To solve the problem of structural instability of cathode material (LiNi_0.8Co_0.1Mn_0.1O₂) (NCM)) during cycling, a strategy of  co-doping of Rb⁺ and Cl^- was proposed for NCM materials. The synergistic effect of  co-doping of Rb⁺ and Cl^- in the NCM lattice can increase the diffusion rate of Li⁺ and relieve the internal strain, thus hindering the mixing of Li⁺/Ni²⁺ during high cut-off voltage cycling. Electrochemical test results show that Li_0.99Rb_0.01(Ni_0.8Co_0.1Mn_0.1)O_1.99Cl_0.01 (RbCl-NCM) has a discharge capacity up to 176.9 mAh/g at a current density of 10C. The initial discharge capacity at  1C is 203.5 mAh/g.  After 200 cycles, its capacity retention ratio is as high as 87.8%,  showing an excellent cycling performance, while the capacity retention ratio of NCM material is only 57.3%.

With micron silicon powder as matrix, phosphorus-doped silicon-carbon composite material (Si-P@C) was synthesized by solid-state thermal diffusion and high-temperature pyrolysis, and then used as anode material of lithium-ion batteries. The results show that Si-P@C anode material demonstrates an initial discharge specific capacity up to 2 164 mAh/g  at a current density of 0.2 A/g. Compared with pure silicon, Si-P@C anode material presents greatly improved cycling performance. After 50 cycles at a current density of 0.5 A/g, it demonstrates a high reversible specific capacity of 1 176 mAh/g, with the capacity retention ratio of 73.5%. It is concluded that phosphorus-doping and carbon coating can effectively improve the electron transfer ability and reaction kinetics of silicon anode.

In order to study the effects of pores in surface-coated carbon layer on the rate performance of graphite cathode materials, a small amount of boric acid was added to generate gasification and effusion effect of boric acid during the softening stage of the coated asphalt. Then, a carbon layer with certain pores was formed on the surface of natural graphite tailings through carbonization, and graphite cathode materials with various proportions of pores were obtained. The results show that boric acid forms a carbon layer on the surface of particles containing mesoporous and macroporous pores. A higher proportion of mesopores in the surface carbon layer leads to more  diffusion channels for Li⁺ in the carbon layer L_C, and lower diffusion impedance of Li⁺. In that case, the rate performance and cycling performance of the material are enhanced.

To address the problems of low conductivity and poor cycling performance of silicon oxide as negative electrode material, polyacrylamide (PAM) was adopted as a carbon source for the first carbon coating, and the methane-acetylene mixture was used as a gas-phase carbon source for the second coating by chemical vapor deposition to prepare nitrogen-containing double-layer carbon-coated silicon oxide anode materials (SiO_x@DC-N). Compared with pure gas-phase coated (SiO_x@GC) and pure liquid-phase coated (SiO_x@LC) silicon oxide anode material, SiO_x@DC-N exhibits excellent rate performance and cycling stability, showing that the specific capacity is 850.1 mAh/g at a current density of 4C (1C=1 500 mA/g). The 18650 cylindrical batteries prepared by using a mixed graphite in a ratio of 5∶95 can have a capacity retention rate of 92.70% after 700 cycles of charging and discharging at a current density of 1C.

A kind of flake graphite with grain size D₅₀ of 40.3 μm from Inner Mongolia was taken in a spherification test by adopting a QCJ vortex micropulverizer, and two kinds of spherical products with D50 of 16.42 μm and 11.68 μm respectively were obtained, of which the corresponding tapped density increased from 0.46 g/cm³ to 0.95 g/cm³ and 0.80 g/cm³ respectively, presenting a total spherification rate of 50.48%. The spherical products were purified with mixed acid, with the fixed carbon content therein up to 99.95% and 99.97% respectively, and then the electrochemical performance of the products was tested. The anode material with those two products delivered initial discharge specific capacities of 366.60 mAh/g and 364.30 mAh/g, respectively, and presented initial charge-discharge efficiency of 93.40% and 92.32%, respectively. It is shown that the capacity retention rate can exceed 99% after 30 cycles at 0.1C current.

Activated carbon derived from coconut shell was prepared as anode material by adopting high temperature pyrolysis and activation. The effects of activation on the structure, morphology and electrochemical properties of coconut shell carbon were investigated by using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the coconut shell carbon after activation process is highly disordered, and also microporous and mesoporous. It delivers an initial discharge specific capacity of 918.22 mAh/g at a current density of 0.1 A/g, and retains a specific capacity of 447 mAh/g after 200 cycles discharge at a current density of 1 A/g.

Based on the relevant patents of layered cathode materials for sodium-ion batteries in China, a review of patent applications (authorization) is presented in terms of annual trend and main applicants. Also, some representative patents on precursors, structure, chemical washing and coating of layered cathode materials for sodium-ion batteries are chosen for analysis. Finally, the industry development trend, as well as technical difficulties and hotspot in this industry are summarized.

