Composite polymer electrolytes for batteries

Abstract

The present invention relates to the field of electrolytes for lithium-ion batteries. In a first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises a lithium salt, a polymer, and γ- LiAlO2 particles, wherein the average particle size of the γ-LiAlO2 particles is at least 2 μm, and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof. In a second aspect, the present invention concerns a solution comprising a solvent, a lithium salt, a polymer, and γ-LiAlO2 particles; wherein the average particle size of the γ-LiAlO2 particles is at least 2 μm, and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof.

Description

[0001] Composite polymer electrolytes for batteries

[0002] Field of the invention

[0003] The present invention relates to the field of electrolytes for lithium-ion batteries. More specifically, the present invention provides an alternative composition for lithium-ion batteries, in which the electrolyte and separator are replaced with a composite polymer electrolyte comprising y-LiAICh particles.

[0004] Background of the invention

[0005] Lithium-ion batteries are used for a wide range of applications and their assembly and components vary somewhat depending on requirements.

[0006] Lithium-ion batteries are continuously developed to increase safety, stability, energy and power density as well as to reduce production cost. Solid-state batteries, in which the liquid electrolyte and separator are replaced with a solid electrolyte, are a promising technology to improve these aspects of battery performance. Some of the main benefits of solid-state batteries is that the approach may i) enable the use of lithium metal anodes, which has significantly higher specific capacity and lower redox potential compared to conventional graphite anodes, ii) avoid the separator and, thus, circumvent failures accompanied with it, as well as iii) replace conventionally used highly flammable electrolytes.

[0007] Solid polymer electrolytes are some of the best-performing electrolytes for solid-state batteries since they are relatively easy to process, exhibit a good mechanical strength and good interfacial contact with electrode materials, as well as exhibit ionic conduction. However, their ionic conductivity especially at room temperature or below remains relatively low and limits their practical applications.

[0008] One approach to increase the ionic conductivity in these solid polymer electrolytes is to include fillers, wherein the fillers are particles of for example AI2O3 or Li7La3Zr20i2, together with the polymer, for example polyethylene oxide or poly(trimethylene carbonate), and a lithium salt, for example lithium bis(trifluoromethylsulfonyl)imide.

[0009] Studies have shown that increasing the particle size of these types of fillers increases the so-called blocking effect, thereby reducing the ionic conductivity of the material.

[0010] Solid polymer electrolytes comprising fillers still have relatively low ionic conductivities which limits their practical applications.

[0011] Thus, there are drawbacks associated with current solid-state battery technology.

[0012] Summary of the invention The objective of the present invention is to overcome the drawbacks of the prior art and improve the performance of lithium-ion batteries.

[0013] In a first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises a lithium salt, a polymer, and y- LiAIOz particles; wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof, and wherein the average particle size of the y-LiAICh particles is at least 2 pm.

[0014] In another aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises a lithium salt, a polymer, and y-Li AIO2 particles; wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof, and wherein the average particle size of the y-LiAICh particles is at least 2 pm; wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

[0015] In another aspect, the present invention concerns a solution comprising a solvent, a lithium salt, a polymer and y-LiAICh particles; wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof, and wherein the average particle size of the y-LiAICh particles is at least 2 pm.

[0016] Brief description of figures

[0017] Figure 1 a) depicts the total ionic conductivity as a function of temperature.

[0018] Figure 1 b) depicts impedance comparison between CPEs fabricated with either y-LiAICh particles (LAO), AI2O3 particles (AO) or Li67sAlo2sLa3Zr2Oi2 particles (LLZO).

[0019] Figure 2 depicts the total ionic conductivity for composite polymer electrolytes at 60°C.

[0020] Figure 3 shows chronoamperograms of a) the solid polymer electrolyte (Filler-free SPE) and b) composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE - 20 wt% LAO).

[0021] Figure 4 shows the Li+transference number of the solid polymer electrolyte and composite polymer electrolyte comprising 20 wt% y-LiAIOz particles.

[0022] Figure 5 a) shows the linear sweep voltammograms of solid polymer electrolyte (Filler-free SPE) and composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE:20 wt% LAO).

[0023] Figure 5 b) shows voltage vs time profile obtained by cut-off increase cell cycling. Figure 6 depicts a) the cycling performances and b) voltage profiles of LiNii / aMni / aCoi / aCh (NMClll) / composite polymer electrolyte / lithium configuration type pouch cells (NMC / CPE20LAO / Li).

[0024] Figure 7 depicts the particle size distribution of the y-Li Al O2 particles.

[0025] Figure 8 depicts stripping and plating experiments at different current densities of a Li / CPE20LAO / Li symmetrical cell at 60 °C.

[0026] Figure 9 depicts a schematic drawing of a lithium-ion battery according to some embodiments of the present invention.

[0027] Figure 10 depicts a schematic drawing of a lithium-ion battery according to some embodiments of the present invention.

[0028] Figure 11 depicts the total ionic conductivity as a function of temperature for composite polymer electrolytes with different size and amounts of y-Li Al O2 particles.

[0029] Figure 12 depicts the total ionic conductivity as a function of temperature.

[0030] Figure 13 depicts SAXS scattering intensity as a function of the scattering vector q for composite polymer electrolytes according to example 1 in a), as well as according to comparative examples 2 in b) and c).

[0031] Figure 14 depicts XRD patterns of y-LiAICh particles a) as well as composite polymer electrolytes according to example 1 with different amounts of y-Li Al O2 particles.

[0032] Figure 15 depicts voltage vs time profile of a composite polymer electrolytes according to example 1 comprising 20 wt% y-LiAICh particles obtained by cut-off increase cell cycling of a cell NMC / / CPE20LAO / / Li configuration pouch cell.

[0033] Figure 16 depicts Coulombic efficiency for a NMC / CPE20LAO / Li configuration pouch cell assembled with the composite polymer electrolyte according to example 1.

[0034] Figure 17 depicts stripping and plating experiments at different current densities of a Li / CPE20LAO / Li symmetrical cell.

[0035] Figure 18 depicts total ionic conductivity as a function of temperature for CPEs according to example 2.

[0036] Figure 19 a) depicts total ionic conductivity as a function of temperature for CPEs according to example

[0037] 3.

[0038] Figure 19 b) depicts total ionic conductivity as a function of temperature for CPEs according to example

[0039] 4. Figure 20 depicts total ionic conductivity as a function of temperature for CPEs according to example 4.

[0040] Itemized embodiments

[0041] In one embodiment according to the first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises a lithium salt, a polymer and y-LiAICh particles; wherein the average particle size of the y-LiAICh particles is at least 2 pm, and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof.

