Few-Layer Graphene Island Seeding for Dendrite-Free Li Metal Electrodes

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%

Advances in Interfaces between Li Metal Anode and Electrolyte

Cheng

2017

Adv Materials Inter

229

143

Section: New Strategies For Protecting LI Metal Anode In Li–s Batteriesmentioning

confidence: 99%

“…A large range of different carbon‐based materials have been used as the protective layers of Li metal anodes including interconnected hollow carbon nanospheres, a carbon nanofiber network, nitrogen‐doped graphene sheets, graphite, layered reduced graphene oxide, a 3D porous carbon matrix, an unstacked graphene framework, and a 3D graphene@Ni scaffold . Carbon‐based materials are the ideal interfacial layer for the Li metal anode because of their chemical stability in a highly reducing environment, strong mechanical flexibility, and excellent electrical conductivity.…”

Section: New Strategies For Protecting LI Metal Anode In Li–s Batteriesmentioning

confidence: 99%

“…The island‐type, nitrogen‐doped graphene coated Cu substrates as electrodes for Li metal storage exhibit stable voltage profiles and excellent efficiency retention over 100 cycles at a current density of 2 mA cm −2 in an electrolyte (1 m LiTFSi in DME: DIOX (1:1, vol%)) without additives between −1.0 and 2.0 V, because it could limit the initial Li metal nucleation and growth. It is concluded that the interlayers of graphene sheets play the role of a seed site for the initial Li metal nucleation, and Li ions are first inserted into them during the charge process.…”

Section: New Strategies For Protecting LI Metal Anode In Li–s Batteriesmentioning

confidence: 99%

See 1 more Smart Citation

Anode Improvement in Rechargeable Lithium–Sulfur Batteries

et al. 2017

Owing to their theoretical energy density of 2600 Wh kg , lithium-sulfur batteries represent a promising future energy storage device to power electric vehicles. However, the practical applications of lithium-sulfur batteries suffer from poor cycle life and low Coulombic efficiency, which is attributed, in part, to the polysulfide shuttle and Li dendrite formation. Suppressing Li dendrite growth, blocking the unfavorable reaction between soluble polysulfides and Li, and improving the safety of Li-S batteries have become very important for the development of high-performance lithium sulfur batteries. A comprehensive review of various strategies is presented for enhancing the stability of the anode of lithium sulfur batteries, including inserting an interlayer, modifying the separator and electrolytes, employing artificial protection layers, and alternative anodes to replace the Li metal anode.

“…Solid or polymer electrolytes are promising to suppress the lithium dendrite growth if the issues of lithium penetration through the cracks or grain boundaries of the solid electrolyte can be solved, together with some other issues such as lower ionic conductivity or interface reaction of solid and polymer electrolytes . As an alternative, ex situ coated artificial SEI layers such as polydimethylsiloxane (PDMS), boron/graphene, or silica layer present efficient interfacial protection.…”

Section: Introductionmentioning

confidence: 99%

A Versatile Strategy to Fabricate 3D Conductive Frameworks for Lithium Metal Anodes

Shang

Chen

et al. 2018

Adv Materials Inter

and uniformity of the solid electrolyte interphase (SEI) layer by optimizing electrolyte components including adding Cs + and Rb + , [3] LiF, [4] vinylene carbonate (VC), [5] or Li 2 S 8 . [6] However, due to the "hostless" nature of Li metal with volume expansion toward the separator, [7] cracking SEI layers upon cycling can expose the fresh Li metal upon further reaction. Solid or polymer electrolytes are promising to suppress the lithium dendrite growth if the issues of lithium penetration through the cracks or grain boundaries of the solid electrolyte can be solved, together with some other issues such as lower ionic conductivity or interface reaction of solid and polymer electrolytes. [8] As an alternative, ex situ coated artificial SEI layers such as polydimethylsiloxane (PDMS), [9] boron/graphene, [10] or silica layer [11] present efficient interfacial protection.Recently, various novel "host" designs have demonstrated their power in changing the Li plating behavior. Conductive micro-/ nanostructure frameworks have proved to be an effective method to ensure uniform Li deposition and to accommodate the Li volumetric expansion [8g] ; these frameworks include the layered reduced graphene oxides, [2b,12] nickel (Ni) foam, [13] and metal-coated sponges. [14] However, the expensive and complex fabrication process may limit practical applications. Developing a simple, lowcost, and versatile technique that can transform materials into 3D conductive frameworks remains a challenge in this field.In this work, we demonstrate a novel strategy that can implement such a transformation at large scale. [15] Through two simple The suppression of lithium dendrite is critical to the realization of lithium metal batteries. 3D conductive framework, among different approaches, has shown very promising results in dendrite suppression. A novel cost-effective and versatile dip-coating method is presented here to make 3D conductive framework. Various substrates with different geometries are coated successfully with copper, including electrically insulating glass fiber (GF) or rice paper and conducting Ni foam. In particular, the as-prepared copper coated GF shows promising results to serve as the lithium metal substrate by the electrochemical battery tests. The method significantly broadens the candidate materials database for 3D conductive framework to include all kinds of intrinsically insulating 3D substrates.