Self-healing Polymer Electrolytes Research Articles

Interfacial self-healing polymer electrolytes for Long-Cycle silicon anodes in High-Performance solid-state lithium batteries

For all-solid-state lithium-ion batteries (ASSLIBs), silicon (Si) stands out as an appealing anodes material due to its high energy density and improved safety compared to lithium metal. However, the substantial volume changes during cycling result in poor solid-state physical contact and electrolyte–electrode interface issues, leading to unsatisfactory electrochemical performance. In this study, we employed in-situ polymerization to construct an integrated Si anodes/self-healing polymer electrolyte for ASSLIBs. The polymer chain reorganization stems from numerous dynamic bonds in the constructed self-healing dynamic supermolecular elastomer electrolyte (SHDSE) molecular structure. Notably, SHDSE also serves as a Si anodes binder with enhanced adhesive capability. As a result, the well-structured Li|SHDSE|Si-SHDSE cell generates subtle electrolyte–electrode interface contacts at the molecular level, which can offer a continuous and stable Li+ transport pathway, reduce Si particle displacement, and mitigate electrode volume expansion. This further enhances cyclic stability (>500 cycles with 68.1 % capacity retention and >99.8 % Coulombic efficiency). More practically, the 2.0 Ah wave-shaped Si||LiCoO2 soft-pack battery with in-situ cured SHDSE exhibits strongly stabilized electrochemical performance (1.68 Ah after 700 cycles, 86.2 % capacity retention) in spite of a high operating temperatures up to 100 °C and in various bending tests. This represents a groundbreaking report in flexible solid-state soft-pack batteries containing Si anodes.

Interfacial self-healing polymer electrolytes for long-cycle solid-state lithium-sulfur batteries

Coupling high-capacity cathode and Li-anode with solid-state electrolyte has been demonstrated as an effective strategy for increasing the energy densities and safety of rechargeable batteries. However, the limited ion conductivity, the large interfacial resistance, and unconstrained Li-dendrite growth hinder the application of solid-state Li-metal batteries. Here, a poly(ether-urethane)-based solid-state polymer electrolyte with self-healing capability is designed to reduce the interfacial resistance and provides a high-performance solid-state Li-metal battery. With its dynamic covalent disulfide bonds and hydrogen bonds, the proposed solid-state polymer electrolyte exhibits excellent interfacial self-healing ability and maintains good interfacial contact. Full cells are assembled with the two integrated electrodes/electrolytes. As a result, the Li||Li symmetric cells exhibit stable long-term cycling for more than 6000 h, and the solid-state Li-S battery shows a prolonged cycling life of 700 cycles at 0.3 C. The use of ultrasound imaging technology shows that the interfacial contact of the integrated structure is much better than those of traditional laminated structure. This work provides an interesting interfacial dual-integrated strategy for designing high-performance solid-state Li-metal batteries.

Borax cross-linked guar gum hydrogel-based self healing polymer electrolytes filled with ceramic nanofibers towards high-performance green energy storage applications

An inventive concept towards the implementation of green energy-storing devices is the synthesis of hydrogel-based gel electrolytes from biopolymers imbued with self-healing capabilities. However, these electrolytes have drawbacks, such as low mechanical stability due to inadequate cross-linking and limited ionic conductivity compared to synthetic polymers. This work develops and characterizes a flexible self-healing hydrogel polymer electrolytes (HPEs) based on guar gum (GG) hydrogel for use in energy storage devices. Hydrogel is prepared with silicon dioxide (SiO2) nanofibers dispersed into borax-bonding cross-linked guar gum. Propylene carbonate (PC) and diethyl carbonate (DC) in equal amounts and lithium perchlorate (LiClO4) are used as plasticizers and salt, respectively. It has been found that adding nanofibers to the hydrogel and spreading them there considerably increases the ionic conductivity as evaluated by ac impedance spectroscopy. When the nanofiber concentration is 5 wt% (wt%), the hydrogel electrolytes reach their maximum room temperature ionic conductivity of 4.3 × 10−3 S cm−1. XRD, FTIR, SEM, and XPS investigations are used to explain the enhanced conductivity caused by the dispersion of nanofibers. Nanofibers also improve the self-healing abilities of materials, as demonstrated by the fact that hydrogels loaded with 5 wt% nanofibers recover from deformation more quickly than hydrogels with lower nanofiber contents. Additionally, the dispersion of nanofibers enhances the hydrogel's mechanical and thermal properties. According to electrochemical investigations and linear sweep voltammetry (LSV) graphs, hydrogel electrolytes are stable up to 4.7 V. When compared to nanofiber-free hydrogels, nanofiber-integrated hydrogel electrolytes show more excellent interfacial stability. The developed self-healing hydrogel-based polymer electrolytes exhibit outstanding promise for a range of energy storage systems, opening the way for creating high-performance and environmentally friendly energy storage solutions.

