【作者】 徐婷；

【导师】 詹晖；

【作者基本信息】 武汉大学 ， 物理化学， 2022， 硕士

【摘要】 锂离子电池（LIB）因具有高能量密度和功率密度,已在便携式电子市场占据了主导地位,并在逐步向电动汽车等大规模储能应用扩展。目前,商用锂离子电池主要以过渡金属氧化物为阴极,此类材料通常涉及稀缺的自然资源,难以满足可持续发展的需要。有机化合物特别是羰基化合物因其理论容量高、成本低、环境友好等优点,成为下一代可充电电池的候选材料。然而,有机小分子羰基化合物普遍存在羰基利用率低和在电解液中的溶解等问题,这阻碍了其进一步应用。本论文以有机羰基小分子电极材料为研究对象,从电解液的角度出发,探究了电解液组成对有机小分子电化学性能的影响。本论文的研究内容可分为以下两个部分:一、针对酸酐小分子电极材料的电解液设计我们以有机酸酐小分子3,4,9,10-苝四羧酸二酐（PTCDA）为锂离子电池阴极,以Li TFSI-PYR₁₄TFSI为基础电解液,分别以1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚（TTE）,1H,1H,5H-八氟戊基-1,1,2,2-四氟乙基醚（OFE）,二氯甲烷（DCM）,四氢呋喃（THF）为稀释剂,设计了一系列离子液体-稀释剂电解液,并研究了它们对PTCDA极片浸润性、溶解性和电化学性能的影响,从而筛选出循环稳定性最优的电解液Li-4PYR₁₄-5TTE和倍率性能最好的电解液Li-4PYR₁₄-5THF。在此基础上,我们将两种稀释剂以不同比例结合,配制了二元稀释剂电解液,结果表明二元稀释剂电解液结合了TTE和THF的优点,同时更有效地综合解决了离子液体粘度,电导率上的不足,在保持离子液体电解质带来的循环稳定性优势外,明显提高了PTCDA倍率性能。此外进一步的评估表明,这种二元稀释离子液体电解质的优势在高温条件以及厚电极上仍得到显现,而且即使用在其他小分子衍生物上,也具有一定效果。二、针对醌类小分子电极材料的电解液设计我们以醌类小分子5,7,12,14-并五苯四酮（PT）为锂离子电池阴极,探究了醚类电解液的溶剂、浓度、电压区间等因素对电池电化学性能的影响。结果显示,电解液的组成对PT的电化学性能有很大影响作用,其中高浓度的醚类电解液能够有效改善材料的溶解流失问题。在5M DME电解液中,PT在500次循环内容量损失不足10%,库伦效率接近于100%。对高浓电解液进行稀释处理,可以明显提升材料的倍率性能,同时基本维持材料的循环稳定性。更多还原

【Abstract】 Lithium-ion batteries（LIBs）have been a dominant role in the portable electronics market due to their high energy density and power density,and their application are gradually expanding to large-scale energy storage applications such as electric vehicles.With the huge success in the battery market,commercial lithium-ion batteries based on transition metal oxides cathode now is facing the resources issues and the concerns about sustainable development.Organic compounds,especially carbonyl compounds,have become a prominent candidate material for the next generation of rechargeable batteries because of their high theoretical capacity,low cost and environmental friendliness.However,organic small-molecule carbonyl compounds much suffer from low material utilization and dissolution loss,which hinder their further application.In this thesis,we try to address the dissolution issue through the electrolyte optimization,and investigated the effect of electrolyte composition on the electrochemical performance of organic carbonyl small molecule electrode materials.The main results were listed in the following:1.Electrolyte strategy for small-molecule anhydrides electrode materialsWe designed a series of diluted ionic liquid electrolytes with lithium bis（trifluoromethanesulphonyl）imide（Li TFSI）-1-butyl-1-methylpyrrolidinium bis（trifluoromethylsulfonyl）imide(PYR₁₄TFSI)as the base electrolyte,and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether（TTE）,1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether（OFE）,dichloromethane（DCM）,or dichloromethane（THF）as the diluents.Their effects on the wettability,solubility and electrochemical performance of PTCDA electrodes were studied.After screening four electrolytes,Li-4PYR₁₄-5TTE and Li-4PYR₁₄-5THF were picked out for further investigation,as the former endowed PTCDA electrode with the most stable cycling while the latter brought the best rate performance.Binary-diluent electrolyte was formulated to combine the advantage of TTE and THF.The results show that the binary-diluent electrolyte much reduced the viscosity and increased the conductivity and wettability of ionic liquid electrolyte.Additionally,it well tackled the rate performance issue and helped to maintain the cycling stability of PTCDA.On the other side,the effect of binary-diluent electrolyte was further evaluated at high temperature,or on thick electrodes and other small molecule derivatives,and its effectiveness was again proved.2.Electrolyte strategy towards small-molecule quinone electrode materialsTargeting at the dissolution loss of 5,7,12,14-pentacenetetrone（PT）,we investigated the effects of ether electrolyte composition on its electrochemical performance.The results showed the strong relevance between the electrolyte and capacity,cycling stability and even polarization characteristic of PT.In concentrated ether electrolyte,the dissolution of PT materials could be effectively alleviated.When using 5M Li TFSI in DME electrolyte,the capacity decay could be reduced to less than10%capacity within 500 cycles,accompany with a coulombic efficiency close to 100%.Further adding diluent in it could significantly improve the rate performance of PT,meanwhile the cycling stability was maintained.更多还原