Highest Room Temperature Conductivity Research Articles

In situ polymerization of 1,3-dioxolane and formation of fluorine/boron-rich interfaces enabled by film-forming additives for long-life lithium metal batteries.

In situ polymerized 1,3-dioxolane (PDOL) is widely utilized to construct solid polymer electrolytes because of its high room-temperature ionic conductivity and good compatibility with lithium metal. However, the current polymerization additives used in PDOL do not effectively contribute to the formation of a robust solid electrolyte interphase (SEI), leading to decreased cycle life. Herein, a film-forming Lewis acid, tris(hexafluoroisopropyl) borate (THB), is demonstrated not only to be a catalyst for the ring-opening polymerization of DOL, but also an additive for the formation of a stable fluorine- and boron-rich SEI to improve the interfacial stability and suppress the Li dendrite growth. Moreover, molecular dynamics simulations and experimental results demonstrate that the introduction of THB can promote the dissociation of lithium salt and release more Li+ while the boron site can effectively restrict the free movement of TFSI- anion, thus increasing Li+ transference numbers (0.76) and ensuring the long-term cycling stability of cells. By using THB-PDOL, a stable cycling of Li‖Li symmetric cell for 600 h at a capacity of 0.5 mA h cm-2 can be achieved. Furthermore, employing THB-PDOL in Li‖LiFePO4 full cell enables a capacity retention of 98.64% after 300 cycles at 1C and a capacity retention of 95.39% after 200 cycles at a high temperature (60 °C). At the same time, this electrolyte is also suitable for the Li‖NCM523 full cell, which also achieves excellent stability of more than 180 cycles. This film-forming Lewis acid additive provides ideas for designing low-cost, high-performance PDOL-based lithium metal batteries.

Ion-conductive vs. non-ion-conductive ceramic fillers in silane-linked polyethylene oxide-based composite polymer electrolytes with high room-temperature ionic conductivity

Surface-modified ZrO2 fillers strongly facilitate Li+ transport in PEO-based electrolytes, but even simple addition of the modifier serves to greatly improve ionic conductivity, proving the crucial role of the additive–matrix interaction.

Sulfide electrolytes for all-solid-state sodium batteries: fundamentals and modification strategies.

Sulfide solid-state electrolytes (SSSEs) have garnered overwhelming attention as promising candidates for high-energy-density all-solid-state sodium batteries (ASSSBs) due to their high room-temperature ionic conductivity and excellent mechanical properties. However, the poor chemical/electrochemical stability, narrow electrochemical windows, and limited adaptability to cathodes/anodes of SSSEs hinder the performance and application of SSSEs in ASSSBs. Consequently, a comprehensive understanding of the preparation methods, fundamental properties, modification techniques, and compatibility strategies between SSSEs and electrodes is crucial for the advancement of SSSE-based ASSSBs. This review summarizes the SSSEs based on their compositional makeup and crystal structure, aiming to elucidate the Na+ conduction mechanisms. It also provides an overview of modification strategies designed to enhance ionic conductivity, chemical/electrochemical stability, and interfacial compatibility with electrodes. Furthermore, we outline the challenges and strategies related to the interfaces of SSSEs with cathodes/anodes. Finally, we discuss the existing challenges facing SSSEs and propose the future research directions for SSSE-based ASSSBs.

(Invited) Overview of Ionic Liquid Electrolytes Doped with δ-Metal Halides for Advanced Post-Lithium-Ion Batteries

