Electrochemical primary cell as well as multi-cell battery and use of nano-particulate silicon agglomerates

Abstract

The invention relates to an electrochemical primary cell with an anode, a cathode, an electrolyte, and at least one separator. The cathode comprises preferably manganese dioxide as the material and optionally a carbon-containing conductivity promoter, and the anode comprises silicon as the anode material, said silicon being provided in the form of silicon particles having silicon primary particles which have a particle size between 1 nm and 3000 nm and which are optionally substantially amorphous. The invention additionally relates to a multi-cell battery comprising at least two primary cells which are connected together in series and to the use of silicon as the anode material in the form of silicon particles that are provided as silicon primary particles which have a particle size between 1 nm to 3000 nm and which form agglomerates and / or aggregates, wherein the anode material does not comprise lithium in the charged state, and the silicon primary particles are optionally substantially amorphous.

Description

[0001] Electrochemical primary cell and multi-cell battery and use of nano-particulate silicon agglomerates

[0002] The invention relates to an electrochemical primary cell having an anode, a cathode, an electrolyte and at least one separator, wherein the cathode preferably comprises manganese dioxide as material and optionally a carbon-containing conductivity promoter, wherein the anode comprises silicon as anode material, the silicon being in the form of silicon particles, and the silicon particles having silicon primary particles with a particle size between 1 nm and 3000 nm, and the particles are optionally substantially amorphous.Furthermore, the invention comprises a multi-cell battery with at least two primary cells connected in series and also the use of silicon as anode material in the form of silicon particles which are present as silicon primary particles with a particle size between 1 nm and 3000 nm and form agglomerates and / or aggregates, wherein the anode material in the charged state does not comprise lithium and wherein the silicon particles are optionally substantially amorphous.

[0003] Due to the growing demand for e-mobility in local public transport through electric cars, electric bicycles, and electric buses, as well as the increasing use of decentralized power generation, there is a huge demand for environmentally friendly batteries whose components should be both infinitely available and infinitely recyclable, environmentally friendly, and / or reusable. Silicon is a raw material with unlimited availability on Earth. Furthermore, battery components must be available at low cost.

[0004] Furthermore, it is known that electrical energy can be generated by continuously supplying fuel to fuel cells that have a galvanic cell in the presence of an oxidizing agent. In principle, this principle is also conceivable for silicon-air batteries. Furthermore, conventional silicon-containing lithium-ion secondary batteries are in daily use worldwide.

[0005] The object of the invention was to provide a silicon-containing galvanic cell in an economical manner which can provide a good power density and a high starting voltage. A further object was to provide a silicon-containing galvanic cell which is preferably free of lithium, where preferably free of lithium means that the lithium content in the charged state is less than 0.1 wt. % in the overall composition of the primary cell, in particular comprising the anode, the cathode and the electrolyte, and preferably the lithium content in the electrode material of the anode in the charged state is less than 0.1 wt. %. The galvanic cell should preferably comprise reactants and reaction products which originate from recycling processes, are by-products and / or can be reused in recycling processes.Surprisingly, the inventors have found that specific silicon particles can be used as active components in a galvanic cell and can achieve significant power densities up to unexpectedly high power densities of greater than or equal to 3 mW / cm in a single specific electrochemical primary cell. 2 The highest power densities were achieved with fluoride-containing electrolytes. Good power density results were also achieved with ionic liquids. Good power densities were also measured with electrolytes containing ammonium chloride and sodium carbonate, using agglomerated and / or aggregated silicon primary particles as the anode material. In all experiments, the best power densities for silicon-containing primary cells were achieved with electrochemically treated or produced carbon black and conductive carbon black.

[0006] According to the invention, agglomerated silicon primary particles or silicon agglomerates are understood to be silicon primary particles that essentially touch each other at corners and edges, rather than at their surfaces. Agglomerates (Figure 14) can be broken down into aggregates (Figure 13) and the silicon primary particles (Figure 12) during dispersion. Furthermore, aggregates (Figure 13) are understood to be primary particles that have grown together, melted together, or are agglomerated and can only be separated from each other under the application of mechanical force.

[0007] Preferred primary cells of the invention are preferably free of lithium, wherein preferably free of lithium is understood to mean that the lithium content in the charged state in the primary cell, in particular comprising the anode, the cathode and the electrolyte, is less than or equal to 1 wt. %, in particular less than or equal to 0.1 wt. % in the primary cell; preferably the lithium content in the electrode material of the anode in the charged state is less than or equal to 0.1 wt. %. Electrochemical primary cells and in particular anodes for electrochemical processes with a lithium content of less than 1 wt. %, preferably less than or equal to 0.1 wt. %, are considered to be free of lithium and are referred to according to the invention as pure silicon cells or pure silicon anodes.

[0008] Furthermore, an economical cathode material is to be provided which preferably comprises a physical mixture of manganese dioxide (MnO2) and a conductivity promoter. The optional content of the conductivity promoter in the electrodes of the primary cell can vary in the cathode and the anode. For manganese dioxide, a conductivity promoter content of approximately 5 to 65 wt.%, preferably 5 to 15 wt.%, is usual in the cathode material. In general, the conductivity promoter content can be 5 to 60 wt.% in the cathode material. Alternatively, preferred contents can be in the range of 15 to 20 wt.% for a lower resistance, or 30 to 60 wt.% as an upper limit. The total cathode material always amounts to 100 wt.%.

[0009] The invention thus relates to at least one electrochemical primary cell which has an anode, a cathode, an electrolyte and at least one separator, wherein the separator separates the cathode and the anode from one another, and the cathode comprises manganese dioxide as material and optionally a carbon-containing conductivity promoter, wherein the anode comprises silicon as anode material and wherein the silicon is in the form of silicon particles and the silicon primary particles have a particle size between 1 nm and 3000 nm, and the primary particles are optionally substantially amorphous. It is particularly preferred if the silicon particles, and in particular the silicon primary particles, have a crystallinity of less than or equal to 20%, in particular 12%, in particular a crystallinity of less than or equal to 2%. Silicon primary particles with a crystallinity of less than 12%, preferably less than 2%, are considered amorphous.

[0010] Preferably, the silicon particles in the anode are present as aggregates and optionally the lithium content is less than or equal to 0.1 wt.% with respect to the silicon content of the anode of 100 wt.% of the primary cell, wherein the lithium content is preferably less than or equal to 0.1 wt.% in the charged state of the primary cell.

[0011] A powder is considered essentially amorphous if it is X-ray amorphous. A powder with a crystallinity of less than 20%, preferably less than 12%, and particularly preferably less than or equal to 2% is considered X-ray amorphous. The degree of crystallinity can be determined using XRPD using the formula % crystallinity = (100 x A) / (A + B -C) where A = total peak area of ​​the reflections of the crystalline components of the diffractogram; B = total area below peak area A; C = air scattering, fluorescence, and instrument-related background area. Total peak area A including background directly below the narrow reflections of the Si phase. The background area C was determined using the XRD diagrams of the Si reference standard NIST 640 (Si standard = 100% crystallinity). Area B corresponds to an inserted background profile and the constant background C. Calculation (HighScore Plus software). Si standard (Standard Reference Material 640d for X-Ray Metrology, David R.Black, Donald Windover, Albert Henins, David Gil, James Filliben, and James P. Cline; National Institute of Standards and Technology, Gaithersburg, MD, 20899). In X-ray amorphous powders, there are no sharp interferences in XRPD, but only a few diffuse ones at small diffraction angles. Materials with this type of X-ray diffraction pattern are called X-ray amorphous. Crystalline: A crystal is an anisotropic, homogeneous body that has a three-dimensional periodic arrangement of its building blocks and an XRPD with clearly defined, resolvable reflections.

