DE102018208017A1 - Energy storage protected by a composite material - Google Patents

Abstract

The present invention relates to the use of a composite material comprising fibers and graphite foil to protect an energy store which heats up during charging and / or discharging, e.g. the energy storage of a vehicle that heats up during charging and / or discharging.

Description

The present invention relates to the use of certain composite materials to protect energy storage devices which heat up during charging and / or discharging, in particular energy storage devices which drive an electric motor driving a vehicle, such as lithium-ion batteries in electric cars.

Batteries are enveloped, e.g. through a battery case. In general, the sheaths serve to hold a plurality of electrochemical cells in position relative to each other and to position the battery in the desired position, e.g. in a vehicle, firmly anchored.

The U.S. Patent No. 8,852,794 B2 describes a battery case for an electric vehicle. The battery case can be used in the vehicle or for storage of batteries outside the vehicle. As housing materials plastic or metals are proposed. Polyethylene materials are said to have relatively high stability, low friction with many other materials, and high resistance to acids and water.

The DE 10 2010 048 102 A1 describes a vehicle having a crash energy absorbing traction battery. The traction battery is deliberately designed as a deformation element, with non-destructively deformable memory cells. The existing of the individual memory cell memory block can be enclosed in a battery case gas and liquid-tight. For this purpose, it is proposed that the battery case is designed not resistant to components or dimensionally stable, but from an easily deformable material. As examples, a rubber-like high-tenacity shell material is called, as it is used for example in fuel tank bladders.

The U.S. Patent No. 8,393,427 describes a vehicle battery pack protection system, comprising: a battery pack housing mounted under an electric vehicle, the battery pack housing including a housing top, a housing bottom, and a plurality of housing side parts, the battery pack housing configured to receive a plurality of batteries, and wherein the battery pack housing is mounted between a passenger compartment floor panel and a drive surface; a ballistic shield mounted under the electric vehicle and under the battery pack housing, wherein the ballistic shield is disposed between the battery pack housing and the drive surface and wherein the ballistic shield is spaced at least 5 millimeters from the housing bottom plate; and a layer of compressible material disposed between the ballistic shield and the battery pack housing. The layer of compressible material may be made of foam or plastic. For example, the layer may be formed with a plurality of protrusions and a plurality of recesses; is called, for example, a urethane foam. The ballistic shield may be made of aluminum, aluminum alloy, steel, glass fiber, carbon fiber epoxy composite and / or plastic. The protection system is intended to fully integrate the battery pack housing into the vehicle while protecting the battery pack from accidental damage and minimizing the effects of the battery pack on the comfort and safety of vehicle occupants.

The utility model DE 20 2015 106 607 U1 Describes that the battery of an electric vehicle during a collision of the vehicle; that is, during a vehicle-to-vehicle collision, may be subject to damage. It is also described that the battery must be placed in a suitable location that limits the exposure of the battery during vehicle crashes. Proposed, among others, is a battery post that includes a housing having a bottom and a bottom-extending side. The housing is configured on an interior surface for receiving the battery for the electric vehicle. The battery post includes a deformable energy absorber defining a repeating pattern of hexagonal cells tessellated in a honeycomb structure. It is proposed that cell material, cell geometry, cell wall thickness and cell side length be matched depending on the expected load. For example, cells and housings can be made of aluminum, with the aluminum alloy 6111-T4 in particular being proposed.

The object of the present invention is to protect an energy store, which heats up during charging and / or discharging, from damage by acting forces, for example during rockfall or when a vehicle collides, and at the same time to improve its passive cooling capability.

This object is achieved by the use of a composite material comprising fibers and graphite foil to protect an energy store which heats up during charging and / or discharging, e.g. the energy storage of a vehicle that heats up during charging and / or discharging.

It can be a stationary energy storage, eg a stationary battery or a mobile energy storage, such as a mobile battery act. Batteries are understood to mean rechargeable batteries in the context of this invention.

Even with stationary energy storage, which are often considerably larger than mobile energy storage, the protection against damage by acting forces, is particularly important. Such energy storage can be released in case of damage large amounts of energy. Accordingly, the risks are high for people in the area. This applies to stationary batteries in large buildings, which may not be damaged in case of earthquakes by falling building parts. The same applies to stationary batteries in places where they may be damaged by accidents involving air, rail or road vehicles. Especially here it is important to reduce damage to the energy storage by acting forces and to improve the passive cooling ability.

