Promising Solid-state Electrolyte Research Articles

Quasi-Solid-State Na-O2 Battery with Composite Polymer Electrolyte.

Na-O2 batteries have emerged as promising candidates due to their high theoretical energy density (1,601 Wh kg-1), the potential for high energy storage efficiency, and the abundance of sodium in the earth's crust. Considering the safety issue, quasi-solid-state composite polymer electrolytes are among the promising solid-state electrolyte candidates. Their higher mechanical toughness provides superior resistance to dendritic penetration compared with traditional liquid electrolytes. The flexibility of the composite polymer electrolyte matrix allows it to conform to various battery configurations and considerably reduces safety concerns related to the combustion risks associated with conventional liquid electrolytes. In this study, we employed poly(ethylene oxide) (PEO) and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as the polymer matrix and sodium ion-conducting agent, respectively. We incorporated nanosized NZSP (25 wt %) to create the composite polymer electrolyte membrane. This CPE design facilitates ion conduction pathways through both sodium salt and NZSP. By utilizing a liquid electrolyte infiltration method, we successfully enhanced its ionic conductivity, achieving an ionic conductivity of 10-4 S cm-1 at room temperature.

In Situ Fabrication of High Ionic and Electronic Conductivity Interlayers Enabling Long-Life Garnet-Based Solid-State Lithium Batteries.

Garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is a promising solid-state electrolyte (SSE) because of its fast ionic conduction and notable chemical/electrochemical stability toward the lithium (Li) metal. However, poor interface wettability and large interface resistance between LLZTO and Li anode greatly restrict its practical applications. In this work, we develop an in situ chemical conversion strategy to construct a highly conductive Li2S@C layer on the surface of LLZTO, enabling improved interfacial wettability between LLZTO and the Li anode. The Li/Li2S@C-LLZTO-Li2S@C/Li symmetric cell has a low interface impedance of 78.5 Ω cm2, much lower than the 970 Ω cm2 of a Li/LLZTO/Li cell. Moreover, the Li/Li2S@C-LLZTO-Li2S@C/Li cell exhibits a high critical current density of 1.4 mA cm-2 and an ultralong stability of 3000 h at 0.1 mA cm-2. When used in a LiFePO4 battery, the Li/Li2S@C-LLZTO/LiFePO4 battery exhibits a high initial discharge capacity of 150.8 mA h g-1 at 0.2 C without lithium storage capacity attenuation during 200 cycles. This work provides a novel and feasible strategy to address interface issues of SSEs and achieve lithium-dendrite-free solid-state batteries.

AgF-PEO composite interfacial layer for electrolyte-free LAGP-based lithium metal batteries

NASICON-type LAGP solid state electrolyte has become one of the most promising solid-state electrolytes due to its superior performance such as favorable room-temperature ionic conductivity, high stability in air, wide electrochemically stable window, and low cost. The key constraint to the development of LAGP electrolyte is the LAGP/Li interface problem. In this paper, a composite interfacial layer (AgF@Li-PEO@LAGP) is introduced between LAGP electrolyte and electrode material. The LiF and Ag nanoparticles are generated on the Li surface by utilizing the substitution reaction to uniform lithium flux and prevent the side reaction, while the flexible PEO polymer buffer layer on the LAGP will improve the interface wettability. The Li/LAGP/Li symmetric cell modified with composite interfacial layer can maintain a low polarization voltage of 0.11 V at 0.1 mA cm−2 for stable cycling for more than 1200 h. The full cell also shows excellent cycling stability with the capacity retention of 93.6 % after 100 cycles. The composite interface layer can realize the elimination of liquid electrolyte and greatly reduce interface resistance. This broadens the road for the realization of all-solid-state batteries.

