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The characteristics of tin alloy as anode material

wallpapers Tech 2021-01-08
Tin alloy
SnCoC is a kind of material that has been commercialized successfully among tin alloy anode materials. It uniformly mixes Sn, Co, and C at the atomic level and is not obtained by crystallization treatment. This material can effectively inhibit the electrode during charge and discharge. The volume change of the material improves the cycle life. For example, in 2011, Japan’s SONY announced the use of Sn-based amorphous materials as the negative electrode of the 18650 cylindrical battery with a capacity of 3.5AH. The theoretical specific capacity of elemental tin is 994mAh/g, which can form intermetallic compounds with other metals such as Li, Si and Co. For example, Xue et al. first prepared a Cu film carrier with a three-dimensional porous structure by electroless plating, and then supported Sn-Co alloy on the surface of the Cu film carrier by surface electrodeposition, thereby preparing a Sn-Co alloy with a three-dimensional porous structure.
 
The first discharge specific capacity of this material is 636.3mAh/g, the first coulombic efficiency reaches 83.1%, and the specific capacity can still reach 511.0mAh/g after 70 charge-discharge cycles. Wang et al. used graphite as a dispersant and a mixture of SnO/SiO and metallic lithium as the reactant. They used high-energy mechanical ball milling and post-heat treatment to prepare a Sn/Si alloy uniformly dispersed in a graphite matrix. The material was charged and discharged after 200 cycles. After cycling, its reversible capacity can still reach 574.1mAh/g, which is better than a single negative electrode material such as SnO or SiO.
 
Tin oxide
SnO2 has attracted much attention because of its high theoretical specific capacity (781mAh/g). However, it also has some problems in the application process: the first irreversible capacity is large, and there will be a large volume effect (volume expansion 250 %~300%), easy to reunite during the cycle, etc.
 
Studies have shown that by preparing composite materials, the agglomeration of SnO2 particles can be effectively inhibited, and the volume effect during lithium intercalation can be alleviated, and the electrochemical stability of SnO2 can be improved. Zhou et al. prepared SnO2/graphite composites by chemical deposition and high-temperature sintering. At a current density of 100mA/g, the specific capacity can reach 450mAh/g or more, and at a current density of 2400mA/g, the reversible specific capacity exceeds 230mAh/g. , Experiments show that graphite as a carrier can not only disperse SnO2 particles more uniformly but also effectively inhibit particle agglomeration and improve the cycle stability of the material.

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