Solid Electrolyte Films Research Articles

Functional multilayer solid electrolyte films for lithium dendrite suppression

The improvement of the interface between a lithium metal and a solid electrolyte layer is very important for the application of a lithium anode coated by solid electrolytes in lithium metal batteries. In order to address the issues of interface performance and compatibility between solid electrolyte films prepared by magnetron sputtering and lithium metals and the suppression of lithium dendrite during the cycling, a three-layer interface solid electrolyte film based on carbon-doped lithium phosphate oxynitride (LiCPON) was employed for coating a lithium metal. The sandwich structure of LiCPON by introducing an ultra-thin lithium niobium oxynitride (LiNbON) layer prepared by sputtering LiNbO3 in nitrogen ambient can be confirmed by time-of-flight secondary ion mass spectrometry. Atomic force microscopy data indicated that the surface of the LiCPON thin film with the sandwich structure is flatter and smoother than that of the LiCPON thin film on the lithium metal. The interface impedance of the symmetric battery based on the sandwich structure of the LiCPON coating lithium metal was reduced from 512.2 to 65.4 Ω, and the symmetric battery stable cycles from 300 h with an overpotential of more than 200 mV to 400 h with low overpotential of about 77 mV. These results suggest that functional multilayer solid electrolyte films become an effective method for protecting lithium. The incorporation of ultra-thin LiNbON into the LiCPON thin film could significantly decrease interface impedance between the lithium metal and solid electrolyte layer.

Long cycle life all-solid-state batteries enabled by solvent-free approach for sulfide solid electrolyte and cathode films

All-solid-state batteries have been considered as a promising energy storage system due to their high energy density and intrinsic safety. As the key component, sulfide solid electrolytes have attracted enormous attentions benefitting from the high ionic conductivity and small grain boundary resistance. However, fabricating ultrathin sulfide solid electrolyte film to achieve high energy density remains a challenge. Here, we report a strategy to obtain freestanding sulfide solid electrolyte film by hot rolled technology using PTFE and Li6PS5Cl powders. The obtained electrolyte film is 40 μm with a high ionic conductivity of 8.4 mS cm−1. Meanwhile, we prepared solvent-free cathode (LiNbO3@LiNi0.6Co0.2Mn0.2O2) film using the dry method technology. Herein, the all-solid-state batteries with the dry cathode and electrolyte films deliver a high discharge capacity of 120 mA h g−1 with excellent stability of 86.4 % after 1000 cycles at 1C and excellent rate performance (40 mA h g−1 at 4C) at room temperature. Furthermore, the pouch batteries show outstanding electrochemical performance, indicating potential commercial applications of sulfide-based solid-state batteries.

Melamine-Regulated Ceramic/Polymer Electrolyte Interface Promotes High Stability in Lithium-Metal Battery.

With the advantages of organic and inorganic solid electrolytes, composite electrolytes are a promising option for use in all-solid-state Li-metal batteries. However, the considerable disparity in interfacial energy between ceramic and polymer electrolytes results in poor solid-solid contacts and the internal creation of a space charge layer in the composite electrolyte. Here, we report a melamine (MA) transition layer for the sake of strengthening the bond between Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and poly(ethylene oxide) (PEO) to enhance physical and electrochemical properties. The MA is absorbed on LAGP by electron transfer from LAGP to MA's triazine ring, resulting in intimate contact and good mechanical stability. Simultaneously, the MA stabilizes the Li-salt anion, reduces its decomposition reactions at the interface between PEO and LAGP in the electrolyte, and promotes free Li+ dissociation, resulting in superior ionic conductivity and interfacial stability. Thus, the solid electrolyte film enables symmetric Li/Li batteries to achieve steady Li plating/stripping for more than 1300 h at a current density of 0.25 mA cm-2. The all-solid-state Li|PEO-MA@LAGP|LFP cell exhibits improved cycling stability. The Li/PEO-MA@LAGP/NCM523 cell shows a cycling life that is a factor of 5 times greater than that of a cell based on PEO-LAGP.

