Spherical nano-graphite anode derived from electrochemical stripping for high performance Li-ion capacitors

Developing graphite-based carbon materials with nano-size, stable morphology, enhanced interlayer spacing, outstanding conductivity as well as superior dispersibility are greatly challenge for obtaining low charge platform, high fast-charge capacity and excellent cycling performance of lithium-ion capacitors (LICs). Herein, we employed electrochemical stripping method to prepare spherical nano-graphite (SNG) endowing with large interlayer spacing, high conductivity and stable morphology. SNG anode exhibits excellent rate performance (313 and 175 mA h g−1 at 0.1 and 1 A/g), high fast-charge capacity (119 mA h g−1 at 4 A/g) and ultralong cyclic stability for 3000 cycles (83.6% capacity retention). Additionally, the assembled asymmetric LICs using SNG as anode and porous carbon as cathode shows maximum gravimetric energy density of 399 W h kg−1 and maximum volumetric energy density of 383 W h L−1 coupled with excellent capacity retention rate of 90.6% at 8 A/g for 6000 cycles. Furthermore, the theoretical calculation models for carbon materials with different interlayer spacing (0.334–0.37 nm) are constructed to demonstrate that the enhanced Li-ion storage capability is closely related to interlayer spacing. Thus, this material provides great potential application in LICs and other practical energy storage system.