Multilayer solid electrolytes and batteries containing them

Abstract

The present invention relates to a multilayer solid electrolyte for Li and Na-ion batteries, which comprises a dual conducting layer, more specifically an ionically and electronically conducting layer in combination with an ionically conducting and electronically insulating layer. The present invention also relates to a method for its preparation and to a solid-state battery comprising said multilayer solid electrolyte.

Description

[Technical field]

[0001] The present invention relates to the field of solid electrolytes, and more particularly to solid electrolytes used in lithium and sodium metal batteries. The present invention also relates to the field of lithium and sodium batteries that include a solid electrolyte. [Background technology]

[0002] Solid-state batteries (SSBs) are a promising electrochemical energy storage technology for power devices in modern society. It is believed that solid electrolytes can provide a real leap in energy density using lithium-metal anodes compared to conventional Li-ion batteries (LIBs). However, there is still a long way to go for practical application of SSBs. The growth and propagation of lithium dendrites from the Li metal anode to the positive electrode remains a problem, even with the use of solid electrolytes (Nature Energy, https: / / www.nature.com / articles / nenergy2016141; R. Chen, et al., Chem. Rev., 2020, 120, 6820-6877).

[0003] Lithium propagation occurs from the Li metal to the positive electrode, and the propagation of Li dendrites connects both sides, shorting the battery and limiting its shelf life. Lithium propagation through the solid electrolyte can be attributed to non-uniform electrodeposition of lithium at the Li metal electrode, which is probably due to the existence of non-uniform current density distribution at the Li metal-solid electrolyte interface due to non-uniform contact between these components.

[0004] The mechanism of dendrite growth is not fully understood, but it is known that the interface between Li metal and the solid electrolyte (SE) is a key factor. The uneven contact between Li metal and the SE is responsible for the uneven current density distribution along the surface of the electrode, and thus contributes to preferential spots for Li electroplating where Li metal accumulates and propagates through the thickness of the electrolyte towards the positive electrode. Dendrites are more likely to form at higher currents (i.e., more rapid charging / discharging of the battery) and at higher areal capacity loadings (i.e., a greater amount of lithium is plated and stripped by the surface area).

[0005] Dendrite propagation has been observed in solid-state batteries that use both polymer and inorganic solid electrolytes.

[0006] In view of this, several efforts have been made to reduce dendrite formation and improve and homogenize the current density at the Li metal-solid electrolyte interface.

[0007] Luhan Ye et al. (Nature, 2021, 593, 218-222) describe a cell structure for Li-metal batteries containing a multilayer electrolyte formed by the sequence graphite-LPSCl-LGPS-LPSCI-graphite. The central LGPS layer has the formula Li 10 Ge1P2S 12 while the LPSCl layer has the formula Li 5.5 P.S. 4.5 Cl 1.5The solid electrolyte is a 100% ZnO-based LGPS / LPSCI solid electrolyte. By using the multilayer sequence graphite-LPSCl-LGPS-LPSCI-graphite in a symmetric battery, it has been shown that the battery can be cycled at very high current densities (20 mA / cm2) and low overpotentials without any significant signs of short circuiting. The LPSCl layer stabilizes the primary interface to the Li / graphite layer and helps to lower the overall overpotential, allowing practical cycling at high current densities, while the central LGPS layer exhibits an effect similar to an expanded screw effect (derived from forced decomposition acting as a self-repairing concrete that fills and repairs micrometer-sized cracks) and reduces Li dendrite formation.

[0008] Alemayehu et al., (Nanoscale, 2018, 10, 6125-6138) aim to minimize the formation of lithium dendrites and achieve uniform lithium deposition in anode-free lithium-metal batteries. To this end, they disclose the use of a copper electrode coated with a polyethylene oxide (PEO) film in combination with an electrolyte made from a mixture of LiTFSI, 1,2-dimethoxyethane / 1,3-dioxolane (DME / DOL) and LiNO3, and a cathode of LiFePO4 or LiCoO2.

[0009] The PEO membrane coating has been shown to enhance lithium cycling and inhibit dendrite formation by hosting the deposited lithium and preventing it from coming into excessive contact with the electrolyte. The interaction of the lithium ions with the polar surface of the PEO membrane coating provides good interfacial compatibility and controls the flow of lithium ions during cycling.

[0010] On the other hand, polyethylene oxide is also widely used as a solid polymer electrolyte in lithium-metal batteries. This polymer has ionic conductivity, which, when lowered to temperatures below 65°C, mainly contributes to the transition from amorphous to crystalline structure. Therefore, PEO is used in combination with lithium salts with very large counterions that interfere with the crystallization process, and in combination with ceramic or oxide nanoparticles that act as effective cross-linking centers for the PEO segments, thus reducing the reorganization of the polymer chains and promoting localized amorphous regions.

[0011] Carbon additives have also been used in PEO electrolytes to improve the ionic conductivity and enhance amorphization of such polymers. However, due to the electronic conductivity of these compounds, they are less suitable as solid electrolytes, since electrical conduction across the electrolyte induces short circuits. For example, the electrical conductivity of carbon nanotubes (CNTs) and the risk of battery short circuits limit the application of these carbon additives in the field of polymer electrolytes. For this reason, several attempts have been made to reduce the aforementioned electronic conductivity.

[0012] Ahn et al., (Metals and Materials International, 2006, 12(1), 69-73) describe the use of small and well-dispersed multi-walled carbon nanotubes (MWCNTs) in a PEO-LiClO4 electrolyte. The small amount avoids direct electrical conduction across the electrolyte. In fact, they conclude that MWCNTs are more effective than oxide nanoparticles in terms of enhancing polymer chain disorder and localized amorphization, and therefore that the PEO-LiClO4-MWCNT combination in the electrolyte increases ionic conductivity by promoting the amorphous state mentioned above.

[0013] Tang et al., (Nano Letters, 2012, 12, 1152-1156) describe the use of hybrid nanofillers, in particular based on carbon nanotubes made of montmorillonite, incorporated into PEO electrolytes, encapsulated within insulating clay layers. These nanofillers not only increase the lithium ion conductivity of the PEO electrolyte and improve the mechanical properties of the polymer, but also eliminate the risk of electrical short circuits, as the electrical conduction of the carbon nanotubes is blocked by the clay plates connected to the CNTs.

