Ionic Conductivity Research Articles

Design of cellulose/polyethylene oxide/EMITFSI-based composite electrolyte with synergistic transport mechanism for high-performance solid-state lithium batteries

Despite its theoretically high energy density, polymer solid-state lithium batteries (PSSLBs) exhibit lower actual energy density. This discrepancy arises from the low ionic conductivity of the polymer solid-state electrolyte (PSSE) due to the coupling of lithium ion (Li+) transport to the relaxation of polymer chain segments. The objective of this study is to optimize the Li+ transport in PSSE. This is achieved by incorporating 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) to plasticize both cellulose and polyethylene oxide (PEO). By leveraging the synergistic effects of cellulose and PEO, an ion-conducting network is established. This network allows Li+ to form multiple Li-O coordination simultaneously with the hydroxyl group (OH) of cellulose and the ether group (EO) of PEO, thereby enabling Li+ to transport between the two polymers in a decoupled manner. The PSSE demonstrated an ionic conductivity of 4 × 10-4 mS/cm (at room temperature) and a Li+ transference number of 0.43, significantly exceeding traditional PEO-based values of 10-5 mS/cm and 0.1–0.2. Additionally, the high voltage stability of EMITFSI extends the electrochemical stability window of PSSE, achieving a stability window of 5 V. The assembled LiFePO4/Li cell achieved a specific capacity of 138 mA h/g at 50℃ (0.5C) with a capacity retention rate of 80 % after 280 cycles. This represents an innovative method for preparing high-energy–density solid-state lithium batteries.

A highly-proton conductive poly(vinyl alcohol)/silica nanocomposite membrane for PANI@GNP symmetric supercapacitor separator

Polyaniline (PANI) has potential as an anode and cathode for proton based batteries (PBs) owing to its high energy density (295 mAh g−1) and excellent reversible redox activity. Achieving proton electrolytes with fast single-proton conduction behavior, separator-required mechanical properties and good proton transport channel is essential but extremely challenging for the practical success of PBs. Herein, this proton separator is constructed with nano-silica grid points in polyvinyl alcohol (PVA) chains cross-linked by sulfuric acid. Results show that PVA/inorganic composite proton membrane (PIC-PM) can immobilize the sulfate anions and help dissociate H+, which leads to a high ionic conductivity (8.6 × 10−2 S cm−1). Moreover, PIC-PM shows enough toughness and mechanical strength to puncture resistance. When the PIC-PM was applied to assemble a PANI@GNP symmetric supercapacitor, it delivers a high capacity of 943.1 F/g at 0.5 A/g; a rate capability of 74.9 % with the current density increasing from 0.5 to 5 A/g; and a capacity retention rate of 84.3 % after 1000 cycles in a current density of 3.5 A/g.

Conceptualizing Surface-Like Diffusion for Ultrafast Ionic Conduction in Solid-State Materials.

Surface-like diffusion is a recently proposed concept to explain the mechanism of ultrafast ionic conduction in high-rate oxide (e. g., niobium oxides and their alloys with TiO2 and WO3) and framework materials (e. g., Prussian blue analogs). This perspective seeks to illustrate the structural origin, theoretical foundation, and experimental evidences of surface-like diffusion. Unlike classical lattice diffusion, which typically involves ionic hopping between adjacent interstitial sites in solids, surface-like diffusion occurs when ions-that are significantly smaller than the interstitials-migrate along the off-center path in the diffusion channel. This mechanism results in an exceptionally low activation energy (Ea) down to 0.2 eV, which is crucial for achieving high-rate performance in electrochemical devices such as lithium-ion and sodium-ion batteries. This concept review also discusses the criteria to identify materials with potential surface-like diffusion and outlines theoretical and experimental tools to capture such phenomenon. Several candidates for further investigation are proposed based on the current understanding of the mechanism.

Synthesis and characterization of soluble pyridinium-containing copolyimides.

