A soluble polyimide (PI) is attempted to be a binder for transition metal oxide cathode in lithium ion batteries. It is synthesized from 2,2-Bis[4-(4-aminophenoxy)phenyl]propane, 4,4′-Oxydianiline and 4,4′-Oxydiphthalic anhydride, and characterized by FT-IR and 1H NMR techniques. To be a binder, the synthesized PI is applied to fabricate the electrodes, showing binding property and electrochemical performance as good as poly(vinylidene fluoride) (PVDF) that is conventional binder widely used in lithium ion batteries. The 2 Ah pouch full cells with PI and PVDF binders are assembled to compare their performances. As a result, the batteries with PI binder display 91.4% capacity retention after 500 cycles, which is almost the same as the cells withPVDF binder. The overcharge safetytests are carried by 2 Ah pouch full cells, indicating that PI cells can pass the test, no fire and no explosion, but the PVDF cells fail the test, catching fire. The result shows that the PI binder can enhance the safety of Li-ion batteries. This study paves a new way to improve the safety performance of lithium ion batteries.

Phosphorus@carbon composites are alternative anode materials for lithium-ion batteries due to their high specific capacity. Serving as a conductive and buffer matrix, the carbon substrate is important to the performance of the composite. Our results exhibit that the electrochemical performances of phosphorus@carbon composites could be significantly enhanced by pore size distributions of the carbon matrix. The initial Coulombic efficiency of phosphorus@YP-50F reaches 80% and the capacity remains stable at 1370 mAh g–1 after 100 cycles at 300 mA g–1. The work may provide a general strategy for designing or selecting the optimal carbon matrix for phosphorus@carbon performance, and pave the way to practical application in lithium-ion batteries.Keywords: High performance; Lithium-ion batteries; Phosphorus@carbon composites; Pore size distributions

•Porous Co3O4 microellipsoids are obtained by a facile method.•The initial discharge capacity of as-prepared Co3O4 is 1314 mAh g−1 at 100 mA g−1.•Excellent rate capabilities are observed for the porous Co3O4 microellipsoids.•Porous Co3O4 microellipsoid shows enhanced cyclic stability.The porous micro-/nanostructured Co3O4 microellipsoids are successfully fabricated through a urea-assisted solvothermal route using polyvinylpyrrolidone (PVP) as the capping reagent followed by thermal treatment in air. The porous characterization has been performed to confirm that porous Co3O4 micro-/nanostructures are composed of numerous primary nanocrystallines. The specific surface area and pore size of the Co3O4 microellipsoids are around ∼24.2 m2 g−1 and 13.5 nm, respectively. The obtained porous Co3O4 microellipsoids demonstrate the high initial discharge capacity of ∼1314 mAh g−1 with a Columbic efficiency of 79.2% at a current density of 50 mA g−1 in the potential range of 0.01–3.0 V. More impressively, a significantly improved reversible capacity of ∼1192 mAh g−1 is retained at 100 mA g−1 after 50 discharge-charge cycles. Excellent rate capabilities (∼920 mAh g−1 at 200 mA g−1 and ∼630 mAh g−1 at 600 mA g−1) are observed for the porous microellipsoid-like structure. It should be noted that the unique porous micro-/nanostructured microellipsoids play an important role in the enhanced electrochemical lithium storage performance. Therefore, the porous micro-/nanostructured Co3O4 microellipsoids should be suitable as an anode material for lithium ion batteries.

•A novel anode material Li2NiFe2O4 was prepared under the air conditions.•Li2NiFe2O4 showed well-defined octahedron crystal morphology.•9 h-annealed Li2NiFe2O4 delivered a capacity of 203 mAh g−1.For the first time, the preparation and characterization of a novel anode material Li2NiFe2O4 are reported in this work. The preparation of Li2NiFe2O4 is conducted under the air conditions by using a subsection calcination method. The influence of annealing periods on the properties of the resultant materials is thoroughly explored. The characteristics of the materials are mainly examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy (EIS). The results of the XRD patterns effectively demonstrate the formation of crystalline Li2NiFe2O4, and the SEM images indicate that particles with octahedron crystal morphology are prepared and the 9 h-annealed sample has the smallest particle size among all the prepared samples. The results of electrochemical measurements reveal that 9 h-calcined sample delivers a high specific capacity of 203 mAh g−1 after 20 cycles at a current density of 100 mA g−1. The successful preparation of Li2NiFe2O4 is believed to be able to trigger the research work concerning the novel group of Li2MFe2O4 materials.

A distinctive structure of carbon materials for Li-ion batteries is proposed for the preparation of red phosphorus-carbon composites. The slit-shaped porous carbon is observed with aggregation of plate-like particles, whose isotherm belongs to the H3 of type IV. The density functional theory (DFT) method reveals the presence of micro-mesopores in the 0.5–5 nm size range. The unique size distribution plays an important role in adsorbing phosphorus and electrochemical performance. The phosphorus-slit-shaped porous carbon composite shows initial capacity of 2588 mAh g−1, reversible capacity of 1359 mAh g−1 at a current density of 100 mA g−1. It shows an excellent coulombic efficiency of ∼99 % after 50 cycles.

With the aim to overcome the high thermal shrinkage of conventional polyolefin separators and improve the electrochemical properties of lithium ion batteries, a nano-composite polymer electrolyte membrane (NCPE) is attempted by introducing highly dispersed nano-TiO2 hybrid doped poly(vinylidene fluoride–hexafluoro propylene) (PVDF–HFP) into a glass fiber nonwoven, which is easily available at low costs. The physical and electrochemical properties of the obtained NCPE are characterized using SEM, thermal shrinkage tests, AC impedance measurements, and charge–discharge and cycling tests. The results show that the NCPE possesses higher porosity and higher thermal dimensional stability temperature than a conventional PP separator. In addition, the electrochemical properties, such as liquid uptake, ionic conductivity and interface compatibility, of the polymer electrolyte membrane and the metallic Li electrode was improved significantly. In particular, the LiCoO2/Li coin cell with NCPE exhibits good C-rate performances of up to 85% at 10C-rate of the capacity at 1C-rate, and capacity retention ratios up to 80% after 1500 cycles at 1C/2C charge–discharge cycling. This study shows that the glass fiber nonwoven, which is easily available at low cost, can be a high performance separator for Li-ion battery applications.

•Graphite/Phosphorus composite anode shows promising performance.•The composite anode presents high reversible capacity of 500 mAh g−1 and good cycleability.•Performance of a composite|LiFePO4 full-cell shows easy SOC evaluation.•This paves a new way for exploring new battery chemistry.Graphite/Phosphorus composite anodes are prepared by mixing graphite and the phosphorus/carbon material, which prepared by heating the mixture of red phosphorus and porous carbon. Their electrochemical performances are evaluated as anodes for Li-ion batteries. A graphite/Phosphorus composite|LiFePO4 full-cell is also attempted. When the phosphorus/carbon content in the composite anode is 28.6 wt.%, the composite anode presents high reversible capacity of 500 mAh g−1 and considerable cycleability comparable to that of graphite anode, showing promising performance.