Humankind is currently facing a global transition towards a green electrification of both energy production and transportation. There is an urgent need to find new approaches for the storage of energy derived from renewable sources, such as solar irradiation, wind and waves. In addition, electric cars require energy storage or conversion systems capable of providing engine power. To these ends, secondary batteries are an attractive and viable solution, especially in the form of the relatively mature Li-ion technology. Unfortunately, Li power sources suffer from high cost, low Li earth-crust abundance, and toxicity of their electrochemical components (e.g., the Co-based cathodes). Such disadvantages demand the exploration of new energy storage devices based on alternative chemistries (e.g., Na, Mg, Ca).Since their discovery [1-5], electrolytes based on disordered or delta metal halide salts (e.g., δ-MgCl2, δ-LiCl, δ-MgI2) have received widespread attention due to their intriguing physical-chemical properties. Subsequently, electrolytes comprised of ionic liquid solvents dispersing various δ-metal halide salts were investigated [6-9]. These latter ion-conducting systems are characterized by: (i) very high room-temperature ionic conductivity; (ii) wide thermal, chemical and electrochemical stability; and (iii) high coulombic efficiency and very low overpotentials in the metal deposition and stripping processes.In this contribution, a comparison of different families of ionic liquids will be proposed. In particular, the effects of the use of δ-metal halide salts (e.g., δ-MgCl2, δ-LiCl, and δ-NaCl) on the thermal stability, vibrational features, and electrochemical properties of the resulting electrolytes will be considered. The conductivity mechanisms will be analyzed side-by-side, revealing how ionic conductivity is modulated by the metal ions (e.g., Mg2+, Li+, Na+), on the basis of broadband electrical spectroscopy results. Acknowledgments The authors acknowledge support in the form of the following grants: project “Interplay between structure, properties, relaxations and conductivity mechanism in new electrolytes for secondary Magnesium batteries” (Grant Agreement W911NF-21-1-0347-(78622-CH-INT)) of the U.S. Army Research Office; project “ACHILLES” (prot. BIRD219831) of the University of Padua; project “VIDICAT” (Grant Agreement 829145) of the FET-Open call of Horizon 2020; project “Polymer electrolytes for Sodium Batteries” (Grant Agreement 72957-00 01) sponsored by Natrion Inc. and the CUNY Sensor CAT.

NASICON-type Ta5+ substituted LiZr2(PO4)3 with improved ionic conductivity as a prospective solid electrolyte

The need to develop safe solid-state lithium batteries has stimulated intense research efforts for Li+ solid electrolytes. However, the low conductivity limits the development of NASICON LiZr2(PO4)3 (LZP) electrolyte. Here, the doping effects of Ta on the structure, surface morphologies and electrochemical properties of Li1-xZr2-xTax(PO4)3 (LZTP, x = 0, 0.01, 0.02, 0.04, 0.06 and 0.08) solid electrolyte were analyzed. LZTP was prepared using a simple solid-state reaction route, followed by sintering at 1200 °C for 12 h. A proper content of Ta5+ substitution for Zr4+ is beneficial to stabilize the high conductive rhombohedral (α) phase of LZP at room temperature. Doping Ta5+ is conducive to unblocking of Li+ at the M1 site and facilitates the occupation of Li+ at the M2 site, thereby expanding the pathway for Li+ conduction. Rietveld refinement data demonstrated that the Zr–O and P–O bond lengths (dZr-O and dP-O) increased with a decrease in Zr–O–P bond angles (θZr-O-P) as x rose. The distortions in the ZrO6 octahedron may weaken the coulomb attraction in Li+-O2-, resulting in a lower activation energy (Ea) and a higher Li+ conductivity. The highest room-temperature conductivity (6.06 × 10−5 S cm−1) was obtained at x = 0.06, which reached 1.5 × 10−4 S cm−1 at 50 °C. The Ea was found to decrease from 0.388 eV (x = 0) to 0.306 eV (x = 0.06). In addition, Ta doping resulted in improved connectivity and reduced pore formation, which also contributed to the decrease in resistance. The Raman spectrum demonstrated that some phonon modes of bending vibration in PO4 were degenerate and external modes became too weak to be observed or even disappeared as Ta content increased. This change in the modes also had an impact on the Li+ conductivity. Overall, the LZTP-0.06 appears to be a promising candidate for the solid electrolyte.

A flux growth technique for high quality cubic boron arsenide bulk single crystals

The growth of single crystal cubic boron arsenide (c-BAs) has attracted considerable interest due to its high room-temperature thermal conductivity and high ambipolar electrical mobility. However, currently the only growth technique reported for c-BAs crystals is the chemical vapor transport (CVT) method, which exhibits several drawbacks with regard to size scalability and crystal quality control, thereby hindering the further advancement of this semiconductor material. Herein, we report a flux growth technique using liquid arsenic (l-As) as a reaction medium at high pressures for the growth of high-quality c-BAs crystals with several millimeters size. The outstanding properties, including high uniformity, lower defect density, and lower carrier concentration of the as-grown c-BAs single crystals from flux growth, have been verified via a combination of techniques including x-ray diffraction, Raman scattering, photoluminescence spectroscopy, and electrical transport measurements, in comparison with the CVT-grown crystals.

The Universal Super Cation-Conductivity in Multiple-cation Mixed Chloride Solid-State Electrolytes.