[0014] Despite the different proposals made in the art, there remains a need to provide a battery including a solid electrolyte with enhanced conductive properties while reducing dendrite formation and improving the Li metal-solid electrolyte interface. Summary of the Invention

[0015] The inventors have shown that the use of a layer with dual conductivity (ionic and electronic) in an electrolyte that also has a purely ionically conductive layer can prevent or at least reduce the growth of lithium dendrites and lower the internal resistance in Li metal solid-state batteries.

[0016] This layer, with dual conducting properties, is placed in contact with the Li metal of the anode and acts as a buffer layer for the dendrite growth, homogenizing the current distribution thanks to its electrical properties. In fact, the electronic conductivity of the dual conducting layer improves the distribution of the current density at the interface between the Li metal anode and the above-mentioned electrolyte layer, thus blocking the lithium dendrite growth and its propagation through the other electrolyte layer (pure ionically conducting layer).

[0017] Experimental results provided herein show that, in contrast to lithium batteries having an ionically conductive layer as the only component of the electrolyte, the electrolyte of the present invention can withstand full rate capability with currents from 0.05C up to 4C and back to 0.1C without evidence of dendrite formation. Furthermore, all cells containing the electrolyte layer exhibit higher discharge capacity values ​​at high currents. The same is expected for Na metal batteries.

[0018] Thus, a first aspect of the present invention is a multilayer solid electrolyte for Li-ion and Na-ion batteries, the electrolyte comprising: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or -refers to a multi-layer solid electrolyte comprising an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive.

[0019] A second aspect of the present invention relates to a method for obtaining a multilayer solid electrolyte, the method comprising the steps of: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or providing an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or providing an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive; and c) disposing the ionically and electronically conductive layer provided in step b) on top of the ionically conductive and electronically insulating layer provided in step a).

[0020] Another aspect of the present invention relates to an electrochemical Na-ion or Li-ion or Na-metal or Li-metal cell or Na-ion or Li-ion or Na-metal or Li-metal battery comprising the multilayer solid electrolyte as defined above. [Brief description of the drawings]

[0021] [Figure 1] Schematic diagram of two setups used to test the stripping plating capability of solid electrolytes: a) symmetric Li metal cell; b) full Li metal cell. [Diagram 2] Stripping plating tests of symmetric cells containing solid electrolyte layer 1 (a, b) and layers 1 and 2 (c). Tests were performed at 0.2 and 0.5 mAh cm-2 for the former and at 0.5 mAh cm-2 for the latter. Rate capabilities were investigated from 0.05 C up to 4 C. [Diagram 3] Schematic diagram of cell 1 and cell 2 (left) and the discharge capacity of the cells at rates from C / 20 up to 2C. [Figure 4] Electrochemical impedance spectroscopy plots of Li metal symmetric cells with layer 1 (cell 1) and layer 2 (cell 2) measured at RT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] As mentioned above, a first aspect of the present invention is a multi-layer solid electrolyte for Li-ion and Na-ion batteries, the electrolyte comprising: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or -refers to a multi-layer solid electrolyte comprising an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive.

[0023] The ionically conductive and electronically insulating layer (a) and the ionically conductive and electronically conductive layer (b) are also referred to in this document as Layer 1 and Layer 2, respectively.

[0024] In the context of the present invention, "multilayer" is used as a general term to encompass structures that include at least a first layer that is partially or completely covered or coated by at least another layer. Thus, in its simplest form, a multilayer is a bilayer.

[0025] In a preferred embodiment, the multilayer solid electrolyte is for a Li-ion battery, the electrolyte comprising: a) an ionically conductive and electronically insulating layer, an ion-conducting polymer and at least a lithium salt, or an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt, and an electronically conductive additive, or an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive.

[0026] In a particular embodiment, the ionically conductive and electronically insulating layer (a) comprises an ionically conductive polymer and at least a lithium or sodium salt, and in a more particular embodiment, the ionically conductive and electronically insulating layer (a) comprises an ionically conductive polymer and at least a lithium salt.

[0027] In another particular embodiment, the ionically conductive and electronically insulating layer (a) comprises a mixture of an ionically conductive polymer and a lithium or sodium salt, and in a more particular embodiment, the ionically conductive and electronically insulating layer (a) comprises a mixture of an ionically conductive polymer and a lithium salt.

[0028] Non-limiting examples of the above-mentioned ion-conducting polymers are polyethylene oxide (PEO) derivatives, polypropylene oxide (PPO) derivatives, polytetrahydrofuran (polyTHF) derivatives, polyvinylidene fluoride (PVDF), and polymers containing ionically dissociable groups. Combinations comprising at least one of the above may also be used.

[0029] More preferably, the ion-conducting polymer is an ion-conducting polymer having an alkylene oxide-based segment.

[0030] As used herein, the phrase "ion-conducting polymer having alkylene oxide-based segments" refers to an ion-conducting polymer having alkylene oxide chain structural units in alternating arrangement of alkylene groups and ether oxygen groups.

[0031] The alkylene oxide chain structural unit may be included in the main chain of the ion-conducting polymer or may be included in the ion-conducting polymer in a grafted form. For example, the alkylene oxide chain structural unit may be an alkylene oxide chain structural unit having 8 to 500,000 carbon atoms, for example, 40 to 250,000 carbon atoms. In some embodiments, the alkylene oxide chain structural unit may be branched or have a comb-like structure.

[0032] The ion-conducting polymer may include a siloxane-based polymer or an acrylate-based polymer, a poly(alkene-alt-maleic anhydride) polymer connected to an alkylene oxide-based polymer. The ion-conducting polymer may include at least one selected from an alkylene oxide-based polymer blend, a siloxane-based polymer blend, and an acrylate-based polymer blend poly(alkene-alt-maleic anhydride) polymer.

