Lithium phosphorus sulfur halide / polymer composite electrolytes and methods of making thereof

Abstract

This disclosure provides systems, methods, and apparatus related to lithium phosphorus sulfur halide / polymer composite electrolytes. In one aspect, a method includes ball milling a lithium phosphorus sulfur halide (Li6PS5X), with X being one or more halides. The Li6PS5X has an argyrodite-type crystal structure. The Li6PS5X is mixed with a polymer and a solvent. The solvent is evaporated to form an electrolyte. The electrolyte is cured.

Description

Lithium phosphorus sulfur halide / polymer composite electrolytes and methods of making thereofInventors: Gao Liu, Faiz Ahmed, Xiuyu JinRELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 553,211, filed 14 February 2024, which is hereby incorporated by reference.STATEMENT OF GOVERNMENT SUPPORT

[0002] This invention was made with government support under Contract No. DE-AC02- 05CH11231 awarded by the U.S. Department of Energy. The government has certain rights in this invention.BACKGROUND

[0003] Research is focused on all-solid-state lithium-ion batteries (ASSLBs) with solid electrolytes (SEs), owing to their qualities such as high energy, high power density, and enhanced safety compared to conventional lithium-ion batteries (LIBs). Despite the numerous advantages of ASSLBs, many of issues still need to be addressed before commercialization. Typically, solid electrolytes demonstrate lower ionic conductivity (o) compared to liquid electrolytes. For instance, lithium phosphorous oxynitride (LiPON), a frequently employed solid electrolyte, exhibits an ionic conductivity (o) on the order of 10'6S / cm. In contrast, a liquid electrolyte like lithium hexafluorophosphate in ethylene carbonate and propylene carbonate demonstrates a higher o on the order of IO2S / cm at room temperature.

[0004] Extensive research has been conducted on solid electrolytes to address their limitations. Various approaches have been explored, including organic polymer electrolytes, inorganic ceramic electrolytes, and inorganic-organic composite electrolytes. However, many polymer electrolytes face challenges with modest room temperature o due to their high degree of crystallinity and low Li-ion transference number. Poly (ethylene glycol) diacrylate (PEGDA), poly (ethylene oxide) (PEO), polydopamine (PDA), polyacrylonitrile (PAN), and poly(vinylidene fluoride) (PVDF) polymers exhibit low-temperature o, worse antioxidation, and poor mechanical characteristics. Further, oxide-based inorganic solid electrolytes, such asLiPON, garnetsLii.3Alo.3Tii.7(P04)3 (LATP), LivLinZnOn (LLZO), and Lao.57Lio.29Ti03 (LLTO), have shown improved conductivity (ranging from 10!to IO- S / cm). Nonetheless, they are sensitive to moisture, prone to reduction during charge-discharge cycles, react with Li-metal, and tend to be brittle.

[0005] However, researchers have turned to sulfide-based solid electrolytes as an alternative to oxides. Sulfide-based solid electrolytes exhibit good room temperature G (about 2.5 x IO2S / cm), which equals or surpasses that of most liquid electrolytes. Investigations into sulfide- based solid electrolyte systems, including glasses, glass ceramics, and crystalline conductors, have opened up a research field on solid electrolytes. However, certain sulfide-based solid electrolytes such as LiGePiSn and LiSnP Si? exhibit a strong reactivity with Li-metal, leading to the formation of dendrites at the interfaces. This reactivity results in the decomposition of the solid electrolytes. To address this issue and mitigate side reactions between the electrolyte and Li-metal, a solution involving using Li-alloy and buffer layers between the sulfide-based solid electrolytes and Li-metal has been studied. Unfortunately, this approach comes with a significant drawback as it dramatically reduces the energy density of the cells due to the low working voltage. Alternatively, sulfide-based solid electrolytes like LiPSX (X= halides), Li3PS4, and LiP.S n have also been explored, and they display a reactivity with Li-metal, forming an ionicconductivity interface layer. This layer can serve as a solid-electrolyte interface (SEI) layer, effectively suppressing side reactions and creating a smooth pathway for Li+movement.Consequently, these types of sulfide-based solid electrolytes present promising options for the development of high-energy-density SSBs.

[0006] Among the various sulfide-based solid electrolytes, argyrodite LiePSsCl (LPSC1) stands out as an attractive option due to its excellent o (about 1 ,33x 103S / cm at room temperature) and low cost. Consequently, extensive research has been conducted on LPSC1 electrolytes, yielding promising results for their applications in Li-ion and Li-S batteries. However, a significant challenge in using argyrodite LPSC1 in ASSLBs applications is the interface instability between the LPSC1 and electrodes. During charge-discharge cycling, LPSC1 tends to oxidize, leading to the production of elemental sulfur, polysulfides, phosphates, and lithium chloride at the electrode interface. These side products ultimately hinder cycling stability and can result in dendrite formation at the interface. Another important drawback of LPSC1 is its non-negligible electronic conductivity, which allows for smooth electron transport through theLPSC1 electrolyte. Consequently, lithium dendrites can be directly deposited at the grain boundaries of LPSC1 particles, leading to a self-discharge issue.

