Energy storage element having a prismatic housing

Abstract

The energy storage element (100) includes a plurality of anodes (120) and cathodes (130). Each anode (120) and cathode (130) includes a current collector (115, 125) having a main area filled with a layer of a respective electrode material (123, 155) and a free edge strip (117, 121) extending along the edge (115a, 125a) of the current collector that is not filled with the electrode material. The anodes (120) and cathodes (130) are stacked to form an assembly (105), and the anodes (120) and cathodes (130) are separated by separators (118, 119) or layers of solid electrolyte. Here, a free edge strip (121) of the anode current collector (115) protrudes from one side of the assembly (105), and a free edge strip (117) of the cathode current collector (125) protrudes from another side of the assembly (105). The assembly (105) is enclosed by a prismatic housing. The energy storage element has at least one metallic contact element (102, 112) connected to the free edge strips (117, 121) of the anode current collector (115) and / or the cathode current collector (125) by welding or soldering.

Description

[Technical Field]

[0001] The invention described below relates to an energy storage element having a prismatic housing. [Background technology]

[0002] Electrochemical cells can convert stored chemical energy into electrical energy through oxidation-reduction reactions. They generally contain a positive electrode and a negative electrode separated from each other by a separator. During discharge, electrons are released at the negative electrode as a result of an oxidation process. This results in an electronic current that can be drawn by an external electrical consumer, for which the electrochemical cell serves as an energy source. Simultaneously, an ionic flow corresponding to the electrode reactions occurs within the cell. This ionic flow crosses the separator and is ensured by an ion-conducting electrolyte.

[0003] If the discharge is reversible, i.e., if it is possible to reverse the conversion of chemical energy to electrical energy that occurred during discharge and thus charge the cell again, it is said to be a secondary battery. The designation of the negative electrode as the anode and the positive electrode as the cathode is generally used for secondary batteries, but this refers to the discharge function of the electrochemical cell.

[0004] Secondary lithium-ion cells are currently used in many applications because they can supply high currents while at the same time being characterized by a relatively high energy density. They are based on the use of lithium, which in the form of ions can be transported back and forth between the electrodes of the cell. The negative and positive electrodes of lithium-ion cells are often used in the form of so-called composite electrodes, which contain not only electrochemically active components but also electrochemically inactive components.

[0005] In principle, any material capable of absorbing and releasing lithium ions can be used as the electrochemically active component (active material) in secondary lithium-ion cells. Carbon-based particles, such as graphitic carbon, are often used in the negative electrode. Other non-graphitic carbon materials suitable for lithium intercalation can also be used. In addition, metallic and semi-metallic materials capable of alloying with lithium can also be used. For example, elements such as tin, aluminum, antimony, and silicon can form intermetallic phases with lithium. In some embodiments, the negative electrode can also be based on metallic lithium. For example, lithium metal oxides, such as lithium cobalt oxide (LiCoO), lithium manganese oxide (LiMnO), and lithium iron phosphate (LiFePO), or their derivatives, can be used as the active material in the positive electrode. The electrochemically active material is generally contained in the electrode in particulate form.

[0006] As an electrochemically inactive component, a composite electrode generally includes a flat and / or strip-shaped current collector, e.g., a metal foil, that serves as a support for each active material. Typically, the current collector is covered on both sides with a layer of active material. For example, the negative electrode current collector (anode current collector) can be made of copper or nickel, and the positive electrode current collector (cathode current collector) can be made of aluminum. Additionally, the electrode can include an electrode binder (e.g., polyvinylidene fluoride (PVDF) or another polymer, e.g., carboxymethyl cellulose), a conductivity-enhancing additive, and other additives as an electrochemically inactive component. The electrode binder ensures the mechanical stability of the electrode and often ensures the active material adheres to the current collector.

[0007] To produce a secondary lithium-ion cell, a positive electrode and a negative electrode can be combined with one or more separators to form an assembly. Generally, an assembly includes at least the order "positive electrode / separator / negative electrode." However, an assembly may include two or more positive electrodes and one negative electrode. For example, an assembly can include multiple positive and negative electrodes in alternating order, so that in each case adjacent electrodes always have opposite polarities due to the separator provided between the adjacent electrodes. When forming an assembly, it may be advantageous to bond the electrodes and separators together under pressure, optionally by lamination, or by bonding.