Novel ionene-type cationic copolyimides based on 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(1,4-phenylenediisopropylidene)bisaniline (BIS P), and 2,6-diaminopyridine (DAP) were synthesized. The copolyimides were obtained in two stages: first, the copolyimides with the 0/1, 0.2/0.8, 0.3/0.7, 0.5/0.5, 0.6/0.4 and 1/0 DAP/Bis P ratios were obtained through thermal imidization, and then quaternization of soluble copolyimides with methyl iodide was conducted for 24 or 48 h. The samples were characterized via FTIR, NMR and EDX methods to confirm their structure and composition. The cationic copolyimides with a DAP content of less than 0.3 showed initial weight loss (onset) at about 250 °C, according to TGA results and demonstrated solubility in chloroform. The highest ionic conductivity value of 0.234 S cm-1 was showed by the sample with 0.3 DAP content and 0.15 degree of quaternization. The stability of the membranes in alkaline media was evaluated using FTIR and TGA. It was shown that samples with a DAP content of more than 0.3 lost their integrity probably owing to partial hydrolysis of imide rings, while copolyimides with a DAP content of 0.2 and 0.3 remained stable.

Topotactic Reduction-Induced Stabilization of β-La2Mo2O8.68 Phase: Structure, Static Oxygen Disorder, and Electrical Properties.

La2Mo2O9 is acknowledged as an exceptional oxide ion conductor. It undergoes a reversible phase transition around 580 °C from the nonconductive low-temperature monoclinic α-La2Mo2O9 phase to the highly conductive high-temperature cubic β-La2Mo2O9 phase. In addition, La2Mo2O9 demonstrates complex chemistry under reducing conditions. This study reports, for the first time, the stabilization at ambient temperature of a novel cubic phase through a topotactic reduction of α-La2Mo2O9 employing CaH2. This phase contains approximately ∼3 atom % oxygen vacancies relative to the nominal composition (La2Mo2O8.68(1)). The cubic symmetry is associated with a static distribution of these vacancies, in contrast to the dynamic distribution observed in the high-temperature cubic β-La2Mo2O9 phase reported previously. Additionally, the material exhibits mixed-ion-electronic conduction, which expands its potential use in applications requiring both ionic and electronic transport.

Investigation of structural and electrical properties of electrolyte LaGaO3 for solid oxide fuel cell.

Electrochemical devices such as solid oxide fuel cells (SOFCs) allow the direct transformation of fuel's chemical energy into electrical power. Even though YSZ electrolyte-based conventional SOFCs are widely used in both laboratories and on a commercial scale, developing alternative ion-conducting electrolytes is crucial for enhancing SOFC performance at lower operating temperatures. In this work, we conducted a thorough computational analysis on the characteristics of Sr- and Mg-doped superior oxide ion conductors. We have used the DFT technique to examine the system's electrical and structural characteristics and the impact of doping. The GII value and LaGaO3 formation energy are used to investigate thermodynamical and structural stability, respectively. Theoretical investigations are validated against data to ensure the accuracy of the computational model. The research shows that the properties of Sr- and Mg-doped LaGaO3 have changed in a desirable way. This DFT study sheds light on the underlying mechanisms that affect the structural and electronic properties of LaGaO3 electrolytes and offers a thorough investigation of the synergistic effects of strontium and magnesium co-doping. The knowledge acquired is critical for the logical design and development of more stable and efficient solid oxide fuel cells.

Supramolecular Crystals based Fast Single Ion Conductor for Long‐Cycling Solid Zinc Batteries

AbstractThe solid polymer electrolytes (SPEs) used in Zn‐ion batteries (ZIBs) have low ionic conductivity due to the sluggish dynamics of polymer segments. Thus, only short‐range movement of cations is supported, leading to low ionic conductivity and Zn2+ transference (tZn2+). Zn‐based supramolecular crystals (ZMCs) have considerable potential for supporting long‐distance Zn2+ transport; however, their efficiency in ZIBs has not been explored. The present study developed a ZMC consisting of succinonitrile (SN) and zinc bis (trifluoromethylsulfonyl) imide (Zn(TFSI)2), with a structural formula identified as Zn(TFSI)2SN3. The ZMC has ordered three‐dimensional tunnels in the crystalline lattices for ion conduction, providing high ionic conductivities (6.02×10−4 S cm−1 at 25 °C and 3.26×10−5 S cm−1 at −35 °C) and a high tZn2+ (0.97). We demonstrated that a Zn‖Zn symmetrical battery with ZMCs has long‐term cycling stability (1200 h) and a dendrite‐free Zn plating/stripping process, even at a high plating areal density of 3 mAh cm−2. The as‐fabricated solid‐state Zn battery exhibited excellent performance, including high discharge capacity (1.52 mAh cm−2), long‐term cycling stability (83.6 % capacity retention after 70000 cycles (7 months)), wide temperature adaptability (−35 to 50 °C) and fast charging ability. The ZMC differs from SPEs in its structure for transporting Zn2+ ions, significantly improving solid‐state ZIBs while maintaining safety, durability, and sustainability.

