Macroporous silver-carbon composite material

Abstract

The present invention relates to a porous silver-carbon composite material containing a carbon powder. The carbon powder contains porous carbon particles, wherein the carbon particles contain pores having an open and continuous pore structure. Furthermore, the porous silver-carbon composite material contains silver particles, wherein at least some are bound to the surface of the porous carbon particles. The silver-carbon composite material can be used for electrodes of solid-state batteries.

Description

[0001] This invention relates to a porous silver-carbon composite material, a method for producing the porous silver-carbon composite material, and the use of the material in a solid-state battery.

[0002] Battery-powered applications are now indispensable in most aspects of life. Lithium-ion batteries are the most commonly used. Modern standard lithium-ion batteries use liquid electrolytes. The advantages of liquid electrolytes are high ionic conductivity, which enables rapid charging and discharging. Furthermore, these electrolytes exhibit high chemical stability, ensuring a high level of safety and preventing unwanted side reactions. Low viscosity results in good ion transport within the battery cell. The disadvantages of liquid electrolytes are the battery's high flammability and limited operating temperature.

[0003] One way to improve energy density and safety compared to existing lithium-ion batteries is to use solid-state batteries. These no longer contain any liquid electrolyte that could leak out. In particular, they offer high lithium-ion conductivity (1-25 mS / cm) at room temperature, comparable to conventional liquid electrolytes. -1 Sulfide solid electrolytes (SSEs) are the most suitable solid electrolytes for use in batteries for electric vehicles (EVs).

[0004] article High-energy long-cycling all-solid-state lithium metal batteries enabled by silver-carbon composite anodes (Nature Energy, Vol. 5, pp. 299-308 (2020) https: / / doi.org / 10.1038 / s41560-020-0575-z, hereinafter referred to as " Nature EnergyThis paper describes a simplified solid-state battery based on a sulfide solid electrolyte, exhibiting a very high energy density exceeding 900 Wh / L. The following layer structure is used: an NMC active material layer is used as the cathode. An argyrodite-type solid sulfide electrolyte layer is then placed on top of this. An Ag-C nanocomposite layer is then applied to this solid electrolyte, which is further coupled with a stainless steel charge collector (current collector). The collector is used as the contact. A mixture of silver nanoparticles (NP), carbon black, and polyvinylidene fluoride binder in a weight ratio of 1:3 is used as the silver-carbon (Ag-C) nanocomposite. In this arrangement, no dedicated anode material is placed on the anode side. More specifically, during charging, lithium migrates to the charge collector and deposits between the silver-carbon layer and the charge collector. This makes it possible to achieve an exceptionally thin lithium layer in foil form, which can only be introduced into this structure with great difficulty. One drawback of the described Ag-C composite is that the silver nanoparticles are loosely mixed with carbon and migrate over several charge and discharge cycles. The gradual migration of the silver nanoparticles to the charge collector is described.

[0005] In addition, Nature Energy The text describes how the battery material must be compressed under relatively high pressure. This reduces the porosity of the structure, particularly the porosity of the Ag-C nanocomposite, which in turn leads to a decrease in the mobility of charge carriers.

[0006] Another typical problem with loose mixtures of silver particles and other particles is so-called Ostwald ripening. Here, large silver particles grow at the expense of smaller ones. This alters the size of the silver particles during electrochemical operation and reduces the electrochemical activity of the material.

[0007] One object of the present invention is to overcome at least one disadvantage of the prior art.

[0008] In particular, an object of the present invention is to provide a silver-carbon composite material for battery electrodes, wherein silver migration is reduced so that the material can maintain its original structure for a longer period of time as part of the anode.

[0009] Another preferred objective is to provide a silver-carbon composite material with improved permeability to lithium and lithium ions.

[0010] In addition, one objective is to provide a simple method for producing improved silver-carbon composite materials.

[0011] Another preferred objective is to provide a silver-carbon composite material that can be processed under lower pressure.