A high ionic conductive PDOL/LAGP composite solid electrolyte film for Interfacial Stable solid-state lithium batteries

High ionic conductivity for solid electrolyte and stable electrode/electrolyte interface have always been the main requirements for solid-state lithium batteries. Herein, a high ionic conductive composite solid electrolyte (CSE) film was prepared by combining 1.3-dioxolanes (DOL) capable of in-situ polymerization with high ionic conductive Li1.5Al0.5Ge1.5(PO4)3 (LAGP)ceramic fillers. The CSE film also shows high interface compatibility and stability with lithium metal. The optimized poly-DOL (PDOL)-30% LAGP CSE exhibits a desirable dense and uniform structure, which endows the CSE with a high ion conductivity of 4.63 × 10−4 S cm−1, a high ion migration number up to 0.73 and a wide electrochemical stability window of 5.1 V. The assembled high-voltage NCM622/PDOL-30%LAGP CSE/Li solid-state cell exhibits good rate and cycle performances with a capacity of 125 mAh/g at 2 C and a capacity retention of 76% at 0.5C after 400 cycles with an average Coulomb efficiency of 99.7%. The PDOL-30%LAGP CSE also possesses a high inhibition ability of lithium dendrites owing to the dense and uniform structure and the stable electrolyte/lithium electrode interface including Li–Ge, LiF and CF3 components. The Li/CSE/Li cell maintains a relatively stable voltage up to 650 h at a current density of 0.1 mA/cm2. This high ionic conductive composite solid electrolyte film shows a good application prospect in high-voltage solid-state lithium batteries.

A Three-Dimensionally Interconnected Composite Polymer Electrolyte for Solid-State Batteries

High energy density of solid-state batteries requires a thin solid electrolyte separator layer (<30 μm), that can sustain high currents and is easily processable. Polymer-ceramic composite electrolytes can potentially fulfill these requirements by combining the advantages of each type. Ceramic electrolytes have high room-temperature ionic conductivity, transference number of one, and mechanical strength to suppress lithium dendrites, whereas polymer electrolytes are easily processable and can form conformable interfaces with the electrodes. High interfacial-impedance between polymer and ceramic electrolytes make the composites with dispersed ceramic particles less attractive.1 A composite electrolyte architecture where a three-dimensionally interconnected porous ceramic is filled with polymer electrolyte, previously reported by our group, can avoid the interfacial impedance issue, although for thin composite membranes, the interfacial impedance between ceramic framework and excess polymer layer on top/bottom surface will still dominate the overall impedance.2 Here we will present fabrication and electrochemical evaluation of ~150 μm thick composite electrolytes with the above-described 3D-interconnected ceramic architecture. The 3-D framework is obtained by partially sintering Ohara ceramic particle tapes obtained via tape casting, which are filled with curable polymer electrolyte precursors. To obtain a thin (5 μm), uniform polymer electrolyte layer on both surfaces, spray coating was employed. The resulting composite membrane exhibited good dendritic resistance in symmetric cell cycling, improved transference number compared to the polymer electrolytes. We also found significantly improved flexibility of the composite electrolytes with plasticization, however, at the cost of reduction in ionic conductivity due to damage to the ceramic network caused by plasticizer-induced swelling of the cross-linked polymer electrolyte. This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office’s Advanced Battery Materials Research Program (Tien Duong, Program Manager). This abstract has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). References Chen, X. C.; Liu, X.; Samuthira Pandian, A.; Lou, K.; Delnick, F. M.; Dudney, N. J., Determining and Minimizing Resistance for Ion Transport at the Polymer/Ceramic Electrolyte Interface. ACS Energy Letters 2019, 4 (5), 1080-1085.Palmer, M. J.; Kalnaus, S.; Dixit, M. B.; Westover, A. S.; Hatzell, K. B.; Dudney, N. J.; Chen, X. C., A three-dimensional interconnected polymer/ceramic composite as a thin film solid electrolyte. Energy Storage Materials 2020, 26, 242-249.

Studies on structural and electrical properties of NaI doped PEO/CMC blend solid polymer electrolyte

Solid polymer blend electrolyte (SPE) films of Polyethylene oxide(PEO)/Carboxymethyl cellulose (NaCMC) doped with Sodium iodide (NaI), were prepared by solution cast method and their structural, optical and electrical properties were investigated using X-Ray diffraction, Fourier transform infrared spectroscopy, UV–Vis spectrophotometer and Electrical impedance analyser respectively. X-Ray diffraction spectra indicate that, deformation occurred in the structure of the blend followed by doping with NaI salt. The variation in intensity and shifting of characteristic bands in FTIR spectra provides the evidence for formation of complex due to the interaction occurred in the blend with the dopant. Optical energy band gap decreases in the blend samples upon doping and is confirmed by UV–Vis spectrophotometer analysis. Increase of dielectric constant and loss upon doping, exhibits usual behaviour of the polymer electrolytes. An increase in AC conductivity is observed upon doping and maximum conductivity of 9.41 × 10−3 Scm−1 is obtained for 10/90 sample doped with 0.03% Sodium iodide and DC conductivity for the same sample at room temperature is 1.05 × 10–2 Scm−1. In addition, I-T studies confirm the conductivity exhibited by the sample as due to ions and I-V studies show electrochemical stability in the range of good working potential. From the results obtained, it can be inferred that, the prepared sample can be used as polymer electrolytes in the manufacturing of energy storage devices.

