Solid electrolyte separator bonding agent

Abstract

Set forth herein are electrochemical cells which include a negative electrode current collector, a lithium metal negative electrode, an oxide electrolyte membrane, a bonding agent layer, a positive electrode, and a positive electrode current collector. The bonding agent layer advantageously lowers the interfacial impedance of the oxide electrolyte at least at the positive electrode interface and also optionally acts as an adhesive between the solid electrolyte separator and the positive electrode interface. Also set forth herein are methods of making these bonding agent layers including, but not limited to, methods of preparing and depositing precursor solutions which form these bonding agent layers. Set forth herein, additionally, are methods of using these electrochemical cells.

1 . An electrochemical stack, comprising:
 a lithium metal (Li) negative electrode, a positive electrode, an electrolyte separator, and a bonding layer; wherein the bonding layer comprises a lithium salt, a polymer, and a solvent;   wherein the electrolyte separator is in direct contact with the Li metal negative electrode; and   wherein the bonding layer directly contacts, and is positioned between, the electrolyte separator and the positive electrode.   
     
     
         2 . The electrochemical stack of  claim 1 , wherein electrolyte separator is an oxide electrolyte separator. 
     
     
         3 . The electrochemical stack of  claim 1 , wherein the Li negative electrode comprises a layer of Li metal having a thickness from 1 nm to 30 μm in the fully discharged state. 
     
     
         4 . The electrochemical stack of  claim 1 , wherein the Li metal negative electrode comprises a layer of Li metal having a thickness from 1 μm to 50 μm in the fully charged state. 
     
     
         5 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a surface roughness, on at least one surface, from about 0.01 μm to 10 μm. 
     
     
         6 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a surface roughness, on at least one surface, from about 0.01 μm to 5 μm. 
     
     
         7 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a surface roughness, on at least one surface, from about 0.01 μm to 2 μm. 
     
     
         8 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a surface roughness from about 0.1 μm to 10 μm at the surface that interfaces the electrolyte separator and the Li metal negative electrode. 
     
     
         9 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a density greater than 95% of its theoretical density. 
     
     
         10 . The electrochemical stack of  claim 9 , wherein the electrolyte separator has a density greater than 95% of its theoretical density as determined by scanning electron microscopy (SEM). 
     
     
         11 . The electrochemical stack of  claim 9 , wherein the electrolyte separator has a density greater than 95% of its theoretical density as measured by the Archimedes method. 
     
     
         12 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a surface flatness of 0.1 μm to about 50 μm. 
     
     
         13 . The electrochemical stack of  claim 1 , wherein the polymer in the bonding layer is selected from the group consisting of polyacrylonitrile (PAN), polypropylene, polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinyl pyrrolidone (PVP), polyethylene oxide poly(allyl glycidyl ether) PEO-AGE, polyethylene oxide 2-methoxyethoxy)ethyl glycidyl ether (PEO-MEEGE), polyethylene oxide 2-methoxyethoxy)ethyl glycidyl poly(allyl glycidyl ether) (PEO-MEEGE-AGE), polysiloxane, polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), ethylene propylene (EPR), nitrile rubber (NPR), styrene-butadiene-rubber (SBR), polybutadiene polymer, polybutadiene rubber (PB), polyisobutadiene rubber (PIB), polyisoprene rubber (PI), polychloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), polyethyl acrylate (PEA), polyvinylidene fluoride (PVDF), and polyethylene. 
     
     
         14 . The electrochemical stack of  claim 13 , wherein the polymer in the bonding layer is polyacrylonitrile (PAN) or polyvinylidene fluoride hexafluoropropylene (PVDF-HFP). 
     
     
         15 . The electrochemical stack of  claim 13 , wherein the polymer in the bonding layer is selected from the group consisting of PAN, PVDF-HFP, PMMA, PVC, PVP, PEO, and combinations thereof. 
     
     
         16 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is selected from the group consisting of LiPF 6 , LiBOB, LiBETI, LiTFSi, LiBF 4 , LiClO 4 , LiAsF 6 , LiFSI, LiAsF 6 , LiClO 4 , LiI, LiBF 4 , and a combination thereof. 
     
     
         17 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is selected from the group consisting of LiPF 6 , LiBOB, LFTSi, and a combination thereof. 
     
     
         18 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is LiPF 6  at a concentration of 0.5 M to 2 M. 
     
     
         19 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is LiTFSI at a concentration of 0.5 M to 2M. 
     
