Gong Haiqiang, Du Peng, Zhang Bao, Xiao Zhiming, Ming Lei, Ou Xing
National Energy Metal Resources and New Materials Key Laboratory, School of Metallurgy and Environment, Central South University, Changsha 410083, PR China.
National Energy Metal Resources and New Materials Key Laboratory, School of Metallurgy and Environment, Central South University, Changsha 410083, PR China.
J Colloid Interface Sci. 2025 Jan 15;678(Pt C):472-481. doi: 10.1016/j.jcis.2024.09.146. Epub 2024 Sep 16.
Due to the inherent characteristics of traditional graphite anode material, its lithium diffusion kinetic is significantly constrained, easily leading to a noticeable capacity degradation during rapid charge/discharge cycling. Although modifying the graphite by mixing the hard carbon can effectively enhance its fast-charging performance, yet the underlying mechanism of improvement effect and structure design of interface are still needed to further investigate. To address this research gap, hard carbon-coated graphite (HCCG) material has been designed and synthesized through simple interface engineering, which is aimed to explore and elucidate the optimization mechanisms on fast-charging performance from the graphite interface perspective. According to the electrochemical calculations, the HCCG anode exhibits significant enhancements. Specially, its reversible lithium content is increased by approximately 8 % at various states of charge, its exchange current density is tripled, and its Tafel slope is reduced to one-quarter of the original graphite. Therefore, the HCCG maintains an impressive 86.89 % capacity retention and a high capacity of 202.3 mAh g after 1450 cycles at ultrahigh rate of 5C. These improvements indicate a substantial reduction in electrode polarization during fast charging, which is ascribed to the abundant lithium intercalation pathways and accommodation space provided by the intimate hard carbon coating layer. Moreover, as a "buffer layer," hard carbon coating can accommodate considerable amount of lithium deposited on the graphite surface, effectively mitigating the capacity loss caused by lithium deposition and maintaining effective electrochemical contact without delamination. This comprehensive analysis of hard carbon coating illustrates the improvement mechanism of fast-charging performance, which can offer valuable insights into the dynamic and structural optimization of graphite anode interfaces.
由于传统石墨负极材料的固有特性，其锂扩散动力学受到显著限制，在快速充放电循环过程中容易导致明显的容量衰减。虽然通过混合硬碳对石墨进行改性可以有效提高其快充性能，但改善效果的潜在机制和界面结构设计仍需进一步研究。为了填补这一研究空白，通过简单的界面工程设计并合成了硬碳包覆石墨（HCCG）材料，旨在从石墨界面角度探索和阐明快充性能的优化机制。根据电化学计算，HCCG负极表现出显著的增强。特别是，在各种充电状态下，其可逆锂含量增加了约8%，交换电流密度增加了两倍，塔菲尔斜率降低到原始石墨的四分之一。因此，在5C的超高倍率下经过1450次循环后，HCCG仍保持86.89%的令人印象深刻的容量保持率和202.3 mAh g的高容量。这些改进表明在快速充电过程中电极极化大幅降低，这归因于致密的硬碳涂层提供了丰富的锂嵌入途径和容纳空间。此外，作为“缓冲层”，硬碳涂层可以容纳大量沉积在石墨表面的锂，有效减轻锂沉积导致的容量损失，并保持有效的电化学接触而不分层。对硬碳涂层的这种综合分析阐明了快充性能的改善机制，可为石墨负极界面的动力学和结构优化提供有价值的见解。
