All dry in one step (ADIOS to water) synthesis of W-coated Li1+x(Ni0·7Mn0.3)1-xO2

Abstract

Surface coatings have been used to improve the chemistry at the electrode-electrolyte interface of cathodes in lithium-ion batteries by forming a passivation film that can reduce side reactions with the electrolyte and can potentially offer enhanced electrochemical performance as well. Previous work in our group has shown that W-coated LiNiO2 electrode particles are more mechanically robust, which is reflected in the significantly improved cycling performance as microcracking is minimized. The application of these coatings, however, usually requires a separate processing step before or after lithiation of hydroxide precursors. Here, we propose combining a facile dry coating technique with the solid-state synthesis of cobalt-free cathode material Li1+x (Ni0·7Mn0.3)1-xO2 (Ni70Mn30), where W coated single crystal Ni70Mn30 is made in a one-step dry process from constituent compounds and a lithium source without any solvents. In this work, hydroxide precursors were bypassed completely and various precursor choices for the synthesis of cobalt-free materials were investigated. Cycling data shows that the W-coated single crystal Ni70Mn30 offers increased capacity without impacting lifetime and possesses excellent electrochemical performance. By adopting this direct synthesis approach, we believe that large amounts of wastewater and solid waste products can be eliminated while simplifying the cathode production process greatly.