Li Tong, Cao Yun, Song Qiuchen, Peng Linkai, Qin Xianying, Lv Wei, Kang Feiyu
Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China.
Shenzhen Graphene Innovation Center Co. Ltd, Shenzhen, 518107, China.
Small. 2024 Oct;20(40):e2403057. doi: 10.1002/smll.202403057. Epub 2024 May 28.
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 (558 mAh g) than graphite, the full cell coupled with a high-loading LiNiCoMnO cathode (13 mg cm) 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 0.2 C under the low temperature of -20 °C.
整合锂离子和金属存储机制以提高石墨负极的容量，有望提升锂离子电池的能量密度。然而，这种方法通常是将锂金属电镀到传统石墨负极上，由于商业碳酸盐电解质中锂金属容纳空间受限以及锂电镀不稳定，面临着严重锂枝晶生长和短路等安全风险挑战。在此，开发了一种具有精确可调膨胀结构的微膨胀球形石墨负极，以容纳金属锂，在商业碳酸盐电解质中实现了高容量与稳定的锂离子/金属存储之间的良好平衡状态。这种结构还能实现锂嵌入/脱嵌以及电镀/剥离的快速动力学。与石墨相比，负极总容量高出1.5倍（558 mAh g），与高负载LiNiCoMnO正极（13 mg cm）耦合的全电池在低N/P比（≈1.15）下实现了长期循环稳定性（200次循环后容量保持75%，而球形石墨负极的电池在50次循环后迅速失效）。此外，在-20°C的低温下，全电池在0.2 C时的容量衰减率也低至每循环0.05%。