As exciting candidates for next-generation energy storage, all-solid-state lithium batteries (ASSLBs) are highly dependent on advanced solid-state electrolytes (SSEs). Here, using cost-effective LaCl3 and CeCl3 lattice (UCl3 -type structure) as the host and further combined with a multiple-cation mixed strategy, we report a series of UCl3 -type SSEs with high room-temperature ionic conductivities over 10-3 S cm-1 and good compatibility with high-voltage oxide cathodes. The intrinsic large-size hexagonal one-dimensional channels and highly disordered amorphous phase induced by multi-metal cation species are believed to trigger fast multiple ionic conductions of Li+ , Na+ , K+ , Cu+ , and Ag+ . The UCl3 -type SSEs enable a stable prototype ASSLB capable of over 3000 cycles and high reversibility at -30 °C. Further exploration of the brand-new multiple-cation mixed chlorides is likely to lead to the development of advanced halide SSEs suitable for ASSLBs with high energy density.

Electrochemically induced crystalline-to-amorphization transformation in sodium samarium silicate solid electrolyte for long-lasting sodium metal batteries

Exploiting solid electrolyte (SE) materials with high ionic conductivity, good interfacial compatibility, and conformal contact with electrodes is essential for solid-state sodium metal batteries (SSBs). Here we report a crystalline Na5SmSi4O12 SE which features high room-temperature ionic conductivity of 2.9 × 10−3 S cm−1 and a low activation energy of 0.15 eV. All-solid-state symmetric cell with Na5SmSi4O12 delivers excellent cycling life over 800 h at 0.15 mA h cm−2 and a high critical current density of 1.4 mA cm−2. Such excellent electrochemical performance is attributed to an electrochemically induced in-situ crystalline-to-amorphous (CTA) transformation propagating from the interface to the bulk during repeated deposition and stripping of sodium, which leads to faster ionic transport and superior interfacial properties. Impressively, the Na|Na5SmSi4O12|Na3V2(PO4)3 sodium metal batteries achieve a remarkable cycling performance over 4000 cycles (6 months) with no capacity loss. These results not only identify Na5SmSi4O12 as a promising SE but also emphasize the potential of the CTA transition as a promising mechanism towards long-lasting SSBs.

Optical and temperature-dependent electrical and dielectric properties of ultrasound-synthesized CdS quantum dots

CdS quantum dots (QDs) were synthesized by the ultrasound-assisted chemical precipitation technique. The structure analysis revealed the presence of bi-structural cubic and hexagonal phases with an average crystallite size of 3 nm. The N2-adsorption isotherm exhibited the evolution of meso-/macro-porous interfaces with a pore size of 7.56 nm and a surface area of 44.41 m2·g−1. The improvement of the quantum size effect in CdS QDs resulted in the increase of optical bandgap to 2.52 eV compared with the corresponding bulk phase. However, the analysis of long-tail states absorption revealed a very small Urbach energy of about 76 meV compared with CdS QDs prepared by other techniques. The as-synthesized CdS QDs revealed high room-temperature DC conductivity of 2.56 × 10–6 Ω−1 · m−1 and very small activation energy of 268 meV facilitating tunnelling of the thermionically excited carrier through the high bandgap of CdS QDs. The frequency-dependent behavior of AC conductivity (σ AC) and dielectric constant (ε r) of CdS QDs were investigated at different temperatures in the range from 303 K to 453 K. It was observed that both σ AC and ε r were improved with increasing temperature up to 363 K followed by a sudden decrease at higher temperatures.

Single-Ion Conductive Polymer-Based Composite Electrolytes for High-Performance Solid-State Lithium Metal Batteries.

Flexible composite polymer electrolytes (CPEs) with inorganic electrolyte fillers dispersed in polymer electrolytes integrate the merits of the polymer and inorganic electrolytes and have attracted much attention in recent years. In order to increase the electrochemical performance, especially the low lithium (Li)-ion transference number in traditional dual-ion Li salt-containing CPEs, single-ion conductive CPEs are synthesized with a single-ion polymer conductor (SIPC) as the matrix and Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) particles as the active fillers. The single-ion conductive CPEs show a high Li-ion transference number (up to 0.96), high room-temperature (RT) ionic conductivity (>1.0 × 10-4 S cm-1 ), wide electrochemical stability window (>5.0V, vs Li/Li+ ), and excellent long-term cycling stability with Li metal at RT (3200h). Based on the SIPC-LLZTO CPE, the solid-state lithium metal batteries with LiFePO4 - and LiCoO2 -based cathodes deliver average discharge capacities of 159 mAh g-1 for 600 cycles and 119 mAh g-1 for 200 cycles at RT, respectively. This study sheds light on the design of high-performance CPEs for next-generation solid-state lithium metal batteries.

