Improved interfacial contact and electrochemical performance of highly Ni-rich LiNixCoyMn1-x-yO2 (x>90%) cathode in all-solid-state lithium battery

Single-crystal LiNixCoyMn1-x-yO2 (SC-NCM) cathodes design is an effective solution for enhancing electrochemical performance of all-solid-state lithium battery (ASSLBs). For highly Ni-rich SC cathode (Ni>90%), the accumulation of local stress caused by anisotropic lattice shrinkage at deeply charging state is more destructive, and even SC-NCM design can not prevent the structure damage and interfacial contact failure between cathode and solid electrolyte (SE). In this work, small-size single-crystal design and Al-doping strategy are firstly combined to synthesize LiNi0.91Co0.04Mn0.04Al0.01O2 (S-SC-NCMA) cathode. Electrochemistry test, CP-SEM, GITT and in-situ EIS techniques are combined to reveal the interfacial evolution of cathode/SE. The kinetic limitation caused by local contact failure of cathode/SE and the formation of intergranular crack under high voltage are the main reason for capacity loss of ASSLBs. Small-size single-crystal design can reduce the volumetric strain effect and Al-doping strategy can further inhibit lattice shrinkage to improve contact. This work provides an effective cathode modification strategy for highly Ni-rich NCM (Ni>90%) cathode to improve high-voltage performance of sulfide-based ASSLBs.