Synthesis and Characterization of Vitrimer-like Self-Healing Polymer Electrolytes for Lithium Metal Batteries

Solid-polymer electrolytes have become crucially significant with the fast-expanding energy requirements in both the academic and industrial spheres due to their better safety and energy density compared to liquid electrolytes. Despite these encouraging possibilities, a few obstacles are associated with these electrolytes, chief among them being the limited charge transport via the solid electrode-electrolyte interface. Due to the difference in electrochemical potential between the electrode and the electrolyte, this obstruction initiates electrode-electrolyte interactions through electrode volumetric changes, interface reactions, and space charge layers.One possible way to enhance the LIB performance could be by integrating a new class of covalent adaptable networks called vitrimers.The self-healing, shape memory, recyclability, and reprocessibility properties of vitrimers, a class of covalent adaptable networks (CANs), are derived from a covalent molecular network that can change its topology through molecular rearrangements while maintaining the overall number of network bonds. In this manner, Li dendrites that might develop during battery cycling could be eliminated and the electrolyte-electrode contact could be restored by vitrimers. Figure 1

Rapid self-healing, highly conductive and near-single-ion conducting gel polymer electrolytes based on dynamic boronic ester bonds for high-safety lithium metal batteries

Polymer electrolytes with high ionic conductivity and good self-healing capability are crucial for the development of lithium metal batteries with enhanced rate capability and safety. However, the application of self-healable polymer electrolytes is hindered by low ionic conductivity and slow self-healing speed. Herein, boronic ester based self-healing gel polymer electrolyte (PBAD-PEG) with high ionic conductivity and fast self-healing speed is developed. PBAD-PEG is fabricated by thiol-ene click reaction of a multifunctional monomer 2,2′-(1,4-phenylene)-bis (4-allyloxy-1,3,2-dioxaborolane) (PBAD) consisting of two dynamic boronic ester bonds, pentaerythritol tetra(3-mercaptopropionate) and polyethylene glycol diacrylate. Abundant reversible boronic ester bonds endow PBAD-PEG with good flexibility and excellent self-healing ability. PBAD-PEG can self-heal within 1 h at room temperature after damaged, which effectively restores the ionic conductivities and mechanical properties. PBAD-PEG possesses high ionic conductivity of 8.67 × 10−4 S cm−1 at 25 °C. Lewis acid-base interactions between anions and boron atoms of PBAD-PEG contributes to ultrahigh lithium-ion transference number of 0.71. PBAD-PEG exhibits significant resistance to the growth of Li dendrites. The fabricated LiFePO4/Li batteries with PBAD-PEG achieve significantly boosted cycle stability (capacity retention of 92.6 % after 150 cycles). More importantly, LiFePO4/Li cells with the healed PBAD-PEG also show excellent cycle performance.