     
         20 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is LiBF 4  at a concentration of 0.5 M to 2M. 
     
     
         21 . The electrochemical stack of  claim 1 , wherein the lithium salt in the bonding layer is present at a concentration from 0.01 M to 10 M. 
     
     
         22 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is selected from the group consisting of ethylene carbonate (EC), diethylene carbonate or diethyl carbonate (DC), dimethyl carbonate (DMC), ethyl-methyl carbonate (EMC), tetrahydrofuran (THF), γ-Butyrolactone (GBL), fluoroethylene carbonate (FEC), fluoromethyl ethylene carbonate (FMEC), trifluoroethyl methyl carbonate (F-EMC), fluorinated 3-(1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoropropane(F-EPE), fluorinated cyclic carbonate (F-AEC), propylene carbonate (PC), dioxolane, acetonitrile (ACN), succinonitrile, adiponitrile, hexanedinitrile, pentanedinitrile, acetophenone, isophorone, benzonitrile, dimethyl sulfate, prop-1-ene-1,3-sultone (PES), dimethyl sulfoxide (DMSO), ethyl-methyl carbonate, ethyl acetate, methyl butyrate, dimethyl ether (DME), diethyl ether, propylene carbonate, dioxolane, glutaronitrile, gamma butyl-lactone, and combinations thereof. 
     
     
         23 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is a 1:1 w/w mixture of EC:PC. 
     
     
         24 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is a mixture of EC:EMC. 
     
     
         25 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is a mixture of EC:sulfolane. 
     
     
         26 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is a mixture of succinonitrile and glutaronitrile. 
     
     
         27 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer is PES. 
     
     
         28 . The electrochemical stack of  claim 22 , wherein the amount of solvent in the bonding layer is the amount remaining after the bonding layer is dried. 
     
     
         29 . The electrochemical stack of  claim 22 , wherein the amount of solvent in the bonding layer is the minimum amount of solvent required to solvate the lithium salt. 
     
     
         30 . The electrochemical stack of  claim 1 , wherein the bonding layer lowers the interfacial impedance between the electrolyte separator and the positive electrode than it otherwise would be in the absence of the bonding layer. 
     
     
         31 . The electrochemical stack of  claim 1 , wherein the interfacial impedance between the electrolyte separator and the positive electrode is less than 50 Ω·cm 2  at 50° C. 
     
     
         32 . The electrochemical stack of  claim 1 , wherein the interfacial impedance between the electrolyte separator and the positive electrode is less than 25 Ω·cm 2  at 50° C. 
     
     
         33 . The electrochemical stack of  claim 1 , wherein the interfacial impedance between the electrolyte separator and the positive electrode is less than 10 Ω·cm 2  at 50° C. 
     
     
         34 . The electrochemical stack of  claim 1 , wherein the interfacial impedance between the electrolyte separator and the positive electrode is less than 5 Ω·cm 2  at 50° C. 
     
     
         35 . The electrochemical stack of  claim 1 , wherein the positive electrode comprises a lithium intercalation material, a lithium conversion material, or a combination thereof. 
     
     
         36 . The electrochemical stack of  claim 35 , wherein the lithium intercalation material is selected from the group consisting of a nickel manganese cobalt oxide (NMC), a nickel cobalt aluminum oxide (NCA), Li(NiCoAl)O 2 , a lithium cobalt oxide (LCO), a lithium manganese cobalt oxide (LMCO), a lithium nickel manganese cobalt oxide (LMNCO), a lithium nickel manganese oxide (LNMO), Li(NiCoMn)O 2 , LiMn 2 O 4 , LiCoO 2 , LiMn 2-z Ni a O 4 , wherein a is from 0 to 2, or LiMPO 4 , wherein M is Fe, Ni, Co, and Mn. 
     
     
         37 . The electrochemical stack of  claim 36 , wherein the lithium conversion material is selected from the group consisting of FeF 2 , NiF 2 , FeO x F 3-2x , FeF 3 , MnF 3 , CoF 3 , CuF 2  materials, alloys thereof, and combinations thereof. 
     
     
         38 . The electrochemical stack of  claim 1 , wherein the positive electrode further comprises a catholyte. 
     
     
         39 . The electrochemical stack of  claim 38 , wherein the catholyte is a gel electrolyte. 
     
     
         40 . The electrochemical stack of  claim 39 , wherein the positive electrode comprises a gel catholyte which has the same composition as the bonding layer. 
     
