Strategic germanium doping for Jahn-Teller suppression in high-voltage spinel LiNi0.5Mn1.5O4: multiscale analysis of interfacial dynamics and electronic structure evolution

High-voltage spinel LiNi 0 . 5 Mn 1 . 5 O 4 (LNMO) has emerged as a promising cobalt-free cathode candidate for lithium-ion batteries, yet its practical implementation is hindered by structural instability stemming from the Jahn-Teller effect. Herein, we propose an effective germanium doping strategy to suppress this effect. The optimized Ge Mof -LNMO exhibits exceptional electrochemical performance, delivering an initial capacity of 153.7 mAh g −1 at 0.1 C with remarkable cycling stability (82.1 % retention after 1000 cycles) while maintaining elevated operating voltages (4.67–4.53 V). Mechanistic investigations through electrochemical impedance spectroscopy coupled with distribution of relaxation times analysis at various charge states reveal that Ge incorporation enhances interfacial stability and charge transfer kinetics. Density functional theory calculations demonstrate that the formation of Ge-O bonds not only stabilizes the lattice structure but also optimizes electron distribution, effectively suppressing Jahn-Teller distortion. Notably, when paired with biomass-derived carbon (synthesized from Hami melon peel) as the anode in full cells, Ge Mof -LNMO demonstrates superior compatibility and cycling stability, highlighting its potential for practical applications. This work provides valuable design strategies for developing stable high-voltage spinel cathodes in next-generation energy storage systems.