Self-healing polymer electrolytes with nitrogen‑boron coordinated boroxine for all-solid-state lithium metal batteries

Polymer networks with dynamic covalent cross-linked boroxine have received a great deal of attention as recyclable and self-healing materials, but their application was rarely mentioned in all-solid-state polymer electrolytes. In this work, the boroxine-based self-healing solid polymer electrolytes (ONBSPE-x) with nitrogen‑boron (NB) coordination were prepared by the amidation reaction between different molecular weight NH2-PEG-NH2 and ortho-triphenylboroxine with the plasticization of lithium salt. To highlight the effect of NB coordination on the self-healing ability of the polymer electrolytes, PNBSPE-2000 with para-triphenylboroxine structure was prepared for comparison. It was proved that the ortho-triphenylboroxine is conducive to the formation of NB coordination and the NB coordination can accelerate the equilibrium of boroxine, further speeding the self-healing ability of ONBSPE-x without external stimulation at room temperature. More importantly, given the strong electron-withdrawing effect of boroxines groups, the ONBSPE-2000 membranes show an ionic conductivity value up to 0.168 mS cm−1 and comparatively high lithium-ion transference number (0.60) at 25 °C, which will minimize concentration polarization between electrolytes and lithium metal anode, then inhibiting lithium dendrite generation. The NB coordination and the interaction between boroxine groups and anions in ONBSPE-2000 were further studied with density functional theory (DFT). The Li|ONBSPE-2000|LiFePO4 coin cell performs excellent cycling stability with an initial discharge capacity of 130.9 mAh g−1 at 0.1C and coulombic efficiency of 94.8 %. Thus, the self-healing solid polymer electrolytes with nitrogen‑boron coordinated boroxine provide a prospective application for high-performance lithium metal batteries.

Synergistic effect and enhanced safety of double dynamic solid polymer electrolytes for lithium metal batteries

A solid polymer electrolyte with low mechanical strength and poor flexibility will cause mechanical degradation, short circuits, or functional failures in lithium ion batteries (LIBs). Therefore, introducing an double dynamic solid polymer electrolytes with high ionic conductivity, good mechanical strength, and excellent self-healing ability for stabilizing the solid electrolyte interface, preventing battery fire, and suppressing Li dendrite growth will further improve the reliability, security, and lifetime of the LIBs. Herein, a series of dual dynamic self-healing solid polymer electrolytes (DD-shSPEs) are developed via the Schiff base reaction between different molar ratios of polyethylene glycol derivative (tat-PEG) and terephthalaldehyde. The hydrogen bond and the highly reversible imine bonds endow DD-shSPEs with rapid self-repairing capacity to cure mechanical damage within 5 min at normal temperature. The self-healing polymer electrolytes also exhibit excellent stretchability, which can satisfy the external deformation of the battery. Meanwhile, after self-healing, the ionic conductivities of the electrolytes can hold the original values. Also, the initial discharge capacity (IDC) of the battery based on DD-shSPEs reach to 149.3 mAh g-1 under a current rate of 0.1 C, and still maintains 144.2 mAh g−1 after 100 cycles. Besides, the polymer electrolyte (PE) also exhibits good interfacial stability and have a cycle life of more than 650 h at a current density of 0.2 mA cm-2. Accordingly, this work shows that the high-performance PE based on self-healing materials is promising for constructing high stable solid-state energy storage device.

Self-healing polymer electrolytes with dynamic-covalent borate for solid-state lithium metal batteries

Developing a solid polymer electrolyte (SPE) combining superior interface stability with high ionic conductivity is still a challenge in the energy storage field. Herein, a series of novel self-healing solid polymer electrolytes were prepared by free radical photopolymerization with poly(ethylene glycol) methyl ether methacrylate and monomers containing borate. The reversible reaction induced by interesterification of borate ester endows the polymer electrolytes with excellent self-healing ability. The comb-like structure based on flexible poly(ethylene glycol) provides an amorphous state, which is conducive to lithium-ion transport. Further benefiting from the strong interaction between electron capture groups and anions of electrolyte salts, the borate-containing comb-shaped solid polymer electrolytes (PPBSPE) films display optimal ionic conductivity of 0.272 mS cm−1 at 60 °C, satisfactory transfer number for lithium ion, wide working voltage window, and remarkable stability towards lithium metal. The initial discharge capacities of the cell based on PPBSPE reach 156.2 mAh g−1 at a current rate of 0.1C, and high Coulombic efficiency (CE) of 99.4 %. This enhancement is due to the introduction of borate to the comb-shaped polymer, which is beneficial to form a more suitable electrolyte that can stabilize and improve the performance of lithium metal batteries.