[0042] In one embodiment according to the first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises a lithium salt, a polymer and y-LiAICh particles; wherein the average particle size of the y-LiAICh particles is at least 2 pm, and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof, and wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

[0043] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the average particle size of the y-LiAIC particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0044] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the average particle size of the y-LiAIC particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0045] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, but wherein the amount of y-LiAICh particles in the composite polymer electrolyte is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%.

[0046] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, even more preferably at least 15 wt% but wherein the amount of y-LiAICh particles in the composite polymer electrolyte is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%.ln another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the amount of lithium salt in the composite polymer electrolyte is at least 10 wt%, preferably at least 15 wt%, more preferably at least 20 wt%, but wherein the amount of lithium salt in the composite polymer electrolyte is less than 45 wt%, preferably less than 40 wt%, more preferably less than 35 wt%.

[0047] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the amount of polymer in the composite polymer electrolyte is at least 40 wt%, preferably at least 45 wt%, more preferably at least 50 wt%, but wherein the amount of polymer in the composite polymer electrolyte is less than 75 wt%, preferably less than 70 wt% more preferably less than 65 wt%.

[0048] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate or lithium perchlorate.

[0049] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

[0050] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the polymer is selected from poly(ethylene oxide), poly(trimethylene carbonate), poly(e-caprolactone)-co-poly(trimethylene carbonate), or a combination thereof.

[0051] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the polymer is selected from poly(ethylene oxide), poly(trimethylene carbonate), poly(e-caprolactone)-co-poly(trimethylene carbonate), poly(e-caprolactone) or a combination thereof.

[0052] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery comprising a cathode comprising layered oxides, spinel oxides or polyanionic compounds, preferably wherein the cathode comprises lithium nickel manganese oxides, lithium iron phosphates, lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides, more preferably wherein the cathode comprises lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides. In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery comprising an anode comprising lithium metal.

[0053] In another embodiment according to the first aspect, the present invention concerns a lithium-ion battery wherein the lithium-ion battery is a so-called anode-free lithium metal battery. The anode-free lithium-ion battery is configured to utilize the lithium metal plating on the current collector during charge, and lithium metal stripping from the current collector during discharge, and wherein the anode- free lithium-ion battery is configured without excess lithium metal as anode.

[0054] In one embodiment according to a second aspect, the present invention concerns a solution comprising a solvent, a lithium salt, a polymer, and y-LiAICh particles; wherein the average particle size of the y- LiAIOz particles is at least 2 pm and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof.

[0055] In one embodiment according to the second aspect, the present invention concerns a solution wherein the average particle size of the y-Li Al O2 particles is at least 3 pm, preferably at least 4 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0056] In one embodiment according to the second aspect, the present invention concerns a solution wherein the average particle size of the y-LiAICh particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0057] In one embodiment according to the second aspect, the present invention concerns a solution wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, but wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%.

[0058] In one embodiment according to the second aspect, the present invention concerns a solution wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, even more preferably at least 15 wt%, but wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%. In one embodiment according to the second aspect, the present invention concerns a solution wherein the amount of lithium salt with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 10 wt%, preferably at least 15 wt%, more preferably at least 20 wt%, but wherein the amount of lithium salt with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 45 wt%, preferably less than 40 wt%, more preferably less than 35 wt%.

[0059] In one embodiment according to the second aspect, the present invention concerns a solution wherein the amount of polymer with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least at least 40 wt%, preferably at least 45 wt%, more preferably at least 50 wt%, but wherein the amount of polymer with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 75 wt%, preferably less than 70 wt% more preferably less than 65 wt%.

[0060] In one embodiment according to the second aspect, the present invention concerns a solution wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate or lithium perchlorate.

[0061] In one embodiment according to the second aspect, the present invention concerns a solution wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

[0062] In one embodiment according to the second aspect, the present invention concerns a solution wherein the polymer is selected from poly(ethylene oxide), poly(trimethylene carbonate), poly(e-caprolactone)- co-poly(trimethylene carbonate), or a combination thereof.

[0063] In one embodiment according to the second aspect, the present invention concerns a solution wherein the solvent is selected from acetonitrile, ethylene carbonate, diethyl carbonate, dimethyl sulfoxide, tetrahydrofuran, acetone, methanol, ethanol, dimethylformamide, dimethyl carbonate, ethyl methyl carbonate, N-methylpyrrolidone or a combination thereof.

[0064] In one embodiment according to the second aspect, the present invention concerns a solution wherein the ratio of polymer to solvent is at least 0.01 g / mL, preferably at least 0.03 g / mL, more preferably at least 0.05 g / mL, and / or wherein the ratio of polymer to solvent is less than 1 g / mL, preferably less than 0.8 g / mL, more preferably less than 0.5 g / mL.

[0065] Detailed description of the invention

[0066] According to the first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein said composite polymer electrolyte comprises a lithium salt, a polymer, and y-LiAICh particles; wherein the average particle size of the y-LiAICh particles is at least 2 pm and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof. Furthermore, the lithium-ion battery according to the present invention comprises an anode and a cathode, wherein the composite polymer electrolyte is arranged between them.

[0067] According to the first aspect, the present invention concerns a lithium-ion battery comprising a composite polymer electrolyte, wherein said composite polymer electrolyte comprises a lithium salt, a polymer, and y-LiAICh particles; wherein the average particle size of the y-LiAICh particles is at least 2 pm and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof; and wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate. Furthermore, the lithium-ion battery according to the present invention comprises an anode and a cathode, wherein the composite polymer electrolyte is arranged between them.

[0068] The composite polymer electrolyte according to the present invention can serve as a combination of separator and electrolyte in lithium-ion batteries, i.e. it can serve as solid-state electrolyte. The composite polymer electrolyte prevents or hinders the electrical short circuit between the cathode and the anode by forming a mechanically strong layer that physically separates them. An electrolyte according to the present invention has good ionic conductivity, high lithium-ion transference number and high electrochemical stability. Thus, the present composite polymer electrolyte serves as both a separator and an electrolyte in the lithium-ion battery. The combination of these features enables superior lithium-ion battery performance compared to conventional alternatives.

[0069] The lithium salt provides ions necessary for the ionic conduction within the composite polymer electrolyte.