[0008] In embodiments of secondary lithium-ion cells having a metallic lithium-based anode, an assembly may also be formed that initially includes only a current collector instead of a negative electrode. In these cases, it is envisioned that lithium is introduced into the cell, for example, through the cathode, and deposited on the current collector during initial charging.

[0009] With the electrodes and separator, the assembly already contains the main structural components of the cell. To convert it into a functional electrochemical cell, it is often necessary to add a liquid electrolyte that impregnates the electrodes and especially the separator. Alternatively, during assembly fabrication, a solid electrolyte that has inherent ionic conductivity and does not require impregnation with a liquid electrolyte can be disposed between the electrodes instead of the separator. In this case, the assembly becomes a functional electrochemical cell immediately after formation.

[0010] The commonly used liquid electrolyte for lithium-ion cells is a solution of at least one lithium salt in an organic solvent mixture. To form a lithium-ion cell with a basic cylindrical shape, ribbon-shaped electrodes and separators can be processed in a winding machine to form a helical winding. Such windings fit snugly into a cylindrical housing.

[0011] However, some applications require energy storage elements with prismatic housings. To produce such energy storage elements, oppositely polarized electrodes with polygonal bases can be stacked to form an assembly with a prismatic base. Within the stack, the oppositely polarized electrodes are generally separated from each other by a separator or layer of solid electrolyte to prevent direct contact between the oppositely polarized electrodes. For example, a cubic assembly formed with rectangular cells fits snugly into a corresponding cubic housing. Within the housing, the electrodes can be electrically interconnected. Typically, electrodes with the same polarity are coupled to a common current conductor within the housing, which is electrically connected to one of the housing components or is routed out of the housing through a corresponding opening.

[0012] Applications in the automotive sector, electric bicycle applications, or similarly other applications with high energy requirements, such as power tools, require energy storage elements with as high an energy density as possible that can be simultaneously loaded with high currents during charging and discharging. Modern lithium-ion cells are already capable of achieving energy densities of up to 270 Wh / kg. However, this energy density is considered to be only an intermediate step. The market is already demanding energy storage elements with even higher energy densities.

[0013] However, when developing improved energy storage elements, not only energy density but also other factors must be taken into account. Two very important parameters are the cell's internal resistance, which must be kept as low as possible to reduce power loss during charging and discharging, and the thermal connection of the electrodes, which may be essential for regulating the cell's temperature. During fast charging of the cell, power loss can cause heat accumulation in the cell and electrode stack, which can lead to significant thermomechanical and electrochemical stresses. When the aforementioned common current conductor is connected to the electrodes, the risk is amplified, since localized heating of these separate current conductors can occur during charging or discharging. In particular, each electrode in the immediate vicinity of the current conductor is subjected to greater thermomechanical stresses than those further away from the current conductor.

[0014] WO 2017 / 215900 A1 describes a cell in which the electrodes are ribbon-shaped and in the form of windings. Each electrode has a current collector filled with electrode material. Oppositely polarized electrodes are arranged staggered within an electrode separator assembly so that the longitudinal edge of the positive electrode current collector protrudes from the winding on one side and the longitudinal edge of the negative electrode current collector protrudes from the winding on the other side. To electrically contact the current collectors, the cell has at least one contact element that rests on one of the longitudinal edges to form a linear contact section. The contact element is connected to the longitudinal edge by welding along the linear contact section. This allows the current collector, and therefore the associated electrode, to be electrically contacted over its entire length. This significantly reduces the internal resistance within the cell. Consequently, large currents can then be absorbed much better. Summary of the Invention [Problem to be solved by the invention]

[0015] Objectives and Solutions The present invention is based on the object of providing an energy storage element with a prismatic housing. This energy storage element not only has an increased energy density compared to the prior art, but is also characterized by a current distribution that is as homogeneous as possible over the surface and length of its electrodes, while at the same time having excellent properties with regard to its internal resistance and passive heat dissipation capacity. Furthermore, the energy storage element should have improved manufacturability and safety. This object is achieved by an energy storage element having the features of claim 1. Preferred embodiments of the energy storage element are defined in the dependent patent claims. [Means for solving the problem]

[0016] The energy storage element according to the present invention is characterized by a combination of the following features a. to i. a. Contains a plurality of anodes and cathodes. b. Each anode includes an anode current collector. c.Anode current collectors, respectively: a main area filled with a layer of anode material; a free edge strip extending along the edge of the anode current collector that is not filled with negative electrode material. d. Each cathode includes a cathode current collector. e. Each cathode current collector is a main area filled with a layer of cathode material; a free edge strip extending along the edge of the cathode current collector that is not filled with positive electrode material. f. The anode and cathode are stacked to form an assembly in which the anode and cathode are separated by a layer of separator or solid electrolyte. g. The assembly is enclosed in a prismatic housing. h. The free edge strip of the anode current collector projects from one side of the assembly and the free edge strip of the cathode current collector projects from another side of the assembly. i. The energy storage element has at least one metallic contact element connected to the free edge strip of the anode current collector and / or the free edge strip of the cathode current collector by welding or soldering.

