Solid Polymer Electrolyte Research Articles

Two in one: The use of hexagonal copper sulfide (CuS) nanoparticles as a bifunctional high-performance cathode and as a reinforced electrolyte additive for an all-solid-state lithium battery

All Solid-State Batteries (ASSBs) based on solid polymer electrolytes (SPEs) have improved safety, energy, and power densities than conventional liquid electrolyte-based Lithium-ion batteries (LIBs). However, two significant obstacles still need to be addressed, including the low ionic conductivities and the low interfacial contact between ASSB components. This study involves the fabrication of hexagonal CuS nanoparticles by a one-step hydrothermal method and uses them for both cathode and solid electrolyte formulation functions. The reasonable ionic conductivity of 4.68 × 10−4 S.cm−1 at 60℃ and the instant transport number of 0.86 of the designed CuS filler-incorporated solid electrolyte offered great promise for ASSBs applications. In particular, the CuS filler-incorporated solid electrolyte exhibited ceaseless and prompt Li-ion transportation kinetics and delivered a dendrite resistance capability over 200 cycles of stripping/plating of Li. In addition, the Li metal solid-state battery is also verified using CuS as the cathode and SPE electrolyte (PEO/LiTFSI/CuS SPE) system. It offers an initial discharge capacity of up to 695 mAh/g and keeps an average capacity of ∼ 365 mAh/g after 50 cycles at a current density of 0.5C. Thus, this study introduced a simple but effective solution to mitigate the dendrite problems associated with solid polymer electrolytes by using CuS as a durable inactive filler.

Confining Polymer Electrolyte in MOF for Safe and High‐Performance All‐Solid‐State Sodium Metal Batteries

AbstractNanoconfined polymer molecules exhibit profound transformations in their properties and behaviors. Here, we present the synthesis of a polymer‐in‐MOF single ion conducting solid polymer electrolyte, where polymer segments are partially confined within nanopores ZIF‐8 particles through Lewis acid‐base interactions for solid‐state sodium‐metal batteries (SSMBs). The unique nanoconfinement effectively weakens Na ion coordination with the anions, facilitating the Na ion dissociation from salt. Simultaneously, the well‐defined nanopores within ZIF‐8 particles provide oriented and ordered migration channels for Na migration. As a result, this pioneering design allows the solid polymer electrolyte to achieve a Na ion transference number of 0.87, Na ion conductivity of 4.01×10−4 S cm−1, and an extended electrochemical voltage window up to 4.89 V vs. Na/Na+. The assembled SSMBs (with Na3V2(PO4)3 as the cathode) exhibit dendrite‐free Na‐metal deposition, promising rate capability, and stable cycling performance with 96 % capacity retention over 300 cycles. This innovative polymer‐in‐MOF design offers a compelling strategy for advancing high‐performance and safe solid‐state metal battery technologies.

Sandwich-type composited solid polymer electrolytes to strengthen the interfacial ionic transportation and bulk conductivity for all-solid-state lithium batteries from room temperature to 120 °C

The insurmountable charge transfer impedance at the Li metal/ solid polymer electrolytes (SPEs) interface at room temperature as well as the ascending risk of short circuits at the operating temperature higher than the melting point, dominantly limits their applications in solid-state batteries (SSBs). Although the inorganic filler such as CeO2 nanoparticle content of composite solid polymer electrolytes (CSPEs) can significantly reduce the enormous charge transfer impedance at the Li metal/SPEs interface, we found that the required content of CeO2 nanoparticles in SPEs varies for achieving a decent interfacial charge transfer impedance and the bulk ionic conductivity in CSPEs. In this regard, a sandwich-type composited solid polymer electrolyte with a 10% CeO2 CSPEs interlayer sandwiched between two 50% CeO2 CSPEs thin layers (sandwiched CSPEs) is constructed to simultaneously achieve low charge transfer impedance and superior ionic conductivity at 30 °C. The sandwiched CSPEs allow for stable cycling of Li plating and stripping for 1000 h with 129 mV polarized voltage at 0.1 mA cm−2 and 30 °C. In addition, the LiFePO4/Sandwiched CSPEs /Li cell also exhibits exceptional cycle performance at 30 °C and even elevated 120 °C without short circuits. Constructing multi-layered CSPEs with optimized contents of the inorganic fillers can be an efficient method for developing all solid-state PEO-based batteries with high performance at a wide range of temperatures.

