高性能钠离子电池负极合金化诱发压电效应调控钠脱嵌的实现方法

Alloy-based materials hold great promise for their high theoretical capacity as the sodium-ion batteries (SIBs) anode, but their practical application is hindered by the poor conductivity, slow reaction kinetics and large volume change during discharge/charge processes. In this proposal, we will fabricate different dimensional laminated or core-shelled structured bariucm titanate (BTO) and alloy-based (M) composites. The large expansion of alloy-based material during Na-ion insertion is exploited as an energy source via piezoelectric BTO, which is a synergetic effect on Na-ion battery anode. First-principles combined with in-situ XRD, are used to explore the influence of alloy’s varieties, contents and reaction conditions on the resulting size, dimension and structure of composites. The controllable preparation methods of the alloy-based anode composites based on piezoelectric effect will be established. The relationship between structure and electrochemical performance will be studied in Na-ion battery. Polarization direction of BTO, volume effect of alloy-based materials as well as structure parameters (dimension, spatial configuration and interface) of the composites in the process of Na+ intercalation/deintercalation and their mechanism of influence on Na-ion transport are investigated through the molecular dynamics simulation, high voltage electric field polarization and scanning electrochemistry. The mechanism of Na+ intercalation of alloy-based composites based on the piezoelectric effect is revealed. It also provides theoretical guidance for the design and synthesis of novel alloy-based composites and their application in Na-ion batteries.

合金元素因理论容量高被认为是最具潜力的钠离子电池负极材料，但其实际应用却受制于导电性差、反应动力学缓慢和充放电过程中体积变化严重的缺点。本项目拟采用钛酸钡(BTO)和合金(M)构建不同维度叠层或核壳结构的BTO/M复合材料，实现合金化反应产生的机械应力与BTO压电电压的相互转换并协同调控钠离子的传输。利用第一性原理结合原位XRD技术系统研究合金元素、含量和反应条件对复合材料的尺寸、维度和结构的影响规律，建立基于压电效应的合金类复合材料的可控制备方法；以研制BTO/M复合材料作为钠离子电池负极，通过分子动力学模拟结合高压电场极化、扫描电化学技术研究BTO极化方向、合金化体积效应和复合材料结构参数（维度、空间构型、界面特征）在脱嵌钠过程中的演变规律及其对钠离子传输的影响机制，揭示基于压电效应的合金类复合材料的嵌钠机理。项目成果为新型合金类复合材料的设计合成及其在钠离子电池中的应用提供理论指导。

本项目针对合金类材料导电性差、脱嵌钠时体积变化大和反应动力学缓慢的瓶颈性难题，引入功能性材料钛酸钡（BTO），通过机械球磨、气相沉积、静电纺丝、溶剂热等技术构建了四种不同维度和结构的复合材料。系统研究了合金类材料（red-P、SnO2）和BTO含量、制备条件对复合材料尺寸、维度和结构的影响，建立了基于铁电/压电效应的合金类复合材料的可控制备方法；探究了复合材料的脱嵌钠特性和反应机理，揭示了材料的结构、组成对其电化学性能的影响规律，实现了超长寿命的可快充的钠离子电池的组装；通过高压电场极化和分子动力学模拟计算研究了BTO极化方向和强度对钠离子传输机制的影响规律；借助扫描电化学显微镜（SECM）和原位X射线粉末衍射（XRD）等技术探究了合金化体积效应诱发压电效应调控钠离子传输机制以及复合材料维度和结构在脱嵌钠过程中的演变规律，阐明了基于铁电/压电效应的合金类复合材料的嵌钠机理。主要研究成果如下：（1）引入铁电材料（钛酸钡）以及正向极化可提升钠离子扩散，而负向极化会阻碍钠离子的扩散；（2）钛酸钡在外部电场或压力作用下容易极化形成内部电场，该内部电场可有效加速钠离子扩散，诱导钛酸钡产生内部电场的条件来自于电池自身电场对钛酸钡的铁电极化和合金体积膨胀微压应力产生的压电效应；（3）一维异质结构的SnO2/BTO@NCNF复合材料在5 A·g-1电流密度下可稳定循环10000圈仍保持183.4 mAh·g-1的可逆容量，三维核壳结构的BTO@SnO2@P-C复合材料在10 A·g-1电流密度下稳定循环10000圈可保持144.4 mAh·g-1的可逆容量，突破了钠离子电池在大电流密度下的超长稳定循环。项目成果为新型合金类复合材料的设计合成及其在二次离子电池中的应用提供了理论和技术基础，具有重要的学术价值和广阔应用前景。