Artificial synapses based on organic electrochemical transistors with self-healing dielectric layers

Organic electrochemical transistors (OECTs) have emerged as one type of promising building block for neuromorphic systems owing to their capability of mimicking the morphology and functions of biological neurons and synapses. Currently, numerous kinds of OECTs have been developed, while self-healing performance has been neglected in most reported OECTs. In this work, the OECTs using self-healing polymer electrolytes as dielectric layers are proposed. Several important synaptic behaviors are simulated in the OECTs by doping the channel layers with ions from the electrolytes. Benefitting from the dynamic hydrogen bonds in the self-healing polymer electrolytes, the OECTs can successfully maintain their electrical performance and the ability of emulating synaptic behaviors after self-healing compared with the initial state. More significantly, the sublinear spatial summation function is demonstrated in the OECTs and their potential in flexible electronics is also validated. These results suggest that our devices are expected to be a vital component in the development of future wearable and bioimplantable neuromorphic systems.

Suppression of Dendrites by a Self-Healing Elastic Interface in a Sodium Metal Battery

The safety issues caused by sodium dendrites limit the widespread application of sodium metal batteries. Herein, a self-healing polymer electrolyte (SPE) is prepared by immersing the self-healing polymer in a liquid electrolyte. Benefiting from the self-healing properties, elastic interface, and dense nonporous structure of the SPE, the fabricated NaK|MC SPE|NaK symmetric battery presents a long battery life (∼590 h) and low polarization voltage (192 mV). Moreover, the PTCDA|MC SPE|NaK full cell also delivers stable long cycles and outstanding rate performance.

Self-Healing Polymer Electrolytes for Next-Generation Lithium Batteries

The integration of polymer materials with self-healing features into advanced lithium batteries is a promising and attractive approach to mitigate degradation and, thus, improve the performance and reliability of batteries. Polymeric materials with an ability to autonomously repair themselves after damage may compensate for the mechanical rupture of an electrolyte, prevent the cracking and pulverization of electrodes or stabilize a solid electrolyte interface (SEI), thus prolonging the cycling lifetime of a battery while simultaneously tackling financial and safety issues. This paper comprehensively reviews various categories of self-healing polymer materials for application as electrolytes and adaptive coatings for electrodes in lithium-ion (LIBs) and lithium metal batteries (LMBs). We discuss the opportunities and current challenges in the development of self-healable polymeric materials for lithium batteries in terms of their synthesis, characterization and underlying self-healing mechanism, as well as performance, validation and optimization.

Effect of SiO2 microstructure on ionic transport behavior of self-healing composite electrolytes for sodium metal batteries

Batteries matched with flexible intelligent electronic devices are required in the future to supply dense and reliable power security. In addition to energy storage performance, functionalized design of batteries with good mechanical properties and self-healing ability is critical to the development of flexible intelligent electronic devices. The polymer with quadruple hydrogen bonds can give materials the ability to repair mechanical damage and restore the original mechanical properties. The incorporation of inorganic fillers into polymer electrolytes can improve the electrochemical properties and stability of the electrolytes. Optimization of the geometry of inorganic materials could further improve the electrical conductivity of composite electrolytes. In this work, a flexible self-healing polymer electrolyte (Poly (ethylene glycol)-co-ureidopyrimidinone), PEG-UPy) was synthesized. Three different microstructures of SiO2 fillers (solid, mesoporous, and hollow mesoporous) with UPy modified were designed to improve the sodium ion transport performance of the PEG-UPy self-healing polymer electrolyte for sodium ion batteries. The PEG-UPy electrolyte filled with hollow mesoporous SiO2 (PEG-UPy@hSiO2) exhibits an excellent electrochemical performance due to its unique structure among the samples. The PEG-UPy@hSiO2 electrolyte shows the highest ionic conductivity, sodium ion transference number, and appropriate self-healing property. The discharge capacity of NVP/PEG-UPy@hSiO2-NaTFSI (HCPE)/Na cell could reach 110.5 mAh g−1 at 0.1C and the capacity retention rate could reach more than 77.6% after 200 cycles at 60 °C.

