Grain boundaries boost the prelithiation capability of the Li2CO3 cathode additives for high-energy-density lithium-ion batteries

Due to high theoretical capacity, Si anodes have attracted tremendous attention. Nevertheless, huge volume change during cycling together with large lithium loss substantially hinders their large-scale application. Prelithiation has emerged as a highly attractive strategy to compensate for the loss of active lithium. Li2CO3, which is ambient stable and delivers more than 5 times the theoretical capacity of the existing cathode materials, serves as an excellent cathode prelithiation additive. However, the practical application of Li2CO3 is limited by its sluggish charge transport and high critical decomposition potential. Herein, we report a facile route to fabircating nanosized Li2CO3 (N-Li2CO3) materials enriched with grain boundaries (GBs). First-principles investigations reveal that the Li-ion transport behavior is dependent on the concentration of GBs. The Σ(0 0 1) GB model exhibits higher Li-ion and electronic conductivities compared to those of the bulk counterpart. As a result, the ∼ 100 % capacity utilization of N-Li2CO3 with a delithiation capacity of 724 mAh/g is obtained, which is much higher than that of commercial Li2CO3 (115 mAh/g), greatly enhancing the reversible capacity, energy density and lifetime of the LiNi0.5Co0.2Mn0.3O2//Si-graphite full cell. These findings provide valuable understanding of the role of GBs and the correlation between microstructure engineering and performance optimization.