【作者】 王岩；

【导师】 左朋建； 谢继春；

【作者基本信息】 哈尔滨工业大学 ， 化学工程（专业学位）， 2021， 硕士

【摘要】 锂离子电池由于其具有较高的能量密度、较长的使用寿命并且循环时无记忆效应、环境友好、使用范围广等特点已经成为电子产品重要的储能装置。随着电子产品各项功能的充分发展,不可避免的导致功耗增加,提高电池的倍率性能已成为首要解决的问题。近年来从负极电极结构调控及材料包覆等多个方面提出了解决方案,但其复杂的制备工艺带来了高昂的制备成本,且倍率性能提升的同时也带来了其他的新问题,因此相关技术措施并未得以广泛应用。因此,发展制备简单、成本可控的电极结构调控的新技术,使之能够应用于商业电池体系成为了亟待解决的问题。本文首先采用激光物理刻蚀工艺,在辊压后的负极片上进行激光刻蚀,将极片正反面的石墨进行高温烧蚀处理,实现了对电极结构的调控,并有效地改善了化学刻蚀过程中出现的石墨晶体结构被破坏导致坍塌的现象。研究结果表明,激光刻蚀极片能有效改变极片表面的形貌,产生新的孔隙,不但整体提升了极片的孔隙率,而且还改善了孔隙率在极片厚度方向上的均匀性,孔隙率由28.01%提升至34.33%。在倍率性能方面,新产生的孔隙作为锂离子的扩散通道,有效地缩短了锂离子的迁移路径,而且更大的孔隙率也增大了石墨颗粒的比表面积,从而减小了电流密度,减小极化,提升了电芯的倍率性能,在2.0 C倍率时,恒流充入比提升近3%。同时电芯的常温循环、高温循环性能也分别得到一定程度的提升。考虑到锂离子电池商业应用中对负极性能的特殊要求,提高电极结构的灵活性的需求,本文结合双层涂布工艺设计了一种新的电极结构调控方法。以不同压实密度及不同动力学性能的石墨作为实验材料,将两种不同的石墨分别涂覆在极片的底层和顶层并制备成电芯,结合多种表征方法探究对电极结构和电性能的影响。研究结果表明,双层涂布对电极结构有明显的调控作用,不但优化了电极孔隙率的分布而且还可以调整极片厚度方向两层涂覆石墨浆料的顺序,提高了电极结构的灵活性,降低了制备成本,大大适应了商业化的需求。从电极结构调控结果来看,极片的孔隙率得到了较为明显的提升,由24.13%提升至34.57%,并且在实现孔隙率提升的同时不会对电池的能量密度造成影响。倍率性能方面,双层涂布极片的表面阻抗较低,提高了负极表层动力学性能,有效地减小了负极极化。双层涂布工艺电芯整体上有较大优势,且随着充电倍率的增大,这种变化趋势就越明显,在2.0C倍率时,恒流充入比提升近5.8%。同时电芯的常温循环、高温循环性能也分别得到一定程度的提升。更多还原

【Abstract】 Lithium-ion battery has become an important energy storage device for electronic products due to its high energy density,long service life,no memory effect during the cycle,environmental friendness and wide range of application.With the development of various functions of electronic products,it inevitably leads to the increase of power consumption,thus improving the rate performance of the battery has become the primary problem to solve.In recent years,many solutions have been proposed from the aspects of electrode structure regulation and material coating,etc.However,the complex preparation process brings high preparation cost,and the improvement of rate performance also brings other new problems,so relevant technical measures have not been widely used in application.Therefore,it has become an urgent problem to develop a new technology for the simple preparation and cost controllable electrode structure regulation,so that it can be used in commercial battery systems.In this paper,the laser physical etching process is firstly adopted to carry out laser etching on the anode electrode after rolling,and the graphite on both sides of the electrode is ablated at high temperature to realize the regulation of the electrode structure,it effectively avoids the destruction of graphite which will leads to collapse of the crystal structure in the process of chemical etching.The results show that laser etching can effectively change the surface morphology of the electrode plate and create new pores,it not only improves the overall porosity of the electrode plate,but also improves the uniformity of the porosity along the direction of the electrode plate thickness,the porosity increases from 28.01% to34.33%.In terms of rate performance,new pores as lithium ion diffusion channel,effectively shorten the lithium-ion migration path,and the larger porosity also increase the BET area of graphite particle,so it can reduce the current density,decrease the polarization,and improve the rate performance of the battery,at 2.0C-rate,constant current charge ratio increase the nearly 3%.At the same time,the performance of normal temperature cycle and high temperature cycle of the cell has been improved to a certain extent.Considering the special requirements for the performance of anode electrode in commercial application of lithium-ion battery,a new electrode structure preparation method is designed in combination with the double-layer coating process in this paper.Graphites with different compaction densities and different dynamic properties were used as experimental materials.Two different kinds of graphites were coated on the bottom and top layer of the electrode plate and prepared into a cell.The influence of different characterization methods on the structure and electrical properties of the electrode was investigated.The results show that the double-layer coating has an obvious regulating effect on the electrode structure,which not only optimizes the distribution of electrode porosity,but also adjusts the order of two layers of coated graphite slurry in the direction of electrode thickness,this method improves the flexibility of the electrode structure,reduces the preparation cost,and greatly meets the requirements of commercialization.According to the results of electrode structure regulation,the porosity of the electrode plate has been significantly improved from 24.13% to 34.57%,and the increase of the porosity will not dereriorate the energy density of the battery.In terms of rate performance,the surface impedance of the double-coated electrode plate is lower,which effectively improves the dynamic performance and reduces the polarization of the anode electrode.The double-layer coating technology has a great advantage on electrochemical performance,and the changing trend becomes more and more obvious with the increase of charging ratio.At 2.0C-rate,the constant current charging ratio increases by nearly 5.8%.At the same time,the performance of the cell normal and high temperature cycling has been obviously improved.更多还原