The energy store is preferably an energy store of a vehicle that heats up during charging and / or discharging, in particular an energy store of a vehicle that heats up when charging and / or discharging with electric current. Preferably, the energy storage drives at least one of the drive of the vehicle serving electric motor. Then the advantages of the invention come into play especially. It has been found that both the low mass of the composite material and the passive cooling capability ultimately contribute to increasing the range of the vehicle. The reduced mass has a direct effect on energy consumption. The improved passive cooling reduces the need for energy-consuming active cooling of the energy store, so that a higher proportion of the energy stored in the energy store can be used to drive the vehicle. At the same time, the life of the energy storage increases. The life increases especially if it is the energy storage is a battery. Batteries, and especially lithium-ion batteries, age faster at elevated temperatures. It is believed that the composite material according to the invention compensates for temperature peaks and thereby increases the service life of the battery cells. As a result, the vehicle operated with the energy store can be driven particularly efficiently overall. The vehicle is preferably a land vehicle (e.g., a HEV or BEV) or an aircraft.

The invention also relates to an energy storage device for a vehicle that heats up during loading and / or unloading and is at least partially surrounded by a composite material, wherein the composite material comprises fibers and graphite foil.

A further object according to the invention is a vehicle having an energy store which heats up during loading and / or unloading, wherein the energy store is at least partially surrounded by a composite material and the composite material comprises fibers and graphite foil.

Typically, the composite material is planar. It preferably has two main surfaces, one of the main surfaces facing the energy store and the other main surface facing away from the energy store.

In the vehicle according to the invention, part of the main surface facing away from the energy store or the entire main surface facing away from the energy store may face the ground on which the vehicle is located, for example a road. This protects the energy storage from mechanical damage from below, for example against falling rocks.

In the vehicle according to the invention, part of the main surface remote from the energy store or the entire main surface facing away from the energy store may face the front of the vehicle and / or the rear of the vehicle. This protects the energy storage, especially in rear-end collisions, in which the vehicle with the front or the rear on an object, e.g. another vehicle, opens up.

In the vehicle according to the invention, part of the main surface remote from the energy store or the entire main surface facing away from the energy store may face the driver's side or the passenger side of the vehicle. This protects the energy storage, especially in rear-end collisions, in which another vehicle impacts one of the sides of the vehicle according to the invention.

To protect the energy storage device, a plurality of composite materials may be used, wherein according to the invention at least one of the composite materials comprises fibers and graphite foil. For example, substantially planar composite materials may be disposed on different sides of the energy store, e.g. below the energy store, at the front of the energy store, at the back of the energy store and / or on one or both sides of the energy store.

Alternatively, the composite material can extend around the energy store in such a way that it at the same time extends into an area below the energy store and into at least one area at the front of the energy store and / or at the rear of the energy store; or that it is at the same time in an area below the energy store and in at least one area at one or both Sides of the energy store extends. For this purpose, the composite material must have at least one kink or bend.

The information "below", "front", "rear", "on one or both sides of the energy storage" refer to the orientation of the energy storage device, if it is intended to be installed in the vehicle. Thus, "front" refers to the side of the energy accumulator installed as intended in the vehicle, and "rear" to the front of the vehicle, and the side of the energy accumulator installed as intended in the vehicle that faces the rear of the vehicle.

Preferably, at least a portion of the composite material in the direction of travel is arranged in front of or behind the electrical energy storage or arranged under the electrical energy storage.

Wobei

n

für 3; insbesondere für 2; vorzugsweise für 1,5; besonders bevorzugt für 1 steht; und

A

die Oberfläche der dem Energiespeicher zugewandten Hauptfläche des Verbundmaterials ist.

In general, the composite material is arranged close to the energy store. It may, for example, rest on the surface of the energy store. Each point of the energy storage-facing main surface of the composite material has a certain distance d to the energy storage. Preferably, the main surface facing the energy store applies for each point: $$d<n\cdot \sqrt{A}$$

In which

n

for 3; especially for 2; preferably for 1.5; particularly preferably 1; and

A

the surface of the energy storage facing main surface of the composite material is.

This will ensure that the composite material is close to the energy store. This reduces the risk of damage to the energy storage by reaching between composite material and energy storage vehicle parts in accidents or passing between composite material and energy storage stones in case of rockfall. Because the space between energy storage and composite material is limited by this feature.

wobei

m

für 0,005; insbesondere für 0,01; vorzugsweise für 0,02; besonders bevorzugt für 0,05 und ganz besonders bevorzugt für 0,1 steht; und

A

die Oberfläche der dem Energiespeicher zugewandten Hauptfläche des Verbundmaterials ist.

