Solid-state battery having electrodes with flexible polymer-salt interfacial layers

Abstract

Embodiments relate to an electrochemical cell. The electrochemical cell includes an electrolyte. The electrolyte includes a first electrolyte interface surface and a second electrolyte interface surface opposite the first electrolyte interface surface. The electrochemical cell also includes a cathode. The cathode includes a first cathode interface surface adjacent the first electrolyte interface surface and a second cathode interface surface opposite the first cathode interface surface. The electrochemical cell also includes an anode. The anode includes a first anode interface surface adjacent the second electrolyte interface surface and a second anode interface surface opposite the first anode interface surface. The electrochemical cell also includes a flexible polymer-salt interfacial layer disposed upon the first anode interface surface and / or the first cathode interface surface.

Description

Atty. Ref. No. 0073605-001156SOLTD-STATE BATTERY HAVING ELECTRODES WITH FLEXIBLE POLYMER- SALT INTERFACIAL LAYERSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is related to and claims the benefit of priority of U. S. Provisional Application 63 / 761,421, filed on February 21, 2025, the entire contents of which are incorporated by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Grant No. CBET-2134643 awarded by the National Science Foundation and under Grant No. W91 INF-23-2-0229 awarded by the U.S. Army / ARO. The Government has certain rights in the invention.FIELD OF THE INVENTION

[0003] Embodiments can relate to an electrochemical cell having electrodes having a flexible polymer-salt interfacial layers that interface with an all -solid-state electrolyte to enable clean separation of the electrode and the electrolyte in a recycling process while preserving electrochemical properties of the electrolyte and the electrode during the recycling process. Embodiments can further relate to a method of making an electrode having a flexible polymer-salt interfacial layer that interfaces with an all-solid-state electrolyte in an all-solid-state battery.BACKGROUND OF THE INVENTION

[0004] All-solid-state batteries provide opportunities for safe and robust energy storage solutions. An emerging issue is the final disposal of spent batteries due to the required production scale, limited lifetime, and lack of recycling methods. Here, we propose an architectural design for recyclable all-solid-state lithium batteries based on interfacial layers at the electrodes.SUMMARY OF THE INVENTION

[0005] Flexible lithium bis(fluorosulfonyl)imide doped polypropylene carbonate (PPC-LiFSI) interfacial layers improve physical contacts at Li metal and Li7La3Zr2Oi2(LLZO)-based composite electrolytes interfaces, and serve as sacrificial layers to enable clean separation andAtty. Ref. No. 0073605-001156direct recycling. Recovered components demonstrate the preservation of electrochemical properties through direct reintegration into batteries. Fully recovered full cells with Li-metal and LTO anodes show 92.5 % and 93.8% of original discharge capacity at 0.05 C and room temperature. We demonstrate an approach for the design of recyclable all-solid-state lithium batteries to fulfill long-term goals for sustainable energy storage devices.

[0006] An exemplary embodiment can relate to an electrochemical cell. The electrochemical cell can include an electrolyte having a first electrolyte interface surface and a second electrolyte interface surface opposite the first electrolyte interface surface. The electrochemical cell can include a cathode having a first cathode interface surface adjacent the first electrolyte interface surface and a second cathode interface surface opposite the first cathode interface surface. The electrochemical cell can include an anode having a first anode interface surface adjacent the second electrolyte interface surface and a second anode interface surface opposite the first anode interface surface. The electrochemical cell can include a flexible polymer-salt interfacial layer disposed upon the first cathode interface surface and / or the first anode interface surface.

[0007] In some embodiments, the electrolyte can be a Li7-La3-Zr-O12 (LLZO) solid electrolyte.

[0008] In some embodiments, the anode can be at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode.

[0009] In some embodiments, the flexible polymer-salt interfacial layer can be a polypropylene carbonate-lithium bis(fluorosulfonyl)imide (PPC-LiFSI) interfacial layer.

[0010] In some embodiments, the first cathode interface surface and / or the first anode interface surface having the flexible polymer-salt interfacial layer disposed thereupon can include a LiFSL Dimethyl Ether (LiFSI-DME) solution having a LiFSI molar concentration within a range of approximately IM to 12M.

[0011] In some embodiments, the cathode can be a lithium iron phosphate (LFP) cathode.

[0012] In some embodiments, the flexible polymer-salt interfacial layer can have an ionic conductivity of approximately 0.0039 Siemens per centimeter (3.9 x |03S / cm ') at a temperature range from approximately 65 to 85 degrees Fahrenheit

[0013] Another exemplary embodiment can relate to an electrode having a first electrode interface surface and second electrode interface surface opposite the first electrode interface surface and a flexible-polymer salt interfacial layer disposed upon the first electrode interface surface and / or the second electrode interface surface.Atty. Ref. No. 0073605-001156

[0014] In some embodiments, the first electrode interface surface and / or the second electrode interface surface can include a LiFSI-Dimethyl Ether solution having a LiFSI molar concentration within a range of approximately IM to 12M between the flexible polymer-salt interfacial layer and the first electrode interface surface and / or the second electrode interface surface.

[0015] In some embodiments, the flexible polymer-salt interfacial layer can be a polypropylene carbonate-lithium bis(fluorosulfonyl)imide (PPC-LiFSI) interfacial layer.

[0016] In some embodiments, the electrode can be a lithium iron phosphate (LFP) cathode.

[0017] In some embodiments, the electrode can be at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode.

[0018] In some embodiments, the LiFSLDME solution can have a quantity within a range of approximately 2 to 8 micro-liters per centimeter squared ( / I. / cm2).

[0019] Another exemplary embodiment can relate to a method of making an electrode having a flexible polymer-salt interfacial layer. The method can include dissolving, in an anhydrous acetonitrile solution, lithium bi(fluorosulfonyl)imide (LiFSI) and polypropylene carbonate (PPC), the dissolving occurring in an inert atmosphere, and the dissolving resulting in a polymer-salt solution. The method can include depositing the polymer-salt solution onto a film sheet, and storing, at a predetermined temperature, the polymer-salt solution deposited onto the film sheet until the polymer-salt solution is dried, resulting in a flexible polymer-salt film. The method can include separating the flexible polymer-salt film from the film sheet and applying the flexible polymer-salt film and a predetermined quantity of a LiFSI-Dimethyl Ether solution having a molar concentration within a range of approximately IM to 12M to a first interfacial surface of the electrode.

[0020] In some embodiments, the polymer-salt solution can include a ratio by mass of approximately 12:1:2 of anhydrous acetonitrile solution, lithium bi(fluorosulfynol)imide (LiFSI), and propylene carbonate (PPC), respectively.

[0021] In some embodiments, the inert atmosphere can include at least one of an argon, helium, nitrogen, or anhydrous air atmosphere.

[0022] In some embodiments, the predetermined temperature can include a temperature range from approximately 65 degrees to 85 degrees Fahrenheit.Atty. Ref. No. 0073605-001156

[0023] In some embodiments, the electrode can be a lithium iron phosphate (LFP) cathode, and the predetermined quantity of LiFSI-DME solution applied to the interfacial surface of the electrode can be within a range of approximately 2 to 8 micro-liters per centimeter squared ( / zL / cm2).

[0024] In some embodiments, the electrode can be at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode, and the predetermined quantity of LiFSI-DME solution applied to the interfacial surface of the electrode can be within a range of approximately 2 to 8 zzL / cm2.

[0025] Further features, aspects, objects, advantages, and possible applications of the present invention will become apparent from a study of the exemplary embodiments and examples described below, in combination with the Figures, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, aspects, features, advantages and possible applications of the present innovation will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings. Like reference numbers used in the drawings may identify like components.

[0027] FIG. 1 shows an exemplary embodiment of the electrochemical cell.

[0028] FIG. 2A shows an exemplary embodiment of the electrode.

[0029] FIG. 2B shows an exemplary embodiment of the electrode.

[0030] FIG. 3 illustrates an exemplary method of making an embodiment of the electrode.

[0031] FIG. 4 illustrates an exemplary method of recycling an embodiment of the electrochemical cell.

[0032] FIGS. 5A and 5B show Nyquist plots and an equivalent circuit model of Li metal symmetric cells with and without PPC-LiFSI layers.

[0033] FIGS. 6A and 6B illustrate the critical current density of Li metal symmetric cells with and without PPC-LiFSI.

[0034] FIGS. 7A and 7B show the wettability of molten Li metal on the surface of LLZO-SE with and without polymer-salt layers.

[0035] FIG. 8 illustrates Nyquist plots of pristine and cycled Li / i / LLZO-SE / i / Li with discharge capacity lesser than 50% of its original value.Atty. Ref. No. 0073605-001156

[0036] FIG. 9 illustrates the removal of polymer-salt interfacial layers that enables recyclability of all-solid-state lithium batteries.

[0037] FIG. 10 shows recovered components from LTO and Li anode-based full electrochemical cells.

[0038] FIG. 11 illustrates XRD spectra analyses of pristine LFP, LLZO, and LTO materials; recovered LFP, LLZO, and Li from electrochemical cells containing Li anode; recovered LLZO and LTO from electrochemical cells containing LTO anodes; and expected diffraction peaks from electrochemical cells for LFP, LTO, and LLZO with cubic and tetragonal phases.

[0039] FIG. 12A illustrates a post-mortem XPS analysis of a concentration of pristine elements and elements recovered from the electrochemical cell.

[0040] FIG. 12B illustrates a C Is XPS spectra analyses of pristine LLZO.

[0041] FIG. 12C illustrates an XPS spectra analyses and depth profile analyses of recovered LLZO from Li-based and LTO-based full electrochemical cells.

[0042] FIG. 13 A illustrates a Nyquist plot of pristine and fully recycled LFP / i / LLZO-SE / i / Li electrochemical cells.

[0043] FIG. 13B illustrates rate performance analyses of pristine and fully recycled LFP / i / LLZO-SE / i / Li electrochemical cells at room temperature.

[0044] FIGS. 14A and 14B illustrate galvanostatic charge and discharge curves of pristine and fully recycled LFP / i / LLZO-SE / i / Li electrochemical cells at room temperature.

[0045] FIG. 15A illustrates a Nyquist plot of pristine LFP / i / LLZO-SE / i / LTO electrochemical cells and fully recycled LFP / LLZO-SE / LTO electrochemical cells.

[0046] FIG. 15B illustrates rate performance analyses of pristine LFP / i / LLZO-SE / i / LTO electrochemical cells and fully recycled LFP / LLZO-SE / LTO electrochemical cells at room temperature.

[0047] FIGS. 16A and 16B illustrate galvanostatic charge and discharge curves of pristine LFP / i / LLZO-SE / i / LTO electrochemical cells and fully recycled LFP / LLZO-SE / LTO electrochemical cells at room temperature.

