•LiNi0.5Co0.2Mn0.3O2 has been functionally coated with Li2SiO3 via a two-step method.•Li2SiO3 possesses a high Li+-ion conduction and excellent structural stability.•The Li2SiO3-coated sample shows improved electrochemical properties.Layered LiNi0.5Co0.2Mn0.3O2 (NCM523) material has been functionally coated with a uniform and thin layer of Li2SiO3 via a two-step method. Owing to its high lithium ion conduction and excellent structural stability against electrolyte decomposition, Li2SiO3 could greatly improve the Li+ ion diffusion rate and ameliorate the electrochemical capability of the layered oxide materials. Electrochemical tests illustrate that Li2SiO3 used as a Li+-ion conductor greatly improves electrochemical performance of the NCM523 cathode at high current density under high cutoff voltage. Particularly, the Li2SiO3-modified sample delivers an initial capacity of 140.0 mAh g−1 and remains 134.1 mAh g−1 even at a high current density of 10 C after 100 cycles, while the capacity of the pristine decreased sharply to 81.5 mAh g−1. The capacity retention of Li2SiO3-modified NCM523 is 96.1%, while only 55.3% for the bare sample. This result demonstrates an efficient method for the Li2SiO3-modified NCM523 cathode with enhanced electrochemical performance, which has a certain reference for other cathode materials of Li-ion batteries.LiNi0.5Co0.2Mn0.3O2 has been functionally coated with Li2SiO3 via a two-step method. The Li2SiO3-coated sample shows improved electrochemical properties.Download high-res image (338KB)Download full-size image

•LFP-NVPF/C hybrid composite is synthesised by carbothermal reduction method.•The addition of NVPF facilitates the diffusion via continuous Li+ diffusion pathways.•The synergistic effect of carbon coating and NVPF phase improves stability of surface.•The best composite retains 95% of the initial capacity after 500 cycles at 5C.To improve the operating voltage and the rate performance of LiFePO4, the different ratios of the xLiFePO4·(1−x)Na3V2(PO4)2F3/C (LFP-NVPF/C) are synthesised via a carbothermal reduction method. The structure and morphology of the composite are analysed by X-ray diffraction (XRD) and electron microscopy. The as-prepared material is composed of a mixture of two phases: V-doped LFP and Fe-doped NVPF. Electrochemical tests show that the molar ratio of 9:1 is the optimum composition and the LFP-NVPF/C (x = 0.9) composite exhibits excellent performance with an initial discharge capacity of 151.2, 146.5, 120.6 and 100.2 mAh g−1 at 1.0, 2.0, 5.0 and 10 C, respectively, which is higher than that of single phase LFP/C, especially at high rates. According to the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the introduction of NVPF improves charge transfer and Li+ diffusion of LFP/C and provides excellent cycle stability at high rates.

•LMFP·NVPF/C is prepared by mechanical activation assisted carbonthermal reduction.•Nano-hybrid cathode has continual Li+ diffusion pathway with uniform carbon coating.•Nano-hybrid cathode has better rate and cycling performance with 106.4 mAh g−1 at 3 C.The nanostructured 0.9LiMn0.9Fe0.1PO4·0.1Na3V2(PO4)2F3/C composites are successfully synthesized by a facile solvothermal method followed by mechanical activation and subsequent carbonthermal reduction process. Behaviours of bi-phase co-existence and element mutual-substitution have been investigated by XRD, TEM/EDX and FTIR. The result shows that the composites have dual phase boundaries including the semi-coherent phase interface and incoherent phase interface, as well as the advantage of Na3V2(PO4)2F3 acting as ionic conductor. Due to the multifunctional phase and (Mn,Fe)-V mutual doping as well as nano-carbon continual conducting network, enhanced Li+ migration and charge transfer of nano-hybrid is obtained. Compared with pristine one, the 0.9LiMn0.9Fe0.1PO4·0.1Na3V2(PO4)2F3/C composites exhibit high rate capability and cycling ability, showing 125.5, 106.4 mAh g−1 at 1.0 C, 3.0 C at room temperature, respectively, with high capacity retention up to 93.9% after 600th at 2 C.

