【作者】 赵恒；

【导师】 贺艳兵； 赵玲；

【作者基本信息】 清华大学 ， 材料工程（专业学位）， 2018， 硕士

【摘要】 近年来,各类电子产品与新能源汽车的快速发展使得高能量密度的电池研发变得迫切。锂金属负极由于其极高的理论比容量(3860 mAh g^-1),较低的电压平台等优势（-3.04 V相对于标准氢电极）,可广泛应用于锂金属电池、锂硫电池和锂空电池体系,逐渐引起了人们的研究兴趣,但诸多缺点限制了锂金属负极的商业化应用。如锂金属负极在循环过程中会产生锂枝晶、体积膨胀明显,不仅造成容量衰减加快,而且还会导致电池短路、热失控等安全问题。针对上述问题,本文从电极结构的角度出发制备了三维多孔铜集流体以推进锂金属负极的实际应用。首先,以商业化铜锌合金为原材料,利用线性扫描循环伏安法电化学刻蚀铜锌合金制备三维多孔铜集流体;相比于化学刻蚀法,电化学刻蚀法制备的多孔铜集流体具有均一、光滑、致密的网络结构,强度明显提高,从而提升了电极在循环过程中的稳定性;同时电化学刻蚀法制备的多孔铜集流体可以很好地保持电子导电网络,促进电子传导,有助于电化学性能的提升;电化学刻蚀法简单易行,有望实现三维多孔铜集流体的规模化生产。其次,从锂金属负极的实际应用角度出发,制备了Li@3D Cu电极应用于半电池,发现多孔铜集流体可以有效抑制锂枝晶生长,主要原因在于均一、连续的三维多孔铜集流体结构赋予了锂更多的沉积空间;三维多孔铜集流体较大的比表面积能够降低电流密度,避免电荷集中,有利于锂金属在孔道内部的均一沉积,抑制锂枝晶形成;同时均一、连续的三维多孔铜集流体能够诱导高质量SEI膜的形成,避免了SEI膜的破裂和不断生成,提高了电池的库伦效率;再者,紧凑的结构具备良好的机械性能促进了锂金属电池的循环稳定性,可以稳定循环400小时没有短路发生。最后,为了进一步提高三维多孔铜集流体的性能,发展了多种提升锂金属在多孔铜集流体内部均匀沉积的改性方法:第一,通过在多孔铜集流体孔道内修饰银颗粒改善其亲锂性,诱导锂均匀地沉积;第二,通过镀石墨烯多孔层可以增强多孔铜集流体沉积锂的空间,提升电极整体的能量密度;第三,通过聚氧化乙烯（PEO）涂层可有效改善表层电荷分布情况,减少表层锂沉积,诱导锂更倾向于沉积到三维多孔铜集流体孔道内部。利用以上方法对三维多孔铜集流体进行改性可进一步推动锂金属电池的实际应用。更多还原

【Abstract】 In recent years,the rapid development of various kinds of electronic products and new energy vehicles requires the development of high-energy density batteries urgently.Lithium metal anode gradually attracted the interest of the researchers due to its advantages of high theoretical specific capacity(3860 mAh g^-1)and the low voltage platform（-3.04 V vs standard hydrogen electrode）.Lithium metal anode can be widely used in lithium batteries,lithium sulfur battery and lithium air battery.However,shortcomings of lithium metal anode restrict its commercial application.Lithium dendrite gradually grows and its volume expansion is obvious during long cycling of battery,which not only causes the capacity attenuation but also leads to the battery short circuit,thermal runaway and other security issues.In view of the above problems,3D porous copper was prepared and applied as current collector of Li metal anode to promote its practical application.In this paper,using the commercial copper-zinc alloy as raw material,the linear sweep voltammetry electrochemical dealloying method is used to precisely regulate the three-dimensional porous copper structure.Compared to chemical dealloying method,the porous copper prepared by electrochemical etching method has a uniform,smooth and compact network structure,which helps to enhance the strength and the stability of the electrode during cycling.At the same time,it can maintain a good electronic conductive network,which promotes the conduction of electrons and improves the electrochemical performance.In addition,the method is simple and easy to use commercial Cu-Zn alloy tape as raw material,and it is expected to realize the large-scale production of 3D porous copper current collector.Secondly,based on the practical application of lithium metal anode,the Li@3D Cu anode was prepared and used in half battery,which can effectively inhibit the lithium dendrite growth.This inhibition of lithium dendrites is mainly because that a homogenous and continuous porous structure contributes to more lithium deposition space and large surface area,which avoids the charge concentration so as to inhibit the formation of lithium dendrites.At the same time,the 3D porous copper current collector with a uniform,smooth and compact network structure induces formation of high a quality SEI film,which avoids the rupture and continuous generation of SEI film,thus coulombic efficiency is enhanced.Moreover,the compact structure has good mechanical properties,which promotes the cycling stability of the lithium metal battery.The half cells can stably cycle for 400 hours without short circuit.In the end,the 3D porous copper current collector was further modified by several methods,which were found to be beneficial to inhibiting the Li dendrite growth.The first is that the electrophilic modification of 3D porous copper by silver plating can induce the deposition of lithium and promote the smooth deposition of lithium.Secondly,the coating of the porous layer of graphene can construct more space for Li deposition and increase the energy density of the whole electrode.The third is that the polymer PEO coating can effectively improve the surface charge distribution,reduce the deposition lithium on the surface,and induce lithium to be more prone to deposit into the porous copper current collector.The modifications of the 3D Cu can further promote the future application of lithium metal anode.更多还原