[0048] FIG. 17 shows the transparency and flexibility of the polymer-salter interfacial layer.

[0049] FIG. 18 illustrates a Nyquist plot of PPC-LiFSI at room temperature.

[0050] FIG. 19A illustrates a Nyquist plot of the ionic conductivity of PPC-LiFSI from-20 to 80 °C.Atty. Ref. No. 0073605-001156

[0051] FIG. 19B illustrates an Arrhenius plot of the ionic conductivity of PPC-LiFSI from -20 to 80 °C.

[0052] FIG. 20 illustrates thermogram analyses from differential scanning calorimetry (DSC) of PPC-LiFSI interfacial layer in comparison to pure polypropylene carbonate (PPC) on heating at 5 °C min1from -30 to 120 °C.

[0053] FIG. 21 shows a mechanical property assessment of PPC-LiFSI.

[0054] FIG. 22 illustrates stress-strain analyses of PPC-LiFSI.

[0055] FIG. 23 illustrates a Nyquist plot of symmetric Li metal electrochemical cells with PPC-LiFSI at interfaces, with and without 4M LiFSI / DME soaking of PPC-LiFSI.

[0056] FIG. 24 illustrates time dependence and voltage profiles of Li / i / LLZO-SE / i / Li electrochemical cells at a current density of 0.2 mA cm-2over 410 h.

[0057] FIG. 25 illustrates critical current density and area specific resistance of Li / i / LLZO-SE / i / Li electrochemical cells.

[0058] FIG. 26 illustrates cyclic voltammogram curves of LFP / i / LLZO-SE / i / Li electrochemical cells at a scan rate of 0.1 mV s1.

[0059] FIG. 27A illustrates the long-term electrochemical performance of LFP / i / LLZO-SE / i / LTO electrochemical cells cycled at 0.1 and 1.0 C-rates at room temperature.

[0060] FIG. 27B illustrates the long-term electrochemical performance of LFP / i / LLZO-SE / i / Li electrochemical cells cycled at 0.1 C-rate at room temperature.

[0061] FIG. 28 shows a separation process of separating the polymer-salt interfacial layer from LLZO-SE and LFP components.

[0062] FIG. 29 shows SEM images and EDS analyses of recovered LFP cathodes from LFP / i / LLZO-SE / i / LTO electrochemical cells.

[0063] FIG. 30 shows SEM images and EDS analyses of recovered LLZO from LFP / i / LLZO-SE / i / LTO electrochemical cells.

[0064] FIG. 31 shows SEM images and EDS analyses of recovered LTO anodes from LFP / i / LLZO-SE / i / LTO electrochemical cells.

[0065] FIG. 32 shows images of recovered Li metal anodes from cycled electrochemical cells.

[0066] FIG. 33 shows SEM and elemental mapping images of pristine and recovered Li metal from electrochemical cells.Atty. Ref. No. 0073605-001156

[0067] FIG. 34A illustrates FTIR spectra analyses of recovered LFP that is extracted from LTO-based full cells (Recovered LFP, LTO) and Li metal full cells (Recovered LFP, Li metal) compared against spectra from pristine LFP and PPC-LiFSI.

[0068] FIG. 34B illustrates FTIR spectra analyses of recovered LLZO that is extracted from LTO-based full cells (Recovered LLZO, LTO) and Li metal full cells (Recovered LLZO, Li metal) compared against spectra from pristine LLZO powder and PPC-LiFSI.

[0069] FIG. 34C illustrates FTIR spectra analyses of recovered LTO that is extracted from LTO-based full cells (Recovered LTO) compared against spectra from pristine LTO and PPC-LiFSI.

[0070] FIG. 35 shows a post-mortem SEM image of a spent LFP / LLZO-SE / i / Li electrochemical cell with PPC-LiFSI at the anode interface.

[0071] FIG. 36 shows SEM images of pristine and recovered LFP, LLZO, and LTO from the LFP / i / LLZO-SE / i / LTO electrochemical cell.

[0072] FIG. 37 illustrates the cycling stability of pristine and fully recycled LFP / i / LLZO-SE / i / Li electrochemical cells at 0.1 C-rate at room temperature.

[0073] FIG. 38 illustrates a Nyquist plot of a pristine LFP / i / LLZO-SE / i / LTO electrochemical cell and a cycled LFP / i / LLZO-SE / i / LTO electrochemical cell with discharge capacity lesser than 50% of its original value.

[0074] FIG. 39 shows optical images of the separation process for spent LFP / i / LLZO-SE / i / LTO, where spent LLZO-SE, LTO, and LFP were soaked in dimethylformamide followed by rinsed with dimethoxy ethane to remove polymer-salt layers, allowing the recovery of battery components.

[0075] FIG. 40 illustrates the galvanostatic charge and discharge curves of an electrochemical cell containing recovered LTO treated with ethylene carbonate at various C-rates at room temperature.DETAILED DESCRIPTION OF THE INVENTION

[0076] The following description is of exemplary embodiments that are presently contemplated for carrying out the present invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles and features of the present invention. The scope of the present invention is not limited by this description.

[0077] Referring to FIG. 1, embodiments can relate to an electrochemical cell 100. The electrochemical cell 100 can include an electrolyte 102. For instance, the electrolyte can be aAtty. Ref. No. 0073605-001156solid lithium-based electrolyte 102. The electrolyte 102 can include a first electrolyte interface surface 104 and a second electrolyte interface surface 106 opposite the first electrolyte interface surface 104. In some embodiments, the electrolyte 102 can be aLi7-La3-Zr2-O12 (LLZO) allsolid composite electrolyte. It is understood that the electrolyte 102 can be any suitable solid electrolyte, including lithium-ion super conductor (LISICON) electrolytes, such as Li2+2xZnl-xGeO4, perovskite electrolytes, such as La0.57Li0.29TiO3 (LLTO), polyethylene oxide electrolytes, polyethylene oxide block and graft copolymer electrolytes, etc.

[0078] The electrochemical cell 100 can include a cathode 110. In some embodiments, the cathode 110 can be a lithium iron phosphate (LFP) cathode 110. It is understood that the LFP cathode 110 is merely exemplary and that the cathode 110 can include any suitable cathode, such as a layered oxide (e.g., LiCoO2 and LiNixMnyCo2O2 (NMC)) cathode, a spinel oxide (e.g., LiMn2O4) cathode, an oxoanion complex (e.g., LiFePO4) cathode, etc. The cathode 110 can include a first cathode interface surface 112 and a second cathode interface surface 114 opposite the first cathode interface surface 112. In some embodiments, the first cathode interface surface 112 can be positioned adjacent to an electrolyte interface surface, such as the first electrolyte interface surface 104 or the second electrolyte interface 106, such that there exists electrical and ionic conductivity between the first cathode interface surface 112 and the adjacent electrolyte interface surface. The cathode 110 can include a current collector including an electrically conductive material or coating (E.g., Al, Cu, etc.) disposed upon the second cathode interface 114, such that the current collector can be in electrical conductivity with the cathode 110 and an external electrical load.

[0079] The electrochemical cell 100 can include an anode 116. The anode 116 can be a lithium and / or a graphite anode 116. For instance, the anode 116 can be a lithium metal (Li) anode, a lithium titanate (LTO) anode, and / or a graphite anode. It is understood that the Li, LTO, and / or graphite anode is merely exemplary and that the electrode 200 can include any suitable anode. The anode 116 can include a first anode interface surface 118 and a second anode interface surface 120 opposite the first anode interface surface 118. In some embodiments, the first anode interface surface 118 can be positioned adjacent to an electrolyte interface surface, such as the first electrolyte interface surface 104 or the second electrolyte interface 106, such that there exists electrical and ionic conductivity between the first anode interface surface 118 and the adjacent electrolyte interface surface. The anode 116 can include a current collector (not shown)Atty. Ref. No. 0073605-001156consisting of an electrically conductive material or coating (E.g., Al, Cu, etc.) disposed upon the second anode interface layer 120, such that the current collector can be in electrical conductivity with the anode 116 and an external electrical load (not shown).

[0080] As seen in FIG. 1, each of the individual components of the electrochemical cell 100, e.g., the electrolyte 102, the cathode 110, the anode 116, and the interfacial layer(s) 108, are shaped and sized such that the electrochemical cell 100 can be in the form of what is referred to in the art as a coin cell. It is understood that the illustrated coin cell shape of electrochemical cell 100 in FIG. 1 is merely exemplary, and that other embodiments can exist in which the individual components are sized and / or shaped according to desired technical specifications, technical applications, etc. For example, the individual components of the electrochemical cell 100 can be sized and / or shaped to accommodate technical applications across a range of technological fields, such as electric vehicles, variously sized portable consumer electronics, medical equipment, etc.

[0081] The electrochemical cell 100 can include one or more interfacial layer(s) 108. The interfacial layer can be a polymer, e.g., a flexible polymer-salt interfacial layer. The interfacial layer(s) 108 can be disposed upon the cathode 110 and / or the anode 116. For instance, the interfacial layer 108 can be disposed upon an interface surface of the cathode 110 and / or the anode 116 that is adjacent to the first electrolyte interface surface 104 and / or the second electrolyte interface surface 106. For example, as shown in FIG. 1, the electrochemical cell 100 can have an interfacial layer 108 disposed upon the first cathode interface surface 112 between the first cathode interface surface 112 and the first electrolyte interface surface 104, and an interfacial layer 108 disposed upon the first anode interface surface 118 between the first anode interface surface 118 and the second electrolyte interface surface 106. In some embodiments, the electrochemical cell 100 can have the interfacial layer 108 disposed only upon an interface surface of the cathode 110 or only upon an interface surface the anode 116. In other words, the electrochemical cell 100 can have the interfacial layer(s) 108 disposed between the cathode 110 and the electrolyte 102, between the anode 116 and the electrolyte 102, or both. The interfacial layer(s) 108 can be disposed between the electrolyte 102 and the cathode 110 and / or anode 116 such that there exists electrical and ionic conductivity between the electrolyte interface surface(s) of the electrolyte 102, the interfacial layer(s) 108, and the interface surface(s) of the cathode 110 and / or anode 116.Atty. Ref. No. 0073605-001156

[0082] In some embodiments, the interfacial layer 108 can be a flexible polymer-salt composite interfacial layer. For example, the interfacial layer 108 can be a polypropylene carbonatelithium bis(fluorosulfonyl)imide (PPC-LiFSI) interfacial layer. It is understood that PPC-LiFSI is merely an exemplary polymer-salt composite, and that the interfacial layer 108 can include any suitable polymer-salt composite. For example, a polymer-salt composite can include any combination of suitable polymers, such as polyethylene oxide, polypropylene oxide, block copolymers based on polyethylene oxide, and / or graft copolymers based on polyethylene oxide, and suitable salts, such as LiFSI, LiTFSI, LiClO4, and / or LiPF6.