Poly(Ionic Liquid) Electrolytes at an Extreme Salt Concentration for Solid-State Batteries.

Polymer-in-salt electrolytes were introduced three decades ago as an innovative solution to the challenge of low Li-ion conductivity in solvent-free solid polymer electrolytes. Despite significant progress, the approach still faces considerable challenges, ranging from a fundamental understanding to the development of suitable polymers and salts. A critical issue is maintaining both the stability and high conductivity of molten salts within a polymer matrix, which has constrained their further exploration. This research offers a promising solution by integrating cationic poly(ionic liquids) (polyIL) with a crystallization-resistive salt consisting of asymmetric anions. A stable polymer-in-salt electrolyte with an exceptionally high Li-salt content of up to 90 mol % was achieved, providing a valuable opportunity for the in-depth understanding of these electrolytes at an extremely high salt concentration. This work explicates how increased salt concentration affects coordination structures, glass transitions, ionic conductivity, and the decoupling and coupling of ion transport from structural dynamics in a polymer electrolyte, ultimately enhancing electrolyte performance. These findings provide significant knowledge advancement in the field, guiding the future design of polymer-in-salt electrolytes.

Ion conductivity and the stability of the interface between Na metal and Na3OCl

Ion conductivity and the stability of the interface between Na metal and Na3OCl

Optimizing Reversible Phase‐Transformation of FeS2 Anode via Atomic‐Interface Engineering Toward Fast‐Charging Sodium Storage: Theoretical Predication and Experimental Validation

AbstractSodium‐storage performance of pyrite FeS2 is greatly improved by constructing various FeS2‐based nanostructures to optimize its ion‐transport kinetics and structural stability. However, less attention has been paid to rapid capacity degradation and electrode failure caused by the irreversible phase‐transition of intermediate NaxFeS2 to FeS2 and polysulfides dissolution upon cycling. Under the guidance of theoretical calculations, coupling FeS2 nanoparticles with honeycomb‐like nitrogen‐doped carbon (NC) nanosheet supported single‐atom manganese (SAs Mn) catalyst (FeS2/SAs Mn@NC) via atomic‐interface engineering is proposed to address above challenge. Systematic electrochemical analyses and theoretical results unveil that the functional integration of such two type components can significantly enhance ionic conductivity, accelerate charge transfer efficiency, and improve Na+‐adsorption capability. Particularly, SAs Mn@NC with Mn‐Nx coordination center can reduce the decomposition barrier of Na2S and NaxFeS2 to further accelerate reversible phase transformation of Fe/Na2S→NaFeS2→FeS2 and polysulfides decomposition. As predicted, such FeS2/SAs Mn@NC showcases outstanding rate capability and fascinating cyclic durability. A sequence of kinetic studies and ex situ characterizations provide the comprehensive understanding for ion‐transport kinetics and phase‐transformation process. Its practical use is further demonstrated in sodium‐ion full cell and capacitor with impressive electrochemical capability and excellent energy‐density output.

Biomass‐based crosslinked composite anion exchange membranes using bacterial cellulose template towards enhanced ionic conductivity and alkaline stability

AbstractA balanced relationship among ionic conductivity, mechanical properties and alkaline stability of anion exchange membranes (AEMs) is essential for their practical application in fuel cells. Herein, a porous substrate (BC@LDH) with hierarchical structure was constructed using natural bacterial cellulose (BC) as a template and then in situ grew inorganic hydroxide ion conductor (layered double hydroxide, LDH). The membrane was fabricated via a filling together with sol–gel crosslinking strategy after impregnating an ionomer containing both quaternary ammonium and hydroxyl groups into the porous substrate and then crosslinked by organosiloxane. Due to the synergistic enhancement effect of BC, LDH and cross‐linking, the obtained membrane exhibited a tensile strength of 47.48 MPa that was 88.3% higher than that of the pure ionomer membrane, and showed an ionic conductivity of 70.7 mS cm−1 (80°C) which benefited from the introduction of ionic conductor LDH. More importantly, its alkaline stability was significantly improved and the residual conductivity ratio was still as high as 81.5% even after hot alkali treatment for 580 h. The direct methanol fuel cell assembled with this membrane exhibited a peak power density of 13.6 mW cm−2 with an open‐circuit voltage of 0.72 V, indicating its potential application in biomass‐based AEMs for fuel cells.Highlights Hierarchical porous substrate comprising LDHs anchored BC fiber was prepared. LDH@BC served as a reinforcing substrate and an ion transport medium. The crosslinked membrane showed significantly improved alkaline stability. The membrane had high ionic conductivity and mechanical strength. Providing a new way to design biomass‐based AEMs with high performance.