Highly conductive self-healing polymer electrolytes based on synergetic dynamic bonds for highly safe lithium metal batteries

Self-healing polymer electrolytes can improve the safety, reliability and cycle life of the batteries. Herein,we developed a self-healing polymer electrolyte (IBshPE) with high ionic conductivity and excellent self-healing property. IBshPE cross-linked by synergetic dynamic imine bond and boroxine bond was prepared via the reaction of 2-formylphenylboronic acid and poly(ethylene glycol) diamine. In IBshPE, boroxine bonds with B-N coordination and imine bonds can synchronously undergo fast bond exchange reactions, enabling rapid self-healing of IBshPE. IBshPE shows high self-healing efficiency of 97% within 4 h. The healed IBshPE has nearly the same mechanical property and ionic conductivity as the original IBshPE. IBshPE exhibits the highest ionic conductivity (5.08 × 10−3 S cm−1 at 30 °C) among the reported self-healing polymer electrolytes. IBshPE facilitates the construction of robust LiF-rich SEI and efficiently inhibits dendrite growth. LiFePO4/Li cells with IBshPE exhibits excellent cycle performance (capacity retention of 98.6% after 80 cycles) and good rate capability (specific capacity of 130.5 mAh g−1 at 2C rate). More importantly, IBshPE is capable of self-repairing damage in the LiFePO4/Li cells and restoring the performance of the cells, thus effectively enhancing the reliability and safety of the battery.

Self‐Healing Polymer Electrolyte for Dendrite‐Free Li Metal Batteries with Ultra‐High‐Voltage Ni‐Rich Layered Cathodes

Practical applications of polymer electrolytes in lithium (Li) metal batteries with high-voltage Ni-rich cathodes have been hindered by the dendrite growth and poor oxidative stability of electrolytes. Herein, a self-healing polymer electrolyte is developed by in situ copolymerization of 2-(3-(6-methyl4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (UPyMA) and ethylene glycol methyl ether acrylate (EGMEA) monomers. With the electrolyte, the dendrite growth is inhibited by spontaneously repairing dendrite-induced defects, cracks, and voids at the Li/electrolyte interface; the suppressed dendrite growth and associated electro-chemo behaviors are visualized by the kinetic Mont-Carlo simulation. Benefitting from the high ionic conductivity, wide electrochemical window and good interfacial stability, the self-healing polymer electrolyte enables stable cycling of the LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathode under 4.7V, achieving a high specific capacity of ≈228.8mAh g-1 and capacity retention of 80.4% over 500 cycles. The new electrolyte is very promising for developing highly safe and dendrite-free Li metal batteries with high energy density.

Self-healing polymer electrolyte for long-life and recyclable lithium-metal batteries

Nowadays, the complex application environment requires lithium batteries to be self-healing to cope with the inevitable volume changes and breakage during use. However, only a small part of self-healing materials has been applied in lithium batteries because the introduction of self-healing components will affect the electrochemical performance. Developing a self-healing and recyclable electrolyte to pursue sustainable and long-life lithium batteries is still a great challenge. Herein, a self-healing and recyclable electrolyte has been prepared with a rigid and flexible epoxy resin as a backbone and disulfide bonds as reversible cross-linking points. The epoxy resin imparts superior mechanical abilities (tensile strength >20 MPa) to the electrolytes, while the disulfide bonds provide excellent self-healing capabilities (healing efficiency >95%). Meanwhile, the ionic conductivity (25 °C) of the rigid-flexible self-healing polymer electrolytes (RFSPEs) is as high as 10−3 S/cm, and the multiple healed RFSPE has no changes in the ionic conductivity. In addition, RFSPE has an inhibitory effect on the growth of lithium dendrites, which can cycle stably for up to 1800 h at 1 mAh/cm2. The Li/LiFePO4 cell also exhibits good cycling stability and superior rate performance.