[0083] It is understood that having the flexible polymer-salt layer 108 disposed between the interfaces of the cathode 110 and / or anode 116 and the electrolyte 102 of the electrochemical cell 100 can provide an easier and more efficient separation and / or recovery of these components during a recycling process while maintaining the desired performance metrics of both the electrochemical cell prior to recycling and of the recovered individual components after the recycling and recovery process is complete.

[0084] In some embodiments, the interface surface(s) of the cathode 110 and / or the anode 116 having the flexible polymer-salt interfacial layer(s) 108 disposed thereupon can include a LiFSI-Dimethyl Ether (LiFSI-DME) solution. The LiFSI-DME solution can have any suitable LiFSI molar concentration, such as a LiFSI molar concentration within a range of IM to 12M, e.g., 4M LiFSI-DME solution. The LiFSI-DME solution can be applied to an interface surface of the cathode 110 (e g., first cathode interface surface 112), an interface surface of the anode 116 (e g., first anode interface surface 118), the first electrolyte interface surface 104, the second electrolyte interface surface 106, the interfacial layer(s) 108, or any combination thereof. It is understood that the application of LiFSI-DME solution to an interface surface of the cathode 110 and / or anode 116 having an interfacial layer 108 disposed thereupon can facilitate enhanced contact between the cathode / anode interface surface(s) and the electrolyte interface surface(s), leading to more efficient ion transport and a reduction in interfacial resistance.

[0085] It is understood that the LiFSI-DME solution applied to the flexible polymer-salt interfacial layer(s) 108 is an exemplary solution, and that any suitable lithium-salt based solution can be applied to the flexible polymer-salt interfacial layer(s) 108. For example, the solution can include any suitable lithium salt, such as LiTFSI, LiClO4, and / or LiPF6, etc., and the solutionAtty. Ref. No. 0073605-001156can include any suitable solvent, such as tetrahydrofuran (THF), Diethyl Ether, Glyme (Dimethoxyethane), Dioxolane, Polyproplene Carbonate, Ethylene Carbonate, etc.

[0086] As discussed above, each of the individual components of the electrochemical cell 100 can be differently and / or similarly sized and shaped relative to each other. As depicted in exemplary FIG. 1, the electrolyte 102 can have the largest surface area (E.g., diameter) and / or largest thickness relative to the interfacial layer(s) 108, the cathode 110, and the anode 116. It is understood that the relative size / shape of the electrolyte 102, the cathode 110, the anode 116, and the interfacial layer(s) 108 can be of the same thickness, diameter, shape, etc., and / or can be of different thicknesses, diameters, shapes, etc. For example, in some embodiments the electrolyte 102, the cathode 110 and the anode 116 can be of the same thickness, but different diameters, of the same thickness and same diameter, of the same diameter and different thicknesses, of different thicknesses and different diameters, etc. relative to each other.

[0087] A non-limiting, exemplary, electrochemical cell 100 can have a total thickness of approximately 529.3 / mi, with the electrolyte 102 having a thickness of approximately 343 / mi, the cathode 110 having a thickness of approximately 46.2 / / m, a current collector disposed upon the second cathode interface 114 having a thickness of approximately 16.5 / mi, the anode 116 having a thickness of approximately 40 / mi, a current collector disposed upon the second anode interface 120 having a thickness of approximately 10 / / m, and the flexible polymer-salt interfacial layers 108 disposed upon the first cathode interface surface 112 and the first anode interface surface 118, respectively, each having a thickness of approximately 102 / mi. It is understood that the above thickness values are merely exemplary and that any suitable thickness values may be used.

[0088] The interfacial layer(s) 108 can have an average thickness suitable for balancing mechanical, thermal, and / or electrochemical properties (e.g., thermal stability, mechanical strength / stability, ionic / electrical conductivity, electrochemical stability, etc.) of the interfacial layer(s) 108. In a non-limiting example, the interfacial layer(s) 108 can have an average thickness of 102 ± 2 micrometers ( / mi). As discussed above, the interfacial layer(s) 108 can have any average thickness suitable to accommodate electrochemical cells of various sizes, shapes, applications, etc., and / or to achieve desired mechanical, thermal, and / or electrochemical properties. In some embodiments, the flexible polymer-salt interfacial layer 108 can have anAtty. Ref. No. 0073605-001156ionic conductivity of approximately 0.0039 Siemens per centimeter (3.9 * IO S / cm ') at a temperature range from approximately 65 to 85 degrees Fahrenheit.

[0089] It is understood that having the interfacial layer(s) 108 disposed between the interfaces of the cathode 110 and / or anode 116 and the electrolyte 102 of the electrochemical cell 100 can provide an easier and more efficient separation and / or recovery of these components during a recycling process, while also maintaining the desired performance metrics and operational characteristics of both the electrochemical cell prior to recycling and of the recovered individual components after the recycling and recovery process is complete.

[0090] Referring now to exemplary FIGS. 2 A and 2B, the electrode 200 can include a first electrode interface surface 202 and a second electrode interface surface 204 opposite the first electrode interface surface 202. The electrode 200 can be a cathode. For example, the electrode 200 can be a LFP cathode. It is understood that the LFP cathode is merely exemplary and that the electrode 200 can include any suitable cathode, such as a layered oxide (e.g., LiCoO2 and LiNixMnyCo2O2 (NMC)) cathode, a spinel oxide (e.g., LiMn2O4) cathode, an oxoanion complex (e.g., LiFePO4) cathode, etc. The electrode 200 can be an anode. For example, the electrode 200 can be a Li, LTO, and / or graphite anode. It is understood that the Li, LTO, and / or graphite anode is merely exemplary and that the electrode 200 can include any suitable anode.

[0091] The electrode 200 can include an interfacial layer 206 disposed upon the first electrode interface surface 202 or the second electrode interface surface 204. The interfacial layer 206 can be a flexible polymer-salt composite interfacial layer. For example, in some embodiments, the interfacial layer 206 can be a flexible polypropylene carbonate-lithium bis(fluorosulfonyl)imide (PPC-LiFSI) interfacial layer. It is understood that PPC-LiFSI is merely an exemplary polymer-salt composite, and that the interfacial layer 206 can include any suitable polymer-salt composite. For example, a polymer-salt composite can include any combination of suitable polymers, such as polyethylene oxide, polypropylene oxide, block copolymers based on polyethylene oxide, and / or graft copolymers based on polyethylene oxide, and suitable salts, such as LiFSI, LiTFSI, LiClO4, and / or LiPF6.

[0092] The electrode 200 can have a current collector (not shown) consisting of an electrically conductive material or coating (E.g., Al, Cu, etc.) disposed upon the electrode interface surface opposite the electrode interface surface upon which the interfacial layer 206 is disposed. For example, the electrode 200 can have the interfacial layer 206 disposed upon the first electrodeAtty. Ref. No. 0073605-001156interface surface 202 and a current collector (not shown) disposed upon the second electrode interface surface 204.

[0093] A non-limiting, exemplary, electrode 200 can have a LiFSI-DME solution on the first electrode interface surface 202 and / or the second electrode interface surface 204. The LiFSI-DME solution can be applied to the electrode interface surface upon which the interfacial layer 206 is disposed, and / or applied directly to the interfacial layer 206. The LiFSI-DME solution can have a LiFSI molar concentration within a range of approximately IM to 12M, e.g., 4M LiFSI-DME solution. It is understood that the application of the LiFSI-DME solution can facilitate enhanced contact between the electrode interface surface(s) and interface surface(s) of components in electrical and / or ionic conductivity with the electrode interface surface(s), such as an electrolyte, leading to more efficient ion transport and a reduction in interfacial resistance.

[0094] Further to the above, it is understood that the LiFSI-DME solution applied to the electrode interface surface and / or flexible polymer-salt interfacial layer(s) 206 is an exemplary solution, and that any suitable lithium-salt based solution can be applied to the flexible polymer-salt interfacial layer(s) 206. For example, the solution can include any suitable lithium salt, such as LiTFSI, LiClO4, and / or LiPF6, etc., and the solution can include any suitable solvent, such as tetrahydrofuran (THF), Diethyl Ether, Glyme (Dimethoxyethane), Dioxolane, Polyproplene Carbonate, Ethylene Carbonate, etc.

[0095] In an exemplary embodiment, in which the electrode 200 is a cathode and the interfacial layer 206 is a flexible polymer-salt interfacial layer, the electrode interface surface upon which the flexible polymer-salt interfacial layer 206 is disposed can include a specific quantity of LiFSI-DME solution. In some embodiments, the specific quantity of LiFSI-DME solution can include any suitable quantity, such as a quantity within a range of approximately 2 micro-liters per centimeter squared (wL / cm2) to 8 «L / cm2. For example, an LFP cathode having a cathode interface surface upon which the flexible polymer-salt interfacial layer 206 is disposed can include a quantity of 4M LiFSI-DME of approximately 3.98 / L / cm2. Further, in an exemplary embodiment in which the electrode 200 is an anode and the interfacial layer 206 is a flexible polymer-salt interfacial layer, the electrode interface surface which the flexible polymer-salt layer 206 is disposed thereupon can include a specific quantity of LiFSI-DME solution. For example, a lithium-based anode having an anode interface surface upon which the flexible polymer-salt layer 206 is disposed can include a quantity of 4M LiFSI-DME of approximatelyAtty. Ref. No. 0073605-0011565.97 zL / cm2. It is understood that the quantity of LiFSI-DME solution applied to the electrode 200 can

[0096] As shown in exemplary FIGS. 2A and 2B, the electrode 200 and the interfacial layer 206 are illustrated as being coin cell shaped. It is understood that the illustrated coin cell shape of the electrode 200 and the interfacial layer 206 in FIGS. 2A and 2B is merely exemplary, and that other embodiments can exist in which the electrode 200 and / or the interfacial layer 206 are sized and / or shaped according to desired technical specifications, technical applications, etc. For example, the electrode 200 and / or the interfacial layer 206 can be sized and / or shaped to accommodate technical applications across a range of technological fields, such as electric vehicles, variously sized portable consumer electronics, medical equipment, etc.

[0097] Further to the above, the sizes and / or shapes of the electrode 200 and the interfacial layer 206 may be the same, substantially similar, or different relative to each other. As illustrated in the example of FIG. 2A, the electrode 200 can be of similar or the same shape as the interfacial layer 206, the electrode 200 can be a smaller diameter than the interfacial layer 206, and the electrode can be of greater thickness than the interfacial layer 206. As illustrated in the example of FIG. 2B, the electrode 200 can be of similar or the same shape and diameter as the interfacial layer 206, and the electrode can be of greater thickness than the interfacial layer 206. It can be understood that these examples are merely illustrative and non-limiting, and that the electrode 200 and the interfacial layer 206 can include any combination of similar or different shapes, diameters, thicknesses, etc. relative to each other.

