Unlocking the Potential of Li-Rich Mn-Based Oxides: Surpassing 300 mAh g−1 at Room Temperature in All-Solid-State Batteries

This study presents a comprehensive assessment of the temperature-dependent electrochemical performance of LiNbO₃-coated lithium-rich manganese-based oxide (LRMO) cathodes in all-solid-state batteries (ASSBs). The effects of temperature and activation on the performance of LRMO cathodes are systematically investigated through electrochemical characterization and X-ray diffraction and X-ray absorption near-edge structure analyses. LRMO activation significantly improves electronic conductivity by facilitating lithium intercalation within the sulfide-based solid electrolyte (SE). This conductivity enhancement reduces cell resistance more effectively than an elevation in temperature alone. Because of the low conductivity of LRMO at room temperature (≈10⁻⁶ S cm⁻¹), improving the composite cathode's conductivity is critical for reducing cell resistance and enabling LRMO activation. Two strategies are proposed to achieve this: the addition of carbon additives to enhance the electronic conductivity and the application of a LiNbO₃ coating to stabilize the interface between the cathode active material and the SE, thereby minimizing resistance. With these improvements, LiNbO₃-coated LRMO cathodes with conductive additives achieve a high discharge capacity of over 300 mAh g⁻¹ after 30 cycles at 25 °C. These findings provide valuable insights into optimizing next-generation LRMO-based cathodes and advancing high-performance energy storage systems for ASSBs.