Transition from Vogel-Fulcher-Tammann to Arrhenius Ion-Conducting Behavior in Poly(Ethyl Acrylate)-Based Solid Polymer Electrolytes via Succinonitrile Plasticizer Addition

Solid polymer electrolytes (SPEs) offer potential advantages over liquid electrolytes, including flexibility, safety, and processability. However, they suffer from low room-temperature ionic conductivity. Recently, it has been reported a poly(ethyl acrylate) based (polyEA) SPE, by incorporating 50 wt% of succinonitrile (SN) solid plasticizer, 30 wt% of lithium salt and 5 wt% of fluoroethylene carbonate additive, which achieves a high room-temperature ionic conductivity of 1.01 × 10−3 S cm−1 (Nat. Nanotechnol, 2022, 17, 768-776). This novel SPE exhibits stability against Li0 and anodic stability up to 4.9 V vs Li+/Li. However, the specific mechanism responsible for its high ionic conductivity remains elusive. In this work, by adjusting the weight ratio of SN in the SPE, a transition from Vogel-Fulcher-Tammann to Arrhenius ion-conducting behavior is observed. It is demonstrated that the addition of SN leads to the gradual decoupling of Li-ion from the polymer backbone and its coordination with SN, as revealed by 6Li solid-state nuclear magnetic resonance spectroscopy. As a result, Li-ion migration primarily occurs through SN rather than the segmental motion of the polymer backbone. Performances of the SPE in Cu||Li, Li||Li and a LiFePO4||Li pouch cells are shown to demonstrate the commercial viability of this SPE in Li0-anode solid-state batteries.

Adverse Effects of Trace Non-polar Binder on Ion Transport in Free-standing Sulfide Solid Electrolyte Separators

Sulfide solid-state electrolyte (SE) possesses high room-temperature ionic conductivity. However, fabrication of the free-standing, sheet-type thin sulfide SE film electrolyte to enable all-solid-state batteries to deliver high energy and power density remains challenging. Herein we show that argyrodite sulfide (Li6PS5Cl) SE can be slurry cast to form free-standing films with low (≤5 wt%) loadings of poly(isobutylene) (PIB) binder. Two factors contribute to a lower areal specific resistance (ASR) of the thin film SEs benchmarked to the pristine powder pellet SSE counterparts: i) 1–2 orders reduced thickness and ii) reasonably comparable ionic conductivity at room temperature after the isostatic pressing process. Nevertheless, an increasing polymer binder loading inevitably introduced voids in the thin film SEs, compromising anode/electrolyte interfacial ion transport. Our findings highlight that electrolyte/electrode interfacial stability, as well as the selection of slurry components, including sulfide SE, binder, and solvent, play essential roles in thin film sulfide electrolyte development.

Construction and Interfacial Modification of a β-PbSnF4 Electrolyte with High Intrinsic Ionic Conductivity for a Room-Temperature Fluoride-Ion Battery.

Solid-state fluoride-ion batteries (FIBs) attract significant attention worldwide because of their high theoretical volume, energy density, and high safety. However, the large interfacial resistance caused by the point-point contact between the electrolyte and the electrode seriously impedes their further development. Using liquid-phase therapy to construct a conformal interface is a good choice to eliminate the influence of inadequate contact between the electrode and the electrolyte. In this study, a β-PbSnF4 solid-state electrolyte with high room-temperature ionic conductivity is prepared, and a trace amount of the liquid electrolyte (LE) between the electrode and the electrolyte is introduced in order to minimize the interfacial resistance and enhance the cycle life. The Allen-Hickling simulations show that the introduction of an interfacial wetting agent (LE) can significantly reduce the energy barrier of charge transfer and mass transfer processes at the interface and reciprocate FIBs an enhanced interfacial reaction kinetics. As a result, the initial discharge capacity of the fabricated FIBs is 210.5 mAh g-1 and the capacity retention rate is 82.6% after 50 cycles at room temperature, while the initial discharge capacity of the unmodified battery is only 170.9 mAh g-1 and the capacity retention rate is 22.1% after 50 cycles. Therefore, interfacial modification with a trace amount of LE provides a significant exploration for the improvement of FIB performances.

