Tailoring the electronic conductivity of high-loading cathode electrodes for practical sulfide-based all-solid-state batteries

Sulfide-based all-solid-state batteries (ASSBs) exhibit unparalleled application value due to the high ionic conductivity and good processability of sulfide solid electrolytes (SSEs). Carbon-based conductive agents (CAs) are often used in the construction of electronic conductive networks to achieve rapid electron transfer. However, CAs accelerate the formation of decomposition products of SSEs, and their effects on sulfide-based ASSBs are not fully understood. Herein, the effect of CAs (super P, vaper-grown carbon fibers, and carbon nanotubes) on the performance of sulfide-based ASSBs is investigated under different cathode active materials mass loading (8 and 25 ​mg·cm⁻²). The results show that under low mass loading, the side reaction between the CAs and the SSEs deteriorates the performance of the cell, while the charge transfer promotion caused by the addition of CAs is only manifested under high mass loading. Furthermore, the gradient design strategy (enrichment of CAs near the current collector side and depletion of CAs near the electrolyte side) is applied to maximize the benefits of CAs in electron transport and reduce the adverse effects of CAs. The charge carrier transport barrier inside the high mass loading electrode is significantly reduced through the regulation of electronic conductivity. Consequently, the optimized electrode achieves a high areal capacity of 5.6 ​mAh·cm⁻² at high current density (1.25 ​mA·cm⁻², 0.2 ​C) at 25 °C with a capacity retention of 87.85% after 100 cycles. This work provides a promising way for the design of high-mass loading electrodes with practical application value.