储能科学与技术 ›› 2024, Vol. 13 ›› Issue (1): 325-332.doi: 10.19799/j.cnki.2095-4239.2023.0746

• 储能材料与器件 • 上一篇    下一篇

中空三维结构的硅碳负极的构筑及性能研究

郝胐(), 王俊明, 董春伟, 尉琳琳, 董阳, 梁文斌, 苏志江()   

  1. 北京低碳清洁能源研究院，北京 102211
  • 收稿日期:2023-10-24 修回日期:2023-11-10 出版日期:2024-01-05 发布日期:2024-01-22
  • 通讯作者: 苏志江 E-mail:20071227@chnenergy.com.cn;20036107@chnenergy.com.cn
  • 作者简介:郝胐（1982—），男，博士，工程师，研究方向为锂电硅碳负极、人造石墨负极，E-mail：20071227@chnenergy.com.cn；

Preparation and research of three-dimensional silicon carbon anodes with a hollow structure

Fei HAO(), Junming WANG, Chunwei DONG, Linlin WEI, Yang DONG, Zhijiang SU, Wenbing LIANG()   

  1. National Institute of Clean-and-Low-Carbon Energy, Beijing 102211, China
  • Received:2023-10-24 Revised:2023-11-10 Online:2024-01-05 Published:2024-01-22
  • Contact: Wenbing LIANG E-mail:20071227@chnenergy.com.cn;20036107@chnenergy.com.cn

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摘要：

硅碳材料作为高能量密度的锂电负极材料备受瞩目，但由于硅在充放电过程中巨大的体积膨胀效应，导致了其循环性能差，限制了其商业化应用。本工作利用薄层石墨柔性结构的特点，与纳米硅进行复合制备了中空结构的硅碳复合物，并通过对薄层石墨和纳米硅分别用含有羧基的羧甲基纤维素（CMC）和含有氨基的正硅酸乙酯（TEOS）进行表面修饰。相比于传统的机械混合工艺制备的硅碳负极材料存在纳米硅与碳材料复合不均一的问题，本工作修饰后的纳米硅与薄层石墨之间通过静电自组装作用，可形成更为均一的纳米硅与薄层石墨的复合物（S/MG）。通过造粒技术，构筑了由纳米硅/薄层石墨片层组成的中空结构的硅碳复合物颗粒，而颗粒外部由碳层进行包覆。通过SEM切片、EDS以及高分辨TEM等表征手段，可以看到颗粒内部由纳米硅与薄层石墨层结构构筑了微米尺寸的中空结构，该结构内部不但形成了导电的三维网络结构，而且为纳米硅的体积膨胀提供了充足的缓冲空间，从而大幅提升了硅碳负极材料循环稳定性。相比于传统石墨取代薄层石墨与纳米硅制备的硅碳复合物，薄层石墨制备的硅碳负极的比容量达到958 mAh/g，扣电在0.5 C下循环500次后容量保持率可维持在88%左右。本文作者也从实用角度评价了S/MG全电循环性能，与三元NCM811正极材料组装成的软包全电池，在1 C倍率充放电下，循环1000周后电池容量保持率可达86%，可为高能量密度锂电技术的研究提供实验依据。

关键词: 纳米硅, 薄层石墨, 硅碳复合材料, 中空结构

Abstract:

Silicon/carbon anodes have received extensive attention in the development of high-energy Li-ion batteries. However, Si's rapid capacity fading impedes their commercial application because of the huge volume change in Si upon lithiation-delithiation. In this study, multilayer graphite materials with flexible structures and nanosilicon particles were modified separately by the COOH groups in carboxymethyl cellulose (CMC) and the NH2-groups in ethyl silicate (TEOS) to fabricate the nanosilicon/multilayer graphite composite (S/MG). In the silicon carbon anode materials prepared by traditional mechanical mixing processes, nanosilicon particles and carbon materials fail to form homogeneous composites. However, in this study, the modified nanosilicon particles were homogeneously deposited on the surface of graphite layers through electrostatic interaction. Through ball milling, a novel carbon-coated granule with a hollow structure was formed by the S/MG layers. Such micron hollow structures were confirmed via scanning electron microscopy, elemental mapping, and high-resolution tunneling electron microscopy measurements. The structural uniqueness not only includes an inner buffer space for silicon volume expansion but also an excellent conductive three-dimensional network for silicon particles. Compared to the silicon carbon material prepared from the graphite material and nanosilicon particles under the same conditions, S/MG showed a high reversible capacity of 958 mAh/g, and good cycling stability (88% of capacity retention) was achieved after 500 cycles at a 0.5 C rate through the coin half-cell test. We also evaluated S/MG from a practical perspective through the characterization of pouch full cells prepared with NCM811 as the cathode. The cells exhibited a stable cycling performance with a capacity retention of 86% over 1,000 cycles at a 1 C rate. Thus, this study provides a potential anode material for the research and development of high-energy-density LIBs.

Key words: nano silicon particles, multi-layers graphite, silicon/carbon composites, hollow structure

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