[0070] The polymer selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof provides a matrix for the lithium salt and y-LiAICh particles. Additionally, the polymer in combination with the lithium salt and y-LiAICh particles is easily processed into a layer, for instance by mixing the polymer, the lithium salt and the y-LiAICh particles in a solvent followed by solution casting and evaporation of solvent (although a skilled person recognizes that there are many possible and analogous approaches to form a composite polymer electrolyte layer comprising the polymer, the lithium salt and the y-LiAICh particles). Additionally, the combination of the polymer, the lithium salt and y-Li Al O2 particles layer gives a good interfacial contact with the electrode materials as well as high electrochemical stability, where interfacial contact influence ionic conductivity between the electrodes. A layer comprising these polymers, the lithium salt and y-LiAICh particles has good mechanical strength. Furthermore, these polymers have relatively high thermal stability which enable the lithium-ion battery to operate at relatively high temperatures. A non-limiting list of relevant polymers is polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof. In one embodiment, the polymer is selected from poly(ethylene oxide) (PEO), poly(trimethylene carbonate) (PTMC), poly(e-caprolactone-co-trimethylene carbonate) (P(CL-co-TMC), or a combination thereof. Preferably, the polymer is poly(ethylene oxide) (PEO). Poly(ethylene oxide) further improves ionic conductivity, lithium-ion transference number and electrochemical stability and provides sufficient mechanical strength.

[0071] The polymer selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof provides a matrix for the lithium salt and y-LiAIOz particles. Additionally, the polymer in combination with the lithium salt and y-LiAICh particles is easily processed into a layer, for instance by mixing the polymer, the lithium salt and the y-LiAICh particles in a solvent followed by solution casting and evaporation of solvent (although a skilled person recognizes that there are many possible and analogous approaches to form a composite polymer electrolyte layer comprising the polymer, the lithium salt and the y-LiAICh particles). Additionally, the combination of the polymer, the lithium salt and y-Li Al O2 particles layer gives a good interfacial contact with the electrode materials as well as high electrochemical stability, where interfacial contact influence ionic conductivity between the electrodes. A layer comprising these polymers, the lithium salt and y-LiAICh particles has good mechanical strength. Furthermore, these polymers have relatively high thermal stability which enable the lithium-ion battery to operate at relatively high temperatures. A non-limiting list of relevant polymers is polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof. In one embodiment, the polymer is selected from poly(ethylene oxide) (PEO), poly(trimethylene carbonate) (PTMC), poly(e-caprolactone-co-trimethylene carbonate) (P(CL-co-TMC), poly(e-caprolactone) (PCL) or a combination thereof. Preferably, the polymer is poly(ethylene oxide) (PEO) or poly(e-caprolactone) (PCL), more preferably wherein the polymer is poly(ethylene oxide) (PEO). Poly(ethylene oxide) further improves ionic conductivity, lithium-ion transference number and electrochemical stability and provides sufficient mechanical strength.

[0072] The y-LiAIO2 particles with an average size of at least 2 pm, is an additive that improves the ionic conductivity as well as the lithium-ion transference number of the composite polymer electrolyte in combination with the polymer and the lithium salt. Additionally, the addition of y-LiAIOz particles with an average size of at least 2 pm results in a further increased electrochemical stability enabling operation at higher potential than conventional alternatives. Furthermore, the y-LiAICh particle phase results in particularly high electrochemical stability of the resulting composite polymer electrolyte.

[0073] Ionic conductivity, the lithium-ion transference number and electrochemical stability are at least partly dependent on particles size of the y-LiAICh particles. In one embodiment of the present invention, the average particle size of the y-Li Al O2 particles is at least 3 pm, preferably at least 4 pm, but wherein the average particle size of the y-Li Al O2 particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0074] Ionic conductivity, the lithium-ion transference number and electrochemical stability are at least partly dependent on particles size of the y-LiAICh particles. In one embodiment of the present invention, the average particle size of the y-Li Al O2 particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

[0075] An average particle size of at least 3 pm, preferably at least 4 pm further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0076] An average particle size of at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0077] An average particle size smaller than 20 pm allows for the formation of thin layers of the polymer composite, enabling a smaller distance between the cathode and the anode thus lower resistance and better performance.

[0078] In one embodiment, the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, but wherein the amount of y-LiAICh particles in the composite polymer electrolyte is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt-%. This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0079] In one embodiment, the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, even more preferably at least 15 wt%, but wherein the amount of y-Li AIO2 particles in the composite polymer electrolyte is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt-%. This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0080] The addition of at least 5 wt% y-LiAICh particles is beneficial for the ionic conductivity, the lithium-ion transference number and electrochemical stability. Preferably the amount of y-LiAICh particles is at least 7 wt%, more preferably at least 10 wt%. Furthermore, an amount of y-LiAICh particles less than 40 wt% is beneficial for the ionic conductivity. Preferably the amount of y-LiAICh particles is less than 30 wt%, more preferably less than 25 wt-%. This further improves the ionic conductivity, the lithium- ion transference number and electrochemical stability.

[0081] In one embodiment, the amount of lithium salt is at least 10 wt% but less than 45 wt%. A lithium salt content above 10 wt% but less than 45 wt% ensures sufficient amount of charge carriers, i.e. ions, in the composite polymer electrolyte to ensure high ionic conductivity but low enough to preserve ionic mobility, i.e. reduces ion-ion and ion-polymer interactions. The amount of lithium salt is preferably at least 15 wt%, more preferably at least 20 wt% but preferably less than 40 wt%, more preferably less than 35 wt%. This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0082] In one embodiment, the amount of polymer in the composite polymer electrolyte is at least 40 wt% but less than 75 wt%. This further improves that the polymer in combination with the lithium salt and y-LiAICh particles is easily processed into a layer, for instance by mixing the polymer, the lithium salt and the y-LiAICh particles in a solvent followed by solution casting and evaporation of solvent (although a skilled person recognizes that there are many possible and analogous approaches to form a composite polymer electrolyte layer comprising the polymer, the lithium salt and the y-LiAICh particles). Additionally, an amount of polymer of at least 40 wt% but less than 75 wt% further improves that the combination of the polymer, the lithium salt and y-LiAICh particles layer gives a good interfacial contact with the electrode materials as well as high electrochemical stability. A layer comprising an amount of polymer of at least 40 wt% but less than 75 wt%, the lithium salt and y-LiAICh particles have good mechanical strength. Furthermore, a layer comprising an amount of polymer of at least 40 wt% but less than 75 wt%, the lithium salt and y-LiAICh particles have relatively high thermal stability which enables the lithium-ion battery to operate at relatively high temperatures. Preferably the amount of polymer is at least 45 wt%, more preferably at least 50 wt%, but wherein the amount of polymer is preferably less than 70 wt%, more preferably less than 65 wt%. This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0083] In one embodiment, the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (IJBF4), lithium hexafluorophosphate (LiPFs), lithium hexafluoroarsenate (LiAsFs), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB) or lithium perchlorate (LiCIC ). Preferably the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB) or lithium difluoro(oxalato)borate (LiDFOB). This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability.

