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The lithium-rich manganese cathode material Li2MnO3·LiMO2 (M = Mn, Co, Ni, Fe, etc.) has been received extensive attention for Li-ion batteries owing to its ultra-high specific capacity (>250 mAh g−1) and lower cost. Nevertheless, it is still strictly challengeable to achieve encouraging Li-storage behaviors due to its poor cyclability, rate performance, and voltage decay. Li-rich manganese cathode material Li1.2Mn0.54Ni0.13Co0.13O2 (LRNCM) modified by a novel hybrid conductive layer constructed with Li1.4Al0.4Ti1.6(PO4)3 (LATP) and polyaniline (PANI) is prepared. The hybrid modification layer (LATP&PANI) not only serves as a physical barrier to protect the active material from the electrolyte, but also combines the high ionic conductivity of Li1.4Al0.4Ti1.6(PO4)3 with the excellent electronic conductivity of polyaniline, helping for facilitating the transfer of electrons and lithium ions. The hybrid modification cathode material (LRNCM@3 wt%LATP@1 wt%PANI) displays favorable rate capability and cycle performance, whose capacity retention (2.0–4.8 V at 0.2 C, 25 °C) deliveries 79% after 200 cycles. The hybrid modification is a promising route for remarkable enhancement in performance of the lithium-rich manganese-based cathode materials.

Ni-rich cathode material attracts a substantial amount of attention due to its high specific capacity, superior energy density and low cost. Nonetheless, there are still a few intrinsic issues which need to be solved including rate performance, cycling stability, elevated-temperature performance, etc. In this paper, the graphene-analogous structural MoS2 with chemical stability and acceptable conductivity is purposefully introduced to modify LiNi0.8Co0.1Mn0.1O2 cathode material via a facile wet-chemical approach followed by low-temperature reaction. In addition, lithium-active MoS2 coating layer can provide an interconnected and stable tunnel for the insertion and extraction of lithium ions. Characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, Raman, scanning electron microscopy and transmission electron microscopy demonstrate that MoS2 coating layer is uniformly deposited on the surface of LiNi0.8Co0.1Mn0.1O2 material. The electrochemical results indicate that the modified cathode material displays excellent structure stability, superior rate performance and outstanding cycling properties.

A series of layered Na0.67Lix(Ni0.2Fe0.15Mn0.65)1-xO2+δ (x = 0, 0.1, 0.2 and 0.3) compounds is prepared via a facile oxalate coprecipitation method and a solid-state reaction process, and investigated as the promising positive electrode materials for Na-ion batteries. As the Li content increases, O3 phase and Li2MnO3 gradually grow at the expense of the P2 phase and the particles become smaller and more agglomerated based on X-ray diffraction, scanning electron microscopy and transmission electron microscope results. The optimal Na0.67Li0.2(Ni0.2Fe0.15Mn0.65)0.8O2+δ shows the improved electrochemical performance with a high specific capacity of 151 mAh g−1 and 78% capacity retention over 50 cycles at 0.1 C (15 mA g−1). When tested at 5 C (750 mA g−1) rate, the electrode exhibits a discharge capacity of 68 mAh g−1. The results of electrochemical impedance spectroscopic and ex-situ X-ray diffraction measurements demonstrate that the improved cyclability and rate capability of the Li-substituted cathode can be ascribed to the decreased resistance and the enhanced structure stability in the high voltage of 4.3 V.

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.

In this paper, we propose a facile strategy to synthesize the porous structure TiO 2 @C composites through a two-step method, in which the precursor of MIL-125(Ti) was firstly prepared by solvent thermal method and then calcined under inert atmosphere. When employed as anodes for Na ion batteries, TiO 2 @C composites can exhibit a superior cyclability with a reversible sodium storage capacity of 148 mAh g −1 at the current density 0.5 A g −1 after 500 cycles and an excellent rate performance with a capacity of 88.9 mAh g −1 even the current reached to 2.5 A g −1 due to the dispersion of anatase TiO 2 throughout amorphous carbon matrix and the synergistic effect between the anatase TiO 2 nanocrystals and carbon matrix, which can availably enhance the electric conductivity and alleviate the volumetric variation of TiO 2 during the insertion/extraction process of Na + .

Ni-rich layered oxides LiNixTM1-xO2 (TM = Co, Mn, Al, x > 0.6) cathode materials for lithium-ion batteries have an anisotropic volume change during lithium deintercalation process, which easily causes microcracks and rapid capacity decay. In the paper, carbonate precursor prepared by a urea-based hydrothermal method is lithiated at different temperatures of 750–850 °C to obtain agglomerate LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material with different primary sizes. The sample synthesized at 750 °C shows broadening diffraction peaks due to its near-nano grain size, which results in the merging of (006)/(012) and (018)/(110) peaks. The effect of anisotropic volume shrinkage is effectively weakened by fine grain range, which alleviates formation of intergranular crack that is commonly considered as an important reason for capacity decay of Ni-rich layered oxide cathode materials. In addition, two new types of intragranular microcracks are first identified in cyclic NCM811. One extends along the spinel phase and layered phase interface, and the other extends along the vertical (003) R crystal plane. The difference in atomic plane spacing during the electrochemical cycles plays a key role in the growth of intragranular microcracks.

