Enabling superior cathode/sulfide electrolyte interfacial stability by Li3BO3 coating for all solid-state Li battery

The interface instability between a Li-excess cation disordered rocksalt cathode (DRX) and sulfide solid electrolyte (SE) results in rapid capacity fade. It is well established that cathode coatings are important to mitigate the side reaction at interfaces and therefore increasing the reversible specific capacity of all-solid-state Li batteries (ASSLBs). However, internal mechanism remains blurry, and the effects of the coating layer on electrode/electrolyte interface and capacity degradation have not been fully clarified. In this work, we used various coating materials on Li_1.2Ni_0.3Ti_0.3Nb_0.2O₂ (LNTNO) cathodes to investigate the behavior of the DRX/SE interfaces. The electrochemical performances are compared of uncoated, Li₂ZrO₃-coated, LiNbO₃-coated, and Li₃BO₃ (LBO)-coated cathodes in Li₆PS₅Cl-based ASSLBs in long charge–discharge processes. The results demonstrate that all coated LNTNO could improve specific capacity and cycle performance. Li₃BO₃ is identified as a superior coating with good structural stability that exhibits observably large discharge capacity (206 mAh g⁻¹ at 10 mA g⁻¹), long cycle life (100 cycles, capacity retention of 78%), as well as outstanding rate property. Combined with ex situ X-ray photoelectron spectroscopy and scanning electron microscope, we can observe the side reactions at cathode/electrolyte interface can be mitigated after the LBO coating layer, enabling fast lithium transport dynamics. This work highlights the critical role of having an appropriate coating layer and offers a promising path to enhance the electrochemical behaviors of ASSLBs.

Graphical abstract