Electrochemical behaviors in the anode of LiCoO2/mesocarbon microbead battery and their impacts on the capacity degradation

Though LiCoO2/mesocarbon microbead (MCMB) battery has wide application, its capacity loss mechanisms at different cycling stages are still not clear. Here, we report the electrochemical behaviors in MCMB anode at different stages and their impacts on the capacity degradation. The exfoliation of anode material from current collector tends to occur in single-side pasted region, which is one of the reasons for the quick capacity fading at early stage. After long-term cycles, MCMB anode has larger capacity loss than LiCoO2 cathode. The carbonates with poor Li+ conductivity are formed in the solid electrolyte interface (SEI) film at later stage. MCMB structure has no obvious variations. Lithium deposits appear on single-side pasted region firstly and then double-side pasted region. They are distributed more widely and become thicker with the cycling. The deposits contain metallic lithium while the battery at fully charged state and reduce the battery capacity significantly. Suppose each behavior exists in the whole MCMB anode, lithium deposit will have the most impact on the capacity loss; for the MCMB anode in full battery, SEI film has the largest effect. This work will help to improve the battery’s manufacturing techniques pointedly and obtain the lithium-ion batteries with high capacity and long life.