[0017] For the sake of explanation, the connection between the metallic contact element of the anode or cathode current collector and the edge strip is a direct connection. In the case of welding, the metallic contact element is directly fused to the free edge strip, while in the case of soldering, at most a thin layer of solder metal is arranged between the metallic contact element and the free edge strip. The direct connection of the contact element to the electrode's current collector ensures excellent heat dissipation properties, as will be discussed further below. It is particularly preferred that the energy storage element according to the invention comprises two metallic contact elements, one of which is connected to the free edge strip of the anode current collector by welding or soldering and the other of which is connected to the free edge strip of the cathode current collector by welding or soldering.

[0018] Preferred Embodiments of the Electrochemical System In principle, the present invention includes energy storage elements, regardless of their electrochemical implementation. However, in a particularly preferred embodiment, the energy storage element according to the invention is designed as a lithium-ion system, i.e., it has electrodes capable of reversibly absorbing and releasing lithium. Therefore, in principle, all known electrode materials for secondary lithium-ion cells can be used for the anode and cathode contained in the energy storage element.

[0019] Preferably, carbon-based particles, such as graphitic carbon or non-graphitic carbon materials capable of intercalating lithium, also in particulate form, can be used as the active material in the negative electrode of the energy storage element according to the present invention. Alternatively, or in addition, lithium titanate (Li4Ti5O 12 ) or a derivative thereof may also be included in the negative electrode, preferably in particulate form. Furthermore, the negative electrode may contain as an active material at least one material from the group including silicon, aluminum, tin, antimony, or a compound or alloy of these materials capable of reversibly depositing and removing lithium, such as silicon oxide, optionally in combination with a carbon-based active material. Tin, aluminum, antimony, and silicon can form intermetallic phases with lithium. The lithium absorption capacity, particularly in the case of silicon, is many times greater than that of graphite or comparable materials. One or more anodes based on metallic lithium or consisting of metallic lithium as mentioned at the beginning may also be used.

[0020] Lithium metal oxide compounds and lithium metal phosphate compounds, such as LiCoO2 and LiFePO4, are suitable active materials for the positive electrode of the energy storage element according to the invention. Furthermore, lithium metal oxide compounds and lithium metal phosphate compounds, such as LiCoO2 and LiFePO4, are particularly well suited. x Mn y Co z Lithium nickel manganese cobalt oxide (NMC) with the formula LiMnO2 (where x+y+z is typically 1), lithium manganese spinel (LMO) with the formula LiMn2O4, or lithium manganese oxide (LiMnO) with the formula LiNi x Co y Al z Lithium nickel cobalt alumina (NCA) with the formula Li 1.11 (Ni 0.40 Mn 0.39 Co 0.1 Al 0.05 ) 0.89Lithium Nickel Manganese Cobalt Alumina (NMCA) with O2, or Li 1+x MO compounds and / or mixtures of said materials can also be used.The active material of the cathode is also preferably used in granular form.

[0021] In addition, the electrodes of the energy storage element according to the present invention preferably contain an electrode binder and / or an additive for increasing electrical conductivity. The active material is preferably embedded in the matrix of the electrode binder, with adjacent particles in the matrix preferably in direct contact with each other. The conductive agent functions to increase the electrical conductivity of the electrode. Common electrode binders are, for example, polyvinylidene fluoride (PVDF), polyacrylate, styrene-butadiene rubber (SBR), or carboxymethyl cellulose-based. Common conductive agents include carbon black, graphite, graphene, carbon nanofibers, and metal powders.

[0022] Preferred embodiments of the separator The energy storage element according to the present invention preferably includes a separator made of a plastic material permeable to the liquid electrolyte. For example, plastic films can be used for this purpose, including nonwoven fabrics, woven fabrics, and other flat structures made of plastic materials that are not only microporous but also permeable to the liquid electrolyte. The prerequisite in each case is that the plastic material used has electrical insulating properties. Suitable plastic materials include polyolefins, polyether ketones, and polyethylene terephthalates. Preferably, separators with a thickness ranging from 5 μm to 50 μm are used.

