Using a solid-state electrolyte (SE), all-solid-state batteries could provide improved safety and higher energy density than conventional Li-ion batteries. In this regard, it is important to develop a SE with superior ionic conductivity and chemical compatibility with electrode materials. Li6PS5Cl is a promising SE that features high ionic conductivity up to 10–3 S cm–1 at room temperature, owing to the anion site disorder and high polarizability of sulfur. However, the chemical instability of Li6PS5Cl during cycling limited the implementation in practical usages. This study employed graphene fluoride (GF) as a conductive agent for the cathode composite to improve the phase stability of Li6PS5Cl. GF was fabricated using a facile microwave-induced exfoliation method. By mixing Li6PS5Cl with GF rather than conventional Super P carbon black (CB), we observed significant improvements in the chemical stability of Li6PS5Cl. From X-ray photoelectron spectroscopy, it showed the diminished phase decomposition of Li6PS5Cl. In addition, LiF was detected, attributing to the interfacial reactions between GF and Li6PS5Cl. This LiF-enriched protective layer could be the reason for preventing the phase decomposition of Li6PS5Cl. Furthermore, we conducted cyclic voltammetry and galvanostatic measurements by fabricating a LiCoO2 composite containing GF/Li6PS5Cl composite. The cyclic voltammetry results revealed that GF contributes to a reversible redox profile with a low anodic current. During the galvanostatic measurements, GF containing cathode displayed an improved capacity and high Coulombic efficiency. Our results show that GF is a promising candidate for conductive agents in all-solid-state batteries, which function as the electron pathway and an interfacial stabilizer to improve the chemical stability of Li6PS5Cl, resulting in substantially improved electrochemical performance.

Employing graphene fluoride as a conductive agent in all-solid-state batteries

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