[0098] Referring to FIG. 3, embodiments can relate to a method of making an electrode having a flexible polymer-salt interfacial layer 300. In some embodiments, the method 300 can include dissolving lithium bis(fluorosulfonyl)imide (LiFSI) and polypropylene carbonate (PPC) in a solvent in an inert atmosphere to create a polymer-salt solution 302. For example, in some embodiments, the LiFSI-PPC can be dissolved in an anhydrous acetonitrile solution in an inert atmosphere to create a polymer-salt solution 302. It is understood that PPC-LiFSI is merely an exemplary polymer-salt, and that the method 300 can include any suitable polymer-salt. For example, a polymer-salt can include any combination of suitable polymers, such as polyethylene oxide, polypropylene oxide, block copolymers based on polyethylene oxide, and / or graft copolymers based on polyethylene oxide, and suitable salts, such as LiFSI, LiTFSI, LiClO4, and / or LiPF6. It is also understood that the solvent anhydrous acetonitrile solution is merelyAtty. Ref. No. 0073605-001156exemplary, and that any suitable solvent can be used, such as tetrahydrofuran, dimethylformamide, DMSO, acetone, ethyl acetate, methanol, ethanol, isopropanol, butanol, pentanol, hexanol, etc.

[0099] The method 300 can include depositing the polymer-salt solution onto a film sheet 304. The method 300 can include storing the polymer-salt solution deposited onto the film sheet at a predetermined temperature until the solution is dried into a flexible polymer-salt film 306. The method 300 can include separating the flexible polymer-salt film from the film sheet 308. The method 300 can include and applying the flexible polymer-salt film and a LiFSI-DME solution having a molar concentration of LiFSI within a range of approximately IM to 12M (e.g., 4M LiFSI-DME) to an interfacial surface of the electrode 310.

[0100] The electrode 310 can be a cathode. For example, the electrode 310 can be a LFP cathode. It is understood that the LFP cathode is merely exemplary and that the electrode 200 can include any suitable cathode, such as a layered oxide (e.g., LiCoO2 and LiNixMnyCo2O2 (NMC)) cathode, a spinel oxide (e.g., LiMn2O4) cathode, an oxoanion complex (e.g., LiFePO4) cathode, etc. The electrode 310 can be an anode. For example, the electrode 310 can be a Li, LTO, and / or graphite anode. It is understood that the Li, LTO, and / or graphite anode is merely exemplary and that the electrode 310 can include any suitable anode.

[0101] Further to the above, it is understood that the LiFSI-DME solution applied to the interfacial surface of the electrode 310 is an exemplary solution, and that any suitable lithium-salt based solution can be applied to the interfacial surface of the electrode 310. For example, the solution can include any suitable lithium salt, such as LiTFSI, LiClO4, and / or LiPF6, etc., and the solution can include any suitable solvent, such as tetrahydrofuran (THF), Diethyl Ether, Glyme (Dimethoxyethane), Dioxolane, Polyproplene Carbonate, Ethylene Carbonate, etc.

[0102] In some embodiments, the inert atmosphere can be an argon atmosphere, such as an argon atmosphere having less than 0.1 parts per million (ppm) Oxygen (02) and less than 0.1 ppm water (H2O). It is understood that an argon atmosphere is merely exemplary and that the inert atmosphere can include any suitable inert atmosphere, such as helium, nitrogen, anhydrous air, etc., atmospheres. In some embodiments, the quantities of LiFSI, PPC, and anhydrous acetonitrile can be a ratio by mass of 1:2:12, respectively.

[0103] In some embodiments, the film sheet can be an Aclar sheet. In an exemplary embodiment, the quantity of the polymer-salt solution deposited onto the film can beAtty. Ref. No. 0073605-001156approximately 46.5 / zL / cm2It is understood that 46.5 / / L / cm2is merely an exemplary quantity and that any suitable quantity of polymer-salt solution can be used. For example, in some embodiments the quantity can be as low as 23 / / L / cm2. In some embodiments, the quantity can be greater than, or significantly greater than 46.5 / L / cm2. The quantity of polymer-salt solution applied to the film can depend on the application, the desired average thickness of the film and polymer-salt solution, or any other suitable operational parameter that may be affected by the quantity of polymer-salt solution applied to the film. In some embodiments, the predetermined temperature can include a temperature within a range of temperatures from approximately 65 degrees to 85 degrees Fahrenheit.

[0104] In an exemplary embodiment, the electrode can be a lithium iron phosphate (LFP) cathode, the LiFSI-DME solution can have a LiFSI molar concentration of 4M, and the quantity of 4M LiFSI-DME applied to the interfacial surface of the electrode can be approximately 3.98 / L / cm2In another exemplary embodiment, the electrode can be a lithium metal (Li), lithium titanate (LTO) anode, and / or a graphite anode, the LiFSI-DME solution can have a LiFSI molar concentration of 4M, and the quantity of 4M LiFSI-DME applied to the interfacial surface of the electrode can be approximately 5.97 zzL / cm2. In exemplary embodiments, the quantity of LiFSI-DME solution applied to an interfacial surface of the electrode can include any suitable quantity, such as a quantity within a range of approximately 2 / L / cm2to 8 z / L / cm2. It is understood that the values of quantities, concentrations, temperature ranges, etc. discussed above in relation to the method 300 are non-limiting and exemplary and said values can be altered based on factors such as shape, size, material, intended application, desired operational characteristics, etc. of the electrode and / or the flexible polymer-salt interfacial layer.

[0105] The following disclosure discusses exemplary implementations, methods, and test data related to the same.

[0106] EXAMPLES

[0107] Example 1

[0108] Exemplary embodiments discussed in the EXAMPLES section relate to all-solid-state lithium-ion electrolytes, lithium -based electrodes, and flexible polymer-salt interfacial layers that provide an interface between a lithium electrode and an all-solid-state lithium electrolyte in allsolid-state electrochemical cell, or battery. The inventive flexible polymer-salt interfacial layers provide a balance between maintaining intimate contacts between electrodes and electrolytes inAtty. Ref. No. 0073605-001156an all -solid-state battery, while also allowing for easier and more efficient separation of electrodes from electrolytes during recovery and recycling processes.

[0109] The development of all-solid-state batteries is driven by the need to enhance electrochemical performance, lifespan, and safety in energy storage devices. Replacing conventional liquid electrolytes with solid alternatives can mitigate the risks associated with leakage and flammability. Moreover, the inherent mechanical strength and electrochemical stability of solid-state electrolytes can augment the structural stability and operating voltage window. These characteristics can enable the safe use of lithium metals anodes in all -solid-state batteries with improved energy density and longevity, even after long-term charge and discharge cycles.

[0110] The increasing demand for lithium-ion batteries in portable consumer electronics and sustainable transportation can push the limit of raw material availability and can result in substantial growth in waste that is generated as batteries reach end-of-life. Improper disposal and inadequate recycling practices can pose risks to human health and can threaten ecosystems and wildlife due to hazards associated with lithium, cobalt, and other heavy metals. The development of efficient and sustainable recycling processes can be essential to reducing the environmental impact of the green energy revolution and enabling circularity for valuable battery materials. As the consumption of lithium-ion batteries continues to grow, the management of spent lithium-ion batteries can minimize their negative environmental impact and can promote a more sustainable approach to energy storage technology.

[0111] Although efforts to recycle batteries continues to grow, few recycling strategies currently exist for solid state batteries. Current adopted lithium-ion battery recycling focuses on the recovery of a few key materials, such as lithium, cobalt, nickel, and other metals. This recycling can involve using a combination of energy intensive mechanical separation, pyrometallurgy, and hydrometallurgy processes to chemically breakdown battery components into simple precursors that can be recycled in production of new batteries. Nevertheless, these traditional recycling processes may not be sustainable when considering energy and material input costs and production of hazardous wastes. In addition, traditional recycling methods may not be suitable for all-solid-state lithium batteries, as the inclusion of solid electrolytes can bring additional challenges in recycling due to their unique battery architecture and chemistries. The diversity of designs and chemistries among different all-solid-state batteries can also complicateAtty. Ref. No. 0073605-001156the development of a universal recycling approach. As a result, developing recycling processes that can accommodate this variability while ensuring efficient resource recovery remains a substantial obstacle.

[0112] A more sustainable way to address spent all-solid-state batteries can be through direct recycling, which can avoid chemically breaking down battery components and can lower processing costs by minimizing material lost and energy inputs. This approach has not been demonstrated on all-solid-state batteries, likely because of the implementation of solid electrolytes. Compact microstructures can play an important role dictating cycling performance. The intimate contacts at solid-solid interfaces, however, can complicate the separation process, resulting in a mixture of electrolyte and electrode powders. To achieve a balance between intimate contacts and easy separation, one approach to enable recycling could be to engineer interfaces between the electrode and electrolytes that promote separation when needed.

[0113] Interfacial engineering has been explored for many years to tune the interfacial chemistry between electrodes and electrolytes and ensure effective contacts, low interfacial resistance, and high stability. Various strategies have been employed, including using anodes with Li-containing alloys, and introducing buffer layers by depositing inorganic metallic oxides, non-metallic element interlayers, and gel electrolytes. Batteries with engineered interfaces can introduce greater complexity in battery fabrication, which can present additional challenges in recycling. Nevertheless, one approach to enable effective recycling could be to engineer interfaces between the electrode and electrolytes that promote separation on demand.

[0114] Here, we propose an architectural design for recyclable all-solid-state lithium batteries by introducing interfacial layers at electrode interfaces to allow intimate contacts while also facilitating separation during recycling. To demonstrate the applicability of this strategy, flexible lithium salt doped polypropylene carbonate (polymer-salt) interfacial layers were introduced at electrode contacts in all-solid-state batteries. The flexible polymer-salt fdms can promote interfacial contacts between LLZO composite electrolytes and Li metal. The removal of polymer-salt layers can facilitate the component separation process, and can allow for direct recycling. Full cells with recycled components show good cycling performances, indicating the viability in recycling spent batteries. We provide a new structural design for recyclable batteries and an approach to promote the sustainability of energy storage technologies.Atty. Ref. No. 0073605-001156

[0115] Polymer-salt layers at lithium anodes provides better physical contacts enabling lithium-ion transport across interfaces

[0116] All solid-state batteries that incorporate lithium iron phosphate (LFP) cathodes, Li7-2x+yMgxLa3-ySryZr2Oi2-polypropylene carbonate-lithium perchlorate solid composite electrolytes (LLZO-SE), and Li metal or lithium titanate (LTO) anodes are chosen to demonstrate recy cl ability. The composite electrolyte, LLZO-SE, was fabricated using the cold sintering process, which can enable densification of composites comprised of ceramics, polymers, and salts at a low temperature with the addition of applied pressure and transient solvents.

