Boosting diffusion kinetics of anode material for fast charging Li-ion batteries

Abstract

Traditional graphite anode material in Li-ion batteries (LIBs) is a primary reason for hampering fast charging LIBs. This is due to its intrinsically sluggish Li⁺- diffusion kinetics and the growth of Li dendrites under fast charging condition. As a result, electric vehicles (EVs) take significantly longer to charge compared to refueling time gasoline vehicles, and the growth of Li dendrites poses a safety hazard. Reforming traditional graphite to a fast charging one opens up new opportunities for faster performing LIBs. We report for the first time a breakthrough in boosting the Li⁺- diffusion kinetics of natural graphite via a fine tuning of surface interlayer expansion to sub-angstrom (Å) level (SE-Gr), utilizing an ethanol-based simple, scalable and inexpensive low-temperature method. The critical benefits of SE-Gr anode material are 2-fold higher diffusion coefficients at stage 1L and deeper charging to stage 3 than traditional natural graphite under fast charging condition of 1C (charged in 1 h). As a result, SE-Gr enables nearly theoretical capacity (375 mAh g⁻¹) under 1C, which is 20-fold faster than 0.05C (charged in 20 h) required for traditional natural graphite, and unprecedented outstanding long cycles of half-cell and full-cell with practically loaded 88 % nickel cathode (active mass of 18 mg cm⁻²) under fast charging conditions of 1 ∼ 5 C (charged in 1 h ∼ 12 min), without Li plating and dendrites. Such performance is impossible to achieve with traditional natural graphite. SE-Gr yields an excellent combination of minute-scale charge speed, high capacity and safety of LIBs, holding promise for next-generation energy storage.