•NTP with high ionic conductivity is used as coating layer for the first time.•NTP coating layer with crystalized or amorphous is introduced successfully.•Crystalized NTP-coated LNCM exhibits the excellent electrochemical properties.•Low barrier diffusion pathways for Li+ ions through the interface are provided.•Typical sample shows a capacity retention of 85.3% at 3.0–4.6 V after 100 cycles.Well-distributed, nano-sized and amorphous or crystalized NaTi2(PO4)3 (NTP) coating layer with high ionic conductivity is successfully introduced onto the surface of LiNi0.6Co0.2Mn0.2O2 (LNCM) particles by a simple and effective mechanical activation method followed by adjusting the reheating temperature appropriately. The promoting influence of NTP coating on the structure stability, cycle life and high rate capability under elevated cut-off voltage has been investigated in-depth. Particularly for the crystalized NTP-coated LNCM, the main reason for the enhanced electrochemical performance can be attributed to the NTP layer with rhombohedral structure providing convenient and low activation barrier diffusion pathways for Li+ ions to insert/extract the interface of electrode/electrolyte. Besides, the NTP-coated layer with stable structure can effectively inhibit the surface side reaction during the long charge/discharge process under high cut-off voltage, which will reduce the harmful insulative by-products. It's worth mentioning that the cyclic stability of crystalized NTP-coated LNCM between 3.0 and 4.6 V is also improved significantly even under the rigorous test environment.

•Li2SnO3 has been successfully coated on the surface of LiNi0.5Co0.2Mn0.3O2.•Electrochemical performance of host material is improved by Li2SnO3 modification.•A coating layer of Li2SnO3 can reduce polarization of host material.A surface cladding of nano-sized Li2SnO3 powder on Ni-rich layered LiNi0.5Co0.2Mn0.3O2 compounds for lithium ion batteries have been successfully achieved through a two-step synthesis process. The structures and morphologies of as-prepared samples have been analyzed. A cladding layer of Li2SnO3 can be distinguished on the surface of host material and the thickness is about 15 nm with uniform distribution. The optimized Li2SnO3-coated sample displays better rate performance and higher capacity retentions of 94.9% at 10C after 100 cycles than that of the bare one (68.3%) at 3.0–4.5 V. In addition, Li2SnO3 as an effective coating layer can enhance the cycle stability and rate property of electrodes.

•LiMnPO4 was introduced to modify Ni-rich cathode materials.•LiMnPO4 uniformly coated NCA composite has been constructed successfully.•Olivine structured skin restrains the formation of residues on NCA during cycling.•LiMnPO4 improves the structural and thermal stability of NCA@LMP.LiNi0.80Co0.15Al0.05O2 has been widely pursued as an alternative to LiCoO2 cathode materials for lithium ion batteries because of its high capacity and acceptable cycling property. However, that NCA can react with commercialized electrolyte during cycling restrains its wide use. Here, olivine structured LiMnPO4 has been introduced to modify the surface of NCA by a sol-gel method. Characterizations from structure, morphology and composition analysis technologies demonstrate that a LiMnPO4 layer has been uniformly coated on NCA particles. The electrochemical performance and thermo stability of modified samples are characterized by electrochemical tests, XRD and metallic nail penetration tests. The olivine structured skin, which provides structural and thermal stability, is used to encapsulate the high powered core via using the effective coating technique. The modified material displays a high discharge capacity of 211.0 mAh g−1 at 0.2 C and better rate performance and promoted cycling stability than the uncoated control sample. Furthermore, the thermal stability of coated sample in the delithiated state is upgraded to the pristine powders remarkably.

•A novel SiO2-coating on cathode materials method is introduced.•The surface of NCM 811 is coated SiO2 by carbonic acid neutralization method.•SiO2 coating exhibits greatly slowing down dissolution of metal ions effect.•Lithium impurities are suppressed by SiO2 coating demonstrating by XPS results.•Electrochemical and storage property are greatly improved after SiO2 coating.A novel SiO2-coating on cathode materials process is introduced to improve the electrochemical performance and storage property of LiNi0.8Co0.1Mn0.1O2. The continuous and uniform nanoscale layer of SiO2 is successfully coated onto the surface of LiNi0.8Co0.1Mn0.1O2 particles through carbonic acid neutralization method, which is demonstrated by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The nanostructured SiO2 coating film on the surface of particles working as protective layer can effectively weaken the host particles from HF corrosion and delay the increasing amount of the lithium impurities on the surface, improving the cycle performance and storage property of LiNi0.8Co0.1Mn0.1O2 significantly. This can be further demonstrated by the outcome of Cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) tests which show that the SiO2-modified layer can greatly reduce the polarization gap and significantly decrease the charge-transfer resistance during charge/discharge process. The results of charge–discharge tests also demonstrate that the cycle performance even at elevated cut-off voltage and high temperature (60 °C), as well as the rate capability of LiNi0.8Co0.1Mn0.1O2 sample are improved strikingly after SiO2 coating modification.