Stabilization versus Penetration Dynamics Induced by Localized Concentration Polarization in Solid Polymer Electrolytes

While the onset of dendrites found inside solid polymer electrolytes was typically analyzed by the dilute solution theory, nonideal behaviors such as dendrites at underlimiting current densities were often reported. Here, we consider two critical factors that were often neglected in existing studies, the severe heterogeneous current distribution and the dynamic change of modulus during the polarization process. Polymers with different dynamic mechanical properties were assessed, exploiting the recently discovered mechanism of phase transformation inside low-salt-concentration polymers. Analyses of the operando images revealed two characteristic points on the potential curve, the local and total concentration depletion which each corresponded to the starting and stopping point of dendrites. We further assess these dynamics at different degrees of heterogeneity controlled by different electrode sizes. The penetration dynamics and Sand’s time scaling exponent were heavily affected by both the initial concentration and the electrode size, which stress the significance of interfacial dynamic heterogeneity in working batteries.

Easily accessible linear and hyperbranched polyesters as solid polymer electrolytes

Herein we report synthesis, characterization, thermal properties, ionic conductivity and oxidative stability of novel linear and hyperbranched polyesters. Tri-acrylate ester of commercially available 1,1,1-Tris(hydroxymethyl)propane (M1) was used as the primary building block for the synthesis of linear and hyperbranched polymers. A3 + B2 type polycondensation between M1 and dithiols of two different chain lengths (C3, C6) by 100 % atom efficient thiol-acrylate Michael addition reaction, followed by consumption of the unreacted acrylate esters (in the linear or terminal units) with 1-butane thiol produced two hyperbranched polymer namely HB-P1 and HB-P2. For synthesis of linear analogues, one of the equivalent acrylate esters was reacted first with 1-butane thiol and the resulting di-acrylate monomer was polymerized with the C3 and C6-dithiols, producing linear polymers L-P1 and L-P2. All the polymers showed molecular weight (Mn) in the range of 5000–6000 gmol−1 with low dispersity. TGA analysis revealed sufficient thermal stability of the polymers for the application as solid polymer electrolyte. All the polymers are amorphous, showing only a glass transition in the range of ∼ -45 °C (C3 spacer) to −50 °C (C6 spacer) and no crystallization peak. In presence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt the Tg increased by ∼ 10 °C. Solid polymer electrolytes were prepared by incorporating LiTFSI at a molar ratio of polymer carbonyl units to lithium of C=O/Li of 10 and ionic conductivity (σ) was evaluated by electrochemical impedance spectroscopy (EIS). Moderate values in the range of 10-7 S cm−1 were obtained at 25 °C with slightly higher values for the linear polymers. The ionic conductivity increased up to ∼ 2 orders of magnitude at higher temperatures. The oxidative stability of the polymer electrolytes against lithium-metal electrodes revealed onset potential for the first degradation in the range of 3.8 V, indicating moderate stability that might be suitable for testing applications in all-solid-state lithium-metal batteries using sulfur or lithium iron phosphate cathodes.

Lithiophilic Li-Si alloy-solid electrolyte interface enabled by high-concentration dual salt-reinforced quasi-solid-state electrolyte

