Energy storage device with solid electrolyte on a mineral binder base

Abstract

Energy storage device consisting of an anode, a cathode and a solid electrolyte, characterized in that, to improve temperature resistance and operating characteristics, a graphite foil is provided as the anode and a metal foil, preferably aluminum foil, as the cathode, wherein a layer of a solid electrolyte based on a mineral binder is located between these.

Description

Prior Art:Since the 1990s, lithium ion batteries have become the main source of energy storage in portable devices and electric vehicles. However, safety concerns, wear and environmental impact have advanced the search for alternative solutions. Solid electrolyte technology has developed widely over the last two decades and is estimated for its ability to improve the stability and safety of batteries.Modern energy technology and electronics place high demands on reliable, long-lived and environmentally friendly energy storage systems. Technologies developed intensively in recent years include electrochemical energy stores which use solid-state electrolytes. Such devices are used in energy storage systems for renewable energy sources, portable electronics, uninterrupted power supply systems and in automotive and industrial automation.Solid electrolytes can be divided into several types:• Ionic conductors based on oxides - are distinguished by high ionic conductivity and good chemical stability.• Polymer electrolytes - offer flexibility and ease while maintaining good electrical properties.• Sulfide electrolytes - have high ionic conductivity but are sensitive to moisture and oxygen.Examples of solid electrolyte with lithium additions:• Lithium-based solid electrolyte such as lithium-biotite oxides (e.g., Li7La3Mn2O12-LLZO) have high ionic conductivity and are used in lithium-ion batteries.• Some sulfide electrolytes, such as Li2S-P2S5, contain lithium and are characterized by high ionic conductivity. These materials provide excellent electrochemical properties, making them suitable for high efficiency batteries.• Polymer electrolytes with lithium salts, such as polyethylene oxide (PEO) with lithium salt additions, can be used to improve the conductivity and stability of solid state electrolytes.Solid electrolytes offer several advantages over liquid and gel-like alternatives. These include high mechanical strength, temperature resistance, no leaks and the possibility of compact constructions. Another important advantage is the increased safety of the apparatus by eliminating volatile and combustible liquids. Most modern solutions are, however, based on polymeric or ceramic materials which have some disadvantages: high raw material costs, complicated manufacturing technologies, low environmental friendliness and limited mechanical properties.Examples of existing solutions for lithium-based solid electrolyte: JP20119200851; EA201290999; US 2023 / 0140434 A1; EP 4 126 765 B1; WO 2021 / 198183 A1; CN113544875.Sulfide-based solid electrolyte, for example U.S. Pat. No. 11,837,721 B2.Electrolytes based on compounds of rare and rare earth elements, for example WO 2019 / 173626 A1.All these technical solutions are very complex in technical implementation and scaling. Rare chemical elements are required for their reproduction, in particular lithium. The recovery and production of lithium is not only energy intensive and environmentally harmful, but the presence of this element is also limited in the earth's crust and in the ocean.At present, developments using mineral materials as bases for solid electrolytes are of great interest. Mineral binders such as magnesium cement or kaolin are distinguished by availability, low costs and high resistance to external influences. Such materials also simplify the manufacturing process and reduce environmental impact. However, their use in electrochemical energy stores has not yet been studied, which restricts their broad introduction.At the time of application, no publications or patents have been found disclosing the use of solid state electrolyte energy stores based on mineral binders, in particular magnesium cements and kaolins (refractory clays).This technical solution aims to solve the above-mentioned problems by using a mineral binder in the solid electrolyte. The proposed approach combines the advantages of mechanical strength and heat resistance of mineral materials with the electrochemical stability required for efficient energy storage. The introduction of an aqueous graphene dispersion and the use of special additives additionally improve the conductivity and provide a high performance of the device.The use of magnesium binders, in particular Sorel cement, enables the production of solid solid electrolytes whose mechanical strength is maintained even at a binder content of up to 25% by volume.Graphene dispersions that dissolve easily in the components of magnesium cements contribute to increasing the mechanical strength.The concentration limits of low-layer graphene in aqueous graphene dispersions are determined by its electrical properties: concentrations below 2% do not provide sufficient ionic movement in the solid electrolyte; concentrations above 8% can lead to leakage currents due to local short circuits. Low-layer graphene can relate in particular to the range of approximately 2-30 layers.A very important property of magnesium binders, including Sorel cement, is the constant volume during the preparation of the binder, the shaping of the solid electrolyte and under thermal operating conditions.The use of kaolin or refractory clay as binder makes it possible to obtain, at the solid electrolyte forming stage, a plastic material which offers versatility and easy displaceability of the electrolyte.Thanks to the structure of refractory clays and kaolins containing the mineral kaolinite, which resembles graphite in its physical properties, mixtures with graphene dispersion show complex, poorly studied properties:The dipole moments of the kaolinite molecules are oriented so as to minimize the energy of the system by attracting to the zone of opposite charge or higher electronic potential if graphene is functionalized.When graphene approaches kaolinite, the dipoles seek an orientation which allows maximum interaction, which can lead to the formation of layer structures or complexes with a specific geometry.These interactions can affect the mechanical and electrical properties of the composites made from these components.It has been found experimentally that a kaolinite content of less than 15% in kaolins and refractory clays is not sufficient to ensure sufficient ionic conductivity in the solid electrolyte. It has also been observed that as kaolinite content increases, the ionic conductivity of kaolins and refractory clays increases.With solid electrolyte thicknesses of more than 3 mm, the internal resistance of the electrolyte increases significantly. Therefore, it is recommended to reduce the electrolyte thickness to as small a level as possible, but not thinner than 0.5 mm, in order to obtain the structural strength of the solid electrolyte.In the production of an accumulator according to this technical solution with a solid electrolyte surface of more than 50 cm 2 basalt, glass or cellulose fibers must be added in amounts that are required to form a reinforcing mesh in order to avoid cracks and chipping in the electrolyte.Thus, the proposed mineral binder-based solid electrolyte energy storage device offers the potential for significantly reducing production costs, increasing environmental friendliness, and simplifying the manufacturing process. Its development represents an important advance in the field of electrochemical energy stores and opens up new possibilities for scalable and efficient energy storage.This technical solution is explained by FIG. 1, wherein: 1 cathode 2 solid electrolyte 3 anodeReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 20196200851

