The effect of the LiCoO2/Li7La3Zr2O12 ratio on the structure and electrochemical properties of nanocomposite cathodes for all-solid-state lithium batteries

Using a self-assembled block copolymer (BCP) structure as a template, an inorganic nanocomposite consisting of a cathode active material (LiCoO2) and an electrolyte (Li7La3Zr2O12) was synthesized as a candidate electrode material for all-solid state lithium batteries. The precursors of the cathode active material and those of the electrolyte were introduced into separate polymer blocks of the BCP, and then calcination was used to remove the BCP template and crystallize the cathode active material and the electrolyte. The LiCoO2/Li7La3Zr2O12 ratio that produced the optimum electrode structure was determined: the ratio of 90% resulted in the maximum capacity per active material, 135 mA h g(-1), which is 98% of the theoretical value for LiCoO2. The obtained capacity was substantially larger than the values reported for other cathodes used in all-solid-state lithium batteries. The implication is that at the optimum LiCoO2/Li7La3Zr2O12 ratio, nanoscale three-dimensional conducting paths and an electrochemically effective interface between the active material and the electrolyte are formed as a result of templating by the self-assembled BCP structure.