锂电负极废涂布浆料破胶减容与资源化利用

Gel breaking-capacity reduction and reutilization of waste lithium anode coating slurry

锂电负极废涂布浆料含水率高、胶态分散稳定性强,难以过滤。本文研究了废涂布浆料的胶态特性,分析了废浆料的高效破胶分离机理,并对其资源化进行了初步探索。羧甲基纤维素钠(CMC-Na)解离产生的羧基负离子(R-COO-)提供的静电斥力及苯乙烯-丁二烯橡胶(SBR)在颗粒间形成的空间位阻力是废浆料胶态稳定性的根本原因。酸度的降低能够抑制浆料中CMC-Na的解离,减少吸附于石墨颗粒表面的带电基团R-COO-,削弱静电斥力,造成颗粒团聚,并破坏SBR的架桥作用。pH=2.0时,废浆料破胶过滤效率较佳,过滤常数为0.0741m2/s,含水率降低48个百分点;X射线三维显微成像分析(X-CT)表明细微颗粒团聚破胶的同时,保留的静电斥力能够降低过滤阻力,促进滤饼孔道结构的发育,生成大孔隙半径,长喉道的渗流网络减少滤饼孔道吸附水的量;分离所得固相碳材对亚甲基蓝、铬(Cr^(6+))、COD的吸附量分别为435mg/g、0.645mg/g、87mg/g,满足《工业水处理用活性炭技术指标及试验方法》(LY/T3279—2021)优级品标准。

Waste lithium anode coating slurry is hard to filtrate and also hard to be reutilized since it contains high water content,which is strongly stable with a wonderful colloid dispersion.The colloidal properties of this waste coating slurry were characterized,its high-efficiency rubber breaking separation mechanisms were discussed,and its reutilization as active carbon was also investigated.The electrostatic repulsion provided by the carboxyl anion(R-COO-)produced by the dissociation of sodium carboxymethylcellulose(CMC-Na)and the spatial resistance formed between particles by styrene-butadiene rubber(SBR)were the fundamental reasons for the colloidal stability of waste slurry.The decrease in acidity effectively suppressed the dissociation of carboxymethyl cellulose sodium(CMC-Na)in the slurry,resulting in reduced adsorption of charged groups(R-COO-)onto the surface of graphite particles.Consequently,the electrostatic repulsion between particles weakened,facilitating particle agglomeration and undermining the cross-linking effect of styrene-butadiene rubber(SBR).When pH was 2.0,the filtration constant of the waste slurry escalated to 0.0741m2/s,resulting in a remarkable 48 percentage point reduction in moisture content.X-ray three-dimensional microscopy analysis(X-CT)showed that while fine particles agglomerated and broken,the retained electrostatic repulsion could reduce the filtration resistance,promote the development of the filter cake pore structure,generate a large pore radius,and the seepage network of the long throat channel reduced the amount of water adsorbed by the filter cake pores.Moreover,the separated solid carbon material demonstrated impressive adsorption capacities of 435mg/g,0.645mg/g and 87mg/g for methylene blue,chromium(Cr^(6+))and COD,respectively.These values adhered to the first-rate standards set forth in the“LY/T 3279—2021”.