Non-flammable electrolyte mixtures for high-stability alkali-metal batteries

Background

As the demand for sustainable energy storage solutions grows during the advancement of portable electronics and electric vehicles, there is a pressing need for enhanced energy storage systems. Alkali-metal batteries are a promising solution for energy storage due to their high energy-density capabilities. However, their widescale adoption has been dendrite formation, battery degradation, and safety issues that arise from flammable electrolytes.

One approach to mitigating alkali-metal degradation involves the implementa­tion of localized high concentration electrolytes (LHCE), which are engineered by dissolving an alkali-metal salt in a primary solvent up to the saturation limit. This approach mitigates battery degradation; however, high concentrations of expensive salts and diluents are required. Moreover, this approach does not solve the safety issues associated with a highly flammable electrolyte.

Technology overview

This invention presents a novel electrolyte design for alkali-metal batteries, addressing key challenges associated with electrolyte flammability and alkali-metal stability. The efficacy of this invention was demonstrated in sodium-metal batteries by incorporating sodium nitrate (NaNO₃) salt as a diluent in a trimethyl phosphate (TMP)-based localized high-concentration electrolyte (LHCE). The low concentration of sodium bis(fluorosulfonyl)imide (NaFSI) and NaNO₃ in the electrolyte significantly reduced the amount of expensive salts and fluoroether-based diluents, enhancing the economic feasibility of sodium batteries. The resulting LHCE formed a uniform and inorganic-rich solid electrolyte interphase (SEI) on the anode, improving sodium-metal stability.

Moreover, the TMP-based LHCE enabled Na||Na(Ni_0.3Fe_0.4Mn_0.3)O₂ cells to achieve high Coulombic efficiency (99.3%) and 80% capacity retention over 500 cycles. By utilizing weakly solvating salts as diluents, this invention offers a low-cost, non-flammable solution to enhancing alkali-metal batteries.

Benefits

• Enhanced alkali-metal stability, mitigating dendrite formation and improving battery safety
• Non-flammable and cost-effective electrolyte formulation, reducing the reliance on expensive salts and fluoroether-based diluents
• Improved battery performance as demonstrated by high Coulombic efficiency (99.3%) and 80% capacity retention over 500 cycles in Na||Na(Ni_0.3Fe_0.4Mn_0.3)O₂ cells

Applications

• Lithium/sodium/potassium-ion battery manufacturing

Opportunity

• This cost-effective electrolyte design addresses key challenges in alkali-metal batteries, including electrolyte flammability, dendrite formation, and anode stability.
• Improved alkali-metal battery performance with high Coulombic efficiency (99.3%) and capacity retention (80%) over 500 cycles
• PCT/US2023/029298 (https://patents.google.com/patent/WO2024147801A1/en)
• Available for exclusive license

Publication

“Tuning the solvation structure with salts for stable sodium-metal batteries” (https://doi.org/10.1038/s41560-024-01469-y)