Manufacturing High-Energy-Density Sulfidic Solid-State Batteries

All-solid-state batteries (ASSBs) using sulfide solid electrolytes with high room-temperature ionic conductivity are expected as promising next-generation batteries, which might solve the safety issues and enable the utilization of lithium metal as the anode to further increase the energy density of cells. Most researchers in the academic community currently focus on developing novel sulfide solid electrolytes, clarifying the interface issues between sulfide electrolytes and solid electrodes and mechanism of lithium dendrite growth in ASSB. However, there is a lacking in the technical route analysis about the commercialization of ASSBs based on sulfide solid electrolytes. This review mainly introduces the specific preparation methods of various parts in sulfide-based ASSBs, including the preparation methods of sulfide solid electrolyte particles, sulfide-based composite electrolyte membranes, composite cathodes and anodes, and analyzes the advantages and disadvantages of these methods. In addition, several schemes of ASSB assembly are also introduced. Finally, a perspective of large-scale production of sulfide-based ASSBs is provided, which is expected to accelerate the commercialization of sulfide-based ASSBs.

Ion Channel-Restructured Zwitterionic Covalent Organic Framework Solid Electrolyte for All-Solid-State Lithium Metal Batteries.

Organic solid electrolytes offer an effective route for safe and high energy-density all-solid-state Li metal batteries. However, it remains a challenge to devise a new strategy to promote the dissociation of strong ion pairs and the transport of ionic components in organic solid electrolytes. Herein, a zwitterionic covalent organic framework (Zwitt-COF) with well-defined chemical and pore structures is prepared as a solid electrolyte capable of accelerating the dissociation and transport of Li ions. The Zwitt-COF solid electrolyte exhibits a high room-temperature ionic conductivity of 1.65 × 10-4 S cm-1 with a wide electrochemical stability window. Besides, the Zwitt-COF solid electrolyte displays stable Li plating/stripping behavior via effective inhibition of the formation of Li dendrites and dead Li, leading to superior long-term cycle performance with retention of 99% discharge capacity and 98% Coulombic efficiency in an all-solid-state Li metal battery. Theoretical simulations reveal that the incorporation of zwitterionic groups into COF can facilitate the dissociation of strong ion pairs and reconstruct the AA-stacking configuration by dissociative adsorption of Li+ ions on Zwitt-COF producing linear hexagonal ion channels in the Zwitt-COF solid electrolyte. This strategy based on Zwitt-COF can provide an alternative way to construct various solid-state Li batteries. This article is protected by copyright. All rights reserved.

Fast Li+-conducting Zr4+-based oxychloride electrolyte with good thermal and solvent stability

Li2ZrCl6 with a trigonal structure is a low-cost Li+-conducting chloride electrolyte, which is stable at high voltages up to 4.2 V and is compatible with high-voltage cathodes. However, its relatively low room-temperature ionic conductivity, poor stability in different solvents and at high temperatures limit its application for next-generation all-solid-state batteries. Herein, we prepared new oxychloride electrolytes with different molar ratios of Li2O, ZrCl4, and LiCl, replacing Cl− with O2− anion to optimize the electrolyte performance. The results showed that increasing the Li2O content reduced the crystallization degree of trigonal Li2ZrCl6 and induced a monoclinic structure in the prepared oxychloride electrolyte. The oxychloride with the general formula Li2.22Zr1.11Cl5.33O0.67 had a high room-temperature ionic conductivity above 10−3 S cm−1. Moreover, introducing Li2O considerably increased the thermal and solvent stability of the electrolyte. Good ionic conductivity and stability of the electrolyte enable the stable cycling of all-solid-state Li-In/LiCoO2 batteries.

Influence of Solvent Evaporation Temperature on the Performance of Ternary Solid Polymer Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) Combining an Ionic Liquid and a Zeolite.

Solid polymer electrolytes (SPEs) will allow improving safety and durability in next-generation solid-state lithium-ion batteries (LIBs). Within the SPE class, ternary composites are a suitable approach as they provide high room-temperature ionic conductivity and excellent cycling and electrochemical stability. In this work, ternary SPEs based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a polymer host, clinoptilolite (CPT) zeolite, and 1-butyl-3-methylimidazolium thiocyanate ([Bmim][SCN])) ionic liquid (IL) as fillers were produced by solvent evaporation at different temperatures (room temperature, 80, 120, and 160 °C). Solvent evaporation temperature affects the morphology, degree of crystallinity, and mechanical properties of the samples as well as the ionic conductivity and lithium transference number. The highest ionic conductivity (1.2 × 10-4 S·cm-1) and lithium transference number (0.66) have been obtained for the SPE prepared at room temperature and 160 °C, respectively. Charge-discharge battery tests show the highest value of discharge capacity of 149 and 136 mAh·g-1 at C/10 and C/2 rates, respectively, for the SPE prepared at 160 °C. We conclude that the fine control of the solvent evaporation temperature during the preparation of the SPE allows us to optimize solid-state battery performance.