Silica-reinforced functional composite polymer electrolyte with high electrochemical compatibility for solid-state lithium metal battery

Composite polymer-ceramic electrolytes (CPEs) are emerging as viable substitute providing high ionic conductivity, mechanical stability, and good safety for the progress of all-solid-state rechargeable batteries. Here, SiO2 particles were generated from beach sands via a simple gelation method and embedded in to poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) to obtain precisely two types of the electrolytes namely, electrospun and solution casted. The 2.5 wt.% SiO2-embedded CPEs generated by electrospinning and solution-casting exhibit best ionic conductivities being 3.6 × 10–4 and 1.3 × 10–4 S cm-1 at 30 °C, respectively. The polarization voltage for the electrospun CPE was particularly low and showed an extremely stable voltage plateau up to 300 h demonstrating high electrochemical compatibility and immense cycling stability. Consequently, the all solid-state lithium metal battery (Li|CPE|LiFePO4) using the electrospun CPE initially exhibits a discharge capacity of 142 mAh g-1 at 0.1C-rate superior to that of the full cell using the solution-casted CPE.

Ion‐Permeable Electrospun Scaffolds Enable Controlled In‐Vitro Electrostimulation Assay of Myoblasts

AbstractIn‐vitro models are fundamental for studying muscular cell contractility and for wide‐screening of therapeutic candidates targeting skeletal muscle diseases, owing to their scalability, reproducibility, and circumvention of ethical concerns. However, in‐vitro assays permitting reliable electrical stimulation of cell contractile activity still require technological development. Here, a novel approach to electrically stimulate differentiated muscular cell contractility is reported exploiting the ionic conductivity and mechanical flexibility of 3D nanofibrous scaffolds. The electrospun poly(L‐lactide‐co‐caprolactone) scaffold allowed for C2C12 murine myoblasts horizontal elongation and myotubes formation. Scaffold porosity enables high ionic conductivity and strong electric field generation, orthogonally oriented to the scaffold surface. Electrically induced cell contractility is determined with atomic force microscopy (AFM) enabling real‐time monitoring of scaffold vibrations in liquid environment. Differentiated cell actuation is found to be linearly correlated to current amplitude and number of current stimuli. Integrating the 3D nanofibrous scaffolds with real‐time AFM monitoring provides highly accurate in‐vitro assays for biomedical research. The induction of electric fields orthogonal to the scaffold surface allows for accurately mimicking the excitation‐contraction coupling mechanism observed in native skeletal muscle tissue. This work paves the way for the quantitative study of muscular cell dynamic behavior and physiology, further evaluating therapy effectiveness for muscular pathologies.

Polyether‐Derived Carbon Material and Ionic Liquid (Tributylmethylphosphonium iodide) Incorporated Poly(Vinylidene Fluoride‐co‐Hexafluoropropylene)‐Based Polymer Electrolyte for Supercapacitor Application

ABSTRACTPoly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP)‐sodium thiocyanate (NaSCN) solid polymer electrolytes containing different weight ratios of ionic liquid (IL)—tributylmethylphosphonium iodide (TBMPI) were prepared using solution‐cast approach. Electrochemical impedance data indicates that increasing ionic liquid into polymer electrolyte matrix increases ionic conductivity and the maximum value of ionic conductivity was obtained at 150 wt% TBMPI, having conductivity value of 8.3 × 10−5 S cm−1. The dielectric measurement supports our conductivity data. Ionic transference number measurement affirms this system to be predominantly ionic in nature, while electrochemical stability window (ESW) was found to be 3.4 V. Polarized optical microscopy (POM) along with differential scanning calorimetry (DSC) suggest suitability of TBMPI as plasticizer, while infrared spectroscopy (FTIR) confirms ion interaction, complexation, and composite nature. The thermogravimetric analysis (TGA) shows thermal stability of these ionic liquid‐doped polymer electrolytes (ILDPEs). Using maximum conducting ILDPE, a sandwiched supercapacitor has been fabricated which shows stable performance as high as 228 Fg−1 using cyclic voltammetry (CV).

