兰州大学机构库 >材料与能源学院
基于离子径迹技术的锂负极框架研究
Alternative TitleIon Track Technology-Based Frameworks for Lithium Anodes
朱晓霞
Subtype博士
Thesis Advisor彭勇
2023-08-24
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline物理学
Keyword离子径迹技术 Ion track technology 模板法 Template method 锂负极 Lithium anode 三维纳米金属框架 Three-dimensional nano-metal framework 亲锂位点 Lithiophilic site
Abstract

随着消费类电子产品和新能源交通工具等的快速发展,人们对高能量密度储能系统的需求日益增大,而传统的锂离子电池石墨负极已然接近其理论极限(372 mAh g-1)。因此,急需寻找新型负极材料以满足人们对高性能储能系统的需求。金属锂由于具有极高的理论容量(3860 mAh g-1)、低电化学电位(-3.04 V,相对于标准氢电极)、低密度等优点,一直被认为是“理想负极材料”。然而,金属锂负极在反复电镀/剥离的过程中容易产生枝晶生长、体积膨胀等问题,从而造成电池短路、容量减小和库仑效率降低等一系列问题,存在安全隐患。

本论文针对下一代高比能量二次电池锂金属负极枝晶生长和体积膨胀等问题,利用离子径迹技术的特点,设计构建了高孔隙率、低孔道迂曲度的纳米金属框架,系统研究了框架结构设计、材料选择、框架纳米梁修饰对框架复合电极电化学循环性能的影响和锂金属均匀沉积的调控机制,具体如下:

(1)三维纳米金属框架设计与制备研究。设计了四向、五向、层级五向支撑三种纳米框架构型,基于兰州重离子研究装置(HIRFL),利用多轮次、多方向入射的离子辐照,在三维空间构建了离子径迹结构。通过径迹蚀刻得到了具有三维孔道阵列的模板。最后利用电化学沉积,分别制备了金/铜/镍三维纳米金属框架,探索了金/铜/镍三种材质的纳米框架制备方法、工艺和参数,系统表征分析了三维纳米金属框架的形貌、成分和孔隙率等。综合分析锂金属负极的理想框架要求和上述框架结构的特点,本论文选择以45°四向支撑纳米框架构型作为锂负极框架构型电化学性能的主要研究对象。

(2)亲锂性金纳米框架的电化学循环研究。利用2032扣式电池,研究了亲锂四向支撑金框架(简称3D Au)对锂沉积形貌和锂负极电化学性能的影响。鉴于金元素化学性质稳定,不易受电解液成分的影响,且对其作为锂负极框架的研究不够深入,优先选取亲锂性的金纳米框架进行电化学性能研究,发现金纳米框架复合负极的深充深放循环性能较差,阐明了锂与金的合金化反应造成的框架结构破坏是电极循环性能差的主要原因。为此,进一步利用葡萄糖碳化技术对金框架做了处理,部分隔离了金纳米梁与锂合金化反应的界面。结果显示,碳化后的金框架(3D Au@C)显著提升了复合负极(3D Au@C-Li)的循环寿命、稳定性、深充深放、快充快放等性能表现,将对称电池循环寿命从600 h提高到1000 h。以上结果表明,对于完全亲锂的纳米框架材料,合金化导致的结构破坏不利于其复合锂负极的循环稳定性和长循环寿命。因此,需要采用非亲锂材质的锂负极框架结构,以获得稳定的循环性能。

(3)非亲锂性铜纳米框架的电化学循环性能研究。利用离子径迹技术构建了铜纳米框架(3D Cu),通过对不同容量的锂沉积形貌研究,说明了铜框架纳米梁的稳定性和其对枝晶的抑制效果。通过COMSOL Multiphysics有限元模拟,进一步阐明了纳米框架结构的低表面电荷密度导致的电场均匀化,是纳米框架抑制枝晶生长的主要原因。此外,对3D Cu-Li对称电池的稳定循环性能、深充深放能力、快充快放表现等方面的电化学循环性能做了系统的研究。结果表明,3D Cu-Li对称电池的循环寿命超过了1650 h,远远超越3D Au-Li和3D Au@C-Li。这证明了稳定的锂负极框架有利于延长电池循环寿命。进一步研究发现3D Cu-Li对称电池在1000 h后,极化逐渐增大,电池循环稳定性变差。因此,需要在铜框架纳米梁表面修饰亲锂位点,以降低锂金属形核过电位,提高循环性能。