Structure and Dynamics in Self-Healing Polymer Electrolytes Based on PVDF-HFP for Battery Applications

Lithium dendrite formation is a key limitation in rechargeable Li metal batteries. Here we report on a novel polymer electrolyte with self-healing capabilities, consisting of PVdF-HFP membranes imbibed with an ionic liquid electrolyte EMIM-TFSI + LiTFSI and mechanically reinforced by alumina nanowires. Similar membranes were reported to have self-healing capability via resistance to dendrite formation at the electrode-electrolyte interface.1 We have investigated the structure and dynamics in these membranes by nuclear magnetic resonance (NMR). Double resonance and 2D NMR methods show that the EMIM cation interacts with CF3 group present in HFP, forming an ion-dipole association which may be related to the desired self-healing properties. Moreover, addition of alumina nanowires has been reported2 to increase the ionic conductivity in the membrane in addition to imparting mechanical strength. We have used pulsed field gradient (PFG) NMR to investigate how alumina nanowire doping into the PVDF-HFP-IL matrix improves the Li+ diffusivity. Additional characterizations such as electron dispersion X-ray (EDX) spectroscopy to study nanowire distribution in the polymer and ionic conductivity measurements, will also be discussed. Keywords: Ionic Liquids, Self-healing, Dendrite formation, PVDF-HFP membranes, NMR spectroscopy, EDX References Chen, T. et al. Ionic liquid-immobilized polymer gel electrolyte with self-healing capability, high ionic conductivity and heat resistance for dendrite-free lithium metal batteries. Nano Energy 54, 17–25 (2018).Kwon, S. J. et al. Influence of Al2O3 Nanowires on Ion Transport in Nanocomposite Solid Polymer Electrolytes. Macromolecules 51, 10194–10201 (2018).

A high ion-conducting, self-healing and nonflammable polymer electrolyte with dynamic imine bonds for dendrite-free lithium metal batteries

High-performance polymer electrolytes with the capability to self-heal mechanical damage can effectively enhance reliability, safety and service life of the batteries. Herein, a novel polymer electrolyte (PBPE) with excellent self-healing capacity and high ionic conductivity was developed. PBPE with polymer networks cross-linked by highly reversible imine bonds was fabricated by the Schiff-base reaction between poly(ethylene glycol) diamine and benzene-1,3,5-tricarbaldehyde. PBPE can quickly repair the cut damage spontaneously within 1 h at room temperature and recover its mechanical strength and electrochemical properties. The healed PBPE exhibits almost the same ionic conductivities and mechanical properties as the original PBPE shows. PBPE possesses the highest ionic conductivity (4.79 × 10−3 S cm−1 at 30 °C) among the self-healing polymer electrolytes. PBPE can promote the generation of LiF-rich SEI and effectively suppress dendrite growth on Li metal anodes. LiFePO4 (LFP) cells assembled with PBPE exhibit excellent rate capability (discharge capacity of 118.2 mAh g−1 at 5 C rate) and good cycling performance (capacity retention of 97.8% over 125 cycles). More importantly, the healed PBPE can completely recover its properties from damage in LFP cells and enable the cells to possess cycle performance identical to original PBPE.

