Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All‐In‐One Separator

Abstract

vs SHE) and tenfold increased theoretical specific capacity (3860 mA h g −1 ) [6,7] than graphite anode (376 mA h g −1 ). [8][9][10] Despite these fundamental advantages, Li metal anodes still suffer from the inevitable formation of Li dendrites, resulting in reduced long-term performance and undesirable internal short circuits. [11][12][13][14] Thus, it is essential to develop a novel strategy to effectively suppress the formation of Li dendrites by manipulating the nucleation and growth behavior of Li deposits during cycling.According to Sand's time model, increasing the Li + transference number is a feasible strategy to reduce the concentration overpotential in the electrolyte and to suppress the diffusion-limited growth of Li dendrites. [15][16][17][18][19] The most intuitive approach to achieve this is the modification of the electrolyte composition; however, there are few electrolyte compositions that can fulfill the various requirements of LMBs in terms of ionic conductivity, chemical/electrochemical stability, and safety. Instead, introducing functional materials with high polarity onto the separator provides a practical approach for improving the Li + transference number because it allows a direct interaction between functional materials and electrolyte solvents. [20][21][22][23][24] However, it would be difficult to completely alter the inherent properties of the separator via a conventional coating process, whichThe uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO 3 nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO 3 nanoparticles and the polar solvent reduces the ionic radius of the Li + -solvent complex, thus increasing the Li + transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO 3 nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi 2 at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.

A sacrificial separator facilitating in situ creation of a durable CEI layer and tailoring lithium dendrites for practical lithium metal batteries

“…Lithium-metal batteries (LMBs) coupled with NCM811 cathodes are considered a standard combination for achieving high-energy-density LMBs. 1–3 Theoretically, the energy density of LMBs assembled with Li metal and NCM811 is ∼500 W h kg −1 , which is almost two times higher than that of traditional lithium-ion batteries (∼250 W h kg −1 ) composed of commercial graphite and lithium cobalt oxide electrodes. 4–8 However, the commercialization of LMBs comprising NCM811 remains challenging owing to the severe degradation of the electrochemical performance caused by the concurrent occurrence of two adverse effects: uncontrollable dendritic Li growth and the morphological irregularity of NCM811.…”

Improvement of the Li metal-electrolyte interfacial stability by cis–trans polar conformer formation in a carbonate electrolyte

“…However, lithium metal electrodes suffer from dendritic growth during cycling, which causes continuous electrolyte consumption and ultimately decreases the lithium metal battery (LMB) capacity. 4,7–10 Subsequent electrolyte decomposition on the dendritically grown Li metal surface leads to excess electrolyte injection into the LMB, which greatly decreases the practical specific energy of the cell from the flooded electrolyte. 11,12 Thus, preventing cathodic electrolyte decomposition on the Li electrode is crucial to improve the LMB performance.…”