鋰電池極板製作之分析：混漿與塗佈

A Study on Making the Lithium-ion Battery Electrodes: Mixing and Coating

劉達人(Darjen Liu)

指導教授 ： 汪上曉

國立清華大學/工學院/化學工程學系/博士(2016年)

摘要

鋰離子二次電池為常見的能源儲存裝置，其電極板製造程序主要包含：(1)漿料混合和(2)塗佈乾燥製程，可直接影響電池特性的好壞。本論文分別研究此二程序，提出相較傳統方法，更先進且效率更佳之加工之方式。
鋰電池正、負極漿料配方中均含有大量的固體顆粒分散在含有機溶劑及黏結劑的高分子溶液系統之中，其粒子種類、大小、形狀各異，且漿料具較高黏度。本研究確認攪拌流場設計建立新穎的攪拌機和混漿程序以達到最佳的混合時間和效果。在比較數種不同的攪拌方式與混漿程序後，本研究發現，負極漿料以傳統的攪拌葉片即可達到和球磨攪拌機相同的分散效果，同時可以大幅節省混漿時間。正極漿料可以三維攪拌機和多步驟加料程序達到分散良好之目的。混漿分散效果可以量測漿料流變和流場觀察技術判定，並可進一步製作成極板組成電池比較其電池性能，再次確認以此方法和傳統攪拌方法比較可得到較好的電容量與循環壽命。
現有研究發現在製作極板時，因為鋰離子電池正負電極中含有相當比例的顆粒及黏著劑，在電極塗膜乾燥過程中，高溫乾燥條件有利於產品之生產速度，但會造成所謂黏結劑遷移現象，即電極塗層中粒子下沉而黏結劑上升，此種粒子顆粒與黏結劑分佈不均勻，會造成電極電性之不佳及塗層與基材黏著力下降。本研究利用一同時雙層塗佈之機制，將原本電極塗層一分為二，塗層中成份總重量，各成份比例不變，但在塗佈層結構中上層具較少黏著劑而下層具較多黏著劑，在快速乾燥中，因對流作用關係，反而使塗層內部黏著劑及顆粒之分佈達到均勻之效果，可以有效解決高溫乾燥時之黏結劑遷移缺陷，此效果以元素分佈和極板電導率量測得到證實，最後組成電池測試，亦發現可以改善其電容量、C-rate放電電容量與循環壽命。

關鍵字

鋰電池 ； 漿料混合 ； 塗佈 ； 乾燥 ； 雙層塗佈

並列摘要

Lithium ion secondary batteries as energy storage devices have become popular in recent years. Electrodes manufacturing process which involves mixing the slurry, coating and drying directly affect the quality of the battery performance. The thesis is divided into two parts respectively discuss ways to improve this second program compared to traditional methods.
Slurries for anodes and cathodes of lithium batteries contain a large percentage of solid particles of different chemicals, sizes and shapes in highly viscous media. A thorough mixing of these slurries poses a major challenge in the battery manufacturing process. Several types of mixing devices and mixing methods were examined. The conventional turbine stirrers or ball mill mixers could be adequately used for the preparation of anode slurries, but not suitable for cathode slurries. In this study, a newly three-dimensional mixer, in conjunction with a multi-stage mixing sequence were proposed. The mixing effectiveness was examined by means of rheological measurements and flow visualization techniques. Electrical performance results indicated that the battery obtained using the 3-D mixing device with a multi-stage mixing sequence was more efficient to those obtained from conventional methods.
The cathode and anode electrodes in lithium-ion batteries typically contain a significant proportion of particles and binders. During the electrode drying process, the high temperature will lead to the so-called "binder migration" phenomenon. Uneven particle/binder distribution can cause poor adhesion between the coated layer and which will level to the substrate, disruption of conductive paths and decrease the electrode performance. In this study, a two-layered cathode was designed using separate compositions of slurry ingredients in each layer, as produced by means of a simultaneous multilayer coating method. The two-layered cathode with the top layer containing less binder than the bottom layer was found to yield a better particle/binder distribution in the final structure under high temperature drying. The battery made with the two-layered cathode appeared to give a better overall performance.

並列關鍵字

lithium ion battery ； mixing ； coating ； drying ； two-layered coating

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