Juggling Formation of HF and LiF to Reduce Crossover Effects in Carbonate Electrolyte with Fluorinated Cosolvents for High‐Voltage Lithium Metal Batteries

Abstract

Fluorinated solvents emerge as a promising strategy to improve performance of lithium metal batteries (LMBs). However, most of them are prone to produce corrosive HF and deteriorate electrode interface, inducing cathode-to-anode detrimental crossover of transition metal-ions. Here, fluorinated aromatic hydrocarbons in dimethyl carbonate (DMC)-based diluted highly concentrated electrolyte (DHCE) are employed to juggle formation of HF and LiF, enabling stable cycling of high-voltage LiNi 0.7 Co 0.1 Mn 0.2 O 2 (NCM712) and LiCoO 2 (LCO). The nature of aromatics in this carbonate-based DHCE makes them difficult to undergo β-hydrogen assisted defluorination, evidencing by the high energy barrier and high bond energy of β-sites hydrogen. The advanced DHCE restrains HF formation but strengthens LiF formation, which not only suppresses impedance growth, transition-metal dissolution, and stress crack on the cathode, but achieves highly reversible Li stripping/plating with an outstanding average Coulombic efficiency up to 99.3%. The Li||NCM712 cell and Li||LCO cell both exhibits superior cycling stability at high operation voltage. Even under stringent conditions, the 4.4 V Li||NCM712 full battery retains >95% of the initial capacity over 100 cycles, advancing practical high-voltage LMBs. This study designs an efficient electrolyte that generates robust electrode/electrolyte interphases and restrains by-products formation spontaneously, thus shedding new light on electrolyte toward applicable LMBs.

Recent advances of structural/interfacial engineering for Na metal anode protection in liquid/solid-state electrolytes

“…Significant advancements have been made in the study of lithium metal batteries because LiF is one of the primary elements of the SEI barrier. 83,84 Similarly, NaF could be used to enhance the stability of SEI layers on Na anode by fluoridating the solvents in SMBs.…”

A “tug-of-war” effect tunes Li-ion transport and enhances the rate capability of lithium metal batteries

“…13 Although these promising electrolytes provide high CE (>99%) and derive robust SEI and cathode electrolyte interphase (CEI) on both the LMA and cathode, the limited rate performance of LMBs cannot meet the demand for commercialization. [14][15][16][17][18][19][20][21][22][23][24][25][26] Specically, ionic conductivity and the Li + transference number (T Li +; ionic current is carried predominantly by Li + ) are two critical parameters to measure the mobility of Li + in electrolytes. The low mobility of Li + will aggravate the concentration polarization in the electrolyte, thereby accelerating the formation of lithium dendrites.…”

Quasi‐Localized High‐Concentration Electrolytes for High‐Voltage Lithium Metal Batteries

“…[17] Furthermore, the highly reactive de-lithiated cathode at high charge cutoff voltages (>4.3 V) can even cause carbonate electrolyte decompositions and leakage of metal dissolution. [5,18,19] Such issues are even more formidable in highly demanding conditions, where a highloading cathode, a thin Li anode, and even a limited amount of electrolyte are required, presenting greater challenges for highvoltage electrolytes.…”