     
         41 . The electrochemical stack of  claim 38 , wherein the positive electrode comprises a gel catholyte comprising:
 a solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), methylene carbonate, and combinations thereof;   a polymer selected from the group consisting of PVDF-HFP, PAN, and combinations thereof; and   a salt selected from the group consisting of LiPF 6 , LiBOB, and LFTSi.   
     
     
         42 . The electrochemical stack of  claim 1 , wherein the bonding layer is a phase inversion gel electrolyte. 
     
     
         43 . The electrochemical stack of  claim 1 , wherein the positive electrode comprises a phase-inversion gel catholyte. 
     
     
         44 . The electrochemical stack of  claim 38 , wherein the positive electrode comprises a phase inversion gel catholyte comprising:
 a polymer selected from the group consisting of PVDF-HFP and PAN;   a non-solvent selected from toluene, acetone, and combination thereof; and   a salt selected from the group consisting of LiPF 6 , LiBOB, and LFTSi.   
     
     
         45 . The electrochemical stack of  claim 1 , wherein the positive electrode further comprises a binder selected from the group consisting of polypropylene (PP), atactic polypropylene (aPP), isotactic polypropylene (iPP), ethylene propylene rubber (EPR), ethylene pentene copolymer (EPC), polyethylene oxide (PEO), PEO block copolymers, polyethylene glycol, polyisobutylene (PIB), styrene butadiene rubber (SBR), a polyolefin, polyethylene-co-poly-1-octene (PE-co-PO) copolymer, PE-co-poly(methylene cyclopentane) (PE-co-PMCP) copolymer, stereoblock polypropylenes, polypropylene polymethylpentene copolymer, acrylics, acrylates, polyvinyl butyral, vinyl polymers, cellulose polymers, resins, polyvinyl alcohol, polymethyl methacrylate, polyvinyl pyrrolidone, polyacrylamide, silicone, PVDF, PVDF-HFP, PAN, and combinations thereof. 
     
     
         46 . The electrochemical stack of  claim 1 , wherein the positive electrode comprises an electronically conductive source of carbon. 
     
     
         47 . The electrochemical stack of  claim 1 , wherein the positive electrode comprises a solid catholyte and either a lithium intercalation material or a lithium conversion material; wherein each of the catholyte, lithium intercalation material or a lithium conversion material independently has a d 50  particle size from about 0.1 μm to 5 μm. 
     
     
         48 . The electrochemical stack of  claim 1 , wherein the electrolyte separator is selected from the group consisting of a lithium-stuffed garnet, a sulfide electrolyte doped with oxygen, a sulfide electrolyte comprising oxygen, a lithium aluminum titanium oxide, a lithium aluminum titanium phosphate, a lithium aluminum germanium phosphate, a lithium aluminum titanium oxy-phosphate, a lithium lanthanum titanium oxide perovskite, a lithium lanthanum tantalum oxide perovskite, a lithium lanthanum titanium oxide perovskite, an antiperovskite, a LISICON, a LI—S—O—N, lithium aluminum silicon oxide , a Thio-LISICON, a lithium-substituted NASICON, a LIPON, or a combination, mixture, or multilayer thereof. 
     
     
         49 . The electrochemical stack of  claim 48 , wherein the electrolyte separator is lithium lanthanum titanium oxide characterized by the empirical formula, Li 3x La 2/3-x TiO 3 , wherein x is a rational number from 0 to 2/3. 
     
     
         50 . The electrochemical stack of  claim 48 , wherein the electrolyte separator is lithium lanthanum titanium oxide characterized by the empirical formula, Li 3x La 2/3-x Ti j Ta k O 3 , wherein x is a rational number from 0 to 2/3, and wherein subscripts j+k=1, and j and k, independently in each instance, are a rational number from 0 to 1. 
     
     
         51 . The electrochemical stack of  claim 48 , wherein the electrolyte separator is lithium lanthanum titanium oxide characterized by a perovskite crystal structure. 
     
     
         52 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is an antiperovskite characterized by the empirical formula, Li 3 OX wherein X is Cl, Br, or combinations thereof. 
     
     
         53 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is LISICON characterized by the empirical formula, Li(Me′ x ,Me″ y )(PO 4 ) wherein Me′ and Me″ are selected from Si, Ge, Sn or combinations thereof; and wherein 0≦x≦1; wherein 0≦y≦1, and wherein x+y=1. 
     
