From Li$_2$NiO$_3$ to high-performance LiNiO$_2$ cathodes for application in Li-ion and all-solid-state batteries

The synthesis of LiNiO$_2$ (LNO) typically involves oxidizing Ni(II) to Ni(III), thus leading to Ni$_{Li}$ point-defect formation. Here, materials containing Ni(IV) in the form of overlithiated Li$_{1+x}$Ni$_{1−x}$O$_2$ (0 ≤ x ≤ 1/3) are converted into LNO. This method produces low defect-density samples at high temperatures, offering an attractive route toward coarse-grained particles that are naturally coated by the byproduct Li$_2$O. In thiophosphate-based solid-state batteries, this kind of self-coating effect shows a direct correlation between residual lithium content and cycling performance.