Prestoring Lithium into Stable 3D Nickel Foam Host as Dendrite‐Free Lithium Metal Anode

hydrogen electrode). [5,6] In fact, lithium metal has been applied in space exploration, petroleum prospecting in 1970s. However, the further application of LMB is plagued with practical issues that puzzled researchers for more than 40 years. [7,8] The most critical issue is that deposition of lithium metal tends to be highly dendritic during the repeated plating and dissolution process, which not only continue to consume the electrolyte and induce the "dead lithium" leading to capacity fading, but also face the severe safety problems of short-circuit due to the crack of separator by continuous ramified growth of lithium dendrites. [9,10] During the past half-century, many up-and-coming methods have been carried out to suppress dendrite growth and achieved partially success. These strategies can be broadly divided into three areas: i) electrolyte modification (such as selfhealing electrostatic shield mechanism by inducing Cs + , [11] replacing traditional liquid electrolyte by solid state electrolyte [12] ), ii) artificial solidelectrolyte interphase (SEI) (such as manufacturing the Li 3 N, [13] LiF, [14] Li-Sn alloy [15] layers to improve the mechanical strength, ionic diffusion performance, and stability to suppress the dendrite); iii) the multifunctional nanostructured anodes design to manipulate the nucleation of lithium (such as Ni foam, [16] 3D skeleton Cu matrix, [17] Cu-Zn alloy matrix [18] ). The former two strategies are based primarily on suppressing the protrusions, while the last one mainly focuses on modulating the initial nucleation process of dendrite, before the extension of dendrites into the electrolyte. Designing the excellent LMB requires the joint effort of these methods. However, if we can eliminate or mitigate the lithium dendrite from the initial nucleation process, it will be a highly efficient and convenient measure for its industrial production. Thus, finding an ideal nucleating anode material is very important to solve the dendrite problem.Based on Chazalviel's theory, [19,20] designing high-surface area anode can suppress the local current density and thus improve the electrical performance. Graphene, who possesses very high specific surface area, shows great advantage on its potential application in lithium metal anode field. [21][22][23] However, the pristine graphene (PG) shows poor performances in the actual application. [24][25][26] Doping or modulating the graphene can adjust its performance which has already made some Lithium metal is the most promising anode material for next-generation batteries, owing to its high theoretical specific capacity and low electrochemical potential. However, the practical application of lithium metal batteries (LMBs) has been plagued by the issues of uncontrollable lithium deposition. The multifunctional nanostructured anode can modulate the initial nucleation process of lithium before the extension of dendrites. By combing the theoretical design and experimental validation, a novel nucleation strategy is developed by introducing sulfur (S) to gr...

mentioning

confidence: 99%

S‐Doped Graphene‐Regional Nucleation Mechanism for Dendrite‐Free Lithium Metal Anodes

Wang

Zhai

Legut

et al. 2019

“…The solid electrolyte interface (SEI) layer on the surface of the electrodes, which may not accommodate the volume change, will be repeatedly break and form during continuous cycling. [28] To solve this problem, the 3D porous current collectors were used as host structures for Li metal in recent studies, such as 3D porous copper current collectors, [29][30][31][32][33] 3D nickel foam host, [34] and graphene [35,36] electrode. [21,22] These severe problems impede the practical applications of Li metal anodes and the approach to solve these multifaceted problems would be imperative.…”

mentioning

confidence: 99%

N‐Doped Graphene Modified 3D Porous Cu Current Collector toward Microscale Homogeneous Li Deposition for Li Metal Anodes

