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Experimental Investigation and Thermodynamic Modeling of LNMO High Voltage Spinel Cathode for the LIBs

锂离子电池用 LNMO 高压尖晶石阴极的实验研究和热力学建模

基本信息

批准号：
326070248
负责人：
Dr. Dajian Li
金额：
--
依托单位：
Institut für Angewandte Materialien (IAM)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/326070248?language=en
关键词：
Experimental Investigation Thermodynamic Modeling LNMO

项目摘要

High voltage Li-Ni-Mn-O (LNMO, stoichiometric composition LiNi0.5Mn1.5O4, 4.7 V vs. Li) spinels are very promising cathode materials for Li-ion batteries (LIBs) due to the high energy densities. Consistent thermochemical and electrochemical data are urgently required for the design of power and thermal management systems of LIBs based on these new materials. Although numerous cell property investigations have been published, thermochemical (enthalpy of formation, heat capacity) and electrochemical data (entropy of reaction during charge-discharge processes) are rare. Therefore, the aim of this project is to investigate the thermochemistry and electrochemistry of LNMO spinels and to use the results to develop self-consistent analytical descriptions of the Gibbs free energy of the respective phases for the first time.The experimental studies in this proposal include the synthesis of spinel samples with selected cation ratios using the sol-gel method. Heat treatments in defined atmospheres will be used to obtain samples with different oxygen vacancy concentrations. Sample characterization will be performed using powder-XRD, ICP-OES and SEM. Redox titration techniques will be employed to determine the average oxidation state of Mn cations, allowing the calculation of oxygen vacancy concentrations. Moreover, enthalpies of formation will be measured using drop solution calorimetry, and heat capacity measurements will be conducted using different DSC devices. Battery test cells (Coin cells, Swagelok cells) will be assembled with the spinel cathode against pure Li, and will be used for potentiometric investigation to obtain the entropy changes during lithiation-delithiation process. Both LMO and LNMO spinels compositions will be investigated.A model taking the crystal structure and Wyckoff site occupancies into account (oxygen vacancy concentrations, cation mixing), will be established based on the experimental data using the Calphad approach. Lithiation-delithiation process will be simulated by modeling the relation between Gibbs energy and correct sublattice site occupations for the first time. Predictions of battery behaviors including open circuit voltages, heat generation properties, and oxygen partial pressures with temperature dependencies under varying conditions, will be performed.As the output of the current project, conditions for synthesizing LNMO spinel with improved battery performance will be proposed according to thermodynamic calculations. Meanwhile, the obtained thermodynamic models will be key contributors to the ICME development of LIBs with novel spinel cathode materials. Furthermore, the thermochemical information is essential for the battery safety and preventing hazardous phenomena such as thermal runaway and flame generation.

高压Li-Ni-Mn-O(LNMO，化学计量比LiNi0.5Mn1.5O4，4.7Vvs.Li)尖晶石具有很高的能量密度，是非常有前途的锂离子电池正极材料。为了设计基于这些新材料的LIBS的功率和热管理系统，迫切需要一致的热化学和电化学数据。尽管已经发表了大量的电池性质研究，但热化学(生成热、热容)和电化学数据(充放电过程中的反应熵)却很少。因此，本项目的目的是研究LNMO尖晶石的热化学和电化学，并首次利用这些结果对各相的吉布斯自由能进行自洽的解析描述。本项目的实验研究包括使用溶胶凝胶法合成具有选定阳离子比例的尖晶石样品。在规定的气氛中进行热处理，以获得具有不同氧空位浓度的样品。利用粉末X射线衍射仪、电感耦合等离子体发射光谱仪和扫描电子显微镜对样品进行表征。氧化还原滴定技术将被用来确定锰离子的平均氧化态，从而可以计算氧空位浓度。此外，将使用液滴溶液量热法测量生成热，并使用不同的DSC设备进行热容测量。电池测试电池(Coin电池、世伟洛克电池)将与尖晶石正极组装成纯Li，并用于电位测量，以获得锂-锂脱氢过程中的熵变化。对LMO和LNMO尖晶石的组成进行了研究，利用CALPHAD方法建立了一个考虑晶体结构和Wyackoff位占有率(氧空位浓度，阳离子混合)的模型。首次通过模拟Gibbs能量与正确的亚晶格占位之间的关系来模拟锂离子的脱硫化过程。将对电池行为进行预测，包括开路电压、发热特性和氧分压在不同条件下随温度的变化。作为本项目的输出，将根据热力学计算提出合成具有改善电池性能的LNMO尖晶石的条件。同时，所得到的热力学模型将对新型尖晶石正极材料LiBS的ICME开发起到关键作用。此外，热化学信息对于电池的安全和防止热失控和火焰产生等危险现象是必不可少的。