Batteries using lithium metal as anode have exhibited the energy density over 500 Wh/kg. However, the practical application of lithium metal batteries (LMBs) is still severely limited by issues such as lithium dendrite formation, short cycle life, and low Coulombic efficiency of Li plating/stripping. The optimization of electrolyte formulations is known as an effective approach to conquering those challenges, in which the additive engineering is known as one of the most cost-effective methods for commercial applications. Nevertheless, to find an additive with multi-functions is a long-term challenge. Now, a team of researchers from Nankai University found electrolytes with boron additives can mitigate critical challenges of LMBs.
Screening B additives
The researchers explore four B additives as candidates with various functional group. Electrostatic potential (ESP) is used to find the best anion acceptors, in which tris(hexafluoroisopropyl)borate (THFPB) is endowed with maximum ESP of all B-ads. The sites with more positive value of ESP are known to easily occur in nucleophilic reactions and thus can strongly attract the small anions, acting as most promising additives of electrolytes.
Versatileness of B additives in lithium metal batteries.
The B additives are found to exhibit at least three merits in lithium metal batteries. 1) The strong electron-deficiency can assist the dissolution of Li 2 O, which can reduce the interfacial charge transfer resistance of Li metal anode. 2) Through dissolving LiF deposits within CF x pores, B additives can be further applied to Li/CF x batteries to increase lithium-ion diffusion coefficient, thus can largely improve the specific discharge capacity and increase the high-rate performance. 3) The oxidative decomposition of B additives at the cathode interface facilitates the formation of the robust cathode electrolyte interphase, which contributes to long cycling stability of high-voltage cathodes.
Science China Chemistry
Experimental study