•Electrochemical performance of LiNi0.5Co0.2Mn0.3O2 is improved by Li2MoO4 modification.•Li2MoO4 modification can make the structure of the bare material stable.•Li2MoO4-inlaid Li[Ni0.5Co0.2Mn0.3]O2 samples show excellent cycling stability under high voltages.•The modification of Li2MoO4-inlaid can reduce polarization and increase the electronic conductivity to some extent.Uniform spherical xLi2MoO4-inlaid LiNi0.5Co0.2Mn0.3O2 materials were successfully prepared through a solid state synthesis. To investigate the material characterization and electrochemical performance after Li2MoO4 modification, X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests were applied. The results of the XRD, Rietveld refinement, SEM and EDS analyses showed that a Mo atom may be incorporated into the crystal lattice of the layer structure. Moreover, the presence of Li2MoO4 on the LiNi0.5Co0.2Mn0.3O2 surface was observed. The thickness of the Li2MoO4 coating layer on the xLi2MoO4-inlaid LiNi0.5Co0.2Mn0.3O2 material (x = 0.02) was approximately 25 nm. Similarly, XPS was performed to determine the effect of Li2MoO4 modification, confirming the presence of Li2MoO4. The xLi2MoO4-inlaid (x = 0.02) LiNi0.5Co0.2Mn0.3O2 materials exhibited a retention capacity 83.5% higher than that of the bare material (40.9%) after 200 cycles at 0.5 C between 3.0 and 4.4 V, and it also exhibited the best electrochemical properties at a cutoff voltage of 4.5 V. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed that the modification of Li2MoO4 plays an important role in improving the electrochemical performance of pristine LiNi0.5Co0.2Mn0.3O2.

A facile solution route was employed for the preparation of an Al doped ZnO (AZO) coating layer, which was composed of many AZO nanoparticles. These nanoparticles have an average particle size of 50 nm and have been successfully decorated on the surface of NCM523. As cathode material for lithium ion batteries, the AZO-decorated NCM523 exhibits superior lithium storage improvements according to good cyclic performance, enhanced rate performance (134.2 mAhg–1 after 200 cycles at 10 C), and high-temperature performance (148.9 mAhg–1 at 10 C at 60 °C). Such significant improvement could be attributed to the structural superiority of the AZO decoration on the surface of NCM523, which would stabilize the surface structure of the bulk, suppress the undesirable side reaction at the interface of the electrodes, and lead to the enhancement of the conductivity. The preparation of AZO-decorated NCM523 provides an effective method for the high-performance lithium ion batteries and has a certain reference for other materials.Keywords: AZO; cathode material; decoration; high-temperature performance; rate performance;

•PPy-coated LiCoO2 particles are prepared by a chemical polymerization method.•The PPy film, like a capsule shell, avoids LiCoO2 corrosion from HF attacking.•The PPy film builds a conductive network and increases the electronic conductivity.•The electrochemical properties of LiCoO2 are enhanced after coating with PPy.A conducting polypyrrole thin film is successfully coated onto the surface of LiCoO2 by a simple chemical polymerization method. The structure and morphology of pristine LiCoO2 and PPy-coated LiCoO2 are investigated by the techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). Energy dispersive X-ray spectroscopy (EDXS), Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA) further demonstrate the existence of PPy. The electrochemical properties of the composites are investigated by galvanostatic charge–discharge test and AC impedance measurements, which show that the conductive PPy film on the surface significantly decrease the charge-transfer resistance of LiCoO2. The PPy-coated LiCoO2 exhibits a good electrochemical performance, showing initial discharge capacity of 182 mAh g−1 and retains 94.3% after 170 cycles. However, the retention of pristine LiCoO2 is only 83.5%. The rate capability results show that the reversible capacity retention (10C/0.2C) of LiCoO2 increases from 52.4% to 80.1% after being coated with PPy. The continuously coated thin PPy film is just like a capsule shell, which can protect the core (LiCoO2) from corrosion causing by the HF attacking and greatly reduce the dissolution of Co into electrolyte.