•Highly monodisperse Co3O4 mesoporous microdisks were obtained via a facile method.•As-prepared Co3O4 have a diameter of around 2 μm with an thickness of 30 nm.•The initial discharge capacity of as-prepared Co3O4 is 1032 mAh g-1 at 100 mA g-1.•Co3O4 mesoporous microdisks shows improved capacity and cyclic stability.The monodisperse Co3O4 mesoporous microdisks have been successfully prepared through a facile solvothermal synthesis method and subsequent heating treatment. The Co3O4 microdisks are polycrystalline, and have an average diameter of around 2 μm with an thickness of 300 nm. The specific surface area of Co3O4 mesoporous microdisks is about 108.9 m2 g−1 with a narrow pore size distribution centered at round 9.68 nm. The as-prepared Co3O4 mesoporous microdisks as anode material in lithium ion batteries exhibit a stable specific discharge–charge capacity of 765 and 749 mAh g−1 after 30 cycles at a current density of 100 mA g−1. The good electrochemical properties could be attributed to the unique mesoporous structure of Co3O4 materials.Highly monodisperse mesoporous microdisk Co3O4 nanostructured electrode exhibit significant enhancement of lithium-ion intercalation capacity, good cyclic stability and rate performance due to its unique mesoporous structure.

•In-situ formation of interface films on LiCoO2 surface by electrolyte additive.•Thickness-tunable interface films is obtained by adding different concentrations of BMP additive.•High-voltage cycling performance (4.5 V) is closely associated with the thickness of the interface film.•0.5% BMP electrolyte additive shows superior high-voltage cycleability.We have previously demonstrated that N,N′-4,4′-diphenylmethane-bismaleimide (BMI) as an electrolyte additive enhances the high-voltage performance of lithium-ion batteries by electrochemically forming an interface film on cathode surface. In order to obtain a comprehensive understanding of the bismaleimide-based additives, 2,2′-Bis[4-(4-maleimidophenoxy) phenyl]propane (BMP), which is more compatible with electrolyte than BMI, is studied as a new electrolyte additive. LiCoO2 is chosen as the typical cathode material. Firstly, the structure of interface films on LiCoO2 surface is studied with different concentrations of BMP additive. The morphology, thickness and chemical composition of the interface film are characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) respectively. The oxidation potential of BMP is measured by linear sweep voltammetry (LSV). Secondly, how the interface films influence the high-voltage cycling performance of LiCoO2/Li batteries is studied. AC impedance measurements (EIS), X-ray diffraction (XRD) and discharge profile analysis are used to further clarify the mechanism. For the first time, we find that thickness-tunable interface films could be generated on LiCoO2 surface by adding different concentrations of BMP additives in electrolyte. Also, the high-voltage cycling performance of the corresponding LiCoO2/Li batteries is closely associated with the thickness of the interface film. Optimized amount of BMP additive (0.5% w/v in our work) presents superior high-voltage cycling performance of the corresponding LiCoO2/Li batteries.

•Burned graphene has a significant effect on the morphology of LiNiO2.•Crystal LiNiO2 could be produced as the burned content of graphene was lower than 2 wt %.•Novel LiNiO2 particles with octahedron structure were prepared with burned graphite.A novel finding, that the “burned” graphene has a significant role in determining the morphology of the resultant LiNiO2 nanoparticles prepared under the air conditions, was reported in this work. Briefly, prior to the calcination-preparation of LiNiO2, a series of graphene with various weight contents (0.5 wt %, 1 wt %, 1.5 wt % and 2 wt %) were added in the starting materials of LiNiO2, and then followed by a subsection calcination method under the air conditions. The obtained samples were thoroughly characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). It was found that when the “burned” content of graphene is below 2 wt %, LiNiO2 particles with an average size ranging from about 100 to 500 nm were demonstrated to have regular crystal structures. Results obtained from the electrochemical measurements effectively indicated that the largest value of initial discharge capacity and the highest cycling stability were exhibited by the 1.5 wt % graphene-burned LiNiO2 cathode material as compared to other graphene-burned samples. Interestingly, when employing graphite other than graphene as the carbon source, LiNiO2 particles with well defined octahedron structure were prepared by the same process, which is beneficial to the development of micro-devices. A novel concept, that burned graphene has a significant role in determining the morphology as well as the electrochemical properties of resulting samples, is presented in this work.

In this work, we report novel composite electrospun membranes for Li-ion batteries. A monodispersed nano-sized TiO2@Li+ single ionic conductor containing a P(AALi-MMA) polymer layer grafted on a nano-sized TiO2 surface was prepared and used as functional fillers in composite membranes. The obtained results show that our material, based on the incorporation of a nano-sized TiO2@Li+ single ionic conductor into a composite electrospun membrane is a new generation battery separator for application in lithium-ion batteries.

•Ni1.5Co1.5O4 microflower is synthesized on a large scale by a simple method.•As-prepared Ni1.5Co1.5O4 is composed of two-dimension ultrathin nanosheets.•Ni1.5Co1.5O4 electrode exhibits specific capacity of 980.8 mAh g−1 after 30 cycles.•Ni1.5Co1.5O4 microflowers show potential application for lithium ion batteries.Uniform three-dimension hierarchical flower-like Ni1.5Co1.5O4 nanostructures were synthesized on a large scale by a simple, low-temperature hydrothermal method without any template, catalyst and surfactant, followed by a calcinating process. The obtained Ni1.5Co1.5O4 products were composed of two-dimension ultrathin nanosheets with random attachment. Nitrogen sorption isotherm shows that this structure possesses a high specific surface area of 118.8 m2 g−1 with an average pore diameter of 16.67 nm. When tested as an anode material, the as-prepared Ni1.5Co1.5O4 nanostructures exhibit an initial discharge capacity of 1461.5 mAh g−1. After 30 cycles at the current density of 100 mA g−1, the discharge capacity still keeps 980.8 mAh g−1. The obtained three-dimension hierarchical flower-like Ni1.5Co1.5O4 nanostructures show a promising anode material for lithium ion batteries.

The cooling rate after annealing treatment was proved to be important for the structure and electrochemical performances of the layered oxide 0.3Li2MnO3 · 0.7LiNi0.5Mn0.5O2 material, which has been synthesized using a sol–gel method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nondestructive nano-computed tomography (nano-CT), and Brunauer-Emmett-Teller (BET) surface area measurement were used to characterize the structure and micromorphology of the material. It was demonstrated that the material quenched by liquid nitrogen (AN-material) showed less defects in structure and larger specific surface area than the material cooled naturally (AF-material). Electrochemical measurement showed that the AN-material exhibited better electrochemical performance as cathode candidate for lithium-ion batteries. The initial discharge capacity and coulombic efficiency reached 277.4 mAh g−1 and 84.1 % for AN-material, while 257.1 mAh g−1 and 78.4 % for AF-material. In addition, the AN-material also exhibited lower charge transfer resistance than AF-material.

To study the effect of Fe and/or Zn doping on the performance of LiMnPO4, LiMn0.9Fe0.1−xZnxPO4/C (x = 0, 0.05, and 0.1) composites were synthesized by a solid-state process. They are all single phase with olivine structure but LiMn0.9(FeZn)0.05PO4/C reveals a different morphology. The Fe-Zn co-doping remarkably enhances the performance of LiMnPO4 due to the presence of Fe and Zn in olivine framework resulting in the decrease of charge transfer resistance and Mn ion dissolution. Compared with LiMn0.9Fe0.1PO4/C and LiMn0.9Zn0.1PO4/C, LiMn0.9(FeZn)0.05PO4/C exhibits much higher discharge capacity and better rate capability. It delivers the capacities of 151.3 mAh g−1 at 0.1 C and 128.4 mAh g−1 at 1 C and retains 96.7 % of the initial capacity after 100 cycles.

