Tough Polymer Electrolyte with an Intrinsically Stabilized Interface with Li Metal for All-Solid-State Lithium-Ion Batteries

Abstract

A high-performance solid polymer electrolyte (SPE) membrane that simultaneously addresses the issues of enhanced toughness and Li-dendrite mitigation for all-solid-state Li-ion batteries (ASSLIBs) is demonstrated. The membrane has a sandwiched structure consisting of a center poly(ethylene oxide)/ lithium bis(trifluoromethanesulfonyl) imide (PEO/LiTFSI) electrolyte matrix laminated on both sides with electrospun high-polarity β-phase poly(vinylidene fluoride-co-hexafluoropropylene) (β-PVDF-HFP) nanofibers. The nanofiber layers impart remarkable enhancement in both mechanical and electrochemical properties of the SPE, including a 20-fold increase in tensile strength and a 48-fold increase in toughness, along with up to 4-fold enhancement in Li-ionic conductivity. Moreover, the highly polar fluorinated nanofiber cladding layers enable a stable Li-plating/ stripping interface on the Li anode to efficiently mitigate dendrite formation, while improving the electrochemical interfacial stability with the cathode. In a Li|SPE|Li symmetric cell, the use of the sandwiched SPE is demonstrated to improve the cycle stability from short-circuiting at 144 h for a pristine PEO/LiTFSI membrane to no short-circuiting even up to 3600 h (1800 Liplating-stripping cycles). In an example of LiFePO 4 |SPE|Li ASSLIBs, using the sandwiched membrane enables substantial reduction irreversible capacity upon charging to the high-voltage end and more than 80% capacity retention for over 1600 h. This work presents a feasible and facile design for an SPE for high-performance ASSLIBs.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications

“…502 A new approach for SPEs development involved the implementation of a PEO/LiTFSI electrolyte matrix laminated on both sides by electrospun poly(VDF-co-HFP) membranes, the main achievement being the absence of short-circuiting up to 3600 h as shown in Figure 33c. 503 Another SPE with the same components but also with N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 13 TFSI) 507 and MWCNT-COOH 508 showed excellent stability against the Li anode and significantly increased Li + migration ability, respectively.…”

Design Strategies for Anodes and Interfaces Toward Practical Solid‐State Li‐Metal Batteries

“…[55] Compared to metal and metal oxide-based interlayers; however, polymers might have a certain disadvantage in terms of Li diffusion kinetics and longterm stability because of their relatively low ionic conductivity and low lithium transference number. [57][58][59] The aforementioned strategies (involving the enhancement of the interfacial Li-wetting properties) for generating conformal contact between solid electrolytes and Li-metal anodes effectively reduce the initial interfacial resistance. This increases the effective area for Li plating/stripping, which improves the Reproduced with permission.…”

Solid Polymer Electrolytes with Dual Anion Synergy and Twofold Reinforcement Effect for All-Solid-State Lithium Batteries

“…17 Electrospinning is a well-established facile method for preparing microscale or nanoscale flexible fibers with tunable porosity, mechanical strength, and functionality into 3D porous structures with a large specific surface. 12,18 Up until now, a large number of electrospun fibers have been utilized as a 3D reinforcement in SPE such as polyimide, 19 polyamide-6, 20 polyacrylonitrile (PAN), 21,22 polyvinylidene fluoride (PVDF), 23 poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), 24 and so forth. Electrospun PAN fibers with excellent thermal stability, robust mechanical strength, and bearing polar nitrile (C�N) groups can assist Li + ion conduction and simultaneously can be used to support a PEO-Li salt-based soft polymer matrix that permeates into the 3D fibrous framework in a manner similar to 3D reinforced concrete structures.…”

“…Various structural modifications have been explored to reduce the crystallinity and increase the ionic conductivity of SPEs, such as blending, grafting, copolymerizing, cross-linking, addition of inorganic or organic fillers, and so forth . Unfortunately, it is well known that the mechanical properties of pristine PEO decrease on the reduction of crystallinity and critically affect the battery performance, leading to short-circuiting due to dendrite penetration . Introducing mechanically stable cross-linked network structure into linear polymer backbones forming semi-interpenetrating networks (semi-IPNs) can effectively reduce the crystallinity of the polymer matrix preserving the dimensional stability and have been used in the past to fabricate SPEs .…”

“…In instances where cross-linking has been known to adversely increase the rigidity and lower the mechanical strength of the electrolyte, porous membranes have been used as support to alleviate the challenges of the cross-linked structures . Electrospinning is a well-established facile method for preparing microscale or nanoscale flexible fibers with tunable porosity, mechanical strength, and functionality into 3D porous structures with a large specific surface. , Up until now, a large number of electrospun fibers have been utilized as a 3D reinforcement in SPE such as polyimide, polyamide-6, polyacrylonitrile (PAN), , polyvinylidene fluoride (PVDF), poly­(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), and so forth. Electrospun PAN fibers with excellent thermal stability, robust mechanical strength, and bearing polar nitrile (CN) groups can assist Li + ion conduction and simultaneously can be used to support a PEO-Li salt-based soft polymer matrix that permeates into the 3D fibrous framework in a manner similar to 3D reinforced concrete structures. − The SPEs thus produced have the porous, strong, fibrous electrospun framework acting as the reinforcement material, with the soft ion-conducting polymer acting as the void-sealer matrix.…”