[0023] When using such a separator, the energy storage element according to the invention preferably comprises an electrolyte, in particular an electrolyte based on at least one lithium salt present dissolved in an organic solvent (e.g., a mixture of organic carbonates or a cyclic ether such as THF or a nitrile), such as lithium hexafluorophosphate (LiPF6) for the case of an energy storage element designed as a lithium-ion system. Other lithium salts that can be used include lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(oxalato)borate (LiBOB).

[0024] Preferred embodiments of the solid electrolyte The use of a solid electrolyte layer is particularly advantageous when a lithium metal-based anode is used. The solid electrolyte can be, for example, a polymer solid electrolyte based on a polymer conductive salt complex that exists in a single phase without a liquid component. The polymer matrix can be, for example, polyacrylic acid (PAA), polyethylene glycol (PEG), or polymethyl methacrylate (PMMA). Lithium conductive salts such as lithium bis(trifluoromethane)sulfonylimide (LiTFSI), lithium hexafluorophosphate (LiPF), and lithium tetrafluoroborate (LiBF) can be dissolved in these.

[0025] When a solid electrolyte is used, it is advantageous if a proportion (e.g., up to 10 percent by weight) of the solid electrolyte, e.g., one of the polymer solid electrolytes having a conductive salt dissolved therein, is also contained in the anode and / or cathode of the energy storage element according to the invention.

[0026] Preferred embodiments of the separator In a configuration with a separator and a liquid electrolyte, the energy storage element according to the present invention preferably has at least one of the following characteristics a. to c., which are described immediately below: a. The separator is a polygonal, preferably rectangular, flat structure made of an electrically insulating plastic substrate, particularly in the form of the aforementioned plastic film having micropores or a nonwoven fabric that is permeable to the liquid electrolyte. b. The separator has a thickness in the range of 5 μm to 50 μm, preferably in the range of 10 μm to 30 μm, and particularly preferably in the range of 7 μm to 12 μm. c. The edges of the separator form the sides of the assembly, from which protrude the free edge strips of the anode and cathode current collectors. The immediately preceding features a to c are preferably implemented together.

[0027] In particularly preferred embodiments, the energy storage element according to the invention has the following features, as will be described immediately below: a. The separator comprises at least one inorganic material, in particular a ceramic material, that enhances resistance to thermal stress.

[0028] This inorganic material protects the separator from shrinkage resulting from localized heating, such as may occur when welding contact elements. The risk of short circuits is therefore significantly reduced. The above information regarding the preferred thickness of the separator preferably also applies to separators comprising at least one inorganic material. In a particularly preferred embodiment of the energy storage element according to the invention, a separator comprising at least one inorganic material for increasing the resistance of the energy storage element is realized in combination with a current collector comprising an edge region with a support material, as further described below.

[0029] In another preferred further development, the separator is characterized by the following feature a, which is mentioned immediately below: a. At least one inorganic material is contained in the separator as a particulate filler.

[0030] In a preferred embodiment, the separator can electrically insulate a plastic film with particulate filler embedded therein. For example, the plastic film has the micropores described above, which allows electrolyte to permeate the plastic film, which is preferred. Preferably, the proportion of particulate filler in the separator is at least 40 wt.%, more preferably at least 60 wt.%, based on the mass of the separator without electrolyte.

[0031] In another preferred further development, the separator is characterized by the following feature a., which is mentioned immediately below. a. The at least one inorganic material is present as a coating on the surface of the separator.

[0032] According to this development, in a preferred embodiment, the separator can be a plastic film, or a nonwoven or woven fabric, or other electrically insulating sheet material coated with a particulate filler. In this case, it is preferable to use a separator with a base thickness in the range of 5 μm to 20 μm, preferably in the range of 7 μm to 12 μm. The total thickness of the separator is obtained from the thickness of the base and the thickness of the coating. In some embodiments, only one side of the separator is coated with an inorganic material. In other possible embodiments, the separator is coated with an inorganic material on both sides.

[0033] The thickness of the coating is preferably in the range of 0.5 μm to 5 μm. This means that in the case of double-sided coating, the total thickness of the separator is preferably in the range of 6 μm to 30 μm, particularly preferably in the range of 8 μm to 22 μm. In the case of single-sided coating, the thickness is preferably in the range of 5.5 μm to 20.5 μm, particularly preferably in the range of 7.5 μm to 17 μm. Where appropriate, it may be preferable for the separator used to contain an inorganic material as filler and the same or a different inorganic material as coating.