Impedantiometric behavior of solid biopolymer electrolyte elaborated from cassava starch synthesized in different pH

This paper approaches the study of pH’s effect on elaborate films of solid biopolymer electrolyte from cassava starch and its impedantiometric response. The films of solid biopolymer electrolyte were elaborated by thermochemical synthesis while varying the pH (2, 4, 5, 7, 9, 10, and 12). Starch was extracted from cassava tubers by a traditional method (disintegrated, washed, decanted, filtered, and dried). Solid biopolymer electrolyte films were processed by thermochemical synthesis by adding plasticizers (glycerol, glutaraldehyde, and polyethylene glycol) and lithium salt (lithium perchlorate). The impedance behavior was studied using the electrochemical impedance spectroscopy technique. The Nyquist and Bode’s diagrams registered presented a similar trend in all the films; therefore, they were described by the same equivalent circuit model. However, the equivalent circuit components presented different values in each case. The conductivity and capacitance showed a quadratic polynomial tendency in relation to the pH, obtaining the highest conductivity in the films elaborated at acidic pH and the highest capacitance in the films elaborated at basic pH. The degree of basicity or acids allowed conductivity to be modulated or capacitance of the solid biopolymer electrolyte as required. It could be concluded that the production pH has a marked effect on impedantiometric behavior of films of solid biopolymer electrolyte from cassava starch, which may be useful to modulate the electrochemical properties of this type of material in future Applications.

Surface-reinforced NCM811 with enhanced electrochemical performance for Li-ion batteries

Effective and uniform surface modification is very important for improving the properties of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811). Here, we used a liquid-phase assisted method to modify the surface of NCM811 via ammonium metatungstate to synthesize 1 W@NCM811. This step reduced surface residual lithium and led to in situ WO 3 /Li 2 WO 4 coating. The uniform WO 3 /Li 2 WO 4 coating acted as an ideal protective layer and physically prevented direct contact between the NCM811 lattice and the electrolyte, thus stabilizing the cathode/electrolyte interface and passivating detrimental reactions. Moreover, the coating enhanced the electrochemical kinetics in terms of the impedance of Li + through a solid electrolyte film (R sf ) and charge transfer resistance (R ct ). The strong W-O bond can effectively improve the thermal stability of the material. As a result, the 1 W@NCM811-based cathode exhibits significantly enhanced structural stability, electrochemical performance, and thermodynamic properties. At 0.5 C (1 C = 200 mAh g −1 ) in the voltage range of 3.0–4.3 V, the 1 W@NCM811-based cathode delivers excellent capacity retention of 97.36% and 88.92% after 100 cycles at 25 °C and 55 °C, respectively. According to the analysis of 1 W@NCM811-based cathode, a better layered lattice, fewer by-products, and less heat generation prove that this approach provides an effective means for the development of NCM811. • A method is developed to resolve residual lithium and surface stability of Ni-rich layered cathode. • Ammonium metatungstate can significantly reduce the interfacial impedance of the material surface. • The strong W-O bond introduced can effectively improve the thermal stability of the material.

Fast Li+ migration in LiPON electrolytes doped by multi-valent Fe ions

Achieving superior ionic conductivity of LiPON solid electrolyte films is critical for the solid-state thin-film batteries with high energy density. Here we describe a method of preparing LiPON with promising ionic migration capability and high work function by systematically tailoring the concentration of Fe ions doping. Fe-doped LiPON exhibits excellent ionic conductivity (1.08 × 10−5 S cm−1, nearly 10 times higher than the pristine LiPON), low ionic activation energy, and moderate equilibrium potential difference (versus LiCoO2, 0.78 V) at room temperature. The favorable ionic mobility and electrochemical stability of Fe-doped LiPON are fully confirmed. All-solid-state “Li/LiPON/LiCoO2” TFB has been successfully constructed with a large specific capacity (∼36.3 µAh cm−2 µm−1 at 10 µA cm−2) and good cycle performance (87.8 % capacity retention after 40 cycles). Fe with the unique d-orbital electronic structure changes the local electron density of LiPON system with the weakened electrostatic constraint of PO3N4− tetrahedrons to Li+. A low Li+ migration barrier center is established around the Fe–N bridge bonds.

