應用於鋰離子電池之雙摻雜鹵化物型固態電解質

Abstract

近年穿戴式裝置與電動車之發展，對於電池之需求逐漸上升，因兩者皆具移動性，降低電池重量以增加裝置之輕便性與電動車之續航力即為急需解決之問題，如何提升電池之能量密度與安全性為目前研究重要之方向。 本研究於鹵化物型固態電解質鋰銦氯(Li3InCl6)進行雙摻雜改質，摻雜鋯離子取代銦離子以增加固態電解質之離子導率，並摻雜氟離子取代氯離子以增加其電化學窗口。因摻雜氟離子將降低固態電解質之離子導率，故本研究以Li2.9In0.9Zr0.1Cl5.2F0.8作為固態電解質，其離子導率可達5.96 × 10-4 S/cm，與純鋰銦氯與純摻氟離子之固態電解質相比，其具較高之離子導率，同時其可抑制電解質於高電壓之氧化反應，降低副反應之問題。雙摻雜結構與純鋰銦氯相比，對稱電池可得較低之過電位與較長之循環壽命。 本研究亦對鎳錳酸鋰陰極(LiNi0.5Mn1.5O4; LNMO)與Li2.9In0.9Zr0.1Cl5.2F0.8進行界面反應研究，以X光電子能譜儀證實無序相鎳錳酸鋰陰極(disordered-LNMO)與Li2.9In0.9Zr0.1Cl5.2F0.8將產生副反應，形成銦金屬與Mn4+，然而若於LNMO表面包覆磷酸鋰(Li3PO4; LPO)則可抑制副反應發生。 最後本研究以鈷酸鋰(LiCoO2; LCO)與LNMO陰極組裝全電池。以Li2.9In0.9Zr0.1Cl5.2F0.8作為固態電解質之全固態LCO電池，其首圈電容為140 mAh且庫倫效率為90%，與純鋰銦氯與摻氟之結果相比可得較好循環穩定性與較高之電容。而以LNMO作為陰極之全固態電池，有序相鎳錳酸鋰(ordered-LNMO)因其離子導率較低，其組裝之固態電池因阻抗過高無法進行充放電，而disordered-LNMO包覆Li3PO4之陰極可得更高之電容，其首圈電容為78 mAh/g且庫倫效率為86%，其相較於僅摻氟之電池具較佳之電池表現。

In recent years, the development of wearable devices and electric vehicles has increasingly demanded batteries due to their need for mobility. Reducing battery weight to enhance the portability of devices and the endurance of electric vehicles is a critical issue that needs to be addressed. The enhancement of battery energy density and safety is currently a major focus of research. This study modifies halide-type solid electrolyte lithium indium chloride (Li3InCl6) through dual doping to increase its ionic conductivity and electrochemical window. Considering that doping with fluorine ions may reduce the ionic conductivity, this study uses a dual-doped lithium indium chloride formulation, Li2.9In0.9Zr0.1Cl5.2F0.8, achieving an ionic conductivity of 5.96 × 10-4 S/cm, surpassing the results obtained with pure lithium indium chloride. This research assembles full batteries using lithium cobalt oxide (LiCoO2; LCO) and LNMO cathodes. A solid-state LCO battery using Li2.9In0.9Zr0.1Cl5.2F0.8 as the electrolyte shows a first-cycle capacity and coulombic efficiency superior to those obtained with pure lithium indium chloride and fluorine-doped lithium indium chloride. With LNMO as the cathode, the solid-state battery assembled using ordered LNMO has too high an impedance for charging and discharging due to its lower ionic conductivity. However, a cathode of disordered LNMO coated with Li3PO4 achieves a higher capacity compared to pure disordered LNMO. The novelty of this study lies in the use of dual-doped halide solid electrolyte lithium indium chloride, which not only increases its ionic conductivity but also enhances its electrochemical window. This reduces side reactions at high voltages and also enhances the cycling efficiency of the battery.