Influence of excess sodium and phosphorus on the ionic conductivity of NASICON-structured Na3Zr2(SiO4)2PO4 ceramic solid electrolyte

NASICON-structured Na3Zr2(SiO4)2PO4 (NZSP) is regarded as one of the most promising solid-state electrolytes (SSEs) for all-solid-state Na-ion batteries mainly due to its high thermal stability and wide electrochemical window. However, the existing NZSP tends to exhibit lower ionic conductivity at room temperature. Thus, in order to solve this issue, NaH2PO4 was chosen as a novel phosphate source for the synthesis of NZSP via solid-state reaction method. On top of that, excess sodium (Na) and phosphorus (P) were also added into parent NZSP SSE with different weight percentage ratios to investigate their effects on Na+ ion activation energy. Structural study reveals NZSP with either excess Na or P have the same crystal structure morphology but are dissimilar in terms of the presence of impurities and grain size. NZSP with the excess of Na shows the highest ionic conductivity (1.05 × 10−3 S cm−1) and electrode polarization contributed by the increasing of Na+ carriers and the excess Na+ ion vacancies. These results authenticate that the excess of Na can be an effective way to improve the performance of NZSP SSE for energy storage application.

Solid-state synthesis and ion transport characteristics of the β-KSbF4 for all-solid-state fluoride-ion batteries

All-solid-state fluoride ion batteries (FIBs) have been recently considered as a post-lithium-ion battery system due to their high safety and high energy density. Just like all solid-state lithium batteries, the key to the development of FIBs lies in room-temperature electrolytes with high ionic conductivity. β-KSbF4 is a kind of promising solid-state electrolyte for FIBs owing to its rational ionic conductivity and relatively wide electrochemical stability window at room temperature. However, the previous synthesis routes of β-KSbF4 required the use of highly toxic hydrofluoric acid and the ionic conductivity of as-prepared product needs to be further improved. Herein, the β-KSbF4 sample with an ionic conductivity of 1.04 × 10−4 S cm−1 (30 °C) is synthesized through the simple solid-state route. In order to account for the high ionic conductivity of the as-synthesized β-KSbF4, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) are used to characterize the physicochemical properties. The results show that the as-synthesized β-KSbF4 exhibits higher carrier concentration of 1.0 × 10−6 S cm−1 Hz−1 K and hopping frequency of 1.31 × 106 Hz at 30 °C due to the formation of the fluorine vacancies. Meanwhile, the hopping frequency shows the same trend as the changes of ionic conductivity with the changes of temperature, while the carrier concentration is found to be almost constant. The two different trends indicate the hopping frequency is mainly responsible for the ionic conduction behavior within β-KSbF4. Furthermore, the all-solid-state FIBs, in which Ag and Pb + PbF2 are adopted as cathode and anode, and β-KSbF4 as fluoride ion conductor, are capable of reversible charge and discharge. The assembled FIBs show a discharge capacity of 108.4 mA h g−1 at 1st cycle and 74.2 mA h g−1 at 50th cycle. Based on an examination of the capacity decay mechanism, it has been found that deterioration of the electrolyte/electrode interface is an important reason for hindering the commercial application of FIBs. Hence, the in-depth comprehension of the ion transport characteristics in β-KSbF4 and the interpretation of the capacity fading mechanism will be conducive to promoting development of high-performance FIBs.

Effect of Li6.4La3Zr1.4Ta0.6O12 Fillers on the Interfacial Properties between Composite PEO-LiTFSI Electrolytes with Li Metal during Cycling.