Solid polymer electrolytes (SPEs) are urgently required to achieve practical solid-state lithium metal batteries (LMBs) and lithium-ion batteries (LIBs). Herein, we proposed a mechanism for modulating interfacial conduction and anode interfaces in high-concentration SPEs by LiDFBOP. Optimized electrolyte exhibits superior ionic conductivity and remarkable interface compatibility with salt-rich clusters: (1) polymer-plastic crystal electrolyte (P-PCE, TPU-SN matrix) dissociates ion pairs to facilitate Li+ transport in the electrolyte and regulates Li+ diffusion in the SEI. The crosslinking structure of the matrix compensates for the loss of mechanical strength at high-salt concentrations; (2) dual-anion TFSI–n-DFBOP–m in the Li+ solvation sheath facilitates facile Li+ desolvation and formation of salt-rich clusters and is conducive to the formation of Li conductive segments of TPU-SN matrix; (3) theoretical calculations indicate that the decomposition products of LiDFBOP form SEI with lower binding energy with LiF in the SN system, thereby enhancing the interfacial electrochemical redox kinetics of SPE and creating a solid interface SEI layer rich in LiF. As a result, the optimized electrolyte exhibits an excellent ionic conductivity of 9.31 × 10−4 S cm−1 at 30 °C and a broadened electrochemical stability up to 4.73 V. The designed electrolyte effectively prevents the formation of Li dendrites in Li symmetric cells for over 6500 h at 0.1 mA cm−2. The specific Li-Si alloy-solid state half-cell capacity shows 711.6 mAh g−1 after 60 cycles at 0.3 A g−1. Excellent rate performance and cycling stability are achieved for these solid-state batteries with Li-Si alloy anodes and NCM 811 cathodes. NCM 811|| Prelithiated silicon-based anode solid-state cell delivers a discharge capacity of 195.55 mAh g−1 and a capacity retention of 97.8% after 120 cycles. NCM 811||Li solid-state cell also delivers capacity retention of 84.2% after 450 cycles.

Misuse of XPS in Analyzing Solid Polymer Electrolytes for Lithium Batteries

One of the most powerful spectroscopic tools for battery analysis is X-ray photoelectron spectroscopy (XPS); however, its great power, must be accompanied by great responsibility for authenticity. Fluorine is documented to be unstable under XPS conditions, and fluorinated salts used in Li batteries show photodecomposition. As all-solid-state batteries advance, demand for surface characterization is increasing. Here, a popular solid polymer electrolyte comprising a fluorinated salt in a PEO matrix was measured by XPS. Rapid photodecomposition after few minutes produced mainly LiF, initially not found on the surface. Not being aware of such artifacts may lead to an erroneous analysis of the characterized electrochemical system.

The Versatile Establishment of Charge Storage in Polymer Solid Electrolyte with Enhanced Charge Transfer for LiF‐Rich SEI Generation in Lithium Metal Batteries

AbstractThe solid‐state electrolyte interface (SEI) between the solid‐state polymer electrolyte and the lithium metal anode dramatically affects the overall battery performance. Increasing the content of lithium fluoride (LiF) in SEI can help the uniform deposition of lithium and inhibit the growth of lithium dendrites, thus improving the cycle stability performance of lithium batteries. Currently, most methods of constructing LiF SEI involve decomposing the lithium salt by the polar groups of the filler. However, there is a lack of research reports on how to affect the SEI layer of Li‐ion batteries by increasing the charge transfer number. In this study, a porous organic polymer with “charge storage” properties was prepared and doped into a polymer composite solid electrolyte to study the effect of sufficient charge transfer on the decomposition of lithium salts. The results show in contrast to porphyrins, the unique structure of POF allows for charge transfer between each individual porphyrin. Therefore, during TFSI− decomposition to the formation of LiF, TFSI− can obtain sufficient charge, thereby promoting the break of C−F and forming the LiF‐rich SEI. Compared with single porphyrin (0.423 e−), POF provides 2.7 times more charge transfer to LiTFSI (1.147 e−). The experimental results show that Li//Li symmetric batteries equipped with PEO‐POF can be operated stably for more than 2700 h at 60 °C. Even the Li//Li (45 μm) symmetric cells are stable for more than 1100 h at 0.1 mA cm−1. In addition, LiFePO4//PEO‐POF//Li batteries have excellent cycling performance at 2 C (80 % capacity retention after 750 cycles). Even LiFePO4//PEO‐POF//Li (45 μm) cells have excellent cycling performance at 1 C (96 % capacity retention after 300 cycles). Even when the PEO‐base is replaced with a PEG‐base and a PVDF‐base, the performance of the cell is still significantly improved. Therefore, we believe that the concept of charge transfer offers a novel perspective for the preparation of high‐performance assemblies.

