Local Thermal Strain Regulated Solid Electrolyte Interphase with Advanced High-Temperature Tolerance

The structure instability of solid electrolyte interphase (SEI) on hard carbon (HC) anode, further worsening under high-temperature cycling, severely hinders the application of sodium-ion battery (SIB). Herein, we introduced locally negative thermal strain to catalyze SEI formation and improve its structure durability during high-temperature cycling, through using negative thermal expansion (NTE) oxide ZrW₂O₈. Both interfacial Na⁺ transfer and initial Coulombic efficiency (ICE) were enhanced significantly at 0-80 °C. Specifically, NTE ZrW₂O₈ with the mitigation effect on thermal strain, imparts self-relieving functionality with mechanical elasticity into internal inorganic layer, synergistically improving the temperature tolerance and mechanics stability of the SEI. The optimized HC with 93.3% ICE sustained working over 8000 cycles at 5.0 A g^-1, even maintained remarkable capacity retentions of 86.3% at 60 °C (226.7 mA h g^-1 at 2.0 A g^-1 after 420 cycles) and 63.4% at 80 °C (241.4 mA h g^-1 at 1.0 A g^-1 after 250 cycles). The capacity retention ratio of full battery at 60 °C was improved from 22.8% to 64.0%. It is believed that this novel thermal strain modulation of SEI will hold great promise for the design of stable SIB under extreme conditions.