[0007] Recently, there has been significant use of polyethylene oxide) (PEO) and its derivatives-based polymers in conjunction with LPSC1 to develop composite electrolytes aiming to enhance electrochemical performance, mechanical strength, and interfacial stability. One research group reported a composite electrolyte composed of PEO, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and LPSC1, which exhibited high G and excellent interfacial stability against Li-metal. By preventing direct contact between LPSC1 and Li metal, the prepared cell demonstrated favorable Li plating-stripping ability at a current density of 0.2 mA / cm2at 60 °C. Another research group improved cell performance by modifying PEO, showing that a substituted terminal group of poly(ethylene glycol) not only stabilized inner interfaces but also extended the electrochemical window of the composite electrolyte.

[0008] Despite the advantages of the aforementioned PEO-based composite electrolytes, they are not yet suitable for practical applications due to their low G at room temperature and dendrite formation at high current density. Addressing these challenges, researchers recently prepared composite electrolytes using only polymer and LPSC1 electrolytes without the addition of any salts. Poly(p-phenylene oxide) (PPO), polyethylene glycol) dimethyl ether (PEGDME), and PVDF were used as the polymer matrix. It was observed that after adding the polymer to the LPSC1 electrolyte, the voids and gaps among the LPSC1 particles were filled. The polymer formed a protective layer on the LPSC1 particles, reducing electronic conductivity through the LPSC1 particle, ultimately suppressing dendrite formation in the grain boundary, and protecting LPSC1 from moisture. As a result, the cycling performance and capacity retention of the cell with polymer / LPSCl composite electrolyte significantly increased. The engineering of polymer / LPSCl composite electrolytes represents a promising strategy to develop dendrite and self-discharge-free, as well as humidity-stable, ASSLBs.SUMMARY

[0009] Described herein are polymer / LPSCl composite electrolytes for application in ASSLBs. In some embodiments, the synthesis process involves utilizing TEGDMA monomer and LPSC1 ceramic as precursor materials, which are then subjected to in-situ polymerization. One goal was to enhance the interfacial interaction between the solid electrolyte and theelectrodes. Additionally, the effect of ball-milling on the particle size and morphology of LPSC1 was investigated to determine its effects on the performance of the material.

[0010] The resulting composite electrolytes exhibited several advantageous properties, including reduced sensitivity to air, exceptional <5, and diminished electronic conductivity. To assess Li plating-striping performance, Li-Li symmetric cells were employed. Notably, the Li- Li symmetric cell employing the composite electrolyte demonstrated stable cycling for a remarkable duration of over 1000 hours (375 cycles) at a current density of 0.4 mA / cm2.

[0011] One innovative aspect of the subject matter described in this disclosure can be implemented in a method including ball milling a lithium phosphorus sulfur halide (LiePSsX), with X being one or more halides. The LiePSsX has an argyrodite-type crystal structure. The LiePSsX is mixed with a polymer and a solvent. The solvent is evaporated to form an electrolyte. The electrolyte is cured.

[0012] Details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figures 1A-1C show FTIR spectra of (Figure 1A) TEGDMA monomer and TEGDMA Polymer (Figures IB and 1C) ALPSC1, BLPSC1, ALPSC1-P, and BLPSC1-P electrolytes. Figures ID- IK show S 2p (Figures 1D-1G) and P 2p (Figures 1H-1K) XPS spectra of prepared solid electrolytes.

[0014] Figure 2A shows TGA analysis and Figure 2B shows DSC analysis of prepared electrolytes. Figures 2C-2G show SEM images of (Figure 2C) ALPSC1 and (Figure 2D) BLPSC1 electrolytes. Figures 2E-2G show cross-sectional SEM images and Figures 2H-2J show EDS and elemental mapping of BLPSC1-P composite electrolyte.

[0015] Figure 3A shows ionic conductivity and Figure 3B shows electronic conductivity of the prepared solid electrolytes at 25 °C. Figure 3C shows a schematic diagram of the challenges of a LPSC1 electrolyte. Figure 3D shows a schematic diagram of the impact of polymer on a composite electrolyte. Figure 3E shows the ionic conductivity vs temperature curves of theprepared solid electrolytes. Figure 3F show the ln(ionic conductivity) vs the inverse of absolute temperatures.

[0016] Figure 4A shows the overpotential vs. current density curves and Figures 4B show Li plating-striping curves at 0.5 mA / cm2current density for ALPSC1 and BLPSC1 electrolytes.Figures 4C-4E show Li plating-striping curves at 0.4 mA / cm2current density for ALPSC1 and BLPSC1 electrolytes. Figure 4F shows Li plating-striping curves at 0.4 mA / cm2current density for ALPSC1-P and BLPSC1-P electrolytes.

[0017] Figure 5A shows charge-discharge plots of the as-prepared electrolyte solutions based on the coated NMC811 / / solid electrolyte / / Li-In cell at 0.1C rate. Figure 5B shows specific discharge capacity plots of the cells as a function of the charge-discharge cycles at 0.1C. Figure 5C shows coulombic efficiency of the cells with as-prepared solid electrolytes as a function of the charge-discharge cycles.

[0018] Figure 6 shows an example of a flow diagram illustrating a fabrication process for a lithium phosphorus sulfur halide / polymer composite electrolyte.