[0012] At least one objective is achieved through the subject matter of the independent claims. The dependent claims describe preferred embodiments.

[0013] The first aspect of the present invention relates to a porous silver-carbon composite material comprising:

[0014] a) Carbon powder containing porous carbon particles, said carbon particles having pores with open and continuous pore structures, and

[0015] b) Silver particles, at least some of which are bound to the surface of the porous carbon particles, particularly the accessible surface.

[0016] In the porous silver-carbon composite material of the present invention, Ostwald ripening of silver particles can be significantly reduced or suppressed. This can greatly slow down the aging of the material as part of a battery electrode.

[0017] Composite materials are materials in which two or more components exist as distinct substances, in this case carbon and silver, which are bonded or mixed together. Preferably, these components are bonded to each other at least partially via chemical bonds, particularly ionic or covalent bonds.

[0018] Preferably, the carbon in the porous silver-carbon composite material is amorphous, graphitic, non-graphitic, or a combination of these variations. The porous silver-carbon composite material is further preferably a powder.

[0019] This porous silver-carbon composite material contains carbon powder. This carbon powder contains porous carbon particles, with silver particles bonded to its surface, particularly through chemical deposition.

[0020] The porous carbon particles in this silver-carbon composite material exhibit a particle size distribution. The median particle size d of the porous carbon particles in this silver-carbon composite material is... 50 Preferably, the porous carbon particles are in the range of 1 µm to 5 µm. These porous carbon particles may have a single-peak, double-peak, or multi-peak distribution. In a preferred embodiment, the porous carbon particles are not carbon black.

[0021] This porous silver-carbon composite material exhibits a pore size distribution. In this case, micropores with a pore diameter < 2 nm, mesopores with a pore diameter of 2 nm to 50 nm, and macropores with a pore diameter > 50 nm are distinguished. The median pore size of this porous silver-carbon composite material is preferably in the range of > 50 nm to 280 nm, particularly in the range of 60 nm to 250 nm. The median pore size is especially preferably in the range of 75 nm to 150 nm.

[0022] Preferably, the pore volume of the micropores in the porous silver-carbon composite material is 0.01 - 0.5 cm³ g. -1 Especially 0.02 - 0.25 cm 3 g -1 The pore volume of macropores is, for example, 0.3 - 0.5 cm³ g. -1 Within the range of [specific parameters]. More preferably, the macropore volume of the silver-carbon composite material accounts for at least 30% or at least 40% of the total pore volume, particularly at least 50%. The total pore volume of the porous silver-carbon composite material, measured by mercury porosimetry, particularly the pores in the range of 10 nm to 1000 nm, is preferably between 0.2 cm³ / g and 1.0 cm³ / g. 3 Within the range of / g.

[0023] The carbon powder of the present invention can be obtained, for example, under the name Porocarb from Heraeus Battery Technology GmbH, Germany. This porous carbon material can alternatively be produced using Alnovol PN 320 Past and Genapol PF20 in a ratio of 10:6, in combination with Example 2 of WO2019081732A1 and Table 2.

[0024] The porous carbon particles in this porous silver-carbon composite material have an open and continuous pore structure. This means that preferably at least 50% of the pore volume, particularly at least 75% of the pore volume, or very particularly preferably at least 90% of the pore volume, is externally accessible. The open and continuous pore structure can be determined, for example, using a 3D representation of the primary particles formed by FIB / SEM tomography. In a preferred embodiment, the tortuosity of the porous carbon particles can be in the range of 1.5-3. One advantage of the open and continuous pore structure is the improved permeability of lithium atoms and lithium ions through the porous carbon particles.

[0025] This porous carbon composite material contains silver particles. At least some of the silver particles are bound to the surface of the porous carbon particles. This binding is preferably via chemical bonding. Chemical bonds can be, for example, covalent, ionic, or coordinate bonds. This binding can preferably be achieved by direct deposition of silver particles as elemental silver (through the reduction of a silver precursor compound). In particular, "binding" does not involve the physical adhesion of silver particles mixed into the porous carbon material.