(4)亲锂位点修饰的铜纳米复合框架的电化学循环性能研究。为了降低锂金属的形核过电位,诱导锂金属在框架内部均匀沉积,提出了利用置换反应在纳米梁表面修饰亲锂位点的方法,得到了纳米梁表面均匀修饰了亲锂位点的铜纳米复合框架(3D Cu@CuAux)。借助原位光学显微镜观察了锂金属在铜纳米复合框架中的沉积行为,证明了锂金属优先在网格内部沉积且没有锂枝晶的产生和体积膨胀。利用电池循环测试,研究了亲锂颗粒CuAux对铜纳米复合框架锂负极(3D Cu@CuAux-Li)电化学性能的影响。结果表明,与3D Cu-Li相比,3D Cu@CuAux-Li的电化学性能有显著的提升,其对称电池稳定循环寿命超过了2100 h且具有更小的极化,说明了亲锂因子的引入,诱导锂金属均匀形核,降低了锂的形核过电位,实现了复合电极电化学性能的进一步提升。通过对3D Cu@CuAux-Li电极在醚类电解液和碳酸酯类电解液中的库伦效率测试以及3D Cu@CuAux-Li负极与高质量负载LiFePO4与Li2(Ni0.8Co0.1Mn0.1)O2正极的全电池循环测试,进一步阐明了铜纳米复合框架的广泛适应性。此外,利用磁控溅射方法实现了Zn、Sn等亲锂因子的修饰,拓展了3D Cu低成本颗粒修饰方法。

总的来说,本论文针对锂负极循环稳定性的问题,发挥离子径迹技术的优势,设计构建了三维纳米金属框架锂负极,研究了金属框架的材质、空间构型和亲锂性等因素对锂沉积形貌和锂负极循环性能的影响。研究表明,亲锂性材质的框架有利于高容量负载,但不利于框架结构的稳定性,非亲锂性材质可以保持框架的稳定性,但存在极化逐渐增大循环稳定性变差等问题。而由亲锂颗粒和非亲锂框架组合的复合纳米框架,即能保持框架稳定又能减小极化,因此,亲锂颗粒的引入是诱导锂金属均匀沉积、提升负极电化学性能的关键。此外,框架计构的高孔隙率、低孔道迂曲度,促进了电场的均匀化,也是负极性能提升的关键因素。本论文研究结果对探寻金属负极理想框架构型和高性能锂电池负极材料具有较好的参考价值和指导意义。

 

关键词:离子径迹技术,模板法,锂负极,三维纳米金属框架,亲锂位点

Other Abstract

With the rapid development of consumer electronics and new energy transportation, people's demand for high energy density energy storage systems is increasing. However, the traditional graphite anode electrode of lithium-ion batteries has approached its theoretical limit (372 mAh g-1). Therefore, there is an urgent need to discover novel anode materials to meet the demand for high performance energy storage systems. Lithium metal has been considered as an "ideal anode" due to its extremely high theoretical capacity (3860 mAh g-1), low electrochemical potential (-3.04 V compared to standard hydrogen electrode) and low density, etc. However, the lithium metal anode electrode is prone to dendrite growth and volume expansion in the process of repeated plating/stripping, which result in a series of problems such as short circuit, capacity reduction and Coulomb efficiency reduction of the battery, causing safety risks.

In this dissertation, we aim at the problems of dendrite growth and volume expansion of next-generation lithium anode electrode with high energy density, a nano-metal framework with high porosity and low channel tortuosity is designed and constructed by utilizing the characteristics of ion track technology. The influences of framework structure design, material selection and framework nano-beam modification on the electrochemical cycling performance of the framework composite electrode and the mechanism of regulating the uniform deposition of lithium metal are systematically investigated. Detailed information is as follows:

(1) Study of the design and fabrication of three-dimensional nano-metal frameworks. Based on The Heavy Ion Research Facility in LanZhou (HIRFL), the ion track structure was constructed in three-dimensional space by multi-round and multi-directional incident ion irradiation. The template with three-dimensional channel array was obtained by track etching. Finally, three-dimensional gold/copper/nickel frameworks were prepared by electrochemical deposition, and the preparation methods, processes and parameters of gold/copper/nickel frameworks were investigated. The morphology, composition and porosity of the three-dimensional frameworks were systematically characterised and analysed. Upon a comprehensive analysis of the requirements for ideal frames of the lithium metal anode and the characteristics of the above frame structures, the 45° four-way supported framework configuration was selected as the main research object for the electrochemical performance of the lithium anode frame configuration.

(2) Study of the electrochemical cycling of lithiophilic gold nano-framework. The effect of lithiophilic four-way supported gold framework (3D Au) on the deposition morphology and electrochemical performance of lithium anode was investigated using 2032 button cell battery. Considering the stable chemical properties of Au, which is not easily affected by the composition of electrolytes, and the lack of in-depth research on its use as lithium anode electrode framework, the lithiophilic gold framework was chosen to study the electrochemical performance. It was found that the deep charge and deep discharge cycle performance of gold framework composite anode electrode is poor. The main reason for the poor cycling performance of the electrode was the failure of the framework structure caused by the alloying reaction of lithium and gold. Therefore, the gold framework was further treated by glucose carbonisation technology, and the reaction interface between the gold and the lithium was partially isolated. The results showed that the carbonised gold framework (3D Au@C) significantly improved the performances of cycle life, stability, deep charge and deep discharge, fast charge and fast discharge of the composite anode electrode (3D Au@C-Li), and increased the cycle life of the symmetrical battery from 600 hours to 1000 hours. The above results show that the structural damage caused by alloying is not conducive to the cycle stability and long cycle life of the lithium anode composite for the composite lithiophilic framework materials. Therefore, it is necessary to use a lithium anode framework structure of non-lithiophilic material to achieve stable cycle performance.

