The (In-)Stability of the Ionic Liquids [(TMEDA)BH2][TFSI] and -[FSI] on the Li(001) Surface

• Electrolytes that can enable the use of a Li metal anode at a vast 3860 mAh/g, in place of currently used graphite anodes (372 mAh/g), are required for the advancement of next-generation rechargeable Li batteries. Both quaternary ammonium and boronium (trimethylamine)(dimethylethylamine)dihydroborate [NNBH2](+) cation-based ionic liquids (ILs) show high electrochemical stability windows and thermal stability for use in Li batteries. Cyclization of the former cation shows improved electrolyte stability compared to the open-chain counterpart. However, it is not known whether this is the case for the cyclic derivative of [NNBH2](+), N,N,N',N'-tetramethylethylenediamine)dihydroborate [(TMEDA)BH2](+). Here, the details of the initial stages of solid-electrolyte interphase (SEI) layer formation on a lithium metal surface, Li(001), for the [(TMEDA)BH2](+) based ILs are revealed using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. These indicate that [(TMEDA)BH2](+) remains intact, displaying a similarly weak interaction with the Li metal surface as the open-chain analogue. The chemical stability shown by the boronium cation indicates spontaneous and unwanted side reactions with the Li anode are unlikely to occur, which could help to facilitate long-term cycling stability of the battery. Altogether, the findings suggest the [(TMEDA)BH2](+) ILs, like their [NNBH2](+) IL counterparts, are viable candidates for rechargeable Li metal batteries.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

lithium battery

boronium cation

SEI layer

ionic liquids

Li metal anode

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