[0034] With respect to the inorganic material of the separator(s), in preferred embodiments, the separator is characterized by at least one of the following characteristics a.-e., as set forth immediately below: a. The at least one inorganic material is or comprises an electrically insulating material. b. The at least one inorganic material is or includes at least one material selected from the group consisting of ceramic materials, glass-ceramic materials, and glasses. c. The at least one inorganic material is or includes a lithium ion conducting ceramic material, such as Li5AlO4*Li4SiO4 or LiAlSi2O6. d. The at least one inorganic material is or includes an oxide material, particularly a metal oxide. e. The ceramic or oxide material is aluminum oxide (Al2O3), titanium oxide (TiO2), titanium nitride (TiN), titanium aluminum nitride (TiAlN), silicon oxide, in particular silicon dioxide (SiO2) or titanium carbonitride (TiCN).

[0035] It is particularly preferred that the immediately preceding features a to c, or the immediately preceding features a, b, and d, or the immediately preceding features a, b, and e, are combined with one another. Among the aforementioned materials, aluminum oxide (Al2O3), titanium oxide (TiO2), and silicon dioxide (SiO2) are particularly preferred as coating materials.

[0036] In a further preferred development, the separator is characterized by at least one of the following features a. to c., which are described immediately below: a. The separator comprises at least one inorganic material in only certain areas. b. The separator has an edge strip that includes at least one inorganic material as a coating and / or as a particulate filler. c. The separator has at least one major area that is free of inorganic material. It is particularly advantageous that the immediately preceding features a. to c. are realized in combination with one another.

[0037] It is not necessary for the separator to contain a homogeneously distributed inorganic material or to be uniformly coated with the material everywhere. Rather, it may even be preferable for the separator to be free of inorganic material in certain regions, such as the key regions mentioned above. This region does not need to have as high a thermal resistance as the separator's edges. Additionally, inorganic material, especially in this region, can contribute to an undesirable increase in electrical resistance.

[0038] Preferred Embodiments of the Current Collector The current collector of the electrode of the energy storage element according to the present invention has the function of electrically contacting the electrochemically active components contained in the respective electrode materials over as large an area as possible. Preferably, the current collector is made of metal or is metallized at least on the surface. In the case of electrodes for lithium-ion systems, suitable metals for the anode current collector include, for example, copper or nickel, or other conductive materials, in particular copper and nickel alloys, or metals coated with nickel. Stainless steel is also generally possible. Suitable metals for the cathode current collector include aluminum or other conductive materials, including aluminum alloys.

[0039] Preferably, the anode current collector and / or the cathode current collector are in each case metal foils having a thickness in the range of 4 μm to 30 μm, in particular ribbon-shaped metal foils having a thickness in the range of 4 μm to 30 μm. However, in addition to foils, other substrates can be used as current collectors, such as metallic or metallized nonwoven fabrics, or open-pore metallic foams, or expanded metals. The current collectors are preferably filled on both sides with the respective electrode materials.

[0040] In some particularly preferred embodiments, the energy storage element according to the present invention may be characterized by at least one of the following features a. to c., as described immediately below: a. The main area of ​​the current collector, which is connected to the contact element by welding or soldering, has a plurality of openings. b. The opening in the main area is in particular a round or square hole punched or drilled. c. The current collector, which is connected to the contact element by welding, is perforated in the main area, in particular by drilling circular holes or elongated holes. Preferably, the immediately preceding features a. and b., or a. and c., and particularly preferably the immediately preceding three features a. to c., are realized in combination with one another.

[0041] The multiple apertures reduce the volume and weight of the current collector, allowing more active material to be incorporated into the electrode, dramatically increasing the energy density of electrochemical cells formed from the electrode. Energy density increases in the double-digit percentage range can be achieved in this manner. In some preferred embodiments, the apertures are introduced into the main region by a laser.

[0042] In principle, the geometric shape of the openings is not essential to the invention. What is important is that the mass of the current collector is reduced as a result of the insertion of the openings and that the space for the active material is increased, since the openings can be filled with the active material. When inserting the openings, it can be very advantageous not to make their maximum diameter too large. Preferably, the dimensions of the openings do not exceed twice the thickness of the layer of electrode material on the respective current collector.

