Protecting the Li‐Metal Anode in a Li–O₂ Battery by using Boric Acid as an SEI‐Forming Additive

Abstract

The Li-O battery (LOB) is considered as a promising next-generation energy storage device because of its high theoretic specific energy. To make a practical rechargeable LOB, it is necessary to ensure the stability of the Li anode in an oxygen atmosphere, which is extremely challenging. In this work, an effective Li-anode protection strategy is reported by using boric acid (BA) as a solid electrolyte interface (SEI) forming additive. With the assistance of BA, a continuous and compact SEI film is formed on the Li-metal surface in an oxygen atmosphere, which can significantly reduce unwanted side reactions and suppress the growth of Li dendrites. Such an SEI film mainly consists of nanocrystalline lithium borates connected with amorphous borates, carbonates, fluorides, and some organic compounds. It is ionically conductive and mechanically stronger than conventional SEI layer in common Li-metal-based batteries. With these benefits, the cycle life of LOB is elongated more than sixfold.

Electrolytes for Rechargeable Lithium–Air Batteries

“…In addition, the concentrations of Li salts and additives related to the formation of stable SEI layers require further optimization . Novel solvents, Li salts, and additives should be discovered through the continuous innovation …”

“…[219] Novel solvents,L is alts,a nd additives should be discovered through the continuous innovation. [220] Solid-state electrolytes have great potential for use in Liair batteries to realize open systems with good safety and high energy density.S PEs such as PVDF-HFP,P EO,a nd PMMA as well as SIEs such as NASICON and garnet are considered promising solid electrolytes for Li-air batteries.H owever, their ionic conductivity and stability still need to be improved. Solid composite electrolytes have been developed to combine the advantages and overcome the drawbacks of two or more solid matrixes including SPEs,S IEs,a nd passive fillers.A s research in this direction is still at the initial stage,a ll-solidstate Li-air batteries using solid electrolytes or solid composite electrolytes still face many challenges,f or example, limited ionic conductivity and stability,a nd poor interface chemistry with the electrodes.Solid-liquid composite electrolytes combine the fluidity of non-aqueous liquid electrolytes with the favorable mechanical properties of solid matrixes.…”

Constructing Co3O4 Nanowires on Carbon Fiber Film as a Lithiophilic Host for Stable Lithium Metal Anodes

“…[7][8][9][10][11] However, the practical applications of lithium metal anode are still impeded by many critical problems including severe lithium dendrite growth, infinite volume change of lithium foil, and unstable solid liquid interphase (SEI) film in the process of repeated charge/discharge cycles, which results in short cycle life, massive discharge capacity loss, and battery short circuit accompanied by battery failure, thermal runaway, and safety risks. [12][13][14] Many approaches have been tried to regulate the undesired lithium dendritic formation, including designing various functional electrolyte additives, [15][16][17][18][19][20] creating artificial SEI films (i. e. LiF, [21][22][23] LiCl, [24] phosphorene, [25] Nafion/TiO 2 , [26] and MoS 2 , [27] ) and use of 3D current collectors [28][29][30] to regulate the lithium deposition. Moreover, modifying the polypropylene separators via coating functional nanocarbon (FNC) is adopted to control the dendrite growth direction for making lithium metal anode rechargeable in the iterant charge/discharge cycles.…”

Strategies Toward Stable Nonaqueous Alkali Metal–O2 Batteries

“…[64] Metal ions, which are electrochemical active and are easily reduced by alkali metal, can be used as promising additives for SEI formation, such as Ge 4+ . [66] BA can chemically react with Li anode to form an ionically conductive and mechanically strong film composed of nanocrystalline (Li 2 O) m (B 2 O 3 ) n , Li 2 CO 3 , LiF, and some organic compounds (Figure 7b). [65] After polished and immersed in GeCl 4 /tetrahydrofuran (THF) stream for several minutes, the surface of Li foil turned black, which contains Ge, GeO x , Li 2 CO 3 , LiOH, Li 2 O, and LiCl species.…”

“…Considering the limited amount of active Li in lithiated silicon, side reactions between limited Li and O 2 species/moisture in the electrolyte have a great impact on cell's capacity retention. [66] Copyright 2018, Wiley. A lithium-ion oxygen battery employing commercial Si particles as anode material was proposed and exhibited long cycling stability of 100 cycles in the LiTFSI/TEGDME electrolyte with a Ru decorated carbon cathode (Figure 8a,b).…”