Dendrite-Free Lithium Deposition with Self-Aligned Columnar Structure in a Carbonate–Ether Mixed Electrolyte

Cheng

2017

Adv Materials Inter

229

143

on Li metal anode paired with sulfur/ oxygen cathode is highly concerned. [6] Li metal has extremely high theoretical specific capacity (3860 mA h g −1 ), nearly ten times higher than that of graphite anode, and the lowest reduction potential (−3.040 V vs. standard hydrogen electrode), which has been considered as a 'Holy Grail' anode in rechargeable batteries. [7] Moreover, Li metal anode can be paired with different cathode materials, such as intercalated cathodes (e.g., LiFePO 4 , [8] LiNi x Co y Mn 1−x−y O 2 [9,10] ) and conversion cathodes (e.g., S, [11,12] O 2 [13] ), to construct different types of high energy density batteries. The specific energy densities of Li metal batteries are very hopeful to approach 500 Wh kg −1 in the next 5 to 10 years according to the goal of US Department of Energy.Nevertheless, the rechargeable Li metal batteries have not been large-scale released yet. Li metal anode was first applied in Li-TiS 2 rechargeable batteries. In 1980s, the first-generation rechargeable Li metal batteries were commercialized by MOLI energy. [14] However, there were incessant reports about the fires and explosion events of rechargeable Li metal batteries. Safety issue has been the grand challenge hindering the practical applications of Li metal batteries since then. The main origin of safety issue comes from Li dendrites, i.e., random and spiculate Li deposition, which is induced by unstable interfaces between Li metal and liquid electrolyte. [2,15] Due to its extreme reactivity, Li metal can react with nearly all electrolytes, inducing the spontaneous decomposition of organic electrolyte. [16] The reaction products between Li and electrolyte constitute the solid electrolyte interphase (SEI) on Li metal anode, which was first named by Peled in 1979. [17] However, the formed SEI is fragile and heterogeneous with varied spatial resistance, [18,19] which induces uneven Li ions flux and random Li deposition underneath. Consequently, the surface of Li metal in a working cell is not uniform, where there are many protuberances enhancing the local electric field and attracting Li ions to deposit. [20] When the Li ion concentration near anode surface decreases to zero at the characteristic time (named as Sand's time), [21] scarce Li ions aggravate the nonuniformity of Li deposition and accelerate the growth of Li dendrites, which is a self-amplifying process. [22] The dendritic Li can easily pierce fragile SEI and induce the rapid decomposition of liquid electrolyte to form new SEI. [19,23] In the subsequent stripping process, gracile Li dendrites may break from the roots forming dead Li. [24] The repeated formation of SEI and dead Li give rise to low Coulombic efficiency. [15] Additionally, interfacial resistance Lithium metal has been considered as one of the most promising anode materials in high-energy-density rechargeable batteries due to its extremely high specific capacity and very low reduction potential of all possible candidates. However, the mysterious interfacial phenomena of lithium metal ano...

Section: | Liquid Electrolytementioning

confidence: 99%

Section: | Liquid Electrolytementioning

confidence: 99%

Advances in Interfaces between Li Metal Anode and Electrolyte

Cheng

2017

Adv Materials Inter

229

143

“…20 Recently, H. Yu et al exhibited a self-aligned columnar structure with smooth and dendrite-free Li deposition in a carbonate-ether mixed electrolyte. 21 R. Xu et al presented an artificial soft-rigid protective layer for dendrite-free Li metal anode. 22 S. Choudhury et al reported a highly reversible Li metal battery based on crosslinked hairy nanoparticles, which can afford enhanced mechanical strength and good ionic conductivity.…”

Section: Rechargeable Lithium Metal Battery Has Been Regarded As One mentioning

confidence: 99%

An ultrafast rechargeable lithium metal battery

Guo

Deng

et al. 2018

J. Mater. Chem. A

“…[14] Thed ifference in local ion-solvent structures is believed to give new insights.T hese future insights are expected to revolutionize current electrolyte recipes. [15] Third, since most of the organic solvents are intrinsically reducible by Li and Na while ion-solvent complexes ubiquitously exist in any known electrolyte system, designing an artificial or in situ protective layer on the alkali metal anode to prevent its direct contact to unstable ion-solvent complexes emerges as amore promising…”

mentioning

confidence: 99%

Ion–Solvent Complexes Promote Gas Evolution from Electrolytes on a Sodium Metal Anode

et al. 2017

Lithium and sodium metal batteries are considered as promising next-generation energy storage devices due to their ultrahigh energy densities. The high reactivity of alkali metal toward organic solvents and salts results in side reactions, which further lead to undesirable electrolyte depletion, cell failure, and evolution of flammable gas. Herein, first-principles calculations and in situ optical microscopy are used to study the mechanism of organic electrolyte decomposition and gas evolution on a sodium metal anode. Once complexed with sodium ions, solvent molecules show a reduced LUMO, which facilitates the electrolyte decomposition and gas evolution. Such a general mechanism is also applicable to lithium and other metal anodes. We uncover the critical role of ion-solvent complexation for the stability of alkali metal anodes, reveal the mechanism of electrolyte gassing, and provide a mechanistic guidance to electrolyte and lithium/sodium anode design for safe rechargeable batteries.