High-quality monodisperse multiporous hierarchical micro/nanostructured ZnCo2O4 microspheres have been fabricated by calcinating the Zn1/3Co2/3CO3 precursor prepared by urea-assisted solvothermal method. The as-prepared products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) measurement to study the crystal phase and morphology. When tested as anode material for lithium ion batteries, the multiporous ZnCo2O4 microspheres exhibit an initial discharge capacity of 1,369 mAh g−1 (3,244.5 F cm−3) and retain stable capacity of 800 mAh g−1 (1,896 F cm−3) after 30 cycles. It should be noted that the good electrochemical performances can be attributed to the porous structure composed of interconnected nanoscale particles, which can promote electrolyte diffusion and reduce volume change during discharge/charge processes. More importantly, this ZnCo2O4 3D hierarchical structures provide a large number of active surface position for Li+ diffusion, which may contribute to the improved electrochemical performance towards lithium storage.

•Feeding sequences is important in synthesis of LMFP through solvothermal.•(010) face orientated LiMFP presents high electrochemical performance.•A synthesis reaction mechanism of feeding sequence is proposed.•The synthesized LiMn0.9Fe0.1PO4 presents the discharge capacity of 150 mAh g−1.Solvothermal approach is used to synthesize LiMn0.9Fe0.1PO4 (LMFP) nanomaterial for Li-ion batteries (LIBs). Experimental parameters such as feeding sequences, reaction time and reaction temperature are discussed and the obtained LMFP are characterized by XRD, SEM and TEM. To understand the formation of LMFP, a reaction mechanism is proposed. The proposed mechanism indicates that the suitable concentration of MLi (M = Fe, Mn) antisite defect can improve the electrochemical performance of the material. The charge–discharge data of obtained LMFP shows that the LiMn0.9Fe0.1PO4 material synthesized at 180 °C for 4 h and then sintering with sucrose at 650 °C for 5 h under argon protection has the highest discharge capacity, which is 149.2 mAh g−1 at 0.1C rate.

•Titania–PMMA organic/inorganic hybrid is synthesized via in situ polymerization.•The hybrid increases the porosity, uptake efficiency of the PVdF–HFP membrane.•The hybrid increases the ionic conductivity of the PVdF–HFP based CPE.•The hybrid enhances the performance of LiCoO2 cycled between 4.4 and 2.75 V.Titania–poly(methyl methacrylate) (PMMA) organic–inorganic hybrid material is synthesized via in situ polymerization. The hybrid material is employed to prepare poly vinylidene fluoride–hexafluoropropylene (PVdF–HFP) composite polymer electrolyte. The effect of the hybrid material is investigated by SEM, TG-DSC, AC impedance and charge/discharge cycling tests. The results demonstrate that the inorganic–organic hybrid material as additive increases the porosity, pore size and electrolyte uptake of the PVdF–HFP composite polymer electrolyte membrane, so that the ionic conductivity of the composite polymer electrolyte membrane is improved. The performance enhancement of the composite polymer electrolyte is confirmed by an electrochemical test using LiCoO2/Li cells in the voltage range of 2.75–4.4 V. This study shows that titania–PMMA hybrid material is a promising additive for PVDF–HFP composite polymer electrolyte for Li-ion batteries.

•MnO2 nanorods demonstrate excellent electrochemical properties.•The excellent properties can be attributed to nanorod structure and CMC binder.•CMC binder facilitates networking process during electrode fabrication.A facile hydrothermal approach is attempted to prepare MnO2 nanorods using potassium permanganate and hydrochloric acid as the reactants. The MnO2 electrode delivers initial specific discharge/charge capacities of 1609.5 and 1206.1 mAh g−1, respectively, with a columbic efficiency of 74.9% at 0.1 C-rate. After 100 cycles, the reversible capacity keeps to be 1404.7 mAh g−1. The excellent electrochemical properties can be attributed to unique structure of MnO2 nanorods, which greatly shortens the diffusion path of Li+ and accommodates the strain induced by drastic volume change during cycling, and application of CMC binder, which results in the extended conformation in electrolyte solution that facilitates networking process of MnO2 nanorods and conductive additives during electrode fabrication.

•Bismaleimide is found as an additive to enhance electrolyte performance.•Performance of LiCoO2/Li cells is improved while charging the cell up to 4.5 V.•The electrolyte stability is improved to be 5.0 V after the addition.•The surface film formation on cathode is crucial during first cycles.N,N′-4,4′-diphenylmethane-bismaleimide (BMI) is attempted to enhance the high-voltage performance for lithium-ion batteries. When 0.1% (m/v) BMI is added into the control electrolyte, the high-voltage cycling performance of LiCoO2/Li cells is improved evidently while charging the cell up to 4.5 V rather than the conventional 4.2 V. Analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that an interface film forms on the cathode surface from BMI in electrolyte. AC impedance spectra and charge/discharge test were tested after incubation of the charged cell at 60 °C. Linear sweep voltammetry (LSV) is used to test the electrochemical stability window of the electrolyte with BMI addition. The results demonstrate that the improvement of high-voltage performance is attributed to the surface film on cathode. In addition, the BMI addition does not cause damage in conventional performance with 4.2 V electrochemical window. The BMI-containing electrolyte provides high-voltage cycling performance with 4.5 V electrochemical window, making LiCoO2 battery a simple and promising system for applications with high energy density.

Anion species are proved to have a significant influence on orientation, agglomeration and defect control of crystal growth for LiMn0.9Fe0.1PO4 nano-particles prepared by solvothermal synthesis. SO42− is helpful for high dispersity, while Cl− benefits accurate molar ratio control of transition metals in LiMn0.9Fe0.1PO4. Various LiMn0.9Fe0.1PO4 particles, being agglomerative spindles or mono-dispersed uniform nano-flakes, can be obtained by just tuning [Cl−]:[SO42−] ratio, and present dramatically different electrochemical performances. Though the as-prepared samples possess similar reversible capacities around 130 mAh g−1 at low C-rate, they show very different rate performances depending on morphology of the particles.

A solvothermal method is applied for synthesizing LiFePO4 nanoparticles using ethylene glycol as solvent. Crystals are obtained with quite different morphologies at solutions of various acidity prepared via changing the primary LiOH/H3PO4 mole ratios. SEM, TEM, and HRTEM are used to analyze the samples. Element distribution in solid LiFePO4 particles, mother solutions and washing solutions are tracked by ICP-OES and pH tests. Morphological test results show that the main exposed faces of samples transform from (100) as a rectangular shape to (010) as a spindle shape with the pH of the mother solutions increasing. Samples with predominant (010) faces are formed at less acidic solvothermal solutions. At the intermediate pH from 3.11 to 3.73, powders like long hexagon nanorods are synthesized with (100) and (010) faces exposed. XRD results show that the long hexagon nanorods have better crystal structures when synthesized at LiOH/H3PO4 = 2.7–3.0. Impurities like Fe3O4, Li3PO4, etc. are detected in the spindle shape LiFePO4 powders. The amount of impurities is related to the synthesis process and increases with the pH of solvothermal solution increasing. High temperature treatment is useful for impurities transforming to LiFePO4 and thus reduces the impurities. The long hexagon nanorods show better electrochemical performances: 169.9 mA h g−1 at 0.1 C, and 129.8 mA h g−1 at 10 C.

