Secondary cell with a molded hybrid electrode

Abstract

A molded anode comprising an active material or a composition of active materials, wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode; a secondary cell comprising said anode; a method for its manufacturing; and a vehicle comprising such secondary cell.

Description

[0001] SECONDARY CELL WITH A MOLDED HYBRID ELECTRODE

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to a secondary cell containing a molded anode that comprises a metal ion storage layer. More particularly, the present disclosure relates to a secondary cell containing a molded anode comprising a substrate and a metal ion storage layer, wherein the metal ion storage layer is deposited on the substrate, a method for manufacturing the secondary cell, as well as a vehicle comprising such secondary cell.

[0004] TECHNICAL BACKGROUND

[0005] Rechargeable batteries having high energy density and discharge voltage, in particular Li-ion batteries, are a vital component in portable electronic devices and are a key enabler for the electrification of transport and large-scale storage of electricity. To reach higher energy densities, new types of batteries are being developed.

[0006] State of the art Li-ion batteries typically consists of stacks of secondary cells, wherein each cell is composed of a cathode comprising a cathode current collector, an electrolyte, an anode comprising an anode current collector, and optionally a separator positioned between the anode and cathode.

[0007] In secondary cells where the anodes are made of graphite-based materials and a metal current collector, the cations are extracted from the cathode material and then diffuse from the cathode material through the electrolyte and intercalate into the anode material during charging. During discharge, this process is reversed.

[0008] In an effort to increase the energy density, the development has gone towards lithium metal batteries since lithium metal demonstrates a much higher specific capacity and a lower redox potential than graphite. In such batteries, the anode consists of a lithium metal whose corresponding cations carry the current in the electrolyte. However, the use of lithium metal poses several challenges during both manufacturing and cycling of the battery. Lithium metal reacts violently with water and extra precautions are therefore required during assembly of lithium metal battery cells, such as strict dry room conditions, strict waste management and modification of the equipment, to prevent spontaneous ignition. During cycling, lithium metal deposition and dissolution is associated with large volume changes which can reduce the cycling stability of the cell.

[0009] Another issue with secondary cells containing lithium metal is the formation of lithium metal dendrites when the corresponding lithium ion is deposited on the anode. That risk increases upon repetition of charging and discharging cycles or during particularly fast charging conditions. This hamper cycling stability, as some of these dendrites can break off and get electronically disconnected, hence reducing access to otherwise useful charge in the battery. Dendrites also increase the risk for short-circuits in the secondary cell, as dendrites can grow through the electrolyte and the separator, thereby putting the anode in contact with the cathode, resulting in serious fire hazards.

[0010] Increasing the uniformity of metal plating is thus important to reduce the risk of dendrite formation as well as to alleviate problems related to large volume changes. One way to achieve this is to confine lithium plating within a certain structure, such as pores. The high surface area of a porous structure reduces the local current density and the risk of dendrites while the available pore volume allows for lithium deposition without further overall volume change in the cell. However, the porous structure adds weight to the battery reducing the advantages of using a lithium metal anode.

[0011] Hence, there is a need for more weight and volume efficient secondary cells with a reduced risk of dendrite formation.

[0012] SUMMARY OF THE INVENTION

[0013] An object of the present invention is to provide a secondary cell with homogenous metal deposition growth, wherein the cell contains a molded anode that comprises a metal ion storage layer deposited on a substrate. A further object is the provision of a secondary cell that can be assembled without the insertion of any lithium metal.

[0014] The present invention thus provides a secondary cell with an improved cell safety level as the cell does not comprise a Li metal foil.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional image of a molded electrode according to the invention, having two opposite faces with layers of active materials comprising cavities, in uncharged state.

[0017] Figure 2 is a cross-sectional image of a molded electrode according to the invention in charged state.

[0018] Figure 3 is a top view photo of a molded anode active material.

[0019] Figure 4 is a cross-sectional photo of a) a molded anode coated on two sides with active material, and b) a non-molded anode.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] All aspects and embodiments disclosed herein can be combined with any other aspect and / or embodiment disclosed herein.

