【作者】 张超群；

【导师】 娄帅锋；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2023， 硕士

【摘要】 锂离子电池自商业化以来蓬勃发展,其大规模应用已从消费类电子产品延伸到电动汽车、电网储能、国防与空间技术等领域。传统锂离子电池在极端工况下,易发生由电解液泄漏、分解引发的起火、爆炸等安全问题。此外,其能量密度已达到理论上限,无法满足电动汽车和电网储能日益增长的应用需求。因此,兼具高能量密度、高安全性的全固态锂电池有望从根本上突破锂离子电池的技术瓶颈。本文在总结全固态锂电池反应动力学的仿真模拟、电极尺度离子传输及界面反应行为的基础上,以开发高比能、长循环的硫化物基全固态锂电池为研究目标,针对复合正极的结构设计与界面调控开展了以下研究工作:（1）系统研究了硫化物基固态电池复合正极Li⁺传输动力学机制及电极结构设计策略。基于全固态电池的结构特征,开发了包含颗粒尺度的三维异构电化学模型,考察电解质种类(硫化物固态电解质Li₆PS₅Cl,LPSCl、氧化物固态电解质Li_6.4La₃Zr_1.4Ta_0.6O₁₂,LLZTO)对固态电池电化学性能的影响。结果显示,硫化物固态电池的放电容量约为氧化物固态电池的2.26倍,活性颗粒内部固相Li⁺浓度远高于氧化物固态电池。以硫化物固态电池为研究主体,提出迂曲梯度模型电极结构,进一步提升全固态电池的电化学性能。（2）系统研究了硫化物基固态电池的界面（电）化学降解行为及改性策略。基于Li Ni_0.8Co_0.1Mn_0.1O₂（NCM811）模型正极材料,利用湿化学方法在其前驱体表面构筑含氧空位缺陷的钙钛矿La₄Ni Li O_8-x（LNLO）包覆层,经过热处理后得到LNLO@NCM811。详细研究了包覆层对固态电池电化学性能、界面（电）化学反应行为的影响。结果显示,LNLO包覆层抑制了LPSCl电解质的分解,稳定的氧空位缺陷有效缓解了NCM811在高压下的晶格氧逸出,从根本上稳定了NCM811/LPSCl界面,显著降低界面电阻,进而改善了硫化物基全固态电池的电化学性能。LNLO@NCM811材料的首次放电比容量提升至157.0 m Ah/g,在4.5 V高截止电压下循环100圈,容量保持率为78.6%。更多还原

【Abstract】 Lithium-ion batteries have flourished since commercialization,and their large-scale applications have extended from consumer electronics to electric vehicles,grid energy storage,defense and space technology.However,in extreme operating conditions,traditional lithium-ion batteries have safety problems such as fires and explosions caused by organic electrolyte leakage and decomposition.In addition,the energy density of commercial lithium-ion batteries has reached the theoretical upper limit,which is difficult to meet the growing application demand for electric vehicles and grid energy storage.Therefore,all-solid-state lithium metal batteries with high energy density and high safety are expected to break the technical bottlenecks of traditional lithium-ion batteries fundamentally.Based on the summary of the simulation of reaction kinetics,electrode-scale ion transport,and interfacial reaction behavior of all-solid-state lithium metal batteries,this thesis aimed to develop high specific energy and long cycle life sulfide-based all-solid-state batteries,and conducted the following research work on structure design and interface modification of composite cathode:（1）The mechanism of Li⁺transport kinetics and electrode structure design strategy for the composite cathode of sulfide-based solid-state batteries were systematically studied.Based on the structural characteristics of the all-solid-state batteries,a three-dimensional heterogeneous electrochemical model including particle scale was developed to investigate the influence of electrolyte types(sulfide solid-state electrolyte Li₆PS₅Cl,LPSCl and oxide solid-state electrolyte Li_6.4La₃Zr_1.4Ta_0.6O₁₂,LLZTO)on the electrochemical performance of the solid-state batteries.The results showed that the discharge capacity of the sulfide-based solid-state batteries was about 2.26 times as high as that of the oxide-based solid-state batteries,and the solid phase Li⁺concentration of the active particles was much higher.Taking sulfide solid-state batteries as the research object,the tortuosity gradient model electrode structure was proposed to further improve the electrochemical performance of all-solid-state batteries.（2）The interfacial（electro）chemical degradation behavior and modification strategy of sulfide-based solid-state batteries were systematically studied.Based on the Li Ni_0.8Co_0.1Mn_0.1O₂（NCM811）model cathode material,the perovskite La₄Ni Li O_8-x（LNLO）coating layer containing oxygen vacancy defects was constructed on the surface of its precursor by wet chemical approach,and LNLO@NCM811 was obtained after heat treatment.The effect of the coating layer on the electrochemical performance and interfacial（electro）chemical reaction behavior of solid-state batteries were further studied.The results showed that the LNLO coating layer inhibited the decomposition of LPSCl,and the stable oxygen vacancy defects effectively mitigated the lattice oxygen evolution of NCM811 at the high cut-off voltage,which fundamentally stabilized the NCM811/LPSCl interface and significantly reduced the interfacial resistance,thus the electrochemical performance of the sulfide-based all-solid-state batteries was improved.Therefore,the LNLO@NCM811 material exhibited a higher discharge specific capacity of 157.0m Ah/g,the capacity retention was 78.6%after 100 cycles at a high cut-off voltage of 4.5 V.更多还原