A series of LiMnPO4 nanoparticles with different morphologies have been successfully synthesized via a solvothermal method. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results show that the morphology, particle size and crystal orientation are controllably synthesized by various precursor composite tailoring with various Li:Mn:P molar ratios. At 3:1:1, a Li+-containing precursor Li3PO4 is obtained while at 2:1:1, only a Mn2+-containing precursor involving Mn5(PO4)2[(PO3)OH]2·4H2O and MnHPO4·2.25H2O is detected. Especially, at 2.5:1:1, the precursor consists predominantly of a Mn2+-containing precursor with a minor amount of Li3PO4. From 2:1:1 to 3:1:1, the particle morphology evolves from sheet to spherical texture accompanied with the particle size reducing. In the presence of urea, highly uniform LiMnPO4 with a hierarchical micro-nanostructure is obtained, which is composed of nanosheets with a thickness of several tens of nanometers. Thus, these unique hierarchical nanoparticles with an open porous structure play an important role in the LiMnPO4 cathode material. At a concentration of 0.16 mol L−1 for urea, the hierarchical LiMnPO4/C sample assembled from nanosheets with the (010) facet exposed shows the best electrochemical performance, delivering higher reversible capacity of 150.4, 142.1, 138.5, 125.5, 118.6 mA h g−1 at 0.1, 0.2, 0.5, 1.0, 2.0C, respectively. Moreover, the composites show long cycle stability at high rate, displaying a capacity retention up to 92.4% with no apparent voltage fading after 600 cycles at 2.0C.

•MnFe2O4/rGO was synthesized by an in situ reduction-coprecipitation method.•MnFe2O4 particles with a size of about 10 nm are uniformly anchored on rGO sheets.•MnFe2O4/rGO exhibits an excellent electrochemical performance.MnFe2O4/reduced graphene oxide nanocomposite (MnFe2O4/rGO) was synthesized by a facile and green strategy, which involves in situ reduction of GO in presence of Fe2+ as well as co-precipitation of Fe3+ and Mn2+ onto the surface of rGO. The composite consists of MnFe2O4 with its primary particles (~10 nm) decorated by rGO sheets, which could prevent the aggregation of the particles and ensure a relatively large specific surface area. It exhibits a specific capacity of 813.4 mA h g−1 at the current density of 0.2 A g−1 and a capacity retention of 80.3% after 100 cycles. Moreover, the proposed synthesis strategy can also be easily extended to prepare other MxFe1−xO4/rGO (M=Ni, Co, Zn, and Mg) composite materials.

•Li2TiO3 and carbon co-coated LiMnPO4 with mixed conductive network is prepared.•Co-coated LiMnPO4 has better rate and cycle performance than the pristine one.•The capacity of 3 wt.% Li2TiO3-coated LiMnPO4 is 117.7 mAh g− 1 at 2 C between 2.5 and 4.5 V.The nano LiMnPO4 composites with surface co-coating of Li2TiO3 and carbon have been successfully synthesized via quasi gel–sol method followed by thermal treatment. The samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The effect of surface coating with different amount of Li2TiO3 on the structure and electrochemical performance of LiMnPO4 is investigated. At a mass ratio of Li2TiO3/LiMnPO4 of 3%, the as-prepared products are composed of primary nanoparticles (30–50 nm), and Li2TiO3 by in-situ growing cross-links with the carbon to form the double coating on the surface of LiMnPO4. The co-coating layer of Li2TiO3/C distributes uniformly in the thickness of about 2.2 nm and 1.2 nm, respectively. Compared with the LiMnPO4/C sample, the Li2TiO3-coated LiMnPO4/C composite displays larger lithium ionic diffusion coefficient and higher cycle stability. Within, the 3 wt.% Li2TiO3-coated LiMnPO4 sample shows the best electrochemical performance, delivering the reversible capacity of 131.9, 125.8, 117.7 mAh g− 1 at 0.5, 1.0, 2.0 C, respectively, with a capacity retention of 92.9% after 240th at 2.0 C.