     
         54 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is thio-LISICON characterized by the empirical formula, Li 3.25 Ge 0.25 P 0.75 S 4 . 
     
     
         55 . The electrochemical stack of  claim 48 , wherein the electrolyte separator is thio-LISICON characterized by the empirical formula, Li 4-x M 1-x P x S 4  or Li 10 MP 2 S 12 , wherein M is selected from Si, Ge, Sn, or combinations thereof; and wherein 0≦x≦1. 
     
     
         56 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is lithium aluminum titanium phosphate characterized by the empirical formula, Li 1+a Al b Ti 2−c (PO 4 ), wherein 0≦a≦2; 0≦b≦2; and 0≦c≦2. 
     
     
         57 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is lithium aluminum germanium phosphate characterized by the empirical formula, Li 1.5 Al 0.5 Ge 1.5 (PO 4 ). 
     
     
         58 . The electrochemical stack of  claim 42 , wherein the electrolyte separator is LI—S—O—N characterized by the empirical formula, Li x S y O z N w , wherein x, y, z, and w, are each, independently, a rational number from 0.01 to 1. 
     
     
         59 . The electrochemical stack of  claim 1 , wherein the electrolyte separator is characterized by the empirical formula Li x La 3 Zr 2 O h +yAl 2 O 3 , wherein 3≦x≦8, 0≦y≦1, and 6≦h≦15; and wherein subscripts x and h, and coefficient y is selected so that the electrolyte separator is charge neutral. 
     
     
         60 . The electrochemical stack of  claim 59 , wherein the electrolyte separator is doped with Ga, Nb, or Ta. 
     
     
         61 . The electrochemical stack of  claim 1 , wherein the electrolyte separator isolates the positive electrode from the negative electrode. 
     
     
         62 . The electrochemical stack of  claim 1 , wherein the electrolyte separator physically decouples the positive electrode from the negative electrode. 
     
     
         63 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has a top or bottom surface that has less than 5 atomic % of an amorphous material comprising carbon and oxygen. 
     
     
         64 . The electrochemical stack of  claim 63 , wherein the amorphous material is lithium carbonate, lithium hydroxide, lithium oxide, lithium peroxide, a hydrate thereof, an oxide thereof, or a combination thereof. 
     
     
         65 . The electrochemical stack of  claim 1 , wherein the bonding layer is characterized by a thickness of about 1 nm to about 5 μm. 
     
     
         66 . The electrochemical stack of  claim 1 , wherein the Li negative electrode is characterized by a thickness of about 10 nm to about 50 μm. 
     
     
         67 . The electrochemical stack of  claim 1 , wherein the oxide separator is characterized by a thickness of about 0.1 μm to about 100 μm. 
     
     
         68 . The electrochemical stack of  claim 1 , wherein the oxide separator is characterized by a thickness of about 10 μm to about 50 μm. 
     
     
         69 . The electrochemical stack of  claim 1 , wherein the bonding layer penetrates into the positive electrode. 
     
     
         70 . The electrochemical stack of  claim 1 , wherein the bonding layer penetrates into the positive electrode at least 10% of the thickness of the positive electrode. 
     
     
         71 . The electrochemical stack of  claim 1 , wherein the bonding layer contacts the catholyte in the positive electrode. 
     
     
         72 . The electrochemical stack of  claim 1 , wherein the bonding layer does not creep around the electrolyte separator. 
     
     
         73 . The electrochemical stack of  claim 1 , wherein the bonding layer does not comprise components which volatilize and diffuse around the electrolyte separator to contact the Li metal negative electrode. 
     
     
         74 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer have a vapor pressure less than about 80 Torr at 20° C. 
     
     
         75 . The electrochemical stack of  claim 1 , wherein the solvent in the bonding layer has a boiling point above 80° C. at one atmosphere. 
     
     
         76 . The electrochemical stack of  claim 1 , wherein the electrolyte separator is free of pin-holes. 
     
     
         77 . The electrochemical stack of  claim 1 , wherein the electrolyte separator is free of surface defects. 
     
     
         78 . The electrochemical stack of  claim 1 , wherein diameter of the electrolyte separator is greater than the diameter of the lithium metal negative electrode. 
     
     
         79 . The electrochemical stack of  claim 1 , wherein diameter of the electrolyte separator is greater than the diameter of the positive electrode. 
     
     
         80 . The electrochemical stack of  claim 1 , wherein width or diameter of the electrolyte separator is greater than either of the width or diameter, respectively, of the lithium metal negative electrode or of the positive electrode. 
     
