Developmet of a design protocol for a ultrafast-charging, non-flammable electrolyte in lithium ion batteries.

Research Summary

The electrolyte design protocol required to overcome safety problems such as ignition and explosion of existing liquid electrolytes and to develop a new flame-retardant electrolyte capable of ultra-fast charging is presented through Nuclear Magnetic Resonance spectroscopy.

Upon introducing new non-flammable electrolyte (called WNLE), more than ten times increase in charging rate compared to the conventional electrolytes was observed. This improvement was elucidated through Nuclear Magnetic Resonance (NMR) spectroscopy, which analyzed the binding strength between the electrolyte and lithium ions, as well as the structure of the solvent molecules surrounding the lithium ions.

The WNLE exhibits lower viscosity and higher lithium ion diffusion coefficient and transference numbers compared to commercial electrolytes. This results in faster lithium ion diffusion and quicker insertion of lithium ion from the solvent into the anode. Consequently, this mitigates dendrite growth, forming a stable solid-electrolyte interphase (SEI), and ensures both rapid charging within 20 minutes and long-term high capacity retention.

Expected Outcomes

By developing a new method to elucidate the fast lithium ion transport and solvation structure of liquid electrolytes, this research provides important guidelines for the design of future liquid electrolytes.

Related Figures

[Figure 1] (top) Discharge capacity as a function of cycle number for the WNLE and commercial electrolyte(bottom) Flammability test result of WNLE

[Figure 2] (left) Comparison of diffusion coefficients and transference number between WNLE and commercial electrolyte(right) The changes in ¹⁷O NMR chemical shifts for both carbonyl and ethereal oxygen of each solvent molecules as a function of solvent ratio