The Versatile Establishment of Charge Storage in Polymer Solid Electrolyte with Enhanced Charge Transfer for LiF-Rich SEI Generation in Lithium Metal Batteries.

The solid-state electrolyte interface (SEI) between the solid-state polymer electrolyte and the lithium metal anode dramatically affects the overall battery performance. Increasing the content of lithium fluoride (LiF) in SEI can help the uniform deposition of lithium and inhibit the growth of lithium dendrites, thus improving the cycle stability performance of lithium batteries. Currently, most methods of constructing LiF SEI involve decomposing the lithium salt by the polar groups of the filler. However, there is a lack of research reports on how to affect the SEI layer of Li-ion batteries by increasing the charge transfer number. In this study, a porous organic polymer with "charge storage" properties was prepared and doped into a polymer composite solid electrolyte to study the effect of sufficient charge transfer on the decomposition of lithium salts. The results show in contrast to porphyrins, the unique structure of POF allows for charge transfer between each individual porphyrin. Therefore, during TFSI- decomposition to the formation of LiF, TFSI- can obtain sufficient charge, thereby promoting the break of C-F and forming the LiF-rich SEI. Compared with single porphyrin (0.423 e-), POF provides 2.7 times more charge transfer to LiTFSI (1.147 e-). The experimental results show that Li//Li symmetric batteries equipped with PEO-POF can be operated stably for more than 2700 h at 60 °C. Even the Li//Li (45 μm) symmetric cells are stable for more than 1100 h at 0.1 mA cm-1. In addition, LiFePO4//PEO-POF//Li batteries have excellent cycling performance at 2 C (80 % capacity retention after 750 cycles). Even LiFePO4//PEO-POF//Li (45 μm) cells have excellent cycling performance at 1 C (96 % capacity retention after 300 cycles). Even when the PEO-base is replaced with a PEG-base and a PVDF-base, the performance of the cell is still significantly improved. Therefore, we believe that the concept of charge transfer offers a novel perspective for the preparation of high-performance assemblies.

Synthesis of nanoporous solid polymer electrolyte AuNiCe/NC hydrogenation membrane electrode

In this study, using graphite fiber cloth as the support, gold-based solid polymer electrolyte (SPE) membrane electrodes were synthesized by high-vacuum ion beam sputtering, nitrogen doping of the support, combined electrochemical dealloying, and hot-pressing technology. The application of the SPE membrane electrode to couple hydrogen evolution and liquid organic hydrogen storage is of significant importance for sustainable hydrogen energy and efficient carbon dioxide conversion. Using various characterization techniques, we systematically analyzed the phase structure, surface morphology, porous structure, and electrocatalytic performance of the membrane electrode for the hydrogenation of cyclohexene. The results indicated that doping the carbonaceous support with nitrogen (NC), doping with cerium as catalyst promoter, and combined electrochemical dealloying can all enhance the activity of the catalyst. Cerium doping provides the catalyst with oxygen vacancies for accelerated electron transfer. After combined electrochemical dealloying, AuNiCe/NC formed a three-dimensional bicontinuous porous structure. The electrochemically active surface area increased by 23.94 times, the energy consumption of catalytic cyclohexene hydrogenation decreased by 35.7%, and current efficiency and the formation rate of cyclohexane increased by 54.9% and 29.4%, respectively.

