利用回收矽晶粒子與木質纖維素製備碳矽複合材料應用於鋰離子電池負極之研究

Carbon-Silicon Composites Prepared from Recycled Silicon and Lignocellulose for Negative Electrodes of Li-ion Batteries

郭晉榕(Jin-Rong Kuo)

指導教授 ： 顏溪成

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701413

摘要

矽為新一代鋰離子電池負極材料的理想材料之一，因為矽具有非常高的比電容量與適當的工作電壓，極具成為鋰離子負極材料的潛力，但是矽基材在鋰嵌入與脫嵌時，會產生劇烈的體積變化，而體積驟然收縮會產生很大的機械應力使矽基材結構崩壞，最後導致電池的循環效能不佳。為了改善純矽基材所遇到的問題，本研究將使用熱處理程序將碳材導入，製備碳矽複合材料，改善純矽電極的循環特性。
有別於以往的研究，本研究使用從矽晶磚經鑽石線切削矽泥中所回收而來的次微米級矽粒子，搭配紙漿廠的副產物木質素與木質纖維素，進行碳矽複合材料的製備。兩種碳前驅物分別與回收矽粒子依重量比1:1進行超音波震盪混合程序，緊接著進行在600℃氬氣氣氛下進行燒結程序，由於不同種類的碳前驅物具有不同的型態，所以製備出具有不同結構的碳矽複合材料。在木質纖維素與矽的複材當中，碳化過後的木質纖維素可以作為材料的支撐體與增加導電性，而矽粒子會附著於其表面且彼此之間保有一定的空隙，這些空隙可以用來容納矽體積的變化，讓此結構具有相當出色的循環性能，其首圈去鋰化電容量(delithiation)為1165 mAh/g Si，經過51圈循環後，電容量還有970 mAh/g Si，電容量保留率高達83.4%。另一方面，在木質素與矽的複合材料當中，矽會包埋在木質素碳化完的基材中，而藉由不定型碳層的保護，可以有效減緩矽體積膨脹所產生的應力，進而抑制電容量的衰退現象。其電化學表現與純矽電極相比也相當優異，首圈去鋰化電容量為2286 mAh/g Si，且在300 mA/g循環51圈之後，還保有880 mAh/g Si。此項研究可以提供鋰離子電池負極材料的研究方向，一方面改善純矽電極的循環特性，另一方面可以減少廢棄物的產生與提升再生資源的附加價值，達成永續發展的循環型社會。

關鍵字

鋰離子電池 ； 鋰離子電池負極材料 ； 碳矽負極材料 ； 木質纖維素 ； 木質素

並列摘要

Silicon has the potential to replace the graphite as the anode material for Li-ion batteries due to its high specific capacity and appropriate working voltage. However, the dramatic volume change during the Li-ion insertion and extraction has caused the poor cyclic stability. To improve the cyclic stability of Si anode, we embedded Si into a carbon matrix to form a Si-C composites.
In this study, we employed the silicon particles recovered from the silicon ingot slicing slurries and the biomass (lignin and lignocellulose), which are by-products of pulp industry, to fabricate negative electrodes for lithium ion battery. Lignin or lignocellulose would be well mixed with Si particles by magnetic stirring and ultrasonication and then undergo a pyrolysis process to form Si-C composites. Due to different carbonaceous precursors, the composites have different structures. The pyrolyzed lignocellulose formed an interconnected structure with Si particles, which provides extra space to accommodate Si volume variation. The composite electrode exhibits outstanding cycle performance for capacity retention up to 83.4% after 51 cycles at 300 mAh/g. On the other hand, the Si particles in lignin-Si composites are coated with a carbon layer, and the layer can not only suppress the volume change but also increase the contact electronic conductivity. Besides, the SEI layer on the carbon surface would be stable. It also showed excellent electrochemical performance with an initial charge capacity up to 2286 mAh/g and retaining 880 mAh/g after 51 cycles at 300 mA/g. We hope that the utilization of renewable sources and industrial Si slurry as battery materials can be improved and applied in energy storage application.

並列關鍵字

Lithium ion batteries ； Li-ion batteries anode ； C/Si composites anode ； lignocellulose ； lignin

參考文獻

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