Abstract
In recent years, various attempts have been made to meet the increasing demand for high energy density of lithium-ion batteries (LIBs). The increase in voltage can improve the capacity and the voltage platform performance of the electrode materials. However, as the charging voltage increases, the stabilization of the interface between the cathode material and the electrolyte will decrease, causing side reactions on both sides during the charge–discharge cycling, which seriously affects the high-temperature storage and the cycle performance of LIBs. In this study, a sulfate additive, dihydro-1,3,2-dioxathiolo[1,3,2]dioxathiole 2,2,5,5-tetraoxide (DDDT), was used as an efficient multifunctional electrolyte additive for high-voltage lithium cobalt oxide (LiCoO2). Nanoscale protective layers were formed on the surfaces of both the cathode and the anode electrodes by the electrochemical redox reactions, which greatly decreased the side reactions and improved the voltage stability of the electrodes. By adding 2% (wt.%) DDDT into the electrolyte, LiCoO2 exhibited improved Li-storage performance at the relatively high temperature of 60 °C, controlled swelling behavior (less than 10% for 7 days), and excellent cycling performance (capacity retention rate of 76.4% at elevated temperature even after 150 cycles).
Highlights
In the past decades, remarkable progress has been made in lithium-ion batteries (LIBs) in the field of portable devices [1,2]
The research indicated that the DDDT-containing electrolyte was beneficial for the high-voltage LiCoO2 batteries, besides the previous breakthroughs towards LiNi0.5 Co0.2 Mn0.3 O2 /graphite batteries, which may provide a useful reference for the preparation of more stable LIBs by the formation of high-quality interfacial films in the cells
Comparing the cells in #1 and #2 electrolytes, it can be found that the redox peak potential of the cell in #2 electrolyte containing 0.5% DDDT appeared at 1.0 V during the first cycle, while it disappeared during the second and the third cycles
Summary
Remarkable progress has been made in lithium-ion batteries (LIBs) in the field of portable devices [1,2]. The oxidation reaction is catalyzed in the presence of transition-metal ions, and the decomposition of electrolytes is accelerated at lower potentials, leading to unexpected rapid capacity fading [14]. Ethers such as 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) have high ionic conductivities and coulombic efficiencies [15,16]. Electrolytes with excellent electrochemical properties always play an important role in improving the stability of LIBs. researchers have had great difficulty in developing novel electrolytes for high-performance LIBs. It is worth noting that the addition of a small amount of additive into the electrolyte is beneficial in forming a protective layer and preventing the solvent penetration; in this way, the possible damages to the electrode structure could be efficiently avoided. The research indicated that the DDDT-containing electrolyte was beneficial for the high-voltage LiCoO2 batteries, besides the previous breakthroughs towards LiNi0.5 Co0.2 Mn0.3 O2 /graphite batteries, which may provide a useful reference for the preparation of more stable LIBs by the formation of high-quality interfacial films in the cells
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