[0084] In one embodiment, the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPFs), lithium hexafluoroarsenate (LiAsFs), lithium bis(oxalato)borate (LiBOB), or lithium difluoro(oxalato)borate (LiDFOB). Preferably the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB) or lithium difluoro(oxalato)borate (LiDFOB). This further improves the ionic conductivity, the lithium-ion transference number and electrochemical stability. More preferably, the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium bis(fluorosulfonyl)imide (LiFSI).

[0085] The lithium salt in combination with the polymer and y-LiAIOz particles with an average particle size of at least 2 pm, ensures high ionic conductivity and high lithium-ion transference number.

[0086] In one embodiment, the lithium-ion battery comprises a cathode comprising layered oxides, spinel oxides or polyanionic compounds. Cathodes comprising layered oxides, spinel oxides or polyanionic compounds enable good performance of lithium ion batteries. Preferably the cathode comprises lithium nickel manganese oxides, lithium iron phosphates, lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides, more preferably wherein the cathode comprises lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides. These cathode materials enable good battery performance.

[0087] In one embodiment, the lithium-ion battery comprises an anode comprising lithium metal. Anodes comprising lithium metal are beneficial for their high capacity and low operating potential. The composite polymer electrolyte according to the present invention exhibit high ionic conductivity in combination with high lithium-ion transference number. In turn, the high lithium-ion mobility is favorable to suppress the formation of lithium dendrites, which is typically accompanied with lithium metal anodes.

[0088] In one embodiment, the lithium ion battery is an anode-free lithium-ion battery. In an anode-free lithium-ion battery, the cell is configured such that lithium is plated on the current collector during charge and stripped from the current collector during discharge at the anode side. A composite polymer electrolyte according to the present invention further improves the performance of anode-free lithium- ion battery cells. A skilled person recognizes that even an anode-free lithium-ion battery comprises an anode comprising at least some lithium metal. An anode-free lithium-ion battery according to the present invention may be assembled without lithium metal as anode. But, as recognized by a skilled person, such anode-free lithium-ion battery is configured such that lithium-ions from the composite polymer electrolyte are plated on the current collector on the anode side during charge.

[0089] According to another aspect, the present invention concerns a solution comprising a solvent, a lithium salt, a polymer and y-LiAICh particles; wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof; and wherein the average particle size of the y-LiAICh particles is at least 2 pm.

[0090] The solvent according to the present invention improves mixing of the lithium salt, the polymer, the y- LiAIOz particles in the solvent.

[0091] In one embodiment, the solution according to the present invention may be used or intended to form a composite polymer electrolyte. This may be accomplished for example by solvent evaporation solution-casting, but a skilled person recognizes that there are many possible and analogous approaches to form a composite polymer electrolyte from the solution according to the present invention. In turn, the composite polymer electrolyte may be used in a lithium-ion battery.

[0092] In one embodiment, the solution comprises a solvent selected from acetonitrile, ethylene carbonate, diethyl carbonate, dimethyl sulfoxide, tetra hydrofuran, acetone, methanol, ethanol, dimethylformamide, dimethyl carbonate, ethyl methyl carbonate, N-methylpyrrolidone or a combination thereof.

[0093] Solutions using these solvents further facilitate formation of composite polymer electrolytes with further improved ionic conductivity, lithium-ion transference number and electrochemical stability.

[0094] In one embodiment, the ratio of polymer to solvent is at least 0.01 g / mL, preferably at least 0.03 g / mL, more preferably at least 0.05 g / mL, and / or wherein the ratio of polymer to solvent is less than 1 g / mL, preferably less than 0.8 g / mL, more preferably less than 0.5 g / mL.

[0095] This further facilitates formation of composite polymer electrolytes with further improved ionic conductivity, lithium-ion transference number and electrochemical stability.

[0096] In one embodiment, the lithium-ion battery according to present invention comprises a composite polymer electrolyte, wherein said composite polymer electrolyte comprises a lithium salt of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a polymer, and y-LiAICh particles with an average particle size of at least 2 pm but smaller than 10 pm. In one embodiment, the lithium-ion battery according to the present invention comprises a composite polymer electrolyte wherein said composite polymer electrolyte comprises a lithium salt, preferably lithium bis(trifluoromethylsulfonyl)imide, a polymer, preferably polyethylene oxide or poly(trimethylene carbonate), and y-LiAICh particles, wherein the average particle size of the y-LiAICh particles is at least 2 pm but less than 10 pm. Preferably the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt% but less than 45 wt%. Preferably the amount of lithium salt in the composite polymer electrolyte is at least 10 wt% but less than 45 wt%. Preferably the amount of polymer is at least 40 wt% but less than 75 wt%.

[0097] In one embodiment, the lithium-ion battery according to the present invention comprises a composite polymer electrolyte wherein said composite polymer electrolyte comprises a lithium salt, preferably lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate or lithium difluoro(oxalato)borate, a polymer, preferably polyethylene oxide or poly(trimethylene carbonate), and y-LiAICh particles, wherein the average particle size of the y-LiAICh particles is at least 3 pm but less than 6 pm. Preferably the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt% but less than 45 wt%. Preferably the amount of lithium salt in the composite polymer electrolyte is at least 10 wt% but less than 45 wt%. Preferably the amount of polymer is at least 40 wt% but less than 75 wt%.

[0098] In another embodiment, the lithium-ion battery according to the present invention comprises a composite polymer electrolyte wherein said composite polymer electrolyte comprises a lithium salt, preferably lithium bis(trifluoromethylsulfonyl)imide or lithium bis(fluorosulfonyl)imide, a polymer, preferably polyethylene oxide, poly(e-caprolactone-co-trimethylene carbonate), poly(e-caprolactone) or poly(trimethylene carbonate), and y-LiAICh particles, wherein the average particle size of the y-LiAIC particles is at least 3 pm but less than 6 pm. Preferably the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt% but less than 45 wt%. Preferably the amount of lithium salt in the composite polymer electrolyte is at least 10 wt% but less than 45 wt%. Preferably the amount of polymer is at least 40 wt% but less than 75 wt%.

