廢料之復活： 利用鍍膜及電漿表面改質技術於回收矽/碳化矽之複合材 與其鋰離子電池之應用

A Revival of Waste: Surface Modification via Coating and Plasma Jet in Recycled Si/SiC Composite for Lithium Ion Batteries

陳秉宏(Chen, Bing Hong)

指導教授 ： 杜正恭

國立清華大學/工學院/材料科學工程學系/博士(2017年)

摘要

在過去數十年，鋰離子電池的發展被視為一開發的主流來解決能源儲存裝置之議題。在此相關產業蓬勃發展的同時，高電容密度以及低環境影響的條件已被當作鋰離子電池正負極活物選用時的基本要求。現今負極活性材料，多採用碳材為主而限制了其高電容量之發展性。其中矽基負極材料，因充放電過程中形成Li15Si4合金所貢獻之理論電容量高達3590 mAh/g 可吻合高電容量的條件，被認定為最具潛力來取代傳統碳基電池的潛力材料，但卻因其合金化過程所造成的體積膨脹與伴隨的固態電解質生成相，造成電容量之衰減而影響其應用端的發展。為了克服矽基電池的缺點，大部份的研究致力於 (1) 合成各種特殊形貌來縮小矽粉體至奈米尺度， (2) 包覆或混合添加物於粉體上或漿料中，或 (3) 加入電解液添加劑等方法。然而，上述等方法往往與商業化之低成本以及環保之低污染源的需求大相逕庭。
本論文擬開發低成本且環境友善之矽基高容量鋰電池負極材料。材料端選用自太陽能切削廢液，回收純化後所得之回收矽廢料為活性材料，其微米尺度粉體遠大於一般效能較好之奈米尺度粉體，且其表面含有豐富的有機鍵結與原生氧化層。有別於傳統之方法，多種表面改質技術於本論文中提出，其技術包含表面碳薄膜鍍製與大氣電漿處理，係作用於矽基電池極片表面，由介面著手優化其表面鍵結組態，來抑制固態電解液相之生成。此外，更佐以整體電池極片之空間佈局，並配合添加劑以及導電劑之調控，增加矽基回收廢料之循環壽命。本論文中所開發之技術相較於其他化學合成方法來說，除了簡易、快速、低成本且環境友善外，更可有效地達到優異電性的表現，預期所開之各種表面改質技術能推廣至更多不同電池材料系統中。咸信本文所選用之廢料回收之負極材料，可適用於未來高電容量之商業化發展鋰離子電池中。

關鍵字

鋰離子電池 ； 矽 ； 廢料回收 ； 大氣電漿 ； 表面改質 ； 鍍膜

並列摘要

In the past decade, the rising development of lithium ion batteries (LIBs) has been recognized as a tidal current for solving energy storage related issues. Under this technical billow, the demands of active materials with lower environmental impact and higher energy density are considered as the criteria for LIBs materials. Especially for anodic material, the present carbon-based electrode is limited in the potential applications with high capacity because of its theoretic capacity (372 mAh/g). To achieve the goal for high capacity anodes, silicon (Si) with 3590 mAh/g theoretical capacity meets the requirement by forming Li15Si4 phase during cycling processes to replace present conventional carbon-based batteries. However, the capacity fading caused by the intrinsic drawbacks of volumetric expansion and continuous formation of solid electrolyte interphase hinders the dissemination of Si-based LIBs. To overcome the disadvantages of Si, numerous studies have endeavored (1) to shrink Si particles to nanometer scales by using various morphology-chemical synthesis techniques, (2) to wrap or mix conductive additives onto particles or into slurries, and (3) to add electrolyte additives. Unfortunately, the as-mentioned methods mostly fail to accommodate the cost-effectiveness of commercialization and low pollution of environmental friendliness.
In the pursuit of low cost and high environmental friendly anode material, a distinct resource of Si-based anode material is explored in this study. The recycled material is extracted from the cutting waste fluid produced in solar panel industry. After purification technology of chemical rinsing and physical separation, the obtained composites show much larger particle size than commonly nanolized Si particles, and possess the abundant organic bonds and native oxide on the surface of particle. Unlike conventional methods to focus on the synthesis process of powder, the as-prepared electrodes will be treated via various surface modifications, including techniques of carbon deposition and atmospheric pressure plasma jet. The combined processing reduces the capacity degradation by interfacial control to convert the surface bonds with the effectiveness to suppress the growth of SEI, and then maintain the stabilization of electrode during cycling. In addition, the entire electrode collocates with conductive agent and electrolyte additive to provide the conductivity and to improve the internal SEI formation. Overall, the developed techniques of surface modifications are not only scalable, simple, low-cost and environmental friendly but also effective to achieve the excellent performance with high capacity. It is expected for similar potential usage in others battery system. The selected recycled waste for anodic material should be applicable and suitable for the future blueprint in the commercialization for LIBs.

並列關鍵字

Lithium ion batteries ； Silicon ； Recycled waste ； Atmospheric pressure plasma ； Surface modification ； Coating

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