直孔电极和多孔铜集流体的溶液相转化法制备与表征

发布时间：2018-03-14 15:34

  本文选题：溶液相转化法　切入点：直孔电极　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：锂二次电池是重要的电化学储能体系,如今的商业化应用对其能量密度和功率密度有更高的要求。提高能量密度和功率密度的方法之一是从成型工艺和装配技术的角度入手优化电极的微结构。当电极上的活性物质负载量较大且处于大倍率充放电时,电极中曲折的孔道将会阻碍锂离子的液相扩散,导致锂离子分布不均而存在浓差极化。针对这一问题,本文从成型工艺的角度出发,利用溶液相转化法成型具有直孔结构的LiFeP04电极并研究了直孔对电极电化学性能的影响。另一种提高能量密度以及功率密度的方法是优化正、负极材料,即从电极材料入手。锂金属因具有极高的理论能量密度和极低的氧化还原电位而被认为是理想的负极材料。然而,锂金属负极中枝晶的不可控生长给电池体系造成了潜在的短路风险。针对这一问题,本文提出了利用溶液相转化法成型多孔铜集流体,以抑制枝晶的产生和生长,优化锂金属负极的电化学性能。本论文的第一部分内容是利用溶液相转化法制备多孔LiFePO4电极,主要探究了溶液相转化法的成型工艺、实验参数等对电极的微结构和电化学性能的影响。实验表明采用NMP为溶剂、PVDF为粘结剂、水为絮凝剂,并在10℃条件下完成溶液相转化可以成型出具有直孔结构的电极。电化学数据表明当电极处于高负载量大倍率条件下,直孔结构对改善浓差极化有明显的作用,溶液相转化制备的电极表现出比传统电极更加突出的电化学性能。本论文的第二部分内容研究了利用溶液相转化法成型具有双极孔结构的多孔铜,并分别利用一步法和两步法两种热处理工艺去除其中的聚合物相而得到具有一定强度的多孔铜集流体。将它应用于锂金属负极时,多孔铜中的大比表面为锂的沉积提供了大量的有效沉积位点,而其中的孔隙起到了抑制锂枝晶生长的作用。以两步法热处理的多孔铜作为集流体的锂金属电池表现出良好的电化学性能,在锂沉积量为1mAh/cm2、电流密度为1 mA/cm2的条件下,循环寿命高达470小时,在前225个循环中库伦效率不低于96%。
[Abstract]:Lithium secondary battery is an important electrochemical energy storage system. Today's commercial applications require higher energy density and power density. One of the ways to improve energy density and power density is to optimize the microstructure of the electrode from the point of view of molding process and assembly technology. When the loading amount of active substances is large and the charge / discharge rate is large, The zigzag pore channel in the electrode will hinder the liquid phase diffusion of lithium ion and lead to the concentration polarization due to the uneven distribution of lithium ion. The LiFeP04 electrode with straight pore structure was fabricated by solution phase inversion method and the effect of straight hole on the electrochemical performance of the electrode was studied. Another way to improve the energy density and power density is to optimize the positive and negative electrode materials. Lithium metal is considered to be an ideal negative electrode material because of its high theoretical energy density and extremely low redox potential. The uncontrollable growth of dendrite in lithium metal negative electrode causes potential short circuit risk for the battery system. In order to suppress the generation and growth of dendrite, a solution phase inversion method is proposed to form porous copper in this paper. The first part of this thesis is to prepare porous LiFePO4 electrode by solution phase inversion method. The effects of experimental parameters on the microstructure and electrochemical properties of the electrode showed that NMP was used as binder and water as flocculant. The electrode with straight pore structure can be formed by the solution phase transformation at 10 鈩，

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