[0026] Preferably, based on the total weight of the porous carbon composite material, the proportion of silver particles is in the range of 2-45% by weight, particularly in the range of 5-10% by weight. The median particle size d of the silver particles... 50 Preferably, the particle size is in the range of 5 nm to 150 nm, particularly in the range of 10 nm to 120 nm, and especially preferably in the range of 20 nm to 110 nm. It has proven advantageous that the median particle size d of the silver particles... 50 The particle size is at least 5 nm, particularly at least 10 nm, and especially preferably at least 20 nm. The particle size can be determined by XRD using the Deby-Scherer method with the Bragg equation at 111 reflex.

[0027] In one possible implementation, at least some silver particles are arranged in the pores of the porous carbon particles in the silver-carbon composite material, particularly in the macropores.

[0028] In a particularly preferred embodiment, silver particles are uniformly distributed in the porous silver-carbon composite material. This distribution can be determined using a scanning electron microscope with spatially resolved EDX.

[0029] In a preferred embodiment, the porous carbon composite material is free of metals other than silver, and in particular, free of intentionally added metals. This does not involve unavoidable impurities. The weight-related amount of unavoidable metal impurities may be, for example, at most 1000 ppm or at most 500 ppm.

[0030] The specific surface area of ​​porous silver-carbon composite materials, as determined by the BET method, is preferably between 50 m² / g and 800 m² / g. 2 Within the range of / g.

[0031] In a second aspect, the present invention relates to a method for producing the porous carbon composite material, comprising the following steps:

[0032] a) Provide carbon powder and silver precursor compounds containing porous carbon particles with open and interconnected pore structures;

[0033] b) Combine the carbon powder with the silver precursor compound in a solvent.

[0034] c) Convert the silver precursor compound into elemental silver to obtain a suspension of the porous carbon composite material, and

[0035] d) Separate the porous silver-carbon composite material.

[0036] Preferably, the carbon in the carbon powder is amorphous, graphitic, non-graphitic, or a combination of these variations.

[0037] Carbon powder contains porous carbon particles. These porous carbon particles exhibit a particle size distribution. The median particle size d of the porous carbon particles in the carbon powder is... 50 Preferably, the porous carbon particles are in the range of 1 µm to 5 µm. These porous carbon particles may have a single-peak, double-peak, or multi-peak distribution. In a preferred embodiment, the porous carbon particles are not carbon black.

[0038] The pores of carbon powder exhibit a pore size distribution. In this case, micropores with a diameter <2 nm, mesopores with a diameter from 2 nm to 50 nm, and macropores with a diameter >50 nm are distinguished. The median pore size of the carbon powder is preferably in the range of >50 nm to 280 nm, particularly in the range of 60 nm to 250 nm. The median pore size of the carbon powder is especially preferably in the range of 75 nm to 150 nm.

[0039] Preferably, the micropore volume in the carbon powder is 0.01 - 0.5 cm³ g. -1 Especially 0.02 - 0.25 cm 3 g -1 The pore volume of macropores is, for example, 0.3 - 0.5 cm³ g. -1 Within the specified range. Preferably, the macropore volume of the carbon powder accounts for at least 30%, particularly at least 50%, of the total pore volume. The total pore volume of the carbon powder, measured by mercury porosimetry, particularly the volume of pores in the range of 10 nm to 1000 nm, is preferably between 0.2 cm³ / g and 1.0 cm³ / g. 3 Within the range of / g.

[0040] The carbon powder of the present invention can be obtained, for example, under the name Porocarb from Heraeus Battery Technology GmbH, Germany. This porous carbon material can alternatively be produced using Alnovol PN 320 Past and Genapol PF20 in a ratio of 10:6, in combination with Example 2 of WO2019081732A1 and Table 2.