Reinforced flexible solid-state electrolyte membrane by polyurethane polymer of intrinsic microporosity for high-energy-density lithium metal battery

Poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are restricted in commercial applications due to the low ionic conductivity at ambient temperature and fragile mechanical properties. Polyurethanes (PUs) are unique materials coupled with superior rigidity and flexibility. Herein, we designed a novel polyurethane polymer of intrinsic microporosity (PPU), which was incorporated with PEO-based polymer electrolyte to prepare composite polymer electrolyte (CPE). The physicochemical and electrochemical properties of CPE membranes were explored. The high ionic conductivity (1.82 × 10−3 S cm−1 at 50 °C) and superior interfacial stability with the lithium anode was obtained. Furthermore, the rate performances and the cycling properties of CPE in LiFePO4 (LFP) batteries were extensively studied. The CPE-15% PPU film showed the excellent electrochemical stability of 84.3% capacity retention after 890 cycles at 0.5 C and 82.4% capacity retention after 500 cycles at 1.0 C at 50 °C. Especially, the CPE matched with high-voltage LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode delivered long-term stable cycling performances. The novel polymer electrolyte acquired could open up a new horizon to achieve high stable lithium metal batteries.

Facile in situ polymerization synthesis of poly(ionic liquid)-based polymer electrolyte for high-performance solid-state batteries

The rational one-step design of poly(ionic liquid) solid polymer electrolyte (PIL-SPE) with outstanding ionic conductivity and inferior interfacial resistance with Li-electrode to preclude the Li-dendrite growth and interfacial instability of solid-state lithium metal batteries (ASLMBs) remains a grand challenge. Herein, we provide a s facile, one-step, and productive approach for the synthesis of PIL-SPE via the in situ polymerization of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfony)imide ([VBIm][TFSI]) in the presence of bis(trifluoromethane) sulfonamide lithium salt (LiTFSI) using azodiisobutyronitrile (AIBN) as initiator. This approach endows a compact and compatible interface between Li-electrode and PIL-SPE with an excellent ionic conductivity that depends on the Li-salt concentration. Thereby, in situ polymerization of monomer with 40 wt% LiTFSI (PIL-SPE-LiTFSI-40) revealed the highest ionic conductivity of 1.35 × 10-3 S cm−1 at 303 K and 6.16 × 10-3 S cm−1 at 353 K, besides excellent lithium transference number (0.54), oxidative stability up to 5.3 V, and constant current plating/stripping cycles for 1000 h at 0.15 mA cm−2. Meanwhile, ASLMBs composed of PIL-SPE with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes delivered discharge capacities of 164.3 mA h g−1 and 155.3 mA h g−1 at 0.1 C, respectively, along with 92 % capacity retention after 100 cycles. This study may revolutionize the synthesis of PIL-SPE electrolytes for the next generation of efficient and durable ASLMBs.

Enhancing the Performance of Nanocrystalline TiO2 Dye-Sensitized Solar Cells with Phenothiazine-Doped Blended Solid Polymer Electrolyte

Enhancing the Performance of Nanocrystalline TiO2 Dye-Sensitized Solar Cells with Phenothiazine-Doped Blended Solid Polymer Electrolyte

The Progress of Polymer Composites Protecting Safe Li Metal Batteries: Solid-/Quasi-Solid Electrolytes and Electrolyte Additives.

The impressive theoretical capacity and low electrode potential render Li metal anodes the most promising candidate for next-generation Li-based batteries. However, uncontrolled growth of Li dendrites and associated parasitic reactions have impeded their cycling stability and raised safety concerns regarding future commercialization. The uncontrolled growth of Li dendrites and associated parasitic reactions, however, pose challenges to the cycling stability and safety concerns for future commercialization. To tackle these challenges and enhance safety, a range of polymers have demonstrated promising potential owing to their distinctive electrochemical, physical, and mechanical properties. This review provides a comprehensive discussion on the utilization of polymers in rechargeable Li-metal batteries, encompassing solid polymer electrolytes, quasi-solid electrolytes, and electrolyte polymer additives. Furthermore, it conducts an analysis of the benefits and challenges associated with employing polymers in various applications. Lastly, this review puts forward future development directions and proposes potential strategies for integrating polymers into Li metal anodes.

