利用電漿輔助化學沉積提升鋰離子電池中富鎳三元正極材料電化學性能之應用

Improved Electrochemical Performance of Nickel-rich Ternary Cathode Materials for Li ion Batteries via Plasma-assisted Chemical Vapor Deposition

曾子芯(Tzu-Hsin Tseng)

指導教授 ： 劉偉仁

中原大學/工學院/化學工程研究所/碩士(2022年)

https://doi.org/10.6840/cycu202200069

摘要

鋰離子電池作為一種新型的綠色能源，且具有多方面的優點，被廣泛應用於手機和筆記型電腦等數碼電子產品，純電動及混合動力新能源汽車，以及能源儲能系統之中。正極材料是鋰離子電池的關鍵組成，其不僅作為電極材料參與電化學反應，同時還要充當鋰離子源。理想的正極材料首先要有較高的化學穩定性和熱穩定性以保證充放電的安全，同時要有良好的電化學性能，具備較大的電容量與工作電壓、優良的循環和倍率性能。
本實驗以廠商提供的商用富鎳正極材料粉末LiNi0.8Co0.1Mn0.1O2(NCM811)在經過混漿塗佈後，再利用電漿濺鍍的方式進行表面改質，其中我們選擇了氮化鈦以及氧化鈦作為改質材料，而在電漿處理上因應不同改質材料的性質需選擇直流或射頻濺鍍。在電漿改質後，由於TiN良好的導電性與導熱性使其提升初始電容量至218.3 mAh/g，並且高溫下的循環穩定性在40圈以前依然維持在200 mAh/g，而後才漸漸有下降的趨勢，以及透過DSC可以看到放熱峰後移了53oC，安全性能也得到改善；TiO2因為是絕緣體，相對導電性沒有像TiN來的好，因此我們著重討論TiN改質。將TiN改質後的極片放在大氣環境下五天後，透過XPS可以明顯看出因TiN披覆而有效保護極片，使NCM811不與空氣中的CO2反應產生Li2CO3。將極片進行充放電50圈後，從SEM可以看出改質後的NCM顆粒被完整的保護，而原始的NCM811出現巨大的裂痕，進而影響電化學表現。經由一系列改質後的極片之結構分析與電化學分析，認為電漿濺鍍能有效控制改質膜厚以及品質穩定性，並且在正極材料的安全性與循環穩定性皆有提升，值得注意的是電漿改質的方式是有望一次生產大量，因此是具有發展潛力的改質方式應用於正極材料。

關鍵字

鋰離子電池 ； 富鎳三元正極材料 ； 電漿改質 ； 濺鍍 ； TiN 披覆 ； TiO2 披覆

並列摘要

With the demand of human society for energy, the supply of green, clean and efficient energy has become one of the serious and urgent issue faced by today's science. Lithium-ion batteries (LIBs) are the novel green energy due to their high capacity, low self-discharge, high open circuit voltage, non-memory effect, long cycling life and low pollution. Therefore, they have been widely used in cell phone, laptop, electric or hybrid electric vehicles, grid energy storage, etc. The cathode serves as a key component in LIB, it not only participates in electrochemical reaction as an electrode material but also at as a source of lithium ions. As an ideal cathode material, the first it needs to have high chemical and thermal stability to ensure the safety of charging and discharging; meanwhile, it needs to have good electrochemical performance, large specific capacity, large working voltage, excellent cycle and multiplier performance. Furthermore, it should be easier to prepare, more friendly to the environment and cheaper than other material.
In the experiment, we used the commercial rich nickel cathode material, provided by the manufacturer. After dispersing mixture, we modified surface by sputtering. We took titanium nitride and titanium oxide as modification materials, and we would choose DC or RF sputtering depending on the nature of the modification materials. We could observe the improvement of initial capacity, cyclic life, C-rate and safety by the good thermal and electrical conductivity of TiN. Next, we were going to discussed the modification of TiN because TiO2 was an insulator and its conductivity was not as good as that of TiN. After TiN-modification, we kept the electrode in air for five days. It was obvious from XPS that TiN effectively protects the electrode so NCM811 would not react with the CO2 and produce Li2CO3 in air. After charging and discharging for 50 cycles, SEM show that after TiN-modified, NCM particles were completely protected. Pristine NCM811, by contrast, had huge cracks, which would affect the electrochemical performance. After a series of structure and electrochemical analysis of the TiN-modified, conformed that sputtering can effectively control the modified film thickness and stability, the safety and cyclic stability of the cathode material have been improved by TiN- modification. Furthermore, the method of modification can be able to mass-produce by sputtering. In conclusion, it is a cathode material with great potential development.

並列關鍵字

Lithium-ion batteries ； Rich-nickel ternary cathode material ； NCM811 ； Sputtering ； TiN coating ； TiO2 coating

參考文獻

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