Functionalized Electrode Additive for Simultaneously Reinforcing Chemo-Mechanical Properties of Millimeter-Thick Dry-Electrode for High-Energy All-Solid-State Batteries

Voids are widely disseminated in a powder when mixed, and hence the typical dry-electrode preparation method yields a sparse dry-electrode because the external pressure applied to the surface of the mixed powder is not evenly distributed. Consequently, particle cracking and void remnants appear in the electrode after calendaring. This study introduces a practically applicable bi-functionalized electrode additive to simultaneously reinforce the chemo-mechanical properties of millimeter-thick dry electrodes. The agyrodite Li₆PS₅Cl solid electrolyte and lithium difluorophosphate (LiPO₂F₂) additive have different sizes, as demonstrated by their densification from their elaborate bimodal structure, which is densely packed. Because the additive is filled into the interparticle voids in the electrode sheet during electrode fabrication, a decrease in electrode cracking after calendaring is possible because of the uniform distribution of external pressure. Hence, a thin, highly ionic/electronic-conductive electrode can be constructed by the addition of LiPO₂F₂ additive. Furthermore, during the formation, the active material surface-contacted LiPO₂F₂ promptly produces a surface layer comprising LiF and Li_xPF_y. Thus, the addition of LiPO₂F₂ further reduces the degradation of Li₆PS₅Cl solid electrolytes. As a result, the LiPO₂F₂ additive simultaneously improves the electrochemical and physicochemical properties of millimeter-thick dry-electrodes for high-energy all-solid-state battery systems.