By replacing the inert, strongly positive electrostatic potential of TTE with the active, weakly positive electrostatic potential of MDFSA, thermally resistant interfacial films are formed, enhancing the battery's performance at high temperatures.

Graphite films with large grain sizes have been reportedly obtained by using metal as catalysts, but the obtained graphite is mostly heavily wrinkled, thus containing defects that degrade its properties. We report the synthesis of mirror-like and large-grained graphite films with only a few nano kinks and controllable dimensions, achieved by using flat Ni-Mo alloy melts of the same lateral dimensions as the metal foils used to make this alloy melt. The graphite film exhibited few nano kinks and a mirror-like appearance because the deliberate evaporation of much of the Ni produced a porous substrate, which in turn dramatically weakened the substrate-graphite film interaction before cooling. The mirror-like graphite appears to be 100% AB-stacked with millimeter-sized grains that are much larger than the multi-micron grain size of highly oriented pyrolytic graphite and rivaled in size only by a small percentage of natural graphite. Our graphite films have an electrical conductivity of 2.25 × 10⁴ S cm⁻¹ at 300 K. Tensile loading of macroscale samples showed an average Young’s modulus of 969 ± 69 GPa and average fracture strength of 1.29 ± 0.203 GPa, and Frequency Domain Thermoreflectance revealed an average in-plane thermal conductivity of 2034.4 ± 68 W m⁻¹·K⁻¹.

Flame‐retardant phosphate‐based electrolytes effectively enhance lithium‐ion battery safety but suffer from poor compatibility with graphite anodes and high‐voltage cathodes, hindering scalability. Fluorinated phosphates, though widely used, increase interfacial resistance at the anode, degrading performance. In this work, carbonate solvents with strong polarity are introduced to prevent tris(2,2,2‐trifluoroethyl) phosphate (TFEP) from participating in the solvation structure of lithium ions. This strategy forms a quasi‐localized high‐concentration solvation structure, thereby restricting the reduction of TFEP and its impact on the graphite anode. The LiNi _0.8 Mn _0.1 Co _0.1 O ₂ (NCM811) | Graphite (Gr) pouch cell with optimized electrolyte exhibits a capacity retention rate of 80.1% after 370 cycles at 0.5C, which is much more stable than the electrolyte with TFEP‐involved solvation structure (capacity retention rate: 47.1% after 300 cycles). The corresponding pouch cell with cut‐off voltage to 4.5 V exhibits a capacity retention rate of 82.8% after 125 cycles, significantly outperforming cells employing commercial carbonate electrolytes (capacity retention rate: 56.9% after 125 cycles). Thus, the developed quasi‐localized high‐concentration solvation structure can effectively stabilize the electrode interface, greatly enhancing the cycling performance of phosphate‐based flame‐retardant electrolytes.