Characterization of graphite etched with potassium hydroxide and its application in fast-rechargeable lithium ion batteries

Surface-modified graphite for application as an anode material in lithium ion batteries was obtained by etching with KOH under mild conditions without high-temperature annealing. The surface of the etched graphite is covered with many nano-sized pores that act as entrances for lithium ions during the charging process. As compared with pristine graphite and other references such as pitch-coated or etched graphite samples with annealing, our non-annealed etched graphite exhibits excellent electrochemical properties, particularly at fast charging rates of over 2.5 C. While avoidance of the trade-off between increase of irreversible capacity and good rate capability has previously been a main concern in highly porous carbonaceous materials, we show that the slightly larger surface area created by the etching does not induce a significant increase of irreversible capacity. This study shows that it is important to limit the size of pores to the nanometer scale for excellent battery performance, which is possible by etching under relatively mild conditions. [Display omitted] •The surface modified graphite for lithium battery is prepared by etching with KOH.•The size of holes on the surface is a key factor to improve the battery performances.•Nano-sized holes on the graphite surface act as lithium ion entrances during cycling.•Etched holes on the graphite surface penetrate to a depth of 40 nm.