LiNi1−x−yCoxAlyO2 is a commonly used Ni-rich cathode material because of its relatively low cost, excellent rate capability and high gravimetric energy density. Surface modification is an efficient way to overcome the shortcomings of Ni-rich cathodes such as poor cycling stability and poor thermal stability. A high-powered concentration-gradient cathode material with an average composition of LiNi0.815Co0.15Al0.035O2 (LGNCAO) has been successfully synthesized by using spherical concentration-gradient Ni0.815Co0.15Al0.035(OH)2 (GNCA)as the starting material. An efficient design of the Al3+ precipitation method is developed, which enables obtaining spherical GNCA with ∼10 μm particle size and high tap density. In LGNCAO, the nickel and cobalt concentration decreases gradually whereas the aluminum concentration increases from the centre to the outer layer of each particle. Electrochemical performance and storage properties of LGNCAO have been investigated comparatively. The LGNCAO displays better electrochemical performance and improved storage stability than LNCAO.

The nanostructured 0.9LiMn 0.9 Fe 0.1 PO 4 ·0.1Na 3 V 2 (PO 4 ) 2 F 3 /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 Na 3 V 2 (PO 4 ) 2 F 3 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 0.9LiMn 0.9 Fe 0.1 PO 4 ·0.1Na 3 V 2 (PO 4 ) 2 F 3 /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.

Ultrathin molybdenum diselenide nanosheets are decorated on the surface of multi-walled carbon nanotubes (MWCNT) via a one-step hydrothermal method. Uniform MoSe2 nanosheets are firmly anchored on MWCNT according to the characterizations of scanning electron microscope (SEM), transmission electron microscope (TEM). When evaluated as anodes for sodium storage, the MoSe2@MWCNT composites deliver a reversible specific capacity of 459 mAh g−1 at a current of 200 mA g−1 over 90 cycles, and a specific capacity of 385 mAh g−1 even at a current rate of 2000 mAh g−1, which is better than the MoSe2 nanosheets. The enhanced electrochemical performance of the MoSe2@MWCNT composites can be ascribed to the synergic effects of MoSe2 nanosheets and MWCNT. The high capacity and good rate performance reveal that the MoSe2@MWCNT composites are very promising for applications in sodium-ion batteries.

A conducting polypyrrole thin film is successfully coated onto the surface of LiCoO 2 by a simple chemical polymerization method. The structure and morphology of pristine LiCoO 2 and PPy-coated LiCoO 2 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 LiCoO 2 . The PPy-coated LiCoO 2 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 LiCoO 2 is only 83.5%. The rate capability results show that the reversible capacity retention (10 C /0.2 C ) of LiCoO 2 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 (LiCoO 2 ) from corrosion causing by the HF attacking and greatly reduce the dissolution of Co into electrolyte.

An eco-efficient approach bases on a mechano-chemical liquid-phase activation technique is developed for synthesizing LiMnPO 4 /C composites. The fine sized [Mn 3 (PO 4 ) 2 · x H 2 O + Li 3 PO 4 ] precursors with uniform particle size distribution are prepared, and characterized by XRD and scanning electron microscope (SEM). The in—situ carbon coated LiMnPO 4 composites are synthesized by one-step solid state reaction. The prepared LiMnPO 4 /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 LiMnPO 4 /C composites synthesize from this environmental friendly route shows a promising electrochemical activity as cathode material for lithium ion batteries.

A high-powered concentration-gradient cathode material with an average composition of Li(Ni0.85Co0.12Mn0.03)O2 has been successfully synthesized by a co-precipitation method. The Li(Ni0.85Co0.12Mn0.03)O2 has a core of Li(Ni0.9Co0.1)O2 that is rich in Ni and a concentration-gradient shell having decreased Ni content and increased Mn content. The electrochemical properties of the concentration-gradient material are studied and compared to those of the core Li(Ni0.9Co0.1)O2 material alone. In the concentration-gradient material of Li(Ni0.85Co0.12Mn0.03)O2, the Ni-rich core delivers a very high capacity, while the Mn-rich concentration-gradient shell improves the cycling stability and rate performance. The electrochemical properties of this cathode material are found to be far superior than those of the core Li(Ni0.9Co0.1)O2 material. At room temperature, the initial capacity of the concentration-gradient Li(Ni0.85Co0.12Mn0.03)O2 is 195 mAh g−1 at 1C between 2.8 and 4.3 V and retains 95.5% after 100 cycles. Moreover, the composite has a good rate performance with a high capacity of about 190 mAh g−1 even at 2C rate.