[0041] In addition, at least one silver precursor compound is provided. The silver precursor compound may be selected from silver salts and silver complexes. Preferably, the silver precursor compound is a silver(I) compound. Examples of silver(I) compounds are silver acetate, silver nitrate, silver halide, and silver sulfate.

[0042] Preferably, the silver precursor compound is present in solution. Suitable solvents may be selected, for example, from aqueous solvents and polar organic solvents. In particular, the solvent is water.

[0043] The silver precursor compound may optionally be partially or completely dissolved in the solvent; complete dissolution is particularly preferred. For example, a solution containing at most 0.5% by weight of the silver precursor compound in solid form can be considered completely dissolved. In an optional embodiment, no other metal or metal compound is provided besides the silver precursor compound.

[0044] Carbon powder is combined with a silver precursor compound in a common solvent. In this invention, the solvent may also be mentioned in relation to the carbon powder, although the carbon powder does not dissolve in the solvent but forms a suspension of porous carbon particles. Optionally, a suspension of porous carbon particles can be prepared first, to which the silver precursor compound is added. Alternatively, the porous carbon particles can be added to an existing solution of the silver precursor compound. In another alternative, the suspension of porous carbon particles and the solution of the silver precursor compound are combined with each other. In this case, the suspending agent of the carbon particles and the solvent of the silver precursor compound can be the same or different. Preferably, the respective solvents or suspending agents are miscible with each other. The solvents or suspending agents within the scope of this invention can be organic or aqueous. Preferred organic solvents or suspending agents are polar.

[0045] In step c), the silver precursor compound is converted into elemental silver in its oxidized state. This conversion is preferably carried out by adding a reducing agent, by temperature, or by exposure to light. Preferably, the conversion is carried out by adding a reducing agent. Particularly preferably, the pH of the suspension is adjusted to a value greater than 8, particularly greater than 8.5, prior to the conversion. The choice of reducing agent is preferably not further limited, and those skilled in the art of particle synthesis can choose a suitable reducing agent for their respective silver precursor compounds. The reducing agent is particularly preferably a nitrogen-containing reducing agent, such as hydrazine. Preferably, the reducing agent used can be removed from the reaction without leaving any residue.

[0046] After conversion to elemental silver, the porous carbon composite material is separated. For separation, known methods such as filtration, centrifugation, or similar methods can be used.

[0047] In a third aspect, the present invention relates to a battery electrode comprising the aforementioned porous silver-carbon composite material. This battery electrode is preferably an anode, particularly an anode for a solid-state battery. Optionally, the battery electrode may contain a binder, such as polyvinylidene fluoride.

[0048] Preferably, the battery electrode may further comprise lithium, particularly in the form of a lithium layer. The lithium layer may preferably be an in-situ deposited lithium layer. The deposited lithium is preferably derived from the cathode material of the solid-state battery and migrates through the electrochemical cell during charging to the charge collector on the side where the anode is to be formed. In this case, a porous carbon composite material can act as a separator between the solid electrolyte and the charge collector (e.g., steel foil). In-situ deposition of lithium between a carbon and silver layer (Ag-C) and the charge collector (e.g., stainless steel foil) is described, for example, in Nature Energy.

[0049] The use of porous silver-carbon composite materials can lead to improved lithium redox reactions, thus enabling solid-state batteries to charge and discharge faster overall.

[0050] In a fourth aspect, the present invention relates to a solid-state battery comprising the porous carbon composite material of the present invention. Preferably, according to Nature Energy The powder mixture of carbon black and silver nanoparticles in the battery can be replaced by the porous carbon composite material of the present invention.

[0051] In this case, the solid-state battery preferably has the following structure: A lithium layer is arranged on a charge collector, for example, which may be made of steel. The porous silver-carbon composite material of the present invention is arranged on the lithium layer. A solid electrolyte is then arranged on the silver-carbon composite material, and a cathode material, such as NMC material known in the prior art, is arranged on the solid electrolyte.

