An overview of progress in the research on anode materials of lithium-ion batteries based on vanadium-based compounds (including vanadium oxide, vanadate, vanadate phosphate and oxide-free vanadium-based compounds) is presented. Furthermore, based on the analysis of relationship among modification method and structure of material and electrochemical performance, it is proposed that vanadium-based anode materials for lithium-ion batteries shall become the trend in the future research.

Lithium sulfide was prepared by solid phase syntheses, with lithium metal as the lithium source, sulfur powder as the sulfur source, and lithium nitride as the additive. Thermodynamic analysis results show that lithium nitride can promote the reaction of lithium metal with sulfur powder to synthesize lithium sulfide; Li₃N firstly reacts with sulfur powder to release N₂, leading to holes formed on the molten lithium metal sheet and the contact area between lithium metal and sulfur powder further expanded. Thus a loose and porous skeleton structure is formed, which is conducive to subsequent crushing and can reduce the risk of secondary reactions in the following ball milling process. With Li∶S∶Li₃N=2∶2∶0.4 (molar ratio), crude lithium sulfide can be obtained after 8 hours reaction at 100 ℃. It is then subjected to calcination, impurity removal and ball milling processes, and a kind of lithium sulfide products with purity greater than 99.95% and particle size less than 15 μm can be obtained, which can be used in EV. This method provides a new idea for industrial production of lithium sulfide products.

The influence of polyether additives on performance of ultra-thin Li-ion battery copper foil with thickness of 5 μm was studied by electrochemistry, scanning electron microscopy, and X-ray diffractometer. The results show that addition of polyether additives into electrolyte can promote negative shift of Cu deposition potential, and polyether additives with suitable concentration can lead to finer grains of copper foil, which is conducive to improving the surface flatness of copper foil. When the mass concentration of polyether additives is 2.3 mg/L, the obtained copper foil has tensile strength of 620.43 MPa, elongation of 3.67%, glossiness of 161 GU, and surface roughness of 1.02 μm, presenting excellent overall performance. The electrolytic copper foil with high tensile strength has a preferred orientation of (111) plane.

Based on an introduction of the structural characteristics of single-crystal Ni-rich ternary cathode material, the common preparation techniques of such material are summarized. Besides, the main strategies for improving the performance of this material in recent years are also discussed, which can provide a reference for large-scale production of such high-performance single-crystal Ni-rich ternary cathode material.

A flotation experiment was conducted for a low-grade fine-grained cassiterite from Yunnan. The median dosage of reagent was determined by a single-factor test, and then the reagent dosage for rougher flotation process of cassiterite was optimized by response surface methodology as follows: 285 g/t of activator (KT-51), 13 g/t of inhibitor (OL-1C) and 873 g/t of compound collector (YK-Sn+SN-705). A verification test on flotation with the addition of those agents yielded a tin rougher concentrate grading 1.460% Sn at 74.44% recovery, which was close to the results predicted by response surface methodology. In order to further explore the effect, a closed-circuit test was conducted, resulting in the tin concentrate grading 5.45% Sn at 66.70% recovery. It is shown that efficient recovery of low-grade cassiterite resources can be actualized.

In the flotation process of electrode materials from spent LiFePO₄ batteries, the occurrence of entrainment and entrapment usually leads to poor separation effect. Aiming at such problem, selective flocculation with polyvinylpiroxanone (PVP) and polyacrylic acid (PAA) was adopted to enhance the flotation effect in an experimental study, and the interaction mechanism between PVP and PAA and electrode materials was also analyzed. Results show that the firstly added PVP can be selectively adsorbed on the graphite surface by hydrogen bonding, thus inhibiting the spontaneous hydrophobic flocculation of graphite. Then, due to site-blocking effect, the subsequently-added PAA is inhibited to be adsorbed on the graphite surface, leading to selective flocculation of LiFePO₄ by PAA. A combined usage of PVP and PAA can not only make graphite effectively dispersed, but also lead to apparent particle size (D₅₀) of LiFePO₄ cathode material increased from 15.01 μm to 26.17 μm. As a result, the loss of LiFePO₄ due to entrainment in the flotation process of mixed electrode can be effectively reduced, thus the recovery rate of LiFePO₄ cathode material by flotation process can be improved from 71.41% to 83.59%.

To recover the copper resource therein, mineral processing of a slag-beneficiated copper sulfide ore from Congo (Kinshasa) with 9.62% Cu was investigated. A regrinding and reseparation flotation process was proposed based on multi-element chemical analysis and mineral occurrence analysis. It is found that with this process, a copper concentrates with Cu grade of 25.16% and Cu recovery of 90.67% can be collected.

In order to recover metal elements from the cathode materials of spent Li-ion batteries in an environmentally friendly and efficient way, three deep eutectic solvents (DES) were synthesized with choline chloride as hydrogen bond acceptor, malonic acid, succinic acid and adipate respectively as hydrogen bond donors. Then, Co and Li in the cathode materials of spent Li-ion batteries were leached by adopting these three DESs respectively. The effects of leaching time, liquid-solid ratio and reaction temperature on the leaching rates of Co and Li were explored, and the leaching residues were also characterized in terms of morphology and phase. The leaching mechanism was analyzed by FT-IR spectrum and UV-Vis absorption spectrum. It is shown that the leaching efficiency of metal elements can be enhanced by prolonging leaching time, increasing liquid-solid ratio and temperature. It is found that under the optimal conditions, including leaching time of 300 minutes, liquid-solid ratio of 100 mL/g, and temperature of 110 ℃, malonic acid-based DES, among those three kinds of DESs, can bring better leaching effect, with leaching rates of Co and Li all exceeding 99%. During the leaching of lithium cobalt oxide with those three DESs, Co exists in the form of bivalent in the leaching solution, and the coordination compound is in a tetrahedral structure.

LiMn_0.6Fe_0.4PO₄/C (LMFP) composite synthesized by a combined process of co-precipitation and solid-phase sintering not only has low impurity content, uniform phase distribution, but also exhibits excellent electrochemical performance. It is shown that such process can inhibit the formation of Mn₂P₂O₇ phase and improve the lithium ion diffusion rate of LMFP, while removing NH₄⁺ and H₂O. The Li-ion batteries assembled with LiMn_0.6Fe_0.4PO₄/C exhibit excellent electrochemical performance, showing initial specific discharge capacity of 145.5 mAh/g at 1C and 111.9 mAh/g at 5C. It is concluded that this process, being simple and cost-effective, is suitable for industrial production. Such study provides a feasible scheme in designing cathode materials for commercialized high-performance Li-ion batteries.

An argyrodite-type sulfide solid electrolyte Li₆PS₅Cl (LPSC) was solid-phase synthesized by adopting high energy ball milling in combination with heat treatment. It is found that prolonging ball milling time is conducive to crushing, mixing, grain refinement and amorphization reaction process of raw material powder; increasing sintering temperature is beneficial to the formation of a single pure phase, but too high temperature for sintering can make electrolyte melted and decomposed, leading to destroyed crystal structure. It is found that after 10 hours of ball milling and 8 hours of sintering at 550 ℃, the synthesized sulfide solid electrolyte exhibits higher ionic conductivity, reaching 3.57×10^-3S/cm.