[0117] The interface between Li metal anodes and LLZO solid electrolytes can play an important role in determining the cycling performance due to the lithiophobic nature of the LLZO surface, which can lead to poor physical contacts and high interface resistance. Strategies such as surface modification and interfacial engineering have been applied to improve the wettability and interface contacts. We introduce a soft polymer-salt layer, polypropylene carb onate-Li thium bis(fluorosulfonyl)imide (PPC-LiFSI), that can bridge solid-solid interfaces and enable lithium-ion transport between electrode and electrolyte.

[0118] The polymer-salt layer, PPC-LiFSI, can be transparent and flexible with an average thickness of 102 ± 2 «m (FIG. 17). To measure the ionic conductivity of this layer, we built symmetric cells with PPC-LiFSI in between aluminum blocking electrodes and 4M LiFSI / DME at the contacts. FIG. 18 shows a Nyquist plot from impedance spectroscopy, from which we obtain an ionic conductivity of 3.9 x 10 S cm1for PPC-LiFSI at room temperature. We also measured ionic conductivity in PPC-LiFSI from -20 °C to 80 °C, as shown in FIGS. 19A and 19B. Temperature-dependent conductivities were fit to the Arrhenius equation, to extract the activation energy (Ea) for ionic conduction of approximately 0.31 eV. As ion transport in polymer-salt films can depend strongly on polymer properties, we characterized thermal and mechanical properties of the polymer-salt layers (FIG. 20). With the incorporation of lithium salt into polypropylene carbonate ([O]:[Li+]=10: 1), PPC-LiFSI shows a lower glass transition temperature (Tg) around 13.5 °C, compared 19 °C for pure PPC. The low Tgsuggests a high segmental mobility of PPC, which can facilitate lithium-ion transport across the interfacial layer. The tensile stress-strain curve for dog bone-shaped PPC-LiFSI films, fabricated by drop-casting polymer-salt solution on the substrate and dried in the glovebox, is shown in FIG. 21, with theAtty. Ref. No. 0073605-001156corresponding properties shown below in Table 1. PPC-LiFSI shows plastic deformation with an ultimate tensile strength of 40 MPa, elongation at break of 113 % and Young’s modulus of 1,500 MPa.Table 1: Mechanical properties of PPC-LiFSIUltimate Tessile Strength Elo&gatira at Break Yotmg’s Modulus _ (MPa) _ (%) _ (MPa) _40.4 ±2.6 112.7 ± 11,6 1495.1 * 50.4

[0119] To examine the effect of incorporating PPC-LiFSI on interfacial resistance, the performance of Li metal symmetric cells with LLZO composite electrolytes was compared between cells incorporating PPC-LiFSI with 4M LiFSI / DME at interfaces and those without PPC-LiFSI. FIG. 5 A shows the total area specific resistance of half cells with and without PPC-LiFSI layers. Half cells that include polymer thin films show a substantial reduction in the total resistance, which is estimated to be around 208 ohm cm2; whereas half-cells without interfacial modifications have a total resistance around 2.9 x 104ohm cm2. The impedance spectrum of the half cells with interfacial layers was fit using an equivalent circuit model, shown in FIG. 5B. The first poorly-resolved semicircle at high frequency can be attributed to bulk (Rb) and grain boundary (RCPEgb) resistances (~ 36.07 fl in total) of the solid electrolyte. The second semicircle has an associated capacitance of 6.21 x 10-6F, which can be ascribed to the electrolyte-electrode interfaces (RCPEin) with an area specific resistance of 94 ohm cm2. The third semicircle in the low frequency region with a capacitance of 1.5 X 10-3F can be attributed to the electrochemical reaction (RCPEecr) at Li metal anode interfaces. The addition of a small amount of 4M LiFSI / DME solution can improve the wetting ability of the PPC-LiFSI layer at the Li metal and LLZO-SE interfaces, facilitating enhanced contact between the polymer layers and ceramic particles, leading to more efficient ion transport and a reduction in interfacial resistance (FIG. 23).

[0120] To characterize the effect of 4M LiFSI / DME at interfaces on the cell resistance, symmetric cells with LLZO-SE sandwiched by PPC-LiFSI interfacial layers and Li metal electrodes, Li / i / LLZO-SE / i / Li, were fabricated. FIG. 23 shows a Nyquist plot of the total impedance of a symmetric cell with and without the wetting of 4M LiFSI / DME at interfaces. Symmetric cells without 4M LiFSI / DME exhibit higher interfacial resistance of 149 ohm cm2,Atty. Ref. No. 0073605-001156compared to cells with incorporation of 4M LiFSI / DME at interfaces, with a value of 94 ohm 2cm

[0121] While PPC-LiFSI demonstrates good adhesion to the electrode surface, an inability to effectively wet LLZO-SE ceramics can limit the number of ion transport pathways at the interface. This poor wetting may be attributed to microscale surface irregularities of LLZO-SE, which may hinder optimal interfacial contact in the absence of adequate wetting. To mitigate this issue, the incorporation of a small quantity of liquid, 4M LiFSI / DME solution, can significantly enhance the wetting capability of the PPC-LiFSI layer at the interfaces between the Li metal and LLZO-SE. By improving wetting, the liquid facilitates better contact between the polymer layers and the ceramic particles, thereby facilitating ion transport and reducing interfacial resistance.

[0122] The stability of electrode-electrolyte interfaces was assessed by measuring critical current densities (CCD). The rate performances of Li metal symmetric cells were examined at current densities ranging from 0.1 to 4.0 mA cm2in a time-control manner with a 15 mins duration time at room temperature, as shown in FIGS. 5A, 5B, 6A, and 6B. Symmetric cells without PPC-LiFSI layers failed to safely cycle at a current density of 0.1 mA cm2. The failure mechanism is likely due to the poor contact between Li metal and solid electrolytes. With PPC-LiFSI, the symmetric cell demonstrates a stable polarization increase accompanied with the elevated current densities. A slight voltage drop at 2.6 mA cm'2implies the occurrence of soft short circuit due to the formation of small dendrites. The critical current density of symmetric cells with polymer-salt interfacial layers is estimated to be 2.4 mA cm2, suggesting a stable lithium-ion transport path across electrode interfaces under much higher cycling current densities. To study the effect on the performance of lithium plating / stripping, symmetric cells with PPC-LiFSI interfacial layers, which we denote as Li / i / LLZO-SE / i / Li, were cycled at a current density of 0.2 mA cm'2over long cycles, where 0.1 mAh cm2capacity of lithium metal was plated / stripped during each cycle (FIG. 24). The cycling curve shows a stable voltage-time profile with small polarization up to -410 hours, followed by a sharp increase in overpotential, likely due to interphase delamination.

[0123] To examine the contact between LLZO-SE and Li metal, we examined the wettability by depositing molten lithium (with the oxide layer of Li metal manually removed) on heated LLZO-SE with and without polymer-salt layers on the top. As shown in FIGS. 7A and 7B, theAtty. Ref. No. 0073605-001156composite electrolyte with polymer-salt layers shows a smaller contact angle compared to the one without. Color change of the sample with polymer-salt layers is due to partial degradation of polymer layers at high temperature (above the Li melting temperature -181 °C). The high contact angle results from the lithiophobic nature of LLZO against Li-metal; whereas Li metal maintains adherence to the LLZO-SE surface with the presence of soft polymer-salt layers bridging the solid-solid interfaces. This supports the idea that introducing polymer-salt layer can promote intimate contact between LLZO-SE and Li metal that can lead to reduced interfacial resistance.

[0124] Ion transport across electrolyte-Li metal interfaces is limited by area specific resistances and strongly governs critical current densities. We compare these values with previous results in FIG. 25. The inverse correlation highlights how controlling interfacial chemistry can achieve high power density. Our results demonstrate an approach for achieving low area specific resistance and higher critical current density compared to most of the reported data.Furthermore, our method can have advantages related to the use of low-cost materials and low energy-consuming processes (Table 2).Table 2: Comparison of critical current densities (CCD) and area specific resistance (ARS) of Li-metal symmetric cells with LLZO-based solid electrolytesAtty. Ref. No. 0073605-001156.. . . | .. .. . CCD ASR ProcessD,Matenal Method(mA cm2) (ohm cm2) temperature (°C)RefAI2O3Pulsed laserQ 48 2 2 RT 13depositionMoS2Dry-polishing 2.2 14 RT 14Polishing and2 8175RT 15spreadingSanding and heat-Q Q5pressingAl Alloying 0.9 1 250 17Au Sputtering 1.15 3 250-300 18 Sulfon .at .ed-covale .nt S „o ,lut ..ion process _ 3 9 „9„organic framework 200 19Mg Alloying 2 142 350 20 LiAIO2Coating 0.75 14 Sintering at 1100 21 Si Plasma-enhancedQ 2 127 300Ga Doping 0.16 16.7 Sintering at 1150 23 PVDF-HFP Casting 0.125 214 RT 24Al Doping 0.1 12.1 Sintering at 1175 23ZnO Atomic layer0.120150 25p deposition

[0125] Full cells with interfacial layers on both cathode and anode side, which we denote as LFP / i / LLZO-SE / i / Li or LFP / i / LLZO-SE / i / LTO, were assembled to test performance, and compared with recycled full cells, which are further discussed below in the fully recycled full cells with recovered components section. The cyclic voltammogram curves of LFP / i / LLZO-SE / i / Li are shown in FIG. 26. Two characteristic peaks are apparent that correspond to the charge (2.95 V) and discharge (3.77 V) potential of LiFePO4. No other redox peak can be observed during the cycling process, which implies that no unexpected side reaction occurred. The three curves nearly overlap, except for the first cycle, which can be attributed to the formation of a solid electrolyte interphase (SEI). This indicates that the polymer-salt layers can enable lithium-ion transport along the interfaces while providing excellent reversible behavior and electrochemical stability.