[0033] In certain embodiments, the ion-conducting polymer may be at least one selected from polyethylene oxide (PEO), polypropylene oxide (PPO), polybutylene oxide (PBO), PEO-PPO blends, PEO-PBO blends, PEO-PPO-PBO blends, PEO-PPO block copolymers, PEO-PBO block copolymers, PEO-PPO-PBO block copolymers, PBO-PEO-PBO block copolymers, PEO-PBO-PEO block copolymers, PEO-grafted polymethylmethacrylate (PMMA), PPO-grafted PMMA, and PBO-grafted PMMA, PEO / PPO-grafted poly(alkene-alternating-maleic anhydride) polymers.

[0034] More specifically, the ion-conducting polymer may be at least one selected from PEO, PPO, PEO / PPO grafted poly(alkene-alternating-maleic anhydride) polymer, PEO-PPO blend, PEO-PPO block copolymer, PEO-PPO-PEO block copolymer and polystyrene-PEO block polymer. In the most preferred embodiment, the ion-conducting polymer is PEO.

[0035] The ion-conducting polymer may have a weight average molecular weight (Mw) of about 100,000 Daltons to about 7.000.000 Daltons. The weight average molecular weight (Mw) of the ion-conducting polymer may be, for example, about 200.000 Daltons to about 7.000.000 Daltons, for example, about 300.000 Daltons to about 5.000.000 Daltons. An ion-conducting polymer having a weight average molecular weight (Mw) within the above range has a suitable chain length (i.e., a suitable degree of polymerization) and may therefore have enhanced ion conductivity at room temperature. However, the weight average molecular weight (Mw) of the ion-conducting polymer is not particularly limited to the above range and may be within any range that enhances the ion conductivity of the electrolyte composition or exhibits the acquisition of mechanical properties.

[0036] Regarding the lithium salt, any lithium salt may be used in the present invention, however, lithium salts having good ionic conductivity due to low lattice energy (i.e., high degree of dissociation), as well as high thermal stability and oxidation resistance are preferred.

[0037] Examples of lithium salts that can be used in the present invention include, but are not limited to, lithium tetrafluoroborate LiBF4, lithium hexafluorophosphate LiPF6, lithium hexafluoroarsenate LiAsF6, lithium iodide LiI, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(trifluoromethanesulfonyl)imide Li[(CF3SO2)2N], lithium bis(perfluoroethylsulfonyl)imide Li[(CF3CF2SO2)2N], Li[(C2F5SO2)2N], lithium bis(fluorosulfonyl)imide Li[(FSO2)2N], lithium(trifluoromethanesulfonyl) ... Lithium (perfluoroethylsulfonyl)(fluorosulfonyl)imide Li[(CF3SO2)(FSO2)N], Li[(FSO2)(C4F9SO2)N], lithium (perfluoroethylsulfonyl)(fluorosulfonyl)imide Li[(FSO2)(CF3CF2SO2)N], lithium perchlorate LiClO4, lithium bis(oxalato)borate LiB(C2O4)2, lithium oxalatodifluoroborate Li[BF2C2O4], the lithium salt of 4,5-dicyano-1,2,3-triazole, the lithium salt of 4,5-dicyano-2-trifluoromethyl-imidazole, the lithium salt of 4,5-dicyano-2-pentafluoroethyl-imidazole, or a mixture thereof.

[0038] In a preferred embodiment, the lithium salt is selected from lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(trifluoromethanesulfonyl)imide Li[(CF3SO2)2N], lithium bis(perfluoroethylsulfonyl)imide Li[(CF3CF2SO2)2N], lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide Li[(CF3SO2)(FSO2)N], Li[(C2F5SO2)2N], lithium bis(fluorosulfonyl)imide Li[(FSO2)2N], Li[(FSO2)(C4F9SO2)N] and lithium (perfluoroethylsulfonyl)(fluorosulfonyl)imide Li[(FSO2)(CF3CF2SO2)N]. Even more preferably, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide Li[(CFSO)N] or lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide Li[(CFSO)(FSO)N], and most preferably the lithium salt is bis(trifluoromethanesulfonyl)imide Li[(CFSO)N].

[0039] In a preferred embodiment, the ionically conductive and electronically insulating layer (a) comprises an ion-conducting polymer selected from PEO, PPO, PEO / PPO grafted poly(alkene-alternating-maleic anhydride) polymers, PEO-PPO blends, PEO-PPO block copolymers, and PEO-PPO-PEO block copolymers and polystyrene-PEO block polymers; and at least one lithium salt selected from LiCF3SO3, Li[(CF3SO2)2N], Li[(CF3CF2SO2)2N], Li[(CF3SO2)(FSO2)N], Li[(C2F5SO2)2N], Li[(FSO2)2N], Li[(FSO2)(C4F9SO2)N] and Li[(FSO2)(CF3CF2SO2)N].

[0040] In a most preferred embodiment, the ionically conductive and electronically insulating layer (a) comprises -PEO as an ion-conducting polymer; - a lithium salt selected from Li[(CF3SO2)2N] and Li[(CF3SO2)(FSO2)N].

[0041] In yet a most preferred embodiment, the ion-conducting polymer is PEO and the lithium salt is bis(trifluoromethanesulfonyl)imide Li[(CF3SO2)2N].

[0042] In another particular embodiment, the molar ratio of the lithium salt to the ion-conducting polymer is from 1:10 to 1:30, more preferably from 1:15 to 1:25, and even more preferably 1:20.

[0043] As mentioned above, the multilayer electrolyte of the present invention can also be implemented in a sodium-ion battery. In this particular case, as is required for the lithium salt, the sodium salt is preferably one that has good ionic conductivity (i.e. a high degree of dissociation) as well as high thermal stability and oxidation resistance.

[0044] Examples of sodium salts that can be used in the present invention include, but are not limited to, Na[R 1 SO2NSO2R 2 ] (where R 1 and R 2 are independently selected from fluorine or fluoroalkyl groups) NaCF3SO3, NaC(CN)3, NaB(C2O4)2 and NaBF2(C2O4), NaSbF6, NaAsF6, NaBF4, NaClO4, NaPF6, and mixtures thereof.