•FeF2–carbon core–shell nanorods are prepared by a one-step thermal reaction.•Ferrocene is used as both iron and carbon precursors.•The nanorods have an average length of 1 μm, and diameters ranging from 100 nm to 1 μm.•The carbon shell is well graphitized with the thickness of 10–20 nm.•The core–shell composite exhibits good cycling performance.Core–shell nanorod with FeF2 as core and graphitized carbon as shell was prepared by a one-pot thermal reaction using a mixture of ferrocene and polyvinylidene fluoride as precursor. The core–shell composite had an average length of about 1 μm and diameter ranging from 100 nm to 1 μm. The shell thickness was about 10–20 nm. Its electrochemical properties were studied in the potential range between 1.3 and 4.2 V at a current density of 30 mA g−1 at room temperature. The core–shell composite exhibited an initial discharge capacity of 345 mA h g−1. A reversible capacity of 217 mA h g−1 was maintained over 50 cycles with coulombic efficiency of 96% per cycle.

Classical molecular dynamics was used to investigate the equilibrium state of the surface region of as-grown La2O3. It is currently thought that bulk and epitaxial thin film La2O3 surfaces exhibit amorphous structures in the as-prepared state that yield bulk crystal states upon postdeposition annealing. The focus of the study is to determine if the as-prepared surface region of La2O3 is purely amorphous as indicated from prior experimental results. Using simulation cells sufficiently large to accommodate the formation of defects, phase segregation, compositional migration, and site defects, our results show that crystalline phases are evident from simulated X-ray diffraction patterns. Although the phase of these crystallites is unresolved, we suggest that combinations of distorted hexagonal, cubic, and nonstoichiometric phases are formed in the as-prepared state prior to annealing. These crystallites likely serve as nucleation site for long-range ordered crystal growth upon annealing.

Metal oxide additives are added into LiFePO4 electrodes attempting to improve cell power performances. Electrochemical performances are tested with 5 wt% different sizes of neutral alumina, nano Al2O3, and nano MgO individually comparing with those with 5 wt% more active LiFePO4 and acetylene black. The polarization between charge and discharge plateaus is reduced not only by adding more conductive acetylene black, but also by adding all these insulated metal oxide additives. Adding natural alumina and nano MgO can significantly increase rate capacities. This might be because of their “lithium ion saver” effect.

Nano-sized ceramic fillers provide a promising approach to enhancing polymer electrolytes in terms of the interfacial chemistry, ionic conductivity, and C-rate performance of Li-ion cells, if their dispersibility and compatibility in a polymer matrix can be well managed. In this work, a nano-crystalline TiO2–PMMA hybrid is prepared by in situ crystallization, and its structure and properties are characterized by XRD, FTIR, TG and HRTEM. The enhancements provided by the nano-crystalline TiO2–PMMA hybrid as an additive in a PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) based composite polymer electrolyte, including in the pore distribution, electrolyte uptake, ionic conductivity, and electrochemical properties, are confirmed by SEM, linear sweep voltammetry (LSV), charge–discharge cycle testing and AC impedance measurements. The results obtained in this work show that, after the process of annealing, the nano-crystalline TiO2–PMMA hybrid can retain a good dispersibility in PVDF-HFP. Moreover, the nanohybrid doped PVDF-HFP CPE exhibits improved pore distribution, electrolyte uptake and ionic conductivity. Even more importantly, LiCoO2/Li cells with doped CPE exhibit good C-rate performances, which is confirmed by AC impedance results, which show a remarkable enhancement in the interfacial compatibility between the doped CPE and the electrode.

A metal-free battery is of great practical significance in terms of high energy density, low cost, high safety, eco-friendly and sustainability. Here a metal-free cathode, using graphene-coated polyethylene terephthalate (G-PET) film (Commercial-Off-The-Shelf) as current collector and sulfurized polyacrylonitrile (SPAN) as active material, is aiming at low cost and high energy density battery. 110 mAh prototype lithium sulfur cells are assembled using SPAN/G-PET cathode, showing energy density of 452 Wh kg−1 excluding the weight of package and capacity retention of 96.8% after 30 cycles at 100% depth of discharge. The self-discharge characteristics of prototype cells are tested. After 30 days of storage at room temperature, the discharge capacity has decreased less than 1%, indicative of low self-discharge of the SPAN-based Li/S batteries. This paper shows that G-PET can be a potential promising current collector for lithium ion batteries.Highlights► A metal free cathode of sulfurized polyacrylonitrile is attempted. ► Using graphene coated polyethylene terephthalate film as current collector. ► 110 mAh prototype lithium sulfur cells are assembled with energy density of 452 Wh kg−1. ► The capacity retention is 96.8% after 30 cycles at 100% depth of discharge. ► The self-discharge is less than 1% after 30 days of storage at room temperature.

•A glycol based solvothermal process is attempted to prepare nano LiFePO4 cathode materials.•The sample delivers capacity retention of 100% after 100 cycles at 100% depth of discharge.•The sample presents an initial columbic efficiency of 98.9% and 100% during cycling afterward.•The capacity of about 163 mAh g−1 at 0.1 C-rate, 157.8 mAh g−1 at 1 C-rate, and 145.9 mAh g−1 at 5 C-rate.A glycol based solvothermal process combined with carbon coating is attempted to prepare nano particle LiFePO4 cathode materials for Li-ion batteries. Different concentration of starting materials, process time, pH values and process temperature are tried. Samples are characterized by XRD and SEM analysis. A carbon coating process with sucrose is used to make LiFePO4/C composites. The optimized sample delivers capacity retention of 100% after 100 cycles at 100% depth of discharge with initial columbic efficiency of 98.9%, cycling capacity of about 163 mAh g−1 at 0.1 C-rate, 159 mAh g−1 at 0.5 C-rate, 157.8 mAh g−1 at 1 C-rate, and 145.9 mAh g−1 at 5 C-rate, under the electrode formula of 80% LiFePO4/C composites, 10% carbon black and 10% binder. This study shows that proposed process can be a potential promising way to prepare high performance LiFePO4 cathode materials for lithium ion batteries.

The presented contribution aims at investigating the role of nano-TiO2 dispersibility in affecting the performance of PVDF-HFP based composite polymer electrolytes (CPEs) for Li-ion cells. Four types of polymer electrolytes containing pristine PVDF-HFP gel polymer electrolyte (GPE), PVDF-HFP/nano-TiO2 CPE, PVDF-HFP/nano-TiO2-PMMA CPE and PVDF-HFP/high-dispersed nano-TiO2-PMMA CPE membranes are obtained by phase inversion. The effect of nano-TiO2 dispersibility on performances of PVDF-HFP based CPEs in terms of ionic conductivity, C-rate and cycling performance is investigated. The results demonstrate that the dispersibility of nano-TiO2 is a key factor to affect the performance of PVDF-HFP based CPEs, and the improvement of the dispersibility of nano-TiO2 can remarkably enhance the electrochemical performances of cells assembled with the corresponding CPEs.