[0022] In a first aspect, the present invention relates to a molded anode comprising an active material or a composition of active materials, wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode. The term "molded" as used herein means actively formed cavities of a desired predetermined shape on the surface of the active material. Formed cavities are not equivalent with existing pores in the active material, as pores have higher tortuosity compared to cavities and does not have pre-determined shapes. The term "thickness of the anode" refers to the total thickness of the anode, including all active materials and a substrate when present, before the first charge cycle. The term "active material or composition of active materials" is interchangeable with the term "metal ion storage layer" throughout the application. If the metal is lithium the "term lithium ion storage layer" may be used interchangeably with "active material or composition of active materials".

[0023] In one embodiment, the anode comprises a substrate and a metal ion storage layer. Preferably, the metal is lithium. Thus in some embodiments, the metal ion storage layer is a lithium ion storage layer.

[0024] Metal plating occurs inside the molded surface cavities of the anode according to the present invention, reducing the amount of top surface plating, and may render the top surface plating more even. This is attributed to the fact that the surface cavities affect the directionality of the plating process. Instead of the metal always plating towards the separator, top surface plating may now occur in other directions. This reduces the risk of dendrite formation and contributes to reduced swelling of the anode during charging. This is illustrated in figure 4, where a) is a photograph of a molded anode according to the invention and b) is a photograph of a non-molded anode. The denoted numbers are: 1. Cupper top layer from cross section setup; 2. Plated lithium; 3. Molded graphite according to the invention; 4. Cupper foil; 5. Non-molded graphite.

[0025] In some embodiments, the surface cavities are fabricated, for example by man or machine, such as by using a focused laser beam, an ion beam, or a mechanical pressure, for example rol l-to-rol I pressure, or ID hydraulic pressure.

[0026] In some embodiments, the surface cavity of the anode is from about 10 pm to about 2000 pm wide, preferably from about 10 pm to about 1500 pm, more preferably from about 10 pm to about 1000 pm, even more preferably from about 20 pm to about 800 pm, most preferably from about 40 pm to about 800 pm. The width of the cavities is referring to the maximal width of the cavity in a certain shape. The cavities may have any shape, such as circular, oval, elongated, polygonal, regular and irregular. The cavities may have a bowl-shaped bottom or a tapering depth, such as in the shape of a cone.

[0027] Optimization of the cavity size and the spacing between the cavities reduces the risks of penetrating the separator. The combined surface constituted by the cavities' top layer may be expressed in terms of cavity width ratio: area (cavity top) / area (whole top surface). In some embodiments, the cavity width ratio is from about 0.1 to about 0.9, preferably 0.2 to about 0.9, more preferably from about 0.2 to about 0.7, most preferably from about 0.2 to about 0.5. The cavity top area is defined as the projected area by the cavity opening.

[0028] The cavities should have a depth that is sufficient for improving plating of the metal. In some embodiments, at least some, or all, cavities go through the anode, i.e., the active material and the current collector. In some embodiments, none of the cavities go through the current collector. In some embodiments, the material between the bottom of the surface cavities and the current collector is at least 2 pm thick, preferably at least 5 pm thick, more preferably at least 10 pm thick. In some embodiments, the depth of the surface cavities is from about 10% to about 90% of the total thickness of the anode. Preferably, the depth of the surface cavities is from about 20% to about 80% of the total thickness of the anode, more preferably from about 30% to about 70%, even more preferably from about 40% to about 60% of the total thickness of the anode. In some embodiments, the depth of the surface cavities is at least 10% of the thickness of the anode.

[0029] In some embodiments, the distance between each individual surface cavity of the molded anode is at least 2 pm, 5 pm, 10 pm, 15 pm, or at least 20 pm. The distance between the individual cavities is measured edge to edge. Should the distance between the cavities be too short, there is a risk that the anode does not mechanically support an added separator for stacking into a working cell. As used herein, the term "about" refers to a value or parameter herein that includes (and describes) embodiments that are directed to that value or parameter per se. For example, description referring to "about 20" includes description of "20." Numeric ranges are inclusive of the numbers defining the range. Generally speaking, the term "about" refers to the indicated value of the variable and to all values of the variable that are within the experimental error of the indicated value (e.g., within the 95% confidence interval for the mean) or within 10 percent of the indicated value, whichever is greater.