Understanding slurry formulations to guide solution-processing of solid electrolytes

Scalable processing of thin solid electrolytes is crucial for engineering solid-state batteries with practical energy densities. To leverage existing battery production infrastructure, pathways for solution processing of solid electrolyte films must be investigated. Roll-to-roll compatible film preparation of aluminum-doped lithium lanthanum zirconate oxide was studied. Four slurry configurations accounting for different solvent properties and solid loadings were evaluated to investigate the ternary interactions within the dispersions. Rheological and coating stability analyses were carried out on the processed slurries. The analysis and characterization indicated that improved component interactions within the ethanol/toluene system result in homogenized distribution of the particles, binder, and plasticizer, and enable the extraction of free-standing thin films with thicknesses of 20 μm and large area (>15 in.2). The drawbacks and opportunities of several protocols for high temperature sintering of the dried green films were investigated. This study highlights the importance of engineering dispersions during the development of processing protocols for solid electrolytes and provides guidelines for the best practices that can be leveraged for solution processing–based fabrications for a wide range of solid electrolyte materials.

Magnesium ion conducting free-standing biopolymer blend electrolyte films for electrochemical device application

Solid polymer blend electrolyte films composed of 70 wt.% of chitosan (CS) and 30 wt.% of methylcellulose (MC) were prepared with different weight percentages of MgCl2 by solution casting method. FTIR analysis demonstrated the interactions between blend and MgCl2, XRD study revealed the amorphous nature of the films. Thermogravimetric analysis (TGA) was carried out to study the thermal stability. Electrical impedance spectroscopy (EIS) study showed that the bulk resistance decreased with increasing salt concentration and is due to the influence of carrier concentration. From EIS measurement, the highest value of DC conductivity at ambient temperature (30 °C) was found to be 2.75 × 10−3 Scm−1 for the sample containing 30 wt.% of MgCl2. The voltage stability window of the highest conducting film was found to be 3.86 V. The total ionic transference number was found to be 0.98. Finally, the highest conducting polymer electrolyte was employed to construct a primary magnesium ion battery.

Boosting lithium-ion transport capability of LAGP/PPO composite solid electrolyte via component regulation from ‘Ceramics-in-Polymer’ to ‘Polymer-in-Ceramics'

The design and regulation of the ion transport channels in the polymer electrolyte is an important means to improve the lithium ion transport behavior of the electrolyte. In this work, we for the first time combined the high ionic conductive inorganic ceramic electrolyte Li1.5Al0.5Ge1.5(PO4)3 (LAGP) with flexible polypropylene oxide (PPO) polymer electrolyte to synthesize a high-filling LAGP/PPO composite solid electrolyte film and regulated the ion transport channels from ‘Ceramics-in-Polymer’ mode to ‘Polymer-in-Ceramics' mode by optimizing the ratio of LAGP vs. PPO. The results reveal that when the LAGP content <40%, the electrolyte belongs to ‘LAGP-in-PPO’, and then changes to ‘PPO-in-LAGP’ when the LAGP content exceeds 40%. Compared with ‘LAGP-in-PPO’, the ‘PPO-in-LAGP’ shows better comprehensive properties, especially for the 75% LAGP-filled PPO electrolyte, the room-temperature ionic conductivity is as high as 3.46 × 10−4 Scm−1, the ion migration number and voltage stable window reach 0.83 and 4.78 V respectively. This high-filled composite electrolyte possesses high tensile stress of 40 MPa with a strain of 46% and withstands working environment up to 200 °C. The NCM622/Li solid-state battery composed of this electrolyte also presents good rate and cycle performances with a capacity retention of 80% after 230 cycles at 0.3C because of its high ion transport capability and good inhibition of lithium dendrites. This composite structural design is expected to develop high-performance solid-state electrolytes suitable for high-voltage solid-state lithium batteries.