[0099] In one embodiment, the solution according to the present invention comprises a solvent, preferably acetone, a lithium salt, preferably lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate or lithium difluoro(oxalato)borate, a polymer, preferably polyethylene oxide or poly(trimethylene carbonate), and y-LiAICh particles, wherein the average particle size of the y-LiAICh particles is at least 2 pm but less than 10 pm. Preferably the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 5 wt% but wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAIC particles is less than 40 wt%. In another embodiment, the solution according to the present invention comprises a solvent, preferably acetone, a lithium salt, preferably lithium bis(trifluoromethylsulfonyl)imide or lithium bis(fluorosulfonyl)imide, a polymer, preferably polyethylene oxide, poly(e-caprolactone-co- trimethylene carbonate), poly(e-caprolactone) or poly(trimethylene carbonate), and y-LiAICh particles, wherein the average particle size of the y-Li Al O2 particles is at least 3 pm but less than 6 pm. Preferably the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 5 wt% but wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 40 wt%.

[0100] Figure 9 is a schematic drawing of a lithium-ion battery 10 according to some embodiments of the present invention. In some embodiments, the lithium-ion battery 10 comprises a composite polymer electrolyte 100, wherein the composite polymer electrolyte comprises a lithium salt, a polymer and y- I AIO2 particles. Wherein the average particle size of the y-Li AIO2 particles is at least 2 pm. Wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof. In some embodiments, the lithium-ion battery comprises an anode 200 and a cathode 300. In some embodiments, the lithium-ion battery 10 comprises a first current collector 400 in electrical contact with the cathode 300. In some embodiments, the lithium-ion battery comprises a second current collector 500 in electrical contact with the anode. In some embodiments, the anode 200 comprises lithium metal.

[0101] Figure 10 is a schematic drawing of an anode-free lithium-ion battery 20 according to some embodiments of the present invention wherein 100 denotes a composite polymer electrolyte, 300 denotes a cathode, 400 denotes a first current collector in electrical contact with the cathode, 500 denotes a second current collector.

[0102] Although the present disclosure has been described with reference to specific embodiments, it will be apparent to those skilled in the art that many variations and modifications may be done within the scope of the present disclosure as described in the specification and defined with reference to the claims below.

[0103] Examples

[0104] Materials: Trimethylene carbonate (TMC; Richman Chemicals), tin(ll) 2-ethylhexanoate (95%; SigmaAldrich) and dry toluene (99.8%; Acros Organics) were stored and handled in an argon-filled glovebox. Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI; BASF) was dried at 120°C under vacuum in a Buchi oven for 48 h prior to use. Anhydrous acetonitrile (99.8%; SigmaAldrich), 1-propanol (>99.5%; SigmaAldrich), and lithium foil (125 pm; Cyprus Foote Minarel Co.) were also used as received. La(OH)3 (99.99%), and ZrCh (99%) purchased from Sigma-Aldrich, and AI2O3 (99.9%; VWR) and U2CO3 (99.99%; SigmaAldrich) were used as received.

[0105] Synthesis of y-LIAIC particles: Stoichiometric amounts of U2CO3 and AI2O3 were mixed and ball-milled in a zirconia jar for 6 hours at a speed of 450 rpm using a planetary ball-mill instrument (Retsch PM100). The obtained powder mixture was heat treated at 900°C for 2 hours with a heating and cooling rate of 5°C / min. The formed y-LiAICh powder (abbreviated as LAO) was thereafter transferred inside an Ar- filled glovebox and used for composite electrolyte fabrication without further processing, as described below.

[0106] Synthesis of polyftrimethylene carbonate): High-molecular-weight poly(trimethylene carbonate) (PTMC) was synthesized through bulk ring-opening polymerization of trimethylene carbonate catalyzed by tin(ll) 2-ethylhexanoate. In a stainless steel reactor 0.2 mol of TMC was added to 0.04 mmol of tin(ll) 2-ethylhexanoate (40 pL of 1 M solution in dry toluene) as catalyst. The reactor was sealed under argon atmosphere, then placed in an oven at 130 °C for 72 h. The reactor was shaken regularly every 30 min for the first 3 h to ensure a good mix of all constituents. Once the polymerization was complete, the reactor was put back inside an argon-filled glovebox and the final product was removed and cut into small pieces. The obtained polymer was a transparent and rubbery solid.

[0107] Comparative example 1 - Solid polymer electrolyte: Self-standing solid polymer electrolyte was obtained via a controlled solvent evaporation solution-casting method. PTMC and 30 wt% LiTFSI were mixed and dissolved in acetonitrile ([Polymer] / [Solvent] = 0.05 g / mL) and kept under magnetic stirring at 40 °C for 12 h inside a glovebox. The resulting solution was poured into Teflon molds before being transferred inside a vacuum oven at a temperature of 30 °C and a pressure of 200 mbar for the first 20 h. Subsequently, the temperature was increased up to 60 °C while the oven was further pumped down to 2 mbar for the next 40 h. After cooling, the obtained solid polymer electrolyte (SPE) films were punched using a 16 mm in diameter punching tool. All process steps were performed inside an argon- filled glovebox and the as-prepared electrolyte films were used as obtained.

[0108] Example 1 - Composite polymer electrolyte (y-LIAIC ) particles: Self-standing composite polymer electrolytes electrolyte samples with a nominal composition of (1-x) wt% [PTMC - 30 wt% LiTFSI] - x wt% y-LiAICh (LAO) (10<x<40) were obtained via a two-step process. Initially, PTMC and 30 wt% LiTFSI were mixed and dissolved in acetonitrile ([Polymer] / [Solvent] = 0.1 g / mL) and kept under magnetic stirring at 60 °C for 12 h inside a glovebox. Subsequently, appropriate amounts of the polymer+salt solution and y-LiAIO2 particles were mixed. The homogeneous polymer-salt-ceramic slurry was solution-cast in Teflon molds, before being transferred inside a vacuum oven at a temperature of 30 °C and a pressure of 200 mbar for the first 20 h. Subsequently, the temperature was increased up to 60 °C while the oven was further pumped down to 2 mbar for the next 40 h. After cooling, the obtained solid composite polymer electrolyte (CPE) films were punched using a 16 mm in diameter punching tool. Their thicknesses were measured with a Mitituyo digital indicator micrometer with typical values ranging from 50 pm to 250 pm depending on the ceramic concentration in the composite electrolyte samples. All process steps were performed inside an argon-filled glovebox and the as-prepared electrolyte films were used as obtained.

[0109] For comparative purposes, two different composite polymer electrolytes were prepared, one with y- LiAIOz particles with median particle size =5 pm and another with y-LiAICh particles with median particle size =20 pm.

