Identifying lithium fluorides for promising solid-state electrolyte and coating material of high-voltage cathode

Effective Li3AlF6 Surface Coating for High-Voltage Lithium-Ion Battery Operation

“…75% at the 100th cycle, the Li 3 AlF 6 coating effectively improves the cyclability in high-voltage operations. Note that the reversible voltage limit of Li 3 AlF 6 @LCO (4.5 V) is lower than that of Li 3 AlF 6 @LNMO (5.0 V), likely owing to the lower stability of Li 3 AlF 6 at the LCO surface …”

“…Note that the reversible voltage limit of Li 3 AlF 6 @LCO (4.5 V) is lower than that of Li 3 AlF 6 @LNMO (5.0 V), likely owing to the lower stability of Li 3 AlF 6 at the LCO surface. 7 ■ CONCLUSIONS Crystalline Li 3 AlF 6 was successfully coated onto Li-Ni 0.5 Mn 1.5 O 4 and LiCoO 2 electrodes by a simple sol−gel calcination process. The cycle performances were significantly enhanced by suppressing the side reaction at the CEI.…”

“…This can be mitigated through the surface modification of the cathodes. , The surfactant materials used for this purpose must have a wide electrochemical window and high Li + -ion conductivity and be inert to the cathode material. Recent high-throughput calculation studies − suggest that ternary lithium fluorides, such as LiMF 4 , Li 2 MF 6 , and Li 3 MF 6 (M: typical metal element), can satisfy these requirements. − In particular, β-Li 3 AlF 6 has a high anodic limit of 6.48 V and sufficient stability against various cathode materials. β-Li 3 AlF 6 synthesized by a mechanochemical process has a sufficient Li + -ion conductivity of 3.9 × 10 –6 S cm –1 and can be applied as a solid-state electrolyte. , However, to the best of our knowledge, β-Li 3 AlF 6 has not yet been applied as a high-voltage cathode coating material.…”

“…β-Li 3 AlF 6 synthesized by a mechanochemical process has a sufficient Li + -ion conductivity of 3.9 × 10 –6 S cm –1 and can be applied as a solid-state electrolyte. , However, to the best of our knowledge, β-Li 3 AlF 6 has not yet been applied as a high-voltage cathode coating material. The abovementioned theoretical studies − suggest that among various ternary lithium fluorides, β-Li 3 AlF 6 is more suitable than a solid-state electrolyte for use as a coating material owing to its much higher anodic stability, thermal stability at the cathode interface, and slightly lower Li + -ion conductivity. As an alternative, an amorphous LiAlF 4 thin film has been used as a cathode coating material. − Although LiAlF 4 -coated cathodes exhibit good cathode performance under high-voltage operation, a theoretical study suggests that β-Li 3 AlF 6 is much more suitable than LiAlF 4 as a coating material because of its lower migration barrier ( E = 0.25 eV for Li 3 AlF 6 , E = 0.41 eV for LiAlF 4 ) and phase stability (β-Li 3 AlF 6 is a crystalline phase, LiAlF 4 is an amorphous phase) …”

Solvent-free and long-cycling garnet-based lithium-metal batteries

“…However, current SSLMBs have not achieved the performance goals of energy density up to 500 Wh kg − 1 and cycling life over 1000 cycles with the retention of 80% at the cell level 7,8 . Extensively explored inorganic solid electrolytes (ISEs), such as oxide 9,10 , sul de 11,12 and halide 13,14 have achieved great progress in ionic conductivity, ame retardancy and ionic transference number but still suffer from the unsatisfactory electrochemical performance, predominantly owing to high impedances at various solid-solid interfaces in SSLMBs related to chemical incompatibility, electrochemical instability and mechanical failure 15,16 . For garnet-type oxide electrolytes, although thermodynamic stability at interfaces is maintained relatively, the physical contact with electrodes limits the practical application, which is much more serious in the cathode side, arising from the rigid particles of cathode composites with a variety of interfaces [17][18][19] .…”