[0019] Figure 7 shows an example of a schematic diagram of the preparation and in-situ polymerization of a polymer / ceramic composite electrolyte.DETAILED DESCRIPTION

[0020] Reference will now be made in detail to some specific examples of the invention including the best modes contemplated by the inventors for carrying out the invention. Examples of these specific embodiments are illustrated in the accompanying drawings. While the invention is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0021] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. Particular example embodiments of the present invention may be implemented without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.

[0022] Various techniques and mechanisms of the present invention will sometimes be described in singular form for clarity. However, it should be noted that some embodiments include multiple iterations of a technique or multiple instantiations of a mechanism unless noted otherwise.

[0023] The terms “about” or “approximate” and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range can be ± 20%, ± 15%, + 10%, ± 5%, or ± 1%. The terms “substantially” and the like are used to indicate that a value is close to a targeted value, where close can mean, for example, the value is within 80% of the targeted value, within 85% of the targeted value, within 90% of the targeted value, within 95% of the targeted value, or within 99% of the targeted value.

[0024] Figure 6 shows an example of a flow diagram illustrating a fabrication process for a lithium phosphorus sulfur halide / polymer composite electrolyte. Figure 7 shows an example of a schematic diagram of the preparation and in-situ polymerization of a polymer / ceramic composite electrolyte.

[0025] Starting at block 605 of the process 600 shown in Figure 6, a lithium phosphorus sulfur halide (LiePSsX) is ball milled. The X in the LiePSsX is one or more halides. The LiePSsX also has an argyrodite-type crystal structure. In some embodiments, the lithium phosphorus sulfur halide (LiePSsX) is ball milled at about 77 Kelvin or lower. In some embodiments, liquid nitrogen is used to cool the LiePSsX during the ball milling operation. In some embodiments, after the ball milling, the LiePSsX has a particle size of about 2 microns to 5 microns. In some embodiments, techniques other than ball milling are used to reduce the particle size of the LiePSsX.

[0026] In some embodiments, X is a halide from a group chlorine, bromine, iodine, and combinations thereof. In some embodiments, X is chlorine. In some embodiments, after the ball milling, the LiePSsX has a particle size of about 2 microns to 5 microns.

[0027] At block 610, the LiePSsX is mixed with a polymer and a solvent. In some embodiments, the polymer is a polymer from a group triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and ethylene glycol dimethacrylate. In some embodiments, the polymer is one of the polymers in the previous sentence that includes an acrylate instead of methacrylate as polymerization group (e.g., triethylene glycol acrylate, diethylene glycol diacrylate, ethylene glycol diacrylate). In some embodiments, the polymer is a polymer from agroup triethylene glycol dimethacrylate, triethylene glycol acrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, and ethylene glycol diacrylate. In some embodiments, the polymer includes alkyls from one methylene unit up to about 1000 methylene units instead of ethyleneoxide units. In some embodiments, the polymer is or comprises triethylene glycol dimethacrylate. In some embodiments, the solvent is or comprises toluene.

[0028] In some embodiments, the mixing includes mixing the LiePSsX with the polymer, the solvent, and a radical initiator. In some embodiments, the radical initiator comprises an organic- radical initiator. In some embodiments, the radical initiator is a radical initiator from a group azibisisbutyronitrile and l,l'-azobis(cyclohexanecarbonitrile). In some embodiments, the radical initiator is or comprises azibisisbutyronitrile.

[0029] At block 615, the solvent evaporated to form an electrolyte.

[0030] At block 620, the electrolyte is cured. Curing the electrolyte polymerizes the polymer, in part. In some embodiments, curing the electrolyte fully cross-links the polymer. In some embodiments, curing the electrolyte includes compressing the electrolyte at a temperature above about room temperature for about 1 hour to 20 hours. Room temperature is generally taken to be about 20 °C to 25 °C. In some embodiments, the temperature above room temperature is about 50 °C to 300 °C, about 50 °C to 250 °C, about 50 °C to 200 °C, about 60 °C to 100 °C, or about 80 °C. In some embodiments, the electrolyte is compressed while exposing the electrolyte to the temperature above about room temperature for about 5 hours to 7 hours.

[0031] In some embodiments, curing the electrolyte includes compressing the electrolyte while exposing the electrolyte to ultraviolet (UV) light for about 1 hour to 20 hours. In some embodiments, the electrolyte is compressed while exposing the electrolyte to UV light for about 5 hours to 7 hours.

[0032] In some embodiments, during the compressing operation, an anode is disposed on a first side of the electrolyte and a cathode is disposed on a second side of the electrolyte. With such an arrangement, the electrolyte may be cured in situ during battery fabrication.

[0033] In some embodiments, the process 600 may be used to fabricate a cathode (e.g., a cathode of an all solid-state battery). For example, in some embodiments, the process 600 further includes mixing the electrolyte and particles of a lithium nickel manganese cobalt oxide to form a cathode composite material. In some embodiments, the particles of the lithium nickelmanganese cobalt oxide are coated with lithium niobium oxide. In some embodiments, the mixing further comprises mixing the electrolyte, the particles of the lithium nickel manganese cobalt oxide, and carbon fiber. In some embodiments, the process 600 further comprises prior to mixing the electrolyte and the particles of the lithium nickel manganese cobalt oxide, grinding the electrolyte.

[0034] In some embodiments, during the compressing operation, a lithium indium sheet is disposed on a surface of the cathode composite material opposite a surface of the cathode disposed on the second side of the electrolyte during the compressing operation.

