Speaker
Description
LiNiO₂ (LNO) offers the highest theoretical capacity (275 mAh g⁻¹) among layered cathodes but suffers from coupled structural and electronic instabilities at high voltage. We investigate Ti⁴⁺/Sb⁵⁺ co-doping, where Ti⁴⁺ serves as a bulk lattice modifier and Sb⁵⁺ as an interface architect due to their different charge mismatch with Ni³⁺. Cross-sectional SEM shows Sb-driven radial grain alignment that suppresses intergranular cracking. In-situ XRD and ⁷Li NMR reveal that both dopants disrupt Li/vacancy ordering, converting the abrupt H2→H3 phase transition into gradual solid-solution behavior, improving cycling retention from 80.2% to 95.9% under 1C for 100 cycles. Beyond structural stabilization, soft X-ray absorption spectroscopy (Ni L₃-edge and O K-edge) reveals a modification of the charge compensation mechanism: in LNO-TiSb, Ni oxidation saturates above 4.5 V while O participation continues to grow — an unexpected decoupling of Ni 3d and O 2p responses within the shared eg* antibonding band. Whether this originates from direct band modification or is an indirect consequence of the suppressed phase transition remains an open question to be addressed by DFT and RIXS.