Interface Engineering of MXene Composite Separator for High‐Performance Li–Se and Na–Se Batteries

Abstract

However, the development of metal-Se batteries has been blocked by the severe shuttle effect of polyselenides, particularly in ether-based electrolyte, where the polyselenides diffuse across the separator and react with the metal anode. [12,13] Tremendous efforts have been devoted to the design of advanced cathode host materials to mitigate the shuttle effect. [14,15] These designed cathode strategies include: employing porous carbon materials as the hosts; [7,[16][17][18][19] coating the cathode materials with graphene, metal oxide, or conductive polymers; [20][21][22][23][24] and heteroatoms doping. [25][26][27] However, these cathode engineering would inevitably reduce the mass ratio of selenium by introducing additional components, leading to decreased energy density. [28] Recently, functional separators have been prepared to inhibit the shuttle effect in Se-or S-based batteries. [17,[29][30][31][32][33][34] For example, MXenes (M n+1 X n T x , where M = transition metal, X = carbon/nitrogen, n = 1, 2, and 3, and T x represents surface functional groups) modified separators have been proved to be effective in suppressing the shuttle effect due to their anisotropic shape and large 2D dimensions that increases the diffusion pathway of polysulfide/polyselenide species. [35][36][37] In addition, MXene shows strong adsorption to polysulfides due to the Lewis acid-base interaction between polysulfides and Ti sites, [38,39] which may also work for polyselenides. Nazar and co-workers have shown that the surface environment on MXene enhances such Lewis acid-base chemisorption via thiosulfate formation. [38] However, this enhanced adsorption undergoes a two-step process with sluggish kinetics. Although the shuttle effect can be mitigated, the battery showed slow redox reaction, especially under high current densities. In addition, the MXene nanosheets also suffer from restacking and poor electrolyte affinities due to the van der Waals (vdW) forces and rich hydrophilic surface groups (OH and F), respectively. [40,41] It is well known that the hydrophilic groups on MXene have low compatibility to organic electrolyte. [42] The inferior separator-electrolyte contact will lead to a poor solid-electrolyte interface (SEI) and slow electrolyte infiltration process. [43] Herein, we developed a novel self-assembled cetrimonium bromide (CTAB)/carbon nanotube (CNT)/Ti 3 C 2 T x MXene Selenium (Se), due to its high electronic conductivity and high energy density, has recently attracted considerable interest as a cathode material for rechargeable Li/Na batteries. However, the poor cycling stability originating from the severe shuttle effect of polyselenides hinders their practical applications. Herein, highly stable Li/Na-Se batteries are developed using ultrathin (≈270 nm, loading of 0.09 mg cm −2 ) cetrimonium bromide (CTAB)/carbon nanotube (CNT)/Ti 3 C 2 T x MXene hybrid modified polypropylene (PP) (CCNT/ MXene/PP) separators. The hybrid separator can immobilize the polyselenides via enhanced Lewis acid-base interactions betwee...

State‐Of‐The‐Art and Future Challenges in High Energy Lithium–Selenium Batteries

“…In addition to COFs, the emerging MXenes (Ti 3 C 2 T x ) was also evaluated to functionalize the separator recently in consideration of their desirable 2D laminar structure with strong affinities to intermediates. [ 216 ] A self‐assembled coating layer comprising CTAB, CNTs, and MXenes was designed to intercept polyselenides shuttling (Figure 16c). DFT calculations and permeability tests suggested the effective polyselenides adsorption by CTAB/MXenes through Lewis acid–base interactions (Figure 16d–f).…”

Advances in MXene Films: Synthesis, Assembly, and Applications

“…However, given the increased number of published papers, MXene is still generally assembled into films. For example, MXene films can be applied as flexible electrodes [42,66], membrane separation (including liquid separation membranes and gas separation membranes) [67,68], battery separators [69], and molecular sieves [70]. The unique chemical compositions, crystallization structure, and morphology of MXenes have been studied for their potential functionalities.…”

Rechargeable Potassium–Selenium Batteries

“…For example, in the Wang's study of Ti 3 C 2 T x MXene for Na-Se batteries, the Lewis acid-base interactions between MXene and sodium polyselenides were able to immobilize soluble intermediates and enhance reaction kinetics. [87] So far, there have not been any unusually adsorptive materials reported for K-Se batteries. This area is hence an open research opportunity for further development of K-Se batteries.…”

“…For example, in the Wang's study of Ti 3 C 2 T x MXene for Na–Se batteries, the Lewis acid‐base interactions between MXene and sodium polyselenides were able to immobilize soluble intermediates and enhance reaction kinetics. [ 87 ]…”