快離子導體類複合固態電解質於半固態鋰離子電池之研究;NaSICON-type LAGP in composite solid electrolyte for solid-state lithium ion battery

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/85690

Title:	快離子導體類複合固態電解質於半固態鋰離子電池之研究;NaSICON-type LAGP in composite solid electrolyte for solid-state lithium ion battery
Authors:	施瀚昇;Shih, Han-Sheng
Contributors:	化學學系
Keywords:	快離子導體;固態鋰電池;複合材料;NaSICON;Solid-state lithium battery;Composite solid electrolyte
Date:	2021-07-23
Issue Date:	2021-12-07 11:15:55 (UTC+8)
Publisher:	國立中央大學
Abstract:	由於液體電解質無法提供與日俱增能量密度以及安全性，次世代的電池便寄望使用固態電解質來取代液態電解質。然而每種類型的固態電解質都有其優缺點，其中就以擁有極高室溫導電度以及空氣穩定性的快離子導體類(NaSICON)的磷酸鍺鋁鋰(Lithium aluminum germanium phosphate， LAGP)無機物和擁有能直接成模且有高化學穩定性的高分子類的Poly(vinyl-idenefluoride-co-hexafluoropropylene) (PVDF-HFP)特別引人注目。然而 LAGP介面接合不佳以及需高溫使其緻密的缺點和PVDF-HFP無法有效抑制鋰枝晶的問題，限制了它們的發展。遂本篇研究利用簡單的溶劑鑄模法(Solvent-Casting)製作出複合高分子類的PVDF-HFP和氧化物類的LAGP以及鋰鹽的複合固態電解質，並於電極與電解質介面添加微量的液體電解質。發現若單以溶劑澆鑄法成膜會導致LAGP分布不均，但可以反過來利用此特性來避免LAGP與鋰負極發生反應。而以此複合固態電解質與磷酸鋰鐵和鋰箔所組成之半固態電池，能夠在0.3C下穩定充放電100圈還保有99%以上的電容保持率，且發現於0.1C下10wt% LAGP會有最佳的平均電容表現約為140 mAh/g；然而在3C下卻是15wt% LAGP有最佳的平均電容約為85 mAh/g，反應出高低充放電速率其傳遞機制不盡相同，高速率下LAGP會逐漸主導傳遞機制。此外，根據交流阻抗的結果，採用正極介面修飾來改善LAGP與正極相容性不佳所導致的高介面電阻的問題。添加15% LAGP的半電池在經修飾後Rct值從319下降到184，並可使半電池在0.5C下的庫倫效率更進一步提升，說明此介面修飾法在愈高比例的LAGP下會有愈顯著的效果。;Using solid state electrolyte to improve the safety and the energy density is a promising answer for the next-generation energy storage devices. Among various solid state lithium ion conductors, NaSICON-type ceramic- Lithium aluminum Germanium phosphate(LAGP) catch a lot of attention due to its advantages of high lithium ion conductivity in room temperature and high air stability, but it needs high pressure or temperature to densification to solve the disadvantages which is bad for commercial application. Therefore, we introduce an easy solvent-casting way to synthesis the composite solid state electrolyte. We embedding the Li1.5Al0.5Ge1.5(PO4)3 (LAGP) ceramic particles into the PVDF-HFP matrix. The ionic conductivity of composite solid membrane is around 2 x 10-6 S/cm when the amount of LAGP is 15 wt% almost five times higher than polymer electrolyte. Moreover, the Li\|CSE\|LiFePO4 cell exhibits long term life time its capacity retention rate is over 99% even run more than 100 cycle in 0.3C. However, higher capacity of 140 mAh/g in 0.1C for 10wt% LAGP, but higher 85 mAh/g in 3C for 15wt% LAGP suggest that the mechanism of ionic transportation is not the same between different current rate. Furthermore, with the interfacial modified, the interfacial resistance of half cell for 15wt% LAGP decreases from 355 to 193 almost half of its original one and the half cell coulombic efficiency is also improving.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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