[0052] The preferred aspects of the invention are explained below with reference to the illustrations.

[0053] Figure 1 This is a schematic diagram of the particles in a silver-carbon composite material.

[0054] Figure 2 This is a schematic diagram of a cross-section through a solid-state battery according to the present invention.

[0055] Figure 1The silver-carbon composite material shown contains porous carbon particles (60). These porous carbon particles have pores, which can be open pores (66) and accessible from the outside, or closed pores (65) inaccessible from the outside. Silver particles (50) are arranged on the accessible surfaces of the porous carbon particles (60). These silver particles (50) preferably have a median diameter d of, for example, 70 nm. 50 Nanoparticles can be arranged on the outer surface of porous carbon particles (60) or in open pores (66).

[0056] Figure 2 This illustrates a schematic layer structure of a solid-state battery. In this case, Figure 2 A shows a cathode material layer (10), which may be, for example, an NMC material (NMC layer (nickel-manganese-cobalt oxide)). A solid electrolyte layer (20) is disposed thereon. The solid electrolyte layer (20) is brought into contact with a silver-carbon composite material layer (30) according to the invention. To extract charge, a charge collector (40) (which may be, for example, a steel foil) is disposed on the silver-carbon composite material (30). The layer structure shown preferably corresponds to the state of the solid-state battery before the first charge.

[0057] Figure 2 B Display and Figure 2 The same solid-state battery shown in A differs in that a lithium layer (35) is arranged between a silver-carbon composite material (30) and a charge collector (40). This lithium layer (35) is preferably formed by lithium ions migrating from the cathode material (e.g., NMC 622 or NMC 811) to the charge collector and depositing thereon during the solid-state battery charging process. Alternatively, the lithium layer can be introduced directly during the solid-state battery manufacturing process.

[0058] Measurement methods

[0059] Mercury porosimetry

[0060] Total pore volume, specific pore volume, and pore size were determined by mercury pore measurement according to DIN ISO 15901-1:2016. Measurements were performed using a Porotec Pascal 140 + 440 apparatus. Measurement details are summarized as follows: sample mass 30 mg; mercury surface tension 0.48 N / m; mercury contact angle 141.3°; measurement method: scanning; starting filling pressure 0.0128 MPa; dilatometer: powder, small volume. For sample preparation, the sample was degassed under vacuum at 110 °C for 8 hours. Prior to measurement, calibration was performed using porous glass spheres (ERM-FD122 BAM reference material) with a modal pore diameter of 140.2 nm and a pore volume of 924.4 mm³. The Washburn method was used for this evaluation, and the density of Hg was corrected for the current temperature.

[0061] Particle size distribution

[0062] Laser diffraction (D) 10 D 50 D 90 ) :

[0063] To determine particle size, laser diffraction was performed according to ISO standard 13320:2020. A Malvern Mastersizer 3000 equipped with a He-Ne laser (632.8 nm wavelength, 4 mW maximum power), a blue LED (470 nm wavelength, 10 mW maximum power), and a hydro-dispersion unit (Hydro MV) was used for measurements at an ambient temperature of 23°C. A mixture of isopropanol and deionized water (50% / 50%) was used as the measurement medium. This mixture was degassed in the dispersion unit using a built-in stirrer at 3500 rpm and exposed to ultrasound at maximum power for 10 seconds. The sample material was placed in a 5% IGEPAL solution. The sample was pre-dispersed with an ultrasonic probe for 30 seconds. The sample was added dropwise to the dispersion unit using a pipette until the transmittance of the laser beam decreased by 3-7%. Dsize was determined using Malvern Software Mastersizer 3000 software 3.30. 10 D 50 and D 90 The value (based on volume). Fraunhofer theory is used for samples where particles > 10 μm, and Mie theory is used for materials where particles < 10 μm.

