Li2OHI 的制备、改性及其在固态电解中的应用研究

STUDY ON THE FABRICATION AND ODIFICATION OF Li2OHI AND ITS PPLICATION IN SOLID STATE ELECTROLYTES

杨润涛

11930063

硕士

材料工程

李帅 朱金龙

2021

2021-06-11

南方科技大学

深圳

互联网的普及和计算机技术的发展使手机、平板电脑等便携式设备参与到人类生活的方方面面，因此对电池的安全性、容量、充放电速率等提出了更高的要求，目前商用的绝大部分锂离子电池均使用有机电解液，手机电池爆炸、电动汽车自燃等事故时有发生，其安全性问题亟待解决，使用固态电解质代替液态电解液有望从根本上解决锂电池的安全隐患，并且使金属锂负极的应用成为可能，又将极大的提高电池的能量密度。因此，作为固态电池最关键的部分，合成制备具有高离子电导率、宽电化学窗口、对锂稳定等综合性能优良的固态电解质是全固态锂离子电池走向成熟的关键一步。富锂反钙钛矿固态电解质因其对锂稳定、高离子电导率等优良特性而广受关注，但由于其制备方法单一且产率较低，难以推广应用。因此，本研究立足于反钙钛矿结构，引入碘元素对Li2OHX 进行晶格调控，通过对比固相烧结法与高能球磨法产物的结构与性能差异，总结反应规律，确定了Li2OHI的最优制备方法，产物纯度高、结晶度高、晶粒均匀且热稳定性好，Li2OHI在40℃电导率为10-6 S/cm，至140℃电导率达5×10-3 S/cm，离子迁移活化能为1.0525 eV，离子迁移数为85.79%，具备作为固态电解质的基础性能条件，但其电化学窗口较窄和対锂循环稳定性较差的问题尚需改进。其次，对Li2OHI 进行氟掺杂取代O-H 位点进行结构优化，初步的结构表征和性能测试显示，氟掺杂后Li2OHI 晶胞参数未发生变化，进入晶格位点后改变了氢氧键的偶极矩，使其对Li+跃迁的束缚减弱，迁移活化能降低，进一步提升了Li2OHI 体系的离子输运性能。同时，尝试采用水热法制备Li2OHI，实验证实了氢氧化锂-卤化锂体系的湿度敏感性，暴露空气后的产物为LiI·H2O，该材料在110℃以上电导率高达10-2 S/cm，离子迁移活化能仅为0.2 eV，其在固态电解质中的应用尚需进一步调研。

The popularity of the Internet and the development of computer technology have enabled portable devices such as mobile phones and tablet computers to participate in all aspects of human life. Therefore, higher requirements have been put forward on the safety, capacity, and charging and discharging rate of batteries. Most of the current commercial lithium Ion batteries all use organic electrolytes, and accidents such as mobile phone battery explosions and spontaneous combustion of electric vehicles need to be solved urgently. The use of solid electrolytes instead of liquid electrolytes is expected to fundamentally solve the safety hazards of lithium batteries and make the application of metal lithium as negative electrodes becomes possible, which will greatly increase the energy density of the battery. Therefore, as the most critical part of solid-state batteries, the synthesis and preparation of solid-state electrolytes with high ion conductivity, broad electrochemical stability window, and stability to lithium are a key step towards the maturity of all-solid-state lithium-ion batteries.Lithium-rich anti-perovskite solid electrolyte has attracted wide attention due to its excellent characteristics such as stability to lithium and high ionic conductivity. However, due to its single preparation method and low yield, it is difficult to popularize and apply. Therefore, this study is based on the anti-perovskite structure, introducing iodine to adjust the crystal lattice of Li2OHX, compares the structure and performance of the solid-phase sintering method and the high-energy ball milling method, summarizes the reaction law, and determines the optimal preparation of Li2OHI Method, the product has high purity, high crystallinity, uniform crystal grains and good thermal stability. The conductivity of Li2OHI at 40°C is 10 -6 S/cm, and the conductivity at 140°C is 5×10 -3 S/cm. The ion migration activation energy is 1.0525 eV, and the ion migration number is 85.79%. It has the basic performance conditions as a solid electrolyte, but its electrochemical window is narrow and the problems of poor lithium cycle stability need to be improved.Secondly, fluorine-doped Li2OHI was used to replace O-H sites for structural optimization. Preliminary structural characterization and performance testing showed that the Li2OHI unit cell parameters did not change after fluorine doping. After entering the lattice sites, the hydrogen-oxygen bond pairs were changed. The polar moment weakens the binding of Li+ transition and reduces the migration activation energy, which further improves the ion transport performance of the Li2OHI system.At the same time, an attempt was made to prepare Li2OHI by hydrothermal method. The experiment confirmed the humidity sensitivity of the lithium hydroxide-lithium halide system. The product after exposure to air is LiI·H2O. The conductivity of this material is as high as 10 -2 S/cm above 110°C.The activation energy of ion migration is only 0.2 eV, and its application in solid electrolytes needs further investigation.

锂离子电池 固态电解质 反钙钛矿材料 Li2OHI 合成工艺

lithium-ion battery solid state electrolyte anti-perovskite material Li2OHI synthesis process

中文

独立培养

南方科技大学

杨润涛. Li2OHI 的制备、改性及其在固态电解中的应用研究[D]. 深圳. 南方科技大学,2021.