[0045] In a preferred embodiment, the sodium salt is Na[R 1 SO2NSO2R 2 ], where R 1 and R 2 are independently selected from F and CF3, more preferably both are F or both are CF3. 1 and R 2When R are both F, the resulting anion is a bis(fluorosulfonyl)imide anion (also called the "FSI anion"). 1 and R 2 When both are CF3, the resulting anion is the bis(trifluoromethylsulfonyl)imide anion (also called the "TFSI anion"). Thus, the use of NaFSI or NaTFSI is preferred.

[0046] In another particular embodiment, the ionically conductive and electronically insulating layer comprises an inorganic solid material.

[0047] The above-mentioned inorganic solid materials are ceramics, such as garnets, more particularly cubic garnets, such as Li7La3Zr2O 12 , or for example β-alumina, for example Li-β-alumina; perovskites, for example Li 3.3 La 0.56 TiO3; argyrodites, e.g., Li6PS5Cl; sulfides, e.g., Li2S-P2S5; hydrides, e.g., LiBH4; halides, e.g., LiI; NASICON, e.g., LiTi2(PO4)3, Li3Zr2(SiO4)2(PO4); LISICON, e.g., Li14Zn(GeO4)4; borates, e.g., Li2B4O7; and phosphates, e.g., Li3PO4, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li 1.3 Al 0.3 Ge 1.7 (PO4)3. The inorganic solid material preferably comprises or is made from a garnet, more preferably a lithium garnet.

[0048] Examples of lithium garnets include Li5 phase lithium garnets, such as Li5La3M 1 2O 12 (where M 1 is Nb, Zr, Ta, Sb, or a combination thereof); Li6 phase lithium garnet, e.g., Li6DLa2M3 2O 12 (wherein D is Mg, Ca, Sr, Ba, or a combination thereof; M 3 is Nb, Ta, or a combination thereof); and Li7 phase lithium garnets, e.g., cubic Li7La3Zr2O 12 and Li7Y3Zr2O 12 Examples include:

[0049] In a particular embodiment, the ionically and electronically conductive layer (b) comprises an ionically conductive polymer, at least a lithium or sodium salt, and an electronically conductive additive. In a more particular embodiment, the ionically and electronically conductive layer (b) comprises an ionically conductive polymer, at least a lithium salt, and an electronically conductive additive.

[0050] In another specific embodiment, the ionically and electronically conductive layer (b) comprises a mixture of an ionically conductive polymer, a lithium or sodium salt, and an electronically conductive additive. In a more specific embodiment, the ionically and electronically conductive layer (b) comprises a mixture of an ionically conductive polymer, a lithium salt, and an electronically conductive additive.

[0051] Any of the ionically conductive polymers, lithium salts and sodium salts described above for the ionically conductive and electronically insulating layer may also be applied to the ionically conductive and electronically conductive layer (b), including specific and preferred embodiments.

[0052] In another particular embodiment, the ionically and electronically conductive layer (b) comprises an inorganic solid material and an electronically conductive additive.

[0053] Any of the inorganic solid materials mentioned above for the ionically conductive and electronically insulating layer may also be applied to the ionically and electronically conductive layer (b), including specific and preferred embodiments.

[0054] With regard to the electronic conductive additive, non-limiting examples thereof include any conductive carbon such as carbon, graphite, graphite powder, graphite powder flakes, graphite powder spheroids, carbon black, activated carbon, conductive carbon, amorphous carbon, glassy carbon, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphene, or any combination thereof. More preferably, the use of single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0055] In some embodiments, the electronically conductive additive can have a particle size ranging from about 1 to about 50 microns, or from about 2 to about 30 microns, or from about 5 to about 15 microns.

[0056] The amount of electronically conductive additive may be as low as 0.1 wt % or as high as is possible to process layer (b). In certain embodiments, the total weight percentage of electronically conductive additive in electrolyte layer (b) may range from about 5 wt % to 20 wt %, more preferably 5 to 10 wt %, with the weight percentages being given in terms of the total weight of electrolyte layer (b).

[0057] In a preferred embodiment, the ionically and electronically conductive layer (b) comprises an ion-conducting polymer selected from PEO, PPO, PEO / PPO grafted poly(alkene-alternating-maleic anhydride) polymers, PEO-PPO blends, PEO-PPO block copolymers, and PEO-PPO-PEO block copolymers and polystyrene-PEO block polymers; - a lithium salt selected from LiCF3SO3, Li[(CF3SO2)2N], Li[(CF3CF2SO2)2N], Li[(CF3SO2)(FSO2)N], Li[(C2F5SO2)2N], Li[(FSO2)2N], Li[(FSO2)(C4F9SO2)N] and Li[(FSO2)(CF3CF2SO2)N], an electronically conductive additive selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and graphite.

[0058] In a most preferred embodiment, the ionically and electronically conductive layer (b) comprises -PEO as an ion-conducting polymer; a lithium salt selected from Li[(CF3SO2)2N] and Li[(CF3SO2)(FSO2)N]; an electronically conductive additive selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphite, and carbon black.

[0059] Within this preferred embodiment, the molar ratio of lithium salt to PEO conductive polymer may vary from 1:10 to 1:30, more preferably from 1:15 to 1:25, and even more preferably is 1:20.

[0060] Also in this preferred embodiment, the electronically conductive additive may be present in a weight percentage ranging from 5 to 10 weight % in terms of the total weight of the ionically and electronically conductive layer (b).

[0061] A second aspect of the present invention relates to a method for preparing a solid electrolyte as defined above, said method comprising the steps of: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or providing an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or providing an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive; and c) disposing the ionically and electronically conductive layer provided in step b) on top of the ionically conductive and electronically insulating layer provided in step a).

[0062] In a particular embodiment, step a) of the method of the invention consists of providing an ionically conductive and electronically insulating layer comprising an ionically conductive polymer and a lithium or sodium salt.

[0063] Within this particular embodiment, at least one lithium or sodium salt and the ion-conducting polymer may be dissolved in a common volatile solvent.

[0064] Examples of volatile solvents include, but are not limited to, methanol, ethanol, isopropanol, acetone, methyl-ethyl-ketone, acetonitrile, ethyl acetate, methyl or ethyl formate, dichloromethane. A person skilled in the art will be able to select a solvent or solvent mixture according to the best properties required for the final product.

