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研究论文

用于石墨负极的高性能聚丙烯酸锂基复合粘结剂的制备及性能研究

郑坤贵a, 刘君珂a, 胡轶旸a, 尹祖伟a, 周尧a,*, 李君涛a, 孙世刚b   

  1. a厦门大学能源学院 福建厦门 361102;
    b厦门大学化学化工学院 福建厦门 361005
  • 投稿日期:2024-05-16
  • 通讯作者: * E-mail: zhouy@xmu.edu.cn
  • 基金资助:
    国家重点研发专项课题 (2022YFB2502103), 厦门市重大科技项目(3502Z20231057), 国家自然科学基金(No. 22309153, No.22288102)和中央高校基本科研业务费(No. 20720230039)资助项目.

A Lithium Polyacrylate-based High-performance Composite Binder for Graphite Anode

Kungui Zhenga, Junke Liua, Zu-Wei Yina, Yao Zhoua,*, Jun-Tao Lia, Shi-Gang Sunb   

  1. aCollege of Energy, Xiamen University, Xiamen, Fujian 361102;
    bCollege of Chemistry and Chemical Engineering, Xiamen University, Xiamen Fujian 361005
  • Received:2024-05-16

聚丙烯酸锂(LiPAA)由于其较高的离子电导率和良好的化学稳定性被广泛用作锂离子电池负极的粘结剂,但是LiPAA粘度低、硬度大,作为粘结剂时负极极片的粘接性能、柔韧性和可加工性是较大挑战。本论文将LiPAA与多种高分子聚合物复配,通过添加羧甲基纤维素(CMC)或黄原胶(XG)提高粘结剂粘度,采用透明质酸钠(HA)降低粘结剂脆性,添加丁苯橡胶(SBR)提高剥离强度,开发了两款基于LiPAA的复配型粘结剂(LiPAA-CMC-HA-SBR及LiPAA-XG-HA-SBR)。与商用负极粘结剂(CMC-SBR)相比,所得两款基于LiPAA的复配粘结剂不仅具有合适的粘接强度及柔韧性,且可显著改善石墨颗粒、导电剂、电解液之间的亲和性,促进锂离子在电极/电解液界面的传输,从而获得高电化学性能。在0.5 C的电流密度下,在循环150圈后,采用上述两款复配粘结剂制备的石墨负极容量分别为209 mAh g-1及191 mAh g-1,远高于使用CMC-SBR粘结剂的石墨负极(108 mAh g-1)。此外,传统配方需添加大量SBR(~50%),而基于LiPAA的配方中只需少量SBR即可保持极片完整性,且可在低粘结剂含量(~3%)和高活性物质载量(~95%)时保持良好力学性能,制备的石墨负极极片也拥有良好的电化学性能,具有较好工业化应用前景。

关键词: 锂离子电池, 石墨负极, 粘结剂, 聚丙烯酸锂

Lithium polyacrylate (LiPAA) is widely used as a binder for lithium-ion battery anodes due to its high ionic conductivity and good chemical stability. However, LiPAA has disadvantages such as low viscosity and high hardness, as a result of which the adhesive performance, flexibility and processability of the anode becomes an issue when LiPAA is used as a binder. In this paper, a composite formula was developed by integrating LiPAA with other polymers, including carboxymethyl cellulose (CMC) or Xanthan gum (XG) to tune the viscosity, sodium hyaluronate (HA) to reduce the brittleness, and benzene butadiene rubber (SBR) to improve the stripping strength. On this basis, two LiPAA-based composite binders (LiPAA-CMC-HA-SBR and LiPAA-XG-HA-SBR) were developed. Compared with the commercial anode binder (CMC-SBR), the two LiPAA-based composite binders both demonstrate well-tuned bonding strength and flexibility; more importantly, they also can significantly improve the interfacial affinity between the graphite particles, the conductive agent and the electrolyte, which hence promotes the diffusion kinetics of lithium ions at the electrode/electrolyte interface and thus improves the electrochemical performance of the graphite anode. At the current density of 0.5 C, after 150 cycles, the graphite anode prepared with our two composite binders display a capacity of 209 mAh g-1 and 191 mAh g-1, respectively, which was much higher than the graphite anode prepared with the commercial CMC-SBR binder (which is 108 mAh g-1). The graphite anode prepared with our binder also demonstrate much higher rate capability and better cycling stability compared to the control. Characterizations of the cycled anode reveal that, in the anode prepared with our binders, much more homogeneous distribution of the conductive carbon and the graphite particles was observed, and a SEI with higher fraction of LiF was formed. In addition, in the commercial CMC-SBR formula, a mass fraction of SBR up to 50% is required; in comparison, in our two LiPAA-based formulations, only a small fraction of SBR is employed yet which can still maintain the integrity of the anode sheet. It is worth noting that, at a low binder content (~3%) and high active material load (~95%), the graphite anode sheet prepared by these two composite binders can still maintain remarkable mechanical strength, and it also demonstrates excellent electrochemical performance, showing the promising industrialization potential of such LiPAA-based composite binders.

Key words: Lithium-ion batteries, Graphite anode, Composite binder, Lithium polyacrylate