Self-Healing Commodity Polymer Electrolytes for Reliable Li Metal Batteries

As countries worldwide pledge to decarbonize their economy, the global demand for batteries is rapidly increasing, urging the development of high-specific-energy (> 500 Wh/kg at cell level) and low-cost (< 100$/kWh at pack level) batteries.1 The safety and durability of these devices are of primary importance. Polymer electrolytes are safer than traditional liquid electrolytes, and further benefit from highly tunable structures.2 Thus, polymers can be designed to achieve desired properties, including the ability of self-healing from damages, which can greatly extend battery lifetime. While the synthesis of self-healing polymers often requires specifically designed monomers or other polymerization components, it was recently shown that commodity copolymers, based on methyl methacrylate (MMA) and n-butyl acrylate (nBA) or their derivatives, display self-healing behavior.3 The autonomous self-repair of these copolymers with certain compositions is governed by interchain van der Waals forces.Herein, this finding was exploited to prepare self-healing polymer electrolytes that ensured long-term performance of high-energy Li metal batteries. The electrolytes were based on polyethylene oxide (PEO), P(MMA-co-nBA) copolymers and Li bis(trifluoromethanesulfonyl)imide (TFSI) salt. Various structures and compositions were explored, including polymer blends and block copolymers made by atom transfer radical polymerization (ATRP) using a functionalized PEO-macroinitiator (Figure 1). The effect of polymer morphology, architecture, weight fraction of PEO and LiTFSI on electrolyte conductivity, thermal and electrochemical stability, Li transference number, mechanical strength and self-healing ability was analyzed.By recovering ionic conductivity and mechanical strength upon cracks, self-healing electrolytes can suppress the growth of dendrites that hinders the utilization of Li metal anodes.4 Moreover, the viscoelastic nature of these polymers contribute to the creation of conformal interfaces on Li metal.2 Therefore, the optimized commodity self-healing polymer electrolytes were tested in Li metal batteries, demonstrating the ability of the electrolytes to enable long-term stable cycling. In addition, tests were conducted to prove the self-repair of the electrolyte upon damaging the device.

Light-Switchable and Self-Healable Polymer Electrolytes Based on Dynamic Diarylethene and Metal-Ion Coordination.

Self-healing polymer electrolytes are reported with light-switchable conductivity based on dynamic N-donor ligand-containing diarylethene (DAE) and multivalent Ni2+ metal-ion coordination. Specifically, a polystyrene polymer grafted with poly(ethylene glycol-r-DAE)acrylate copolymer side chains was effectively cross-linked with nickel(II) bis(trifluoromethanesulfonimide) (Ni(TFSI)2) salts to form a dynamic network capable of self-healing with fast exchange kinetics under mild conditions. Furthermore, as a photoswitching compound, the DAE undergoes a reversible structural and electronic rearrangement that changes the binding strength of the DAE-Ni2+ complex under irradiation. This can be observed in the DAE-containing polymer electrolyte where irradiation with UV light triggers an increase in the resistance of solid films, which can be recovered with subsequent visible light irradiation. The increase in resistance under UV light irradiation indicates a decrease in ion mobility after photoswitching, which is consistent with the stronger binding strength of ring-closed DAE isomers with Ni2+. 1H-15N heteronuclear multiple-bond correlation nuclear magnetic resonance (HMBC NMR) spectroscopy, continuous wave electron paramagnetic resonance (cw EPR) spectroscopy, and density functional theory (DFT) calculations confirm the increase in binding strength between ring-closed DAE with metals. Rheological and in situ ion conductivity measurements show that these polymer electrolytes efficiently heal to recover their mechanical properties and ion conductivity after damage, illustrating potential applications in smart electronics.

Deep-Eutectic-Solvent-Based Self-Healing Polymer Electrolyte for Safe and Long-Life Lithium-Metal Batteries.

The deployment of high-energy-density lithium-metal batteries has been greatly impeded by Li dendrite growth and safety concerns originating from flammable liquid electrolytes. Herein, we report a stable quasi-solid-state Li metal battery with a deep eutectic solvent (DES)-based self-healing polymer (DSP) electrolyte. This electrolyte was fabricated in a facile manner by in situ copolymerization of 2-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (UPyMA) and pentaerythritol tetraacrylate (PETEA) monomers in a DES-based electrolyte containing fluoroethylene carbonate (FEC) as an additive. The well-designed DSP electrolyte simultaneously possesses non-flammability, high ionic conductivity and electrochemical stability, and dendrite-free Li plating. When applied in Li metal batteries with a LiMn2 O4 cathode, the DSP electrolyte effectively suppressed manganese dissolution from the cathode and enabled high-capacity and a long lifespan at room and elevated temperatures.