A medium/low concentration localized electrolyte for safe and fast-charging lithium-ion batteries

Localized high concentrations electrolyte (LHCE) has garnered significant attention as an emerging electrolyte candidate for Li-metal batteries. LHCE is formed by diluting a high concentration electrolyte (usually close to saturation) with a non-solvating solvent that has a low donor number. We propose a modified concept of LHCE, called "localized electrolyte (LE)," optimized for Li-ion batteries with a graphite anode and Ni-rich cathode. In LE, the Li salt concentration is optimized to be only 1-2 M in solvating solvents, resulting in an overall concentration of 0.5-1 M, which reduces cost and supports fast ion transport. The non-flammable LE also has excellent wettability, which facilitates fasting charging. We also demonstrated that with the addition of 2 wt.% vinylene carbonate into 0.7 M LE, the Li-ion cell retains 80.3% of its initial capacity after 700 cycles of testing in about 4 months. Overall, LE represents a promising and cost-effective solution for improving the performance and safety of Li-ion batteries.