A scalable one-pot strategy for the development of polymer electrolytes adaptable to room-temperature high-voltage lithium batteries

Poly(ethylene oxide) (PEO) polymer electrolytes (PEs) have been commercially applied in LiFePO4||Li solid-state lithium batteries (SSLBs). However, it remains challenging to develop PEO-based PEs applicable to the high-voltage SSLBs with higher energy density, owing to the poor electrochemical stability of PEO. Herein, we report a scalable strategy for fabricating PEO-based PEs with high-voltage compatibility, by exploiting a new mechanism to stabilize the cathode-electrolyte interface in the high-voltage SSLBs. The protocol only involves a one-pot synthesis procedure to covalently crosslink the PEO chains, in the presence of high-content lithium bis(trifluoromethylsulphonyl)imide (LiTFSI) salts and N,N-dimethylformamide (DMF). LiTFSI-DMF supramolecular aggregates are formed and firmly embedded in the polymer network, endowing the PE with high room-temperature ionic conductivity. The dissociated and highly concentrated TFSI− anions can enter the Helmholtz layer close to the high-voltage cathode, leading to the formation of a thin and homogeneous cathode electrolyte interface (CEI), mainly composed of LiF, on the cathode. The CEI with high electrochemical stability can effectively stabilize the cathode-electrolyte interface, enabling long-term stable cycling of the high-voltage LiCoO2||Li and nickel-rich NCM622||Li batteries at room temperature. The simplicity and scalability of the strategy makes the reported PEO-based PE potentially applicable in high-voltage SSLBs in practice.

In Situ Thermal Polymerization of a Succinonitrile-Based Gel Polymer Electrolyte for Lithium-Oxygen Batteries.

For lithium-oxygen batteries (LOBs), the leakage and volatilization of a liquid electrolyte and its poor electrochemical performance are the main reasons for the slow industrial advancement. Searching for more stable electrolyte substrates and reducing the use of liquid solvents are crucial to the development of LOBs. In this work, a well-designed succinonitrile-based (SN) gel polymer electrolyte (GPE-SLFE) is prepared by in situ thermal cross-linking of an ethoxylate trimethylolpropane triacrylate (ETPTA) monomer. The continuous Li+ transfer channel, formed by the synergistic effect of an SN-based plastic crystal electrolyte and an ETPTA polymer network, endows the GPE-SLFE with a high room-temperature ionic conductivity (1.61 mS cm-1 at 25 °C), a high lithium-ion transference number (tLi+ = 0.489), and excellent long-term stability of the Li/GPE-SLFE/Li symmetric cell at a current density of 0.1 mA cm-2 for over 220 h. Furthermore, cells with the GPE-SLFE exhibit a high discharge specific capacity of 4629.7 mAh g-1 and achieve 40 cycles.

Uncoordinated chemistry enables highly conductive and stable electrolyte/filler interfaces for solid-state lithium–sulfur batteries

Composite-polymer-electrolytes (CPEs) embedded with advanced filler materials offer great promise for fast and preferential Li+ conduction. The filler surface chemistry determines the interaction with electrolyte molecules and thus critically regulates the Li+ behaviors at the interfaces. Herein, we probe into the role of electrolyte/filler interfaces (EFI) in CPEs and promote Li+ conduction by introducing an unsaturated coordination Prussian blue analog (UCPBA) filler. Combining scanning transmission X-ray microscope stack imaging studies and first-principle calculations, fast Li+ conduction is revealed only achievable at a chemically stable EFI, which can be established by the unsaturated Co-O coordination in UCPBA to circumvent the side reactions. Moreover, the as-exposed Lewis-acid metal centers in UCPBA efficiently attract the Lewis-base anions of Li salts, which facilitates the Li+ disassociation and enhances its transference number (tLi+). Attributed to these superiorities, the obtained CPEs realize high room-temperature ionic conductivity up to 0.36 mS cm-1 and tLi+ of 0.6, enabling an excellent cyclability of lithium metal electrodes over 4,000 h as well as remarkable capacity retention of 97.6% over 180 cycles at 0.5 C for solid-state lithium-sulfur batteries. This work highlights the crucial role of EFI chemistry in developing highly conductive CPEs and high-performance solid-state batteries.