[0035] The material generated with the process 600 shown in Figure 6 comprises particles of a lithium phosphorus sulfur halide (LiePSsX), with X being one or more halides, the LiePSsX having an argyrodite-type crystal structure. The particles are in or embedded in a polymer matrix.

[0036] In some embodiments, X is a halide from a group chlorine, bromine, iodine, and combinations thereof. In some embodiments, X is chlorine.

[0037] In some embodiments, a size of the particles is about 2 microns to 5 microns.

[0038] In some embodiments, the polymer is a polymer from a group triethylene glycol dimethacrylate, triethylene glycol acrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, and ethylene glycol diacrylate. In some embodiments, the polymer comprises triethylene glycol dimethacrylate.

[0039] In some embodiments, the material further comprises particles of a lithium nickel manganese cobalt oxide disposed in the polymer matrix.

[0040] The following examples are intended to be examples of the embodiments disclosed herein, and are not intended to be limiting.EXAMPLE - Preparation of polymer / ceramic composite electrolyte, composite cathode, and SSBs cells

[0041] To prepare a composite electrolyte made of polymer and ceramic, TEGDMA, toluene, AIBN, and LPSC1 were mixed. First, 0.25 g of TEGDMA and toluene (10 wt%) in a small vial were mixed and stirred for 10 minutes until the solution became uniform. Then, 1 g of LPSC1 was added to the solution and stirred for 4 hours to evenly distribute the particles. After that, AIBN (1 wt% of TEGDMA) was added to the solution and stirred for 30 minutes. The resulting solution was poured onto a polyethylene terephthalate (PET) sheet to allow the tolueneto evaporate. Once the toluene was evaporated, the product was placed in a polyetheretherketone (PEEK) die sleeve and applied 348 MPa pressure. The product was then heated at 80 °C for 4 hours to complete the polymerization process. The whole experiment was conducted inside an Ar-filled glove box. In addition, to prepare ball-milled LPSC1, the as-received LPSC1 was placed in a ZrOi container, along with a ZrOi ball, and subjected to mechanical milling using a planetary ball milling apparatus at a speed of 500 r.p.m. for a duration of 30 minutes. The prepared four electrolytes are denoted as follows: as-received LPSC1 (ALPSC1), ball-milled LPSC1 (BLPSC1), as-received LPSC1-TEGDMA polymer (ALPSC1-P), ball-milled LPSC1- TEGDMA polymer (BLPSC1-P).

[0042] For the assembly and electrochemical measurements of Li-Li symmetric cells, electrolyte weighing 0.2 g was compressed at about 348 MPa using a PEEK die sleeve to form a pellet. Subsequently, two pieces of Li metal foil with a diameter of 10 mm were placed on either side of the electrolyte pellet and pressed with a pressure of about 50 MPa, and heated at 80 °C for 4 hours to complete the polymerization process (for composite electrolytes). Li platingstripping experiments were conducted at 25 °C under 50 MPa applied pressure. The current density was 0.4-0.5 mA / cm2.

[0043] To prepare the cathode composite, coated NMC811 and LPSC1 electrolyte were taken with the weight ratio of 80:20 in mortar inside the glove box. 2 wt% of vapor-grown carbon fiber was added and mixed properly using a pestle. For Li-coated NMC811 full cell testing, 0.2 g of electrolyte was pressed into a pellet with a pressure of about 348 MPa. Next, the cathode composite material was evenly distributed on the surface of the electrolyte plate and pressed under a pressure of about 348 MPa. A Li-In (3:7 wt%) foil was then pressed onto the opposite side of the electrolyte and applied about 50 MPa pressure. The mass loading of the cathode composite material was approximately 12 mg. The pellet was sandwiched between two stainless-steel rods and heated at 80 °C for 4 hours to complete the polymerization process. All these processes were carried out inside an Ar-filled glove box. The galvanostatic chargedischarge tests were conducted at 25 °C under a 50 MPa applied pressure. The operating voltage range was from 2.4 to 4.2 V (vs. Li+ / Li).EXAMPLE - Characterizations of prepared electrolytes

[0044] The cross-linked polymer cannot dissolve in commonly used NMR solvents such as CDCh, DMSO-dd, C4D8O, or D2O. Hence, FTIR spectroscopy was employed to analyze thestructure of the LPSC1, TEGDMA monomer, and cross-linked TEGDMA polymer. Figures 1A- 1C illustrate the FTIR spectra of ALPSC1, BLPSC1, TEGDMA monomer, TEGDMA polymer, ALPSC1-P, and BLPSC1-P, respectively. In the FTIR spectrum of the TEGDMA monomer (Figure 1A), characteristic bands are observed at 3000-2850 cm (C-H stretching),(C-C stretching), 1724 cm (C=O stretching), 1465-1375 cm1(C-H bending I'or -CH - and - CH3), 1340-850 cm1(COC stretching), and 650-1000 cm (C-H out-of-plane bend).However, upon polymerization of the TEGDMA monomer, only the C=C peaks disappear completely (Figure 1A), while the other peaks remain unchanged. This indicates the successful polymerization of TEGDMA. In Figure IB, ALPSC1, BLPSC1, ALPSC1-P, and BLPSC1-P exhibit a characteristic FTIR band of PS4 ’1at 546The C-C band is diminished in the FTIR spectrum of ALPSC1-P, and BLPSC1-P (Figure 1C), indicating that LPSC1 does not hinder the polymerization of the TEGDMA monomer.