[0065] In certain embodiments, the molar ratio of lithium or sodium salt to ion-conducting polymer ranges from 1:10 to 1:30, more preferably from 1:15 to 1:25, and even more preferably is 1:20.

[0066] The resulting solution is viscous and may be poured onto a substrate (e.g., a Teflon plate) followed by evaporation of the solvent. An electrolyte layer or film with controlled thickness can be obtained by any method known to those skilled in the art, such as hot pressing the as-obtained Li or Na salt / polymer mixture.

[0067] In a preferred embodiment, step a) provides an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or - an inorganic solid material.

[0068] More preferably, step a) provides an ionically conductive and electronically insulating layer comprising an ionically conductive polymer and at least a lithium salt.

[0069] In another particular embodiment, step b) of the method of the invention consists of providing an ionically and electronically conductive layer comprising an ionically conductive polymer, at least a lithium or sodium salt, and an electronically conductive additive.

[0070] This can be done by the same method as described above for providing an ionically conductive and electronically insulating layer (step a) of the method of the present invention, except that the electronically conductive additive is added to the solution containing the ionically conductive polymer and at least the lithium or sodium salt.

[0071] In another particular embodiment, step b) of the method of the present invention consists of providing an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive. In this particular embodiment, the electronically conductive additive may be added to a solution containing the inorganic material. Alternatively, the components are mixed, for example, by planetary mill grinding, mortar, or any other mixer.

[0072] The present invention is also directed to a half-cell, cell or battery (SSB) comprising the inventive multilayer solid electrolyte of any of the embodiments described herein.

[0073] The half-cell or cell further comprises a cathode side and / or an anode side.

[0074] A battery may include a plurality of the above-mentioned cells, in particular each adjacent pair of the above-mentioned cells being separated by a separator (which may be a bipolar plate).

[0075] In one embodiment, the SSB of the present invention is a lithium battery. Lithium batteries include both lithium ion batteries and lithium metal batteries. In a preferred embodiment, the SSB is a lithium ion battery.

[0076] In certain embodiments, the SSB of the present invention is a lithium-ion battery or a lithium metal battery. As those skilled in the art will be guided by common general knowledge, the above-described embodiments do not encompass lithium-sulfur batteries.

[0077] In another embodiment, the SSB of the present invention is a sodium battery. Sodium batteries include both sodium ion batteries and sodium metal batteries. In a preferred embodiment, the SSB is a sodium ion battery.

[0078] In certain embodiments, the SSB of the present invention is a sodium-ion battery or a sodium metal battery. As those skilled in the art will be guided by common general knowledge, the above-described embodiments do not encompass sodium-sulfur batteries.

[0079] Indeed, a further aspect of the invention is a cell or battery comprising: a) a multilayer solid electrolyte as defined above, b) a negative electrode; c) a positive electrode, It refers to a cell or battery in which a layer of solid electrolyte a) is in contact with the positive electrode and a layer of solid electrolyte b) is in contact with the negative electrode.

[0080] More preferably, the battery is a lithium battery, more preferably a secondary lithium battery.

[0081] A secondary lithium battery is a rechargeable lithium battery. The electrolyte and negative electrode combination of such a battery must be capable of both plating / alloying (or intercalating) lithium onto the electrode (i.e., charging) and stripping / de-alloying (or de-intercalating) lithium from the electrode (i.e., discharging).

[0082] It should be pointed out that the terms anode and cathode as commonly used in battery literature can be confusing and misleading, especially when connected with rechargeable / secondary batteries, and it is for this reason that the battery compositions of the present invention include the terms negative electrode and positive electrode to provide a more accurate designation.

[0083] The negative electrode corresponds to what is usually called the anode, and the positive electrode corresponds to what is usually called the cathode. To be precise, the negative electrode is the anode (the electrode where the oxidation reaction takes place) only during the discharge process. During recharge, the negative electrode functions as the cathode (the electrode where the reduction reaction takes place). Correspondingly, the positive electrode functions as the cathode only during discharge. During recharge, the positive electrode functions as the anode. Thus, as used throughout this specification, the terms negative electrode and positive electrode are used and should be read in accordance with the nomenclature of this paragraph.

[0084] Additionally, the batteries of the invention may include metal foil current collectors for conducting electrical current to and from the positive and negative electrodes.

[0085] The negative electrode of the lithium battery of the present invention typically comprises a substrate and a negative electrode material.

[0086] The substrate may also serve as a current collector in the battery.The substrate may therefore be a metallic substrate made of any suitable metal or alloy, for example formed from one or more of the following metals: Pt, Au, Ti, Al, W, Cu or Ni.

[0087] The negative electrode material may be metallic lithium, a lithium alloying material, or a lithium intercalation material. Lithium may be electrochemically reduced on / in any of these materials in the device.

[0088] Particularly preferred are Li metal electrodes and electrodes containing Li alloyed with Al, Bi, Cd, Mg, Sn, or Sb, In, for example Li-Al. More preferably, the negative electrode is a Li metal electrode.

[0089] The positive electrode may be formed from any typical lithium intercalation material, such as transition metal oxides and their lithium compounds.

[0090] Suitable active material for the positive electrode Examples of the lithium metal oxides are: - Formula Li y Ni 1-x M x Lithium nickel-rich layered oxides of formula (I) and (II) of formula (I) and (II) of formula (II) and (II) of formula (II) -Formula LiNi 2-x M x O4, where M represents at least one transition metal, and 0≦x≦2; - Formula Li 1+x M 1-x Lithium-rich layered oxides of O2 (wherein M represents at least one transition metal and 0≦x≦1); a lithium polyanion of the formula Li2MSiO4 (wherein M is Mn, Co or Ni), LiMPO4 (wherein M is Co or Ni), Li2MP2O7 (wherein M is Mn, Co or Ni), or of the formula Li3V2(PO4)3, Li2VOP2O7 or LiVP2O7, or - Formula Li y A phosphate or sulfate salt of MXO4Z (where y is 0, 1, or 2, M is a transition metal, X is P or S, and Z is F, O, or OH).