Interfacial compatibility of composite polymer electrolyte and electrode is the key factor to affect the performance of polymer Li-ion batteries. In this work, liquid electrolyte, pristine PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) gel polymer electrolyte (GPE) and nano-TiO2-poly(methyl methacrylate) (PMMA) hybrid doped PVDF-HFP composite polymer electrolyte (CPE) are used to investigate the interfacial compatibility between electrolyte and electrode on performance of LiCoO2/Li cells. The electrochemical performances of cells are studied by charge/discharge tests and electrochemical impedance. The interfacial compatibility coefficient (λ) that related to the interface of electrolyte and electrode is evaluated in terms of the fitting (i = e, sf, b and ct) with equivalent circuit and diffusion resistance (Rdiff). The results confirm that the C-rare performance of cells with GPE is more significantly associated with the interfacial compatibility than the ionic conductivity of GPE.

A facile synthesis of nano-LiMn0.9Fe0.1PO4 particles is attempted by a solvothermal process with ethylene glycol (EG) as solvent. The particle morphology, including plate-like and spindle-like, can be reasonably tuned by anions and feeding sequences of starting materials. FeCl2 and FeSO4 are tried to be starting material of Fe source, respectively. MnCl2, LiOH and H3PO4 are used to be starting materials of Mn, Li and P sources, respectively. P + M + L sequence (that is, LiOH solution is dropwise introduced into the mixture of H3PO4 and transition metal salts) and P + L + M sequence (that is, Mn2+ and Fe2+ mixture was slowly added into the mixture of H3PO4 and LiOH) are investigated to tune the particle morphology. The introduction of SO42− leads to a more uniform morphology of the as-prepared particles compared with those by Cl−1, and P + M + L sequence leads to the particles in smaller size and less agglomeration compared with those by P + L + M sequence. The nano-LiMn0.9Fe0.1PO4 with spindle-like morphology by P + M + L sequence and starting material of FeSO4 exhibits a good reversible discharge capacity of 129.7 mAh g−1 at 0.1C.

Sulfur chain grafted poly(pyridinopyridine) (SPPY) presents an over five-electron process redox reaction, a high reversible capacity of up to 1750 mAh g−1-SPPY and excellent cycling stability. Combined with its facile and eco-efficient synthesis, SPPY is a potential green material for ultra-high capacity of reversible lithium storage and opens a new widow to seek ultra-high capacity materials for lithium ion batteries.

We report the crystal orientation tuning of LiFePO4 nanoplates for high rate lithium battery cathode materials. Olivine LiFePO4 nanoplates can be easily prepared by glycol-based solvothermal process, and the largest crystallographic facet of the LiFePO4 nanoplates, as well as so-caused electrochemical performances, can be tuned by the mixing procedure of starting materials. LiFePO4 nanoplates with crystal orientation along the ac facet and bc facet present similar reversible capacities of around 160 mAh g–1 at 0.1, 0.5, and 1 C-rates but quite different ones at high C-rates. The former delivers 156 mAh g–1 and 148 mAh g–1 at 5 C-rate and 10 C-rate, respectively, while the latter delivers 132 mAh g–1 and only 28 mAh g–1 at 5 C-rate and 10 C-rate, respectively, demonstrating that the crystal orientation plays important role for the performance of LiFePO4 nanoplates. This paves a facile way to prepare high performance LiFePO4 nanoplate cathode material for lithium ion batteries.

Local current density is an important parameter in battery modeling, which affects the performance of lithium-ion batteries. In this study, we take LiFePO4 cathode material as an example. A simplified mathematical model has been developed to study the internal mechanism of the electrode. According to the results of the model, the local current density distribution has a regular change at different time in the discharge process. The parameter “critical thickness” as an optimized variable has been presented for battery design. By qualitative analysis to estimate the critical thickness under different condition, we can optimize the design parameter of a battery according to the practical demand.

Overcharge performance of LiFePO4 cells is investigated through adding 2, 5-ditertbutyl 1, 4-dimethoxybenzene (DDB) as redox shuttle into electrolyte (RS electrolyte) at different charge rate. RS electrolytes with DDB works well as overcharge protection at low charge rate of less than 0.1 C. Novel charge/discharge characteristics are observed when charge rate increases in the cell with RS electrolyte. Especially, larger discharge capacities are obtained at the same discharge rate after charge rate gets higher than 0.1 C rate. Discharge capacity is larger in the cell with RS electrolyte than that in the cell without RS electrolyte at the same charge and discharge rate. At the same charge rate, cells with RS electrolyte have better cycling performances and larger discharge capacity than that with conventional electrolyte. These indicate that DDB accumulates in cathode with cycling and influences electrode–electrolyte interface reactions.

To understand more about the sulfur composite prepared by sulfurized polyacrylonitrile at 300 °C, electrochemical impedance spectroscopy (EIS) is employed to investigate the electrochemical properties of the sulfur composite cathode during discharge process. The impact of discharge depth on the performance of sulfur composite materials is investigated. The electrolyte solution resistance, the charge transfer resistance and the interface impedance are evaluated from the EIS analysis. The charge transfer resistance and the interface impedance increase during delithiation and decrease during lithiation, while the concentration of Li+ in the composite decreases and increases, respectively. Meanwhile the electrolyte solution resistance is likely to keep stable. The interface resistance and charge transfer resistance of the sulfur composite cathode decrease rapidly after initial lithiation, while Li+ diffusion coefficient and exchange current density increase rapidly. After the initial lithiation, they are likely to keep stable. This study reveals more characteristics of the sulfur composite, which is considered to be a promising candidate for large capacity cathode material.Highlights► The impact of initial lithiation depth on the performance of sulfur composite materials is crucial. ► This research reveals more characteristics of the sulfur composite, which helps to understand more about the sulfur composite prepared by sulfurized polyacrylonitrile at 300 °C. ► The sulfur composite material needs full lithiation at the initial cycle for activation to release its electrochemical property.

AlF3-coating is attempted to improve the performance of LiNi0.5Mn1.5O4 cathode materials for Li-ion batteries. The prepared powders are characterized by scanning electron microscope, powder X-ray diffraction, charge/discharge, and impedance. The coated LiNi0.5Mn1.5O4 samples show higher discharge capacity, better rate capability, and higher capacity retention than the uncoated samples. Among the coated samples, 1.0 mol% AlF3-coated sample shows highest capacity after charge–discharged at 30 mA/g for 3 cycles, but 4.0 mol% coated sample exhibits the highest capacity and cycling stability when cycled at high rate of 150 and 300 mA/g. The 40th cycle discharge capacity at 300 mA/g current still remains 114.8 mAh/g for 4.0 mol% AlF3-coated LiNi0.5Mn1.5O4, while only 84.3 mAh/g for the uncoated sample.

A study is attempted on how the dispersion of solid ingredients in solvent affects the electrochemical performance of LiFePO4 composite electrode. The slurries comprising LiFePO4 powder, carbon black and polymeric binder in solvent NMP (N-methyl-2-pyrrolidone) are prepared by two different processes, and results in different dispersion qualities. With better dispersion, the surfactant (Triton-100) is added into slurry as dispersing agent, whereas no dispersing agent in the other sample. The former process leads to more uniform dispersion of solid ingredients as compared to the latter. In the composite electrode prepared from the former process, the LiFePO4 and carbon black particles are homogeneously distributed without obviously reunion. Indebted to this favourable feature, this electrode exhibits a better high C-rate electrochemical performance for cycling and capacity than those without the surfactant.