[0045] The chemical states of the surface functional groups of the prepared solid electrolytes were analyzed using XPS analysis. The corresponding deconvoluted S 2p and P 2p spectra for ALPSC1, BLPSC1, ALPSC1-P, and BLPSC1-P electrolytes are shown in Figures 1D-1K. In the TEGDMA polymer XPS spectra, there were no S 2p and P 2p spectra that appeared. The S 2p and P 2p signals are split into two components due to spin-orbit coupling. Meanwhile, in the deconvoluted XPS spectra of the S 2p and P 2p levels in ALPSC1 and BLPSC1 electrolytes, clear peaks were identified at ca. (162.07 and 163.18) eV for S 2pa / 2 and S 2pi / 2, and at ca. (132.38 and 133.28) eV for P 2p3 / 2 and P 2pi / 2, respectively. The observed peaks of P and S elements were associated with the PS43system. For ALPSC1 and BLPSC1 electrolytes, a second weak component at ca. 168.38 eV was detected in the S 2p spectra. This finding can be explained by traces of the sulfite environment (SO32) on the surface, probably due to contact with traces of oxygen. On the other hand, in the XPS spectra of ALPSC1-P and BLPSC1-P composite electrolytes, this peak was not present, suggesting that the polymer can protect the LPSC1 particles from moisture and form a less air-sensitive electrolyte. Further, the positions and intensities of the S 2p and P 2p peaks in ALPSC1-P and BLPSC1-P composite electrolytes exhibited slight changes, possibly attributable to the inclusion of polymer in the LPSC1 ceramics. EXAMPLE - Physiochemical properties and morphological analyses of as-prepared electrolytes

[0046] Thermal stability analysis was conducted on the LPSC1 ceramic, cross-linked TEGDMA polymer, ALPSC1-P, and BLPSC1-P electrolytes, as indicated in Figure 2A. BothALPSC1 and BLPSC1 ceramics displayed minimal weight loss of approximately 1.42% up to 658 °C and showed high thermal stability up to 800 °C, which is due to the high crystallinity of the ceramics. On the other hand, the cross-linked TEGDMA polymer exhibited an initial weight loss of around 70% within the temperature range of 105-336 °C, which could be attributed to the partial decomposition and carbonization of the polymer. Subsequently, a second weight loss of 97% was observed in the temperature range of 337-440 °C, resulting from the complete decomposition of the polymer. Additionally, both composite membranes, namely the ALPSC1-P and the BLPSC1-P, displayed a two-step weight loss of about 25% in the temperature range of 219-658 °C. This weight loss can be attributed to the decomposition of the polymer within the composite electrolytes, indicating the presence of 25 wt% TEGDMA polymer in the composite electrolytes. However, the thermal stability of both composite electrolytes was lower than that of the LPSC1 ceramic but higher than most conventional liquid electrolytes. Therefore, the thermal stability of the as-prepared composite electrolytes is adequate for their practical application in LIB systems.

[0047] The Tg values of the as-prepared electrolytes were investigated by differential scanning calorimetry (DSC) analysis, as shown in Figure 2B. Both ALPSC1 and BLPSC1 electrolytes showed no obvious exothermic and endothermic behavior up to 200 °C, due to their high thermal stability and crystallinity. The Tg value2 of TEGDMA polymer and composite electrolytes were about 120 °C and 138 °C, respectively.

[0048] The surface morphology, EDS, and elemental analysis of the as-prepared electrolytes were investigated, as depicted in Figures 2C-2J). The ceramic electrolyte plays a crucial role in the preparation of highly conductive composite electrolytes. The SEM images illustrate that the BLPSC1 ceramic, after ball milling, exhibits reduced aggregation and particle size compared to the ALPSC1 electrolyte (Figures 2C and 2D). SEM images of the composite electrolytes, ALPSC1-P and BLPSC1-P, reveal the incorporation of LPSC1 particles, which are enveloped by the polymer matrix.

[0049] Following the in-situ polymerization of TEGDMA, the morphology of the LPSC1 particles undergoes minimal change, gradually becoming coated by the TEGDMA polymer. This polymer filling within the grain boundaries of the LPSC1 particles ensures smooth Li+transport and electronic insulation at these boundaries. Moreover, the LPSC1 ceramic is evenly dispersed throughout the polymer matrix in the BLPSC1-P composite electrolyte, devoid of anyaggregation (Figure 2F). Notably, this uniform distribution of the LPSC1 ceramic and polymer facilitates easy movement of Li+in the BLPSC1-P composite electrolyte. Cross-sectional images, elemental mapping, and EDS analysis of the BLPSC1-P composite electrolyte are presented in Figures 2E-2J. It is evident that the TEGDMA polymer forms a layer enveloping the entire LPSC1 particle in the composite electrolyte. This polymer layer can obstruct electronic conduction through the grain boundaries of the LPSC1 particles, ultimately safeguarding the solid-state cell from severe self-discharge and dendrite formation.EXAMPLE - Ionic conductivity, and electronic conductivity of as-prepared electrolytes

[0050] To evaluate o of the electrolytes, SS / / electrolyte / / SS type symmetric cells were prepared under pressure and an AC impedance measurement technique at the temperature range of (-20 to 70) °C was used. The O value of ALPSC1 was about 1 .086x 10 ’1S / cm at 25 °C (Figure 3A). The o increased after ball-milling, reaching the value of about 1 . 187x 103S / cm for BLPSC1 at 25 °C (Figure 3A), due to the changes in crystallinity, particle size, and aggregation. However, the o value of ALPSC1-P and BLPSC1-P composite electrolytes were about 1 ,65x 104and 2.2 lx 104S / cm at 25 °C (Figure 3A), respectively, which are higher or comparable to those of other conventional polymer / ceramic composite electrolytes (see Table 1).