[0012] The invention also relates to primary cells in which the anode material comprises silicon particles comprising silicon primary particles, agglomerates of silicon primary particles, aggregates of silicon primary particles and / or mixtures thereof, wherein in particular the agglomerates and / or aggregates have a size of 10 nm to 100 pm (micrometers). Preference is given to agglomerates and / or aggregates in the range from 100 nm to 5 micrometers, in particular from 200 nm to 2 micrometers, preferably from 300 nm to 1.5 micrometers and / or from 400 nm to 1 micrometer. At the same time, the silicon primary particles can have a particle size distribution of 1 nm to 15 nm, in particular from 50 to 300 nm or from 100 nm to 300 nm. A primary cell, in particular an electrochemical primary cell, is understood to be a primary battery or primary cell that is intended to be discharged once, whereby this single discharge can also take place in several steps.A single discharge is understood to be the state after current has been drawn until the capacity of the primary cell is completely exhausted or below a certain voltage. A primary cell is thus defined as an electrochemical cell that can be converted once, optionally in several steps, from an initial voltage (Vcharges), at which the cell is considered charged, to a discharge voltage (Vcharges), and this process is irreversible. A primary cell can therefore be used and disposed of and cannot be recharged with electricity to be reused like a secondary cell. A silicon anode according to the invention in a primary cell is therefore consumed or dissolved over its service life due to corrosion by the electrolyte and is in particular not available for recharging.

[0013] Battery separators in an alkaline battery cell are used to separate a negative electrode from a positive electrode when placed in a suitable electrolyte. In addition to separating the electrodes, during cell operation, when normal chemical reactions occur, the separator exhibits a relatively low resistance to electrolyte ion transfer, but a considerably high resistance to electrode ion transfer.

[0014] The separator is formed, for example, by applying an improved coating. The separator is typically a flexible, fibrous, and porous substrate that is resistant to strong alkalis and oxidation. The separator can be a composite and can preferably be based on at least one polymer, such as polyethylene, polypropylene, polyacrylate, linoleum, cellulose, and / or microcellulose.

[0015] The coating composition of the separator comprises, for example, a mixture of a polymeric binder, a hydrolyzable polymeric ester, and inert fillers. A suitable polymeric binder is ethylene-propylene rubber. A suitable hydrolyzable ester is a film-forming polyacrylate. The inert fillers can be, among others, an alkali-insoluble pigment material, including kaolin, metal oxides, and / or titanates. When the separator produced or coated in this way is immersed in the alkaline electrolyte, the hydrolyzable polymeric ester reacts chemically with the electrolyte to form a polymeric salt and an alcohol. The alcohol dissolves. The salt formed during hydrolysis and retained in the coating expands due to further penetration of the electrolyte.These expansion forces of the binder's polymer chains lead to further expansion and an increase in the intermolecular distance. The greater spacing of the polymer binder's intermolecular chains results in an overall increase in the porosity of the film coating. The resulting increase in the coating's porosity allows for faster diffusion of electrolyte ions through the separator while still providing a significant barrier to the large ions emitted by the electrodes.

[0016] Furthermore, it is preferred that the anode material comprises silicon particles and conductivity promoters; in particular, the conductivity promoter comprises carbon-containing particles or a carbon-containing paste, such as electrically conductive organic polymers. A particularly preferred anode material of the anode comprises 10 to 100.00 wt. %, in particular 5 to 90 wt. %, preferably 10 to 95 wt. % silicon particles and a carbon-containing conductivity promoter, in particular 5 to 90 wt. %, and optionally further additives to 100 wt. % of the anode material. The conductivity promoter preferably comprises carbon-containing particles, in particular with a particle size of 20 to 100 nm, in particular 25 to 80 nm. The anode material comprises silicon particles and conductivity promoters in order to reduce the internal resistance of the electrodes, in particular to less than 10 ohm / cm.Also preferred is an anode material of the anode comprising 20 to 75 wt.%, preferably 20 to 60 wt.%, of silicon particles and a carbon-containing conductivity promoter, in particular 25 to 80 wt.%, preferably 40 to 80.

[0017] Wt.%, and optionally further additives to 100 wt.% of the anode material. The conductivity promoter preferably comprises carbon-containing particles, in particular a particle size of 20 to 100 nm, in particular 25 to 80 nm. A particularly preferred anode material of the anode comprises 45 to 55 wt.% silicon particles and 55 to 45 wt.% a carbon-containing conductivity promoter, the total composition of the anode material being 100 wt.%, in particular of the anode material without electrolyte, i.e. dry anode material. The anode material can be used in a primary cell with an air cathode or together with a cathode in a hermetically sealed battery housing.

[0018] According to the invention, an anode material of the anode comprising silicon particles with an iron, zinc, potassium, aluminum, carbon, calcium, optionally titanium, optionally copper content of greater than or equal to 0.01 mg / kg is also particularly preferred. The invention likewise provides an anode material comprising silicon particles having an iron and aluminum content of greater than or equal to 0.02 mg / kg. The invention further provides an anode material comprising silicon particles and optionally carbon and silicon-containing particles and optionally particles of at least one allotropic carbon modification, wherein the silicon particles, in particular the anode material, in particular a silicon anode, have an iron content of greater than or equal to 0.02 mg / kg.Particles containing carbon and silicon and having at least one allotropic carbon modification may include carbon black, spherical nanoparticles comprising graphite, graphite, and polycyclic carbon. These particles preferably have a diameter of greater than or equal to 10 nm, in particular from 10 nm to 300 nm. The surface area of ​​these particles is preferably at least 1 m. 2 / g up to 600 m 2 / g. Preferably, the carbon- and silicon-containing particles comprise silicon carbide, and / or the particles of at least one allotropic carbon modification comprise diamond, polycyclic carbon modifications, graphite, fullerene, and graphene. Diamond can originate from a wire-sawing recycling process.

[0019] The invention further relates to an anode material for the anode comprising silicon particles with an iron content of greater than or equal to 0.02 mg / kg, preferably greater than or equal to 0.05 mg / kg to less than or equal to 2500 mg / kg, preferably greater than or equal to 5 mg / kg to less than or equal to 250 mg / kg. Particularly preferably, the iron content originates at least partially from abrasion of steel products, such as steel-containing saws. The advantage of the iron content in the silicon anode and / or the silicon particles is that iron does not corrode at an alkaline pH, and corrosion is very effectively prevented, in particular, at a pH of 9.2 to 9.5. For steel, the protective effect is most effective at a pH of 9.8. In this way, the iron content in the silicon anodes and / or silicon particles can efficiently reduce corrosion in alkaline electrolytes, particularly in aqueous KOH. Consequently, the anode efficiency can be increased.Anode efficiency depends on the oxidation of the silicon on the surface and can be improved, among other things, by increasing the iron content. The focus for increasing anode efficiency, discharge performance, and thus the service life of the silicon anodes and / or silicon particles is corrosion inhibition.

[0020] According to a further embodiment, the invention relates to a primary cell and / or anode material comprising silicon particles and conductivity promoters for use in an electrochemical primary cell. An electrochemical primary cell is understood to be a primary battery or primary cell that is intended to be used once and disposed of, and not to be charged with electricity and reused like a secondary cell. A silicon anode according to the invention in a primary cell is thus consumed or dissolved over its service life due to corrosion by the electrolyte and, in particular, is not available for recharging.

[0021] According to two alternative particularly preferred embodiments, the cathode of the primary cell comprises a) manganese dioxide as cathode material, or b) the cathode of the primary cell is an air cathode and the cathode comprises manganese oxide, in particular a manganese oxide which is not manganese dioxide and optionally manganese dioxide, platinum, platinum-based, nickel-cobalt cyanide or silver as catalyst in the cathode material.