Highly conducting solid electrolyte films based on bivalent cations (Zn, Fe, and Ni)/oxidized PVA composites

Poly (viny1 alcohol) (PVA) is partially oxidized to form oxidized PVA (OPVA) that chelates efficiently with bivalents metals ion (zinc, iron, and nickel chlorides) composites. Fourier transform infrared spectroscopy (FT-IR) results and density-functional (DFT) theory suggest that the OPVA are formed by keto-enol tautomerism and not isolated ketone groups. X-ray diffractograms (XRD) of the composites showed an enhancement in the crystallinity that could be attributed to good chelation of OPVA with metals chlorides and the formation of a significantly high number of metal clusters following the process of chelation. The homogenous mixing morphology and good hydrophilic character were confirmed by scanning electron microscopy (SEM) and contact angle values, respectively. The incorporation of nickel or ferrous chlorides onto the OPVA matrix improved the electric and optical absorption properties better compared with zinc chloride. This suggested the highest level of chelation and successful preparation of a high conductive electrolyte film based on the OPVA matrix.

A thin free-standing composite solid electrolyte film for solid-state lithium metal batteries.

A thin free-standing composite solid electrolyte film (CSE, ∼15 μm) is prepared by a tape casting and solution infusion method, which owns a high ionic conductivity (2.76 × 10-4 S cm-1 at 25 °C) and a wide electrochemical stability window (4.8 V vs. Li+/Li). The CSE-based solid-state lithium metal batteries with the LiCoO2 cathode present good cycling stability and capacity retention with a 4.5 V cut-off voltage.

Fabrication of thin solid electrolytes containing a small volume of an Li3OCl-type antiperovskite phase by RF magnetron sputtering

RF magnetron sputter deposition was performed using an Li2O + LiCl powder target. The resulting solid electrolyte films were found to contain a small volume fraction of an Li3OCl-type antiperovskite phase.

Synthesis of Lithium Phosphorus Oxynitride (LiPON) Thin Films by Li3PO4 Anodic Evaporation in Nitrogen Plasma of a Low-Pressure Arc Discharge.

Thin amorphous films of LiPON solid electrolyte were prepared by anodic evaporation of lithium orthophosphate Li3PO4 in an arc discharge with a self-heating hollow cathode at a nitrogen pressure of 1 Pa. Distribution of the arc current between two electrodes having an anode potential provided independent control of the evaporation rate of Li3PO4 and the density of nitrogen plasma. Stabilization of the evaporation rate was achieved using a crucible with multi-aperture cover having floating potential. The existence of a threshold value of discharge current (40 A) has been established, which, upon reaching ionic conductivity over 10−8 S/cm, appears in the films. Probe diagnostics of discharge plasma were carried out. It has been shown that heating the films during deposition by plasma radiation to a temperature of 200 °C is not an impediment to achieving high ionic conductivity of the films. Dense uniform films of LiPON thickness 1 μm with ionic conductivity up to 1 × 10−6 S/cm at a deposition rate of 4 nm/min are obtained.

Preparation of free-standing Li3InCl6 solid electrolytes film with infiltration-method enable roll-to-roll manufacture

All-solid-state Li batteries (ASSLBs) have attracted more and more attention due to their potential energy density and safety benefits. For practical application, searching for a preparation method of solid-state electrolyte that is compatible with mature Li-ion-batteries technologies and enable scale-up production is important. In this work, an infiltration method is proposed for the preparation of Li3InCl6/glass-fiber solid composite electrolyte (LIC-SCE) film. Roll pressing method is adopted to obtain compact LIC-SCE with good mechanical strength, showing great promising to roll-to-roll manufacture platform. The LIC-SCE shows a high ionic conductivity of 5.4×10−4 S cm−1 at room temperature. Further, ASSLBs are successfully assembled with LiCoO2 (LCO) cathode.