•A novel eco-efficient LiMnPO4 synthesis process was developed by involving mechano-chemical reaction between Mn and LiH2PO4.•In situ carbon coated LiMnPO4/C composites with a 20 ∼ 50 nm particle size distribution was successfully obtained.•LiMnPO4/C samples with reduced carbon amount displays excellent electrochemical performance.An eco-efficient approach bases on a mechano-chemical liquid-phase activation technique is developed for synthesizing LiMnPO4/C composites. The fine sized [Mn3(PO4)2·xH2O + Li3PO4] precursors with uniform particle size distribution are prepared, and characterized by XRD and scanning electron microscope (SEM). The in—situ carbon coated LiMnPO4 composites are synthesized by one-step solid state reaction. The prepared LiMnPO4/C nano-composites show a comparable rate capability with discharge specific capacity of 136.4 mAh g−1 at 0.05 C-rate and 118 mAh g−1 at 1 C-rate at room temperature. The results indicate that LiMnPO4/C composites synthesize from this environmental friendly route shows a promising electrochemical activity as cathode material for lithium ion batteries.A novel efficient synthesis process was developed involving mechano-chemical reaction between Mn and LiH2PO4 and the addition of PVA as carbon source for synthesis nano LiMnPO4/C composite material. The obtained composites displaying good rate capability and cyclic stability with an excellent discharge plateau around 4.0 V vs. Li/Li+.

•Well crystallized 100–300 nm MnPO4·H2O is achieved by a novel fast precipitation method.•A in situ carbon coated LiMnPO4 is synthesized by mechanochemical activation assisted carbothermal reduction route.•LiMnPO4/C sample with reduced carbon amount displays excellent discharge plateau and good rate capability.A fast precipitation method is adopted for synthesis of nano-MnPO4·H2O, with MnSO4·H2O, H3PO4, NH4NO3 and NaOH as raw materials. MnPO4·H2O precipitate is characterized by XRD (X-ray diffraction) and SEM (scanning electron microscope). Fine-sized, well-crystallized, carbon-coated LiMnPO4/C nano-composites are obtained by using mechanochemical activation assisted carbothermal reduction route from as-prepared MnPO4·H2O, Li2CO3 and PVA (polyvinyl alcohol). The effect of calcination temperature on the structure and properties of obtained materials is investigated by XRD, SEM, TEM (transmission electron microscopy) and electrochemical measurements. The in situ 6.8 wt% carbon coated LiMnPO4/C displays discharge specific capacity of 124 mAh g−1 at 0.05 C rate and 108 mAh g−1 at 1 C rate. The capacity retention is nearly 100% after 20 cycles at 1 C rate. This mechanochemical activation assisted precipitation technique is a facile approach for the fabrication of LiMnPO4 cathode materials.Fine-sized, well-crystallized, in situ carbon-coated LiMnPO4 powders with reduced carbon amount were obtained by a fast precipitation method, displaying good rate capability and cyclic stability with an excellent discharge plateau around 4.0 V vs. Li/Li+.

•LiNi0.5Co0.2Mn0.3O2 is coated with lithium titanium oxide via a facile process.•Lithium titanium oxide possesses high electronic conductivity.•Electrochemical performance of the LTO-coated NCM is significantly enhanced.Ni-based layered LiNi0.5Co0.2Mn0.3O2 (NCM) compounds coated with lithium titanium oxide for lithium ion batteries were successfully achieved through a simple solid state synthesis process using TiO2 powder and CH3COOLi. Systematical measurements in structure, morphology and electrochemical properties have been applied. X-ray diffraction patterns showed the existence and conversion of lithium titanium oxide (Li4Ti5O12 and Li7Ti5O12 are labeled as LTO). A coating layer in the form of LTO could be observed and the thickness was approximately 10 nm with uniform distribution. Similarly, XPS was performed to confirm the existence of LTO. 1.0 wt.% LTO-coated NCM material exhibited higher capacity retentions of 91.0% than that of the bare one (64.3%) after 100 cycles at cutoff voltages of 4.5 V. Meanwhile, the LTO-coated NCM material showed significantly improved thermal stability compared with the pristine sample at an elevated 60 °C. In addition, it has proved that it is effective to enhance the electrochemical performances of electrodes by LTO modification.