锂离子电池中的隔膜虽不直接参与电化学反应但对电池的综合性能影响重大。聚乙烯（PE）隔膜技术路线成熟，是目前主流商用电池隔膜之一，为了改善隔膜的热稳定性和力学性能，工业界主要采用对隔膜进行涂覆改性的策略。勃姆石硬度小、成本低、涂覆性好，是当前主流的PE隔膜涂层材料。但目前商用勃姆石主要采用水热法制备，呈现纳米板状结构、工艺复杂且合成形貌单一，比表面积较小，对电解液的吸附浸润性差，且无法构造均匀的孔隙结构来改善锂离子通量不均匀的问题。为了解决上述问题，本论文利用简单的合成工艺，制备了不同形貌结构的勃姆石，将其作为涂层材料，提升了PE隔膜对电解液的吸附浸润性，并构造均匀的孔隙结构来诱导锂离子均匀性沉积，进而优化了电池的电化学性能。本论文首先结合氢氧化铝的热失重曲线，通过直接热处理法实现了高比表面积多孔勃姆石的快速制备。将多孔勃姆石均匀平整涂覆于PE隔膜上，优化了隔膜的高温稳定性和力学性能。接触角测试结果显示，相较于商用水热法制备的块状勃姆石，热处理多孔勃姆石涂层对电解液的吸附浸润能力明显提升；而隔膜对电解液吸附浸润性提升为电池带来更优异的反应动力学，加快锂离子传质过程，组装电池的倍率与循环性能均有提升。利用高负载磷酸铁锂极片作为正极、金属锂片作为负极，由多孔勃姆石涂层隔膜组装的电池在1 C电流密度的测试条件下循环100圈后仍然具有146.6 mAh·g-1的放电比容量，相比于首次放电，容量保持率高达94%，并且库伦效率保持在99%以上。此外本论文通过快速水热反应，成功合成出形貌均匀、分散性好的勃姆石纳米棒。将勃姆石纳米棒均匀致密涂覆于PE隔膜表面，接触角测试结果表明，涂层显著提升了隔膜对电解液的吸附浸润能力，进而有助于加速电池的电化学反应动力学，组装电池在测试中展现了优异的倍率与循环性能。进一步对比发现涂有勃姆石纳米棒的隔膜表面和内部的孔隙分布更加均匀，从而有助于解决锂通量不均匀的问题，诱导锂离子均匀沉积。由勃姆石纳米棒涂层改性的PE隔膜和金属锂片装备的锂||锂对称电池在2 mA·cm-2与2 mAh·cm-2的测试条件下，可以实现长达500 h的稳定循环，并保持较小的电压极化。

Although the Lithium-ion battery separator does not directly participate in actual electrochemical reaction, it has a significant impact on the overall performance of the battery. The technical route of polyethylene (PE) separator is mature and it is one of the current mainstream commercial battery separators. In order to improve the thermal stability and mechanical properties of the separator, the industry mainly adopts the strategy of coating and modifying the separator. Boehmite has low hardness, low cost and good coating properties. It is the current mainstream commercial PE separator coating material. But currently, the commercial production of boehmite mainly uses hydrothermal method, which presents a nano-plate-like structure, with complex processes and a single synthetic morphology, resulting in a relatively small surface area, poor adsorption and wettability for the electrolyte, and unable to construct a uniform pore structure to improve the uneven lithium ion flux. In order to solve the above problems, this thesis uses simple synthesis processes to prepare boehmite with different morphological structures and uses them as separator coating materials to improve the adsorption wettability of PE separator for the electrolyte, and construct a uniform pore structure to improve the problem of uneven lithium ion flux, thereby enhancing the electrochemical performance of the battery.This thesis first combines the thermogravimetric curve of aluminum hydroxide and achieves rapid preparation of high specific surface area porous boehmite through direct heat treatment method. The uniform and flat coating of porous boehmite on the PE separator improved the high temperature resistance stability and mechanical properties of the separator. The contact angle test results show that compared with the commercial plate-shaped boehmite prepared by the hydrothermal method, the heat-treated porous boehmite coating significantly improves the adsorption and wettability of the electrolyte; The improved electrolyte adsorption and wettability brings better reaction kinetics to the separator, speeds up the lithium ion mass transfer process, and improves the battery rate and cycle performance. Using a commercial high-load LiFePO4 pole piece as the positive electrode, the battery assembled with a porous boehmite-coated separator still has a specific discharge capacity of 146.6 mAh·g-1 after 100 cycles at 1 C, the capacity retention rate is as high as 94%, and the Coulomb efficiency remains above 99%.In addition, this thesis successfully synthesized boehmite nanorods with uniform morphology and good dispersion through rapid hydrothermal reaction. The boehmite nanorods on the surface of the PE separator can achieve uniform and dense coating. Contact angle test results show that its ability to adsorb and wet the electrolyte is significantly improved. The improved electrolyte adsorption and wettability brings better reaction kinetics, accelerates the lithium ion mass transfer process, and improves the rate and cycle performance of the assembled battery. Further comparison found that the surface and internal pores of the separator coated with boehmite nanorods were more uniform, which helped to alleviate the problem of uneven lithium flux and induce uniform deposition of lithium ions. Li||Li symmetrical batteries equipped with boehmite nanorod-coated PE separators can achieve a stable cycle up to 500 h under the test condition of 2 mA·cm-2 and 2 mAh·cm-2, while maintaining low voltage polarization.