[0126] FIGS. 27A-B depict the long-term electrochemical performance of LFP / i / LLZO-SE / i / LTO and LFP / i / LLZO-SE / i / Li at room temperature. LFP / i / LLZO-SE / i / LTO demonstratesAtty. Ref. No. 0073605-001156an initial discharge capacity of 154 mAh g After cycling at 0.1 C for 100 cycles, the full cell shows a discharge capacity of 129 mAh g1with a Coulombic efficiency of 99% and a capacity retention rate of 83.8%. The entire cycling measurement spanned approximately 76 days. To accelerate degradation, LFP / i / LLZO-SE / i / LTO cells were cycled at a higher rate of 1.0 C at room temperature. Under these conditions, the full cell demonstrates a reduced discharge capacity of 40.7 mAh g1with a Coulombic efficiency of 98.6% and a capacity retention rate of 49.2%. At this stage, the cycled full cells, referred to as 50% DCp, are subjected to the recycling process. LFP / i / LLZO-SE / i / Li shows an initial capacity of 147 mAh g '. The discharge capacity of the full cell dropped to 63.5 mAh g1with a Coulombic efficiency of 80% and a capacity retention rate of 43.2 %.

[0127] The full cell configuration employing a Li metal anode without the incorporation of PPC-LiFSI demonstrated a remarkably high total impedance, which severely impeded its ability to be cycled effectively. Moreover, the absence of PPC-LiFSI in the full cell also posed challenges to the separation process; consequently, in-depth studies of cycling behavior without PPC-LiFSI are outside of the scope of this work.

[0128] Overall, our results demonstrate an approach forbridging the electrolyte-electrode interfaces to achieve low area specific resistance and high critical current density, and as discussed below in the removal of interfacial layers section, recyclability with the use of low-cost material and low energy-consuming processes.

[0129] Removal of interfacial layers enables the delamination of battery components, allowing direct recycling of all-solid-state batteries

[0130] Pristine full cells were cycled at a certain C-rate until the discharge capacity reached less than 50% of its original discharge capacity (denoted as 50% DCp), after which the full cells underwent recycling (FIGS. 27A and 27B). Nyquist plots of pristine and recycled Li metalbased full cells show a slight increase in the bulk and grain boundary resistance from 36.9 ohm to 53.12 ohm; whereas, the impedance at the interfaces increases from 338 ohm to 3710 ohm, as shown in FIG. 8. The occurrence of lithium dendrite growth and the buildup of isolated dead lithium can result in volume change within the cell, creating internal stress that leads to the formation of cracks and fractures at the interfaces of the microstructures of solid-state batteries. These structural instabilities obstruct pathways for lithium-ion transport, resulting in elevated interfacial impedance. The failure of the full cell is dictated by evolution and degradation atAtty. Ref. No. 0073605-001156interfaces, while the majority of LLZO-SE remain intact. Therefore, it is conceivable that spent battery components could be recycled without necessitating complex processes once localized interfaces are eliminated.

[0131] Spent batteries were further disassembled and underwent a delamination process where the removal of polymer-salt layers allows the separation and recovery of spent components. Recovered components were then reused and incorporated into a new battery, as illustrated in FIG 9. Dimethylformamide (DMF), an aprotic solvent, which is compatible with LLZO within a short duration, was used to dissolve the polymer-salt layer where undesired side reactions and secondary phases occur. In addition, DMF may react with Li metal, enabling the effective removal of a significant portion of lithium dendrites exposed to the surface of spent LLZO-SE, as depicted in FIG. 28.

[0132] FIG 10 shows optical images of recovered components. Recovered LLZO-SEs show an off-white color with an average recovery rate of around 85-90 wt%, while recovered LFP and recovered LTO have a blackish color with limited amount of weight loss. Although the color difference among recovered components implies an efficient separation, SEM images and elemental mapping analysis on recovered components (FIGS. 29-31) suggest that trace contamination of recovered electrolytes on recovered electrodes occurs, and vice versa. Even with limited mixing during recovery, we hypothesize that the incorporation and removal of polymer-salt interfacial layers is an effective recovery strategy to effectively avoid the formation of anode-cathode mixtures, otherwise known as black mass.

[0133] We also examined cycled Li metal anodes. After cycling, Li metal anodes are not uniform (FIG. 32) when compared to pristine Li metal electrodes with smooth surfaces and small number of defects. This non-flat surface can likely be attributed to uneven deposition of lithium during cycling. EDS analysis shows that white surface features primarily consist of oxygen and carbon (FIG. 33).

[0134] FIG. 32 shows optical images of recovered Li metal anodes from symmetric cells cycled at 0.2 mA cm2for 459 hours. After the recovery process, the Li metal anodes exhibit a white surface layer. After storing the recovered Li metal electrode in an argon-filled glove box for 24 hours, the color of the layer changed to black. FIG. 33 shows SEM images of pristine and recovered Li metal anodes. The pristine Li metal sheet displays a smooth surface with only a small number of defects. In contrast, recovered Li metal is covered with a non-uniform surfaceAtty. Ref. No. 0073605-001156layer. This non-flat surface can be attributed to the uneven deposition of lithium during the cycling process. EDS analysis revealed that the whitish components on the surface of the recovered Li metal primarily consist of oxygen and carbon.

[0135] Recovered electrodes and electrolytes show high degree of crystallinity after separation and recovery

[0136] To study the purity and bulk phase of recovered components, recovered LFP, LLZO, and LTO were characterized using XRD, as shown in FIG. 11. Recovered LFP from LTO and Li-based full cells possess olivine crystal structures, with XRD data with larger noise than profiles from pristine LFP due to uneven surfaces after recovery. Recovered LLZO from full cells with LTO anodes demonstrate a cubic crystalline phase with a space group of Ia-3d, which is the same as pristine LLZO. XRD spectra of recovered LLZO from Li metal -based full cell shows a cubic crystalline (c-LLZO) bulk phase; but minor peaks at 1.98, 2.26, and 2.40 A1suggest the presence of a minor quantity of tetragonal phases (t-LLZO). Although LLZO is reported to be compatible with Li metal, several previous reports proposed that c-LLZO may experience an interfacial cathodic reaction when in contact with Li metal. As the reduction process advances, along with electron transfer, lithium ions diffuse from Li metal into c-LLZO in order to maintain charge balance. The increase in Li content could energetically favor a structural transition from the cubic to the tetragonal phase. This t-LLZO interface is approximately 6 nm thick, and may not be perceptible with the use of X-ray diffraction techniques. In the case of recovered LTO, a spinel crystal structure with a space group of Fd3m, which is the same as pristine LTO, is apparent. Overall, the absence of any new phases indicates that the recovery process was carried out without degrading the bulk crystal structures of cell components.

[0137] To further investigate the occurrence of undesired reactions during recovery, pristine and recovered components from Li metal and LTO anode-based full cells were characterized using FTIR in an attenuated total reflection (ATR) geometry FIGS. 34A-34C. Successful removal of interfacial layers can be confirmed as spectra of recovered components did not show any characteristic peaks belonging to PPC-LiFSI. Recovered electrodes displayed a similar spectra as pristine ones, implying that there is no perturbation to the chemical structure from the recovery process. Peaks at 3670 cm1in pristine and recovered LLZO may be attributed to the O-H stretching from lithium hydroxide, a common surface contaminant when LLZO reacts withAtty. Ref. No. 0073605-001156ambient water. A higher intensity in the 0-H stretching peak in recovered LLZO from the Li metal anode-based full cell is apparent when comparing to pristine and reprocessed LLZO from an LTO-based full cell. This can be explained by the lithium deposited in the microstructure of recovered LLZO, as lithium metal oxidized to form lithium hydroxide. We did not detect any peaks from DMF and DME, implying that solvents were not left in the recovered components after direct recovery. Overall, the similar spectra before and after recovery suggests that the recovery process is compatible with battery components.

[0138] A post-mortem SEM image of spent LFP / LLZO-SE / i / Li (one PPC-LiFSI layer at the anode interface) reveals that the Al current collector, LFP, and LLZO electrolyte composites have thicknesses of approximately 16.5, 46.2, and 343 / m, respectively, and a total thickness of 493 / m (FIG. 35). Consequently, subtracting the thicknesses of the Li and copper foils, 40 / urn and 11 z / m, respectively, we can estimate the thickness of the interfacial layers in the full cell to be around 36.3 / m. SEM images of pristine and recovered electrodes and electrolyte are shown in FIG. 36. Both pristine and recovered battery components demonstrate similar surface morphologies with no significant change in particle sizes and shapes. Post-mortem X-ray photoelectron spectroscopy (XPS) was performed to study the surface chemistry on recovered LLZO from LTO and Li metal anode-based full cells.

[0139] The concentrations of elements detected on as received surfaces are shown in FIG. 12A. Measurements were conducted at a takeoff angle of 45° relative to the sample surface plane, yielding a sampling depth of 3-6 nm, with 95% of the signal originating from this depth or shallower. The measurement confirmed that the near-surfaces were enriched in Li and O, and depleted in Zr and La for both pristine and recovered LLZO. With a minimal amount of La and Zr detected, Li and O appearing at the near-surfaces can be ascribed to LiOH. This confirms the presence of larger amounts of oxide on surfaces of recovered LLZO from Li metal anode-based full cells, probably due to the oxidation of deposited lithium dendrites. In the C Is XPS spectra (FIG. 12B), a stronger CO3 peak was observed in recovered LLZO from Li -based full cell than the pristine state, which can be attributed to Li2COs, resulting from the reaction between LiOH and CO2. Recovered LLZO from an LTO-based full cell shows a higher amount of C, which mostly can be attributed to C-C bonds according to the C is spectra. The source of carbon may come from the carbon additives in LTO anodes. FIG. 12C shows the depth profile of theAtty. Ref. No. 0073605-001156concentration of Li, La, Zr, O, and C as a function of sputtering depth from recovered LLZO from a Li-based full cell.

[0140] Depth profiles confirmed that the near-surfaces were enriched in Li and depleted in Zr. Oxides and carbonates concentrate at 0-6 nm beneath the surface, suggesting the existence of an uppermost layer comprised of LiOH and Li2CO3. Carbonates decrease gradually reaching the minimum concentration at about 41 nm, indicating the native oxide / hydroxide layers of LLZO with a thickness of around 35 nm. The increase in Zr and La contents and decrease in both carbonate and Li oxide / hydroxide concentrations as sputtering depth increases suggests the bulk phase of pristine LLZO. The concentration with depth is summarized in FIG 12C. These findings show the surface of recovered LLZO is covered with contaminants formed during recycling.

[0141] Fully recycled full cells with recovered components demonstrate good cycling performance.