[0091] In a preferred embodiment, the cathode active material has the formula Li y Ni 1-x M xThe lithium nickel-rich layered oxide of LiNiO2 (where M represents at least one metal, 0≦x≦1, 0.8≦y≦1.2) is preferably LiNiO2, where M represents at least one metal, 0≦x≦1, 0.8≦y≦1.2. Preferably, M represents at least one of Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, and Sr, more preferably at least one of Co, Mn, and Al, and most preferably Co and Mn. Preferably, x is in the range of 0.01 to 0.5. An example of a suitable active material that can be finally surface treated and / or slightly overlithiated is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2LiNi 0.4 Co 0.2 Mn 0.4 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.05 Mn 0.1 O2, LiNi 0.84 Co 0.06 Mn 0.09 Al 0.01 O2, LiNi 0.85 Mg 0.15 It's O2.

[0092] In certain embodiments, the cathode active material has the formula LiNi 2-x M x O4 (wherein M represents at least one transition metal, 0≦x≦2). Preferably, M represents at least one of Mn and Ti, and examples of suitable active materials include LiNi 0.5 Mn 1.5 O4, LiNi 0.5 Mn 1.2 Ti 0.3 O4, preferably LiNi 0.5 Mn 1.5 He is O4.

[0093] In certain embodiments, the cathode active material has the formula Li 1+x M 1-x Preferably, the lithium-rich layered oxide is represented by the formula xLi2MnO3(1-x)LiMO2, where M represents at least one transition metal and 0≦x≦1. M preferably represents at least one of Mn, Ni and Co. Preferably, the lithium-rich layered oxide is represented by the formula xLi2MnO3(1-x)LiMO2, where M represents at least one metal and 0≦x≦1. Examples of suitable active materials include Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Li 1.2 Mn 0.6 Ni 0.2 O2 (these are 0.5Li2MnO3 0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and 0.5Li2MnO3 0.5LiNi 0.5 Mn 0.5 O2);Li 1.2 Co 0.4 Mn 0.4 O2, Li 1.3 Nb 0.3 Mn 0.4 It's O2.

[0094] In certain embodiments, the cathode active material is a lithium polyanion of formula Li2MSiO4 (where M is Mn, Co, or Ni), LiMPO4 (where M is Fe, Mn, Co, or Ni), Li2MP2O7 (where M is Mn, Co, or Ni), or Li3V2(PO4)3, Li2VOP2O7, or LiVP2O7.

[0095] In certain embodiments, the cathode active material has the formula Li yIt is a phosphate or sulfate of MXO4Z (where y is 0, 1, 2, M is a transition metal, X is P or S, and Z is F, O or OH). M preferably represents one of Co, Ni, Mn, V and Fe. Preferably, the material has a tavorite structure. More preferably, the positive electrode comprises or is made from LiFePO4.

[0096] As is known in the art, the transition metal oxide composite material may be mixed with a binder, such as a polymeric binder, and any electronically conductive additives, before being applied to or formed into a current collector of appropriate shape.

[0097] In certain embodiments, the positive electrode comprises an active material selected from lithium metal oxides and lithium-based olivines.

[0098] In a preferred embodiment, the cell or battery contains lithium metal as the negative electrode and LiFePO4 as the positive electrode.

[0099] In another embodiment, the battery is a sodium battery, more preferably a secondary sodium battery.

[0100] In this embodiment, the anode and cathode are homologs of the anode and cathode defined above for lithium batteries, with Li replacing Na.

[0101] The cathodes described herein are commercially available and well known in the art, for example from Li et al., Chem Soc Rev, 2017, 46, 3006-3059, or Lyu et al., Sustainable Materials and Technologies, 2019, 21, e00098.

[0102] When the electrodes and multi-layer solid electrolyte are assembled to form an electrochemical cell or half-cell, layer 1 of the electrolyte is disposed on the surface of the negative electrode, while layer 2 of the electrolyte is disposed on the surface of the positive electrode.

[0103] More specifically, for assembly of a full cell containing a multi-layer solid electrolyte, the layers are stacked by placing the components on top of each other: layer 1 of the electrolyte is placed on top of the positive electrode, then layer 2 is placed on top of layer 1, and finally the negative electrode is placed on top of layer 2.

[0104] The present invention is also directed to the use of the multilayer solid electrolyte, half-cells, cells or batteries for energy storage in electronic articles such as computers, smart phones, or portable electronic devices (e.g., wearables), in vehicles such as motor vehicles, airplanes, ships, submarines, or bicycles, or in power systems such as those associated with solar panels or wind turbines.

[0105] Item (further embodiment) 1. A multi-layer solid electrolyte for Li-ion and Na-ion batteries, comprising: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive.

[0106] 2. The solid electrolyte according to item 1, wherein the ionically conductive and electronically insulating layer comprises an ionically conductive polymer and at least a lithium salt.

[0107] 3. The solid electrolyte according to item 1, wherein the ionically and electronically conductive layer comprises an ionically conductive polymer, at least a lithium salt, and an electronically conductive additive.

[0108] 4. The solid electrolyte according to item 2 or 3, wherein the ion-conducting polymer is selected from polyethylene oxide, polypropylene oxide, polyethylene oxide / polypropylene oxide grafted poly(alkene-alternating-maleic anhydride) polymers, polyethylene oxide-polypropylene oxide blends, polyethylene oxide-polypropylene oxide block copolymers, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers and polystyrene-polyethylene oxide block polymers.

[0109] 5. The solid electrolyte according to item 4, wherein the ion-conducting polymer is polyethylene oxide.

[0110] 6. The solid electrolyte according to any one of items 2 to 5, wherein at least the lithium salt is selected from lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(trifluoromethanesulfonyl)imide Li[(CF3SO2)2N], lithium bis(perfluoroethylsulfonyl)imide Li[(CF3CF2SO2)2N], lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide Li[(CF3SO2)(FSO2)N], Li[(C2F5SO2)2N], lithium bis(fluorosulfonyl)imide Li[(FSO2)2N], Li[(FSO2)(C4F9SO2)N] and lithium (perfluoroethylsulfonyl)(fluorosulfonyl)imide Li[(FSO2)(CF3CF2SO2)N].