[0022] Nickel-cobalt cyanides are exemplary of the class of non-noble metal catalysts with excellent electroactivity for the oxygen reduction reaction in neutral electrolytes. The preparation of the Ni / Co-doped CN hollow nanotube composite catalysts (CN, Co / CN, Ni / CN, and Ni-Co / CN) is achieved by simple pyrolysis of the Ni / Co salt-dicyandiamide-glucose mixture. A corresponding silicon-air battery was assembled in a neutral medium using the prepared sample as the catalyst for the air electrode and demonstrated excellent discharge performance and stability.

[0023] The cathode preferably comprises manganese dioxide as a material, i.e., as a cathode material or as a catalyst in the cathode material to accelerate the solubility of oxygen. A preferred cathode material for a cathode in a primary cell with an air cathode preferably comprises manganese oxide, and optionally manganese oxide, as well as silver as a catalyst. A particularly preferred cathode material, in particular for a primary cell with an air cathode, has a hydrophobic cathode whose cathode material comprises a mixture of manganese (di)oxide, i.e., manganese oxide and / or manganese dioxide, preferably with an average particle size of less than or equal to 10 μm (micrometers), in particular electrolytic gamma-manganese dioxide, a conductivity promoter, and a polymeric halogenated hydrocarbon, in particular a polymeric fluorinated hydrocarbon, in particular polytetrafluoroethylene. The mixture can be pressed into plates and dried.In this case, a microporous, hydrophobic film, for example made of a polymeric fluorinated hydrocarbon, is preferably applied to the cathode side exposed to air in the primary cell.

[0024] A particularly preferred cathode material for the cathode, especially for a cathode in a hermetically sealed battery housing, comprises 75 to 85 wt.% manganese dioxide and 15 to 25 wt.% carbon-containing conductivity enhancer, with the total composition of the cathode material being 100 wt.%. The cathode material preferably does not yet comprise an electrolyte or is dry cathode material.

[0025] The carbon-containing conductivity enhancer preferably comprises carbon-containing particles, particularly preferably graphene-containing particles. The carbon particles preferably have a particle size distribution in the range from 0.1 nm to 5 micrometers, preferably from 5 nm to 5 micrometers. It is further preferred if the carbon particles have a particle size in the range from 5 nm to 300 nm, in particular from 10 nm to 150 nm, particularly preferably from 20 to 100 nm, and optionally are present as agglomerates with a size of 100 nm to 3 micrometers, preferably a size of 300 nm to 2 micrometers.

[0026] According to a preferred embodiment, the silicon, in particular the silicon particles, preferably the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are selected from elements of the 13th main group, in particular comprising boron, indium, aluminum and / or gallium, and from elements of the 15th main group, in particular comprising phosphorus, arsenic and / or antimony as well as elements of the iron group, particularly preferably boron, aluminum, phosphorus and / or iron. The elements of the 13th main group (new nomenclature: Group 13 of the Periodic Table) are electron acceptors of the new nomenclature. Elements of the 15th main group (new nomenclature: Group 15 of the Periodic Table) are used as electron donors. According to one embodiment, the silicon, in particular the silicon particles of the anode material, comprises dopants, wherein the dopants comprise greater than or equal to 1 element of the 15th main group per 10 6Silicon atoms and / or greater than or equal to 1 element of the 13th main group per 10 6 Silicon atoms are present, in particular greater than or equal to 1 element of the 15th main group per 10 4 Silicon atoms and / or greater than or equal to 1 element of the 13th main group per 10 4 Silicon atoms, determined using ICP-MS analysis (Inductive Plasma Discharge Mass Spectroscopy, which is described in detail on Wikipedia: https: / / de.wikipedia.org / wiki / Massenspektrometrie_mit_induktiv_gekoppeltem_Plasma). Alternatively, the analysis can also be performed using GD-MS (GDMS / GD-MS glow discharge mass spectroscopy with a Secondary Electron Multiplier (SEM) and / or Faraday detector, as described at: https: / / assets.thermofisher.com / TFS-Assets / CMD / brochures / BR-30066-GD-MS-ELEMENT-GD-PLUS-BR30066-EN.pdf). The Faraday detector is preferably used for measuring trace concentrations in the % range.

[0027] According to an alternative, preferred embodiment, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 2 Atoms (approx. 100 ppm by weight, depending on the atomic weight of the dopant) of the 15th main group to 10 6 silicon atoms and / or greater than or equal to 10 2 Atoms of the 13th main group to 10 6 silicon atoms are present.

[0028] According to further preferred alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 2 10 2 Atoms of the 15th main group to 10 6 Silicon atoms greater than or equal to 2 10 2 Atoms of the 13th main group to 10 6Silicon atoms are present. The above contents of dopants in the silicon of the anode material can be inhomogeneously distributed in the silicon, as well as the contents can be present integrally over the total amount of silicon in the anode material on average. To determine the above contents, a test quantity of 1 g of the test quantity is measured by GD-MS or ICPMS, whereby certain deviations can be determined between the two methods; preferably, an average value is determined. According to further preferred, alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 5 Atoms of the 15th main group to 10 6 silicon atoms and / or greater than or equal to 10 5 Atoms of the 13th main group to 10 6 silicon atoms.

[0029] According to further preferred, alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 19 Atoms of the 15th main group to 10 22 silicon atoms and / or greater than or equal to 10 19 Atoms of the 13th main group to 10 22 Silicon atoms. The silicon particles may comprise, at the atomic level, an alloy of silicon with at least one element of main group 13 or 15, wherein the at least one element of main group 13 or 15 most preferably contains at least 10 21 atoms / cm 3and is selected from at least one electron donor and electron acceptor. The alloy of silicon at the atomic level with at least one element of main group 13 or 15 is present as an amorphous or crystalline phase. The silicon particles particularly preferably have a boron content of 10 ppm by weight to 2.5 wt.% in relation to the total content of 100 wt.% of the silicon particle, preferred is a content of 10 ppm by weight to 1.8, particularly preferred is 1.8 wt.% plus / minus 0.2 wt. Analogously, the silicon of the anode can be part of a silicon-coated electrode material (silicon foil), wherein the silicon has a boron content of 10 ppm by weight to 1.8 wt.% in relation to the total content of 100 wt.% of the anode silicon.

[0030] The invention relates to a primary cell comprising silicon particles having a boron content of 10 wt. ppm to 1.8 wt.%.

[0031] To produce an anode or cathode, a conductivity enhancer, silicon particles for the anode, manganese dioxide for the cathode, and optionally a binder, such as a polymeric fluorinated hydrocarbon, are mixed and optionally dried. A homogeneous particle size of less than or equal to 10 micrometers to 5 nm is preferably achieved, and the mixture is pressed into an anode (plate) or cathode (plate).

[0032] According to a further alternative, the primary cell has an air inlet at the air cathode, which can be a gas-permeable membrane. A membrane made of an inert polymer, preferably polyfluoropolyethylene, polyfluoropolypropylene, or copolymers thereof, is preferred. The air cathode is generally constructed as a sandwich structure comprising a gas-permeable membrane, a metallic mesh for conducting electricity, and at least one catalyst, particularly a porous catalyst. The gas-permeable membrane is preferably impermeable to carbon dioxide and permeable to oxygen and optionally nitrogen.

[0033] A preferred proportion of binder in the electrode material is in the range of greater than 20 to less than 40 wt.%, preferably 22 wt.% to 38 wt.%, in the total composition of the cathode material or the anode material.

