Sol-gel synthesis of aliovalent vanadium-doped LiNi_0.5Mn _1.5O₄ cathodes with excellent performance at high temperatures

Extraordinary performance at elevated temperature is achieved for high-voltage spinel-phase LiNi_0.5Mn_1.5O₄ cathodes prepared using an adipic-acid-assisted sol-gel technique and doped with vanadium. V-substitution in the Li sites (Wykoff position 8a) is confirmed by V K-edge X-ray absorption spectroscopy and Rietveld refinement (Li _0.995V_0.005Ni_0.5Mn_1.5O₄). V-doped LiNi_0.5Mn_1.5O₄ delivered a reversible capacity of approximately 130 and 142mAh g^-1 at ambient and elevated temperature conditions, respectively. Furthermore, the Li_0.995V _0.005Ni_0.5Mn_1.5O₄ phase rendered approximately 94 % and 84 % of initial capacity compared to approximately 85 % and 3 % for the LiNi_0.5Mn_1.5O₄ phase after 100 cycles in ambient and elevated temperature conditions, respectively. The enhancements are mainly because of the suppression of Mn dissolution and unwanted side reaction with electrolyte counterpart, and to the increase in conductivity, improving the electrochemical profiles for the V-doped phase. V for victory: Aliovalent V-substitution in tetrahedral sites of Li in high-voltage spinel-phase LiNi_0.5Mn_1.5O₄ cathodes results in high performance at elevated temperatures. Vanadium doping suppresses Mn dissolution and unwanted side reactions with the electrolyte, and increases the conductivity, resulting in an improvement in the electrochemical performance at high temperatures.