[0006] US 2023 / 0140434 A1

[0006] EP 4 126 765 B1

[0006] WO 2021 / 198183 A1

[0006] CN 113544875

[0006] U.S. Pat. No. 11,837,721 B2

[0007] WO 2019 / 173626 A1

[0008]

Claims

Energy store, consisting of an anode, a cathode and a solid electrolyte, characterized in that, in order to improve the temperature resistance and the operating properties, a graphite foil is provided as the anode and a metal foil, preferably aluminium foil, is provided as the cathode, a layer of a solid electrolyte based on mineral binder being located between these.Energy store according to Claim 1, characterized in that the graphite foil can be used simultaneously as anode and cathode.Energy store according to Claims 1 and 2, characterized in that magnesium cement, including Sorel cement, is provided as the mineral binder.Energy store according to Claim 1, characterized in that kaolin or refractory clay is provided as mineral binder for producing the solid electrolyte.Energy store according to Claim 4, characterized in that the kaolinite content in the kaolin or refractory clay is not less than 15%.Energy store according to Claims 1 to 5, characterized in that the mineral binder in the solid electrolyte makes up at least 25% by volume.Energy store according to Claims 1 to 6, characterized in that the solid electrolytes are produced from an aqueous graphene dispersion having a graphene concentration in the range from 2 to 8% by weight with respect to the mineral binder.Energy store according to Claim 7, characterized in that the aqueous graphene dispersion comprises aggregates of low-layer graphene, which predominantly consist of 3 to 20 layers of elemental graphene.Energy store according to Claims 1 to 8, characterized in that the thickness of the solid electrolyte layer does not exceed 3 mm, a preferred thickness being below 1 mm.Energy store according to Claims 1 to 8, characterized in that water-soluble, ion-conducting salts which do not alter the structure of the solid electrolyte and do not impair its strength are additionally added to the solid electrolyte in order to reduce the electrical resistance.Energy store according to Claims 1 to 10, characterized in that, with a lateral surface of the solid electrolyte of more than 50 cm 2 cellulose, basalt or other mineral fibers which are not electrical conductors are added to the solid electrolyte in order to avoid cracks and chipping.

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