Orientation-Controlled Growth of LiNi0.5Mn1.5O4 Layers Directly Deposited on Current Collectors By Using Flux Coating and Their Electrochemical Properties

Newly developed cathode structures are strongly required for the improvement of LIB properties, including energy and power density, lifetime. Conventionally used cathodes consist of micrometer sized polycrystals of active materials, and additives that facilitate Li ion and electron transportation. Use of nanosized single crystals is expected to make huge improvements because those nanostructures might provide shorter diffusion pathways for ionic transportation. Here, we proposed fabrication of densely-packed orientationaly-controlled LiNi_0.5Mn_1.5O₄ (LNMO) crystal layers directly onto a current collector using flux-coating. As shown in Figure 1, SEM observations revealed that those crystals have octahedral shape with well-developed facets. This shape reflected well the crystal structure of LiNi_0.5Mn_1.5O₄, which belongs to cubic system with Fd-3m space group. Even though the filling rate of the LiNi_0.5Mn_1.5O₄ crystal in the positive electrode reached more than 95% without any additives, the crystal layer exhibited excellent LIBs properties as same as conventionally used powdered electrode with an assistance of many additives. The first charge and discharge capacities of the LIB, containing 14 mm-thick LiNi_0.5Mn_1.5O₄ crystal layer as a cathode were 111 and 105 mA∙h∙g^-1 at 1 C. The retention rate after 30 cycles was 97% for each cycle at 0.3C. These results proved that the flux-coating offered growth of seamlessly connected layers of LNMO crystals on current correctors. Further detail crystallographic natures and electrochemical characteristics of other active material crystals will present in the ECS 227th Meeting.