[0030] In some embodiments, the anode has one surface comprising cavities. In other embodiments, the anode comprises two opposing faces with layers comprising surface cavities.

[0031] In one embodiment of the present invention the substrate is a current collector. The substrate may be selected from any one of metal foil, metal mesh, or metal non-woven, such as copper foil, copper mesh, or copper non-woven; a polymer coated with a conducting material, preferably a metal; a graphite sheet, carbon nanotubes (CNT), graphene, graphene oxide, carbon nanofibers, and carbon paper.

[0032] In some embodiments the secondary cell is a lithium secondary cell, wherein the metal ion storage layer is a lithium ion storage layer. The lithium ion storage layer will function as extra lithium ion source for prolonged cycles, and / or increased number of cycles. In one embodiment of the present invention, the lithium ion storage layer comprises metallic lithium.

[0033] In some embodiments, the active material or the composition of active materials is selected from any one of non-graphitizing carbon, graphite, silicon, silicon alloy, silicon oxide (SiOx, wherein x is smaller than or equal to 2), silicon-carbon composite, a transition metal dichalcogenide (e.g. titanium disulfide (TiS2)), tin-cobalt alloy, lithium titanate oxide (LTO, Li^isO ), MXenes (e.g. V2CTX, Nb2CTx, Ti2CTx, and Ti3C2Tx, wherein T is a functional group, such as O, F, OH or Cl, and x is the number of functional groups and is typically a number from 1 to 4), or a combination of at least two of these. The term "MXenes", as used herein, represents two-dimensional inorganic compounds making up a-few-atoms-thick layers of transition metal carbides, nitrides, or carbonitrides. MXenes combine the metallic conductivity of transition metal carbides with a hydrophilic character.

[0034] In one embodiment, the molded anode comprises particles of the active material or composition of active materials.

[0035] In some embodiments, the active material comprises active metal-ions already before the first charge cycle. In one embodiment, the active material or composition of active materials comprises particles, which are at least partially pre-charged with metal ions. In one embodiment, the active material is pre-charged with lithium ions. In one embodiment, the lithium-ion storage layer comprises LiisSi4, LiCe, LiisSns, or IJ9AI4. The term "pre-charged", as used herein, means that metal-ions exists in the layer before its first charge cycle.

[0036] The particles making up the metal ion storage layer give the layer a certain porosity. This increases the specific surface area of the anode. The porosity of the anode refers to the porosity of the entire anode, including the molded cavities. Plating of lithium takes place inside the cavities as well as inside the pores, which reduces the overall volume change of the electrode during plating. Furthermore, a large specific surface area provides for a large reaction area for the plating to occur in comparison with an anode without cavities or pores. This reduces the local current density and thereby reduces the risk of dendrite formation even more. Preferably, the particles of the lithium ion storage layer have a specific surface area (SSA) of from 0.1 m2 / g to 1000 m2 / g, preferably from 1 m2 / g to 700 m2 / g.

[0037] In yet another embodiment, the anode has a porosity in the interval of from 10% to 90% of the total volume of the active material, preferably from 15% to 75%, more preferably from 25 to 50%. In a preferred porosity interval of from 10% to 30%, lithiation of lithium ions into the active material or composition of active materials is facilitated. In another preferred porosity interval of from 30% to 70%, or from 30% to 60%, plating of lithium onto the active material or composition of active materials is facilitated. During lithiation, lithium ions are stored within the anode material or composition of active materials without occupying any of the void volume constituting the cavities or pores. Whereas, in accordance with the invention, the lithium plating takes place on the surface of the lithium ion storage layer, i.e. in the cavities and in the pores of the active material or composition of active materials, effectively filling the void volume without causing any substantial volume change of the anode. Figure 1 illustrates an anode of the present invention, in an embodiment where the anode has two opposite faces with surface cavities, in its uncharged state. That is, no plating or lithium has yet occurred. Figure 2 illustrates the same anode in its charged state. The denoted numbers are: 1. Porous graphite layer; 2. Metallic current collector; 3. Molded cavity; 4. Lithium inserted graphite with plated lithium inside the pores; 5. Plated lithium.

