Abstract:

Chromium oxide (Cr₈O₂₁) primary battery has become a research hotspot in the field of aerospace and military because of its high energy density and high working voltage. However, the application of primary batteries in extreme conditions is limited by the inherent contradiction between high current discharge capacity and high temperature storage life, but the traditional electrolyte is difficult to achieve synchronous optimization of the two. In view of this contradiction, this study proposed a multi-component electrolyte collaborative design strategy: through the high dielectric constant EC (ethylene carbonate) and low viscosity EMC (methyl ethyl carbonate) composite solvent to optimize the lithium salt dissociation and ion migration efficiency, combined with the same high boiling point PC (propylene carbonate) to improve the thermal stability of the electrolyte, and combined with LiPF₆ (lithium hexafluorophosphate) and LiBOB (lithium oxalate borate) double salt system to control the solvation structure and construct a stable SEI film containing LiF and B-O components. The design takes into account high ionic conductivity, low desolvation energy barrier, high thermal decomposition temperature and interface passivation ability, breaking through the functional limitations of a single component. The experimental results show that the specific discharge capacity of Cr₈O₂₁||Li primary battery at 5C rate is 1.53 times that of commercial electrolyte [LiBF₄ (lithium tetrafluoroborate) - PC+DME (ethylene glycol dimethyl ether)]. At the same time, the high temperature storage life at 60℃ is more than 5 times longer than that of commercial storage, and the capacity retention rate reaches 89% after 720 hours of storage at 60℃. This study provides a new paradigm of electrolyte design and interface control for the development of high reliability primary batteries in extreme environments through the multi-component electrolyte strategy, which has important engineering value for the application of spacecraft power system and other special scenarios.

Key words: Cr₈O₂₁, Primary battery, High current discharge, High temperature storage life, synergistic effect