Te doping stabilizes the P4332 structure and enhances the electrochemical performance of LiNi0.5Mn1.5O4 over 2.0–5.0 V

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) delivers a specific capacity above 140 mAh g⁻¹ within a wide voltage window of 2.0–5.0 V, owing to the additional Mn³⁺/Mn⁴⁺ redox activity at ~ 2.7 V. However, the induced cubic-to-tetragonal phase transition severely compromises its cycling stability. In this work, Te doping is employed to regulate the crystal structure of LNMO, leading to the formation of an ordered P4₃32 spinel phase. Electrochemical analyses (CV and EIS) demonstrate that Te doping effectively lowers electrode polarization, enhances electronic conductivity, and reduces internal resistance, thereby improving the cycling performance. The Te-doped LNMO achieves an energy density of 846 Wh kg⁻¹ (active-material basis), together with a capacity retention of 80.2% at 1C and 152.7 mAh g⁻¹ after 100 cycles. The performance enhancement is primarily attributed to the suppression of the cubic-to-tetragonal phase transition enabled by the ordered structure. In addition, Te doping decreases the Li⁺ migration barrier from 0.337 to 0.289 eV, resulting in an improved rate capability of 163.3 mAh g⁻¹ at 2C. These results highlight the effectiveness of Te doping in stabilizing high-voltage LNMO spinel cathodes and demonstrate their promise for high-energy-density lithium-ion batteries.