[0064] Specific surface area (SSA)

[0065] Nitrogen physisorption measurements for determining the specific surface area of ​​particles were performed according to DIN ISO 9277:2010. For this measurement, a NOVA 3000 (from Quantachrome) was used, operated according to the SMART method (Sorption Method with Adaptive Dosing Rate). Quantachrome alumina SARM catalog number 2001 (13.92 m² according to the multi-point BET method) was used. 2 / g) and SARM catalog number 2004 (214.15 m according to the multi-point BET method). 2 / g) as reference material. A filling rod was added to both the reference and sample measuring cells to reduce dead volume. The measuring cell was inserted into the BET apparatus. The saturated vapor pressure of nitrogen (N2 4.0) was determined. The sample was weighed into the glass measuring cell, precisely the amount that would completely fill the cell with the filling rod and create a minimum dead volume. The sample was dried under vacuum at 200°C for 10 hours. After cooling, the weight of the sample was determined. The glass measuring cell with the sample was placed on the measuring apparatus. To degas the sample, it was evacuated to a final pressure of 10 mbar using a pump selected to prevent any material from being drawn into the pump. Data analysis was performed using NovaWin 11.04 software. A multipoint analysis with 15 measuring points was performed, and the total specific surface area (BET) was obtained. total ) with m 2 / g is the unit specified. The glass measuring cell was cooled to 77 K in a liquid nitrogen bath. For adsorption, the molecular cross-sectional area at 77 K is 0.162 nm. 2 N2 4.0 is used for this calculation.

[0066] According to ISO 15901-3:2007, the empirical t-plot method is used to distinguish the contributions from micropores and other pores (i.e., contributions from mesopores, macropores, and external surface area) under relative pressures greater than 0.1, and the micropore surface area (BET) is calculated. micro ) and micropore volume. Data points on the low-pressure isotherm are selected up to the cut-off p / p0, typically up to 0.1 p / p0, to determine the linear portion of the t-plot. The selection of data points is verified by obtaining a positive C constant. Micropore volume is determined from the ordinate intersection point. The specific surface area of ​​the micropores (BET) microThe external specific surface area (BET) can be calculated from the slope of the t-plot. It is defined by subtracting the specific surface area of ​​the micropores from the total specific surface area. external BET external = BET total - BET micro .

[0067] FIB / SEM tomography

[0068] Tomography, which combines focused ion beam (FIB) and scanning electron microscopy (SEM), is used to obtain information about the 3D microstructure of porous carbon particles.

[0069] The method includes the following steps:

[0070] - Sample preparation

[0071] - Repeated milling using FIB and 2D image acquisition using SEM

[0072] - 3D reconstruction of the structure of porous carbon materials from a set of 2D images by stacking.

[0073] - Creating models through segmentation reconstructed from 3D images, and

[0074] - Analyze porosity on the created model.

[0075] Sample preparation: The porous carbon material was mixed with 5% by weight of binder and rolled into a layer. A piece can be prepared from this sample for FIB / SEM processing.

[0076] The ZEISS 1540XB CrossBeam® (Carl Zeiss AG, Oberkochen, Germany) was used for image capture. Here, a thin layer of the sample was precisely milled away using an accelerated Ga ion beam (FIB), followed by image acquisition using an electron beam (SEM). This process was repeated hundreds of times to obtain a continuous set of images. These images form the basis of the 3D reconstruction. Images were acquired with a 15 nm spacing between consecutive images, and each image contained pixels of 15 nm in size. The dataset was first subjected to brightness gradient correction along the imaging direction and further processed with an anisotropic diffusion filter to clearly distinguish pores and carbon. The images were then stacked and aligned in three dimensions using the software tools ImageJ and Matlab. This yielded a digital 3D representation of the porous carbon material.

[0077] In the next step, segmentation is achieved through the 3D representation obtained by image stacking. In this case, segmentation refers to computing a 3D model based on the reconstructed image, thereby assigning each volume element (voxel) to the carbon material or pores.