PEO-LiX solid polymer electrolyte (SPE) with the addition of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) fillers is considered as a promising solid-state electrolyte for solid-state Li-ion batteries. However, the developments of the SPE have caused additional challenges, such as poor contact interface and SPE/Li interface stability during cycling, which always lead to potentially catastrophic battery failure. The main problem is that the real impact of LLZTO fillers on the interfacial properties between SPE and Li metal is still unclear. Herein, we combined the electrochemical measurement and in situ synchrotron-based X-ray absorption near-edge structure (XANES) imaging technology to study the role of LLZTO fillers in directing SPE/Li interface electrochemical performance. In situ XRF-XANES mapping during cycling showed that addition of an appropriate amount of LLZTO fillers (50 wt %) can improve the interfacial contact and stability between SPE and Li metal without reacting with the PEO and Li salts. Additionally, it also demonstrated the beneficial effect of LLZTO particles for suppressing the interface reactions between the Li metal and PEO-LiTFSI SPE and further inhibiting Li-metal dendrite growth. The Li|LiFePO4 batteries deliver long cycling for over 700 cycles with a low-capacity fade rate of 0.08% per cycle at a rate of 0.3C, revealing tremendous potential in promoting the large-scale application of future solid-state Li-ion batteries.

Design of multicomponent argyrodite based on a mixed oxidation state as promising solid-state electrolyte using moment tensor potentials

Design of multicomponent argyrodite based on the mixed oxidation state as promising solid-state electrolytes using moment tensor potentials.

Phase Evolution and Thermodynamics of Al-Doped Cubic LLZO Studied by High-Temperature X-Ray Diffraction

Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte for advanced Li-ion batteries due to its high ionic conductivity, non-flammability and high electrochemical stability against Li anodes and high voltage cathodes. However, synthesis of phase pure LLZO is challenging due to easy formation of secondary phases, such as the pyrochlore La2Zr2O7, that are detrimental to the performance of a LLZO electrolyte. Although many studies have been performed on the electrochemical performance of LLZO, the understanding of the thermodynamics of the synthesis of LLZO is still lacking.Here we report on high-temperature X-ray diffraction (HTXRD) following the crystallization of a gel of Al-doped LLZO. Gels with 0, 10 and 20 mol% excess Li were prepared and calcined at 500 °C to remove the volatile components before HTXRD. The powders calcined at 500 °C consisted primarily of La2Zr2O7 with trace amounts of Li2CO3 and La2O2CO3 and were used as starting materials to study the formation of the cubic LLZO phase. During HTXRD the samples were heated from 500 °C to 700 °C in steps of 20 °C, and further to 1000 °C in steps of 50 °C. Upon heating the pyrochlore phase gradually transforms to cubic LLZO. In all samples, cubic LLZO first appears around 600 °C and the pyrochlore phase disappears around 750 °C in the samples with 0 % and 20 % excess Li. We performed two analyses of the sample with 10 % excess Li by HTXRD, one with normal deposition thickness (Figure a) and another with thinner deposition thickness (Figure b), see attached Figures. In the thin sample, cubic LLZO appears at a lower temperature of 560 °C compared to the other experiments. The pyrochlore phase does not fully disappear but instead reappears and crystallizes at the highest temperatures investigated, indicating extensive Li loss from the thin sample. These observations suggest that atmospheric exposure and the relative surface area of powder are important factors for LLZO formation.To understand the thermodynamics of LLZO formation, we propose the following reaction to take place based on the identified reactants and products:6.25 Li2CO3 + 0.25 Al2O3 + 2 La2Zr2O7 + La2O2CO3 → 2 Li6.25−xAl0.25La3Zr2O12−0.5x + 7.25 CO2(g) + x Li2O(g).The enthalpy, entropy and Gibbs energy of the reaction were calculated from literature values and DFT calculations and agree with the experimental observations. Finally, we discuss the significance of the highly disordered Li sublattice for the entropy of cubic LLZO. We believe our findings will contribute to improved understanding of LLZO formation and facilitate the synthesis of high-performance phase pure LLZO electrolytes.Figure captions:HTXRD patterns of powder with 10 % Li excess from 500 to 1000 °C. (a) Normal deposition thickness. (b) Deposited as a thin layer on the Pt strip. The red asterisk and green square denote La2Zr2O7 and La2O3 (PDF no. 04-005-6788) impurity phases, respectively. The blue triangle denotes a Pt peak, visible due to the thin deposition. The XRD patterns obtained at 30 °C after the HTXRD are shown at the top of the plots. Figure 1

A Lithium Intrusion-Blocking Interfacial Shield for Wide-Pressure-Range Solid-State Lithium Metal Batteries.