Quasi-solid electrolytes based on ZIF-8 to improve the electrochemical properties of lithium-ion batteries across a wide temperature range

Poor safety of liquid electrolytes and low ionic conductivity of solid electrolytes under room temperature are two major constraints for high energy density, long-term stability and safety of lithium-ion batteries (LIBs). In order to remedy the deficiencies, a quasi-solid electrolyte (QSE) is developed by immobilizing liquid electrolyte into the host of porous 2-Methylimidazole zinc salt (ZIF-8), and then mixing them with solid polymer electrolyte solvent of polyoxyethylene (PEO). The QSE has an ionic conductivity of 0.44 mS cm−1 at 20 °C and 2.27 mS cm−1 at 50 °C. The assembled LiFePO4/QSE/Li batteries exhibit excellent electrochemical performance in a wide temperature range. A reversible capacity of 129.7 mAh g−1 at 0.5 C and 20 °C and high capacity retentation of 94.7% at 0.5 C and 50 °C are achieved after 100 cycles. Especially, the LiFePO4/QSE/graphite pouch full cell exhibits a capacity retention of 97.7% at 0.5 C and 25 °C. These results indicate that QSE is a suitable candidate for enhancing the electrochemical performance of LIBs.

Configuration design toward sustainably-released polymer electrolytes for enhancing ionic transport and cycle stability of solid lithium batteries

Poly(vinylidene difluoride) (PVDF)-based solid polymer electrolytes (SPEs) hold great promise in the practical deployment of solid lithium batteries (SLBs), but suffer from low ionic conductivity, poor interfacial compatibility, and unstable anode interface, especially without liquid wetting. Herein, we utilize poly (propylene carbonate) (PPC), which degrades into propylene carbonate (PC) when being contacted with alkaline Li-metal to construct the PVDF-based composite SPEs. Blended and bi-layered PVDF/PPC configurations are designed, of which the sustain-release effect of PPC, the ionic transport, and the cycle stability are compared. The evenly swelling of PC on PVDF enables a high ionic conductivity (1.2 × 10−4 S cm−1) and a low interfacial resistance (42 Ω cm−2) of bi-layered SPEs at 30 °°C and contributes to the homogeneous distribution of high current density inside electrolytes. Besides, the produced PC can accelerate the dissociation and decomposition of Li-salts, leading to the generation of a stable and uniform solid electrolyte interface. Consequently, the Li/LiFePO4 and Li/LiNi0.6Co0.2Mn0.2O2 cells with bi-layered SPEs deliver a capacity of 163.1 and 151.4 mAh g−1 for 100 cycles at 0.2 C and 30 °C. This study provides a rational protocol for the design of PVDF SPEs and promotes the practical application of PVDF-based SLBs with desirable performances.

A three-dimensional co-continuous network structure polymer electrolyte with efficient ion transport channels enabling ultralong-life all solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) have emerged as one of the most promising candidates for the construction of solid-state lithium batteries due to their excellent flexibility, scalability, and interface compatibility with electrodes. Herein, a novel all-solid polymer electrolyte (PPLCE) was fabricated by the copolymer network of liquid crystalline monomers and poly(ethylene glycol) dimethacrylate (PEGDMA) acts as a structural frame, combined with poly(ethylene glycol) diglycidyl ether short chain interspersed serving as mobile ion transport entities. The preparaed PPLCEs exhibit excellent mechanical property and outstanding electrochemical performances, which is attributed to their unique three-dimensional co-continuous structure, characterized by a cross-linked semi-interpenetrating network and an ionic liquid phase, resulting in a distinctive nanostructure with short-range order and long-range disorder. Remarkably, the addition of PEGDMA is proved to be critical to the comprehensive performance of the PPLCEs, which effectively modulates the microscopic morphology of polymer networks and improves the mechanical properties as well as cycling stability of the solid electrolyte. When used in a lithium-ion symmetrical battery configuration, the 6 wt%-PPLCE exhibites super stability, sustaining operation for over 2000 h at 30 °C, with minimal and consistent overpotential of 50 mV. The resulting Li|PPLCE|LFP solid-state battery demonstrates high discharge specific capacities of 160.9 and 120.1 mA h g−1 at current densities of 0.2 and 1 C, respectively. Even after more than 300 cycles at a current density of 0.2 C, it retaines an impressive 73.5% capacity. Moreover, it displayes stable cycling for over 180 cycles at a high current density of 0.5 C. The super cycle stability may promote the application for ultralong-life all solid-state lithium metal batteries.