In certain embodiments, for each point of the energy storage facing main surface: $$d>m\cdot \sqrt{A}$$

in which

m

for 0.005; in particular for 0.01; preferably for 0.02; more preferably 0.05, and most preferably 0.1; and

A

the surface of the energy storage facing main surface of the composite material is.

This ensures that the composite material maintains a defined distance to the energy store. This reduces the risk of unwanted electrical charging of the graphite foil of the composite material through the energy storage device and ensures that there is sufficient space for a heat conductor everywhere between the composite material and the energy store. Ultimately, this increases the reliability, in particular the risk of electric shock when reaching a place of accident people who may come in contact with the composite material.

According to the invention, the composite material comprises fibers and graphite foil.

As is known, graphite foils can be produced by treating graphite with certain acids to form a graphite salt with acid anions interposed between graphene layers. The graphite salt is then expanded by exposing it to high temperatures of eg 800 ° C. The graphite expandate obtained during the expansion is then pressed into the graphite foil. A process for the production of graphite foils is for example in EP 1 120 378 B1 described.

In principle, according to the invention, any fibers can be used. There are no known fibers that can not be processed with graphite foil into a composite material. However, it is generally preferred to use particularly strong fibers. For example, the fibers have a strength of more than 600 MPa, in particular more than 1200 MPa, preferably more than 1500 MPa, particularly preferably more than 2000 MPa. The strength is the tensile strength. It can be determined by measuring methods well known to those skilled in the art. The use of particularly strong fibers offers the advantage that even with a low fiber basis weight, thus e.g. with very thin fiber layers a very high protection of the energy storage against unwanted mechanical effects, such as penetration vehicle parts in case of accidents or stones in case of rockfall can be achieved. The fibers may e.g. Carbon fibers, aramid fibers and / or glass fibers include. Carbon fibers are particularly preferred.

The graphite foil and the fibers may be incorporated in a layer of the composite material.

In general, however, the composite material is a laminar composite material comprising a fibrous layer and a graphite foil layer. Preferably, the fibers are then arranged in the fiber layer and the graphite foil is arranged in the graphite foil layer. Layered composite materials are preferred composite materials according to the invention, since they can be produced in a particularly simple manner by applying a graphite foil to a fibrous layer, for example by gluing. The thickness of the fiber layer may be, for example, 0.5 to 5 mm, preferably 0.8 to 4 mm, particularly preferably 1 to 3 mm.

In one embodiment, the fibers, e.g. the fibrous layer, with a resin to the graphite foil, e.g. to the graphite foil layer, bound. The resin may e.g. be selected from thermoplastics and thermosets such as epoxy resins and phenolic resins. Preferably, the resin is an epoxy resin. Other suitable resins include, inter alia, unsaturated polyesters, bismaleimides, polyimides, cyanate esters, polyphenylenes, polysulfones, polyethersulfones, polyphenylene sulfides, polyether ketones, polybenzimidazoles, polyamides and polyetherimides.

The fibrous layer may be a fiber composite of fibers, e.g. Carbon fibers and resin matrix, wherein the fibers are substantially completely enclosed by the resin. As matrix matrix suitable matrix polymers are in the book "Carbon fibers and their composites, manufacturing processes, applications and market development", Verlag Moderne Industrie GmbH, ISBN 978-3-86236-001-7 from page 28 described.

In one embodiment, the resin of the resin matrix is the resin with which the fibrous layer is bonded to the graphite foil. This is preferred since the layer composite can then be produced in a particularly simple manner by applying a prepreg to the graphite foil. However, the resin of the resin matrix may also be different from the resin with which the fiber layer is bonded to the graphite foil.

The fibers may be substantially parallel to each other or in different directions. The fibrous layer may be a fiber knit, a fiber web or a fibrous web, e.g. a carbon fiber fabric, carbon fiber fabric or carbon fiber fabric. The clutch may be a biaxial clutch or a multiaxial clutch.

Preferred fiber composites are described in the book "Carbon fibers and their composites, manufacturing processes, applications and market development", Verlag Moderne Industrie GmbH, ISBN 978-3-86236-001-7 from page 35. The fiber composite may therefore be a carbon fiber reinforced plastic (CFRP). The cited book also describes the production of CFK from page 35 onwards. The manufacturing and molding processes described therein can be used to bring a CFRP into the desired form for the protection of the energy storage device according to the invention. One or more layers of graphite foil may be applied before or after any necessary curing of the CFRP formed to the desired shape to obtain the layered composite comprising the fibrous layer and the graphite foil layer.

