A Slightly Expanded Graphite Anode with High Capacity Enabled By Stable Lithium-Ion/Metal Hybrid Storage.

Abstract

Integrating lithium-ion and metal storage mechanisms to improve the capacity of graphite anode holds the potential to boost the energy density of lithium-ion batteries. However, this approach, typically plating lithium metal onto traditional graphite anodes, faces challenges of safety risks of severe lithium dendrite growth and short circuits due to restricted lithium metal accommodation space and unstable lithium plating in commercial carbonate electrolytes. Herein, a slightly expanded spherical graphite anode is developed with a precisely adjustable expanded structure to accommodate metallic lithium, achieving a well-balanced state of high capacity and stable lithium-ion/metal storage in commercial carbonate electrolytes. This structure also enables fast kinetics of both Li intercalation/de-intercalation and plating/stripping. With a total anode capacity of 1.5 times higher (558mAhg-1) than graphite, the full cell coupled with a high-loading LiNi0.8Co0.1Mn0.1O2 cathode (13mgcm-2) under a low N/P ratio (≈1.15) achieves long-term cycling stability (75% of capacity after 200 cycles, in contrast to the fast battery failure after 50 cycles with spherical graphite anode). Furthermore, the capacity of the full cell also reaches a low capacity decay rate of 0.05% per cycle at 0.2C under the low temperature of -20°C.