Researchers at the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences, along with collaborators from leading international institutions, have introduced an innovative cathode homogenization strategy for all-solid-state lithium batteries (ASLBs).

This new approach, detailed in apaper in Nature Energy, significantly improves the cycle life and energy density of ASLBs, representing an important advancement in energy storage technology.

Schematic illustration of cathode microstructure evolution during charging. (a) Conventional heterogeneous composite cathode and (b) the proposed homogeneous cathode with efficient mixed conduction. (Image by QIBEBT)

Current ASLBs face challenges due to heterogeneous composite cathodes, which require electrochemically inactive additives to enhance conduction. These additives, while necessary, reduce the batteries’ energy density and cycle life due to their incompatibility with the layered oxide cathodes, which undergo substantial volume changes during operation.

The researchers developed a solution: a cathode homogenization strategy utilizing a zero-strain material, Li_1.75Ti₂(Ge_0.25P_0.75S_3.8Se_0.2)₃ (LTG_0.25PSSe_0.2). This material exhibits excellent mixed ionic and electronic conductivity, ensuring efficient charge transport throughout the (dis)charge process without the need for additional conductive additives.

The LTG_0.25PSSe_0.2 material shows impressive performance metrics, including a specific capacity of 250 mAh g^–1 and minimal volume change of just 1.2%. A homogeneous cathode made entirely of LTG_0.25PSSe_0.2 enables room-temperature ASLBs to achieve more than 20,000 cycles of stable operation and a high energy density of 390 Wh kg⁻¹ at the cell level.

Our cathode homogenization strategy challenges the conventional heterogeneous cathode design. By eliminating the need for inactive additives, we enhance energy density and extend the battery’s cycle life.

—Dr. CUI Longfei, co-first author of the study from Solid Energy System Technology Center (SERGY) at QIBEBT

The material’s stability and performance metrics are impressive, making it a strong candidate for commercial applications in electric vehicles and large-scale energy storage systems.

—Prof. JU jiangwei, co-corresponding author of the study from SERGY

This advancement is supported by extensive testing and theoretical calculations. These analyses confirm the electrochemical and mechanical stability of the homogeneous cathodes, showing no adverse chemical reactions or significant resistance increases after prolonged cycling.

Beyond ASLBs, other battery types, including solid-state sodium batteries, lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and fuel cells, also face challenges with heterogeneous electrodes. These systems often suffer from mechanochemical and electrochemical incompatibilities, creating significant bottlenecks and degrading overall battery performance.

By addressing key challenges in ASLBs, this strategy sets a foundation for future innovations in energy storage technology. The team plans to further explore the scalability of the LTG_0.25PSSe_0.2 material and its integration into practical battery systems.