[0110] Comparative examples 2 - Composite polymer electrolytes with AI2O3 or Lig. / sAlo^sLasZ^O particles: Lis.75Alo.25La3Zr20i2 (LLZO) particles, the cubic phase of the garnet-type ceramic, were synthesized. Stoichiometric amounts of raw materials (IJ2CO3, La(OH)3, ZrCh and AI2O3) were mixed, to which 1- propanol was added and placed inside a zirconia jar for wet ball-milling using zirconia balls at a speed of 450 rpm for 12 h in a planetary ball-mill instrument (Retsch PM100). 10% excess of IJ2CO3 was added to the previous mix to compensate for Li loss during sintering at thigh temperatures. The obtained white mixture was placed in an Al-crucible and dried inside a ventilated oven at 80 °C for 4-6 h to remove any solvent residues prior to heat treatment. The sintering was conducted in a muffle furnace (MTI corporation, VBF1200X) from room temperature up to 1000 °C for 12 h in air with a rate of 2 °C / min applied during both heating and cooling. The resulting powder was thereafter ball-milled again following the same above-described procedure and stored immediately inside an argon-filled glovebox before use.

[0111] Self-standing composite polymer electrolyte samples with nominal composition of (1-x) wt% [PTMC - 30 wt% LiTFSI] and x wt% AI2O3 (AO) (10<x<40) was prepared in the same manner as example 1.

[0112] Self-standing composite polymer electrolyte samples with nominal composition of (1-x) wt% [PTMC - 30 wt% LiTFSI] and x wt% Li sAlo^sLasZ^On (LLZO) (10<x<40) was prepared in the same manner as example 1.

[0113] Example 2 - Composite polymer electrolyte with (y-LIAIC ) particles and with polyethylene oxide: Selfstanding composite polymer electrolytes electrolyte samples were prepared in accordance with example 1 but with polyethylene oxide (PEO) as the polymer instead of the poly(trimethylene carbonate) (PTMC) used in example 1.

[0114] Example 3 - Composite polymer electrolyte with (y-LIAIC ) particles and with poly(e-caprolactone-co- trimethylene carbonate): Self-standing composite polymer electrolytes electrolyte samples were prepared in accordance with example 1 but with poly(e-caprolactone-co-trimethylene carbonate) copolymer instead of the poly(trimethylene carbonate) (PTMC) used in example 1. The weight ratio of poly(trimethylene carbonate) (PTMC) with respect to poly(e-caprolactone) (PCL) was 80:20 (PTMC:PCL).

[0115] Example 4 - Composite polymer electrolyte with (y-LIAIC ) particles and with poly(e-caprolactone): Selfstanding composite polymer electrolytes electrolyte samples were prepared in accordance with example 1 but with poly(e-caprolactone) as the polymer instead of the poly(trimethylene carbonate) (PTMC) used in example 1.

[0116] Example 5 - Composite polymer electrolyte with (y-LIAIC ) particles and with LiFSI: Self-standing composite polymer electrolytes electrolyte samples were prepared in accordance with example 1 but with lithium bis(fluorosulfonyl)imide (LiFSI) as the salt instead of the lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) used in example l.Comparative example 3 - Solid polymer electrolyte with PEO: Self-standing solid polymer electrolyte was obtained via a controlled solvent evaporation solution-casting method according to comparative example 1 but with PEO as polymer instead of PTMC used in comparative example 1.

[0117] Comparative example 4 - Solid polymer electrolyte with PTMC-co-PCL: Self-standing solid polymer electrolyte was obtained via a controlled solvent evaporation solution-casting method according to comparative example 1 but with PTMC-co-PCL as polymer instead of PTMC used in comparative example 1. The weight ratio of poly(trimethylene carbonate) (PTMC) with respect to poly(e- caprolactone) (PCL) was 80:20 (PTMC:PCL).

[0118] Comparative example 5 - Solid polymer electrolyte with PCL: Self-standing solid polymer electrolyte was obtained via a controlled solvent evaporation solution-casting method according to comparative example 1 but with PCL as polymer instead of PTMC used in comparative example 1.

[0119] Comparative example 6 - Solid polymer electrolyte with LiFSI: Self-standing solid polymer electrolyte was obtained via a controlled solvent evaporation solution-casting method according to comparative example 1 but with LiFSI as lithium salt instead of LiTFSI used in comparative example 1.

[0120] Electrochemical cell assembly: The as-synthesized solid-polymer electrolyte (SPE) and composite polymer electrolyte (CPE) were hermetically placed in CR2025 coin cells, sandwiched between two blocking stainless steel electrodes with a Teflon spacer ring and pressed inside an argon filled glovebox before being taken out for measurements.

[0121] Li / electrolyte / Li configuration type pouch cells were fabricated. First, Li-metal disks were cut using 13 mm and 15 mm in diameter punchers. The cells were assembled by placing the SPE or CPE films between two Li-metal disks and sealed afterwards using vacuum sealer. All steps were carried out in an argon atmosphere.

[0122] The cycling stability of the composite electrolyte vs Lithium metal was evaluated through Li stripping and plating experiments. The tests were carried out on Li / CPE / Li pouch cells with increasing the current density (0.1; 0.3; 0.5; 0.7 and 1 mA cm'2) at 55 °C. The symmetrical pouch cells were assembled with Li metal discs of 12 mm in diameter and a CPE of a 16 mm in diameter, sealed inside an argon-filled glovebox and annealed at 55 °C prior to experiments.

[0123] Lithium iron phosphate / composite polymer electrolyte / lithium configuration type pouch cells were assembled. First, Li-metal disks were cut using 15 mm in diameter puncher. Cathode disks (lithium iron phosphate coated aluminum foil) were cut using 13 mm in diameter puncher. The cells were assembled by placing the SPE or CPE films between Li-metal disk and the cathode disk and sealed afterwards using vacuum sealer. All steps were carried out in an argon atmosphere.

[0124] Similarly, lithium iron phosphate / solid polymer electrolyte / lithium configuration type pouch cells were assembled.

[0125] Similarly, LiNii / aMni / aCoi / aCh (NMClll) / composite polymer electrolyte / lithium configuration type pouch cells were assembled.

[0126] Characterization: The total ionic conductivity of the SPE and different CPEs was determined by electrochemical impedance spectroscopy (EIS). The assembled coin cells were initially annealed at 100°C prior to measurements to improve the interfacial contact. Measurements were carried out within a temperature range from 30°C to 90°C, at a frequency range from 7 MHz to 100 mHz with an applied potential of 10 mV. The data was fitted on Zview software. The impedance data was fitted using a Debye circuit. The total ionic conductivity o was calculated using the equation: where I is the thickness, R is the bulk resistance for the SPE, or the sum of bulk and internal resistances for the CPEs, and A is the cross-sectional geometrical area of the electrolyte film.