[0034] In further alternatives, the cathode material can further comprise at least one additive selected from Bi2O3, PbO2, SnO2, Bi2O3*3ZrO3, and K2Cr2O?, wherein the additive is present in the cathode material at 0.1 to 10 wt.%, and manganese dioxide, the conductivity enhancer, and optionally a binder are present at 100 wt.% in the total composition of the cathode material. If the cathode is an air cathode, the cathode material can optionally additionally comprise silver as a catalyst, in particular nanoparticulate silver articles. It is further particularly preferred if the anode, in particular the anode material, especially in the charged state of the primary cell, does not comprise lithium, preferably does not contain any lithium ions, in the concentration range of greater than or equal to 1000 wt. ppm to greater than or equal to 10 wt. ppm. The anode material particularly preferably contains less than 1 wt. ppm lithium atoms. Preferably, the anode material has less than 10 21 Lithium atoms / cm3 Silicon particles. Furthermore, it is preferred if the concentration of lithium, in particular lithium ions, in the electrolyte is less than or equal to 1000 ppm by weight, in particular less than or equal to 100 ppm by weight, preferably less than or equal to 10 ppm by weight.

[0035] According to a further embodiment, it is preferred if the primary particles of the silicon particles form agglomerates and / or aggregates or mixtures thereof and can preferably be arranged in a porous silicon network. In particular, the agglomerates, aggregates, or mixtures thereof can be mechanically interlocked to form a porous silicon network. In this respect, the anode material can particularly preferably be a porous silicon network composed of primary silicon particles, agglomerates of primary silicon particles, aggregates of primary silicon particles, and / or mixtures thereof.

[0036] It is particularly preferred if the silicon particles, in particular the primary silicon particles, are essentially amorphous (X-ray amorphous), as this ensures uniform dissolution of the silicon particles in the electrolyte. With essentially crystalline silicon, dissolution in the electrolyte would occur anisotropically. Amorphous silicon is dissolved isotropically, so that amorphous silicon can deliver a higher energy density. For example, in alkaline etchants, the etching rate for the (111) directions of a silicon crystal is approximately two orders of magnitude lower than that of any other direction. The (100)-oriented surfaces of the silicon crystal are etched one and a half times faster than the (1 10)-oriented surfaces. Doped, amorphous silicon particles can also be used. If the doping of p-type silicon particles is greater than > 10 19 per cm 3, the etching rate is reduced, since the higher the doping rate, the lower the etching rate. Therefore, the power density can also be adjusted via the etching rate through the doping in amorphous silicon particles.

[0037] Amorphous silicon primary particles are silicon primary particles, usually in powder or solid form, which (silicon primary particles) are X-ray amorphous and can optionally be embedded in a particle-dispersed form in an auxiliary matrix, e.g., carbon black. X-ray amorphous means that the X-ray signal, corresponding to the main peaks: 28.5° (111), 47.4° (220), 56.0° (311), 69.4° (400), reaches a maximum of less than 10% of the signal amplitudes based on the so-called "fcc structure" of the silicon (JCPDS card: 00-027-1402).

[0038] The anode material according to the invention does not comprise silicides. Silicides are understood to be intermetallic compounds with a stoichiometric proportion of at least one second metal. Silicides comprise a homogeneous chemical compound of two or more metals with lattice structures that differ from those of the constituent metals. Furthermore, the anode material does not comprise a classic alloy of at least two elements that together exhibit the typical metal characteristic of a crystalline structure with a metal bond, since the silicon particles are preferably essentially amorphous (X-ray amorphous).

[0039] The electrochemical primary cell according to the invention is not a lithium-ion battery. Furthermore, the anode material does not comprise a lithium intercalation compound. According to the invention, the cathode material does not comprise a lithium metal oxide. Likewise, the primary cell does not comprise any lithium salts.

[0040] The silicon particles may comprise, at the atomic level, an alloy of silicon with at least one element of the 13th or 15th main group, wherein the at least one element of the 13th or 15th main group has a concentration of greater than or equal to 10 21 atoms / cm 3 selected from at least one electron donor and electron acceptor. The alloy of silicon at the atomic level with at least one element from main group 13 or 15 exists as an amorphous phase.

[0041] According to one embodiment, the silicon primary particles essentially have a particle size of 5 to 500 nm, in particular of 5 to 20 nm, preferably of 5 to 15 nm, or in equally preferred alternatives, the silicon primary particles have particle sizes of 20 to 200 nm or of 70 to 350 nm, in particular of 100 to 300 nm.

[0042] Furthermore, it is preferred if the silicon primary particles are in the form of agglomerates and / or aggregates of the primary particles, wherein the agglomerates and / or aggregates have a particle size of 100 nm to 3 pm, in particular of 100 nm to 2000 nm, preferably of 150 to 1000 nm or of 400 to 1000 nm. The aforementioned arrangements can also be regarded as nanowires or nanonetworks. In a further alternative, the silicon particles are essentially in the form of agglomerates of silicon primary particles and / or aggregates of silicon primary particles or mixtures thereof, wherein the agglomerates and / or aggregates have a size of 100 to 3000 nm, in particular of 100 to 2500 nm, preferably of 100 nm to 1500 nm, more preferably 150 to 1000 nm, 400 to 1000 nm or 200 to 2000 nm.

[0043] The silicon primary particles according to the invention preferably have a surface area of ​​10 to 500 m 2 / g, especially from 10 - 100 m 2 / g, preferably with a primary particle size of about 10 nm on average with plus / minus 9 nm. Furthermore, the surface area of ​​the agglomerates and / or aggregates is preferably from 10 to 80 m 2 / G.

[0044] The cathode and / or the anode preferably have a porosity determined by density measurement. The porosity of the cathode and / or the anode is preferably from 8 to 78 vol.% relative to the total volume of the cathode (100 vol.%), preferably from 14 to 58 vol.%, particularly preferably from 25 to 27 vol.%. The porosity is the space in the anode and / or the cathode available for the fluid electrolyte. The porosity is expressed as a percentage volume of the total geometric volume of the cathode or the anode. Thus, the spaces formed by the porosity can be partially or completely filled with electrolyte.

[0045] Porosity of the anode (volume density of anode material): silicon density between 0.1 and 2.3 g / cm 3 .

[0046] According to equally preferred alternatives, the weight ratio of manganese dioxide in the cathode material to the electrolyte can be from 2.2 to 2.9. Alternatively or simultaneously, the weight ratio of the silicon particles in the anode material to the electrolyte can be from 0.6 to 1.7.

[0047] The separator can comprise filter paper, a polymeric membrane, a metallic membrane, a ceramic membrane, or a membrane made of a hybrid material. A polymeric membrane can preferably comprise polyethylene, polypropylene, or an inert polymer or copolymer. Microporous polypropylene films are preferred, in particular with a thickness of 0.028 mm to 0.1 mm, preferably 0.038 mm to 0.75 mm, with the porosity preferably being 45 vol% to 90 vol%, in particular 50 to 80 vol%, preferably 55 to 70 vol%, based on the total volume of the membrane.

[0048] According to a further preferred embodiment, the electrochemical primary cell is a basic battery or an alkaline battery.Preferably, the electrolyte of the electrochemical primary cell is selected from: a) an aqueous fluid composition containing alkaline salts, or a basic fluid composition comprising Na2CO3, or b) an aqueous or non-aqueous fluid composition containing fluoride anions (F), or c) an aqueous composition containing fluoride anions (F-) with a content of undissolved fluoride or containing an intercalation compound containing fluorides, in particular the composition comprises at least one salt selected from MnF2, NH4F, KF, where MnF2 is a solid with a solubility in water, or d) a non-aqueous fluoride anion-containing composition comprising at least one ionic liquid, such as ethyl methyl imidazolium cations and fluoride anions comprising HF, ethyl methyl imidazolium tetrafluoroborate, optionally in the presence of further salts of fluoride anions, such as NH4F.

