储能科学与技术

• 储能材料与器件 •    

TiO2/TiN异质结内建电场的构筑及多硫化锂催化转化性能研究

杜陈强(), 聂周缓, 王慧楠, 张纪伟, 张经纬()   

  1. 河南大学纳米科学与工程研究院，河南省 开封市 475004
  • 收稿日期:2024-02-23 修回日期:2024-03-12
  • 通讯作者: 张经纬 E-mail:dcqxinyang@126.com;jwzhang@henu.edu.cn
  • 作者简介:杜陈强（1987—），男，博士，讲师，新能源材料与器件，E-mail：dcqxinyang@126.com；
  • 基金资助:
    TiN/MxOy异质结内建电场的构筑及锂硫电池穿梭效应的抑制机制研究(NSFC 52002116)

Construction of Built-In Electric Field in TiO2@TiN Heterojunctions toward Boosting the Polysulfide Conversion

ChenQiang Du(), ZhouHuan Nie, HuiNan Wang, JiWei Zhang, JingWei Zhang()   

  1. Institute of Nanoscience and Engineering, Henan University, Kaifeng 475004, Henan, China
  • Received:2024-02-23 Revised:2024-03-12
  • Contact: JingWei Zhang E-mail:dcqxinyang@126.com;jwzhang@henu.edu.cn

摘要：

锂硫电池因具有较高理论容量和能量密度，成为最有前景的下一代电池体系之一。正极材料存在导电性差和多硫化锂转化反应动力学缓慢等问题引起严重的穿梭效应，致使硫利用率低、功率密度小、循环寿命短，严重制约了锂硫电池商业化进程。异质结复合材料具有丰富的活性位点和催化活性，能够催化多硫化锂氧化还原反应，然而其对多硫化锂催化转化机制仍不清晰。本工作以原位构建球形TiO2/TiN异质结复合材料为模型，研究异质界面结构与其对多硫化锂的“吸附-催化-转化”行为，试图解决上述问题。采用多硫化锂吸附实验、X射线光电子能谱分析、紫外可见光谱分析、恒电流充放电测试和循环伏安测试等手段，研究异质界面内建电场形成机理及其对锂硫电池电化学性能的影响。结果表明，TiO2/TiN异质结界面形成由TiN指向TiO2的空间电荷区并构成内建电场。异质结内建电场显著改善多硫化锂锚定能力，加速Li+快速传输，提高多硫化锂向Li2S转化能力。TiO2/TiN异质结复合材料组装的锂硫电池倍率循环测试结果表明在0.05 C电流密度下初始放电比容量高达1070 mAh/g，多次循环后1 C电流密度下容量仍保持60.7%。变温循环伏安测试结果表明TiO2/TiN异质结复合材料将Li2S转化反应活化能降低至2.73 kJ/mol。本工作为锂硫电池正极复合材料的设计和推动锂硫电池进一步发展提供新思路。

关键词: 锂硫电池, 多硫化锂, 穿梭效应, 异质结, 内建电场

Abstract:

Lithium sulfur batteries with the merits such as high theoretical specific capacity and energy density, has become a great potential power cell during the next generation secondary battery systems. Sulfur cathode still suffer some problems such as poor conductivity and sluggish redox kinetics of polysulfide conversion reactions, which trigger a serious shuttle effect, ultimately resulting in low sulfur utilization, poor power density, bad cyclability and hinder further development of lithium sulfur batteries. Heterostructure composites with abundant active sites and superior catalytic activity, can catalyze polysulfide conversion effectively. However, catalytic mechanisms of heterostructure interface on polysulfide conversion remain poorly understood. This paper is devoted to study heterostructure interface and its effects on absorption, the reduction/oxidation of lithium polysulfide within situ synthesized sphere TiO2/TiN composite as models to solve the above scientific question. The formation mechanisms of built-in electric field and the effects of heterostructure interface on electrochemical performances of lithium sulfur batterie are investigated through absorption experiments, XPS, UV-vis spectroscopy analysis, galvanostatic charge-discharge and cyclic voltammetry tests. The results showed that a space charge region and built-in electric field formed at the interface between TiO2 and TiN with electrons flow from TiN to TiO2. The built-in electric field improve anchor ability of lithium polysulfides species, facilitate the Li+ transport rapidly and promote the conversion reaction between lithium polysulfides and Li2S. The step-increased current densities charge-discharge tests present that TiO2/TiN heterojunction composites based lithium sulfur batteries deliver the discharge capacity of 1070 mAh/g at 0.05C, and keep the capacity retention of 60.7% at 1C. Cyclic voltammetry tests at various temperatures indicate the reaction activation energy of lithium polysulfide to Li2S decreases to 2.73 kJ/mol. It provides a new idea for designing the composite cathode materials for lithium sulfur batteries and accelerating further development of lithium sulfur batteries.

Key words: lithium-sulfur battery, lithium polysulfide, shuttle effect, heterostructure, built-In electric field

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