RESUMO
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).
RESUMO
Conjugated porous polymers (CPPs) possess great potential in the energy storage aspect. In this work, a boron-dipyrromethene (BODIPY)-conjugated porous polymer (CPP-1) is achieved by a traditional organic synthesis route. Following this, a carbonization process is employed to obtain the carbonized porous material (CPP-1-C). The two as-prepared samples, which are characterized by doping with heteroatoms and their porous structure, are able to shorten the lithium-ion pathways and improve the lithium-ion storage property. Then, CPP-1 and CPP-1-C are applied as anode materials in lithium-ion batteries. As expected, long-term cyclic performances at 0.1 and 1 A g-1 are achieved with maintaining the specific capacity at 273.2 mA h g-1 after 100 cycles at 0.1 A g-1 and 250.8 mA h g-1 after 300 cycles at 1 A g-1. The carbonized sample exhibits a better electrochemical performance with a reversible specific capacity of 675 mA h g-1 at 0.2 A g-1. Moreover, the capacity is still stabilized at 437 mA h g-1 after 500 cycles at 0.5 A g-1. These results demonstrate that BODIPY-based CPPs are capable of being exploited as promising candidates for electrode materials in the fields of energy storage and conversion.