[0038] The plating has first filled the pores and the cavities, then formed an even layer of plated lithium on top of the anode. As the lithium ions resulting from lithiation do not occupy the space where plating can occur, an increased areal capacity is reached.

[0039] In one embodiment of the present invention, the anode has a minimum porosity as defined by formula (1), wherein P is the porosity, r is the N / P ratio, Cais the anode specific capacity, or in the case of a composition of active materials the weighted average anode specific capacity, [mAh / g], pais the anode active material density, or in the case of a composition of active materials the weighted average anode active material density, [g / cm3], Cu is the lithium specific capacity [mAh / g] (3862 mAh / g), and pu is the lithium density [g / cm3] (0.53 g / cm3). The term "N / P ratio" is used herein for the capacity ratio between the anode and cathode. Finding the anode specific capacity for the anode material and lithium specific capacity is common knowledge in the field.

[0040] In one embodiment the anode loading amount to the cathode loading amount (N / P ratio) is 0.01 to 0.99, preferably 0.25 to 0.75, more preferably 0.3 to 0.5.

[0041] In one embodiment the lithium ion storage layer of the molded anode has a porosity in the range of P to 1.5*P, where P is defined as the porosity according to formula (1).

[0042] In one embodiment, the lithium ion storage layer of the molded anode has a porosity in the range of P to 1.1*P, where P is defined as the porosity according to formula (1).

[0043] By optimizing the cavity and pore sizes, the lithium deposition on the top surface will be more evenly distributed, improving the cycle life of the secondary cell. The skilled person is well equipped to make such optimizations.

[0044] With a conventional anode substrate that only allows for lithium plating, the areal capacity peaks at the maximum level of plating. With an anode of the present invention, that capacity level is surpassed, as the anode's maximum plating level is complemented by lithiation. The anode according to the invention also reaches a higher Coulombic Efficiency (CE) as compared to a conventional anode on which only plating occurs, using the same amount of plated lithium. The lithiation may represent from 10% to 70%, preferably from 30% to 60% of the total areal capacity of the anode. In one embodiment, the lithiation constitutes up to 50%, such as from 10% to 50%, or from 30% to 50% of the total areal capacity of the anode. The extra capacity derived from lithiation does not impede the reversibility of the charging process, which is especially important during repeated charging cycles. The present invention improves the cycling stability and reduces the risk for early secondary cell failure, both under normal and high current operations. During continuous cycling, uneven plating of the top surface of the anode, may result in unfavorable dendritic growth of lithium metal. To prevent dendritic growth, surface cavities help reduce the interfacial activity of the top surface in accordance with the invention, whereby the occurrence of lithium ion reduction on the top surface is reduced. Lithium-ions are instead allowed to migrate deep into the lithium ion storage layer. As a result, lithium metal starts to deposit bottom-up in the lithium ion storage layer, gradually filling the void spaces.

[0045] The void space is, in accordance with the present invention, large enough to accommodate the total volume of plated lithium. Hence, the cavity size and porosity of the lithium ion storage layers can be optimized through the choice of active material or composition of active materials, as well as the ratio between lithiated lithium ions and plated lithium metal. By adjusting the cavity size and the porosity, the ratio between lithiated lithium ions and plated lithium metal may be optimized such that the plated lithium can be better contained within the cavities and pores of the lithium-ion storage layer.

