Co3S4@Li7P3S11 Hexagonal Platelets as Cathodes with Superior Interfacial Contact for All-Solid-State Lithium Batteries

Poor solid-solid contact between an electrode and solid electrolyte is a great challenge for all-solid-state lithium batteries (ASSLBs) which results in limited ion transport and eventually leads to rapid capacity fading. Two-dimensional (2D) materials have incomparable advantage in the construction of the desired interface because of their flat surface and large specific surface area. In order to realize intimate interfacial contact and superior ion transport, monodisperse 2D Co₃S₄ hexagonal platelets as cathodes for all ASSLBs are synthesized through a series of topological reactions followed with in situ coating of tiny Li₇P₃S₁₁ using a liquid-phase method. The unique 2D hexagonal platelets are favorable for in situ solid electrolyte coating. Moreover, the well-designed interfacial structure can make the electrode materials contact with solid electrolytes more closely, contributing to a remarkable improvement on electrochemical performance. ASSLBs employing the Co₃S₄@Li₇P₃S₁₁ composite platelets as a cathode deliver a large reversible capacity of 685.9 mA h g^-1 at 0.5 A g^-1 for 50 cycles. Even at a high current density of 1 A g^-1, the Co₃S₄@Li₇P₃S₁₁ composite cathode still exhibits a high capacity of 457.3 mA h g^-1 after 100 cycles. This work provides a simple strategy to design the composite electrode with intimate contact and superior ion transport via morphology controlling.