【作者】 郭春；

【导师】 田忠良；

【作者基本信息】 中南大学 ， 有色金属冶金， 2022， 硕士

【摘要】 以锌二次电池为代表的碱性水系电池具有高能量密度、高安全性、低成本等优势,被认为是一种非常具有应用前景的绿色储能装置。然而锌负极在充放电过程中,不可避免地发生枝晶生长和析氢副反应,导致锌二次电池的循环性能和倍率性能变差,这也成为限制其商业化应用的关键。针对上述问题,本文采用水热-煅烧工艺制备了一种具有独特核壳结构的锌负极用ZnO@C/Bi复合材料:壳层为镶嵌高析氢过电位金属Bi的多孔C/Bi复合材料,内核为ZnO,并分析了材料的形成机理,研究了水热工艺和热处理工艺对ZnO@C/Bi材料组成与结构的影响;在此基础上,研究了ZnO@C/Bi材料组成与结构对其电化学性能的影响。主要结论如下:（1）揭示了核壳结构ZnO@C/Bi复合材料的形成机理:水热过程葡萄糖（glu）中氧原子与Bi（NO₃）₃中Bi原子络合形成以glu/Bi（NO₃）₃络合物包覆ZnO的ZnO@glu/Bi（NO₃）₃材料;保护性气氛下,glu将Bi³⁺还原为Bi的同时被碳化,包覆层由glu/Bi（NO₃）₃络合物转变为镶嵌有金属Bi的C/Bi材料,形成核壳结构ZnO@C/Bi复合材料。（2）获得了不同水热工艺与热处理条件下ZnO@C/Bi材料的结构与电化学性能,优化了材料的制备工艺。在水热温度200℃、时间6 h和煅烧温度600℃、时间5 h的保护性气氛下,可获得包覆层厚度一致、Bi均匀分布的核壳结构ZnO@C/Bi复合材料。其作为锌负极活性物质构建电池时,在1 C倍率下循环230圈后的放电比容量为547.4 m Ah g^-1,容量保持率为83.06%,其平均放电比容量达593.6 m Ah g^-1。（3）获得了ZnO@C/Bi复合材料组成对其电化学性能的影响规律,确定了性能良好的材料组成:Bi含量为5.66%、碳包覆层厚度为14.4 nm、ZnO粒径为200 nm。当以该组成的ZnO@C/Bi材料作为锌负极活性物质构建电池时,在1 C倍率下稳定循环480圈后,放电比容量仍达527.1 m Ah g^-1,容量保持率为79.98%,其平均放电比容量为589.9 m Ah g^-1。图66幅,表4个,参考文献112篇更多还原

【Abstract】 Alkaline aqueous battery represented by zinc secondary battery is considered as a green energy storage device with great application prospect owing to its high energy density,high safety and low cost.However,dendrite growth and hydrogen evolution side reactions inevitably occur during the charging and discharging process,which leads to poor cycle performance and rate performance of zinc secondary batteries.It is the key challenge for the commercial application of zinc secondary batteries.In view of the above problems,this paper prepared a unique core-shell structure of ZnO@C/Bi composite for zinc anode by hydrothermal and susequently calcination process,which the shell is porous C/Bi composite inlaid with high hydrogen evolution overpotential metal Bi and the core is ZnO.Furthermore,the forming mechanism of the ZnO@C/Bi materials was analyzed,and the influence of hydrothermal process and heat treatment process on the composition and structure of ZnO@C/Bi material were also studied.On the basis,the effects of composition and structure of ZnO@C/Bi on its electrochemical properties were further studied.The main conclusions are as follows:（1）The formation mechanism of ZnO@C/Bi composite with core-shell structure was revealed:The oxygen atoms in glucose（Glu）complex with Bi atoms in Bi（NO₃）₃ to form a coating layer of glu/Bi（NO₃）₃complex,which coated with ZnO to form ZnO@glu/Bi（NO₃）₃ materials.In a protective atmosphere,glu reduces Bi³⁺to Bi and glu is carbonized at the same time.The coating layer is transformed from glu/Bi（NO₃）₃complex to C/Bi composites embedded with metal Bi,and the core-shell structure ZnO@C/Bi composites are formed.（2）The structure and electrochemical properties of ZnO@C/Bi materials were obtained under different hydrothermal processes and heat treatment conditions,and the preparation process of the materials was optimized.The core-shell structure ZnO@C/Bi composites with uniform coating thickness and uniform Bi distribution can be obtained under the protective atmosphere of hydrothermal temperature of 200℃for 6 h and heat treatment temperature of 600℃for 5 h.When used as the active sustances of zinc anode and built a battery,the discharge specific capacity is 547.4 m Ah g^-1 with a capacity retention rate of 83.06%after 230 cycles at 1 C.And the average discharge specific capacity reaches to 593.6 m Ah g^-1.（3）The influence of the composition of ZnO@C/Bi composite on its electrochemical properties was obtained,and the composition of the materials with good performance was determined as follows:Bi content is5.66%,carbon layer thickness is 14.4 nm,ZnO particle size is 200 nm.When using the composed ZnO@C/Bi materials as the zinc anode active substances and building a battery,the specific discharge capacity reaches527.1 m Ah g^-1 with a capacity retention rate of 79.98%after 480 cycles at1 C.And the average discharge specific capacity of the battery is 589.9m Ah g^-1.更多还原