[0046] In one embodiment of the present invention, a functional layer is at least partially, optionally fully, coated on the particles of the lithium ion storage layer. The functional layer is suitable for lithium metal deposition and may promote a homogenous lithium metal deposition growth. Preferably, the functional layer comprises surface functional group, for example, OH, COOH, CSOH, CONH2, CSNH2, NH, NH2, SH, CN, NO2and triazolium; non-graphitizing carbon; a metal or metalloid, for example Si, Sn, Al, Zn, Ag, In, Mg; a metal or metalloid oxide, for example, AI2Os, LiAIO2, ZnO, MnO2, CO3O4, SnO2, SiOx(x smaller than or equal to 2), V2Os, CuxO (1 < x < 2), TiO2, Li2O, Li2O2, ZrO2, MgO, Ta2Os, Nb2Os, LiAIO2, Li?La3Zr20i2(LLZO), Li4TisOi2(LTO), B2Os, LisBOs-LhCOs; a metal fluoride, for example AIF3, LiF; a metal phosphate, for example AIPO4, Li3PO4, Lii.3AI0.3Tii.7(PO4)3 (LATP); piezoelectric material, such as BaTiOs, or PbZrxTii-xO3 where x is any number between 1 and 10; a metal hydroxide, such as AIO(OH) (boehmite), Mg(OH)2, AI(OH)3; a metal or metalloid nitride, such as AIN, BN, SisN4; AlfNOsh; BaSO4; or a polymer or polymer electrolyte, containing for example polyvinylidene fluoride (PVDF), preferably in its beta phase, PVDF-HFP, PMMA, PEO, polysiloxane for example PDMS, lithium polyacrylate (Li-PAA); and mixtures thereof.

[0047] In a second aspect, the present invention relates to a secondary cell comprising a molded anode, a cathode, an electrolyte, and optionally a separator, characterized in that the anode comprises a substrate and a metal ion storage layer comprising an active material or a composition of active materials, wherein the metal ion storage layer is deposited on the substrate, and wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode.

[0048] In one embodiment of the present invention, the anode does not comprise any lithium metal when the secondary cell is in its uncharged state. Preferably, the secondary cell does not comprise any lithium metal when the secondary cell is in its uncharged state.

[0049] In one embodiment of the present invention, the electrolyte is a liquid electrolyte comprising at least one lithium salt and at least one or more solvents selected from the group consisting of carbonate solvents and their fluorinated equivalents, diCi-4 ethers and their fluorinated equivalents and ionic liquids. The lithium salt is preferably one or more selected from the group consisting of lithium hexafluorophosphate (LiPFe), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium (fluorosulfonyl) (trifluoromethanesulfonyl) imide (LiFTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium

[0050] (pentafluoroethanesulfonyl)(trifluoromethanesulfonyl)imide (LiPTFSI), lithium trifluoromethanesulfonate (LiOTf), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium tetrafluoroborate (IJBF4), lithium nitrate (LiNOs), and lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI). The solvent is preferably selected from the group consisting of 1,2-dimethoxyethane (DIVIE), / V-propyl- / V-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13-FSI), / V-propyl- / V- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13-TFSI), 1-butyl-l- methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14-FSI), 1-butyl-l- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14-TFSI), l-ethyl-3- methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI), l-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), and propylene carbonate (PC), and their fluorinated equivalents.

[0051] In an alternative embodiment of the present invention, the electrolyte is a solid electrolyte comprising U2S-P2S5; U3PS4; I 7P3S11; LLZO-based materials, for example Li?La3Zr20i2, Li6.24La3Zr2AI0.24On.98, and Li6.4La3Zr1.4Tao.6O12; Lio.34Lao.56Ti03 (LLTO); Lii.3Alo.3Tii.7(P04)3 (LATP); thio-LISICON for example Lii0MP2Xi2(M = Si or Ge; X = S or Se); lithium argyrodite Li6+yMyvMi_yS5X (X = Cl, Br, or I; Mlvis a group IV element for example Si, Ge, or Sn; Mvis a group V element for example P or Sb, and 0 < y < 1); polymer-based solid electrolytes, for example PEO-LiTFSI mixtures; lithium hydrido- borates LixByHz(x = 1 or 2, 1 < y < 12, 4 < z < 14) and lithium hydrido-carba-borates LiCxByHz (x = 1 or 2, 9 < y < 11, 12 < z < 14).

[0052] In a further aspect, the present invention relates to a vehicle comprising a secondary cell according to the first aspect of the present invention.

[0053] In a further aspect, the present invention relates to a method for manufacturing a secondary cell according to the first aspect of the present invention, comprising assembling the cell without inserting any lithium metal. This means that the handling of any lithium metal during manufacture is avoided, which simplifies the manufacturing process. For example, no special equipment modification or dry room conditions will be required to avoid ignition. This also contributes to an improved production speed as well as a reduced cost for manufacturing.