The advantages and disadvantages of several technologies for recycling spent LiFePO₄ batteries, including pre-treatment, hydrometallurgical process, and direct regeneration and repairing, were presented in terms of recovery efficiency, economic and environmental benefits, and commercial feasibility. The development trend of each technology is also analyzed. All these can serve as reference for optimizing and improving the technologies to recycle spent LiFePO₄ batteries in the future.

Based on a summary of the existing recovery technologies for spent LiFePO4, a brief introduction of repair and regeneration technologies for spent LiFePO4 cathode material is presented. The technical theory for selectively leaching spent LiFePO4 by hydrometallurgical approach, as well as the progress in the research of the existing technical schemes are specifically reviewed, and some new recovery techniques are also briefly introduced. Based on the comparison of the advantages and disadvantages of different technical schemes, the technical development trend for lithium recovery from spent LiFePO4 batteries is predicted.

Nickel, cobalt and lithium were recovered from cathode materials of spent NCM523 batteries by using a hydrometallurgical approach. And the sulfuric acid leaching solution of the cathode material was purified to remove impurities, and then used to prepare NiCo₂O₄ by adopting a process consisting of hydrothermal precipitation and calcination. Subsequently, a chemical precipitation approach was adopted to recover lithium therein. In the experiments, the influences of type of additives, hydrothermal temperature, reaction time and calcination temperature on the morphology of the product were investigated. With leaching solution of the cathode material as the raw material, oxalic acid as the precipitator and hexamethylenetetramine as the additive, hydrothermal reaction at 140 ℃ for 4 h produced precursors, which were then subjected to calcination at 300 ℃ for 2 h, yielding NiCo₂O₄ bars with uniform morphology. Finally lithium was precipitated from the mother solution of hydrothermal reaction, with the product of Li₂CO₃ obtained. It is concluded that recycling of valuable metals of nickel, cobalt and lithium from spent NCM523 batteries can be actualized by using this technical process.

An analysis of pre-lithiation technologies for silicon-based anode material is presented in terms of application trend, applicants and technical compositions of all related domestic and international patents, and the development situation and the key technical route is discussed based on those patents. It is found that currently, the pre-lithiation technologies for silicon-based anode material are growing rapidly without any uniform technical route. Among them, the chemical pre-lithiation strategies, especially based on thermal doping and organic lithium, are in a rapid development and most likely to firstly find industrial application for achieving commercialization. China is the main target market for the pre-lithiation technologies of silicon-based anode materials, but the domestic companies, compared to those foreign enterprises in China, have a weaker technical foundation and less accumulation of patents. Thus, it is recommended that the domestic companies should put more efforts in research and development, and also strengthen the related patent portfolio management.

A kind of composite (Si/C@G) was designed and synthesized by in-situ growth with MOF-derived carbon coated silicon nanoparticles that was confined in graphene composite, which was used as anode material of Li-ion batteries. Its special structure can effectively reduce the variation in the volume of silicon-based anode material during the charge-discharge process, thus promoting the formation of stable solid electrolyte interphase films, and improving conductivity of electrode materials. As a result, the anode material of Si/C@G composite can have reversible specific capacity still remaining at 1081.2 mAh/g after 100 cycles at a current density of 500 mA/g, and have reversible capacity reaching 949.6 mAh/g at a current density of 5.0 A/g. Besides, the anode material of Si/C@G can have the specific capacity remaining around 677.2 mAh/g after 500 cycles at a constant current density of 1.0 A/g, with the Coulomb efficiency up to 99.84%, indicating that it delivers a good cycling stability.

The progress in the R & D of three-dimensional porous micrometer-sized silicon anode material for Li-ion batteries was summarized in terms of its preparation methods, including metal-assisted chemical etching  of micrometer-sized silicon, acid etching of micrometer-sized silicon alloy, disproportionated acid etching of micrometer-sized SiO materials and magnesium thermal reduction of micrometer-sized SiO₂. The porous design for this three-dimensional porous micrometer-sized silicon anode based on micrometer particles can shorten the procedure and ensure a high compaction density. It is found that the pores in micrometer-sized porous silicon can reserve a space for the expansion caused by lithiation of silicon, leading to an improved cycle stability of silicon anode material. The preparation of micrometer-sized porous silicon by magnesium thermal reduction is free of toxic reagents and characterized by a great variety of raw material resources, low price, short process, thus easy to be applied into large-scale production. It is concluded that the three-dimensional porous micrometer-sized silicon anode material prepared by this method is expected to become the next generation of silicon-based anode materials.