[0049] In further advantageous embodiments, the fluid electrolyte can also comprise anhydrous, protic solvents. In further advantageous embodiments, the fluid aqueous electrolyte can also comprise buffers, such as carbonic acid silicate buffers (pH 5.0 to 6.2; weakly acidic) or ammonium chlorides (pH = 5.5). Furthermore, in preferred embodiments, the fluid electrolyte can also comprise alkali fluorides, such as KF, mixed with ammonium fluoride (KF, pH = 8-9, NH4F, pH = 6). In alternative embodiments, it can be preferred for the electrolyte to comprise inorganic salts and, in particular, to have a pH of 2 to 9.5, in particular of 3 to 7, preferably of 2 to 6, further preferably of 3 to 6. Particularly preferably, a pH of 6 with plus / minus 0.5. Optionally, the electrolyte can also contain a buffer and / or a buffer system. A carbonic acid silicate buffer makes the cell robust against CO2 absorption.

[0050] In particularly preferred embodiments, the electrolyte comprises organic or inorganic salts of halide anions, in particular fluorides or chlorides. Furthermore, the electrolyte preferably comprises an aqueous composition comprising hydroxide anions, carbonate anions, such as in Na2CC>3, or halide anions, in particular fluoride anions and / or chloride anions. An aqueous hydroxide solution or an aqueous solution or suspension containing fluoride anions is preferred.

[0051] Furthermore, according to further embodiments, it is preferred if the aqueous electrolyte comprises at least one salt selected from ammonium salts of halides, ammonium salts of carbonates, ammonium hydroxide, alkali halides, alkaline earth halides, alkali carbonate, alkaline earth carbonate, rare earth halides, rare earth fluorides, particularly preferably manganese salts such as manganese difluoride and / or manganese dichloride, ammonium salts such as ammonium halides, in particular ammonium fluoride and / or ammonium chloride, alkali hydroxides such as potassium hydroxide and / or sodium hydroxide, alkali halides, preferably alkali fluorides such as sodium fluoride and / or potassium fluoride, organic carboxylic acids and / or their salts, such as citric acid and / or salts of carboxylic acids. Furthermore, the electrolyte can comprise salts of rare earth metals, such as fluorides of rare earth metals. Furthermore, the electrolyte may comprise carbonates of alkali and / or alkaline earth metals.In a particularly preferred alternative, the electrolyte comprises salts selected from manganese difluoride, manganese dichloride and / or ammonium fluoride and optionally potassium fluoride.

[0052] It has proven advantageous for the electrolyte to contain a wetting agent to improve wetting properties. Preferred wetting agents include surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, organic solvents such as alcohol, ketone, ether, polyether, such as polyethylene oxide and / or polypropylene oxide. The wetting agent in the electrolyte can preferably be present at a content of 1 to 1000 ppm by weight based on the total composition of the electrolyte of 100% by weight.

[0053] A preferred composition of an aqueous electrolyte comprises 2 to 50 wt.% of at least one salt, in particular an inorganic salt, in particular 18 to 22 wt.% of at least one inorganic salt or a mixture of at least two inorganic salts and 50 to 98 wt.% water, in particular 78 to 82 wt.% water, and optionally additives, to the total composition of 100 wt.% of the aqueous electrolyte. Preferably, a mixture of two inorganic salts can be present in the electrolyte, comprising 2 to 15 wt.% of one salt and 15 to 25 wt.% of another salt in the total composition of 100 wt.% of the aqueous electrolyte.

[0054] The invention also relates to an electrochemical primary cell comprising an aqueous, alkaline electrolyte composition containing 2.0 to 99.0 wt.% water, a content of 0.001 to 40 wt.%, in particular 10 to 40 wt.%, of alkali hydroxide based on the total composition of 100 wt.%. Optionally, the electrolyte compositions can comprise a corrosion inhibitor for the silicon anode, in particular with 0.001 to 20 wt.% based on the total composition. Particularly preferably, an alkaline electrolyte composition contains 2 to 5 mol / liter of alkali hydroxide in the total composition, particularly preferably 4 mol / liter with plus / minus 0.5 mol / liter of alkali hydroxide.

[0055] The alkali metal hydroxide can be selected from NaOH and KOH, and optionally other alkaline soluble salts, such as alkaline earth metal hydroxides, basic metal oxides, or organic bases. The electrolyte composition preferably comprises an alkali metal hydroxide selected from KOH and NaOH. Furthermore, the water is preferably distilled water.

[0056] A particularly preferred cathode material comprises 70 to 95 wt.% manganese dioxide, especially battery grade and preferably with a particle size of less than or equal to 10 micrometers, and a carbon-containing conductivity promoter, especially 5 to 30 wt.% conductivity promoter, and optionally further additives, based on 100 wt.% of the cathode material. The conductivity promoter is preferably a carbon-containing particle, a mixture thereof, or a carbon-containing paste.

[0057] The carbon-containing conductivity promoter particularly preferably comprises i) carbon-containing particles comprising carbon black, conductive carbon black, electrochemically produced carbon black, electrical black, activated carbon, graphite, graphene and / or a mixture thereof, and / or ii) a carbon-containing paste which may comprise electrically conductive polymers which may comprise heteroatoms N, O and / or S, such as polyaniline or graphene.

[0058] It has been found that carbon black is more effective as a conductivity enhancer than graphite powder. The sufficient proportion of carbon black in the anode material is preferably in the range of 50 to 90 wt.% of the total composition. With a two-cell battery with a diameter of 16 cm 2 active electrode area could already provide sufficient power to operate a small fan.

[0059] In a particular variant of the electrochemical primary cell, a pressure of 0.01 to 10 MPa, preferably 0.5 to 5.0 MPa, is preferably applied to the cathode and / or anode in order to compact the powder material and reduce the internal resistance of the electrodes to less than 10 ohm / cm. The invention also relates to a multi-cell battery, wherein the battery comprises at least two to 15,000, in particular 3 to 500, preferably 4 to 100, interconnected primary cells. Of the two to 15,000 interconnected primary cells, 4 to 100 are preferably connected in series, and the others are connected in parallel. The battery is defined according to DIN standard 40729.

[0060] The invention also relates to the use of silicon as anode material in the form of silicon particles, in particular in primary cells, which are present as silicon primary particles with a particle size between 1 nm and 3000 nm and, in particular, the silicon primary particles form agglomerates and / or aggregates or mixtures thereof, wherein the silicon particles, in particular the silicon primary particles, are optionally substantially amorphous and the anode material in the charged state does not comprise any lithium. Preferably, the anode material in the charged state does not comprise any lithium ions in the concentration range of greater than or equal to 10,000 ppm by weight, preferably greater than or equal to 1,000 ppm by weight, particularly preferably greater than or equal to 100 ppm by weight, preferably greater than or equal to 10 20 Lithium atoms / cm 3 .

[0061] Furthermore, the electrolyte preferably does not contain any lithium ions with a concentration in the electrolyte in the range above 10,000 ppm by weight, in particular 1,000 ppm by weight, preferably 100 ppm by weight.

[0062] Implementation examples:

[0063] The following tables show the samples of silicon particles and the conductivity enhancer used.

[0064] Table 1 : X-ray amorphous silicon particles Table 2: Conductivity enhancers containing carbon-containing particles

[0065] Electrode pastes were produced using the silicon particles and the carbon particles, which can alternatively be pressed with a binder.

[0066] Battery tests

[0067] The construction of all tested primary cells 1 was carried out according to Figure 1: contact electrodes 2, 3; graphite foil 4, 5; silicone disc 6 with central hole diameter 24 mm (4.5 cm 2 ) for anode material 8, cathode material 9; separator 7 (filter paper), bore 10 in silicone disc 6 for receiving the electrode material.

