A Liquid and Waste-free Method for Preparing Single Crystal Positive Electrode Materials for Li-ion Batteries

Abstract

Nickel-rich layered positive electrode materials are normally made by a “co-precipitation-sintering” method. Mixed transition metal hydroxides called “precursors” are prepared by co-precipitation to ensure homogeneous cation mixing at the atomic level and to create spherical particles which ensure high-performance poly-crystalline materials. Single crystal materials, which show better capacity retention in long-term cycling can be made from the same mixed transition metal hydroxide precursors by sintering at a higher temperature which inevitably destroys the spherical morphology present in the initial precursors. Here we describe a method for single crystal positive electrode material production which we call “all-dry synthesis” since it does not require the use of any liquid and creates no waste unlike the co-precipitation method. The exemplary reaction between Ni, MnCO3, and LiOH·H2O was studied in situ by synchrotron XRD in order to define a proper heating scheme for the all-dry process. The crystal structure, particle morphology, surface residual impurities, and electrochemical performance of materials prepared by the “all-dry synthesis” method are equivalent to or even better than those of materials made using a conventional co-precipitation method.