Effect of Dual‐Salt Concentrated Electrolytes on the Electrochemical Performance of Silicon Nanoparticles

Abstract As a promising anode material, silicon has attracted extensive attention. The instability of the electrode/electrolyte interphase due to the inherent volume variation upon (de)lithiation is one of the major factors limiting the commercialization of silicon anode materials. Here, we report a concentrated electrolyte with lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluoro (oxalate) borate (LiDFOB) dual salt to enhance the control of the species constituting the solid electrolyte interphase (SEI) on the surface of the silicon material. The silicon nanoparticle (SiNP) electrode with the dual‐salt LiFSI 0.7 LiDFOB 0.3 ‐(PC) 4 concentrated electrolyte delivers a relatively high average coulombic efficiency of 97.68 % and a remarkably improved cycling performance with an initial capacity of approximately 3300 mAh g −1 and a capacity retention around 2000 mAh g −1 after 100 cycles. It is found that the polarity of the B−F bond of LiDFOB decreases when the molar ratio of LiDFOB to LiFSI is greater than 0.3 : 0.7. Therefore, the reduction of LiDFOB through a ring‐opening reaction coupled with a ring‐opening reaction of PC becomes dominant. The SEI layer rich in the corresponding products Li(BF 2 O) n polymer could suppress the rupture of the Si particles and excessive growth of the SEI layer, thus could further mitigate the decrease of coulombic efficiency.