Stabilized Structure of High-Voltage LiNi_0.5Mn_1.5O₄ via Suppressing Phase Transition and Manganese Dissolution

LiNi_0.5Mn_1.5O₄ (LNMO) spinel cathode materials possess the advantages of a high discharge potential and rapid lithium-ion dynamics, offering significant application potential in the field of power batteries. However, under extreme conditions such as high temperature, it faces serious phase transformation and crosstalk of metal ion dissolution. To address the aforementioned issues, the coprecipitation method is adopted to doping Cu²⁺ into interstitial sites, which suppresses the phase separation behavior of LNMO and enhances the structural stability of the LNMO. Bond valence sum calculations show that the doping of Cu²⁺ increases the energy required for manganese ions diffusion from 16d to 16c lattice site, which is beneficial for suppressing the migration and dissolution of manganese ions, thereby resisting structural degradation. In situ X-ray diffraction proves that interstitial-site copper is beneficial to resist lattice expansion during charge and discharge. The doping of Cu²⁺ is also advantageous for enhancing the electronic conductivity of LNMO. The specific discharge capacity is 108.4 mAh g⁻¹ at 20 At 1 and 55 °C, after 100 cycles, the capacity retention rate is 96.8%. The insights gained from this study open up new horizons for strengthen the structural stability of LNMO.