Enhanced Fast-Charging Capability in Spinel LiMn2O4 via K+ Ion Stabilization for Advanced Lithium-Ion Batteries

Spinel LiMn₂O₄ (LMO) is a promising fast-charging cathode material because its unique three-dimensional Li-ion diffusion channels offer favorable ionic diffusivity. However, LMO encounters rapid structural degradation at high current densities. To tackle this issue, we introduce K⁺ ions into the interstitial 16c sites to stabilize LMO, thereby achieving excellent fast-charging capability. The K-LMO retains 75% of its theoretical capacity at an ultrahigh current density of 1.48 A g^–1 (10 C, corresponding to a charging time of 5 min). Comprehensive characterizations demonstrate that the incorporation of K⁺ into LMO expands the LiO₄ space, strengthens the Mn–O bonds and suppresses the Jahn–Teller effect, leading to improved Li-ion mobility and enhanced stability of the diffusion channels. Additionally, the volume variation induced by cycling under a high charge state is efficiently suppressed through a solid-solution transition, thus preventing structural degradation against long-term cycling. Given this, this study presents an attractive candidate material for the cathode of fast-charging lithium-ion batteries.