In certain composite laminates according to the invention, the fibers are substantially completely enclosed by the resin in one part of the surface of the laminar material and attached to the graphite foil in another part of the surface of the laminate only over the surface of the fibrous layer.

The layered composite material comprises a fibrous layer and a graphite foil layer. In general, the graphite foil layer faces the energy store and the fiber layer faces away from the energy store. This increases the passive cooling ability, since heat then passes unhindered from the energy storage in the graphite foil.

The layered composite material may comprise further layers, e.g. a further fiber layer on the energy storage side facing the graphite foil layer. The further fibrous layer is preferably very thin, e.g. 0.02 to 3 mm thick, preferably 0.05 to 2 mm thick, so as not to complicate the transfer of heat from the energy storage in the graphite foil layer unnecessarily. An advantage of the further fiber layer on the energy storage side facing the graphite foil layer is an increase in the elastic deformability of the composite material, since the graphite foil layer is then fiber reinforced on both sides.

The laminar material may e.g. have a further graphite foil layer on the side facing away from the energy storage side of the fiber layer. The additional layer of graphite foil reduces the risk of damage caused by stone chips. Presumably, this is due to an inherent dry lubricating effect of the graphite, which in particular "smears" flat objects with a smooth surface.

The invention also relates to a layered composite material which can be used, for example, to protect an energy store, comprising a fibrous layer, for example those described herein A fibrous layer and a graphite foil layer, eg a graphite foil, wherein the graphite foil layer has a plurality of openings which extend through the graphite foil layer.

Preferably, the graphite foil layer has a plurality of openings. The arrangement of the apertures preferably defines a repeating pattern of apertures and inter-apertured graphite film layer portions.

In the repeating pattern, the ratio of the area occupied by the openings to the base area of the graphite foil layer is preferably in the range of 0.01 to 0.98, more preferably in the range of 0.05 to 0.90; most preferably in the range of 0.10 to 0.85. The base area of the graphite foil layer is understood to be the area occupied in the repeating pattern by the openings and the inter-opening graphite foil layer sections as a whole. The ratio of the area occupied by the openings to the base area of the graphite foil layer should be small if a high thermal conductivity in the graphite foil layer is desired. On the other hand, by increasing the ratio, the basis weight of the composite material can be reduced. In particular, if the ratio of the area occupied by the openings to the base area of the graphite foil layer is large, the graphite foil layer in the layered composite fulfills a similar stiffening effect as a honeycomb layer formed of paper or aluminum, as described, for example, in US Pat DE 20 2015 106 607 U1 is shown. In addition, since graphite foils are compressible, higher ductility is achieved compared to stiffening with conventional honeycomb layers. In addition, the heat conductivity in the plane is high, since graphite foils excellently conduct heat in the plane. Both effects are particularly in connection with the protection of a charging and / or discharging warming energy storage of a vehicle of decisive advantage. The risk of mechanical damage is reduced by a yielding of the ductile layer composite, while maintaining high passive cooling capability.

The openings can have any shape. For example, they can be triangular, quadrangular, pentagonal, hexagonal, round or oval. In preferred embodiments, the openings are round. Round openings can be introduced very easily by punching, which favors a particularly efficient production of the layer composite. The area of each individual opening can be, for example, in the range from 0.1 mm ² to 400 mm ² , preferably in the range from 0.2 mm ² to 100 mm ² .

In a layered composite material according to the invention, at least a part of the openings is at least partially filled with resin. This offers the advantage of further stabilization of the layered composite material, since a layer located on one side of the graphite foil can be directly connected to a layer located on the other side of the graphite foil through the openings. For example, the fiber layer is directly connected to the optional further fiber layer.

The carbon fibers used may contain different numbers of individual filaments. For example, from 1,000 (1k fibers) to 320,000 individual filaments (320k fibers). Preferably, the carbon fibers have 1000 (1k fibers) to 10,0000 single filaments (10k fibers), e.g. about 3,000 individual filaments (3k fibers).

According to the invention, the composite material serves to protect an energy store which heats up during charging and / or discharging. In particular, the composite material serves to protect the energy storage against mechanical damage and overheating.