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated based on different charge/discharge manner. The sulfur composites showed novel electrochemical characteristics as well as the high specific capacity and the good cycleability. The investigation showed that the deep discharge down to less than 1.0 V benefited the performance of the sulfur composite cathode, and the overcharge up to 4.0 V deteriorated its performance. The compaction of the sulfur composite electrode was also investigated. The electrochemical performance of the sulfur composite electrodes was tested at the compaction strength from 0 to 24 MPa, showing that the sulfur composites electrode presented the best electrochemical characteristics at the certain compaction strength of 8 MPa. Its performance seriously deteriorated at the compaction strength of 24 MPa. The study reveals that the appropriate compaction strength benefits the electrochemical performance of the sulfur composite electrode.

SrF2-coated LiNi1/3Co1/3Mn1/3O2 cathode materials with improved cycling performance over 2.5–4.6 V were investigated. The structural and electrochemical properties of the materials were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), charge–discharge tests and electrochemical impedance spectra (EIS). The results showed that the crystalline SrF2 with about 10–50 nm particle size is uniformly coated on the surface of LiNi1/3Co1/3Mn1/3O2 particles. As the coating amount increased from 0.0 to 2.0 mol%, the initial capacity and rate capability of the coated LiNi1/3Co1/3Mn1/3O2 decreased slightly owing to the increase of the charge-transfer resistance; however, the cycling stability was improved by suppressing the increase of the resistance during cycling. 4.0 mol% SrF2-coated LiNi1/3Co1/3Mn1/3O2 showed remarkable decrease of the initial capacity. 2.0 mol% coated sample exhibited the best electrochemical performance. It presented an initial discharge capacity of 165.7 mAh g−1, and a capacity retention of 86.9% after 50 cycles at 4.6 V cut-off cycling.

The expansion and shrinkage characteristics of sulfur composite cathode electrode in rechargeable lithium batteries have been investigated. It was found that the sulfur composites electrodes expanded when discharging and shrank when charging again. The thickness change of the electrode was measured to be about 22%. The thickness of lithium metal anodes was also changed when lithium deposition and dissolution, while the sulfur composites electrodes expanded and shrank conversely. The investigation showed that the thickness changes of lithium anode and sulfur composite cathode could be compensated with each other to keep the total thickness of the cell not to change so much.

ZrO2-coated LiNi1/3Co1/3Mn1/3O2 materials were prepared by hydroxide precipitation. The structure and electrochemical properties of the ZrO2-coated LiNi1/3Co1/3Mn1/3O2 were investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests, indicating that the lattice structure of LiNi1/3Co1/3Mn1/3O2 were unchanged after the coating but the cycling stability was improved. As the coating amount increased from 0.0 to 0.5 mol.%, the initial capacity of the coated LiNi1/3Co1/3Mn1/3O2 decreased slightly; however, the cycling stability increased remarkably over the cut-off voltages of 2.5~4.3 V and the capacity retention reached 99.5% after 30 cycles at the coating amount of 0.5 mol.%. ZrO2 coating also improved the cycling stability of LiNi1/3Co1/3Mn1/3O2 over wider cut-off voltage of 2.5~4.6 V.

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated. The sulfur composites showed novel electrochemical characteristics as well as high specific capacity and good cycleability. The sulfur composite presented the average discharge voltage of 1.9 V, which was just the half of conventional LiCoO2 cathode materials, indicating that the double cells in series presented the same working voltage as conventional LiCoO2 cells and meaning that the sulfur composite cells will have good interchangeability with conventional LiCoO2 cells. The overcharge test showed that the sulfur composite cell cannot be charged over 5.0 V, indicating that the sulfur composite cell presented the intrinsic safety for overcharge. Overcharge can cause serious problems for the conventional Li ion cells. The overcharge test also showed that the sulfur composite cell was destroyed when the cell was charged over 4.0 V, resulting in that the cell cannot normally be discharged again. It is found, however, that the sulfur composite cell can be discharged again at very low current density of a 0.002-C rate after the cell was overcharged. Being much safer than lithium metal anode, the graphite anode was used to fabricate sulfur composite/graphite lithium ion cells with a prelithiated sulfur composite cathode, which was produced by electrochemical lithiation. The charge/discharge and cycling characteristics of the sulfur composite/graphite cell was investigated. The result showed that the sulfur composite/graphite cells can be normally cycled and showed the different voltages from that of the cell with the lithium metal anode. This paves the effective way to fabricate safer sulfur composite/graphite lithium ion cells.

Preparation of LiCoO2 cathode materials from spent lithium–ion batteries are presented. It started with the reclaim/recycle of metal values from spent lithium–ion batteries, which involves the separation of electrode materials by ultrasonic treatment, acid dissolution, precipitation of cobalt and lithium, followed by the preparation of LiCoO2 cathode materials. Co (99.4%) and Li (94.5%) were recovered from spent lithium–ion batteries. The LiCoO2 cathode materials prepared from the reclaimed cobalt and lithium compounds showed good elecrtochemical performance. The reclaiming of cobalt and lithium has a promising outlook for the recycling of cobalt and lithium from spent Li–ion batteries, thus reducing the cost of Li–ion batteries.

A process was attempted to improve the performance of natural graphite for lithium ion batteries (LIB). The natural graphite was treated in a concentrated sulfuric acid solution at high temperature, followed by the coating of resorcinol–formaldehyde resin using in situ polymerization and heat-treatment over 800 °C. SEM, XRD, XPS and Raman spectroscopy were employed to investigate the samples. It was found that the sharp edges as well as other active sites “were repaired” and the thin pyrolytic carbon film coated on the surface of graphite led to the decrease of BET surface areas of coated graphite and depressed decomposition of electrolyte and co-intercalation of solvated ions, which led to an improved electrochemical performance of modified graphite. In fact, the modified natural graphite reached 90.3% of the initial coulombic efficiency, more than 350 mAh g−1 of the reversible capacity and 96.4% of the charge capacity retention reached after 70 cycles. The results show that the proposed process is a promising and practicable way to improve natural graphite for LIB.The natural graphite was treated in a concentrated sulfuric acid solution at high temperature, followed by the coating of resorcinol–formaldehyde resin using in situ polymerization and heat-treatment over 800 °C. The modified natural graphite presented an improved electrochemical performance.

The charge/discharge characteristics of the sulfur composite cathodes were investigated at different temperatures and different current densities. The composite presented the discharge capacities of 854 and 632 mAh g−1 at 60 and −20 °C, respectively, while it had the discharge capacities of 792 mAh g−1 at 25 °C. The composite presented the discharge capacities of 792 and 604 mAh g−1 at 55.6 and 667 mA g−1, respectively, at room temperature. The results showed that the sulfur composite cathodes presented good charge/discharge characteristics between 60 and −20 °C and at a high c-rate up to 667 mA g−1.

