储能科学与技术 ›› 2023, Vol. 12 ›› Issue (7): 2045-2058.doi: 10.19799/j.cnki.2095-4239.2023.0248

• 储能锂离子电池系统关键技术专刊 • 上一篇    下一篇

高能量密度磷酸铁锂正极设计

李淼1(), 于永利1, 吴剑扬2, 雷敏1, 周恒辉2()   

  1. 1.北京泰丰先行新能源科技有限公司,北京 102200
    2.北京大学,北京 100871
  • 收稿日期:2023-04-20 修回日期:2023-05-17 出版日期:2023-07-05 发布日期:2023-07-25
  • 通讯作者: 周恒辉 E-mail:limiao@pulead.com.cn;hhzhou@pku.edu.cn
  • 作者简介:李淼(1985—),女,博士,副研究员,研究方向为高压实密度磷酸铁锂正极材料改性,E-mail:limiao@pulead.com.cn
  • 基金资助:
    青海省科技计划(2022-GX-154);国家自然科学基金项目(21875004);国家自然科学基金区域创新发展联合基金(U19A2019)

Design of high-energy-density LiFePO4 cathode materials

Miao LI1(), Yongli YU1, Jianyang WU2, Min LEI1, Henghui ZHOU2()   

  1. 1.Beijing Taifeng Pulead New Energy Resources Technology Co. , Ltd. , Beijing 102200, China
    2.Peking University, Beijing 100871, China
  • Received:2023-04-20 Revised:2023-05-17 Online:2023-07-05 Published:2023-07-25
  • Contact: Henghui ZHOU E-mail:limiao@pulead.com.cn;hhzhou@pku.edu.cn

摘要:

磷酸铁锂(LiFePO4)是锂离子动力和储能电池中应用最广泛的正极材料,为了满足市场对锂离子电池更高能量密度的要求,必须开发具有更高能量密度的LiFePO4材料。根据能量密度的定义,本文从LiFePO4的电压平台、粉体压实密度和质量比容量三个方面展开论述,通过电化学和材料学方面的机理分析,指出提高粉体压实密度和质量比容量是具有潜力的改进方向。结合研发经验、市场调研和国内外的研究成果,在提高材料粉体压实密度方面,本文总结了原料种类选择、烧结制度改善、大小颗粒级配这三类最有效的方法,具体介绍了制备LiFePO4的磷酸铁路线,烧结制度伴随的杂质问题,以及大小颗粒级配的流程差异;在提高质量比容量方面,从LiFePO4的本征特性出发,介绍了纳米化、碳包覆、元素掺杂、缺陷控制以及晶体择优取向五种策略,指出纳米化、碳包覆、元素掺杂是目前最有效的提高质量比容量的改性方法。上述方法都已经应用于市场上的LiFePO4产品之中,其提高能量密度的有效性得到了国内多家电池厂的认证。目前LiFePO4正极材料的能量密度还未被完全开发,仍需要继续开展材料改性的研究和生产工艺的优化。

关键词: 磷酸铁锂, 高能量密度, 粉体压实密度, 容量, 改性方法

Abstract:

Lithium iron phosphate (LiFePO4) is one of the most widely used cathode materials in lithium-ion-based electric vehicles and energy storage batteries. To meet the market demand for high-energy-density lithium-ion batteries, high-energy-density LiFePO4 products must be developed. According to the definition, energy density depends on the following three aspects: the voltage plateau, powder compacted density, and mass specific capacity. Based on electrochemistry and materials science, increasing the powder compacted density and mass specific capacity is a promising modification direction; however, voltage plateau is an intrinsic characteristic of LiFePO4. Based on technical experience, market research reports, and previous research, the choice of raw materials, the modification of the sintering process, and particle gradation are the best modification methods for increasing powder compacted density. In the iron phosphate route, impurities are the primary issue in sintering processes; thus, different procedures for particle gradation are proposed. Considering mass specific capacity, the following strategies are proposed based on the intrinsic characteristics of LiFePO4: nanosizing, carbon coating, elemental doping, defect control, and crystallographic preferred orientation. Moreover, nanosizing, carbon coating, and elemental doping are the most effective modification methods for increasing mass specific capacity. Usually, nanosizing and carbon coating are combined for increasing electronic conductivity, whereas elemental doping is mostly used for increasing Li-ion diffusion coefficient and preferred orientation. These modification methods are used in LiFePO4 products available in the market and are confirmed by domestic battery factories. However, the energy density of LiFePO4 has not yet been maximized; hence, additional methods for modifying the material properties and production processes need to be developed.

Key words: lithium iron phosphate, high energy density, powder compacted density, capacity, modified methods

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