[0051] Figure 3B shows the electronic conductivity of the prepared solid electrolytes at 25 °C. The electronic conductivities of the solid electrolytes, including ALPSC1, BLPSC1, ALPSC1- P, and BLPSC1-P, were about 4.45xl0~9, 4.54xl0~9, 3.70xl0~10and 3.92x 1010S / cm, respectively, at 25 °C. The non-negligible electronic conductivities of LPSC1 electrolytes lead to smooth electron transport through the LPSC1 pellets, resulting in Li-dendrites depositing directly at the grain boundaries and causing self-discharge (Figure 3C). However, polymer / LPSCl composite solid electrolytes suppress the dendrite growth by reducing electronic conductivity. By incorporating polymer into ALPSC1 ceramic, the reduction in o and electronic conductivity for ALPSC1-P was 84.86% and 91.69%, respectively. Similarly, for BLPSC1-P, the reductions were 81.72% for o and 91.35% for electronic conductivity. These results suggest that the polymer has a greater impact on reducing electronic conductivity compared to 0 in the composite electrolytes. The polymer / ceramic composite electrolyte can transport the Li+smoothly while blocking the electron transport at the grain boundary, which helps suppress self-discharge and enhances cycling stability (Figure 3D). More importantly, the polymer covered on the surface ofLPSC1 functions as a protection layer to separate the LPSC1 and moisture, which improves humidity stability.Table 1. Comparison of the Li+conductivities at 25 °C of some reported solid composite electrolytes with the prepared composite electrolytes.PEGDME = polyethylene glycol dimethyl ether, NBR = nitrile butadiene rubber, PEGDMA= Polyethylene glycol) dimethacrylate, LiSTFSI = Lithium 4-styrenesulfonyl- (trifluoromethylsulfonyl)imide, LiCGC = Lithium-ion-conducting glass ceramic powder, PL@LCSE=PEO + Ta-doped garnet Li6.4La3Zn.4Tao.6O12 + Lithium 4-styrenesulfonyl- (trifluoromethylsulfonyl)imide, LATP@PEGDA = Lii.3Alo.3Tii.7(P04)3 particles + poly(ethylene glycol) diacrylate.

[0052] The o values of ALPSC1 and BLPSC1 ceramics were about 5.99xl(T5and 6.04xl05S / cm at -20 °C. o gradually rose with increasing temperature (Figure 3E), reaching the value ofabout 7.57x10 ' and 7.87x10 ’’ S / cm at 70 °C. Accordingly, the o values of the composite electrolytes were about 8.34x 106S / cm and 8.36x106S / cm for ALPSC1-P and BLPSC1-P, respectively, at -20 °C (Figure 3A). While with increasing of temperature, both of the composite electrolytes exhibited higher o, ALPSC1-P and BLPSC1-P showed enhanced o values of about 1.37X10"3and 1 ,49x I03S / cm, respectively, at 70 °C (Figure 3E). Additionally, in order to investigate the temperature dependency of the electrolytes' G. a graph plotting the Inc against the reciprocal of absolute temperatures is shown in Figure 3F. This graph displayed a linear correlation between Inc and temperature, closely resembling the typical Arrhenius plot. This analysis yielded activation energy (Ea) values of approximately 0.21, 0.20, 0.25, and 0.23 eV for the ALPSC1, BLPSC1, ALPSC1-P, and BLPSC1-P electrolytes, respectively. The relatively low Ea values for these electrolytes are in line with the observed high G.EXAMPLE - Compatibility of as-prepared electrolytes with Li-metal

[0053] Figures 4A-4F illustrate the cycling stability of Li-metal symmetric cells using ALPSC1 and BLPSC1 ceramic electrolytes at 25 °C. Both cells, with ALPSC1 and BLPSC1 electrolytes showed different behavior at 0.5 mA / cm2current density (Figures 4A and B). Notably, the cell with ALPSC1 electrolyte displayed wedge-shaped voltage plateaus at a current density of 0.5 mA / cm2due to the increasing Li+transport resistance during lithium deposition, leading to uneven lithium plating (Figure 4A). This uneven plating / stripping, along with the solid-solid point contact and volume changes in the Li-metal anode, resulted in a continuous decrease in the effective contact area between the Li-metal anode and LPSC1 electrolyte. Consequently, the limited contact area contributed to higher local current density and exacerbated the uneven deposition of lithium metal, thereby promoting dendrite growth in the solid electrolyte. Conversely, the cell with BLPSC1 electrolyte exhibited a potential curve indicating uniform current distribution on the BLPSC1 electrolyte at a current density of 0.5 mA / cm2(Figure 4B).

