高储钠能力类石墨烯硼碳新结构的制备及调控机制

Among the traditional graphite materials, due to its low efficience of sodiation/desodiation and slow kinetic rate, etc., the application of carbon mateials used for high-performance sodium-ion batteries (SIBs) is restricted, which would lead to the serious lack of anode materials with large capacity, high diffusivity of sodium ions and superior cyclability. For this purpose, in this work, the gas-solid reaction route is developed to fabricate the high-performance anode materals of SIBs by the reaction between double-faced storage graphene and vapor boron. Depending on the optimal control of gas-solid reaction conditions, the microsturcture and sodium storage properties of BCx structure are enhanced. The mutual relationship between technologic parameters of gas-solid reaction and sodium storage properties of BCx material is studied. Based on the investigation of concentration, existence form and distribution state of boron in graphene sheets, the regulatory mechanism of BCx structure by one-step gas-solid reaction is studied. On the basis of the dependence of the properties of SIBs used BCx structure as anode materials on the microstructure and concentration, existence form and disperse state of boron, the sodium storage mechanism of BCx structure would be clarified by investigating the diffusion coefficient and local structue of sodium ions, as well as the law of the microstructure of electrode during the charge-discharge cycles. The success of our project research would provide not only an novel route of structural design and preparation technology for the novel anode materials in the future, but also the significant support on technology for the first application of SIBs in large scale energy storage systems.

传统石墨材料因对钠离子脱嵌效率低、动力学速率缓慢和体积膨胀较大，限制了其在钠离子电池中的直接应用，导致大容量、高钠扩散率和良好循环性能钠离子电池负极材料的严重匮乏。为此，申请人在发明气相硼原子控制技术的基础上，提出利用气固反应工艺一步制得高储钠能力类石墨烯硼碳新结构的路线。以气相硼原子和石墨烯为原料，通过对气固反应工艺参数优化控制，来调控产物的微观结构（缺陷、层间距和微晶尺寸）；并掌握气固反应工艺参数与硼碳新结构储钠性能（能量密度、倍率特性和循环寿命）之间的相互关系。通过考察硼碳新结构中硼原子含量、存在形式和分散状态，研究硼碳新结构的调控机制。考察硼碳新结构储钠性能与微观结构的内在联系，并结合钠离子在硼碳新结构中扩散能力、局域结构和电极微结构演变规律，探索可调控制备的硼碳新结构储钠机制。本项目将为钠离子电池负极材料的制备提供新途径，为我国率先将钠离子电池应用于规模储能提供重要技术支撑。

为开发高储钠能力的钠离子电池负极材料，本项目采用气-固反应工艺实现了对碳结构的调控，形成了新的类石墨烯硼碳结构（BCx）。因硼碳结构的储钠能力、导电性和机械强度均优于石墨烯，使得在脱嵌钠离子过程中提高了电子、离子传输能力以及电极机械稳定性，从而使钠离子电池具有了更高的容量、倍率和循环性能。对于硼碳结构，作为电子受体使得碳结构更容易从钠得到电子，增强了对钠离子的吸附作用，但也增加了电池放电时钠离子迁移阻力，从而导致可逆容量远达不到其理论值。本项目执行过程中，创新性地采用复合结构设计策略，将超离子导体PbTe纳米点锚固在硼碳结构中，有效提升了硼碳结构的电化学性能，同时采用原位结构表征手段和电化学分析技术，揭示了硼碳结构的储钠机制。本项目还发展了SbPO4@BCx复合材料，发现硼碳结构与PO43-阴离子能够形成双基体效应，有效提升了复合材料脱嵌钠离子的循环稳定性。总体上，本项目的研究不仅为钠离子电池负极材料的制备提供新途径，而且为我国率先将钠离子电池应用于规模储能提供重要技术支撑。在项目执行期间，研究内容还进行了拓展，研究了硼碳纳米管的制备方法和结构特性、发明了一种硼量子点的制备方法并设计合成了硼量子点/石墨烯纳米复合材料，极大地拓展了硼碳结构的合成方法和应用领域。项目组完成了预期目标，在Journal of Power Sources、Carbon、Materials Advances、Chemical Engineering Journal、Electrochimica Acta、ACS Applied Energy Materials等期刊共发表研究论文19篇，另有多项工作已完成并正撰写论文或已投稿；授权发明专利1项，申请暂未授权发明专利8项，专利转让1项，总经费共3万元；培养了山西省高等学校优秀学术带头人1名，培养多名硕士研究生；相关成果获山西省自然科学二等奖1项。通过本项目的实施，进一步增强了项目组的整体科研实力。