The effects of sodium additive on the microstructure and electrochemical properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O2-based material have been investigated. XRD patterns show that the sodium additive doesn't incorporate into the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 lattice, but induces a dispersed secondary phase with the structure of Na0.7MnO2.05. The two-phase composite shows an improved rate performance in comparison with the single phase of Li[Li0.2Mn0.54Ni0.13Co0.13]O2, which can be attributed to the enhanced electrical conductivity and lithium ion diffusion. The interfaces between Li[Li0.2Mn0.54Ni0.13Co0.13]O2 and the secondary phase provide fast diffusion paths for Li+. DC electrical conductivity and EIS are used to elucidate the phenomenon.

The storage properties of LiNi0.8Co0.15Al0.05O2 and LiCoO2-coated LiNi0.8Co0.15Al0.05O2 have been investigated comparatively. It is found that the latter exhibits better storage stability than the former. After storage in air at different relative humidities, LiCoO2-coated LiNi0.8Co0.15Al0.05O2 shows little changes in the aspects of weight, nickel oxidation state, moisture and carbon contents and electrochemical performance. However, for LiNi0.8Co0.15Al0.05O2, the higher the air humidity is, the bigger these aspects change. Fourier transformed infrared (FTIR) spectrum reveals that LiCoO2-coated LiNi0.8Co0.15Al0.05O2 is resistant to H2O and CO2 in air. X-ray photoelectron spectroscopy gives evidence that the LiCoO2 coating layer suppresses effectively the reactions between LiNi0.8Co0.15Al0.05O2 and atmosphere, which contributes to the enhancement of storage performance of LiCoO2-coated LiNi0.8Co0.15Al0.05O2.

Na 3 V 2 (PO 4 ) 3 of the rhombohedral NASICON structure has been prepared via solid state carbothermal reduction reaction assisted by mechanochemical activation. As a cathode material for hybrid lithium ion batteries, Na 3 V 2 (PO 4 ) 3 exhibits an initial specific discharge capacity of 114.2 mAh g −1 in the voltage range between 2.5 V and 4.6 V, with a long discharge plateau near 3.7 V versus lithium metal. Approximately 3% of the discharge specific capacity is lost over the first 3 cycles at a current rate of 0.1 C. Then, the capacity appears to stabilize with the discharge specific capacity retention of 97.4% over the following 97 cycles. The material also exhibits good rate performance. Reversible capacities of 107.0 mAh g −1 at a 1 C rate, 100.5 mAh g −1 at 5 C and 84.4 mAh g −1 at 10 C have been obtained. The preliminary results prove that Na 3 V 2 (PO 4 ) 3 is a new promising material for hybrid lithium ion batteries.

LiNi0.8Co0.15Al0.05O2 cathode material for lithium-ion batteries is synthesized by sintering the precursor Ni0.8Co0.15Al0.05OOH, which is prepared from the corresponding metal sulphates solution by a co-oxidation-controlled crystallization method. The effects of calcination temperature and time on the electrochemical performance of the material are investigated on the basis of TG-DSC analysis. XRD analyses show that the powders obtained by calcination at 700 °C for 6 h have the best-ordered hexagonal layer structure. SEM images show that these powders are spherical particles with diameter in the 5–12 μm range. The XPS measurement and the chemical titration display that Ni ions of these powders are in the form of Ni3+. The charge–discharge tests demonstrate that these powders have the best electrochemical properties, with an initial discharge capacity of 196.8 mAh g−1 and capacity retention of 96.1% after 50 cycles when cycled at a current density of 0.2 C between 2.8 and 4.3 V. Besides, these powders have also exhibited excellent rate capability and high-temperature performance.

A series of LiMn 2− x Cr x O 4 ( x =0, 0.01, 0.05, 0.1, 0.2) has been synthesized by a modified citrate route with combustion. The influence of the substitution of Cr for Mn on the electrochemical performances was investigated and compared. The results show that Cr substitution in spinel LiMn 2 O 4 can effectively depress the capacity fading over 4 V and improve the cycleability.

Effects of rare earth composition on the high-rate capability and low-temperature capacity of AB 5 -type hydrogen storage alloys have been studied and analyzed with pattern recognition methods. The results show that the increase of Ce and Pr and the decrease of La and Nd concentration improve the high-rate capability and low-temperature capacity of AB 5 -type hydrogen storage alloys, Ce exhibiting better favorable influences than Pr. The improvement of both high-rate capability and low-temperature capacity are mainly ascribed to the lower stability of the hydride. The alloy with the rare earth composition of La 0.1645 Ce 0.7277 Pr 0.0234 Nd 0.0845 shows very good high-rate capability and low-temperature capacity.