Toward the Sustainable Lithium Metal Batteries with a New Electrolyte Solvation Chemistry

Abstract

graphite has been the most commercially successful anode material for LIBs due to its low material cost and reduction potential (≈0.05 V vs Li/Li + ). However, graphite anodes limit the enhancement of energy density and charging rate due to their low theoretical capacity (375 mAh g −1 ) and staged lithium (de) intercalation mechanism, making it difficult to meet the expectation of cutting-edge electronic devices. [5,6] Hence, the development of metallic lithium as an anode is attracting great attention because of its exceptionally high specific capacity (3860 mAh g −1 ), small gravimetric density (0.534 g cm −3 ), and low negative electrochemical potential (−3.040 V vs the standard hydrogen electrode). [7][8][9] Therefore, theoretically, rechargeable batteries using Li metal (LMB) and a nickel-rich NCM cathode can easily surpass the energy density of state-of-the-art commercial LIBs using graphite, thereby achieving the goal of 300-400 Wh kg −1 for LIBs. [10] However, thermodynamic instability between Li metal and electrolyte during the charging process always causes an unavoidable parasitic process, wherein the electrolyte spontaneously reacts with the Li anode to deplete the electrolyte, thicken the solid electrolyte interphase (SEI), and induce dendritic growth of Li, resulting in low Coulombic efficiency (CE), rapid capacity drop, and safety concerns. [7,11,12] To alleviate these weaknesses of LMBs, many efforts, including electrolyte engineering, [4,13,14] use of a 3D host structure, [15,16] and artificial SEI engineering, [17,18] are being widely explored. Among these Herein, a new solvation strategy enabled by Mg(NO 3 ) 2 is introduced, which can be dissolved directly as Mg 2+ and NO 3 − ions in the electrolyte to change the Li + ion solvation structure and greatly increase interfacial stability in Li-metal batteries (LMBs). This is the first report of introducing Mg(NO 3 ) 2 additives in an ester-based electrolyte composed of ternary salts and binary ester solvents to stabilize LMBs. In particular, it is found that NO 3 − efficiently forms a stable solid electrolyte interphase through an electrochemical reduction reaction, along with the other multiple anion components in the electrolyte. The interaction between Li + and NO 3 − and coordination between Mg 2+ and the solvent molecules greatly decreases the number of solvent molecules surrounding the Li + , which leads to facile Li + desolvation during plating. In addition, Mg 2+ ions are reduced to Mg via a spontaneous chemical reaction on the Li metal surface and subsequently form a lithiophilic Li-Mg alloy, suppressing lithium dendritic growth. The unique solvation chemistry of Mg(NO 3 ) 2 enables long cycling stability and high efficiency of the Li-metal anode and ensures an unprecedented lifespan for a practical pouch-type LMB with high-voltage Ni-rich NCMA73 cathode even under constrained conditions.

A highly stable lithium metal anode enabled by Ag nanoparticle–embedded nitrogen-doped carbon macroporous fibers

“…However, the uncontrollable growth of Li dendrites and collapse of the solid electrolyte interphase (SEI) layer lead to low Coulombic efficiency (CE) and deteriorated cycling performance, which largely restrict the practical application of the Li metal anode (LMA) (7)(8)(9)(10)(11)(12)(13). Considerable efforts have been made to regulate the Li plating/ stripping behaviors for stable Li metal batteries, including developing functional electrolytes (14)(15)(16)(17)(18), constructing well-designed three-dimensional (3D) host structures (19)(20)(21)(22)(23)(24), and using artificial protection layers (25)(26)(27)(28)(29)(30). Despite much progress (31,32), it remains a challenge to explore LMA with stable cycling life over 500 cycles at practical current densities greater than 1 mA cm −2 .…”

Ion‐Dipole Chemistry Drives Rapid Evolution of Li Ions Solvation Sheath in Low‐Temperature Li Batteries

“…Lithium-ion batteries (LIBs) with graphite anode have made a great impact on society, recognized by the Nobel Prize in Chemistry. [1] Following decades of commercialization, graphite copper fluoride, [11] magnesium nitrate, [12] tin trifluoromethanesulfonate, [13] and γ-butyrolactone, [14] lithium nitrate (LiNO 3 ) has been used to take part in the solvation sheath and produces Li + -conducting SEI layer. High-concentration electrolytes are also developed to improve the ratio of anions in the solvation sheath, leading to primarily inorganic SEI and better Li cyclability.…”

Constructing nitrided interfaces for stabilizing Li metal electrodes in liquid electrolytes

“…Apart from LiNO 3 , some other N-containing additives can also be used to build nitrided SEI for Li metal electrodes. In this regard, Sun et al reported that Mg(NO 3 ) 2 can be dissolved in carbonate-based electrolyte as an additive 96. They suggested that Mg(NO 3 ) 2 can be dissolved directly as Mg 2+ and NO3 − …”