     
         81 . The electrochemical stack of  claim 1 , wherein width or diameter of the electrolyte separator is greater than the width or diameter, respectively, of the lithium metal negative electrode. 
     
     
         82 . The electrochemical stack of  claim 1 , wherein width or diameter of the electrolyte separator is greater than the width or diameter, respectively, of the positive electrode. 
     
     
         83 . The electrochemical stack of  claim 1 , wherein width or diameter of the electrolyte separator is greater than both the width and diameter, respectively, of the lithium metal negative electrode and positive electrode. 
     
     
         84 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has raised edges which protect the bonding layer, or its constituent components, from creeping around the electrolyte separator. 
     
     
         85 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has coated edges which protect the bonding layer from contacting the Li metal negative electrode. 
     
     
         86 . The electrochemical stack of  claim 85 , wherein the coated edges comprise a coating selected from parylene, polypropylene, polyethylene, alumina, Al 2 O 3 , ZrO 2 , TiO 2 , SiO 2 , a binary oxide, La 2 Zr 2 O 7 , a lithium carbonate species, or a glass, wherein the glass is selected from SiO 2 —B 2 O 3 , or Al 2 O 3 . 
     
     
         87 . The electrochemical stack of  claim 1 , wherein the electrolyte separator has tapered edges which protect the bonding layer from creeping around the electrolyte separator. 
     
     
         88 . The electrochemical stack of  claim 1 , wherein
 the electrolyte separator has a thickness between about 10 nm and 50 μm;   the bonding layer has a thickness between about 1 μm and 20 μm; and   the positive electrode, exclusive of the current collector, has a thickness between about 5 μm and 150 μm.   
     
     
         89 . A free standing film comprising a spin-coated gel electrolyte, wherein the phase inversion gel electrolyte comprises a lithium salt, a polymer, and a solvent; and
 wherein the phase inversion gel electrolyte has a porosity of at least 20%.   
     
     
         90 - 100 . (canceled) 
     
     
         101 . A free standing film comprising a phase inversion gel electrolyte,
 wherein the phase-inversion gel electrolyte comprises a lithium salt, a solvent, and a polymer and   wherein the phase inversion gel electrolyte has a porosity of at least 20%.   
     
     
         102 - 112 . (canceled) 
     
     
         113 . A method of making an electrochemical device, comprising,
 providing a positive electrode,   providing a free standing film as set forth in  claim 101 ;   bonding, adhering, or laminating the free standing film to the positive electrode to form a composite;   providing a lithium metal negative electrode; and   bonding, adhering, or laminating the lithium metal negative electrode to the composite, thereby making an electrochemical device.   
     
     
         114 . The electrochemical stack of  claim 1 , wherein the electrolyte separator protects the Li metal negative electrode from exposure to the polymer or to the solvent in the bonding layer. 
     
     
         115 . The electrochemical stack of  claim 48 , wherein the electrolyte separator is Li 4−x Ge 1−x P x S 4  where 0.2≦x≦0.8. 
     
     
         116 . An electrochemical stack, comprising:
 a lithium metal (Li) negative electrode, a positive electrode, an electrolyte separator, and a bonding layer comprising a lithium salt, a polymer, and a solvent;   wherein the electrolyte separator is in direct contact with the Li metal negative electrode;   wherein the bonding layer directly contacts, and is positioned between, the electrolyte separator and the positive electrode; and   wherein the bonding layer is disposed on the side of the electrolyte separator not in contact with the Li metal negative electrode.   
     
     
         117 . (canceled) 
     
     
         118 . An electrochemical stack, comprising:
 a lithium metal (Li) negative electrode, a positive electrode, a sulfide electrolyte separator, and a bonding layer; wherein the bonding layer comprises a lithium salt, a polymer, and a solvent;   wherein the electrolyte separator is in direct contact with the Li metal negative electrode; and   wherein the bonding layer directly contacts, and is positioned between, the electrolyte separator and the positive electrode.   
     
     
         119 . An electrochemical stack, comprising:
 a lithium metal (Li) negative electrode, a positive electrode, a borohydride electrolyte separator, and a bonding layer; wherein the bonding layer comprises a lithium salt, a polymer, and a solvent;   wherein the borohydride electrolyte separator is in direct contact with the Li metal negative electrode; and   wherein the bonding layer directly contacts, and is positioned between, the borohydride electrolyte separator and the positive electrode.