【作者】 李杜；

【导师】 张冠华； 刘翊；

【作者基本信息】 湖南大学 ， 机械工程（专业学位）， 2022， 硕士

【摘要】 近年来,各行各业科学技术日新月异,使得能源的需求量与日俱增,开发新型、高效、低成本、高能量密度的二次电池体系,是解决未来大规模电能存储应用中的重要途径之一。锂金属缘于其理想的理论比容量(3 860 mAh g-1)、低密度(0.534 g cm-3)、较低的电化学电位(-3.04 V vs标准氢电极)等优势,使其在高能量密度能源存储系统的研发中始终占据极为重要的地位,这也是众多科研工作者始终致力于锂金属电池(LMBs)研究的重要原因之一。然而,使用锂负极或锂合金负极时,其诸多缺点是不容忽视的。例如,在充放电循环时容易生长锂枝晶、出现锂腐蚀、产生“死锂”以及体积膨胀等现象。这些问题会造成电池短路以及容量的迅速衰减甚至爆炸,因此,以锂金属作为负极的商业化应用面临着极大的阻碍。鉴于以上问题,本文对锂负极集流体进行了一系列结构设计,致力于推进LMBs的实际应用,具体研究如下:(1)利用光刻法、电沉积法等微纳加工工艺制备出蜂窝状铜金属微网格(CMM)作为集流体基底。该蜂窝微网格兼具超薄、超轻、超柔、高导电性等特征,微米级别的网格结构能调控电场分布。以CMM为基底,结合湿化学刻蚀法、退火处理,在CMM表面修饰一层亲锂性CuxO(x=1,2)纳米线(CMMC)。通过将蜂窝微网格和纳米线三维结构的优势相集成,与纯铜箔和纯铜微网格相比,CMMC在电化学测试中表现出了更加优异的性能。在半电池测试中,CMMC电极以99%的高库伦效率稳定循环了 2 000个周期,CMMC-Li ‖CMMC-Li对称电池以稳定的低过电位12 mV工作2 000 h。为了证明CMMC-Li电极的实际应用价值,将其与高负载LiFePO4(8.56 mg cm-2)正极进行匹配时,CMMC-Li‖LiFePO4全电池在0.2 C下展现了 166.6 mAh g-1的高容量。(2)以CMM为基底,结合湿化学刻蚀法、氢气还原法在CMM表面附着一层铜纳米颗粒(CMM@Cu)。利用连续电沉积法,依次电镀金属锌、锂,获得亲锂性锂锌合金棒修饰的CMM@Cu薄膜(CMC-ZL)。CMC-ZL负极由于其特殊的蜂窝微网格结构和锂锌合金棒低的成核过电位,在LMBs中展现出非凡的电化学性能。对称电池测试中,CMC-ZL‖CMC-ZL始终保持稳定的电压剖面,以超低的过电位稳定循环近1 500 h。与高负载LiFePO4(10 mg cm-2)正极进行匹配时,在0.2 C下展示了 140 mAh g-1的高容量。更多还原

【Abstract】 Recently,the rapid changes in technology in all walks of life have increased the demand for energy.The development of new,high-efficiency,low-cost,and highenergy-density secondary battery systems is an important method to solve large-scale electric energy storage applications in the future.Due to the ideal theoretical specific capacity(3 860 mAh g-1),low density(0.534 g cm-3),and lower electrochemical potential(-3.04 V vs standard hydrogen electrode)of lithium metal,the research and development of high-energy-density energy storage systems has always occupied an extremely significant status,which is one of the important reasons why many researchers have always devoted themselves to the research of lithium metal batteries(LMBs).However,when lithium metal or lithium alloy is used as the anode,the disadvantages should not be ignored.For example,the lithium dendritic growth,lithium corrosion,dead lithium and volume expansion during the charge-discharge process.These problems can cause short circuits,rapid decay of battery capacity and even explosions,so the commercial use of lithium metal as an anode is greatly limited.To deal with above difficulties,this paper carries out several structural designs for the current collector of lithium anode,so as to promote the practical application in our life.The specific research is as follows:(1)Honeycomb copper metal micromesh(CMM)are prepared by micro-nano processing techniques such as photolithography and electrodeposition as the current collector substrate.The honeycomb mesh has the characteristics of ultra-thin,ultralight,ultra-flexible,and high conductivity,and the micron-level grid structure can control the electric field distribution.A layer of lithiophilic CuxO nanowires are modified on the surface of CMM(CMMC)by combining the wet chemical etching method and annealing treatment with the CMM as the substrate.By integrating the advantages of the honeycomb mesh and the nanowires three-dimensional structure,CMMC shows more excellent performance in electrochemical tests compared with pure copper foil and pure CMM.In the half-cell test,the CMMC electrode cycles stably for 2 000 cycles with a high Coulombic efficiency of 99%,and the CMMC-Li‖CMMC-Li symmetric cell operates with a stable low overpotential of 12 mV for 2 000 h.To demonstrate the practical application value of the CMMC-Li electrode,a CMMCLi‖LiFePO4 full cell exhibits a high capacity of 166.6 mAh g-1 at 0.2 C when it is matched with a highly loaded LiFePO4(8.56 mg cm-2)cathode.(2)A layer of copper nanoparticles(CMM@Cu)are attached to the surface of CMM by combining the wet chemical etching method and the hydrogen reduction method with the CMM as the substrate.The CMM@Cu thin film(CMC-ZL)decorated with lithiophilic lithium-zinc alloy rods are obtained by electroplating metal zinc and lithium in sequence by the continuous electrodeposition method.The CMC-ZL anode exhibits extraordinary electrochemical performance in LMBs due to its special honeycomb grid structure and low nucleation overpotential of Li-Zn alloy rods.In the symmetrical battery test,CMC-ZLIICMC-ZL always maintains a stable voltage profile and cycles stably for nearly 1 500 h with ultra-low overpotential.When matched with a highly loaded LiFePO4(10 mg cm-2)cathode,a high capacity of 140 mAh g-1 is demonstrated at 0.2 C.更多还原