微纳结构锂硅合金负极的硼介入制备及其储能应用基础研究

Li and Si are typical anode materials with ultrahigh specific capacity, but suffer from lithium dendrite growth, and huge volume change, large irreversible capacity during electrochemical reaction, respectively. Nevertheless, Li-Si alloy, combining the characteristics of the two, is believed to be one of the key materials to realize high energy density lithium ion batteries (LIB). This proposal aims to address the difficulty in preparation of nano porous Si, the uncertain relationship between Si and Li in alloy and so on. Starting from the composition and structure design of the alloy, based on its unique electronic structure, B atom will be involved into the construction of micro-nano Li-Si alloys to alter the microstructures along with B doping. Ascribed to the B doping effects in the elaborate Li-Si alloy structure, the transfer of Li will be promoted and the synergistic energy storage effect between Si and Li will be delivered effectively. Through the systematic research on the boron-intervening reduction kinetics for nano silicon and Li-Si alloying process; the functional components and micro-nano structures of Li-Si alloy anode; the electrode / electrolyte interface characteristics and their influence on the electrochemical properties of LIB, the control on the performance of Li-Si alloy anode can be realized. The research work in this project is expected to provide new ideas for the development of high-capacity metal energy storage materials, and also provide theoretical and technological support for the development of high-energy lithium secondary batteries represented by LIB.

锂与硅作为锂离子电池负极时具有高比容量的突出优势，但分别存在锂枝晶生长与体积膨胀、不可逆容量大等问题。锂硅合金负极结合了两者特点，是突破锂离子电池能量密度瓶颈的关键电极材料之一。本项目围绕锂硅合金负极研究中纳米多孔硅制备困难、锂硅组分交互作用不明确的核心问题，从合金的组分与结构设计出发，利用硼元素独特的电子结构，提出采用硼介入法构筑微纳结构锂硅合金负极，硼的介入可调节硅的微观形貌结构并进行同步元素掺杂，为锂的嵌入提供良好的条件，有利于合金组分硅与锂发挥相互协同的储能作用。通过系统研究纳米硅的硼介入还原动力学与锂硅合金化过程、锂硅合金负极的功能组分与微纳结构、电极/电解质表界面特性及其对电池电化学性能的影响机制，实现对锂硅合金负极的性能控制。该研究有望为高容量金属储能材料的开发提供新的思路，为发展以锂离子电池为代表的高能锂二次电池提供理论与技术支撑。

为解决锂硅合金负极研究中纳米多孔硅制备困难、锂硅组分交互作用不明确的问题，本项目从锂硅合金的组分与结构设计出发，利用掺硼氧化硅特殊的晶体结构特征，通过控制镁热还原中硼的介入行为来调节还原产物的微观形貌，实现纳米多孔硅材料的简便可控制备；采用极片预锂化的方法，构筑出微纳结构锂硅合金负极，并应用于高能锂离子电池。主要研究了纳米硅的硼介入还原动力学、硼引入镁热还原过程对材料形貌、物相、孔结构的影响、硼掺杂纳米多孔硅负极极片的预嵌锂改性、电极/电解质表界面特性及其对锂离子电池电化学性能的影响机制。同时，还研究除硼外，其他金属（碳、磷）或非金属元素（钨、钼）介入硅还原过程的影响，并研究其在锂离子电池中的应用。通过项目研究，开发了基于硼介入的微纳结构硅负极材料的制备新方法，并建立了其化学反应动力学模型与微观结构形成理论；找到了优化的元素掺杂微纳结构硅合金负极的制备方法与工艺，提出基于硼、磷等元素介入的纳米多孔硅材料的结构稳定与性能强化策略，开发了系列兼具高导电、高容量与长寿命的硅负极材料，成功实现高性能硅碳负极材料的产业化应用。项目执行期间，在Advanced Functional Materials等国际权威与重要期刊发表已标注论文12篇，全部为JCR1区论文，ESI高被引论文1篇，最高影响因子19.924，单篇最高他引82次；获授权中国发明专利4件，获中国有色金属工业技术发明一等奖1项。项目负责人2021年入选湖南省科技创新计划“湖湘青年英才”，培养博士生获博士学位2名，硕士生获硕士学位4名。