Metal‐Organic Framework‐Derived Elastic Solid Polymer Electrolytes Enabled by Covalent Crosslinking for High‐Performance Lithium Metal Batteries

AbstractThe key issue in utilizing solid polymer electrolytes for high‐energy‐density lithium metal batteries is to balance the conflicting demands of superior processability, adequate ionic conductivity, and mechanical stability. Inspired by molecular structure design, a metal‐organic framework‐derived polyether poly(urethane urea) solid polymer electrolyte (denoted as ePU@H SPE) has been synthesized via a facile polycondensation method involving covalent crosslinking. The reduced crystallinity and numerous polar groups in ePU@H SPEs enhance Li salt dissociation and create efficient Li+ ion diffusion channels, yielding remarkable ionic conductivity (1.48 × 10−4 S cm−1). The polymer backbones, incorporating covalent bonds and dynamic hydrogen bonds, provide superb mechanical strength (5.12 GPa), high toughness (1240%), and excellent resilience, which suppress lithium dendrite growth and buffer electrode volume fluctuations during cycling. Leveraging these attributes, the well‐designed ePU@H SPE enables ultra‐high durability in lithium plating/stripping over 2300 h. Moreover, the integrated LFP|ePU@H|Li batteries, generating delicate electrode/electrolyte interfacial contact, deliver an exceptionally long lifespan (86% retention over 500 cycles at 1 C). Moreover, the LFP|ePU@H|Li pouch cell operates reliably even under severe deformation and external damage. Impressively, the stable cycling performance of full batteries incorporating high‐voltage LCO and high‐capacity S cathodes further verifies the significant potential of advanced ePU@H SPEs for practical applications.

Electrolyte Engineering to Construct Robust Interphase with High Ionic Conductivity for Wide Temperature Range Lithium Metal Batteries.

Unstable interphase formed in conventional carbonate-based electrolytes significantly hinders the widespread application of lithium metal batteries (LMBs) with high-capacity nickel-rich layered oxides (e.g., LiNi0.8Co0.1Mn0.1O2, NCM811) over a wide temperature range. To balance ion transport kinetics and interfacial stability over wide temperature range, herein a bifunctional electrolyte (EAFP) tailoring the electrode/electrolyte interphase with 1,3-propanesultone as an additive was developed. The resulting cathode-electrolyte interphase with an inorganic inner layer and an organic outer layer possesses high mechanical stability and flexibility, alleviating stress accumulation and maintaining the structural integrity of the NCM811 cathode. Meanwhile, the inorganic-rich solid electrolyte interphase inhibits electrolyte side reactions and facilitates fast Li+ transport. As a result, the Li||Li cells exhibit stable performance in extensive temperatures with low overpotentials, especially achieving a long lifespan of 1000 h at 30 °C. Furthermore, the optimized EAFP is also suitable for LiFePO4 and LiCO2 cathodes (1000 cycles, retention: 67 %). The Li||NCM811 and graphite||NCM811 pouch cells with lean electrolyte (g/Ah grade) operate stably, verifying the broad electrode compatibility of EAFP. Notably, the Li||NCM811 cells can operate in wide climate range from -40 °C to 60 °C. This work establishes new guidelines for the regulation of interphase by electrolytes in all-weather LMBs.

Bridging links between solid electrolytes and electrodes: Boosting the electrochemical performance of flame-retardant solid electrolytes with vapor-deposited carbon and gold-sputtered nanolayers

Solid electrolytes provide significant advantages such as high safety, minimal leakage, elevated energy density, and flexibility. However, challenges like sluggish ion transport (both in bulk and at interfaces), lithium dendrite formation, and suboptimal interface compatibility persist. This study delineates a strategy for enhancing composite solid electrolytes (CSE) through the sputtering and evaporation of an Au-C nanolayer, thereby augmenting interface contact and facilitating ion transport. The modified nanointerface layer ensures swift and homogeneous heat transfer at the interface, promoting uniform lithium-ion deposition and stripping and restrain lithium dendrite growth. The dual-network structure gel, synthesized by blending carrageenan and polyethylene oxide, imparts exceptional flexibility and thermal stability to the CSE. The obtained polymer solid electrolyte exhibits high ionic conductivity (2.48 × 10-4 S cm−1), an ion transference number of 0.76, and puncture strength of 6 MPa. It also demonstrates excellent thermal stability, withstanding 100 °C for 24 h and resisting ignition for 120 s when exposed to an open flame. Surface modifications Au-C nanolayers decrease interfacial resistance by 200 % and enhance thermal conductivity by 20 %. Non-destructive X-CT analysis and COMSOL-Multiphysics thermal simulations were utilized to investigate the function of modified nanolayers and composite structure. This innovative surface nanolayers modification, combined with advanced testing and analysis, promising strategies for the scalable application of solid electrolytes.

