Effects Of Sulfur-containing Electrolyte Additives On High-voltage Lithium Ion Batteries

In order to obtain higher energy density lithium-ion battery system,the development of high-voltage electrolytes has become more and more important.At present,the traditional electrolytes are mainly composed of LiPF6 and organic carbonates.However,the performance of lithium-ion battery decreases seriously,because of the instability of carbonate electrolytes at high voltage.Adding a small amount of additive into the electrolytes is a simple and cost-effective way to solve problem.In the specific research,1M LiPF6-EC/EMC(1:1)was chosen as the base electrolytes.The effects of sulfur-containing additives on LiNi,/3Co1/3Mn1/3O2(NMC111)/Li and graphite/Li half-cells were investigated.The related factors were also investigated via theoretical calculation,electrochemical test and electrode morphology test.The conclusions are shown as follows:1.The effects of BS as an electrolyte additive on batteries(1)3%BS is the optimum concentration to improve the cycle performance of LiNi1/3Co1/3Mn1/3O2(NMC111)/Li half-cell.The capacity retention of the 3%BS-containing battery is 86.9%after 80 cycles.In contrast,the capacity retention of the base battery is only 69%.(2)BS can preferentially redox to form a SEI film on NMC111 electrode,which can inhibit the decomposition of electrolytes and prevent structure collapses of electrode,thus improving the electrochemical performance of the battery.(3)BS also plays an important role in improving the cycle performance of NMC111/graphite full-cell and graphite/Li half-cell.2.The effects of PES as an electrolyte additive on batteries(1)2%PES can effectively improve the cycle performance of NMC111/Li.It is worth mentioning that 2%PES has a remarkable effect in improving the rate performance of NMC111/Li half-cell.(2)When PES is added into graphite/Li half-cell,it can be reduced preferentially at 1V on the anode electrode.The cycle performances of NMC111/graphite full-cell and graphite/Li half-cell are also improved by adding PES.