Solid-state batteries (SSBs) have emerged as a promising alternative to conventional liquid electrolyte batteries due to their potential for higher energy density and improved safety. However, achieving high performance in SSBs is difficult because of inadequate contact and interfacial reactions that generate high interfacial resistance, as well as inadequate solid-solid contact between electrodes. These chronic issues are associated with inhomogeneous ion and electron transport networks owing to imperfect solid-solid interfacial contact. This study developed an optimal interfacial engineering strategy to facilitate an ion-electron transport network by designing an active material (NCM622) uniformly filled with a thin layer of a solid electrolyte (garnet-type Li6.25Ga0.25La3Zr2O12) and conductive additives. The optimal composite electrode architecture enhanced the high capacity, high rate capability, and long-term cycle stability, even at room temperature, owing to the percolating network for facile ionic conduction that assured a homogeneous reaction. In addition to mitigating the mechanical degradation of the cathode electrode, it also reduced the crosstalk effects on the anode-solid electrolyte interface. Effectively optimizing the selection and use of conductive additives in composite electrodes offers a promising approach to addressing key performance-limiting factors in SSBs, including interfacial resistance and solid-solid contact issues. This study underscores the critical importance of cathode architecture design for achieving high-performance SSBs by ensuring that the interfaces are intact with solid electrolytes at both the cathode and anode interfaces while promoting uniform reactions. This study provides valuable insights into the development of SSBs with improved performance, which could have significant implications for a wide range of applications.
Keywords: carbon additive; composite cathode; composite solid electrolyte; ion- and electron-network; solid-state battery.