2-甲氧基丙烯酸乙酯-丙烯酸共聚物的合成及其在锂离子电池中的应用

随着锂离子电池的不断发展，电池中正负极材料也不断进行着迭代更新。在负极材料中，硅（Si）理论比容量高达4200 mAh/g，在地壳中含量丰富，被看作最具商业化潜力的石墨负极替代品。但是Si在脱嵌锂过程中会产生超过300%的体积变化，导致Si粒子的粉化和电极结构的破坏。目前商用粘结剂丁苯乳胶（SBR）对Si粘结强度低，力学强度低，难以有效缓解Si负极的膨胀效应。在正极材料中，磷酸铁锂（LFP）价格低廉，安全性好，循环稳定性高，被广泛应用于动力电池等领域。然而LFP正极选用聚偏氟乙烯（PVDF）作为粘结剂，需使用N-甲基吡咯烷酮（NMP）作为溶剂，在涂布完成后还需对NMP进行回收。近年来NMP和PVDF的价格水涨船高，使用油溶性的PVDF不仅会造成环境污染，且也增加了电池制造成本。因此，传统的粘结剂亟待更新，以满足当前正负极材料的要求。

本文以聚丙烯酸（PAA）和2-甲氧基丙烯酸乙酯（MEA）为反应单体合成一种新型粘结剂PAA-MEA，以改善锂离子电池SiO负极以及LFP正极的电化学性能。在SiO负极中，PAA-MEA聚合物玻璃化温度更低，更加柔韧，有助于缓解SiO负极循环过程中的膨胀。在LFP正极中，PAA-MEA作为水溶性粘结剂，具有环保和节约成本的优势。主要研究成果如下：

PAA-MEA粘结剂提高了正负极极片的柔韧性，平均剥离力超过5 N，具有比PAA和PVDF更加优异的力学性能。负极测试中，相比于PAA，PAA-MEA为粘结剂制备的SiO负极半电池的可逆比容量和容量保持率显著提升，0.1 C电流密度循环120圈后可逆比容量为1811 mAh/g，容量保持率为66%。进一步控制PAA-MEA合成的引发剂用量，结果表明引发剂用量为0.1%的PAA-MEA-0.1%分子量更高，电化学性能进一步提升，120圈后循环容量保持率为69.4%。LFP正极测试中，以PAA-MEA为粘结剂，循环140圈后放电比容量为143 mAh/g，容量保持率为92.8%，在引入水性体系的同时保持了优异的电化学性能。

本文通过对PAA聚合物的改性，增强了聚合物粘结剂的柔韧性和结构稳定性，采用水溶剂体系降低了电极制备成本，对开发高性能的锂离子电池粘结剂开辟了新的途径。

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