Lithium garnets are considered as promising solid-state electrolytes for next-generation solid-state Li metal batteries (SSLBs). However, the Li intrusion driven by external stack pressure triggers premature of Li metal batteries. Herein, for the first time, an in situ constructed interfacial shield is reported to efficiently inhibit the pressure-induced Li intrusion in SSLBs. Theoretical modeling and experimental investigations reveal that high-hardness metallic Mo nanocrystals inside the shield effectively suppress Li dendrite growth without alloy hardening-derived interfacial contact deterioration. Meanwhile the electrically insulated Li2 S as a shield component considerably promotes interfacial wettability and hinders Li dendrite penetration into the bulk of garnet electrolyte. Interfacial shield-protected Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO)-based cells exhibit significantly enhanced cyclability without short circuits under conventional pressures of ≈0.2MPa and even at high pressure of up to 70MPa; which is the highest endurable stack pressure reported for SSLBs using garnet electrolytes. These key findings are expected to promote the wide-pressure-range applications of SSLBs.

The synergistic effects of dual substitution of Bi and Ce on ionic conductivity of Li7La3Zr2O12 solid electrolyte

Li7La3Zr2O12 (LLZO) is a promising solid-state electrolytes (SSE) candidate with high ionic conductivity, wide electrochemical window, good chemical stability and thermal stability. However, LLZO is unstable at room temperature and is easily converted from a cubic structure to a tetragonal structure, resulting in a decrease in ionic conductivity. Stable cubic phase LLZO can be obtained by element doping and the ionic conductivity can be improved. We found that the doping of Bi and Ce can reduce the sintering temperature and increase the ionic conductivity, among which the Li7La2.5Ce0.5Zr1.625Bi0.3O12 (LLCZBO) solid electrolyte has the highest ionic conductivity of 5.12 × 10−4 S cm−1 and the electronic conductivity of 2.72 × 10−10 at room temperature. LLCZBO prepared by sol-gel method can reduce the sintering temperature and improve the degree of densification. These results indicate that double-doped Bi and Ce is a simple and effective strategy to develop oxide solid electrolytes with high ionic conductivity.

In Situ Generated Electron-Blocking Lih Enabling An Unprecedented Critical Current Density of Over 15Ma Cm-2 for Solid-State Hydride Electrolytes.

LiBH4 is a promising solid-state electrolyte due to its thermodynamic stability to Li. However, poor Li-ion conductivities at room temperature, low oxidative stabilities and severe dendrite growth hamper its application. Herein, weadopted a partial dehydrogenation strategy to in situ generate an electronic blocking layer dispersed of LiH, addressing the above three issues simuteneously. The electrically insulated LiH reduces the electronic conductivity by two orders of magnitude, leading to a 32.0-times higher critical electrical bias for dendrite growth on the particle surfaces than that of the counterpart. Additionally, this layer not only promotes the Li-ion conductance by stimulating coordinated rotations of BH4 - and B12 H12 2- , contributing to a Li-ion conductivity of 1.38 × 10-3 S cm-1 at 25 °C, but also greatly enhances oxidation stability by localizing the electron density on BH4 - , extending its voltage window to 6.0V. Consequently, this electrolyte exhibits an unprecedented critical current density of 15.12mA cm-2 at 25 °C, long-term Li plating and stripping stability for 2700h, and a wide temperature window for dendrite inhibition from -30 to 150 °C. Its Li-LiCoO2 cell displayed high reversibility within 3.0 to 5.0V. We believe this work provides a clear direction for solid-state hydride electrolytes. This article is protected by copyright. All rights reserved.

