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

Abstract

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 ...

Recent Progress in Designing Stable Composite Lithium Anodes with Improved Wettability

“…It is desirable to develop a versatile and facile approach for entrapping Li inside porous scaffolds to create 3D composite Li anodes. Li metal has a low melting point of 180°C, and thus, thermal infusion strategies in which molten Li is infused into a "lithiophilic" matrix have been developed, [34][35][36] but the underlying wetting mechanism is not fully understood. Understanding the underlying wetting mechanism, and thus how to tune the microstructure/composition on substrate surfaces or Li droplet characteristics, provides a guide for designing stable Li metal composite anodes.…”

Controlled Growth of Li Dendrite Induced by Periodic Ni Mesh for Ultrastable Lithium Metal Battery

“…and 3D framework anode, [18][19][20][21] have been proposed to solve abovementioned problems. For instance, Yang's group suppressed Li dendrites by designing a vertical MXene-Li array with adjustable MXene walls.…”

Super Electrolyte-Philic Boron Nitride Nanotube Membranes as Highly Robust Separators for Lithium Batteries

“…+ ) is a critical parameter when evaluating the ionic conductivity for Liion batteries. Low t Li + gives rise to concentration polarization, leading to side reactions, dendrite growth and joule heating, which can shorten cycling life and cause catastrophic failure especially under fast charging/discharging condition 38,39 . It is thus important to determine the extract t Li + .…”

“…Such dendrite formation can be largely attributed to ine cient Li + transport that leads to concentration polarization and uneven charge distribution 38 . It is important in controlling Li dendrite formation by alleviating the anion depletion-induced large electric elds near the Li anode.…”