Zhang

Wen

Wang

et al. 2018

169

105

standard hydrogen electrode). [6][7][8][9][10] Unfortunately, the uneven plating/stripping of Li metal causes uncontrolled Li dendrite growth, which induces a series of problems. First, the continuous growth of Li dendrites may puncture the separator and cause short circuit, consequently resulting in serious safety issues. [11][12][13][14] Second, Li dendrite growth can consume electrolyte and dendritic Li may lose its electronic contact with electrode (called "dead Li") during Li stripping process, accordingly reducing the Coulombic efficiency (CE) and leading to capacity fading. [15][16][17] In addition, different from the other anode materials, the relative volume change of Li metal anodes is infinite due to its "hostless" nature, leading to internal pressure changes and interfacial fluctuations. The solid electrolyte interface (SEI) layer on the surface of the electrodes, which may not accommodate the volume change, will be repeatedly break and form during continuous cycling. [18][19][20] Moreover, the broken SEI will greatly exacerbate the uneven Li electrodeposits nucleate and accelerate the growth of Li dendrites. [21,22] These severe problems impede the practical applications of Li metal anodes and the approach to solve these multifaceted problems would be imperative.To tackle these critical issues, tremendous efforts have been taken to improve the stability of Li metal anodes and the SEI from different perspectives. In order to stabilize the SEI layer, various electrolyte additives, such as Cs + and Rb + ions, LiF, Li 2 S 8 , and LiNO 3 , were used. [23][24][25] Introducing nanoscale interfacial layers has also been intensively investigated (such as interconnected carbon nanospheres [26] and hexagonal boron nitride [27] ), where repeated deposition/stripping of Li under the layers exhibited stable CE. However, the above-mentioned methods based on Li foil (2D Li metal anodes) could not effectually prevent the huge volume change upon stripping/plating of Li metal. Thus, the internal pressure changes and interfacial fluctuations still happened during cycling. [28] To solve this problem, the 3D porous current collectors were used as host structures for Li metal in recent studies, such as 3D porous copper current collectors, [29][30][31][32][33] 3D nickel foam host, [34] and graphene [35,36] electrode. As a major part of Li metal batteries, the current collector has direct influence Lithium metal is the most promising anode material for high-energy-density batteries due to its high specific capacity of 3860 mAh g −1 and low reduction potential of −3.04 V versus standard hydrogen electrode. However, huge volume change, safety concerns, and low efficiency impede the practical applications of Li metal anodes. Herein, it is shown that the nitrogen-doped graphene modified 3D porous Cu (3DCu@NG) current collector can mitigate the above problems. The N-doped graphene, coating on the surface of 3D current collector, not only contributes to a uniform Li + flux, but also leads to a scattered distribution of electrons t...

“…[13,14] The "dead" Li with high impedance leads to poor kinetics and shortened lifespan of the battery. [20][21][22][23][24][25][26] A series of host frameworks have been reported, such as 3D CoO/Ni foam skeleton, [27] coralloid carbon fiber scaffolds, [28] lithiophilic Cu-Ni core-shell nanowire network, [29] and 3D carbon fiber framework. One approach is the coating of an artificial SEI with high mechanical strength onto the electrode surface.…”

mentioning

confidence: 99%

“Top‐Down” Li Deposition Pathway Enabled by an Asymmetric Design for Li Composite Electrode

Yue

Bao

et al. 2019

safety issue due to dendrite growth during the repeated Li stripping/plating process. [7][8][9] On one hand, the surface defects of the bare Li serve as the active sites to increase the local current density, leading to uneven Li deposition. [10] On the other hand, the "hostless" feature of Li metal results in huge volume change during cycling, causing unstable solid electrolyte interphase (SEI). [11] As a result, the fresh Li exposure created by SEI fracturing consumes electrolyte continuously, leading to low coulombic efficiency. [12] As such, the Li dendrites develop in an uncontrolled fashion that can eventually pierce the separator and cause short circuit. Moreover, the fractures of dendrites during repeated Li deposition/stripping result in "dead" Li sections composed of isolated Li fragments surrounded by e −insulating SEI. [13,14] The "dead" Li with high impedance leads to poor kinetics and shortened lifespan of the battery. [15] In order to inhibit Li dendrite growth and build stable SEI layers, considerable efforts have been made. One approach is the coating of an artificial SEI with high mechanical strength onto the electrode surface. [16][17][18][19] However, because of the volume change of Li metal, the structural integrity of the protective layers is hard to be maintained during prolonged running. In order to remit the volume change, great efforts have been made to design porous frameworks to accommodate Li. [20][21][22][23][24][25][26] A series of host frameworks have been reported, such as 3D CoO/Ni foam skeleton, [27] coralloid carbon fiber scaffolds, [28] lithiophilic Cu-Ni core-shell nanowire network, [29] and 3D carbon fiber framework. [30] The host frameworks can not only accommodate the volume change of Li during cycling, but also reduce the local current density. [31][32][33][34] More importantly, the porous structure of these frameworks can suppress the dendrite formation by changing Li plating/ stripping behavior. [35][36][37] It should be noted that most of the reported composited electrodes possess symmetric structure for their two sides, especially for the electrodes fabricated by thermal infusion method. [38] However, as the anode for the battery, the two sides of the electrode are in different environments: one side contacts with the separator, while the other side faces the current collector. The requirements and functions for the two sides are thus quite different. [39] The side facing the separator should be facile for Li-ion transportation.Designing Li composite electrodes with host frameworks for accommodating Li metal has been considered to be an effective approach to suppress Li dendrites. Herein, an asymmetric design of a Mo net/Li metal film (MLF) composite electrode is developed by an inverted thermal infusion method. The asymmetric MLF electrode has a dense oxide passivated layer on the top side, a porous Mo net matrix on the back side, and active Li layer in between. The back side has a larger specific area and higher electric field than the top side, which contacts with ...