Spatio-temporal evolution of bimetallic anode with stress-relaxation effect in sodium storage under ambient and cryogenic temperature

Abstract

The sluggish diffusion kinetics and limited capacity of individual Bi or Sb restrict their application in sodium-ion batteries (SIBs). While Binary alloy systems featuring flexible tunability are compatible with high-stability/capacity characteristics, exhibiting promising potential as anode. Herein, a series of composites Bi_xSb_1-x@C (x = 0.1, 0.3, 0.5, 0.7, 0.9) are constructed by regulating the introduction of Sb salts in Bi-MOF precursor, where Bi_0.5Sb_0.5 with the optimal Na⁺ adsorption/diffusion properties. Moreover, through sophisticated finite element simulations, the unique “stress-relaxation effect” in the BiSb system, significantly dissipating the accumulation of internal stresses and effectively attenuating the structural strain from Na⁺ insertion, is unveiled. Besides, exhaustive explorations targeting the spatio-temporal evolution mechanism uncover that the optimized stabilized structure efficiently promotes electron and Na⁺ transfer dynamics, obviates alloy crushing, and simultaneously synergize interactions with the ester- and ether-based electrolytes to form robust solid-electrolyte interphase (SEI), which enables the Bi_0.5Sb_0.5@C electrode with superior kinetics and ultra-stable cycling capability at ambient and cryogenic temperature. The first exploration of the low-temperature properties of BiSb alloy in this study not only enriches the application prospects of the binary alloy system but also offers instructive implications for the exploration of alloy-type anode in subsequent extreme conditions.