基于LMO和AC电极的锂离子超级电容器质量比调控

Mass ratio regulation forlithium ion supercapacitor based on LMO and AC electrodes

锂离子超级电容器结合了超级电容器高功率和锂离子电池高能量的特点而备受关注,正负极质量匹配对发挥锂离子超级电容器的性能至关重要。本文基于锰酸锂(LMO)正极、活性炭(AC)负极和乙腈电解液,设计制作了不同正负极质量比软包锂离子超级电容器,系统考察了电极质量比对锂离子电容器电性能、工作电压和低温性能的影响。结果表明:随着正负极质量比增大,锂离子电容器容量增大,倍率性能和低温性能提高,充放电曲线在高电极质量比下呈现线性关系,能量密度呈现先增大后减小的趋势。正负极质量比2/1时,锂离子电容器综合性能最优,50C的容量达到1C时的78.0%,最大功率密度为7247 W·kg^(-1),2.3 V下器件最大能量密度达到9.5 Wh·kg^(-1),3.1 V下器件和活性物质的能量密度分别提高至20.2 Wh·kg^(-1)和65.0 Wh·kg^(-1)。但宽工作电压会带来寿命衰减,在1~2.3 V充放电循环10000次容量保持率为93.0%,而在0.5~2.5 V充放电循环5000次容量保持率降至84.5%。在-40℃容量是25℃时的57.8%,能量密度依然还有5 Wh·kg^(-1)(2.3 V)。

Combining the high power of the supercapacitors and high energy of the lithium-ion batteries,lithium ion supercapacitors(Li-SCs)have attracted much attention.The positive and negative mass matching is crucial for the performance of the lithium-ion supercapacitors.In this paper,the pouch-like Li-SCs based on lithium manganate oxide(LMO)cathodes,activated carbon(AC)anodes and acetonitrile-based electrolyte with different cathode/anode mass ratios were designed and fabricated.The effects of cathode/anode mass ratio on the electrical performance,operating voltage and low temperature performance of Li-SCs were systematically investigated.The results show that the capacity,rate capability and low temperature performances were improved with the increase of the mass ratio.The charge and discharge curves of Li-SCs with high mass ratios were linear.The energy density increased first and then decreased with the increase of the mass ratio.Both excessive and insufficient mass ratio lead to the decay of the cycle life.These results can aid in the improvement of the design for Li-SCs.When the cathode/anode mass ratio is 2/1,the comprehensive performance of Li-SC is the best.The capacity at 50C is 78.0%of that at 1C.The maximum power density and energy density at 2.3 V are 7247 W·kg^(-1) and 9.5 Wh·kg^(-1),respectively.The energy densities based on the mass of device and the active materials are increased to 20.2 Wh·kg^(-1) and 65.0 Wh·kg^(-1),respectively when the operating voltage is increased to 3.1 V.However,the wide operating voltage brings life attenuation.The capacity retention is 93.0%after 10000 cycles under 1-2.3 V,which is reduced to 84.5%after 5000 cycles under 0.5-2.5 V.The capacity at-40℃is 57.8%of that at 25℃,and the energy density is still 5 Wh·kg^(-1)(2.3 V).