[0054] In some embodiments, the method comprises molding an anode material to produce surface cavities. The cavities may be formed by using a focused laser beam, an ion beam, or mechanical pressure, for example rol l-to-roll pressure or ID hydraulic pressure. In a further aspect, the present invention relates to a secondary cell comprising a molded anode, a cathode, optionally a separator, and an electrolyte, characterized in that the anode comprises an active material or a composition of active materials in multiple layers, and wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode.

[0055] In one embodiment, the molded anode comprises at least two different layers, wherein the layers have different exchange current densities of lithium plating, wherein at least the top layer is molded. In one embodiment, the molded anode comprises from 3 to 5 layers. Each layer of the 3 to 5 layers may have a different exchange current density of lithium plating, wherein at least the top layer is molded.

[0056] In one embodiment, the molded anode does not include a separate current collector layer.

[0057] In one embodiment, the layer closest to the separator is molded and has a surface with lower exchange current density of lithium plating compared to the other layer(s) of the anode.

[0058] In one embodiment, each layer of the anode has a different coating, wherein one layer may not be coated, and the remainder of the layers each has a different coating, and wherein at least the top layer is molded. The coating may be selected from the list of functional layers hereinabove.

[0059] In one embodiment, the particles, and / or coating(s), have been functionalized with a moiety chosen from the group consisting of OH, COOH, CSOH, CONH2, CSNH2, NH, NH2, SH, CN, NO2 and triazolium. In one embodiment, there is a different active material or composition of active materials in each layer of the anode.

[0060] In one embodiment, the active material or composition of active materials of at least one layer comprises metallic lithium.

[0061] In one embodiment, the active material or composition of active materials of each individual layer has been chosen from the group consisting of non-graphitizing carbon, graphite, silicon, silicon oxide (SiOx, x smaller than or equal to 2), silicon-carbon composite, a transition metal dichalcogenide (e.g. titanium disulfide (TiS2)), tin-cobalt alloy, lithium titanate oxide (LTO, Li^isO ), Mxenes (e.g. V2CTX, Nb2CTx, Ti2CTx, and Ti3C2Tx), or a combination of at least two of these.

[0062] In one embodiment, the anode comprises an electronically insulating film coating the layer closest to the separator.

[0063] In one embodiment, the electronically insulating film comprises a material that has been chosen from the group consisting of AI2O3, Piezoelectric materials (e.g. BaTiCh, PbZrxTii-xO3 where x is any number between 1 and 10), U2O, LiF, a fluoropolymer for example polyvinylidene fluoride (PVDF), preferentially in its beta phase, PVDF-HFP, PMMA, PEO, polysiloxane, for example PDMS, lithium polyacrylate (Li-PAA), and mixtures thereof.

[0064] In one embodiment, one of the layers of the anode is a current collector. Alternatively, the anode comprises a separate current collector. The separate current collector may be in the form of a foil, or in the form of a mesh.

[0065] In one embodiment, the foil is coated with a material that has been chosen from the group consisting of C, Si, Sn, Al, Zn, Ag, In, Mg. In a further aspect, the present invention relates to a secondary cell comprising a molded anode, a cathode, optionally a separator, and an electrolyte, characterized in that the anode comprises particles of an active material or a composition of active materials, and a current collector, in one single structure, wherein the structure comprises carbon, silicon, and / or metal oxide(s), and that the molded anode does not comprise any additional current collector, wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode.

[0066] In one embodiment, the structure consists of a material selected from the group consisting of carbon, silicon, and / or metal oxide(s).

[0067] In one embodiment, the molded anode constitutes one layer.

[0068] In one embodiment, the molded anode comprises at least two layers, wherein at least one layer comprises an active electrode material or composition of active materials, and a current collector, in one single structure, and wherein the layers have different exchange current densities of lithium plating.

Claims

CLAIMS1. A molded anode comprising an active material or a composition of active materials, wherein the anode comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode.