Building Stable Solid-State Potassium Metal Batteries.

Solid-state potassium metal batteries (SPMBs) are promising candidates for the next generation of energy storage systems for their low cost, safety, and high energy density. However, full SPMBs are not yet reported due to the K dendrites, interfacial incompatibility, and limited availability of suitable solid-state electrolytes. Here, stable SPMBs using a new iodinated solid polymer electrolyte (ISPE) are presented. The functional ions reconstruct ion transport channels, providing efficient potassium ion transport. ISPE shows a combination of high ionic conductivity, superior interfacial compatibility, and electrochemical stability. In situ alloying and iodinated interlayer increase K metal compatibility for prolonged cycling with low polarization. Moreover, the ISPE enables SPMBs with Prussian blue cathode stable operation at a high voltage of 4.5V, a superior rate capability, and long-term cycling over 3000 cycles (4.2V vs K+/K) with an ultra-high coulombic efficiency of 99.94%. More importantly, a classic solid-state potassium metal pouch cell achieves 4.2V stable cycling over 800 cycles with a high retention of 93.6%, presenting a new development strategy for secure and high-performance rechargeable solid-state potassium metal batteries.

Confining Polymer Electrolyte in MOF for Safe and High-Performance All-Solid-State Sodium Metal Batteries.

Nanoconfined polymer molecules exhibit profound transformations in their properties and behaviors. Here, we present the synthesis of a polymer-in-MOF single ion conducting solid polymer electrolyte, where polymer segments are partially confined within nanopores ZIF-8 particles through Lewis acid-base interactions for solid-state sodium-metal batteries (SSMBs). The unique nanoconfinement effectively weakens Na ion coordination with the anions, facilitating the Na ion dissociation from salt. Simultaneously, the well-defined nanopores within ZIF-8 particles provide oriented and ordered migration channels for Na migration. As a result, this pioneering design allows the solid polymer electrolyte to achieve a Na ion transference number of 0.87, Na ion conductivity of 4.01×10-4 S cm-1, and an extended electrochemical voltage window up to 4.89 V vs. Na/Na+. The assembled SSMBs (with Na3V2(PO4)3 as the cathode) exhibit dendrite-free Na-metal deposition, promising rate capability, and stable cycling performance with 96 % capacity retention over 300 cycles. This innovative polymer-in-MOF design offers a compelling strategy for advancing high-performance and safe solid-state metal battery technologies.

Polycaprolactone-Li6PS5Cl composite polymer electrolytes for stable room temperature all-solid-state lithium batteries

Incorporating inorganic fillers into solid polymer electrolytes (SPEs) to construct composite polymer electrolytes (CPEs) serves as an effective strategy to comprehensively enhance the properties of solid electrolytes. Herein, a CPE is fabricated by integrating Li6PS5Cl particles into polycaprolactone (PCL). The addition of active fillers could effectively weaken the crystallization of polymer and increase the ionic conductivity of the solid electrolyte. In particular, the PCL-based polymer electrolyte with 3% Li6PS5Cl (PCL-3) exhibits an excellent ionic conductivity of 1.36×10−4 S cm−1 at room temperature, which is one order higher than that of PCL polymer solid electrolyte. And it achieves a high critical current density of 2.2 mA cm−2 with a capacity of 2.2 mAh cm−2. The assembled Li symmetric battery can cycle steadily for more than 3000 h at 0.5 mA cm−2 under room temperature. The LiFePO4/PCL-3/Li all-solid-state battery maintains a capacity of 125.3 mAh g−1 after 400 cycles at 0.2 C under room temperature. Notably, the LiFePO4//Li battery also shows stable cycling at 40 °C, exhibiting high reversible specific capacities of 156.7 mAh g−1 and 126.3 mAh g−1 with a retention rate of 97.15% and 94.6% at 0.2 C and 0.5 C after 100 cycles, respectively, showing promising application prospects for all-solid-state lithium metal batteries.