A novel composite anode material consisted of electrodeposited Cu–Sn alloy dispersing in a conductive micro-porous carbon membrane coated on Cu current collector was investigated. The composite material was prepared by template-like-directed electrodepositing Cu–Sn alloy process and then annealing. The template-like microporous membrane electrode was obtained as follows: (1) casting a polyacrylonitrile (PAN) solution on a copper foil, (2) then immersing the copper foil into deionized water for phase inversion, and (3) drying the membrane electrode. This method provided the composite material with high decentralization of Cu–Sn alloy and supporting medium function of conductive carbon membrane deriving from pyrolysis of PAN. SEM, XRD, and EDS analysis confirmed this structure. The characteristic structure was beneficial to inhibit the aggregation among Cu–Sn microparticles, to relax the volume expansion during cycling, and to improve the cycle ability of electrode. The reversible charge/discharge capacity of the composite material remained more than 426.6 and 445.1 mAh g−1, respectively, after 70 cycles, while that of the electrode prepared by electrodepositing Cu–Sn on a bare Cu foil decreased seriously to only 11.3 mAh g−1. These results show that the novel preparing anode process for LIB is a promising method and can achieve composite materials with larger specific capacity and long cycle life.

Phase inversion technique was used to prepare poly(acrylonitrile-methyl methacrylate) [P(AN-MMA)]-based microporous gel electrolyte with addition of SiO2 via in-situ composition for Li-ion batteries. The P(AN-MMA) was synthesized by emulsion polymerization and was dissolved into N,N-dimethylformamide (DMF) to form a uniform solution, while tetraethyl orthosilicate (TEOS) was added into the solution and was hydrolyzed by catalysis of alkali ammonia solution to form SiO2. Then the solution was cast onto a glass plate using a doctor blade and exposed to humidified atmosphere produced by ultrasonic humidifier, followed by washing, rinsing, and drying, successively. The gel electrolyte was obtained by putting the P(AN-MMA) microporous membrane in a liquid electrolyte. The gelled microporous membrane sucked with 755 wt% of liquid electrolyte vs the dried membrane. It had a porosity of 70%, about 1∼5 μm of pores, and presented an ionic conductivity of 0.94 × 10−3 S/cm at room temperature. Electrochemical stability window of the porous gel polymer electrolyte was determined by running a linear sweep voltammetry. The decomposition voltage of the polymer electrolyte exceeds 4.5 V vs Li. The coin test cell with the microporous gel electrolyte showed a good cycling performance. The discharge capacity retention was above 87% at 0.1 C for 45 cycles.

The star macromolecules (SM) were synthesized from phloroglucinol, phosphorus oxychloride, and poly(ethylene glycol methyl ether) with different molecular weight. Structures of the products were characterized by Fourier transform infrared and 1H-nuclear magnetic resonance. Solid polymer electrolyte films were prepared by mixing the products with poly(ethylene oxide) (PEO) and LiClO4. The polymer blends of PEO and SM have been characterized by differential scanning calorimetry and thermogravimetry, and the polymer electrolytes have been characterized by alternating current impedance. All the SM products could improve the conductivities of the polymer electrolyte obviously at a temperature range from 20 °C to 80 °C.

A novel composite anode material consisted of electrodeposited Sn dispersing in a conductive micro-porous carbon membrane, which was directly coated on Cu current collector, was investigated. The composite material was prepared by: (1) casting a polyacrylonitrile (PAN)/dimethylformamide (DMF) solution that contained silica particles on a copper foil, (2) removing the solvent by evaporation, (3) dissolving the silica particles by immersing the copper foil into an alkaline solution, (4) drying the copper foil coated by micro-porous membrane, (5) electrodepositing Sn onto the copper foil through the micro-pores in the micro-porous membrane, and (6) annealing as-obtained composite material. This method provided the composite material with high decentralization of Sn and supporting medium purpose of conductive carbon membrane deriving from pyrolysis of PAN. SEM, XRD and EDS analysis confirmed this structure. The characteristic structure was beneficial to inhibit the aggregation between Sn micro-particles, to relax the volume expansion during cycling, and to improve the cycleability of electrode. Galvanostatic tests indicated the discharge capacity of the composite material remained over 550 mAh g−1 and 71.4% of charge retention after 30 cycles, while that of the electrode prepared by electrodepositing Sn on a bare Cu foil decreased seriously to 82.5 mAh g−1 and 13%. These results show that the composite material is a promising anode material with larger specific capacity and long cycle life for lithium ion batteries.

A process of modification of natural graphite materials as anode for lithium ion batteries was attempted. The process started with the treatment of natural graphite with concentrated hydrochloric acid and concentrated sulfuric acid in a thermal autoclave, followed by the in situ polymerization of resorcinol–formaldehyde resin to coat the graphite, then heat-treatment. SEM, XRD, Raman and electrochemical charge–discharge analysis showed that the surface defects and impurities on natural graphite were eliminated by purification of the concentrated acids, and carbon-film encapsulation modified the surface structure of the graphite and reduced its BET surface area. The as-obtained natural graphite sample presented an initial charge–discharge coulombic efficiency of 88.4% and a reversible capacity of 355.8 mAh g−1. The proposed process paves a way to prepare a promising anode material with excellent performance with low cost of natural graphite for rechargeable lithium ion batteries.

NH4HCO3, (NH4)2SO4 and (NH4)2C2O4 were used as pore-formers to prepare MEAs of proton exchange membrane fuel cells (PEMFC). The addition of NH4HCO3 presented the best performance of the MEA. ESEM analysis showed that the addition of NH4HCO3 made the dispersion of the catalyst on the surface of the MEA more uniform, and made the surface more porous, leading to low resistance for gas diffusion. The addition of NH4HCO3 reduced the Pt loading in MEA from 0.4 to 0.2mgcm-2 and kept the performance of MEA to be unchanged, leading to the cost reduction of the PEMFC. The ratio of the Pt loading and NH4HCO3 was optimized to be the proper value of 1:2, which presented the maximum power density of 0.332Wcm-2. Addition of NH4HCO3 is an effective way to improve the performance of MEAs, reducing the cost of PEMFC.

Spherical nano Sn encapsulated pyrolytic polyacrylonitrile composite anode material was prepared for Li–ion batteries. The preparation started with the dissolution of SnCl2 and polyacrylonitrile (PAN) in dimethylformamide (DMF) solution, followed by the reduction of Sn using KBH4. The composite was obtained by the pyrolysis of the Sn/PAN mixture at 300 °C. The TEM analysis showed that about 20–40 nm spherical Sn particles were embedded by the pyrolytic PAN. The as-prepared composite presented good cycleability for lithium storage with high initial Coulombic efficiency of 71%.

The electrochemical behavior of the sulfur composite cathode material for rechargeable lithium batteries and the characteristic of the polyacrylonitrile precursor were investigated. The samples of different polyacrylonitrile precursors were characterized by thermogravimetric analysis, nuclear magnetic response, Fourier transform infrared spectrometer, and differential scanning calorimetry. The electrochemical performance of the sulfur composite cathode material made from the polyacrylonitrile precursor was also tested. The analysis showed that the molecular weight distribution and the impurity of the polyacrylonitrile precursor affected the electrochemical performance of the sulfur composite cathode material made from the precursor. The polyacrylonitrile precursor with the narrower distribution of the molecular weight and the higher structural purity of the polyacrylonitrile precursor led the better electrochemical performance of the sulfur composite cathode material made from the precursor.

A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution, forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based composite anode materials for Li-ion batteries.

