电解液添加剂对高镍锂离子电池性能的影响

Effect of electrolyte additives on the performance of high nickel Li-ion battery

研究碳酸亚乙烯酯(VC)、1,3-丙烷磺酸内酯(PS)、氟代碳酸乙烯酯(FEC)和硫酸乙烯酯(DTD)等添加剂在高镍[n(Ni)≥80%]正极材料锂离子电池中的应用效果。对LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)|SiO_(x)/石墨软包装电池和Li|SiO_(x)/石墨扣式电池进行电化学性能、化成产气及负极界面形貌等分析。除PS外的添加剂,均不影响SiO_(x)/石墨电极的初始容量;VC、PS会增大SiO_(x)/石墨界面阻抗。VC、PS和FEC可减少软包装电池的化成产气,而DTD化成产气明显偏多,且主要为烷烃。使用FEC的电池,常温和低温倍率性能最好,25℃和-20℃放电容量,在0.5 C时为标称容量的92.0%和68.2%,在2.0 C时为75.2%和21.5%。使用FEC的电池在高温60℃下存储14 d,容量恢复率和保持率分别为63.3%和48.5%,电压降为2.7%;使用DTD的分别为72.4%、63.6%和1.3%。使用DTD和FEC的电池,分别拥有最好的高温和常温循环性能。SEM分析表明,使用FEC的电池中,高温循环后的SiO_(x)/石墨负极界面覆盖物较多,成膜较厚,表面粗糙。

Application effects of electrolyte additives,including vinylene carbonate(VC),1,3-propanesultone(PS),fluoroethylene carbonate(FEC),ethylene sulfate(DTD)in high nickel(Ni)[n(Ni)≥80%]cathode material Li-ion battery were studied.The electrochemical performance,syngas and morphology of anode interface of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)|SiO_(x)/graphite pouch battery and Li|SiO_(x)/graphite button cell were analyzed.Except for PS,the other additives did not influence the initial capacity of SiO_(x)/graphite electrode,VC and PS contributed to an increase of the interface impedance of SiO_(x)/graphite.For pouch battery,VC,PS and FEC could decrease the gas evolution,but the gas production of DTD increased and the main gases were alkanes.The battery using FEC owned the best room temperature and low temperature rate capability,the discharge capacity at 25℃and-20℃was 92.0%and 68.2%compared with nominal capacity at 0.5 C,75.2%and 21.5%at 2.0 C.After stored at 60℃for 14 d,the capacity recovery rate and retention rate were 63.3%and 48.5%for the battery using FEC,respectively,the voltage drop was 2.7%,the battery using DTD was 72.4%,63.6%and 1.3%,respectively.The battery using DTD and FEC had the best high temperature and room temperature cycle performance,respectively.SEM analysis showed that in the battery using FEC,the anode interface of SiO_(x)/graphite after high temperature cycle was covered with more coating materials,thick film formation and rough surface.