Three-Dimensional Bicontinuous Nanocomposite from a Self Assembled Block Copolymer for a High-Capacity All-Solid-State Lithium Battery Cathode

Safe secondary batteries with high energy densities and high power densities will be necessary if pure-electric and hybrid vehicles are to become more widespread, and all -solid-state lithium-ion batteries (LiBs) are among the most promising options. Much research has focused on the development of cathode materials with solid Li electrolytes, including composites fabricated from calcined microparticles, laser-deposited film systems, and materials with three-dimensional structures. However, because utilization of a high percentage of the active cathode material requires an electrode with a high electrolyte content, achieving high active-material-utilization rates in electrodes with high active-material contents (and thus relatively low electrolyte contents) has been challenging. Herein, we describe the self-assembled block copolymer-templated synthesis of a three-dimensional bicontinuous nanocomposite electrode material consisting of LiCoO2 as the active cathode material and Li7La3Zr2O12 as the solid Li electrolyte for use in all -solid-state LiBs. In this nanocomposite, 98% of the active material was utilized even though the active-material content was high (89.4%). These percentages are substantially larger than those reported for other cathodes in all -solid-state. The excellent electrochemical properties of the nanocomposite can be ascribed to its unique bicontinuous nanostructure consisting of the active cathode material and the Li electrolyte interspersed on a scale of several tens of nanometers, which is 2 orders of magnitude smaller than the scale reported in previous studies. The process we used to prepare the nanocomposite is expected to be versatile for producing other highly functional devices, such as quantum dot solar cells, thermoelectric devices, and solid oxide fuel cells.