Abstract:

The chromium oxide (Cr₈O₂₁) primary battery has emerged as a research hotspot in aerospace and military applications owing to its high energy density and high operating voltage. However, its use under extreme conditions is constrained by the inherent trade-off between high current discharge capacity and high-temperature storage life, which conventional electrolytes cannot simultaneously optimize. To address this issue, a multi-component electrolyte design strategy was proposed. A mixed solvent of ethylene carbonate (EC, high dielectric constant) and methyl ethyl carbonate (EMC, low viscosity) was employed to enhance lithium-salt dissociation and ion migration efficiency. Propylene carbonate (PC, high boiling point) was incorporated to improve electrolyte thermal stability, while a dual-salt system of lithium hexafluorophosphate (LiPF₆) and lithium bis(oxalato)borate (LiBOB) was used to regulate solvation structure and form a stable solid electrolyte interphase (SEI) film enriched with LiF and B—O species. This strategy ensures high ionic conductivity, a low desolvation energy barrier, elevated thermal decomposition temperature, and strong interfacial passivation, thereby overcoming the functional limitations of single-component electrolytes. Experimental results demonstrate that the specific discharge capacity of the Cr₈O₂₁||Li primary battery at a 5 C rate is 1.53 times higher than that with a commercial electrolyte of lithium tetrafluoroborate (LiBF₄) in PC + ethylene glycol dimethyl ether (DME). Moreover, the high-temperature storage life at 60 ℃ is extended more than fivefold, with a capacity retention of 89% after 720 h. This work establishes a new paradigm for electrolyte design and interface control in high-reliability primary batteries for extreme environments, offering significant engineering value for spacecraft power systems and other specialized applications.

Key words: Cr₈O₂₁, primary battery, high current discharge, high-temperature storage life, synergistic effect