Low-concentration donor-doped LiCoO2 as a high performance cathode material for Li-ion batteries to operate between −10.4 and 45.4 °C

Abstract

The majority of electrode materials suffer from severe capacity fading on cycling at elevated temperatures or poor conductivity and diffusion of Li⁺ at low temperatures, which have made it very difficult for lithium-ion batteries to operate at low temperatures and/or elevated temperatures without loss of electrochemical performance. In this work, we report on a new strategy for tackling this issue through low-concentration donor-doping of higher valence Mn ions in LiCoO₂, a typical commercial cathode for many lithium-ion batteries. Firstly, low-concentration Mn-doped LiCoO₂ was successfully synthesized using a molten-salt method, in which solvent NaOH provides an alkaline environment that makes the reactant mixture uniform in reaction process and ensures the valence state of Mn ion at +4. Secondly, the chemical compositions for all samples were systematically tuned, while retaining the single-phase nature. The electrochemically inert Mn⁴⁺ was found to significantly enhance the structure stability, conductivity, and diffusion rate of LiCoO₂. As a consequence, the cathode material with a composition of LiCo_0.95Mn_0.05O₂ exhibited an excellent electrochemical performance in a temperature range from −10.4 to 45.4 °C. The finding reported in this work will be conducive to the applications of lithium-ion batteries under different temperature conditions.