Electrochemical Diagram of an Ultrathin Lithium Metal Anode in Pouch Cells

Abstract

potential (−3.04 V vs the standard hydrogen electrode). [2] The application of Li metal anode can further boost the specific energy density of next-generation battery systems (such as solid-state cells, Li-S, and Li-air batteries) theoretically by three to six times relative to the current Li-ion batteries. [3] However, notorious safety hazard, low Coulombic efficiency (CE), as well as short lifespan due to the unsteady solid electrolyte interphase (SEI) and dendritic Li deposition impede the practical implementation of Li metal batteries (LMBs) seriously. [4] Many emerging strategies are proposed to protect the Li metal anode, such as interface regulation, [5] modified electrolyte, [6] localized high-concentration electrolytes, [7] and artificial protective layer. [8] Solid-state electrolytes are introduced into LMBs for high safety, [9] and threedimension (3D) lithiophilic hosts are introduced to inhibit the dendrite growth and volume expansion. [10] These strategies render critical progress in understanding Li plating/stripping science and extending cycling life, though it is unsatisfied for practical applications (usually <200 cycles in practical pouch cells). To further enhance the utilization and lifespan of the Li metal anode, it is primarily significant to gain the failure mechanism and electrochemical diagram of the Li metal anode.Recently, considerable efforts have been devoted and many enlightening opinions are released to understand the plating/ stripping behavior and failure mechanism of the Li metal anode. [11] By in situ high-resolution optical images, Wood et al. clearly correlated the cycling voltage and electrode morphology. [12] Xiao and co-workers systematically investigated the nickel cobalt aluminum oxide (NCA)-based LMBs and proposed the accumulation of highly resistive layer composed of "dead" Li was the main reason for the rapid capacity fading instead of the short circuit. [13] Xu and co-workers described the current density for charge (i.e., Li deposition) is identified as a key factor controlling the corrosion of the Li metal anode under high Li capacity utilization. [14] These works update our understanding in a working battery. However, these experiments are conducted at a relatively small current (<3.0 mA cm −2 , 3.0 mA) and low capacity (<4.5 mAh cm −2 , 4.5 mAh) in a coin cell, which are far from the practical conditions in pouch cells. [15] The pouch cell Lithium (Li) metal is regarded as a "Holy Grail" electrode for nextgeneration high-energy-density batteries. However, the electrochemical behavior of the Li anode under a practical working state is poorly understood, leading to a gap in the design strategy and the aim of efficient Li anodes. The electrochemical diagram to reveal failure mechanisms of ultrathin Li in pouch cells is demonstrated. The working mode of the Li metal anode ranging from 1.0 mA cm −2 /1.0 mAh cm −2 (28.0 mA/28.0 mAh) to 10.0 mA cm −2 /10.0 mAh cm −2 (280.0 mA/280.0 mAh) is investigated and divided into three categories: polarization, transition, a...

A Dendrite‐Free Lithium/Carbon Nanotube Hybrid for Lithium‐Metal Batteries

“…However, the bare Li shows a sudden voltage drop at 122 cycles possibly due to an internal short circuit for the Li dendrite penetration. [11] Moreover, the LiCSMF cell still (Figure 3c) with a capacity of 2 mAh cm −2 . These results further indicate that the current density in the cell can be dispersed effectively by the conductive CNTs network in the LiCSMF, the formation of Li dendrites and dead Li in the electrode is significantly inhibited.…”

“…[9] In addition, the irreversible electrolyte consumption by dendritic Li during stripping and the accumulation of insulating solid electrolyte interphase (SEI) layers would result in the undesirable electrolyte exhaustion and increased internal electrical resistance. [10,11] Several strategies have been proved to combat these challenges, such as adding electrolyte additives, [12,13] building stable SEI layer, [14][15][16] adopting solid electrolyte, [17,18] forming artificial interfaces, [19][20][21] or optimizing the metallic electrode structure. [22][23][24] For example, a 3D skeleton can manipulate the distribution of Li, which effectively guides the deposition and avoids the growth of Li dendrites.…”

The Surface Chemistry of Thin Lithium Metal Electrodes in Lithium‐Sulfur Cells

“…In scientific literature, a few attempts have been made employing and analysing thin Li metal foils. [11][12][13] When comparing thick and thin Li metal foils, Jeschull et al [11] and Chen et al [13] discovered more rapid capacity decay for the thin metal foil, which indicated that such a limitation on the Li metal anode induces earlier capacity fade. This was explained by the poor efficiency of the Li metal electrode, which requires a high loading for a well-behaved surface morphology.…”

“…This was explained by the poor efficiency of the Li metal electrode, which requires a high loading for a well-behaved surface morphology. Not specifically in the context of LiÀ S batteries, Shi et al [12] studied the application of a thin Li metal anode (50 μm in thickness) in Li j Li pouch cells, and then discovered that the failure mechanisms were dependent on the applied current density. At low current densities, the proposed failure mechanism was correlated to formation of "dead" Li and SEI layer growth, while for higher current densities sharp dendrites generated shortcircuits.…”

In Situ Growth of Lithiophilic MOF Layer Enabling Dendrite-free Lithium Deposition

“…Li metal with ultrahigh theoretical specific capacity (3,860 mAh g −1 ), ultralow redox potential (−3.04 V versus RHE), and light weight (about 0.53 g cm −3 ) has been considered to be the ultimate candidate anode material for next-generation rechargeable batteries ( Li et al., 2019 ; Shi et al., 2019 ; Guo et al., 2017 ), especially for Li–S and Li–O 2 batteries, without which the advantages of high specific capacities cannot be fully exploited. However, there are some critical issues existing for Li metal anodes that hamper their successful implementation in real batteries.…”