Conductive adhesive for positive electrode of lithium-sulfur battery and preparation method of conductive adhesive

Abstract

The invention provides a conductive adhesive for a positive electrode of a lithium-sulfur battery and a preparation method of the conductive adhesive, and belongs to the technical field of lithium-sulfur battery materials. The problems that the existing conductive adhesive consists of a conductive component and a non-conductive component, and the use amount of the adhesive is large are solved. The adhesive consists of a doped conductive polymer material and a good solvent, wherein the mass fraction of the doped conductive polymer material is more than or equal to 0.25%. The invention also provides a preparation method of the conductive adhesive for the positive electrode of the lithium-sulfur battery. The doped conductive polymer material is dissolved in the good solvent until the doped conductive polymer material is completely dispersed to obtain the conductive adhesive for the positive electrode of the lithium-sulfur battery. The adhesive is not added with other non-conductive components, so that the cycle life of the battery is prolonged; during film formation, the density of conductive polymer is relatively low, and therefore the use amount of the adhesive is very small, and the proportion of sulfur in the positive electrode material is improved, thereby the specific capacity of the battery is increased.

Description

technical field [0001] 本发明属于锂硫电池材料技术领域,具体涉及一种锂硫电池正极用导电粘结剂及其制备方法。 Background technique [0002] 当今世界,新能源技术飞速发展。随着智能通讯和电动汽车领域的潜在市场需求,更高能量密度的二次电池体系已经成为目前研究热点。锂硫电池是以硫元素作为电池正极,金属锂作为负极的一种锂电池。理论上,锂与单质硫反应完全是二电子反应,硫电极的理论比容量为1675mAhg -1 ,金属锂负极的理论容量为3860mAhg -1 . 两者构建的锂硫二次电池体系的理论能量密度达2600Whkg -1 ,具有十分广阔的应用前景。研究中发现,元素S的电子导电性极差,在作为正极材料使用时,活性物质S的利用率不高,可逆性差,使容量持续下降。另外,硫(S 8 )在还原过程中产生的中间产物多硫化物Li 2 Sx(2﹤x≤8),如Li 2 S 4 可以溶于电解液,导致充放电过程中多硫化物在电池正负极间来回穿梭(穿梭效应),致使硫在充电过程中不能完全回到正极,从而使电池容量造成不可避免的下降。 [0003] 锂硫电池正极材料一般包括三部分:含硫的复合物、导电碳黑及粘结剂。含硫的复合物主要由导电框架及硫单质组成,是正极材料核心部分。导电碳黑加入的目的在于弥补正极活性物质导电能力不足。由于碳黑及大部分的含硫的复合物都是固体粉末,因此需要加入粘结剂方可成膜应用。目前,已报道的导电粘结剂都是由导电组分(如导电高分子 / 导电炭黑等)和非导电组分(如聚四氟乙烯、聚偏氟乙烯和丙烯腈多元共聚物等)共同构成,在成膜时,其用量较大,一般在总质量的10%wt左右,另外,这些粘结剂都是电子绝缘体,会在一定程度上降低正极材料的电子传输能力,进而影响电池的容量及倍率性能。因此,改善锂硫电池所用粘结剂的导电性、降低粘结剂用量、提高粘结剂的成膜能力是当下锂硫电池所用粘结剂的研究方向。而目前,只含有导电高分子单一组分的的导电粘结剂尚未有报道。 Contents of the invention [0004] 本发明的目的是为了解决现有的导电粘结剂都由导电组分和非导电组分共同构成,且粘结剂用量大的问题,而提供一种锂硫电池正极用导电粘结剂及其制备方法。 [0005] 本发明首先提供一种锂硫电池正极用导电...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that the existing conductive binders are composed of conductive components and non-conductive components, and the amount of binder is large, and to provide a conductive binder for lithium-sulfur battery positive electrode and its preparation method

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