Cost-effective natural graphite reengineering technology for lithium ion batteries

Graphite tailings produced by natural graphite is usually regarded as garbage to be buried underground, which would result in a certain waste of resources. Here, in order to explore the utilization of natural graphite tailings (NGT), a liquid-polyacrylonitrile (LPAN) is used to modify the NGT fragments and aggregate them together to form secondary graphite particles with low surface area and high tap density. Moreover, the modified NGT show much better electrochemical performances than those of original one. When tested in full cells coupled with NMC532 cathode, the material achieves a high rate capability and cycle stability at the cutoff voltage of 4.25 V as well as 4.45 V, which maintains 84.32% capacity retention after 500 cycles at 1 C rate (4.25 V), higher than that of the pristine one (73.65%). The enhanced performances can be attributed to the use of LPAN to create a unique carbon layer upon graphite tailings to reconstruct surface and repair defects, and also to granulate an isotropic structure of secondary graphite particles, which can help to weaken the anisotropy of Li+ diffusion pathway and form a uniform, complete and stable solid-electrolyte-interface (SEI) on the surface of primary NGT fragments to promote a fast Li+ diffusion and suppress lithium metal dendrites upon charge and discharge.