玻璃陶瓷態Li7P3S11鋰離子固態電解質合成及介面處理之研究

Synthesis and Interface-Processing on Li7P3S11 Solid Electrolytes for All-Solid-State Lithium-ion Batteries

林丞逸(Cheng-Yi Lin)

指導教授 ： 劉偉仁

中原大學/工學院/化學工程研究所/碩士(2020年)

https://doi.org/10.6840/cycu202000449

摘要

鋰離子電池目前被廣泛的應用在儲能設備上，比如筆記型電腦，手機，甚至應用在需求更高的電容量密度、更穩定的循環壽命、安全性的電動汽車等設備上。但是目前鋰離子電池所使用的電解質為液態的有機物電解質，因此有易燃易爆和不耐高溫等安全上的問題。而使用固態電解質被認為是此問題的解決方式，因此固態電解質是能目前重要的研究方向。
本研究以Li7P3S11為主題，實驗以透過簡單的機械球磨法合成出非晶相的固態電解質，利用XRD圖譜找到最佳球磨時間，再搭配DSC、EDS、SEM、EIS等分析找出LPS試片的最佳燒結程序，成功合成出Li7P3S11固態電解質。
首先，以機械球磨法合成出非晶相的Li2S-P2S5固態電解質，從SEM和元素分析可知道P和S元素分佈相當均勻，且並無O元素的出現，這說明在此合成步驟中並無和O元素發生反應，接著探討了粉體之熱燒結溫度，並以SEM、XRD、DSC和EIS等分析，討論其燒結後對微觀結構、導電性質等影響，其中樣品Li2S-P2S5-25oC-4hr有最高的離子電導率1.1x10-3 S/cm。
為了確認Li7P3S11與鋰接觸時的穩定性進行鋰對鋰的對充測試，分別以不同鋰金屬直徑在室溫下分別以0.1、0.2和0.3 mA/cm2的定電流密度進行10個循環的鋰對充測試，並且藉由EIS交流阻抗量測其介面阻抗。在鋰金屬片徑為10 mm時，有最小介面阻抗650 Ω和良好穩定性，接著以電流密度為0.1 mA/cm2進行200個循環測試，在較常循環測試下仍然有良好的循環表現，但是Li7P3S11與鋰金屬介面仍然有非常大的介面阻抗650 Ω。
由於Li7P3S11與鋰金屬之介面仍有非常大的介面阻抗，因此我們將Li7P3S11與鋰金屬進行複合，製備成複合電極，在後續的循環測試中，在0.1 mA/cm2電流密度的200個循環測試中，並無短路現象發生。這說明將部分固態電解質與鋰金屬製備成複合電極能有效改善電極與固態電解質之間的介面阻抗，介面阻抗從650 Ω下降至430 Ω，因此Li7P3S11為具有潛力，能應用於鋰離子電池之固態電解質材料。

關鍵字

硫化物固態電解質 ； 離子電導率 ； 鋰金屬 ； 複合電極 ； 介面阻抗

並列摘要

The design of solid state electrolytes with high ionic conductivity is of great importance to develop next-generation Li ion batteries. In the first part of this work, the Li2S-P2S5 glass powder were prepared by mechanical milling using a planetary ball-milling apparatus. The amorphous structure is measured by XRD after 20 hours ball-milling method with a white color powder.
The second part, the obtained glass sample was sealed in the carbon-coated quartz tube and heat from room temperature (22 to 25 °C) to 250 °C for 4 h to obtain the glass-ceramic Li7P3S11 sample which has a high ionic conductivity (1.14 x 10-3 S/cm) and all process were hold in Ar-filled glove box. Crystallinity, morphology and conductivity of the samples were analyzed using small and wide angle powder X-ray diffraction (XRD) with the holder, and impedance analyzer, respectively.
The third part, we test the dendrite suppression capability of Li7P3S11 glass-ceramic sample by cycling the sandwich structure Li/Li7P3S11/Li at step-increasing current density 0.1, 0.2 and 0.3 mA/cm2 every 10 cycles with different lithium foil diameter. The sandwich structure Li/Li7P3S11/Li has the lowest interface resistance 650 Ωand the best cyclic performance with lithium foil diameter 10 mm. However, the interface resistance is still very high between lithium foil and Li7P3S11 solid electrolyte.
The last part, we try to combine lithium foil and Li7P3S11 solid electrolyte into a composite material becomes a composite electrode. And we test the dendrite suppression capability of Li7P3S11 glass-ceramic sample with composite electrode by cycling the sandwich structure LiLPS/Li7P3S11/LiLPS. The interface resistance decreases from 650 Ω to 430 Ω because of the increasing pathway of the lithium ions. Sandwich structure LiLPS/Li7P3S11/LiLPS was cycled for 200 cycles and maintained stable voltage profile at a current density 0.1 mA/cm2. Therefore, Li7P3S11 is a potential candidate as a solid electrolyte for lithium-ion batteries.

並列關鍵字

Li7P3S11 ； solid electrolyte ； ionic conductivity ； ball-milling ； lithium-ion batteries

參考文獻

[1] F. Mizuno, C. Yada, H. Iba, Solid-state lithium-ion batteries for electric vehicles, Lithium-Ion Batteries (2014) 273-291.

[2] J.G. Kim, B. Son, S. Mukherjee, N. Schuppert, A. Bates, O. Kwon, M.J. Choi, H.Y. Chung, S. Park, A review of lithium and non-lithium based solid state batteries, Journal of Power Sources 282 (2015) 299-322.

[3] J. Li, C. Ma, M. Chi, C. Liang, N.J. Dudney, Solid electrolyte: the key for high‐voltage lithium batteries, Advanced Energy Materials 5(4) (2015) 1401408.

[4] B. Huang, X. Yao, Z. Huang, Y. Guan, Y. Jin, X. Xu, Li3PO4-doped Li7P3S11 glass-ceramic electrolytes with enhanced lithium ion conductivities and application in all-solid-state batteries, Journal of Power Sources 284 (2015) 206-211.

[5] M. Eom, J. Kim, S. Noh, D. Shin, Crystallization kinetics of Li2S–P2S5 solid electrolyte and its effect on electrochemical performance, Journal of Power Sources 284 (2015) 44-48.