Porous carbon derived from rice hulls has potential for application in phosphorus–carbon composites as high capacity anode materials for lithium-ion and sodium-ion batteries. The native composition of rice husks produces a porous carbon with a unique doped structure, as well as an efficient pore and channel structure, which may facilitate high and stable lithium storage. After cycling for over 100 cycles, the composite delivered a capacity of about 1293 mAh g–1, as well as a coulombic efficiency of nearly 99% at the current density of 130 mA g–1 with a capacity density of 1.43 mAh cm–2. High specific discharge capacities were maintained at different current densities (∼2224, ∼1895, ∼1642, and ∼1187 mAh g–1composite at 130, 260, 520, and 1300 mA g–1, respectively). This study may offer a golden opportunity to change the humble fate of rice hulls, and also pave the way toward successful battery application for phosphorus–carbon composite anode materials.Topics: Batteries; Composites; Distribution function; Electric transport processes and properties; Heat treatment; Physical and chemical processes; Plant-derived food; Porosity; Surface structure;

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

•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.

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.

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.

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.

•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.

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.

•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.

•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.

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.

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

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.