[0068] Cathode material (e.g., 90% MnO2 + 10% graphite + electrolyte solution) was introduced into the bore 10 of a silicone disk 6 on a graphite foil 5 on the contact electrode 3, and the separator 7 was placed on top. The separator 7 protrudes on one side so that excess electrolyte solution can escape when pressed together. The upper silicone disk 6 is placed on top, and the respective anode material (as anode paste) is filled into the bore, and the graphite foil 4 and contact electrode 2 are placed on top and pressurized with 900 N (equivalent to 20 bar at 4.5 cm 2) are pressed together. The force is distributed across the electrode pastes and silicone discs.

[0069] With a primary cell according to the above primary cell design, a voltage U can be measured at the electrodes. During performance tests, the current load (I) is increased every 30 seconds.

[0070] Example 1 :

[0071] The initial voltage of a test cell with silicon and carbon particles as anode material according to Tables 1 and 2, with silicon particles B containing 80 wt.% and 20 wt.% graphite, and a cathode consisting of 90 mol% MnO2 and 10 mol% graphite, was around 400 mV with an aqueous 20 mol% ammonium chloride solution (NH4Cl) as the electrolyte. Replacing the silicon anode material with battery-grade zinc powder results in a powerful battery with an initial voltage of around 1200 mV and several tens of mW / cm 2Power density with otherwise identical experimental setup. Measurements of the internal resistance of the anode and thus of the anode material with silicon particles B 80 wt% and 20 wt% showed high values ​​in the range of 4 kiloohms per cm 2 . The current load of the anode material with silicon particles B 20 wt.% and 80 wt.% graphite was 100 |jA / cm 2 at a power density of max. approx. 0.01 mW / cm 2 .

[0072] The anode material was measured wet with aqueous electrolyte.

[0073] Example 2:

[0074] A measurement setup of a primary cell according to the invention, initially thoroughly mixed with 20 wt.% silicon particles B and 80 wt.% graphite, and then mixed with an aqueous electrolyte solution, shows a voltage U that increased from approximately 150 mV to approximately 400 mV within 75 minutes. In the subsequent stress test [U(l) measurement], power densities of up to 0.185 mW / cm2 During the recovery phase, U rose back to the initial value within 10 minutes and then slowly decreased again after about 90 minutes (approximately 250 mV).

[0075] Example 2 suggests that a further performance improvement can be achieved through more homogeneous mixing and with smaller silicon particles and smaller conductivity enhancer particles. A coordinated, preferably bimodal, particle size distribution is preferred.

[0076] Improvement of cell structure:

[0077] The test batteries were assembled using a vise specially designed for battery testing. First, the anode and cathode materials were thoroughly ground in a mortar while dry to ensure good contact between the active material and the conductivity promoter. Then, by adding an appropriate amount of electrolyte fluid and a wetting or wetting agent, they were ground into a spreadable paste in a mortar. These pastes were then spread into the respective electrode compartments. A wetted piece of filter paper was used as a separator and regulator for the electrolyte fluid.The paste in the anode compartment was smoothed to create a slight curve, ensuring that the subsequent contact pressure applied with the assembly vise primarily compressed the electrode pastes, ensuring good contact between the active material and the conductivity promoter. The presence of sufficient conductivity in the electrode pastes was demonstrated by varying the contact pressure during several power measurements. No significant change in power was observed in any of these cases.

[0078] For all test batteries, voltage and power gradually decreased during the stress tests. During longer recovery phases without stress, the voltage increased again, but did not quite reach the value before the start of the previous stress phase. This can be attributed to changes in the internal resistance of the electrodes, which is influenced by electrochemical processes at the particle surfaces. U(l) curves were recorded for the test batteries. Since the voltage decreased accordingly during each stress level, especially at higher stress levels, the measurement frequency was increased (measurement intervals of 30 seconds), and all necessary measurements were recorded using this setting.

[0079] For the load measurements, depending on the cell's open-circuit voltage, a diode, two diodes connected in series, a single Schottky diode, or a diode connected in series with a Schottky diode were used as the "load." The load curves obtained in this way over time primarily allow conclusions to be drawn about the load capacity or its decline over longer periods. However, these load curves are only comparable to the U(l) curves to a very limited extent. For a more in-depth understanding, please refer to the electrical engineering literature or the recommendations of semiconductor manufacturers regarding the use of diodes in circuit technology.

[0080] For a selected demo battery, the Si density in the anode paste consisting of 30 wt% silicon particles D and 70 wt% Vulcan-XC72R was determined to be 0.104 g / cm 3Based on this value, the theoretical capacity of the demo battery was calculated. It was approximately 1000 As. In contrast, the power consumption during the load measurements was 20 As, which is 2% of the theoretical capacity. The battery's actual capacity limit had not been reached even after two weeks of alternating operation.

[0081] Specific resistance and conductivity measurements on Si-C anode materials and MnC>2-C cathode materials

[0082] For the measurement of the specific electrical resistance, the samples were placed in a plastic ring between two stainless steel pistons (area 5.0 cm 2), each of which had a copper sheet underneath or on top of it for current supply and voltage tap, were pressed together with a defined force. For each force level, the current, voltage, and distance between the copper sheets were measured. The same values ​​were also measured with the sample-free test setup, and the corresponding ohmic resistances and sheet spacing were subtracted from the corresponding values ​​measured with inserted samples.

[0083] The results of the conductivity measurements are graphically presented in the diagrams shown below in Figures 2, 3 and 4.

[0084] Where: yj: mass fraction of component i; R_sp: specific resistance [Q*cm],

[0085] A specific resistance of 1 Q*cm corresponds to a layer thickness of 0.2 cm in the test batteries and a current density of 10 mA / cm 2a voltage drop of 2 mV in the worst case caused by the ohmic resistance of the electrode paste in question.

[0086] Figures 2, 3 and 4 (Fig. 2: silicon particles B [wt.%], Fig. 3: silicon particles D [wt.%], Fig. 4: Mn2O [wt.%]) show that for both the anode material and the cathode material, a significantly higher conductivity is achieved by using Vulcan XC72R carbon black compared to graphite as an alternative conductivity enhancer at the same mass fraction.

[0087] The conductivities depend on the contact pressure in both cases. The resistivity values ​​given for 0.9 MPa were measured during the measurement phase with a gradual increase in pressure. When the pressure is reduced, the resistivity curve, as well as the layer thickness curve, shows a pronounced hysteresis. A typical example is shown in Figure 5 and illustrates the influence of both the contact pressure and the history of the contact pressure on the internal resistance of the test cell. Figure 5 shows the hysteresis of the internal resistance (measurement of the specific conductivity via pressure, p [MPa] in relation to the layer thickness [mm]) using the example of the Si-C anode paste consisting of 50 wt.% silicon particles A and 50 wt.% Vulcan-XC72R as a function of the contact pressure on the electrodes.

[0088] The conductivities of pure Si powders are very low at room temperature. However, measurements at higher voltages show a different behavior, which is due on the one hand to unavoidable oxide layers on the silicon particle surface and on the other hand to the purity of the silicon.

[0089] Table 3: Si particle conductivities and pressure

[0090] Preliminary tests to characterize the Example 3 test cell with silicon particles B and modified NH4CI solution

[0091] First, the resistance of silicon material B to various aqueous electrolyte solutions was tested in order to subsequently select the additive(s). The tests show that silicon particles B are resistant to water and to concentrated solutions of NH4Cl, NaCl, or citric acid (no gas evolution detectable), limited resistance to dilute solutions of Na2CO3 (gas evolution detectable; sample not fully reacted after a few days), and unstable to concentrated solutions of KOH or Na2CO3 (strong or significant gas evolution; sample dissolves completely within a few minutes or several days). A mixture of 90 wt.% MnO2 and 10 wt.% graphite powder was used as the cathode material. Both with the initially used MnO2 (pa) as well as with the subsequently used MnO2 (precipitated, activated) and MnO2 (battery grade), good performance was achieved with zinc-based comparison cells, so none of these MnO2 grades can be considered as the cause of the low performance. The source of the HH-P type MnO2 used is the Tosoh Hyuga Corporation, JP.