Preferably, the energy store is selected from batteries and capacitors, in particular batteries. The battery is eg a lithium ion battery. By a lithium-ion battery is meant a battery in which an electron donation of Li contributes to the provision of the usable electric current to form Li ⁺ ions. Such batteries heat up during charging and discharging.

The composite material develops the desired effect if the heat radiated from the energy store is absorbed by the composite material and dissipated therein, in particular via the graphite foil.

Preferably, however, the graphite foil is in thermal contact with the energy store. For this purpose, a heat conduction path between energy storage and graphite foil is formed. The heat conduction path may include heat conductive solids and / or liquids.

The thermal contact with the energy storage, for example, by the graphite foil is thermally in contact with a part of the Wärmeleitpfads and another part of the Wärmeleitpfads thermally in contact with the energy storage, for example with an energy storage cell of the energy storage. The heat conduction path may be formed, for example, by a cooling liquid circulated between the energy store and the graphite foil or by a solid heat conduction element, for example by a heat conduction plate, wherein a part of the Wärmeleitplatte in contact with the composite material, for example, in contact with the graphite foil is, and another part of the heat conducting in contact with the energy storage, for example with a cell of a battery is.

According to the invention, for example, essential parts of in US 8,852,794 B2 and DE 10 2010 048 102 A1 described battery housing, of the U.S. Patent No. 8,393,427 described battery pack housing or in DE 20 2015 106 607 U1 described battery support, consist of a composite material described herein.

• 1 ein Fahrzeug aufweisend einen mindestens teilweise von Verbundmaterial umgebenen Energiespeicher
• 2A einen Ausschnitt des Verbundmaterials aus 1, betrachtet von der dem Energiespeicher zugewandten Seite
• 2B eine Seitenansicht des Verbundmaterials aus 1

Other features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawings.

• 1 a vehicle having an at least partially surrounded by composite energy storage
• 2A a section of the composite material 1 , viewed from the energy storage side facing
• 2 B a side view of the composite material 1

1 shows a vehicle 1 with an energy storage, which is a lithium-ion battery 2 is. The lithium ion battery 2 is partially made of a composite material 10 surround. In the example shown here, the composite material extends around the energy store in such a way that it at the same time extends into an area below the energy store, into an area at the front of the energy store and into an area at the rear of the energy store. Graphite foil of the composite material is above a Wärmeleitblech 21 in thermal contact with the lithium ion battery.

2A shows a section 11 of the composite material 1 , viewed from the energy storage side facing. 2 B shows the same section 11 in a side view. The composite material is a layer composite material according to the invention comprising a fiber layer 16 and a graphite foil layer 12 wherein the graphite foil layer has a plurality of round openings. One of the openings is denoted by the reference numeral 13 characterized. The openings extend through the graphite foil layer so that the fiber layer 16 in 2A through the openings can be seen.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8852794 B2 [0003, 0051]
• DE 102010048102 A1 [0004, 0051]
• US 8393427 [0005, 0051]
• DE 202015106607 U1 [0006, 0042, 0051]
• EP 1120378 B1 [0027]

Claims (10)

Use of a composite material comprising fibers and graphite foil to protect an energy store which heats up during charging and / or discharging, e.g. the energy storage of a vehicle that heats up during charging and / or discharging. Use after Claim 1 wherein the composite material is a layered composite comprising a fibrous layer and a graphite foil layer, the fibers are disposed in the fibrous layer, and the graphite foil is disposed in the graphite foil layer. Use after Claim 1 or 2 , wherein the graphite foil is in thermal contact with the energy storage. Use according to any one of the preceding claims, wherein the energy store is under batteries, e.g. Lithium ion batteries, and capacitors is selected. Use according to any one of the preceding claims, wherein the fibers are bonded to the graphite foil with a resin. Use according to any one of the preceding claims, wherein the fibers have a strength greater than 1500 MPa and e.g. Carbon fibers, aramid fibers and / or glass fibers include. Use according to one of the preceding claims, wherein at least a part of the composite material in the direction of travel is arranged in front of or behind the electrical energy storage or is arranged under the electrical energy storage. A laminar composite comprising a fibrous layer and a graphite foil layer, the graphite foil layer having a plurality of apertures extending through the graphite foil layer. Energy storage for a vehicle that heats when loading and / or unloading and is at least partially surrounded by a composite material, wherein the composite material comprises fibers and graphite foil. Vehicle having a at least partially surrounded by a composite energy storage device Claim 9 , wherein the composite material, for example, a laminated composite according to Claim 8 is.

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