2. The molded anode according to claim 1, comprising a substrate and a metal ion storage layer.

3. The molded anode according to claim 2, wherein the metal is lithium.

4. The anode according to claims 2 or 3, wherein the substrate is a current collector.

5. The anode according to any one of claims 2-4, wherein the substrate is selected from any one of metal foil, metal mesh, or metal non-woven, such as copper foil, copper mesh, or copper non-woven; a polymer coated with a conducting material, preferably a metal; a graphite sheet; a sheet comprising carbon nanotubes (CNT), graphene, graphene oxide, carbon nanofibers, and carbon paper.

6. The anode according to claim 1, wherein the cavities are between about 10 and about 2000 pm wide, respectively.

7. The anode according to any one of the above claims, wherein the cavities of the anode are spaced at least 2 pm from each other.

8. The anode according to any one of the above claims, wherein the anode comprises two opposing faces with layers comprising surface cavities.

9. The anode according to any one of the preceding claims, wherein the active material or composition of active materials is selected from any one of non-graphitizing carbon, graphite, silicon, silicon alloy, silicon oxide (SiOx, wherein x is smaller than or equal to 2), silicon-carbon composite, a transition metal dichalcogenide (e.g. titanium disulfide (TiS2)), tin-cobalt alloy, lithium titanate oxide (LTO, Li^isO^), MXenes (e.g. V2CTX, Nb2CTx, Ti2CTx, and Ti3C2Tx), LiisSi^ LiCe, LiisSns, or U9AI4, or a combination of at least two of these.

10. The anode according to any one of the preceding claims, wherein the active material or composition of active materials is at least partially pre-charged with metal ions, such as lithium ions.

11. The anode according to any one of the preceding claims, wherein the particles of active material or composition of active materials have a specific surface area (SSA) of from 0.1 m2 / g to 1000 m2 / g, preferably from 1 m2 / g to 700 m2 / g.

12. The anode according to any one of the preceding claims, wherein the active material or composition of active materials has a porosity in the interval of from 10% to 90% of the total volume of the active material, preferably from 15% to 75%, more preferably from 25% to 50%.

13. The anode according to any one of the preceding claims, wherein the active material or composition of active materials has a minimum porosity as defined by formula (1):where P is the porosity, r is the N / P ratio, Cais the anode specific capacity, or in the case of a composition of active materials the weighted average anode specific capacity, [mAh / g], pais the anode active material density, or in the case of a composition of active materials the weighted average anode active material density [g / cm3], Cu is the lithium capacity [mAh / g] (3862 mAh / g), and pu is the lithium density [g / cm3] (0.53 g / cm3).

14. The anode according to claim 13, wherein the active material or composition of active materials has a porosity in the range of P to 1.5*P, where P is defined as the porosity according to formula (1).

15. A secondary cell comprising a molded anode, a cathode, an electrolyte, and optionally a separator, characterized in that the anode comprises a substrate and a metal ion storage layer comprising an active material or a composition of active materials, wherein the metal ion storage layer is deposited on the substrate, and wherein the metal ion storage layer comprises surface cavities with a depth corresponding to at least 10% of the thickness of the anode.

16. The secondary cell according to claim 15, wherein the cathode loading amount to the anode loading amount (N / P ratio) is 0.01 to 0.99, preferably 0.25 to 0.75, more preferably 0.3 to 0.5, in the uncharged state.

17. The secondary cell according to any one of claims 15 or 16, wherein a functional layer is at least partially coated on the particles of the active material or composition of active materials.

18. The secondary cell according to claim 17, wherein the functional layer comprises surface functional group, for example, OH, COOH, CSOH, CONH2, CSNH2, NH, NH2, SH, CN, NO2 and triazolium, non-graphitizing carbon, a metal or metalloid, for example Si, Sn, Al, Zn, Ag, In, Mg; a metal or metalloid oxide, for example, AI2O3, UAIO2, ZnO, Mn02, CO3O4, SnO2, SiOx(x smaller than or equal to 2), V2O5, CuxO (1 < x < 2), TiO2, I 2O, U2O2, ZrO2, MgO, Ta2Os, Nb20s, UAIO2, Li?La3Zr20i2 (LLZO), Li^isO (LTO), B2O3, LisBCh-I^CCh; a metal fluoride, for example AIF3, LiF; a metal phosphate, for example AIPO4, I 3PO4, Lii.3AI0.3Tii.7(PO4)3 (LATP); piezoelectric material, such as BaTiOs, PbZrxTii-xO3 where x is any number between 1 and 10; a metal hydroxide, such as AIO(OH) (boehmite), Mg(OH)2, AI(OH)3; a metal or metalloid nitride, such as AIN, BN, SisN4; AlfNOsh; BaSO4; or a polymer or polymer electrolyte, containing forexample polyvinylidene fluoride (PVDF), preferably in its beta phase, PVDF-HFP, PMMA, PEO, polysiloxane for example PDMS, lithium polyacrylate (Li-PAA); and mixtures thereof.

