Composite Cathode Material Using Spark Plasma Sintering for Bulk-Type Hybrid Solid-State Batteries

A Composite cathode without polymer binder was prepared by a one-step sintering method employing spark plasma sintering (SPS) of laminated LiCoO2 and Li3BO3 pellets. The amorphous Li3BO3 solid electrolyte melted during the sintering process. For better characterization of the composite cathode, a liquid electrolyte was used in the battery test. However, the active material was mainly in the all-solid-state environment. The specific capacity of the composite cathode was found to be dependent on its thickness. The 0.2 mm thick composite cathode showed a high specific discharge capacity of 99 mAh g (-1) at 0.5 C rate, excellent cycling performance over 10 cycles, and good rate capability of about 93.2 mAh g (-1) with 94% retention capacity. In addition, the composite cathode showed an initial discharge capacity of 0.25 mAh g (-1). The discharge capacity after 3 cycles under the all-solid-state condition was 0.22 mAh g (-1). The SEM and TEM results showed that the melted Li3BO3 solid electrolyte synthesized by the SPS process produced Li+ ion transport pathways, which reduced the grain boundary resistance. Hence, this composite cathode consisting of LiCoO2 as the cathode, amorphous Li3BO3 as the solid electrolyte, and MWCNT as the electric conductor is a promising material for all-solid-state batteries and bulk-type hybrid solid-state batteries.