In order to improve the structural stability and photoelectric conversion efficiency of perovskite, the effects of three isomers and B-site and X-site doping structures of CsPbI₃ on the structural stability and energy band structure were investigated by using First-Principle calculation and CASTEP calculation program. The results show that three isomers of monoclinic phase, rhombic phase and cubic phase are in descending order of stability, and the band gap of rhombic phase is 2.535 eV. With X-site doping, F-doping can greatly increase the band gap, leading to the band gap of CsPbI₃-F up to 2.659 eV; while Br-doping can adjust the band gap of CsPbI₃-Br to 1.7 eV. B-site doping can effectively improve the stability of cubic phase, and the binding energy of Ca-doped structure shows most obvious decrease.

The cathode material of Li₂FeP₂O₇/C was prepared by solid-phase ball milling method, and the influences of sintering temperature, carbon coating content and carbon source on the phase structure, morphology and electrochemical properties were studied. The results indicate that the Li₂FeP₂O₇/C appropriately synthesized at 680 ℃, with citric acid as carbon source and carbon coating content of 5%, has a complete crystal shape with smaller and uniform grain. The Li₂FeP₂O₇/C exhibits an initial discharge capacity of 102.6 mAh/g at 0.1C rate, and an initial discharge capacity of 83.4 mAh/g at 0.5C rate, a reversible capacity of 80.7 mAh/g after 30 cycles at 0.5C, showing better cycling and rate performance.

With isopropanol as a solvent, the precursor of cobalt carbonate was prepared by adopting the solvothermal method with different reaction time, and ultrafine nano/micron-structure porous Co₃O₄ spheres were then prepared by adopting a calcination process. The effect of reaction time on the compositions and morphology of cobalt carbonate and Co₃O₄ was investigated and the electrochemical properties of Co₃O₄ as an anode material of Li-ion batteries were also tested. Results show that micron-sized spheres (2~4 μm) are composed of ultrafine and uniform nano-sized Co₃O₄ spheres and pores. Under the current densities of 0.5 and 1 A/g, the prepared Co₃O₄ anode material exhibits excellent electrochemical performance, with the specific capacities held at 680 and 473 mAh/g after 450 cycles.

ZnO-modified carbon cloth was prepared by solvothermal method and high temperature calcination method, which was then used as the anode substrate to synthesize Li-ZnO/CC composite anode by using thermal fusion method. It is found that ZnO particles can reduce the nucleation overpotential of lithium and selectively regulate the deposition location of lithium, thus improving the cycle performance of batteries. The cycle performance of composite anode material (Li-ZnO/CC) is better than that of bare lithium foil in symmetrical batteries and NCM523 batteries. At a current density of 1 mA/cm2, Li-ZnO/CC symmetric batteries can maintain a stable cycle for at least over 400 h, with an overpotential maintained at about 10 mV. The NCM523|Li-ZnO/CC full cell delivered an excellent cycle performance after 305 cycles at 0.3C, with capacity retention maintaining at 80.41%. It is concluded that Li-ZnO/CC is a promising composite anode material for rechargeable batteries.

A spent lithium iron phosphate (LiFePO₄) battery was soaked in NaOH solution for the separation between the cathode material and the aluminium foil current collector therein. After a series of processes, including heat treatment, sand milling and mixing, and high temperature roasting, the regeneration of LiFePO₄ was actualized. The phase structure and morphology of the regenerated LiFePO₄ were characterized by X-ray power diffraction and scanning electron microscope. It is found that the generated LiFePO4 has its nanoscale particles distributed uniformly without agglomeration. The electrochemical test results reveal that the regenerated LiFePO₄ can display a specific discharge capacity of 165.2 and 101.5 mAh/g at 0.1C and 5C respectively; it still displays a discharge capacity of 150.1 mAh/g after 100 cycles at 1C, with a capacity retention of 97.85%, which indicates a good rate preformance and cycling performance. The process is simple and the generated product displays good electrochemical performances, indicating that the research can provide a reference for speeding up recycling and regeneration of spent LiFePO₄ batteries.

Mn₃O₄ was prepared by co-precipitation method, which was then coated with dopamine and subjected to sintering process, generating carbon-coated MnO@C. It can be used as a cathode material for zinc-ion batteries. The test results show that the assembled battery with this material has a specific capacity of 282.9 mAh/g at 0.2 A/g. After 500 cycles at 1 A/g, the specific capacity is 80.2 mAh/g. It is concluded that MnO@C can provide new ideas for the development of Mn-based zinc ion batteries.

Due to being abundant in natural resources and higher theoretical specific capacity, silicon anode material has been regarded as the most promising anode material for the next generation of lithium ion batteries. However, it also has some shortcomings, such as volume expansion, crushing and pulverization of active substances, separation between anode material and current collector, and poor conductivity during the course of lithiation. The lithiation mechanism and performance degradation of the silicon carbon anode material are reviewed here, including the introduction of recent progress and existing problems in the research on the structural design, such as the silicon carbon material, core-shell structure, egg yolk shell structure, sandwich structure and three-dimensional structure. On this basis, it is expected that the preparation and the three-dimensional structure design for the silicon carbon material being more simple and reliable with lower cost shall be the critical in the future.