Hard Carbon Networks for Mitigating Graphite Lattice Strain Under Extreme‑Low‑Temperature Fast Charging

Low-temperature fast charging of lithium-ion batteries is primarily constrained by sluggish reaction kinetics and mechanical degradation of graphite anodes. Here, a kinetic–structural coordination strategy based on a 15 wt.% hard carbon (HC) percolating network embedded within the graphite matrix is proposed. This HC network functions as an ionic flux redistributor, effectively suppressing the high-strain phase transition to stage 1 (LiC₆) and reducing lattice strain, thereby protecting the graphite from mechanical pulverization. Moreover, the coordinated lithiation promotes the formation of a robust, LiF-rich inorganic solid electrolyte interphase (SEI), which facilitates fast desolvation and prevents interfacial delamination. As a result, NCM523‖Graphite/HC pouch cells deliver 2250 cycles at −20°C under a 4C rate with 88% capacity retention, and maintain stable operation at 8C and −40°C. This network doping approach thus provides a scalable design principle for all-climate, high-power batteries intended for electric vehicle applications.