[0127] Cationic transference number of the fabricated SPE and different CPEs was tested electrochemically employing Bruce-Vincent method based on potentiostatic polarization of a Li / electrolyte / Li symmetrical cell until a steady state current is reached. The measurements were performed on a BioLogic SP240 potentiostat using pouch cell format consisting of sandwiching a 16 mm in diameter solid electrolyte between two lithium chips 13 mm in diameter. The cells were annealed at 60 °C as both annealing and operating temperature for 12 h prior to measurements. Linear sweep voltammetry was performed on CR2025 coin cells, where the CPE / SPE was sandwiched between a stainless steel electrode as the inert working electrode and a lithium disk of 12 mm diameter as the counter / reference electrode. The measurements were performed at 55 °C, and the voltage was swept from 3 to 6 V vs Li+ / Li with a scan rate of 0.1 mV / s.

[0128] Cut-off increase cell cycling (CICC) technique was employed to take the effect of the active material in consideration. The CICC consisted of galvanostatic cycling at a C-rate of C / 20 at 55 °C for 24 h prior to measurements. Cells with lithium iron phosphate (LFP) were cycled between 2.7 and 3.7 to 5 V vs Li+ / Li.

[0129] Galvanostatic charge-discharge cycling was performed on Li-metal batteries with high-voltage cathode materials (NMC111) at a C-rate of C / 20 at 55 °C.

[0130] Results

[0131] For Figure 1-8, LAO refers to the results obtained with y-LiAIOz particles with median particle size =5 pm.

[0132] Figure 1 a) depicts the total ionic conductivity as a function of temperature for SPE and CPEs within the ceramic content range of 10 wt% to 40 wt%.

[0133] As seen in Figure 1 a), the total ionic conductivity of composite polymer electrolytes comprising y-LiAIOz particles (CPE-10 wt% LAO, CPE-20 wt% LAO, CPE-30 wt% LAO, CPE-40 wt% LAO,) is higher compared to solid polymer electrolyte (Filler-free SPE) for all temperature spanning from 30 °C to 90 °C. Highest total ionic conductivity was measured for composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE-20 wt% LAO).

[0134] Figure 1 b) depicts impedance comparison between CPEs fabricated with either LAO, AO or LLZO. As seen in Figure 1 b) the impedance is lower for CPEs comprising LAO, i.e. y-LiAIOj.

[0135] Figure 2 depicts the total ionic conductivity for composite polymer electrolytes comprising y-LiAIOz particles (CPE-LAO), AI2O3 (AO), and Lis.ysAlo.zsLasZrzOu (LLZO) for a range of different ceramic filler content at 60°C. As seen in Figure 2, the total ionic conductivity of composite polymer electrolytes comprising y-LiAIOz particles (CPE-LAO) is equal or higher than for composite polymer electrolytes comprising AI2O3 (AO) or Li sAlo^sLasZ^On (LLZO).

[0136] Figure 3 shows chronoamperograms of a) the solid polymer electrolyte (Filler-free SPE) and composite polymer electrolyte comprising 20 wt% y-LiAIO2 particles (CPE - 20 wt% LAO). The insets represent the Nyquist plot before and after polarization. Rb and R t stand for the bulk and interfacial resistances, respectively. Figure 4 shows the Li+transference number of the solid polymer electrolyte and composite polymer electrolyte comprising 20 wt% y-Li Al O2 particles (CPE - 20 wt% LAO). As seen in Figure 4, the composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE - 20 wt% LAO) exhibited a Li+transference number of 0.974.

[0137] Figure 5 a) shows the linear sweep voltammograms of solid polymer electrolyte (Filler-free SPE) and composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE - 20 wt% LAO). As seen in Figure 5 a) the composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE - 20 wt% LAO) exhibited lower oxidation currents, indicative of better electrochemical stability than for the solid polymer electrolyte (Filler-free SPE).

[0138] Figure 5 b) shows voltage vs time profile obtained by cut-off increase cell cycling.

[0139] As seen in Figure 5 a) and b), the electrochemical stability window becomes wider for battery cells comprising the composite polymer electrolyte comprising 20 wt% y-LiAIOz particles (CPE - 20 wt% LAO), and the oxidation stability of the composite polymer electrolyte comprising 20 wt% y-LiAIOz particles is maintained up to 5 V. This would allow the use of composite polymer electrolyte comprising 20 wt% y-LiAIO2 particles in solid state high voltage Li-metal batteries.

[0140] Figure 6 depicts the cycling performances a) and voltage profiles b) of LiNii / aMni / aCoi / aOz (NMClll) / composite polymer electrolyte / lithium configuration type pouch cells (NMC / CPE20LAO / Li). As seen in Figure 6, battery cells NMC / CPE20LAO / Li exhibited high specific capacity and high coulombic efficiency.

[0141] Figure 7 depicts the particle size distribution of the y-LiAICh particles. As seen in Figure 7, the average particle size of the y-LiAICh particles was 4.5 pm.

[0142] Figure 8 depicts Li stripping and plating experiments at different current densities of Li / CPE20LAO / Li, i.e. symmetrical cells with CPE comprising 20 wt% y-LiAICh. As seen in Figure 8 the Li / CPE20LAO / Li comprising the composite polymer electrolyte according to the present invention exhibits a well- behaved plating / stripping of lithium.

[0143] Figure 11 depicts a comparison between the total ionic conductivity as a function of temperature of composite polymer electrolytes prepared with either y-LiAICh particles with median particle size =20 pm (CPE-X wt% LAO "20 pm") or with y-LiAIOz particles with median particle size =5 pm (CPE-X wt% LAO "5 pm") with different amounts of y-LiAIOz particles.

[0144] Figure 12 depicts the total ionic conductivity as a function of temperature for SPE and CPEs within the ceramic content range of 10 wt% to 40 wt% of y-LiAIOz particles with median particle size =20 pm. Figure 13a)-16 and 18-20 refers to the results obtained with y-LiAICh particles with median particle size =5 pm.

[0145] Figure 13 depicts the SAXS scattered intensity as a function of the scattering vector q with a range of different particle concentrations. Measurements were performed on CPE with a) y-LiAICh particles according to example 1, as well as for b) AO particles and c) LLZO particles prepared according to comparative example 2.

[0146] Figure 14 a) depicts XRD for as synthesized y-LiAIO2 particles.

[0147] Figure 14 b) depicts XRD for CPE according to example 1 for a range of different y-LiAIO2 particle concentrations, wherein CPE40 denotes 40 wt% LAO, CPE30 denotes 30 wt% LAO, CPE20 denotes 20 wt% LAO, CPE10 denotes 10 wt% LAO, and LiAICh denotes the as synthesized y-LiAIO2 particles.

