Enhanced Cyclability of LiNi_0.6Co_0.2Mn_0.2O₂ Cathodes by Integrating a Spinel Interphase in the Grain Boundary

Nickel-rich layered oxides are promising cathode materials for high-energy-density lithium-ion batteries. Unfortunately, the interfacial instability and intergranular cracks result in fast capacity fading and voltage fading during battery cycling. To address these issues, a coherent spinel interphase in the grain boundary of LiNi_0.6Co_0.2Mn_0.2O₂ (NCM) was successfully constructed via solution infusion and heat treatment. The results showed that the spinel (LiMn₂O₄) interphase could significantly reduce the formation of intergranular cracks during cycling. Meanwhile, the spinel structure on the primary particles effectively suppressed surface degradation, realizing the reduction of interface charge-transfer resistance and electrochemical polarization. As a result, the spinel-modified NCM cathode materials display superior electrochemical cyclability. The 1 wt % spinel phase-modified NCM delivers a discharge capacity of 154.1 mAh g⁻¹ after 300 cycles (1 C, 3−4.3 V) with an excellent capacity retention of 93%.