Optimization of Annealing Process of Li6PS5Cl for All-Solid-State Lithium Batteries by Box–Behnken Design

Li6PS5Cl possesses high ionic conductivity and excellent interfacial stability to electrodes and is known as a promising solid-state electrolyte material for all-solid-state batteries (ASSBs). However, the optimal annealing process of Li6PS5Cl has not been studied systematically. Here, a Box–Behnken design is used to investigate the interactions of the heating rate, annealing temperature, and duration of annealing process for Li6PS5Cl to optimize the ionic conductivity. The response surface methodology with regression analysis is employed for simulating the data obtained, and the optimized parameters are verified in practice. As a consequence, Li6PS5Cl delivers a rather high conductivity of 4.45 mS/cm at 25 °C, and ASSB consisting of a LiNi0.6Co0.2Mn0.2O2 cathode and lithium anode shows a high initial discharge capacity of 151.7 mAh/g as well as excellent cycling performances for more than 350 cycles, highlighting the importance of the design of experiments.

Quasi-In Situ XPS Insights into the Surface Chemistry of Garnet-Type Li6.4La3Zr1.4Ta0.6O12 Solid-State Electrolytes: The Overlooked Impact of Pretreatments and a Direct Observation of the Formation of LiOH.

Garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is a highly promising solid-state lithium metal battery electrolyte due to its exceptional ionic conductivity and electrochemical stability. However, when exposed to air, a passivation layer can be spontaneously formed on the garnet-type electrolyte, deteriorating its wettability with metallic lithium (Li) and impeding the lithium ion transfer at the Li-garnet electrolyte interface. The passivation layer is considered a critical issue for garnet-type solid electrolytes. Despite intensive research, the formation mechanism of the passivation film remains poorly understood. The key to elucidating the formation mechanism is to obtain a pristine garnet electrolyte surface and study how the pristine garnet electrolyte interacts with air. In this study, different passivation layer removal pretreatments were performed to expose pristine garnet electrolytes, and their impacts on the samples were systematically studied. The results reveal the overlooked negative impacts of vacuum annealing and acid treatment on LLZTO, which are indicated by the severe loss of Li and O and the formation of additional Li-depleted metal oxides. It was confirmed that argon annealing is the only viable approach to remove the passivation layer without introducing concomitant contaminations to LLZTO. Based on this method, we directly evidenced the formation of LiOH on LLZTO under rarefied air using quasi-in situ X-ray photoelectron spectroscopy. It was confirmed that the loss of Li and O ions, rather than Li+/H+ exchange, drives the formation of LiOH in the passivation layer. These results not only provide a better understanding of the surface and interface chemistry of LLZTO but also reveal a reliable surface treatment for the LLZTO sample.

Al Doped into Si/P Sites of Na3Zr2Si2PO12 with Conducted Na3PO4 Impurities for Enhanced Ionic Conductivity.

Natrium superionic conductor (NASICON) is a promising solid-state electrolyte because of its high stability under air as well as its safety. Doping is an effective way to improve its ionic conductivity, but there is limited information about the explanation of the doping sites. In this work, Al-doped NASICONs are designed. When Al doping is 0.3 (NAl0.3ZSP), the ionic conductivity is the highest and is 5.08 × 10-5 S cm-1 at 30 °C, which is 3.3 times that of undoped NASICON. NAl0.3ZSP consists of a NASICON structure (monoclinic and rhombohedral phases), an amorphous glassy phase, and Na3PO4 impurities. After Al doping, more Si/P sites are occupied by Al; thus, the ratio of Na3PO4 impurities increases. Na3PO4 at the grain boundary is beneficial for grain boundary resistance decrease, contributing to the decrease of the total resistance. Our work first provides a detailed explanation of doped-Al sites and interprets their effects on ionic conductivity.