[0054] Figures 4C-4E show the voltage-time profile of ALPSC1 and BLPSC1 electrolytes at 0.4 mA / cm2at 25 °C. The cells with ALPSC1 and BLPSC1 electrolytes exhibited low cycling stability up to 600 h (225 cycles) and this low cycling stability is responsible for the Li deposition in the bulk LPSC1, reduction of Li+at the grain boundaries of the LPSC1 electrolyte. However, compared to ALPSC1, the BLPSC1 electrolyte showed better, uniform, smooth, and dendrite-free Li-depo sition. The improved performance of the ball-milled electrolyte can beattributed to its distinct morphology, smaller particle size, and reduced aggregation compared to the ALPSC1 electrolyte.

[0055] The effect of a polymer on the suppression of Li dendrites was also investigated (Figure 4F). The cells containing polymer / ceramic electrolytes demonstrated improved Li plating / stripping cycling performance, allowing them to operate for up to 1000 hours (375 cycles) at 0.4 mA / cm2. However, the disparity in cycling stability between the composite electrolytes and LPSC1 electrolytes can be attributed to different Li deposition models. The grain boundary of the LPSC1 particle serves as a pathway for Li deposition, facilitating easy electron transfer between adjacent LPSC1 particles without any barriers. Consequently, continuous Li deposition and the growth of Li dendrites along the grain boundaries ultimately lead to a short circuit. In contrast, the incorporation of TEGDMA polymer in the LPSC1 ceramic electrolyte obstructs electron transport at the grain boundaries, resulting in suppressed Li dendrite growth in the bulk LPSC1 and improved cycle life for Li-Li symmetric cells. The TEGDMA polymer shields the grain boundary of the LPSC1 ceramics, impeding the movement of electrons between LPSC1 particles. However, the electrochemical performance of Li-Li symmetric cells with LPSCl / polymer composite electrolytes demonstrates excellent Li plating-stripping performance, surpassing or matching that of other SSBs. In addition, incorporating the polymer led to an increase in overpotential due to the reduced o, which can be detrimental to high-rate capability.

[0056] The cell resistance of the Li-Li symmetric cells with ALPSC1 and BLPSC1 electrolytes increased for the first few cycles and then stabilized, which can be attributed to the interfacial reactions between Li and LPSC1 and interphase formation. The corresponding EIS results during cycling of the ALPSC1-P and BLPSC1-P composite electrolyte confirmed the high stability and Li dendrite-free behavior. The slight increase in cell resistance during the first few cycles reflected the SEI formation process at the Li / SE interface, but the stabilized resistance after the first few cycles supported the stable Li plating / stripping behavior. Moreover, the cell utilizing BLPSC1-P composite electrolyte exhibited superior characteristics, such as lower over potential and smoother Li deposition behavior, compared to the ALPSC1-P composite electrolyte. These improvements can be attributed to the reduced particle size and altered morphology resulting from the ball milling of the LPSC1 electrolyte. These findings align well with the results obtained from o. electronic conductivity, XRD, XPS, and SEM analyses. Thedifferences in Li plating-stripping behavior with and without polymer further highlights the effect of the polymer on suppressing Li dendrite growth.EXAMPLE - Battery performances of as-prepared electrolytes

[0057] The battery performance of the prepared electrolytes was examined using an allsolid-state cell that had a coated NMC811 / electrolyte / Li-In configuration at a temperature of 25 °C. The choice of coated NMC811 as the cathode material was based on its high energy density, cycling performance, and theoretical capacity (180 mAh / g at 0.1 C). The cells' charge-discharge plots were measured by applying constant currents (0.1 C, 0.2 C, 0.3 C, and 0.5 C) across the potential range of 2.4 V to 4.2 V. The charge rate was determined using the weight of the active cathode material (12 mg). Figure 5A illustrates the charge-discharge plots of the cells at 0.1 C, up to a potential of 4.2 V, while Figures 5B and 5C depict the changes in discharge specific capacity (Csp) and Coulombic efficiency as the number of charge-discharge cycles increases at 0.1 C.

[0058] At a rate of 0.1 C, the Csp values of the solid-state cells with ALPSC1, BLPSC1, ALPSC1-P, and BLPSC1-P electrolytes were approximately 115 mAh / g, 125 mAh / g, 134 mAh / g, and 138 mAh / g, respectively (Figure 5A). These values are comparable to or higher than those reported for other solid electrolytes. EIS curves for the all- solid- state lithium cells prepared with four different SEs, both before cycling and after 50 cycles at 0.1C, show that the cell resistance for all four cells experienced a slight increase. This increase can be attributed to interfacial reactions between lithium and EPSC1, along with the formation of an interphase. Further, after 50 charge-discharge cycles, the FIB with these electrolytes exhibited Csp values of around 65 mAh / g, 73 mAh / g, 87 mAh / g, and 90 mAh / g for AEPSC1, BEPSC1, ALPSC1-P, and BEPSC1-P electrolytes, respectively, at 0.1 C. The capacity was decreased by approximately 44%, 42%, 37%, and 38% of the initial Csp (Figure 5B). Further, the BEPSC1-P electrolyte demonstrated excellent cycling and electrochemical stability, showing promise for the development of high-voltage all-solid-state LIBs. Additionally, the rate capability of the cells was investigated at various current densities from 0.1 C to 0.5 C. The cell with BEPSC1-P electrolyte delivered a capacity of over 59 mAh / g at a high current density of 0.5 C, and no short circuit was observed.

