锂硫电池用柔性多孔碳/TiO2复合纳米纤维电极的制备及其动态电化学反应机制研究

Flexible batteries are the key component of smart wearable electronics. However, current commercialized battery materials suffer low energy density and inferior flexibility problems, which limit their practical applications in the ever-growing market of wearable electronics. In this project, we will combine advantages of the high energy density of lithium sulfur battery and outstanding flexibility of electrospun fibers, and develop nitrogen doped porous carbon/TiO2 composite nanofibrous electrodes by using electro-spinning technology. In this research, we will first examine the influence of solution characteristics, process parameters and calcination conditions on the formation of flexible fibrous films, and elucidate the inherent regulation mechanism for the formation of flexible fibrous structures. After the preparation of flexible sulfur electrodes, we will calculate and simulate the variation of the concentration of lithium polysulfides in the electrodes along with the changes of battery voltage, then identify how polysulfide chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Thereafter, we will establish the electrode reaction equations that driven by stress in the curved electrodes, and reveal the dynamic electrochemical reaction mechanisms of flexible lithium sulfur batteries. We expect to develop flexible Li-S batteries that can obtain a capacity retention of 80% after 800 cycles with a bending radius of 25o/100 mm at a charge and discharge rate of 1/3 C.

柔性电池是智能可穿戴电子产品的关键部件，但现有商业化电池材料存在能量密度低和柔韧性差等问题，限制了其在可穿戴电子产品市场的实际应用。本项目拟结合锂硫电池的高能量密度和静电纺纤维突出的机械柔性的优势，通过静电纺丝技术开发原位氮掺杂的多孔碳/TiO2复合纳米纤维基柔性硫电极，并揭示高载硫量的柔性锂硫电池的动态电化学反应机理。研究将考察静电纺丝原液性质、加工参数和煅烧条件在复合纤维微观结构调控机制中的本构关联，阐明柔性多孔复合纳米纤维电极的成型及结构调控规律；计算并模拟多孔复合纳米纤维电极中多硫化锂浓度随电压变化的规律，明晰多硫化锂扩散和参与反应的过程；建立电池受弯曲应力驱动的电极反应方程，揭示锂硫电池动态电化学反应机制，实现柔性锂硫电池在1/3C充放电倍率下，经过800次±25o/100mm的扭转后容量保留大于80%的目标，以满足其在智能可穿戴电子产品中的应用需求。

柔性可穿戴电子器件广受科研学者的关注，发展与之匹配的柔性电池至关重要。但现有商业化电池材料固有的能量密度低和机械性能差等问题，限制了电池的柔性化发展。本项研究中，立足柔性锂硫电池的总体研究目标，围绕多级孔无机纤维材料设计、柔性纤维正极制备及无机纤维柔性机理，我们重点开发并制备了多种适用于锂硫电池的高活性正极载硫材料，系统研究了相关的电化学性能，拓展了柔性电池的电池结构体系。此外，采用室温锂金属接触腐蚀法开发了新型导电柔性氧化钛纳米纤维，揭示了该反应中的常温多米诺-级联还原机理，为导电陶瓷材料的制备提供了全新的途径。而后，我们将研究工作拓展到柔性可充锌-空电池新领域，组装了实现高柔性兼高比能量（100 mWcm-3）的纤维基可充锌-空电池，进一步丰富了柔性电子器件的研究内容，为发展高比能量的柔性可穿戴电池开辟了新的途径。项目进行期间，共在先进材料、自然通讯、科学进展等顶级期刊发表论文13篇、申请专利14项。申请人入选了上海市海外高层次人才项目、科技启明星等计划。