(3) Study of the electrochemical cycle performance of non-lithiophilic copper frameworks. Copper frameworks (3D-Cu) were constructed by ion-track technology. The stability of copper frameworks and their inhibition effect on dendrites were demonstrated by studying the morphology of lithium deposition with different capacities. The COMSOL Multiphysics finite element simulation, demonstrated that the electric field homogenisation caused by the low surface charge density of the framework structure was the main reason for inhibiting the dendrite growth of the framework. In addition, the electrochemical cycle performance of the 3D Cu-Li symmetric battery was systematically investigated in terms of stable cycle performance, deep charge and deep discharge capacity, fast charge and fast discharge performance. The results showed that the 3D Cu-Li symmetric battery has a cycle life of more than 1650 hours, which greatly outperforms the 3D Au-Li and 3D Au@C-Li, demonstrating that the stable lithium anode framework is conducive to extending the battery cycle life. Further investigation showed that the polarization of the 3D Cu-Li symmetric battery gradually increased after 1000 hours, and the cycle stability of the battery became worse. Therefore, it is necessary to modify the surface of copper nanobeams with lithopghilic sites on to reduce the lithium metal nucleation overpotential and improve the cycle performance.

(4) Study on the electrochemical cycle performance of copper nanocomposite frameworks modified with lithiophilic sites. In order to reduce the nucleation overpotential of lithium metal and to induce the uniform deposition of lithium metal inside the framework, a substitute reaction was proposed to modify the lithiophilic sites on the surface of nano-beams. A copper nanocomposite framework with uniform modification of lithiophilic sites on the surface of nanobeams was obtained (3D Cu@CuAux). The deposition behaviour of lithium metal in copper nanocomposite frameworks was observed by in situ optical microscopy and it was found that lithium metal preferentially deposited in the interior of the lattice without the formation of lithium dendrites and volume expansion. The effect of lithiophilic particles CuAux on the electrochemical performance of copper nanocomposite framework lithium anode (3D Cu@CuAux-Li) was investigated by battery cycling test. The results showed that the electrochemical performance of 3D Cu@CuAux-Li is significantly improved compared to 3D Cu-Li. The stable cycle life of the symmetrical battery exceeded 2100 hours and the polarisation was smaller, indicating that the introduction of lithiophilic sites induced uniform nucleation of lithium metal and reduced the overpotential of lithium nucleation. The electrochemical performance of the composite electrode was further improved. By testing the Coulomb efficiency of 3D Cu@CuAux-Li electrode in ether electrolyte and carbonate electrolyte, as well as full battery cycle test of 3D Cu@CuAux-Li anode electrode and high mass loaded LiFePO4 and Li2(Ni0.8Co0.1Mn0.1)O2 cathode electrode, the wide adaptability of copper nanocomposite framework was further illustrated. In addition, the magnetron sputtering method was utilized to modify Zn, Sn and other lithiophilic sites, and the low-cost 3D Cu particle modification method was extended.

In summary, this dissertation aims at the problem of cycle stability of lithium anode electrode, takes advantages of ion track technology to design and construct three-dimensional nano-metal framework lithium anode electrode, and studies the influences of metal framework material, spatial configuration and lithiophile factors on lithium deposition morphology and lithium anode electrode cycle performance. The research demonstrates that the framework of lipophilic materials is conducive to high-capacity load, but not conducive to the stability of the framework structure. Non-lipophilic materials can maintain the stability of the framework, but there are problems such as increasing polarization and deteriorating cycle stability. The composite framework composed of lipophilic particles and non-lipophilic frameworks can maintain the stability of the framework and reduce the polarization. Therefore, the introduction of lipophilic particles is the key factor to induce the uniform deposition of lithium metal and improve the electrochemical performance of the anode electrode. In addition, the high porosity and low tortuosity of the framework structure promote the homogenisation of the electric field, which is also a key factor for the improved performance of the anode electrode. The above results have good guiding significance for the research of the ideal framework configuration of the metal anode electrode and the anode electrode materials of high-performance lithium batteries.

 

Keywords: Ion track technology, Template method, Lithium anode, Three-dimensional nano-metal framework, Lithiophilic site

MOST Discipline Catalogue理学 - 物理学 - 凝聚态物理
URL查看原文
Language中文
Other Code262010_120190907140
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/539791
Collection材料与能源学院
Affiliation
兰州大学材料与能源学院
Recommended Citation
GB/T 7714
朱晓霞. 基于离子径迹技术的锂负极框架研究[D]. 兰州. 兰州大学,2023.
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