Highly conductive thin lamellar Li7La3Zr2O12/Li3InCl6 composite inorganic solid electrolyte for high-performance all-solid-state lithium battery

Garnet-type oxide Li7La3Zr2O12 (LLZO) has attracted considerable attention as promising solid-state electrolyte (SSE) owing to the exceptional bulk ion conduction. However, the Li+ transfer capacity of most LLZO-based solid electrolytes remains inadequate, primarily due to the presence of extensive grain boundaries and excessive thickness. Herein, we report the fabrication of a LLZO-based lamellar composite inorganic solid electrolyte (LLZO/LIC LISE) by in-situ sintering Li3InCl6 (LIC) in LLZO lamellar framework. LIC can act as an effective Li+-conductive grain boundary modifier within the electrolyte, leading to a remarkable reduction in grain boundary resistance of LLZO/LIC LISE (<9.2 Ω cm2), which is much lower than that of LLZO lamellar framework (827.2 Ω cm2). Together with the reduced internal grain boundary of LLZO nanosheet, a high ionic conductivity of 3.22 × 10−4 S cm−1 at 25 °C is obtained for LLZO/LIC LISE. In addition, combining with the thin thickness of 29 μm, LLZO/LIC LISE obtains high ionic conductance of 223 mS and exceptional energy density of 246 Wh kg−1, surpassing most developed SSEs. As a result, the cell assembled with LLZO/LIC LISE achieves superior cycling performance of 144.2 mAh g−1 after 200 cycles at 0.5C with a capacity decay of only 0.055% per cycle. This study may present a facile approach to effectively eliminate the grain boundary resistance of inorganic solid electrolytes toward high-performance all-solid-state lithium batteries.

Interface characteristics of Li1+xAlxTi2-x(PO4)3 solid electrolyte with Ta-doping for All-Solid-State batteries

Li1+xAlxTi2-x(PO4)3 (LATP) is a promising solid-state electrolyte, but it introduces stability issues because Ti reduces when it comes into contact with Li metal. Here, Ta doping was performed on the LATP electrolyte to confirm its influence on Ti reduction. Further, the crystal structure and ionic conductivity were analyzed to optimize the amount of Ta. We also used electron energy loss spectroscopy to visually demonstrate that Ta doping mitigated the reduction of Ti, which was confirmed by the presence of a mixed Ti4+/Ti3+ peak in the energy loss spectrum. Moreover, the applicability of Ta-doped LATP was confirmed in all-solid-state batteries, which showed a high coulombic efficiency and capacity of 98.6% and 0.072 mAh cm-2, respectively. These findings suggest a possible way to improve the chemical stability of LATP.

Air Stabilization of Li7P3S11 Solid-State Electrolytes through Laser-Based Processing.

All-solid-state batteries (ASSBs) that employ solid-state electrolytes (SSEs) have the potential to replace more conventional batteries that employ liquid electrolytes due to their inherent safety, compatibility with lithium metal and reputable ionic conductivity. Li7P3S11 is a promising SSE with reported ionic conductivities in the order of 10 mS/cm. However, its susceptibility to degradation through oxidation and hydrolysis limits its commercial viability. In this work, we demonstrate a laser-based processing method for SSEs to improve humidity stability. It was determined that laser power and scanning speed greatly affect surface morphology, as well as the resulting chemical composition of Li7P3S11 samples. Electrochemical impedance spectroscopy revealed that laser treatment can produce SSEs with higher ionic conductivities than pristine counterparts after air exposure. Further examination of chemical composition revealed an optimal laser processing condition that reduces the rate of P2S74- degradation. This work demonstrates the ability of laser-based processing to be used to improve the stability of SSEs.