[0092] Due to the expectation that improved performance could be achieved with the help of alkaline electrolytes, experiments were carried out with NH4CI solutions containing Na2CO3.

[0093] Example 3 describes the experimental cell with silicon particles B and NH4CI solution modified with Na2CO3 additives (electrolyte).

[0094] Figure 6 shows the U(l) and P / A(l) characteristics of the test cell (Ref. 160118; anode material: 20 wt.% silicon particles B + graphite, electrolyte: 18 wt.% NH4Cl and 2 wt.% Na2CO3 in H2O, cathode material: 90 wt.% MnO2, precipitated, active + graphite; y-axis: U [mV] or P / A [mW / cm 2 ], x-axis: l / A [mA / cm 2 ] Definition: mV = millivolts = 10 -3 Volt; mW = milliwatt = 10 -3 Watt; mA = milliampere = 10 -3 Amp).

[0095] With this weakly alkalized electrolyte, the performance could be significantly improved, which is mainly due to a correspondingly higher cell voltage (U0 = approx. 700 mV).

[0096] Example 4 describes the test cell with silicon particles B and NH4CI solution modified with Na2CO3 additives (electrolyte), in which a more alkalized electrolyte (15 wt.% NH4CI + 5 wt.% Na2CO3) was used: open circuit potential, cell voltage with U0 < 500 mV and the specific cell power in mW / cm2 decreased significantly.

[0097] Example 5 describes the test cell from Example 2 where the electrode material graphite was replaced by the alternative electrode material carbon black (Vulca-XC72R).

[0098] Anode material: 30 wt.% silicon particles D mixed with 70 wt.% Vulcan-XC72R carbon black. This primary cell was activated with 25 wt.% NH4Cl in H2O as electrolyte and exhibited an initial voltage U0 of approximately 1 V.

[0099] Example 6 describes a test cell analogous to Example 3, in which the graphite electrode material was replaced with the alternative electrode material carbon black (Vulca-XC72R), and an NH4Cl solution modified with Na2CO3 additives was used (electrolyte). With this more alkalized electrolyte (15 wt% NH4Cl + 5 wt% Na2CO3), an open-circuit potential U0 of approximately 650 mV was achieved at comparatively reduced current and power densities.

[0100] Fluoride-containing electrolytes were also tested in the silicon particle primary cell. Example 7 below describes a test cell with a fluoride-containing aqueous electrolyte solution.

[0101] To prepare concentrated aqueous fluoride solutions, the salts KF and NH4F were selected due to their solubility in water. NH4F was used in the subsequent experiments. The aqueous KF solutions have a pH of approximately 8 to 9, such as the solution measured in Example 6, while the pH of an NH4F solution is approximately 6. To evaluate the extent of possible corrosion processes, a concentrated NH4F solution was used first. The electrolyte reacts with the Si particles with noticeable gas evolution. Instead, a modified electrolyte system was tested that contains only a slightly soluble fluoride in predominantly solid form, allowing consumed fluoride to be replaced by dissolving a corresponding amount of solid fluoride. MnF2 (solubility in H2O approx. 10 g / L) was initially chosen as a suitable fluoride. If a high concentration of dissolved MnCl is also present, the Mn 2+The concentration of F varies only slightly with the amount of F consumed, so that it is assumed that the F concentration also remains approximately constant due to the MnF2 solubility product. The prepared electrolyte, referred to below as MnF2 electrolyte, essentially contained (dissolved MnF2 being neglected): MnF2 (solid): approx. 0.5 mol / kg; Mn 2+ : approx. 1.9 mol / kg; NH4 + : approx. 2.5 mol / kg; Cb: approx. 6.3 mol / kg

[0102] Thus, the test battery according to Example 7 was assembled with the silicon particles B, which are more resistant to fluorides. According to Figure 7, this battery was able to generate a performance improved by a factor of 10 compared to the previous examples 1 to 6 (y-axis: U [mV] or l / A [mA / cm 2 ]; P / A [mW / cm 2], x-axis: t [min]). The open-circuit potential (initial voltage) U0 was comparatively high at approximately 0.9 V. Figure 7 shows the load diagram of this primary cell (anode material: 30 wt.% silicon particles B + Vulcan-XC72R, electrolyte: MnF2 electrolyte, cathode material: 90 wt.% MnO2, from Tosoh in graphite powder).

[0103] Example 8 comprises a battery cell with the more active silicon particle D: This enabled an open circuit voltage U0 of just over 1 V to be achieved. The cell according to Example 8 showed a similar performance (Figs. 8 and 9) as the otherwise identically constructed battery cell with silicon particles B. Figure 8 shows the measurement curve as a load diagram, with this primary cell having the following composition: Anode material: 30 wt.% silicon particles D + Vulcan-XC72R, Electrolyte: MnF2 electrolyte, Cathode material: 90

[0104] wt.% MnO2, from Tosoh in graphite powder; (y-axis: U [mV] or l / A [mA / cm 2 ]; P / A [mW / cm2 ], x-axis: t [min]), Figure 9 shows further stress diagrams of this primary cell after one day (left) and another 3 days (right) with a recovery phase without stress in between (y-axis: U [mv] or l / A [mA / cm 2 ]; P / A [mW / cm 2 ], x-axis: t [min]). The power of this primary cell is sufficient to rapidly rotate a low-voltage electric motor with a propeller.

[0105] Example 9 comprises a battery system consisting of two series-connected primary cells constructed with the same material as described in Example 8. Their active electrode areas are 16 cm 2 , which is sufficient to provide an average total current of around 20 mA to drive a motor with a fan attached. In contrast to Example 8, the MnF2 electrolyte was mixed with half the amount of 25% NH4CI solution, so that the F concentration in the electrolyte was lower due to the lower Mn 2+concentration can theoretically be somewhat higher than in the electrolyte according to Example 8. Initial currents of approximately 40 mA to 50 mA were measured. The battery volume is only approximately 20 cm 3 , which is barely more than the volume of two AA batteries. After a week of further stress tests, a power density of more than 3 mW / cm 2 measured. Quite surprisingly, this long cell life demonstrates that corrosion of the cell's anode material has been significantly reduced with this electrolyte system.

[0106] Example 10 includes a test cell with a non-aqueous electrolyte (ionic liquid). Non-aqueous electrolytes include ionic liquids that can be prepared according to literature specifications: the ethyl methyl imidazolium cation (abbreviation: "EMIM") and fluoride anions, each with either two or three HF molecules attached by hydrogen bonds.

[0107] Another non-aqueous electrolyte is ethyl methyl imidazolium tetrafluoroborate, which was additionally mixed with solid NFLF. In the test cell according to Example 10, the anode material comprises silicon particles D in a carbon matrix. The open circuit voltage U0 of this primary cell reaches just under 1.2 V and thus almost the theoretical value measured for a single silicon primary cell of this geometry. The performance of the cell was somewhat lower than the cell according to Example 9 and better than that of the other battery cells tested. Figure 10 shows the load diagram of the cell, with the figure on the left documenting the 1st test section and the second figure on the right documenting the 2nd test section (y-axis: U [mV] or l / A [mA / cm 2 ]; P / A [mW / cm 2], x-axis: t [min]). The load diagrams of the primary cell (anode material: 30 wt.% silicon particles D + Vulcan-XC72R, electrolyte: EMIM-BF4 (with possibly a small concentration of dissolved NH4F), cathode material: 90 wt.% MnO2 from Tosoh with graphite).

