In-situ coating and surface partial protonation co-promoting performance of single-crystal nickel-rich cathode in all-solid-state batteries

The poor electrochemical performance of all-solid-state batteries (ASSBs), which is assemblied by Ni-rich cathode and poly(ethylene oxide) (PEO)-based electrolytes, can be attributed to unstable cathodic interface and poor crystal structure stability of Ni-rich cathode. Several coating strategies are previously employed to enhance the stability of the cathodic interface and crystal structure for Ni-rich cathode. However, these methods can hardly achieve simplicity and high efficiency simultaneously. In this work, polyacrylic acid (PAA) replaced traditional PVDF as a binder for cathode, which can achieve a uniform PAA-Li (Li_xPAA (0 < x ≤ 1)) coating layer on the surface of single-crystal LiNi_0.83Co_0.12Mn_0.05O₂ (SC-NCM83) due to H⁺/Li⁺ exchange reaction during the initial charging-discharging process. The formation of PAA-Li coating layer on cathode can promote interfacial Li⁺ transport and enhance the stability of the cathodic interface. Furthermore, the partially-protonated surface of SC-NCM83 casued by H⁺/Li⁺ exchange reaction can restrict Ni ions transport to enhance the crystal structure stability. The proposed SC-NCM83-PAA exhibits superior cycling performance with a retention of 92% compared with that (57.3%) of SC-NCM83-polyvinylidene difluoride (PVDF) after 200 cycles. This work provides a practical strategy to construct high-performance cathodes for ASSBs.