A porous garnet Li7La3Zr2O12 scaffold with interfacial modification for enhancing ionic conductivity in PEO-based composite electrolyte

The composite combined Li7La3Zr2O12 (LLZO) and PEO is viewed as a promising solid-state electrolyte for lithium-ion batteries due to its chemical stability, wide electrochemical window, mechanical flexibility and easy fabrication procedure. However, the primary challenges of low ionic conductivity and poor interfacial compatibility remain unresolved. Herein, a co-modified composite solid-state electrolyte based on the porous Al-doped LLZO (Al-LLZO) garnet scaffold cooperated with Ca-coordinated Dynasylan IMEO (Triethoxy-3-(2-imidazolin-1-yl) propylsilane, named DI) and PEO (denoted as CSE-DI-Ca) is reported. Benefiting from the fast lithium ion conduction in porous Al-LLZO network and interfacial strengthening modification between ceramics and polymer, CSE-DI-Ca exhibits a high ionic conductivity of 6.38✕10−4 S cm−1 at room temperature. The unique ceramic structure of CSE-DI-Ca also leads to an enlarged electrochemical window of 6 V vs. Li+/Li, good thermal stability under 360 °C, and an improved mechanical strength of 8.91 MPa to block lithium dendrites. Furthermore, as an evidence of the compatibility with high-voltage battery, the LiNi0.6Co0.2Mn0.2O2(NCM622)|CSE-DI-Ca|Li coin cell delivers an initial discharge capacity of 130.2 mAh g−1 at 0.1 C at room temperature and maintains a capacity of 127.3 mAh g−1 after 120 cycles. All these superior properties indicate that the as-prepared composite holds great promise as an effective solid-state electrolyte to be used in next-generation lithium-ion batteries.

High-Efficiency Lithium-Ion Transport in a Porous Coordination Chain-Based Hydrogen-Bonded Framework

Fast and selective Li+ transport in solid plays a key role for the development of high-performance solid-state electrolytes (SSEs) of lithium metal batteries. Porous compounds with tunable Li+ transport pathways are promising SSEs, but the comprehensive performances in terms of Li+ transport kinetics, electrochemical stability window, and interfacial compatibility are difficult to be achieved simultaneously. Herein, we report a porous coordination chain-based hydrogen-bonded framework (NKU-1000) containing arrayed electronegative sites for Li+ transport, exhibiting a superior Li+ conductivity of 1.13 × 10-3 S cm-1, a high Li+ transfer number of 0.87, and a wide electrochemical window of 5.0 V. The assembled solid-state battery with NKU-1000-based SSE shows a high discharge capacity with 94.4% retention after 500 cycles and can work over a wide temperature range without formation of lithium dendrites, which derives from the linear hopping sites that promote a uniformly high-rate Li+ flux and the flexible structure that can buffer the structural variation during Li+ transport.

A novel flame-retardant nitrile-based gel polymer electrolyte for quasi-solid-state lithium metal batteries

In this work, a novel type of highly Li+-ions conductive, nonflammable adiponitrile (ADN)-based gel polymer electrolyte (denoted as AT11-GF) was prepared as a promising solid-state electrolyte for lithium (Li)-metal batteries by in-situ polymerization method. In order to overcome the parasitic reactions of ADN and triethyl phosphate (TEP) on Li-anode surface, fluoroethylene carbonate (FEC) was utilized as film-forming agent to generate LiF-enrich interface in this system of ADN-based electrolyte. The as-prepared electrolyte exhibited high ionic conductivity of 1.724 × 10−3 S/cm at ambient temperature, wide electrochemical window (∼5.75 V vs. Li+/Li), favorable Li+-ion transfer number (tLi+=0.70), and superior interfacial compatibility with Li anode (ultra-stable at a current density of 0.2 mA/cm2 for 1000 h). The LiFePO4|AT11-GF|Li battery presented an excellent rate capacity of 116.9 mAh/g at 2.0 C, and long-term cycling performance with a specific capacity of 134.6 mAh/g and a capacity retention of 94.5% after 1000 cycles at a current density of 1.0 C. Therefore, this as-prepared ADN-based electrolyte exhibited great promise for the application in solid-state Li-metal batteries.