[0059] The Coulombic efficiencies of the cell using AEPSC1, BEPSC1, ALPSC1-P, and BLPSC1-P electrolytes were approximately 94.05%, 95.82 %, 99.85%, and 99.97%,respectively, during the first charge-discharge cycle (Figure 5C). These efficiencies improved to approximately 98.08%, 99.80%, 99.98%, and 99.99%, respectively, after 50 charge-discharge cycles, owing to the enhanced interfacial contact between the electrode and electrolyte. More importantly, both at the initial and following 50 cycles, the cells utilizing composite electrolytes, specifically ALPSCL-P and BLPSCL-P, demonstrated higher Coulombic efficiencies compared to cells employing individual ALPSC1 and BLPSCL electrolytes. Additionally, the fluctuation in Coulombic efficiency observed in cells with ALPSC1 and BLPSC1 electrolytes is higher than that in cells with ALPSC1-P and BLPSC1-P composite electrolytes. This phenomenon is common in solid-state batteries with LPSC1 electrolytes. These observations strongly suggest that the composite electrolytes exhibit substantial electrochemical stability and enduring cycling performance within the potential range of up to 4.2 V.CONCLUSION

[0060] Further details regarding the embodiments described herein can be found in F. Ahmed et al., “Argyrodite-LiePSsCl / Polymer-based Highly Conductive Composite Electrolyte for All-Solid-State Batteries,” ACS Appl. Energy Mater. 2024, 7, 5, 1842-1853, which is hereby incorporated by reference.

[0061] In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

Claims

CLAIMSWhat is claimed is:

1. A method comprising: ball milling a lithium phosphorus sulfur halide (LigPSsX), with X being one or more halides, the LigPSsX having an argyrodite-type crystal structure; mixing the LigPSsX with a polymer and a solvent; evaporating the solvent to form an electrolyte; and curing the electrolyte.

2. The method of claim 1, wherein the ball milling is performed at about 77 Kelvin or lower.

3. The method of claim 1, wherein the temperature above room temperature is about 50 °C to 300 °C.

4. The method of claim 1, wherein X is a halide from a group chlorine, bromine, iodine, and combinations thereof.

5. The method of claim 1, wherein after the ball milling, the LigPSsX has a particle size of about 2 microns to 5 microns.

6. The method of claim 1, wherein the polymer is a polymer from a group triethylene glycol dimethacrylate, triethylene glycol acrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, and ethylene glycol diacrylate.

7. The method of claim 1, wherein the solvent comprises toluene.

8. The method of claim 1, wherein during the compressing operation, an anode is disposed on a first side of the electrolyte and a cathode is disposed on a second side of the electrolyte.

9. The method of claim 1, wherein the mixing includes mixing the LigPSsX with the polymer, the solvent, and a radical initiator.10, The method of claim 9, wherein the radical initiator is a radical initiator from a group azibisisbutyronitrile and l,r-azobis(cyclohexanecarbonitrile).

11. The method of claim 1, the method further comprising: mixing the electrolyte and particles of a lithium nickel manganese cobalt oxide to form a cathode composite material.

12. The method of claim 11, wherein the particles of the lithium nickel manganese cobalt oxide are coated with lithium niobium oxide.

13. The method of claim 11, further comprising: prior to mixing the electrolyte and the particles of the lithium nickel manganese cobalt oxide, grinding the electrolyte.

14. The method of claim 11, wherein mixing the electrolyte and the particles of the lithium nickel manganese cobalt oxide further comprises mixing the electrolyte, the particles of the lithium nickel manganese cobalt oxide, and carbon fiber.

15. The method of claim 1, wherein curing the electrolyte includes compressing the electrolyte at a temperature above about room temperature for about 1 hour to 20 hours.

16. The method of claim 1, wherein curing the electrolyte includes compressing the electrolyte while exposing the electrolyte to UV light for about 1 hour to 20 hours17. A method comprising: ball milling lithium phosphorus sulfur chloride (LiePSsCl) at about 77 Kelvin or lower, the LiePSsCl having an argyrodite-type crystal structure; mixing the LiePSsCl with a polymer and a solvent; evaporating the solvent to form an electrolyte; and compressing the electrolyte at a temperature above about room temperature for about 1hour to 20 hours.

18. A material comprising: particles of a lithium phosphorus sulfur halide (LiePSsX), with X being one or more halides, the LiePSsX having an argyrodite-type crystal structure; and a polymer matrix, the particles being in the polymer matrix.

19. The material of claim 18, wherein X is a halide from a group chlorine, bromine, iodine, and combinations thereof.

20. The material of claim 18, wherein a size of the particles is about 2 microns to 5 microns.

21. The material of claim 18, wherein the polymer is a polymer from a group triethylene glycol dimethacrylate, triethylene glycol acrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, and ethylene glycol diacrylate.

22. The material of claim 18, further comprising: particles of a lithium nickel manganese cobalt oxide disposed in the polymer matrix.

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