[0078] The image data was segmented using an algorithm derived from the region-growing segmentation algorithm. A detailed description of the algorithm is provided in "Quantification of double-layer Ni / YSZ fuel cell anodes from focused ion beam tomography data", J Joos et al., J. of power sources 246, 819-830 (2014).

[0079] The model obtained through image segmentation can be analyzed in terms of porosity, i.e., whether the pores are connected to a pore network that is connected to the environment, or whether the pores are isolated and not connected to the environment. Pores that can be accessed from the surface of primary particles can be understood as open pores.

[0080] Tortuosity

[0081] To determine the tortuosity, an analysis was conducted on a 7.5 x 7.5 x 4.5 μm sample. 3 The sample volume corresponds to a 500x500x300 voxel obtained through segmentation. This model is used to obtain information about porosity using a coarse-grained 3D model based on the finite element method (FEM) with equally sized cubes. Homogenization methods are used in this modeling to determine the effective electrical conductivity σ. effThe tortuosity can be derived from the effective conductivity. To this end, the method involves filling the pore volume with a material having a given bulk conductivity σ0. The porous structure leads to a decrease in effective conductivity compared to the initial conductivity. This decrease in conductivity is directly related to the tortuosity by Equation 1 specified below. For this purpose, a mesh is created by converting each voxel of the investigated phase (in the segmented model) into a cubic 8-node element. In this case, only voxels connected via faces (not just edges or corners) are added to the mesh to avoid singularities at the model boundaries. Isoelectric values ​​are applied to the two opposing outer surfaces (1 V on the upper surface and 0 V on the lower surface). A zero-flow boundary condition is applied to the remaining four outer surfaces and the interface between the two phases (material and pores). As described by J. Joos et al., Journal of Power Sources 196 (2011) and M. Ender et al., Electrochemistry Communications 13 (2011) 166, the transport equations are solved using the FEM (finite element method):

[0082]

[0083] Specify the intrinsic conductivity σ0 of the material. The tortuosity τ can then be calculated using the following formula:

[0084]

[0085] Formula 1

[0086] Porosity

[0087] ε = N i / N total ,in

[0088] N i = The number of voxels in porous phase i, and

[0089] N total ,: The total number of voxels in the segmented model.

[0090] If the dataset for a coarse-grained 3D-FEM model is too large for the available computational power, the created model can be extended, for example, to a high-resolution 3D FEM model based on C++ code. Details of tortuosity calculation are given in J. Joos et al. Electrochimica Acta 82 (2012) 268-276 (Chapter 7 Calculation of microstructure parameters).

[0091] Implementation Plan

[0092] Example 1

[0093] An aqueous solution prepared from 9.45 g of silver nitrate (silver content 63.69 wt%; 55.63 mmol Ag) and 100 mL of water was rapidly added to a suspension of 14.15 g of porous carbon (available as Porocarb L11, Heraeus Battery Technology GmbH, Germany) in 1000 mL of deionized water. This suspension was stirred at 75 °C for 12 h. The pH of the suspension was then adjusted to 9 using a 10 wt% sodium hydroxide aqueous solution. Subsequently, a solution consisting of 2 g of hydrazine solution (hydrazine content 35 wt%), 9.65 g of sodium hydroxide, and 40 mL of water was metered in over 0.5 h (1.3 mL / min), and stirred for another 1 h. The suspension was then cooled overnight (12 h) with stirring, the material was filtered, and washed with a total of 15 L of warm water. Finally, the material was dried in a drying oven at 110 °C under vacuum and nitrogen.

[0094] The silver content of the product was determined to be 32.18% by weight (based on 0% residual moisture) by thermogravimetric analysis.