Nanocrystalline FeS2 cathode material of lithium cell was synthesized from cheap materials of FeSO4, Na2S2O3, and sulfur by a hydrothermal process. The scanning electron microscopy analysis showed the obtained material was nano-sized, about 500 nm. The X-ray powder diffraction analysis showed that the synthetic FeS2 material had two phases of the crystalline structure, pyrite and marcasite. The phase of marcasite seems to have no negative effect on the electrochemical performance of the material. The synthetic FeS2 showed a significant improvement of electrochemical performance for Li/FeS2 cells.

A novel process was proposed for synthesis of spinel LiMn2O4 with spherical particles from cheap materials of MnSO4, NaOH, oxalic acid, citric acid and Li2CO3. Its successful preparation started with a carefully controlled crystallization of Mn3O4, leading to the spherical shape of its particles and a high tap density. The mixture of Mn3O4 and Li2CO3 was sintered to produce LiMn2O4 with spherical particle size retention. The spherical particles of spinel LiMn2O4 were of excellent fluidity and dispersivity, and had tap density as high as 1.9 g cm−3 and the initial discharge capacity reaching 116 mAh g−1. Its 20th cycle capacity kept to be 111 mAh g−1.

Nano SiO2–P(VDF-HFP) composite porous membranes were prepared as the matrix of porous polymer electrolytes through in situ composite method based on hydrolysis of tetraethoxysilane and phase inversion. SEM, TEM, DSC and AC impedance analysis were carried out. It is found that the in situ prepared nano silica was homogeneously dispersed in the polymeric matrix, enhanced conductivity and electrochemical stability of porous polymer electrolytes, and improved the stability of the electrolytes against lithium metal electrodes. The in situ composite method was found to be much better than the direct composite method in lowering the interfacial resistance between electrolyte and lithium metal electrode. Moreover, cycle test of lithium batteries using lithium metal as anode and sulfur composite material as cathode showed that the electrolyte based on in situ composite of silica presented stable charge–discharge behavior and little capacity loss of battery.

Classical molecular dynamics is used to investigate the equilibrium state of the surface region and interface of heteroepitaxial La2O3 thin films. Due to the lattice mismatch, heteroepitaxial thin films are subject to very large stress. For this reason the behavior of La2O3 thin films at SiO2 interface becomes an important concern. Our result indicates that La2O3 can uniformly wet SiO2 surface. The properties of the simulated films are analyzed and the lack of any discernible crystalline phase in epitaxial La2O3 on SiO2 indicates that the lattice mismatch between SiO2 and La2O3 is sufficiently large to prevent the formation of even short-range orders in La2O3 film.The lack of discernible crystalline phase in epitaxial La2O3 on SiO2 indicates that the lattice mismatch between SiO2 and La2O3 is sufficiently large to prevent the formation of even short-range orders in the La2O3 film.Download full-size image

Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is important for the battery energy density. In this study, we grafted organic/inorganic hybrid crosslinked networks on the separators, simply by grafting polymerization and condensation reaction. The considerable silicon-oxygen crosslinked heat-resistance networks are responsible for the reduced thermal shrinkage. The strong chemical bonds between networks and separators promise enough mechanical support even at high temperature. The shrinkage at 150°C for 30 min in the mechanical direction was 38.6% and 4.6% for the pristine and present graft-modified separators, respectively. Meanwhile, the grafting organic-inorganic hybrid crosslink networks mainly occupied part of void in the internal pores of the separators, so the thicknesses of the graft-modified separators were similar with the pristine one. The half cells prepared with the modified separators exhibited almost identical electrochemical properties to those with the commercial separators, thus proving that, in order to enhance the thermal stability of lithium ion battery, this kind of grafting-modified separators may be a better alternative to conventional silica nanoparticle layers-coated polyolefin separators.Organic/inorganic hybrid crosslinked networks on the separators have been grafted, simply by grafting polymerization and condensation reaction. The modified separators exhibit good thermal stability without the increasement of thickness.Download full-size image

Boron-doped Ketjenblack is attempted as cathode catalyst for non-aqueous rechargeable Li–O2 batteries. The boron-doped Ketjenblack delivers an extremely high discharge capacity of 7193 mAh/g at a current density of 0.1 mA/cm2, and the capacity is about 2.3 times as that of the pristine KB. When the batteries are cycled with different restricted capacity, the boron-doped Ketjenblack based cathodes exhibits higher discharge platform and longer cycle life than Ketjenblack based cathodes. Additionally, the boron-doped Ketjenblack also shows a superior electrocatalytic activity for oxygen reduction in 0.1 mol/L KOH aqueous solution. The improvement in catalytic activity results from the defects and activation sites introduced by boron doping.Download high-res image (134KB)Download full-size imageThe boron-doped Ketjenblack delivers high discharge capacity of 7193 mAh/g. The capacity is about 2.3 times as that of the pristine Ketjenblack.

With the aim to overcome the high thermal shrinkage of conventional polyolefin separators and improve the electrochemical properties of lithium ion batteries, a nano-composite polymer electrolyte membrane (NCPE) is attempted by introducing highly dispersed nano-TiO2 hybrid doped poly(vinylidene fluoride–hexafluoro propylene) (PVDF–HFP) into a glass fiber nonwoven, which is easily available at low costs. The physical and electrochemical properties of the obtained NCPE are characterized using SEM, thermal shrinkage tests, AC impedance measurements, and charge–discharge and cycling tests. The results show that the NCPE possesses higher porosity and higher thermal dimensional stability temperature than a conventional PP separator. In addition, the electrochemical properties, such as liquid uptake, ionic conductivity and interface compatibility, of the polymer electrolyte membrane and the metallic Li electrode was improved significantly. In particular, the LiCoO2/Li coin cell with NCPE exhibits good C-rate performances of up to 85% at 10C-rate of the capacity at 1C-rate, and capacity retention ratios up to 80% after 1500 cycles at 1C/2C charge–discharge cycling. This study shows that the glass fiber nonwoven, which is easily available at low cost, can be a high performance separator for Li-ion battery applications.

Nano-sized ceramic fillers provide a promising approach to enhancing polymer electrolytes in terms of the interfacial chemistry, ionic conductivity, and C-rate performance of Li-ion cells, if their dispersibility and compatibility in a polymer matrix can be well managed. In this work, a nano-crystalline TiO2–PMMA hybrid is prepared by in situ crystallization, and its structure and properties are characterized by XRD, FTIR, TG and HRTEM. The enhancements provided by the nano-crystalline TiO2–PMMA hybrid as an additive in a PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) based composite polymer electrolyte, including in the pore distribution, electrolyte uptake, ionic conductivity, and electrochemical properties, are confirmed by SEM, linear sweep voltammetry (LSV), charge–discharge cycle testing and AC impedance measurements. The results obtained in this work show that, after the process of annealing, the nano-crystalline TiO2–PMMA hybrid can retain a good dispersibility in PVDF-HFP. Moreover, the nanohybrid doped PVDF-HFP CPE exhibits improved pore distribution, electrolyte uptake and ionic conductivity. Even more importantly, LiCoO2/Li cells with doped CPE exhibit good C-rate performances, which is confirmed by AC impedance results, which show a remarkable enhancement in the interfacial compatibility between the doped CPE and the electrode.