Multi-element doping enabling Co-free long-cycling high-voltage spinel cathodes

The high-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising cobalt-free cathode with high specific energy, attributed to its high operating voltage (approximately 4.7 V). However, its practical durability is limited by irreversible transition-metal migration, spinel-to-rock-salt phase reconstruction, high-voltage interfacial side reactions, and transition-metal dissolution. Herein, we report a multi-element-doped, cation-disordered spinel LiNi 0.4 Mn 1.4 Fe 0.05 Cr 0.05 Cu 0.05 Nb 0.05 O 4 (HELNMO) synthesized via a solid-state method. Rietveld refinement confirms a single-phase Fd 3̅ m structure with a slightly expanded lattice parameter (8.1857 Å for HELNMO versus 8.1776 Å for LNMO), and energy-dispersive X-ray spectroscopy mapping reveals a homogeneous distribution of the dopant elements. Structural and spectroscopic characterizations consistently confirm enhanced cation disorder in HELNMO, which contributes to favorable electrochemical performance by delivering approximately 130 mAh g −1 at 0.1 C and exhibiting markedly improved cycling stability, retaining 92% of its initial capacity after 1000 cycles at 2 C between 3.5 and 4.9 V. In-situ X-ray diffraction reveals smoother, more continuous lattice evolution of HELNMO than LNMO during (de)lithiation, consistent with a more homogeneous reaction pathway. Post-cycling analyses corroborate suppressed surface rock-salt reconstruction, reduced impedance growth, and alleviated Mn/Ni dissolution. Collectively, multi-element doping coupled with disorder engineering can effectively mitigate transition-metal migration and high-voltage interfacial degradation, providing a practical strategy for durable, high-energy spinel cathodes.