Enhanced electrochemical performances of LiNi0.5Mn1.5O4 by surface modification with superconducting YBa2Cu3O7

Abstract

LiNi0.5Mn1.5O4 modified with superconducting YBa2Cu3O7 (YBCO) is synthesized by mixing as-prepared LiNi0.5Mn1.5O4 powders and the sol–gel-driven YBa2Cu3O7 matrix, subsequently followed by high-temperature calcinations. The effect of YBCO-modification on the electrochemical performances of LiNi0.5Mn1.5O4@YBCO cells in a wide operation temperature is investigated systematically by the charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the pristine LiNi0.5Mn1.5O4, LiNi0.5Mn1.5O4@YBCO samples exhibit higher capacity, better cyclability and higher rate capability in a wide operation temperature range. An analysis of the electrochemical measurements reveals that the improved performance of LiNi0.5Mn1.5O4@YBCO is due to the better electric contact among particles, much lower charge-transfer resistances and higher lithium diffusion rate, especially at low temperature. In addition, the homogeneous YBCO layer formed on the LiNi0.5Mn1.5O4 protects the active materials from chemical attack by HF, which suppresses the dissolution of Ni or Mn from LiNi0.5Mn1.5O4 in the LiPF6 based electrolyte.