[0142] Recovered LLZO was reprocessed by cold-sintering, which in our previous work demonstrates the ability to fix fragmented microstructures and re-integrate LLZO with polymer and lithium salts to form a dense bulk phase. To evaluate the electrochemical performance and stability of recovered components, fully recycled all-solid-state batteries were fabricated by integrating recovered components (fully recycled LFP / i / LLZO-SE / i / Li is incorporated with recovered LFP and recovered LLZO-SE; fully recycled LFP / i / LLZO-SE / i / LTO is incorporated with recovered LFP, recovered LLZO-SE, and recovered LTO). FIG. 13A shows Nyquist plots of the pristine and fully recycled LFP / i / LLZO-SE / i / Li, where high-frequency semicircles and a low-frequency spike can be observed. Both demonstrate similar grain boundary resistances, approximately 22.5 ohm and 38.7 ohm, respectively. Fully recycled LFP / i / LLZO-SE / i / Li shows a significant decrease in the interfacial resistance around 409 ohms after recycling compared to cycled full cells (FIG. 8). This suggests that the removal of polymer-salt layers during the separation process can enable the elimination of most of the electrochemical byproducts localized at interfaces. Solid-state electrodes and electrolytes remain electrochemically functional after cycling. Thus, we hypothesize that we can reuse battery components without undergoing complicated recycling processes and can demonstrate recycling of full cells.

[0143] FIG. 13B illustrates the rate performance and coulombic efficiency of pristine and fully recycled LFP / i / LLZO-SE / i / Li at various C rates at room temperature. For a loading of LFP (1 CAtty. Ref. No. 0073605-001156= 170 mAh / gLFp) of around 0.012 g cm2:the current density at 1 C is 0.58 mA cm2Pristine full cells show a discharge capacity of 160 and 154 mAh g1at 0.1 and 0.2 C, while fully recycled LFP / LLZO-SE / Li cells show an average discharge capacity of 148 and 121 mAh g demonstrating a recovery of 92.5 and 78.6% of the original capacity, respectively (FIG. 13B).

[0144] The cycling stability of pristine and fully recycled LFP / i / LLZO-SE / i / Li at 0.1 C at room temperature is shown in FIG. 37. The pristine full cell shows a stable cycling performance over 32 cycles with a discharge capacity of 109 mAh g1with a Coulombic efficiency of 90 % and a capacity retention rate of 74 %. Similar cycling performance is observed for the fully recycled full cell, with stable retention performance and a discharge capacity of 106 mAh g1with a Coulombic efficiency of 92 % and a capacity retention rate of 70 % after 30 cycles.

[0145] This implies retention of electrochemical properties in recovered components due to the elimination of most secondary phases at interfaces, regardless of the limited presence of contaminants. The decrease in discharge capacity may result from a surface contaminant, specifically lithium hydroxide. Although lithium hydroxide was found to be present on surfaces, recycling can mix surface and bulk layers and can embed LiOH into the bulk phase during cold sintering. Thus, the presence of lithium hydroxide with low ionic conductivity may explain the lower discharge capacity in fully recycled LFP / i / LLZO-SE / i / Li.

[0146] Charge and discharge curves of the pristine and fully recycled LFP / i / LLZO-SE / i / Li full cell at various C rates are shown in FIGS. 14A and 14B). Both cells exhibit a flat discharge plateau at 0.1 and 0.2 C, while fully recycled LFP / i / LLZO-SE / i / Li shows a higher charge / discharge potential gap of 0.24 V compared to 0.22 V for pristine devices. The increase in voltage difference and loss in cycling stability can be attributed to the presence of oxides in recovered components. The non-conductive phases may hinder ion transport pathways, leading to an increase in Ohmic resistance and polarization in the full cell. This phenomenon can become more pronounced during cycling at elevated C rates or over extended cycling periods. An inhomogeneous distribution of applied current density may facilitate growth of lithium dendrites and degrade electrochemical properties.

[0147] To demonstrate that the recyclability of all-solid-state lithium batteries is not limited to Li metal anodes, pristine and fully recycled LTO anode-based full cells were evaluated, as shown in FIGS. 15A-B and 16A-B. Pristine LFP / i / LLZO-SE / i / LTO were cycled at a certain C-rate until the discharge capacity reached < 50% of its original discharge capacity. Nyquist plots ofAtty. Ref. No. 0073605-001156pristine and cycled LFP / i / LLZO-SE / i / LTO is shown in FIG. 38, demonstrating a similar total impedance of bulk and grain boundaries of LLZO-SE around 53 and 43 ohms, while a large increase in interfacial resistance from 416 to 2480 ohms is apparent after cycling. This implies that LLZO-SE remains mostly intact while electrochemical byproducts tend to concentrate at interfaces. The separation process is shown in FIG. 39, which highlights the efficient and successful separation of spent LFP, LLZO-SE and LTO. FIG. 39 shows optical images of the separation process for spent LFP / i / LLZO-SE / i / LTO, where spent LLZO-SE, LTO, and LFP were soaked in dimethylformamide followed by rinsed with dimethoxy ethane to remove polymer-salt layers, allowing the recovery of battery components

[0148] Fully recycled, LTO-based full cells were fabricated with the use of recovered battery components and compared with pristine full cells. Given that recovered electrodes did not undergo further processing to maintain compactness, cold sintering was used to co-sinter recovered electrodes with recovered LLZO powders to form compact tri-layer microstructures, denoted as LFP / LLZO-SE / LTO. FIG. 15A presents the Nyquist plots of fully recycled LFP / LLZO-SE / LTO, which displays a total impedance of bulk and grain boundaries of LLZO-SE at 115 ohm and an interfacial impedance of 128 ohm. A noticeable reduction in the interfacial impedance between electrolyte and electrode is evident when compared to the cycled full cell (FIG. 38). This indicates the successful elimination of undesired phases at interfaces during recycling. Nevertheless, the slight rise in total impedance of LLZO-SE suggests the presence of a small amount of contaminants.

[0149] The cycling performance of LTO-anode based full cells with interfacial layers at room temperature is shown in FIGS. 15B, 16A-B. The rate performance of pristine and fully recycled LTO anode-based full cells (denoted as pristine LFP / i / LLZO-SE / i / LTO and fully recycled LFP / LLZO-SE / LTO, respectively) at various discharge rates is shown in FIG. 15B. Pristine LFP / i / LLZO-SE / i / LTO cells show a better rate performance compared to fully recycled cells, as the discharge capacities that pristine full cell can deliver are approximately 162, 157, and 149 mAh g1at 0.05, 0.1, and 0.2 C, respectively. The fully recycled LFP / LLZO-SE / LTO cell can reach to 130, 113, and 62 mAh g1at 0.05, 0.1, and 0.2 C, respectively. Approximately 80 % of the original discharge capacity can be recovered at 0.05 C.

[0150] The galvanostatic charge / discharge curves of pristine and fully recycled LTO anodebased full cells are shown in FIGS. 16A-B. The cell voltage difference of the charge andAtty. Ref. No. 0073605-001156discharge plateau of pristine and fully recycled full cells was approximately 120 mV and 240 mV, respectively. The slightly larger voltage interval of fully recycled LFP / LLZO-SE / LTO indicates higher polarization during the charge-discharge process, which can be attributed to the presence of non-lithium-ion conducting phases in both electrodes and electrolytes. The poorly conducting phases hinder lithium-ion and electron diffusion in fully recycled LFP / LLZO-SE / LTO.

[0151] The modest decrease in the electrochemical performance of fully recycled LFP / LLZO-SE / LTO might be a consequence of build-up of contaminants or electrochemical reaction byproducts and the incompact microstructures of recovered electrodes. Calendering is a crucial process to reduce porosity and to improve particles compaction. As recovered LFP and recovered LTO did not experience any further treatment, the loose packing and inhomogeneity may consequently decrease electrochemical performance. In addition, during the recovery process, exposure to solvents may lead to the formation of poorly conductive oxides, hindering battery performance. Thus, we can attempt to dissolve oxide layers during the recovery process using ethylene carbonate (EC), which can partially dissolve lithium salts at solid electrolyte interfaces, such as lithium fluoride (LiF), lithium hydroxide (LiOH), lithium carbonate (Li2CC>3), and lithium oxalate ((LiCCh ). A full cell with an EC-treated recovered LTO anode shows a discharge capacity of 152, 138, and 88 mAh g1at 0.05, 0.1, and 0.2 C, respectively (FIG. 40). Approximately 93.8 % of the original discharge capacity (162 mAh g1for a pristine full cell) can be recovered at 0.05 C. Our preliminary results suggest that with the proper post treatment to remove surface contaminants, recycled battery components can deliver improved electrochemical performance. Future work is needed to optimize recycling strategies.

[0152] Regardless of the modest loss in electrochemical performance, fully recycled Li metal and LTO-anode based-full cells can deliver nearly the same rate performance as pristine cells, implying the preservation of electrochemical properties in recovered battery components after undergoing recovery and reprocessing. Polymer-salt layers can promote contacts at interfaces, facilitate effective separation and recovery of spent battery components, and enable recycling of spent all-solid-state lithium batteries. The architectural design of recyclable all-solid-state batteries with engineered interfaces can be applied on other types of batteries with different chemistries. Overall, we provide an approach and insights on the design of recyclable all-solid-state lithium batteries to promote sustainable energy storage through the incorporation ofAtty. Ref. No. 0073605-001156polymer-salt interfacial layers that promote electrode-electrolyte contact and enable separation and recovery of components. Our work provides insights on the architectural design of recyclable all -solid-state batteries, and offers a scalable and sustainable pathway for managing spent batteries at end of life.

[0153] Methods

[0154] Method of making polymer-salt interfacial layers

[0155] Lithium bis(fluorosulfonyl)imide (LiFSI) (Sigma Aldrich, ultra dry, 99.9% trace metals basis) (Sigma Aldrich, battery grade, dry, 99.99% trace metals basis) and polypropylene carbonate (Sigma Aldrich, average Mn-50,000 Da) were dissolved in acetonitrile (ACN, Sigma Aldrich, anhydrous) with a ratio of 1:2:12 by mass under argon atmosphere (O2 < 0.1 ppm and H2O < 0.1 ppm). The polymer-salt solution was deposited on Aclar sheets (46.5 z / L / cm2), dried and stored at the room temperature. Polymer-salt thin films can be easily released from the substrates for further use.

[0156] Method of making LLZO-PPC-LiClO4 solid-state electrolyte composites

[0157] Li7-2x+yMgxLa3-ySryZr20i2, (LLZO, 0.1<x<0.3, 0<y<0.5, particle size -1 / m) powders were mixed with polymer-salt solution and N, N-Dimethylformamide (DMF, Sigma Aldrich, anhydrous) (12:2.5: 1 by mass) using a mortar and a pestle. The mixture was introduced into a hardened steel pressing die with a diameter of 13 mm and underwent the cold sintering process by being pressed and sintered under a uniaxial pressure of 100 bar at 100 °C for 1 h. To ensure uniform sintering temperature, two heating platens and a band heater were used to encircle the die to prevent any temperature variations. As the temperature dropped below 50 °C, as-prepared composite electrolytes were released. All the preparation processes were performed under an argon atmosphere.

