Negative electrode materials for lithium-ion batteries.48 volt golf cart batteries

　　In the early days, metal lithium was directly used as the negative electrode material, but during the charging and discharging process, dendritic lithium was generated, which could puncture the diaphragm and cause short circuits, leakage, and even explosions. Using Aluminium–lithium alloys can solve the problem of dendrite lithium, but after several cycles, there will be serious volume expansion and even powdering. The concept of rocking chair batteries has solved this problem by utilizing non-metallic materials with layered structures such as graphite to store lithium to avoid the generation of dendritic lithium, thereby greatly improving the safety of battery use [3].

　　Carbon materials can be divided into natural carbon materials and artificial carbon materials. Natural graphite materials have high graphitization degree, complete crystallization, multiple embedding positions, and large capacity, but are sensitive to electrolytes and have poor cycling stability. Artificial carbon materials include soft carbon materials and hard carbon materials. There is a large irreversible capacity in hard carbon materials. Adding potassium and boron into carbon materials and coating a layer of Ag, Zn, Sn [4] on the surface of carbon fibers can effectively improve the capacity and charge discharge efficiency of materials.

　　The addition of low melting point metals such as Bi, Pb, Sn, and Cd into lithium to form a lithium metal alloy has high reversible capacity. However, during the charging and discharging process, there will be volume expansion (up to 200%), resulting in powdering and poor contact between particles and electron transfer. The material synthesized by Dahn [5] by depositing Sn on the surface of electrochemical inert SnFe3C grains has good cycling performance, but low capacity.

　　In order to solve the problem of metal powder formation, Idota [6] proposed using metal oxides such as SnO2 instead of pure metals as anode materials. Metal oxide MO (M=Co, Cu, Ni, Fe, etc.) nanomaterials can still maintain a capacity of 700mAh • g-1 after 100 cycles [7]. In addition, other metal oxides such as InVO4, FeVO4, MnV2O6, and TiO2 also have significant lithium storage capacity, but their irreversible capacity is relatively large.

　　Recently, some transition metal nitrides, Li3-xMxN (M: Co, Ni, Cu), have been discovered to have excellent electrochemical stability and high reversible storage, with a charge discharge capacity of up to 760mAh • g-1 [8]. Li6Co0.4N has a capacity of up to 900mAh • g-1 [9] and can be used to improve the electrochemical performance of SnO. The study of its lithium intercalation mechanism found that after the first lithium removal, the material will transform from hexagonal phase to amorphous phase, and the amorphous phase can embed a large number of lithium ions.

　　5-nanometer silicon nanosilicon also has high lithium storage capacity and is currently a research hotspot. High capacity can be achieved by uniformly dispersing nano Si in electrochemical inert TiN lattice and depositing silicon onto porous nickel substrate to produce thin film silicon. By using chemical vapor deposition method to composite some nano silicon into carbon materials, the capacity of the material can be significantly increased, while the capacity of carbon coated silicon can reach 1200mAh · g-10.

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