Research on the High-Rate Capability of Li/Na Dual-Salt Electrolyte Battery with Polyanthraquinonyl Sulfide Cathode

Lithium-ion batteries (LIB) are used in electronic devices and electric vehicles. However, inorganic materials currently such as LiFePO₄ show shortcomings in high-rate capabilities. Organic materials are studied due to their flexibility; despite better rate performance than inorganic, they cannot meet the high demands of storage devices. This work utilizes Na⁺ as cocation additives to form a dual-salt electrolyte with Li salt, aiming to enhance the high-rate performance of organic materials. By preferentially reducing Na⁺ clusters, a Li/Na inorganic salt interface is formed, which effectively lowers the desolvation energy of Li⁺ from 0.259 to 0.239 eV and increases the diffusion rate from 0.73 × 10^-9 to 1.39 × 10^-9 cm²·s^-1. The Li||PAQS battery can achieve a capacity of 119.6 mAh·g^-1 at 20 C while the capacity with a single-Li salt electrolyte is only 34.4 mAh·g^-1. Experiments show that the codeposition of Li⁺/Na⁺ on the anode forms a dense Li/Na inorganic solid electrolyte interphase (SEI), which enables to exhibit a discharge capacity retention rate of 71.97% after 5000 cycles at 5 C, whereas battery with Li salt is only 11.73%. Therefore, a dual-salt electrolyte instead of Li salt in organic materials can effectively enhance the cycling stability and high-rate performance of LIB.