Dynamics of changes in the kinetic parameters of germanium nanowires during lithiation/delithiation in a wide temperature range

• Electrochemical behavior of Ge nanowires in the temperature range from –40 to +20 o C is studied. • Formation of SEI on germanium nanowires was confirmed by IR spectra. • The activation energies of Rs, R SEI , and Rct are of 21.8, 24.1, and 36.5 kJ/mol, respectively. Electrochemical impedance spectroscopy was used to study electrochemical lithium insertion into the electrodes based on germanium nanowires in a temperature range of +20 to −40 °C. Since such electrodes have a regular structure and do not contain binders and conductive additives, they are described by a relatively simple equivalent circuit including the electrolyte resistance (R s ), the resistance of the solid electrolyte film (R SEI ) on the surface of germanium nanowires, the capacitance of the solid electrolyte film (C SEI ), the charge transfer resistance (R ct ), a constant phase element (CPE), reflecting the capacitance of the double layer, and the Warburg impedance (W), reflecting the diffusion of lithium in germanium. It is characteristic of the R SEI and R ct values to grow with an increase in the lithiation degree from 0.3 to 0.9, respectively, by 28% and 16%. A decrease in temperature leads to an increase in the values of R s, R SEI , and R ct in accordance with the Arrhenius law with activation energies of 21.8, 24.1, and 36.5 kJ/mol, respectively. At the same time, the SEI capacity is independent of temperature.

ELECTROCHEMICAL BEHAVIOR OF A COMPOSITE MATERIAL OF SOLID BIOPOLYMER ELECTROLYTE FROM CASSAVA STARCH / GRAPHENE OXIDE PREPARED AT DIFFERENT pH

Background: Composite materials make it possible to modulate the properties of the source materials and expand their technological potential. In this sense, composite materials made from solid biopolymeric electrolytes and graphene oxide can be an attractive alternative for applications in organic electronics due to their electrochemical properties. Aim: The present work aims to evaluate the electrochemical behavior of a composite material made of solid biopolymeric electrolyte of cassava starch and graphene oxide at different concentrations to determine the effect of this concentration and the pH used in the production process. Methods: The composite material was made from the use of cassava starch plasticized with glycerol, glutaraldehyde, polyethylene glycol and with lithium perchlorate as electrolytes. During the synthesis process, graphene oxide was added in different concentrations (0, 0.25, 0.50, 1.00, 1.25, 1.50, and 1.75 %w/w) to evaluate the effect of the concentration of this component. The synthesis was carried out by thermochemical method with constant heating in an oven at 75 ° C for 48 hours. Films were prepared using synthesis solutions at different pH (5.0 and 9.0). The pH was regulated by adding HCl or NaOH to the synthesis solution as appropriate. Results and Discussion: The results showed that the cassava starch biopolymeric solid electrolyte films without plasticizers were stiff and brittle, so they broke easily. The films with plasticizers and the films of the composite material were stable to the manual traction, allowing their easy manipulation without breaking. The films presented a similar electrochemical behavior in terms of oxide reduction processes; however, the films with graphene oxide presented signals with higher peak currents. Films made at pH 9.0 showed 50 % more intensity in peak currents. The addition of graphene oxide affected the current parameters and peak potentials, being more marked in the films prepared at pH 9.0; at this pH the films with concentrations of graphene oxide lower than 1.00 %w/w presented variable Ep and Ip, while at concentrations of graphene oxide greater than 1%w/w, the behavior did not show significant variations. Conclusions: The addition of graphene oxide modulates or modifies the electrochemical behavior of cassava starch biopolymeric solid electrolyte films, and the processing pH can vary the effect of the graphene oxide addition.

Cross-Linked Polypropylene Oxide Solid Electrolyte Film with Enhanced Mechanical, Thermal, and Electrochemical Properties via Additive Modification

Benefiting from the flexibility and low cost, polymer electrolytes are widely used in ultra-thin solid lithium-ion batteries. However, low room-temperature ion conductivity and poor mechanical and thermal stability are key defects hindering the wide application of the polymer solid-state electrolyte. In this work, a cross-linked polypropylene oxide (PPO) polymer solid electrolyte film with excellent mechanical, thermal and electrochemical properties was prepared by introducing the cellulose skeleton, polyglycol (peg400), and zirconia (ZrO2) additives. The cellulose skeleton and peg400 enhance the flexibility, tensile strength and thermal stability(>200 °C) of the electrolyte film, while ZrO2 promotes the movement of polymer segments and the dissociation of lithium salts to improve the ionic conductivity (6.67 × 10–4 S cm–1 at room temperature) and increase the potential window (>4.6 V vs Li/Li+) of the electrolyte. This composite electrolyte film can be used in LiFePO4(LFP) and LiNi0.6Co0.2Mn0.2 (NCM622) solid-state batteries and shows good cycling stability with 600 cycles for LFP. This rigid-flexible composite solid electrolyte film with high ion conductivity and good mechanical and thermal properties has good prospects for application in solid-state Li batteries.