[0111] 7. The solid electrolyte according to any one of items 1 to 6, wherein the electronically conductive additive is selected from carbon, graphite, graphite powder, graphite powder flakes, graphite powder spheroids, carbon black, activated carbon, conductive carbon, amorphous carbon, glassy carbon, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphene, and any combination thereof.

[0112] 8. The ionically conductive and electronically insulating layer (a) a) polyethylene oxide as an ion-conducting polymer; b) a lithium salt selected from Li[(CF3SO2)2N] and Li[(CF3SO2)(FSO2)N].

[0113] 9. The ionically and electronically conductive layer is a) polyethylene oxide as an ion-conducting polymer; b) a lithium salt selected from Li[(CF3SO2)2N] and Li[(CF3SO2)(FSO2)N]; c) an electronic conductive additive selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphite, and carbon black.

[0114] 10. A method for preparing a multilayer solid electrolyte as defined in any one of items 1 to 9, the method comprising: a) an ionically conductive and electronically insulating layer, an ionically conductive polymer and at least a lithium salt or a sodium salt, or providing an ionically conductive and electronically insulating layer comprising an inorganic solid material; b) an ionically and electronically conductive layer, an ionically conductive polymer, at least a lithium salt or a sodium salt, and an electronically conductive additive, or providing an ionically and electronically conductive layer comprising an inorganic solid material and an electronically conductive additive; and c) disposing the ionically and electronically conductive layer provided in step b) on top of the ionically conductive and electronically insulating layer provided in step a).

[0115] 11. An electrochemical Li cell or Li battery comprising a multilayer solid electrolyte as defined in any of items 1 to 9.

[0116] 12. An electrochemical Li cell or Li battery according to item 11, a) a multilayer solid electrolyte as defined in any one of items 1 to 9; b) a negative electrode; c) a positive electrode, Electrochemical Li cell or Li battery, in which a layer a) of a multilayer solid electrolyte is in contact with a positive electrode and a layer b) of a multilayer solid electrolyte is in contact with a negative electrode.

[0117] 13. Multilayer solid electrolyte a) an ionically conductive and electronically insulating layer comprising an ionically conductive polymer and at least a lithium salt; b) an ionically and electronically conductive layer comprising an ionically conductive polymer, at least a lithium salt, and an electronically conductive additive.

[0118] 14. An electrochemical cell or battery according to any of items 12 or 13, wherein the negative electrode comprises a material selected from metallic lithium, a lithium alloying material and a lithium intercalation material.

[0119] 15. An electrochemical cell or battery according to any of items 12 to 14, wherein the positive electrode comprises an active material selected from lithium metal oxide, lithium sulfide and lithium-based olivine.

[0120] The invention will now be described in further detail with reference to the following non-limiting examples. EXAMPLES

[0121] Example 1: Preparation of solid electrolyte The ionically conductive and electronically insulating layer (Layer 1) was prepared from a mixture of lithium bis(trifluoromethanesulfonyl)imide (also known as LiTFSI) and polyethylene oxide (Mw=5 M). The layer formulation was fixed at an ethylene oxide:Li molar ratio of 20:1.

[0122] The ionically and electronically conductive layer (Layer 2) was fabricated from a composite polymer prepared from a mixture of LiTFSI salt with a fixed EO:Li molar ratio of 20:1, polyethylene oxide (Mw=5M), and an electronically conductive additive consisting of multi-walled carbon nanotubes (MWCNTs). The multi-walled carbon nanotubes were added in an amount of 8 wt% with respect to the total weight of Layer 2.

[0123] Example 2: Preparation of a symmetric Li metal cell For the assembly of a symmetric cell containing a multi-layer solid electrolyte, the layers prepared in Example 1 were stacked by placing the components on top of each other. Figure 1a shows a schematic of the assembly of the layers. An ionically and electronically insulating layer (layer 1) is sandwiched between two layers of an ionically and electronically conductive layer (layer 2), and then the whole stack is sandwiched between two plates of lithium metal, resulting in a final configuration of Li metal / layer 2 / layer 1 / layer 2 / Li metal.

[0124] Example 3: Preparation of Li Metal Battery FIG. 1b shows the Li metal solid-state battery cell used in the examples, consisting of a positive electrode layer, a solid electrolyte containing the two layers prepared in Example 1, and a Li metal anode.

[0125] As can be seen, Layer 1 (the ionically conductive and electronically insulating layer) was placed in contact with the cathode, while Layer 2 (the ionically conductive and electronically conductive layer) was placed in contact with the anode).

[0126] The positive electrode layer (or cathode layer) was prepared by mixing the active material (LiFePO4), conductive additive (CNT) and catholyte, which had the same composition of solid electrolyte:PEO-Li salt as layer 1, with an EO:Li molar ratio of 20:1, and the Li salt was LiTFSI.

[0127] The lithium metal anode was prepared by cutting a piece of lithium metal foil having the desired size.

[0128] For the assembly of the whole cell containing the multi-layer solid electrolyte, the different layers prepared above were stacked by placing the components on top of each other. As outlined in FIG. 1b, the electrolyte layer 1 was placed on top of the cathode layer, then an ionically and electronically conductive layer (layer 2) was placed on top of layer 1, and finally, a lithium metal anode was placed on top of layer 2.

[0129] Example 4: Testing of solid electrolytes in a symmetric whole cell configuration The stripping plating capabilities of the electrolyte of the present invention were tested in a symmetrical configuration (FIG. 1a) as described in Example 2, in which solid electrolyte layer 1 was sandwiched between layer 2 and a Li metal plate.

[0130] 0.5mAh cm -2 Symmetric cells were cycled at increasing currents from C / 20 up to 4 C, with an areal capacity of 1000 mA. To ensure high ionic conductivity for the PEO-LiTFSI solid electrolyte layers 1 and 2, the experiments were performed at 70 °C.

[0131] For comparison, symmetric cells having only layer 1 as the solid electrolyte were also prepared and tested. The comparative symmetric cells were charged to 0.2 and 0.5 mAh cm. -2 The areal capacitance was cycled at increasing currents from C / 20 up to a maximum of 4C.

