2D Graphene-Like Carbon Coated Solid Electrolyte for Reducing Inhomogeneous Reactions of All-Solid-State Batteries

Recent studies have identified an imbalance between the electronic and ionic conductivities as the drivers of inhomogeneous reactions in composite cathodes, which cause the rapid degradation of all-solid-state battery (ASSB). To mitigate localized overcharge and utilize isolated active materials, the study proposes the coating of an argyrodite-type Li₆PS₅Cl solid electrolyte (SE) with graphene-like carbon (GLC@LPSCl), a 2D conductive material, to offer a continuous three-dimensionally connected electron pathway within the composite cathode to facilitate ion mobility and promote homogeneous reactions. Despite reducing the content of the conducting agent, it is observed that the GLC@LPSCl cell exhibits high initial Coulombic efficiency and discharge capacity, reducing the inhomogeneous reactivity after 200 cycles compared with when ordinary conductive agents are deployed. Additionally, the presence of GLC@LPSCI surface suppresses the interfacial reaction between SE–cathode material, thus imparting the cell with excellent capacity retention (≈90%) after 200 cycles. Furthermore, the cell performance improves even after a fourfold increase in the cathode loading amount, demonstrating the criticality of a well-developed continuous electron pathway to cell performance and highlighting the key role of ensuring a balance between the electron and ion conductivities in the development of high-energy-density and high-power ASSBs.