回收矽晶切割廢料製備鋰離子電池矽-鎳複合負極

將製程副產物回收再利用、使廢料轉變成高價值產品，這種兼具環保及收益的概念在工業上越來越受到重視。多晶矽太陽能發電模組削切成薄片過程中約30% - 50%的矽會以奈米粉體顆粒的形式隨著研磨漿液流失，由於目前世界太陽能矽晶年需求量約為二十萬噸，因此後續伴隨產生的廢料中所含矽粉是非常可觀且大量的。奈米矽為具有高比電容量潛力的鋰離子電池負極材料，然而其實際應用最需要克服的瓶頸在於，充放電過程中因體積變化引起電極材料的粉化，而導致電容量迅速的損失。在此研究中，我們利用切割廢料漿液處理過後回收而得的矽基粉體，以創新的做法形成高機械強度與高導電度的矽鎳複合物微米二次粒子，有效地改善以這種材料作為鋰離子電池負極的循環穩定性能，經由掃描式電子顯微鏡觀察電極板截面變化，發現充放電過程的體積膨脹可被抑制。我們整合了X光吸收光譜與X光繞射分析，提出了粉體在機械研磨中的固相反應機制：2 NiO + 3 Si → 2 a-NiSi + a-SiO2，並且發現透過調整高能球磨的時間與摻入碳黑，可導致矽在研磨過程中氧化程度的改變，進一步影響其電化學性能。此外，程溫還原(TPR)分析的結果亦顯示部分氧化鎳在球磨過程中被矽粒子還原。4小時研磨與1 wt.%碳黑的摻入，經過700°C還原煆燒而得的矽鎳複合物，是在此研究的各種製程條件中具有最高電化學性能的材料，能在高速充放電(5C)下保有較高的可逆電容量。最後藉由調整極板漿料的酸性程度並控制鋰離子遷入材料時的截止電位，得到具有良好循環壽命的負極。電化學測試結果顯示其在100圈的完全(深度)充放電下仍能保有85%的維持率；若截止電位控制在40 mV，100圈充放電後，電容量仍無衰退跡象。如此我們成功地將矽晶切割廢料回收再利用並製備出高性能、高價值的鋰離子電池負極材料。

關鍵字

鋰離子電池；矽負極；矽鎳合金；太陽能矽晶切割廢料；資源永續

並列摘要

Turning the recycled waste into high-value products is of strategic importance for industrial processes. Despite the fact that most of the high-purity Si is wasted during wafer slicing in fabricating photovoltaic (PV) modules, the applications of recycled kerf-loss Si (K-Si) still remain limited and may not meet the cost of purification from slurry containing abrasive silicon carbide (SiC). K-Si was found to be ragged-edge particles in nano-size, while micro-sized SiC single-crystallites featured sharp edge. A simple and facile method was developed to synthesize structurally robust Si-SiC-Ni composite microparticles (SSNs) from processed kerf-loss powder with the addition of metal Ni. Owing to their mechanically robust and conductive nature, the SSN electrodes exhibited suppressed expansion and stable cycling performance as lithium-ion battery (LiB) anodes. Adjustment in milling time with addition of carbon black (CB) resulted in different amount of amorphous silicon oxide (a-SiO2) formed during high-energy ball-mill. Analysis from X-ray absorption spectroscopy (XAS) combined with X-ray diffraction (XRD) led to the proposed mechanism of solid-phase reaction facilitated by ball-mill: 2 NiO + 3 Si → 2 a-NiSi + a-SiO2. Temperature programmed reduction (TPR) analysis further underlined the fact that part of NiO has been irreversibly reduced by Si particles in the milling step. As a result from process analysis and optimization, composite milled with 1 wt.% CB for 4 hours and calcined at 700°C was found to exhibit the most promising electrochemical behavior, suggesting a reversible capacity up to 769 mAh/g. Cycling stability was further improved by modifying the acidity of electrode-slurry and cut-off voltage for lithiation. Modified SSN anodes retained 85% retention of capacity after 100 cycles of full lithiation/delithiation at 300 mA/g and no capacity decay was observed for electrode cut off at 40 mV for lithiation in the first 100 cycles, which is expected to meet the requirement of practical applications in LiB and suggests an alternative for the usage of Si recovered from kerf loss.

並列關鍵字

Li-ion batteries ； Anodes ； Silicon ； Nickel ； Kerf loss ； Recycling

參考文獻

4. A. Goodrich, P. Hacke, Q. Wang, B. Sopori, R. Margolis, T. L. James, and M. Woodhouse, "A wafer-based monocrystalline silicon photovoltaics road map: Utilizing known technology improvement opportunities for further reductions in manufacturing costs", Sol. Energy Mater. Sol. Cells, 114, 110-135 (2013)

5. N. Drouiche, P. Cuellar, F. Kerkar, S. Medjahed, N. Boutouchent-Guerfi, and M. O. Hamou, "Recovery of solar grade silicon from kerf loss slurry waste", Renew. Sust. Energ. Rev., 32, 936-943 (2014)

6. H. P. Hsu, W. P. Huang, C. F. Yang, and C. W. Lan, "Silicon recovery from cutting slurry by phase transfer separation", Sep. Purif. Technol., 133, 1-7 (2014)

7. Y. C. Lin, T. Y. Wang, C. W. Lan, and C. Y. Tai, "Recovery of silicon powder from kerf loss slurry by centrifugation", Powder Technol., 200, 216-223 (2010)

8. T. H. Tsai, "Modified sedimentation system for improving separation of silicon and silicon carbide in recycling of sawing waste", Sep. Purif. Technol., 78, 16-20 (2011)

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回收矽晶切割廢料製備鋰離子電池矽-鎳複合負極

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