[0132] 0.2mAh cm -2 At the low areal capacity of , the comparative electrolyte withstands up to 1C before shorting at 2C (Figure 2a). -2When the current was increased to 0.1 C, the electrolyte failed after 5 cycles at 0.05 C (FIG. 2b).

[0133] In contrast, the solid electrolyte of the present invention (FIG. 2c) can withstand a full rate capability of 0.05 C up to 4 C and back to 0.1 C without evidence of dendrite formation.

[0134] For the whole-cell experiments, the solid electrolyte was assembled according to the configuration described in Example 3 and shown in Figure 1b. The capacity of the solid electrolyte was 1.0 mAh cm -2 The rate capability of the cells with active material loading was evaluated at 70°C from C / 20 to 2C.

[0135] For comparison, a standard cell configuration using layer 1 as the electrolyte was also tested.

[0136] Therefore, full-cell electrochemical testing was performed in the cell 1 and cell 2 configurations depicted diagrammatically in FIG.

[0137] Cell 1 showed discharge capacity at 0.05 C and 0.1 C. At higher currents, the cell showed no electrochemical activity, likely due to the formation of dendrites.

[0138] Cell 2 and its replicas showed high discharge capacity values ​​from C / 20 up to C / 5. At higher currents, the discharge capacity decreased, but the cell was able to discharge about 50 mAh / g at C / 2 and 1C, and had some electrochemical activity at 2C. The electrochemical results of Cell 2 highlight the improvement when Layer 2 is included at the interface between the Li metal and Layer 1.

[0139] In addition, layer 2 has a lower interfacial resistance with Li metal compared to layer 1. Figure 4 shows the electrochemical impedance spectroscopy profiles of a symmetric Li cell with layer 1 (cell 1) and layer 2 (cell 2).

[0140] Cell 1 shows two hemispheres. The second hemisphere, which appears at a lower frequency, is due to the Li metal / layer 1 interface. The air resistivity (ASR) of this interface is 2100 Ω cm 2 For layer 2 containing the electronic conductive additive, the ASR is 120 Ω cm 2 , showing the improvement at the interface level when layer 2 is included.

Claims

1. 1. An electrochemical Na-ion or Li-ion or Na-metal or Li-metal cell or battery comprising a multi-layer solid electrolyte for Li-ion and Na-ion batteries, the solid electrolyte comprising: c) an ionically conductive and electronically insulating layer, an ion-conducting polymer and at least a lithium or sodium salt, or - an inorganic solid material; d) an ionically and electronically conductive layer, - an ionically conductive polymer, at least a lithium or sodium salt, and an electronically conductive additive, or a layer comprising an inorganic solid material and an electronically conductive additive.

2. 10. The electrochemical cell or battery of claim 1, wherein the ionically conductive and electronically insulating layer comprises an ionically conductive polymer and at least a lithium salt.

3. 3. The electrochemical cell or battery of claim 1 or 2, wherein the ionically and electronically conductive layer comprises an ionically conductive polymer, at least a lithium salt, and an electronically conductive additive.

4. 4. The electrochemical cell or battery of claim 1, wherein the ion-conducting polymer is selected from polyethylene oxide, polypropylene oxide, polyethylene oxide / polypropylene oxide grafted poly(alkene-alt-maleic anhydride) polymers, polyethylene oxide-polypropylene oxide blends, polyethylene oxide-polypropylene oxide block copolymers, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers and polystyrene-polyethylene oxide block polymers.

5. 5. An electrochemical cell or battery according to any one of claims 1 to 4, wherein the ion-conducting polymer is polyethylene oxide.

6. The at least one lithium salt is lithium trifluoromethanesulfonate LiCF ３ SO ３ , lithium bis(trifluoromethanesulfonyl)imide Li[(CF ３ SO ２ ) ２ N], lithium bis(perfluoroethylsulfonyl)imide Li[(CF ３ CF ２ SO ２ ) ２ N], lithium (trifluoromethanesulfonyl) (fluorosulfonyl) imide Li[(CF ３ SO ２ ) (FSO ２ )N], Li[(C ２ F ５ SO ２ ) ２ N], lithium bis(fluorosulfonyl)imide Li[(FSO ２ ) ２ N], Li[(FSO ２ ) (C ４ F ９ SO ２ )N] and lithium (perfluoroethylsulfonyl) (fluorosulfonyl) imide Li[(FSO ２ ) (CF ３ CF ２ SO ２ 6. The electrochemical cell or battery of claim 1, wherein the anion is selected from the group consisting of aryl, aryloxy ...

7. 7. The electrochemical cell or battery of any one of claims 1 to 6, wherein the electronically conductive additive is selected from carbon, graphite, graphite powder, graphite powder flakes, graphite powder spheroids, carbon black, activated carbon, conductive carbon, amorphous carbon, glassy carbon, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphene, and any combination thereof.

8. The ionically conductive and electronically insulating layer (a) a) polyethylene oxide as the ion-conducting polymer; b) Li[(CF ３ SO ２ ) ２ N] and Li[(CF ３ SO ２ ) (FSO ２ 8. The electrochemical cell or battery of claim 1, comprising a lithium salt selected from the group consisting of:

9. the ionically and electronically conductive layer a) polyethylene oxide as the ion-conducting polymer; b) Li[(CF ３ SO ２ ) ２ N] and Li[(CF ３ SO ２ ) (FSO ２ )N]; and and c) an electronically conductive additive selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphite and carbon black.

10. d) a multilayer solid electrolyte as defined in any one of claims 1 to 9; e) a negative electrode; and f) a positive electrode, 10. An electrochemical cell or battery according to any one of claims 1 to 9, wherein said layer a) of the multilayer solid electrolyte is in contact with the positive electrode and said layer b) of the multilayer solid electrolyte is in contact with the negative electrode.

11. 11. An electrochemical cell or battery according to any preceding claim, wherein the negative electrode comprises a material selected from metallic lithium, a lithium alloying material and a lithium intercalation material.

12. 12. An electrochemical cell or battery according to any one of claims 1 to 11, wherein the positive electrode comprises an active material selected from lithium metal oxides and lithium-based olivines.

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