[0158] Methods of material characterization

[0159] The crystal structure and secondary phases of battery components were analyzed by X-ray diffractometry (Malvern Panalytical Empyrean, Cu Ka radiation, 40 kV, 40 mA). Collected spectra were analyzed using MDI JADE. Field emission scanning electron microscope and energy dispersive spectrometer (FE-SEM and EDS, Verios G4, Thermo Scientific) were performed to characterize the surface morphology, cross-sectional structures, and elemental mapping of battery components. Fourier-transform infrared spectroscopy (FTIR) was carried out using a Bruker Vertex 80 spectrometer. X-ray photoelectron spectroscopy (XPS) experimentsAtty. Ref. No. 0073605-001156were performed using a Physical Electronics VersaProbe TIT instrument equipped with a monochromatic Al ka x-ray source (hv = 1486.6 eV) and a concentric hemispherical analyzer. Charge neutralization was performed using both low energy electrons (<5 eV) and argon ions. The binding energy axis was calibrated using sputter cleaned Cu (Cu 2p3 / 2 = 932.62 eV, Cu 3ps / 2 = 75.1 eV) and Au foils (Au 4f? / 2 = 83.96 eV). Peaks were charge referenced to CHXband in the carbon Is spectra at 284.8 eV. Measurements were made at a takeoff angle of 45° with respect to the sample surface plane. This resulted in a typical sampling depth of 3-6 nm (95% of the signal originated from this depth or shallower). Quantification was done using instrumental relative sensitivity factors (RSFs) that account for the X-ray cross section and inelastic mean free path of the electrons. On homogeneous samples, major elements (>5 atom%) tend to have standard deviations of <3% while minor elements can be significantly higher. The analysis size was -200 im in diameter. Tensile properties of PPC-LiFSI were determined following ASTM D638 Type V using an Instron 5943 (100 N load cell) at 10 mm min ’. The cross-sectional area (thickness and width) was measured with digital calipers prior to deformation. The tensile results are reported as engineering stress and strain to determine the Young's modulus, ultimate tensile stress, strain at break. The tensile properties were all tested multiple times (n = 3) and averages are reported.

[0160] Method of making all-solid-state batteries and electrochemical testing

[0161] Anode discs were punched from single side laminated lithium copper foils (MSE Supplies, thickness of lithium and copper - 40 and 11 / zm, respectively) and single-sided Li4Ti50i2 (LTO) copper sheets (NET corporation, tape thickness - 60 urn ± 12 / zm). Cathode discs were cut from single side coated LiFePCh sheets (MTI Corporation, coating thickness -68 / zm ± 10 / zm). Before full cell assembly, surface oxides were scratched off from lithium discs by razor blades to show metallic surface. LTO and LFP electrodes are heated at 100 °C for over 1 hour under argon environment. For the fabrication of Li symmetric cells, composite electrolytes were placed between two Li metal discs with and without the introduction of polymer-salt films at the interfaces.

[0162] To fabricate LFP / i / LLZO-SE / i / Li and LFP / i / LLZO-SE / i / LTO full cells, polymer-salt thin films were placed on electrodes along with the addition of (DME) solution (5.97 and 3.98 / zL / cm2on the anodes and cathodes surfaces, respectively) to wet the surfaces. LLZO-SE were sandwiched between thin-film modified LFP cathodes and Li or LTO anodes. The as-assembledAtty. Ref. No. 0073605-001156full cells were sealed in CR2032 coin cells for further characterization. Galvanostatic cycling tests were carried out in the voltage range from 2.7 to 4.0 V vs. Li+ / Li for LFP / i / LLZO-SE / i / Li and 0.6 to 2.8 V vs. Li+ / Li for LFP / i / LLZO-SE / i / LTO cells using a Neware CT-4008 battery testing system. The charging and discharging current densities were determined from the theoretical capacity of LFP cathodes, 170 mAh g '. Electrochemical impedance spectroscopy (EIS, ModuLab XM MTS) measurements were performed in a frequency range of 0.1 to 106Hz with a 10-mV amplitude. Zview was used to analyze obtained spectra and produce equivalent circuit models.

[0163] Method of recovery

[0164] Cycled full cells were opened using a lineman's plier and a diagonal plier. Stainless steel spacers and springs were removed. Full cells were delaminated by soaking in DMF to dissolve polypropylene carbonate and lithium perchlorate that doped in LLZO and polymer-salt films to effectively separate battery components. Recovered components were further soaked in DMF and followed by dimethoxyethane (DME) to remove residuals and contaminants. After being dried at the room temperature overnight under argon environment, recovered components will undergo direct recycling process by assembling a new battery with the incorporation of recovered components.

[0165] References

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[0167] It should be understood that the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points. It should also be appreciated that some components, features, and / or configurations may be described in connection with only one particular embodiment, but these same components, features, and / or configurations can be applied or used with many other embodiments and should be considered applicable to the other embodiments, unless stated otherwise or unless such a component, feature, and / or configurationAtty. Ref. No. 0073605-001156is technically impossible to use with the other embodiment. Thus, the components, features, and / or configurations of the various embodiments can be combined together in any manner and such combinations are expressly contemplated and disclosed by this statement.

[0168] It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible considering the above teachings of the disclosure. The disclosed examples and embodiments are presented for purpose of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof.

[0169] It should be understood that modifications to the embodiments disclosed herein can be made to meet a particular set of design criteria. Therefore, while certain exemplary embodiments of the compositions, materials, apparatuses, and methods of using and making the same disclosed herein have been discussed and illustrated, it is to be distinctly understood that the invention is not limited thereto but may otherwise be variously embodied and practiced within the scope of the following claims.

Claims

Atty. Ref. No. 0073605-001156 WHAT TS CLAIMED IS:

1. A device comprising:an electrochemical cell, comprising:an electrolyte having a first electrolyte interface surface and a second electrolyte interface surface opposite the first electrolyte interface surface;a cathode having a first cathode interface surface and a second cathode interface surface opposite the first cathode interface surface, the first cathode interface surface adjacent the first electrolyte interface surface;an anode having a first anode interface surface and a second anode interface surface opposite the first anode interface surface, the first anode interface surface adjacent the second electrolyte interface surface; anda flexible polymer-salt interfacial layer disposed upon at least one of the first cathode interface surface or the first anode interface surface.

2. The device of claim 1, wherein the electrolyte comprises a Li7-La3-Zr2-O12 (LLZO) solid electrolyte.

3. The device of claim 1, wherein the anode comprises at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode.

4. The device of claim 1, wherein the flexible polymer-salt interfacial layer comprises polypropylene carbonate-lithium bis(fluorosulfonyl)imide (PPC-LiFSI).

5. The device of claim 1, wherein the at least one of the first cathode interface surface or the first anode interface surface having the flexible polymer-salt interfacial layer disposed thereupon further comprises a LiFSI-Dimethyl Ether (LiFSI-DME) solution having a LiFSI molar concentration within a range of approximately IM to 12M.Atty. Ref. No. 0073605-001156 6. The device of claim 1 , wherein the cathode comprises a lithium iron phosphate (LFP) cathode.

7. The device of claim 1, wherein the flexible polymer-salt interfacial layer has an ionic conductivity of approximately 0.0039 Siemens per centimeter (3.9 x 103S / cm ') at a temperature range from approximately 65 to 85 degrees Fahrenheit.

8. A device comprising:an electrode having first electrode interface surface and a second electrode interface surface opposite the first electrode interface surface; anda flexible polymer-salt interfacial layer disposed upon at least one of the first electrode interface surface or the second electrode interface surface.

9. The device of claim 8, wherein the at least one the first electrode interface surface or the second electrode interface surface includes a LiFSI-Dimethyl Ether (LiFSI-DME) solution between the flexible polymer-salt interfacial layer and the at least one of the first electrode interface surface or the second electrode interface surface, wherein the LiFSI-DME solution has a molar concentration of LiFSI within a range of approximately IM to 12M.

10. The device of claim 8, wherein the flexible polymer-salt interfacial layer comprises polypropylene carbonate-lithium bis(fluorosulfonyl)imide (PPC-LiFSI).

11. The device of claim 9, wherein the electrode comprises a lithium iron phosphate (LFP) cathode.

12. The device of claim 9, wherein the electrode comprises at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode.

13. The device of claim 11, wherein the LiFSI-DME solution comprises a quantity within a range of approximately 2 to 8 micro-liters per centimeter squared (uL / cm2).Atty. Ref. No. 0073605-001156 14. The device of claim 12, wherein the LiFSI-DME solution comprises a quantity within a range of approximately 2 to 8 «L / cm2.

15. A method of making an electrode having a flexible polymer-salt interfacial layer, the method comprising:dissolving, in an anhydrous acetonitrile solution, lithium bi(fluorosulfonyl)imide (LiFSI) and polypropylene carbonate (PPC), wherein the dissolving occurs in an inert atmosphere, and wherein the dissolving results in a polymer-salt solution; depositing the polymer-salt solution onto a fdm sheet;storing, at a predetermined temperature, the polymer-salt solution deposited onto the fdm sheet until the polymer-salt solution is dried, resulting in a flexible polymer-salt fdm; separating the flexible polymer-salt fdm from the fdm sheet; andapplying the flexible polymer-salt fdm and a predetermined quantity of a LiFSI-Dimethyl Ether (LiFSI-DME) solution to an interfacial surface of the electrode, wherein the LiFSI- DME solution has a LiFSI molar concentration within a range of approximately IM to 12M.

16. The method of claim 15, wherein the polymer-salt solution comprises a ratio by mass of approximately 12:1:2 of anhydrous acetonitrile solution, lithium bi(fluorosulfonyl)imide (LiFSI), and polypropylene carbonate (PPC), respectively.

17. The method of claim 15, wherein the inert atmosphere comprises at least one of an argon, helium, nitrogen, or anhydrous air atmosphere.

18. The method of claim 15, wherein the predetermined temperature comprises a temperature in the range of approximately 65 degrees to 85 degrees Fahrenheit.Atty. Ref. No. 0073605-001156 19. The method of claim 15, wherein the electrode comprises a lithium iron phosphate (LFP) cathode, and wherein the predetermined quantity of LiFSI-DME solution applied to the interfacial surface of the electrode is within a range of approximately 2 to 8 micro-liters per centimeter squared ( / / L / cm2).

20. The method of claim 15, wherein the electrode comprises at least one of a lithium metal (Li) anode, a lithium titanate (LTO) anode, or a graphite anode, and wherein the predetermined quantity of LiFSI-DME solution applied to the interfacial surface of the electrode is within a range of approximately 2 to 8 «L / cm2.

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