Insertion of lattice strains into ordered LiNi_(0.5)Mn_(1.5)O_4 spinel by mechanical stress: A comparison of perfect versus imperfect structures as a cathode for Li-ion batteries

摘要

The Ni-doped lithium manganese oxide, LiNio.5Mn1.5O4, has received much attention as a cathode material in high-energy lithium-ion batteries (LIBs). This active material has two different spinel structures depending on the ordering state of the Ni and Mn ions. The ordered LiNi_(0.5)Mn_(1.5)O_4 spinel has an inferior cathode performance than the disordered phase because of its poor electronic conductivity. However, the ordered LiNi_(0.5)Mn_(1.5)O_4 spinel possesses the potential advantage of avoiding dissolution of the Mn ion, which is an issue for the disordered spinel. The improvement of cathode performance is important for future applications. Here, we report a unique approach to improve the cathode performance of the ordered LiNio.5Mn1.5O4 spinel. The mechanical treatment using an attrition-type mill successfully inserted lattice strains into the ordered LiNi_(0.5)Mn_(1.5)O_4 spinel structure without a phase transformation to the disordered phase. The insertion of lattice strains by mechanical stresses provided an increased discharge capacity and a decreased charge transfer resistance. This limited crystal structure modification improved the cathode performance.