Enhancement of battery performance of LiMn2O4: correlations between electrochemical and magnetic properties

Abstract

We report the results of a systematic investigation of structural, electrical transport, magnetic, and electrochemical properties of LiB_xMn_2−xO₄ (where x = 0.0–1), synthesized via a one-step solid state reaction technique. We find that the parent compound (x = 0) has the non-stoichiometric Li_1.05Mn₂O₄ phase and the B ions successfully incorporate the structure for x ≤ 0.5. The resistivity anomaly of the parent compound below 100 K is attributed to the antiferromagnetic correlations. The linear part of the χ⁻¹–T data are used to calculate the effective magnetic moments and to determine the total number of Mn³⁺ and Mn⁴⁺ ions. Magnetization measurements show that Jahn–Teller active Mn³⁺ ions have high spin configuration. Average valance of Mn ions increases with increasing boron content. Electrochemical studies show improved capacity retention for x = 0.125 for 100 charge–discharge cycles. This improvement is attributed to subtle modifications in the structural and magnetic properties upon substitution.