[0095] Example 2

[0096] An aqueous solution prepared from 9.45 g of silver nitrate (63.69 wt% silver content; 55.63 mmol Ag) and 100 mL of water was rapidly added to a suspension of 14.15 g of porous carbon (available as Porocarb L11, Heraeus Battery Technology GmbH, Germany) in 1000 mL of deionized water. This suspension was stirred at room temperature for 1 hour. The pH of the suspension was then adjusted to 9 using a 10 wt% sodium hydroxide aqueous solution. Subsequently, a solution consisting of 2.8 g of hydrazine solution (35 wt% hydrazine content), 9.65 g of sodium hydroxide, and 50 mL of water was added metered over 0.5 hours (1.3 mL / min). The mixture was then heated to 60 °C and stirred for another 3 hours. After acidification to pH 4.2 with dilute nitric acid, the suspension was cooled overnight (12 hours) while stirring. The material was then filtered and washed with a total of 10 L of warm water until a conductivity of 3.2 was achieved. Finally, the material was dried in a drying oven at 110°C under vacuum and protective nitrogen.

[0097] The silver content of the product was determined to be 31.53% by weight (based on 0% residual moisture) by thermogravimetric analysis.

Claims

1. A porous silver-carbon composite material, comprising: a) Carbon powder containing porous carbon particles, wherein the carbon particles contain pores with open and continuous pore structures, and b) Silver particles, at least some of which are bonded to the surface of the porous carbon particles.

2. The porous silver-carbon composite material according to claim 1, wherein the porous silver-carbon composite material has macropores, wherein the proportion of macropore volume in the total pore volume is at least 30% as measured by mercury porosimetry.

3. The porous silver-carbon composite material according to claim 1 or 2, wherein at least some silver particles are chemically bonded to the surface of the porous carbon particles.

4. The porous silver-carbon composite material according to any one of claims 1-3, wherein the proportion of silver particles is in the range of 2-45% by weight based on the total weight of the porous silver-carbon composite material.

5. The porous silver-carbon composite material according to any one of claims 1-4, wherein the total pore volume of the porous silver-carbon composite material, measured by mercury porosimetry, is between 0.2 cm³ / g and 1 cm³ / g. 3 Within the range of / g.

6. The porous silver-carbon composite material according to any one of claims 1-5, wherein the median pore size of the porous silver-carbon composite material, as measured by mercury porosimetry, is in the range of 50 nm to 280 nm.

7. The porous silver-carbon composite material according to any one of claims 1-6, wherein the median particle size d of the silver particles, as measured by XRD, is... 50 Within the range of 5 nm to 150 nm.

8. The porous silver-carbon composite material according to any one of claims 1-7, wherein the median particle size d of the porous carbon particles in the silver-carbon composite material is measured by laser diffraction. 50 Within the range of 1 µm to 5 µm.

9. The porous silver-carbon composite material according to any one of claims 1-8, wherein the specific surface area of ​​the porous silver-carbon composite material, measured by BET, is between 50 m² / g and 800 m² / g. 2 Within the range of / g.

10. A method for producing a porous silver-carbon composite material according to any one of claims 1-9, comprising the following steps: a) Provides a carbon powder containing porous carbon particles and a silver precursor compound, wherein the porous carbon particles have an open and interconnected pore structure. b) Combine the porous carbon powder with the silver precursor compound in a solvent. c) Convert the silver precursor compound into elemental silver to obtain a suspension of the porous carbon composite material, and d) Separate the porous silver-carbon composite material.

11. The method according to claim 10, wherein the silver precursor compound is selected from silver salts and silver complexes.

12. The method of claim 11, wherein the silver precursor compound is present in solution.

13. The method of claim 12, wherein the initiation of the conversion reaction is achieved by adding a reducing agent, particularly a nitrogen-containing reducing agent.

14. A battery electrode comprising a porous silver-carbon composite material according to any one of claims 1-9.

15. The battery electrode of claim 14, wherein the battery electrode is the anode of a solid-state battery.

16. A solid-state battery comprising a porous silver-carbon composite material according to any one of claims 1-9.

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