Study on the electrochemical performance of all-solid-state lithium battery based on Li3BO3 gradient coated LiCoO2 cathode

The interfacial issue of cathode//Li7La3Zr1.4Ta0.6O12 solid electrolyte has seriously hindered the development of all-solid-state lithium batteries. Herein, a gradient coating structure of cathode is constructed by chemically coating Li3BO3 on surface of LiCoO2 particles (LBO@LiCoO2-G). The battery based on the gradient coated cathode has a high capacity of 136.0 mAh g-1, which is 247 % higher than that of the uncoated LiCoO2 battery (39.2 mAh g-1). The capacity is still high as 103.4 mAh g-1 after 100 cycles with a capacity retention rate of 76 %. The gradient coating structure has good interfacial bonding effect that the battery resistance is low of 290 omega after cycling. The interfacial Li+ diffusion coefficient DLi+ (9.95 x 10-16 cm2 s-1) is almost two orders of magnitude higher than that of the uncoated LiCoO2 (1.03 x 10-17 cm2 s-1), and the DLi+ in LBO@LiCoO2-G cathode is obviously higher than that of the unmodified LiCoO2 cathode, indicating that Li3BO3 can greatly promote the Li+ transmission at the interface as well as between LiCoO2 particles. Besides, the gradient coating structure of cathode is more advantageous to the electron and Li+ conduction, and has a higher proportion of LiCoO2 active material which is favorable for obtaining higher cell capacity.