Anisotropic hydrogel sensors with muscle-like structures based on high-absorbent alginate fibers

Hydrogel sensors have attracted much attention as they play a critical role in health monitoring, multifunctional electronic skin, and human-machine interfaces. However, the isotropic structure makes existing hydrogel sensors exhibit isotropic sensing performance. Therefore, it is a challenge to fabricate hydrogels with human tissue-like structures to achieve anisotropic sensing performance. Herein, we proposed a novel method to prepare anisotropic hydrogel sensors using high-absorbent alginate fibers. The anisotropic hydrogel, HAFG@CNTs, was prepared by adsorbing carbon nanotubes on high-absorbent alginate fibers and immobilized using polyacrylamide bonds. The hydrogel had anisotropic mechanical properties and anisotropic ionic conductivity. The modulus and toughness in the parallel fiber direction were 2.31 and 3.75 times higher than those in the perpendicular fiber direction, respectively, and the sensitivity of the parallel fiber direction was higher than that of the vertical direction when strain occurred. In addition, machine learning algorithms were used to predict and classify different action signals obtained from HAFG@CNTs with an accuracy of up to 98.18 %. These advantages offer great potential for applying HAFG@CNTs to wearable devices and medical monitoring.

A high-performance flexible biopolymer-based Ce oxide composite electrolyte for lithium-ion battery dendrite reduction

We propose a novel solid-state composite polymer electrolyte (CPE) that includes Li7La2.5Ce0.5Zr2O12 (Ce-LLZO), chitosan (CS)/agar-agar (AA) polymer, polyethylene glycol (PEG) plasticizer, and LiClO4 salt. At 25 °C, the CPE3 formulation, consisting of 15 wt% Ce-LLZO, 60 wt% CS-AA, 15 wt% PEG, and 10 wt% LiClO4, demonstrated exceptional lithium (Li)-ion conductivity of 5.18 × 10-3 S cm−1 and an optimal transference number (TLi+) of 0.937. We assessed the electrochemical stability of CPE3 using linear sweep voltammetry, which revealed a maximum stability limit of 4.1 V (versus Li/Li+). In addition, the coin cell made with the Li||CPE3||NMC configuration had an amazing discharge capacity of 163 mAhg-1 and stayed stable for up to 100 cycles at 0.1 °C in room temperature. Conversely, when subjected to Li-plating/stripping cycles, the symmetric Li||CPE3||Li cell exhibited stability for 550 h and maintained a current density of 2.0 mA cm−2. Compared to Li-metal, the proposed material exhibited reduced overpotential while simultaneously enhancing electrochemical stability.

High Configuration Entropy Promises Electrochemical Stability of Chloride Electrolytes for High‐Energy, Long‐Life All‐Solid‐State Batteries

AbstractSolid‐state electrolytes (SSEs) with high ionic conductivity, stability, and interface compatibility are indispensable for high‐energy‐density and long‐life all‐solid‐state batteries (ASSBs), yet there are scarce SSEs with sufficient ionic conductivity and electrochemical stability. In this study, with a high‐entropy SSE (HE‐SSE, Li2.9In0.75Zr0.1Sc0.05Er0.05Y0.05Cl6), we show the high configuration entropy has a thermodynamically positive relationship with the high‐voltage stability. As a result, the ASSBs with HE‐SSE and high‐voltage cathode materials exhibit superior high‐voltage and long‐cycle stability, achieving 250 cycles with 81.4 % capacity retention when charged to 4.8 V (vs. Li+/Li), and even 5000 cycles if charged to 4.6 V (vs. Li+/Li). Experimental characterizations and density functional theory calculations confirm that the HE‐SSE greatly suppresses the high‐voltage degradation of SSE at the interface, promoting the high‐voltage stability coordinately through high entropy and interface stability. The high entropy design offers a general strategy to simultaneously improve the high‐voltage stability and ionic conductivity of SSEs, creating an avenue to building high‐energy and long‐life ASSBs.