[0148] Figure 15 depicts voltage vs time profile obtained by cut-off increase cell cycling cycled at a 0.05 C rate at 55 °C of a NMC / CPE20LAO / Li configuration pouch cell assembled with the composite polymer electrolyte according to example 1 comprising 20 wt% y-LiAIO2 particles.

[0149] Figure 16 depicts the Coulombic efficiency cycled at a 0.05 C rate between 2.7 V and 4.2 V at 55 °C of a NMC / CPE20LAO / Li configuration pouch cell assembled with the composite polymer electrolyte according to example 1 comprising 20 wt% y-LiAICh particles.

[0150] Figure 17 depicts Li stripping and plating experiments at 0.1 mA / cm'2at 55 °C of Li / SPE / Li, i.e. symmetrical cells with SPE according to comparative example 1.

[0151] Figure 18 depicts total ionic conductivity as a function of temperature for CPEs according to example 2, i.e. with PEO as polymer, for a range of 10 wt% to 60 wt% of y-Li Al O2 particles.

[0152] Figure 19 a) depicts total ionic conductivity as a function of temperature for CPEs according to example

[0153] 3 for a range of 10 wt% to 40 wt% of y-LiAICh particles.

[0154] Figure 19 b) depicts total ionic conductivity as a function of temperature for CPEs according to example

[0155] 4 for a range of 10 wt% to 40 wt% of y-Li Al O2 particles.

[0156] Figure 20 depicts total ionic conductivity as a function of temperature for CPEs according to example 5 for a range of 10 wt% to 40 wt% of y-Li Al O2 particles.

[0157] A summary of the examples and comparative examples as well as the figure in which their data is presented is found in Table 1 below.

[0158] Table 1. Summary of examples and comparative examples as well as the figure in which their data is presented.

Claims

CLAIMS1. A lithium-ion battery comprising a composite polymer electrolyte, wherein the composite polymer electrolyte comprises: a lithium salt; a polymer; y-LiAICh particles; and wherein the average particle size of the y-Li Al O2 particles is at least 2 pm; and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof; and wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

2. A lithium-ion battery according to claim 1, wherein the average particle size of the y-LiAICh particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

3. A lithium-ion battery according to claim 1 or 2, wherein the amount of y-LiAICh particles in the composite polymer electrolyte is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, even more preferably at least 15 wt% but wherein the amount of y-Li AIO2 particles in the composite polymer electrolyte is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%.

4. A lithium-ion battery according to any of claims 1-3, wherein the amount of lithium salt in the composite polymer electrolyte is at least 10 wt%, preferably at least 15 wt%, more preferably at least 20 wt%, but wherein the amount of lithium salt in the composite polymer electrolyte is less than 45 wt%, preferably less than 40 wt%, more preferably less than 35 wt%.

5. A lithium-ion battery according to any of claims 1-4, wherein the amount of polymer in the composite polymer electrolyte is at least 40 wt%, preferably at least 45 wt%, more preferably at least 50 wt%, but wherein the amount of polymer in the composite polymer electrolyte is less than 75 wt%, preferably less than 70 wt% more preferably less than 65 wt%.

6. A lithium-ion battery according to any of claims 1-5, wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate preferably the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

7. A lithium-ion battery according to any of claims 1-6, wherein the polymer is selected from poly(ethylene oxide), poly(trimethylene carbonate), poly(e-caprolactone-co-trimethylene carbonate), poly(e-caprolactone) or a combination thereof.

8. A lithium-ion battery according to any of claims 1-7, comprising a cathode comprising layered oxides, spinel oxides or polyanionic compounds, preferably wherein the cathode comprises lithium nickel manganese oxides, lithium iron phosphates, lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides, more preferably wherein the cathode comprises lithium nickel manganese cobalt oxides or lithium nickel cobalt aluminum oxides.

9. A lithium-ion battery according to any one of claims 1-8, comprising an anode comprising lithium metal.

10. A lithium-ion battery according to any one of claims 1-9, wherein the lithium-ion battery is an anode-free lithium-ion battery.

11. A solution comprising: a solvent; a lithium salt; a polymer; y-LiAICh particles; and wherein the average particle size of the y-LiAICh particles is at least 2 pm; and wherein the polymer is selected from a polyether, polycarbonate, polyketone, polyester, polynitrile, copolymers thereof and / or a combination thereof.

12. A solution according to claim 11, wherein the average particle size of the y-LiAICh particles is at least 3 pm, preferably at least 4 pm, more preferably at least 4.5 pm, but wherein the average particle size of the y-LiAICh particles is preferably smaller than 20 pm, more preferably smaller than 15 pm, more preferably smaller than 12 pm, more preferably smaller than 10 pm, more preferably smaller than 8 pm.

13. A solution according to claim 11 or 12, wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 5 wt%, preferably at least 7 wt%, more preferably at least 10 wt%, even more preferably at least 15 wt%, but wherein the amount of y-LiAICh particles with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 40 wt%, preferably less than 30 wt%, more preferably less than 25 wt%.

14. A solution according to any of claims 11-13, wherein the amount of lithium salt with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least 10 wt%, preferably at least 15 wt%, more preferably at least 20 wt%, but wherein the amount of lithium salt with respect to the sum of lithium salt, polymer and y-LiAICh particles is less than 45 wt%, preferably less than 40 wt%, more preferably less than 35 wt%.

15. A solution according to any of claims 11-14, wherein the amount of polymer with respect to the sum of lithium salt, polymer and y-LiAICh particles is at least at least 40 wt%, preferably at least 45 wt%, more preferably at least 50 wt%, but wherein the amount of polymer with respect to the sum of lithium salt, polymer and y-LiAIC particles is less than 75 wt%, preferably less than 70 wt% more preferably less than 65 wt%.

16. A solution according to any of claims 11-15, wherein the lithium salt is selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithiumhexafluorophosphate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

17. A solution according to any of claims 11-16, wherein the polymer is selected from poly(ethylene oxide), poly(trimethylene carbonate), poly(e-caprolactone-co-trimethylene carbonate), or a combination thereof.

18. A solution according to any of claims 11-17, wherein the solvent is selected from acetonitrile, ethylene carbonate, diethyl carbonate, dimethyl sulfoxide, tetra hydrofuran, acetone, methanol, ethanol, dimethylformamide, dimethyl carbonate, ethyl methyl carbonate, N- methylpyrrolidone or a combination thereof.

19. A solution according to any one of claims 11-18, wherein the ratio of polymer to solvent is at least 0.01 g / mL, preferably at least 0.03 g / mL, more preferably at least 0.05 g / mL, and / or wherein the ratio of polymer to solvent is less than 1 g / mL, preferably less than 0.8 g / mL, more preferably less than 0.5 g / mL.

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