19. The secondary cell according to any one of claims 15-18, wherein the substrate is a current collector.

20. The secondary cell according to any one of claims 15-19, wherein the substrate is selected from any one of metal foil, metal mesh, or metal non-woven, such as copper foil copper mesh, or copper non-woven; a polymer coated with a conducting material, preferably a metal; a graphite sheet; a sheet comprising carbon nanotubes (CNT), graphene, graphene oxide, carbon nanofibers, and carbon paper.

21. The secondary cell according to any one of claims 15-20, characterized in that the secondary cell does not comprise any lithium metal when the secondary cell is in its uncharged state.

22. The secondary cell according to any one of claims 15-21, wherein the electrolyte is a liquid electrolyte comprising at least one lithium salt and at least one or more solvents selected from the group consisting of carbonate solvents and their fluorinated equivalents, diCi-4 ethers and their fluorinated equivalents and ionic liquids.

23. The secondary cell according to claim 22, wherein the lithium salt is one or more selected from the group consisting of lithium hexafluorophosphate (LiPFe), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium (fluorosulfonyl) (trifluoromethanesulfonyl) imide (LiFTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium (pentafluoroethanesulfonyl)(trifluoromethanesulfonyl)imide (LiPTFSI), lithium trifluoromethanesulfonate (LiOTf), lithium bis(oxalato)borate (LiBOB), lithiumdifluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium tetrafluoroborate (I BF4), lithium nitrate (UNO3) lithium 2-trifluoromethyl-4,5- dicyanoimidazole (LiTDI).

24. The secondary cell according to claim 22 or 23, wherein the solvent is selected from the group consisting of 1,2-dimethoxyethane (DIVIE), / V-propyl- / V- methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13-FSI), / V-propyl- / V- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13-TFSI), 1-butyl- 1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14-FSI), 1-butyl-l- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14-TFSI), 1-ethyl- 3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI), l-ethyl-3- methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), and propylene carbonate (PC), and their fluorinated equivalents.

25. The secondary cell according to any one of claims 15-21, wherein the electrolyte is a solid electrolyte comprising U2S-P2S5, U3PS4, LiyPsSn LLZO-based materials for example LiyLasZ^O , Li6.24La3Zr2AI0.24On.98, Li6.4La3Zr1.4Tao.6O12; Lio.34Lao.56Ti03 (LLTO), Lii.3Alo.3Tii.7(P04)3 (LATP), thio-LISICON for example U10MP2X12 (M = Si or Ge; X = S or Se), lithium argyrodite Li6+yMyvMi_yS5X (X = Cl, Br, or I; MIVis a group IV element for example Si, Ge, or Sn; Mvis a group V element for example P or Sb, and 0 < y < 1), polymer based solid electrolytes, for example PEO-LiTFSI mixtures, lithium hydrido-borates LixByHz(x = 1 or 2, 1 < y < 12, 4 < z < 14) and lithium hydrido-carba-borates LiCxByHz(x = 1 or 2, 9 < y < 11, 12 < z < 14).

26. A method for manufacturing a secondary cell according to any one of claims 15-25, comprising assembling the cell without inserting any lithium metal.

27. The method according to claim 26, further comprising molding an active material layer to form surface cavities.

28. The method according to claim 26, wherein a focused laser beam is used to form the cavities.

29. The method according to claim 26, wherein an ion beam is used to form the cavities.

30. The method according to claim 26, wherein mechanical pressure is used, for example rol l-to-rol I press, or a ID hydraulic press, to form the cavities.

31. A vehicle comprising an anode or a secondary cell according to any one of claims1-30.

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