[0108] In Example 11, silicon particles A and an aqueous NaCl-NaF electrolyte were used. For modification, an aqueous solution containing partially precipitated and partially dissolved NaF was tested as a further electrolyte component with a limited fluoride ion concentration. The solubility of NaF in water is approximately 50 g / L (based on the volume of the pure solvent). To keep the fluoride ion concentration as low as possible, a high Na concentration was aimed for. The electrolyte solution was prepared by adding 2.5 g of an aqueous solution containing 40 wt.% NH4F to 25 g of a saturated NaCl solution, with solid NaF precipitating as a relatively fine-crystalline slurry. To improve the wettability of silicon and carbon black, an additional 2 mL of a diluted wetting agent comprising a polyether was added. Similar to the other examples, the cathode consists of 90 wt.% MnO2 from Tosoh and 10 wt.% graphite powder. As in all experiments, a fleece was used as a separator.

[0109] For example 11 with the anode material silicon particles A, Figure 11 (y-axis: U [mV] or P / A [mW / cm 2 ], x-axis: l / A [mA / cm 2 ]) The corresponding load diagram for primary cell example 11 with an anode material consisting of 30 wt.% silicon particles A + 70 wt.% Vulcan-XC72R, electrolyte: NaCl-NaF electrolyte, cathode made of 90 wt.% MnO2 from Tosoh, and 10 wt.% graphite powder; a fleece was used as the separator. The load diagram shows very good performance and power matching at a load voltage UL of 0.8 volts.

[0110] Through targeted variations, especially in the electrolyte composition, the performance of the silicon primary cells was increased by a factor of about 20 over the course of the tests. The most powerful silicon primary cell differs in initial performance by only a little over an order of magnitude from the Zn batteries measured with the same test setup. It should be noted that the amount of Zn in the Zn batteries is several times the amount of Si in the silicon primary cells (approximately 8 times the theoretical battery capacity). Although the specific surface area of ​​the comparatively coarse Zn particles is considerably smaller than that of the silicon particles, it should be taken into account that with 8 times the amount of silicon powder, the current density also increases, making it comparable to that of the Zn cell.

[0111] Solubility of selected fluorides in water (at temp, in °C) in g / L water: CaF2: 0.015 (20);

[0112] MgF2: 0.13; SrF2: 0.12 (25); BaF2: 1.2 (25); LiF: 2.7 (20); MnF2: 10; CoF2: 14.2 (25); ZnF2: 15 (20) (ZnF2*4H2O); NiF2: 25.6 (25); NaF: 42.2 (20); CuF2: 47 (20);

[0113] KF: 485 (20); NH4F: 820 (20); RbF: 1306 (18); AgF 1850 (15.5); CsF3670 (18)

[0114] Measured bulk densities in g / mL (Silicon particles B: 0.114; 0.110; Silicon particles D: 0.027; 0.024; Silicon particles A: 0.039; 0.039; Vulcan-XC72R: 0.080; Graphite: 0.30; 30 wt% Silicon particles D + Vulcan-XC72R 0.053; 0.053; 0.053; 30 wt% Silicon particles A + Vulcan-XC72R 0.064; 0.064; Zn dust "ZP001", battery grade 4.08)

Claims

Patent claims 1. Electrochemical primary cell comprising an anode, a cathode, an electrolyte and at least one separator, wherein the separator separates the cathode and the anode from each other, and the cathode comprises manganese dioxide and optionally a carbon-containing conductivity enhancer as material, characterized in that the anode comprises silicon as an anode material, wherein the silicon is in the form of silicon particles, the silicon primary particles having a particle size between 1 nm and 3000 nm, and the silicon primary particles are optionally substantially amorphous.

2. Primary cell according to claim 1, characterized in that a) the material of the cathode of the primary cell comprises manganese dioxide as the cathode material, wherein in particular the cathode material is present as the cathode in a hermetically sealed battery housing, or b) the cathode of the primary cell is an air cathode and the cathode as a material comprises a manganese oxide, in particular manganese oxide and / or manganese dioxide, platinum, platinum-based, silver individually or jointly as a catalyst.

3. Primary cell according to claim 1 or 2, characterized in that the silicon particles are in the form of agglomerates of primary silicon particles, aggregates of primary silicon particles or mixtures of these agglomerates and aggregates, and the agglomerates and / or aggregates have a size of 100 to 3000 nm.

4. Primary cell according to one of claims 1 to 3, characterized in that the electrolyte is selected from a) an aqueous fluid composition containing alkaline salts, b) an aqueous or non-aqueous fluid composition containing fluoride anions, c) an aqueous composition containing fluoride anions with a content of undissolved fluoride, in particular the composition comprising at least one salt selected from MnF2, NFLF and / or KF, or d) a non-aqueous composition containing fluoride anions comprising at least one ionic liquid optionally in the presence of further salts of fluoride anions.

5. Primary cell according to one of claims 1 to 4, characterized in that the electrolyte comprises inorganic salts and has a pH value of 2 to 9.5 and optionally includes a buffer and / or a buffer system.

6. Primary cell according to one of claims 1 to 5, characterized in that the electrolyte is an aqueous composition containing hydroxide anions, carbonate anions or halide anions, in particular fluoride anions and / or chloride anions.

7. Primary cell according to one of claims 1 to 6, characterized in that the aqueous electrolyte comprises at least one salt selected from manganese difluoride, manganese dichloride, ammonium fluoride, potassium hydroxide, sodium hydroxide, ammonium chloride, sodium chloride, sodium fluoride, potassium fluoride and / or a salt of a carboxylic acid.

8. Primary cell according to one of claims 1 to 7, characterized in that the electrolyte contains manganese difluoride, manganese dichloride and / or ammonium fluoride and optionally potassium fluoride.

9. Primary cell according to one of claims 1 to 8, characterized in that the cathode material comprises manganese dioxide to 70 to 95 wt.% as cathode material and comprises a carbon-containing conductivity enhancer and optionally further additives to 100 wt.% of the cathode material, in particular the cathode comprises carbon-containing particles or a carbon-containing paste as conductivity enhancer.

10. Primary cell according to one of claims 1 to 9, characterized in that the anode material comprises silicon particles and conductivity mediators, in particular the conductivity mediator comprises carbon-containing particles or a carbon-containing paste.

11. Primary cell according to one of claims 1 to 10, characterized in that i) the carbon-containing particles comprise soot, conductive soot, electrochemically produced soot, graphite, graphene and / or ii) the carbon-containing paste comprises electrically conductive polymers and / or graphene as a carbon-containing conductivity mediator.

12. Primary cell according to one of claims 1 to 11, characterized in that the silicon of the anode material comprises dopants, wherein the dopants are selected from elements of the 13th main group, in particular comprising boron, indium, aluminium and / or gallium, and from elements of the 15th main group, in particular comprising phosphorus, arsenic and / or antimony and optionally selected from elements of the iron group.

13. Primary cell according to one of claims 1 to 12, characterized in that the silicon of the anode material comprises dopants, wherein the dopants are greater than or equal to 1 element of group 15 on 10 6 Silicon atoms and / or greater than or equal to 1 element of the 13th main group per 10 6 Silicon atoms are present.

14. Primary cell according to one of claims 1 to 13, characterized in that the electrolyte comprises a wetting agent, in particular the wetting agent comprises surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, organic solvents such as alcohol, ketone, ether, polyether, such as polyethylene oxide and / or polypropylene oxide.

15. Multi-cell battery, characterized in that the battery comprises at least two to 15,000 interconnected primary cells according to any one of claims 1 to 14, preferably the two to 15,000 interconnected primary cells are connected in series.

16. Use of silicon as an anode material in the form of silicon particles, which are referred to as silicon- Primary particles with a particle size between 1 nm and 3000 nm are present and the anode material in the charged state does not include lithium, in particular the silicon primary particles form agglomerates and / or aggregates mixtures thereof, wherein the silicon primary particles are optionally essentially amorphous.