基于氟磷酸铁钠正极和碳质负极的钠离子电池构建及电化学行为研究

Sodium-ion batteries (SIBs) have shown great prospects in large-scale energy storage applications owing to the huge availability and wide distribution of sodium resources. However, the relatively large radius and heavy mass of Na+ ion would restrict its reversible reaction with the electrode materials. Since Na2FePO4F cathode possesses a robust framework with abundant ionic diffusion channels, and carbonaceous anode shows advantages of low cost and high electrical conductivity, moreover, considering their large working potential difference, the pairing of Na2FePO4F cathode and carbonaceous anode promises the realization of fast, stable, and efficient sodium-ion storage. This project plans to fabricate the Na2FePO4F/porous carbon fiber micro/nano-cathode material, as well as the graphene/porous carbon fiber micro/nano-anode material via an electrospinning technique. By adjusting the experimental parameters, the optimized structures of ultrasmall Na2FePO4F nanoparticles and highly exfoliated graphene layers that could expose sufficient active sites, and one-dimensional porous carbon nanofibers that could interlink into a stable microscale three-dimensional conductive network, are achieved, which solve the problems of low conductivity facing Na2FePO4F cathode and low specific capacity facing carbonaceous anode. By means of the electrochemical analyses, the Na-storage mechanism is revealed, and the structure-performance correlation is elucidated. Finally, the as-prepared cathode and anode materials are matched to construct the high performance, low cost, and high safety Na-ion full batteries with the surface/interface effect being understood, offering a new and feasible perspective to promote the commercialization of SIBs.

钠离子电池凭借资源优势在大规模储能领域有重要应用前景。然而，钠离子较大的半径和质量限制它与电极材料的可逆反应。氟磷酸铁钠正极结构稳定、离子扩散通道丰富，碳质负极成本低廉、导电性高，且二者工作电位差较大，相互配合有望实现钠离子快速、稳定、高效存储。本项目拟采用静电纺丝技术制备氟磷酸铁钠/多孔碳纤维微纳正极材料，以及石墨烯/多孔碳纤维微纳负极材料。通过调控实验参数优化材料结构，得到超小纳米尺寸的氟磷酸铁钠和高度剥离的石墨烯以充分暴露活性位点，同时复合一维多孔碳纳米纤维以交联形成稳定的微米级三维导电网络，进而解决氟磷酸铁钠正极导电性较差，碳质负极比容量较低的问题。结合电化学分析手段，阐明电极材料的储钠机理，理清其中构效关系。最后将正、负极材料匹配构建高性能、低成本、高安全的钠离子全电池，理解电池内部表界面作用机制，为开发具有商用潜力的钠离子电池提供一个新的可行思路。

磷酸盐正极结构稳定、离子扩散通道丰富，碳质负极成本低廉、导电性高，且二者工作电位差较大，相互匹配有望构建高性能钠离子电池。然而，磷酸盐正极的实际容量和导电性亟待提高，碳质负极也面临比容量较低的问题。本项目通过构筑多孔微纳米结构，表界面改性，离子掺杂，反应电对调控等策略，有效促进了钠离子在磷酸盐正极和碳质负极中的高效、快速、稳定存储，提高了材料的离子/电子电导和比容量。发展了简便、普适的纳米电极材料制备方法，利用多种（非）原位表征手段，结合电化学测试和理论计算模拟，阐明了电极材料的储钠机理和反应动力学，并建立了材料结构、成分与性能之间的动态构效关系。将所设计的磷酸盐正极和碳质负极合理匹配，构建了高能量、低成本、高安全钠离子电池，在规模化储能和低速电动车等领域展现一定应用前景。在本项目的资助下，以第一/通讯作者在Adv. Mater., Angew. Chem. Int. Ed., Adv. Funct. Mater., Adv. Sci., Energy Storage Mater., Small等重要期刊发表学术论文23篇（SCI论文21篇，中文论文2篇），其中IF>10论文14篇，中科院一区论文18篇，ESI高被引论文4篇，热点论文2篇，单篇最高引用205次。申请国家专利5件，获授权3件。项目负责人入选中国科协青年人才托举工程（2018年），获天津市自然科学一等奖（R5, 2020年）；在国内外重要学术会议如国际复合材料科技大会，国际光电功能材料研讨会，全国电化学大会，中国能源材料化学研讨会，全国储能科学与技术大会等作邀请报告7次，圆满完成项目预定目标。