Thermally Stable and Dendrite‐Resistant Separators toward Highly Robust Lithium Metal Batteries

Abstract

Metallic lithium (Li) has been considered as an attractive anode material for next-generation rechargeable batteries, owing to its high theoretical capacity (3860 mAh g -1 ), low redox potential (−3.040 V vs standard hydrogen electrode), and low density (0.59 g cm -3 ). [4][5] Nevertheless, the high activity of Li metal, nonuniform Li plating, large volume change, and the formation of fragile solid electrolyte interphase (SEI) layer in lithium metal batteries (LMBs) inevitably lead to negative effects of the low Coulombic efficiency (CE), the uncontrollable growth of Li dendrite, the formation of "dead" Li, etc. [6][7][8][9] These intractable problems can cause irreversible loss of Li metal and electrolyte, resulting in a sustaining capacity attenuation or even triggering thermal runaway and explosion of the battery. Thermal runaway-induced accidents should be a wakeup call that people need to focus more attention on the battery safety and avoid undesirable energy release during battery cycling, since the batteries with higher energy density always endure lower thermal stability during operation. [10][11][12] Consequently, it is of vital importance to achieve robust LMBs security in the progress of developing Li metal anode and constantly breaking the bottleneck of energy density.As a critical component in batteries, separator not only provides paths for Li ion transfer, but also prevents accidental contact of anode and cathode. [13] According to statistics, at least 90% of various battery abuses (e.g., mechanical-abuse, electrical-abuse, thermal-abuse, and electrochemical-abuse) are related to internal short circuits caused by the failure of separator. [14] The prominent weak point of conventional polyolefin separators is their low melting point (135 °C for polyethylene (PE) separator and 165 °C for polypropylene (PP) separator), [15] which means they can easily shrink and collapse upon thermalabuse. To address this issue, tremendous efforts have been devoted to designing thermal-safety separators. [16] Metal oxides with polar surfaces (e.g., SiO 2 and Al 2 O 3 ) have been commonly reported as protective layers to enhance the thermal resistance of polyolefin separator. [17] Some inorganic materials with high Li-ion, thermal conductivity or flame retardance (e.g.,

Integration Plasma Strategy Controlled Interfacial Chemistry Regulation Enabling Planar Lithium Growth in Solid‐State Lithium Metal Batteries

“…The discharge capacities of Ag-LAGP initially increase within 10 cycles since the formation of a disparate functional layer (Ag-Li alloy) accelerates the Li + transfer and stabilizes the interface on Li anode side. [40] However, the high electronic conductivity of Ag-Li alloy also easily triggers the side reactions between the SSEs and Li metal, going against to the cycling stability of batteries. [26] IP-LAGP also delivers a decent rate performance in Li | NCM811 SSLMBs as shown in Figure 3f.…”

Negatively charged separators facilitating lithium-ion conduction to stabilize lithium metal anodes

“…It is known that fluorine (F) is the most electronegative element, being able to form the strongest C–F covalent bond (488 kJ mol −1 ). 27 Polyvinylidene fluoride (PVDF) molecular chains are rich in negatively charged F atoms, which can immobilize anions and facilitate the conduction of lithium ions. Based on the PVDF polymer, we prepare negatively charged separators (NCSs) with different thicknesses by the nonsolvent-induced phase separation (NIPS) method.…”

Nanodiamond-Enhanced Nanofiber Separators for High-Energy Lithium-Ion Batteries

“…Separators, an inactive component in batteries, do not directly participate in redox events but physically separate battery anode and cathode, prevent short circuits, and serve as reservoirs of liquid electrolytes and as conduits for Li-ion transport between the electrodes . In general, separators play a pronounced role in determining battery rate capability, lifespan, and perhaps most importantly, safety. − …”