Interfacial Engineering of Binder‐Free Janus Separator with Ultra‐Thin Multifunctional Layer for Simultaneous Enhancement of Both Metallic Li Anode and Sulfur Cathode

Abstract

and the undesired soluble LiPSs migrate through the porous commercial separators to the metallic Li anode, causing corrosion and passivation. [8] In terms of the metallic Li anode, the Li-dendrite growth triggered by the nonuniform Li dissolution/deposition will induce an internal short circuit. [9] To counteract these negative consequences, researchers have developed hosts for sulfur encapsulation in cathode, [10][11][12][13] lithium anode protection, [14] and separator modification to prevent lithium polysulfides (LiPSs) from shuttling. [15][16][17] Proposing a rational design strategy for simultaneous enhancement of both metallic Li anode and sulfur cathode is of great significance. The separator, one of the most indispensable components, contacts both the cathode and anode directly. It is considered to be a facile and effective approach to functionalizing separators to confine LiPSs and synchronously regulate the Li dissolution/deposition in LSBs. [18][19][20] The commercial polyolefin separator with a low melting point and nonpolar characteristics results in poor electrolyte affinity and difficulty in modification. [21,22] In addition, most of the functionalization strategies have not paid attention to the thickness and weight, which would apparently reduce the energy density of LSBs.What's worse, the stripping of the coated layer from the separator extensively exists in traditional separator modification methods, which would significantly diminish practical performance and even raise serious safety concerns about Li-metal batteries. [23,24] Especially for high energy-density batteries used in electric vehicles (Tesla, 4680), a large amount of binder (polyvinylidene fluoride; PVDF) would be coated on the separator to improve cycle stability, preventing the powder from falling off during cycling, but this is still ineffective. [25,26] Magnetron sputtering, an effective approach for fiber functionalization, could be a solution to the aforementioned issues. [27] During the sputtering process, the functional target material would deposit on the substrate in the form of atoms or molecules, enhancing the adhesion to overcome stripping defects.Meanwhile, research has demonstrated that electrospun nanofibrous separators with high porosity and polar groups were easily modified to improve the electrolyte affinity and suppress the shuttle effect of LiPSs. [28,29] Polyacrylonitrile (PAN) Exploring a scalable strategy to fabricate a multifunctional separator is of great significance to overcome the challenges of lithium polysulfides (LiPSs) and dendritic growth in lithium-sulfur batteries (LSBs). Herein, a binder-free Janus separator is constructed by interfacial engineering. At the cathode interface, an ultra-thin covalent triazine piperazine film containing tailorable micropores and adsorption sites is decorated on polyacrylonitrile (PAN) membrane by in situ interfacial polymerization, building a triple barrier for LiPSs. The combination of steric hindrance and chemical adsorption reduces LiPS's migration by 81.85%. Me...

Donor–Acceptor Conjugated Microporous Polymer toward Enhanced Redox Kinetics in Lithium–Sulfur Batteries

“…The N 1s spectrum of pure CMP-B exhibits two peaks at 399.0 and 400.2 eV, corresponding to C–NC, and C–N–H, respectively (Figure b). In comparison, a positive shift of these peaks can be observed in CMP-B after Li 2 S 6 adsorption, confirming the charge transfer from N in triazine and secondary amine to Li + . Moreover, a new peak appears at a high binding energy of 402.1 eV, which can be ascribed to the Li–N bond.…”

“…In comparison, a positive shift of these peaks can be observed in CMP-B after Li 2 S 6 adsorption, confirming the charge transfer from N in triazine and secondary amine to Li + . 48 Moreover, a new peak appears at a high binding energy of 402.1 eV, which can be ascribed to the Li−N bond. Similar results observed in N 1s spectrum of CMP-T revealed again that Li−N bonds play a vital role in strengthening the interaction between CMP and polysulfides and thus effectively inhibiting the shuttle effect (Figure 4c).…”

Recent Development in Novel Lithium-Sulfur Nanofiber Separators: A Review of the Latest Fabrication and Performance Optimizations

“…Metal oxides in the Li anode-facing side can also improve LSB longevity by decreasing Li dendrite formation. Wu et al [ 126 ] coated the anode side of a PAN NF separator with Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) via magnetron sputtering. The higher surface area of the NFs and polarity of LLZTO increased electrolyte affinity.…”

“…Similarly, covalent organic frameworks (COFs) have been investigated as modifiers for various LSB components because of their tunable porosity, strong interaction with LiPS, and various functional groups [ 150 ]. However, we are only aware of one study by Wu et al who modified a PAN NF separator with covalent triazine piperazine [ 126 ]. Other promising materials like catalytic chalcogenides [ 151 ], layered double hydroxides [ 152 ], quantum dots [ 153 ], and metal borides [ 154 ] have yet to be investigated as modifiers for NF separators.…”

Fast Ion Conduction Nanofiber Matrix Composite Electrolyte for Dendrite‐Free Solid‐State Sodium‐Ion Batteries with Wide Temperature Operation

“…[28][29][30] Moreover, low-cost electrolytes are essential for SIBs to meet the demands of a large-scale application of energy storage. Scalable electrospinning technology has been developed for fabricating nanofibrous separators in our previous work, [31] which provides the technical support for large-scale ceramic nanofibrous membrane incorporation into polymer electrolytes to achieve thermostability, which is promising for use in the military or medical field. [32] In addition, sodium dendrite is also a challenge, restricting the practical application of SIBs.…”