[0043] In a particularly preferred embodiment, the energy storage element according to the invention is characterized by the following feature a, which is described immediately below: The openings of the current collector, particularly in the main region, have a diameter in the range of 1 μm to 3000 μm. Within this preferred range, diameters in the range of 10 μm to 2000 μm, preferably 10 μm to 1000 μm, and especially 50 μm to 250 μm are even more preferred.

[0044] Particularly preferably, the energy storage element according to the invention further has at least one of the following characteristics a. and b., which are described immediately below: a. Current collectors connected to contact elements by welding or soldering have a weight per unit area less than the free edge strips of the same current collectors, at least in a portion of each main area. b. Current collectors connected to contact elements by welding or soldering have no or fewer openings per unit area in the free edge strip than in the main area. It is particularly preferred that the immediately preceding features a. and b. are realized in combination with one another.

[0045] The free edge strips of the anode and cathode current collectors define a main area towards the edges to which they extend. In the case of apertured current collectors, the apertures also characterize the main area. In other words, the boundary between the main area and the free edge strip(s) may, in preferred embodiments, correspond to the transition between an area with apertures and an area without apertures. The apertures are preferably distributed substantially uniformly over the entire surface of the main area.

[0046] In further particularly preferred embodiments, the energy storage element according to the invention has at least one of the following characteristics a. to c., as described immediately below: a. The weight per unit area of ​​the current collector in the main area is reduced by 5% to 80% compared to the weight per unit area of ​​the current collector in the free edge strip. b. The current collector has a hole area within the main area ranging from 5% to 80%. c. The current collector shall have a tensile strength of 20N / mm within the main area. 2 ~250N / mm 2 is. It is particularly advantageous that the immediately preceding features a. to c. are realized in combination with one another.

[0047] The area of ​​the hole, often called the free cross section, can be calculated according to ISO 7806-1983. The tensile strength of the current collector in the main area is reduced compared to a current collector without openings. Its calculation can be done according to DIN EN ISO 527-3.

[0048] Particularly preferably, the energy storage element according to the invention has the following characteristic a., which will be described immediately below. a. Both the main area of ​​the anode current collector and the main area of ​​the cathode current collector are characterized by a plurality of openings. The preferred embodiments of the apertured current collectors described above are applicable independently to the anode current collectors and the cathode current collectors.

[0049] The use of perforated or otherwise multi-apertured current collectors has not yet been seriously considered for lithium-ion cells because such current collectors are extremely difficult to electrically contact. As mentioned at the beginning, electrical connection of current collectors is traditionally made via separate current conductors. However, reliably welding these current conductors to perforated current collectors in industrial mass production processes is difficult to achieve without an acceptable failure rate for conventional lithium-ion cells.

[0050] According to the invention, this problem is solved by welding or soldering the free edge strips of the anode and / or cathode current collector to the contact elements, as described above. The concept according to the invention makes it possible to completely dispense with separate current conductors, which allows the use of current collectors with a low material content and with openings. It is particularly advantageous if the free edge strips of the current collectors are free of openings, since in these cases welding can be carried out particularly reliably with an exceptionally low rejection rate. This is particularly true if a support layer or support material, as described below, is provided at the edge of the current collector, and the separator is, if necessary, improved against the above-mentioned thermal loads.

[0051] Support Coating In the free edge strips, the metal of the respective current collector is preferably free of the respective electrode material, and in some preferred embodiments, the metal of the respective current collector is uncoated therein so as to be available for electrical contact, e.g., welding or soldering to a contact element.

[0052] However, in some further embodiments, the metal of the respective current collector in the free edge strip may also be coated, at least in some areas, with a support material different from the electrode material provided on the respective current collector, the support material being intended to stabilize the edge strip and to prevent it from unintentionally bending or melting, in particular when making a welding or soldering connection to the contact element.

[0053] Support materials that can be used in the context of the present invention preferably have at least one of the following additional characteristics a. to e., which are described immediately below. a. The support material is a non-metallic material. b. The support material is an electrically insulating material. c. The non-metallic material is a ceramic material, a glass-ceramic material, or a glass. d. The ceramic material is aluminum oxide (Al2O3), titanium oxide (TiO2), titanium nitride (TiN), titanium aluminum nitride (TiAlN), silicon oxide, in particular silicon dioxide (SiO2), or titanium carbonitride (TiCN). e. The support material is a metal having a higher melting point than the metal of each current collector. According to the invention, it is particularly preferred that the support material is formed in accordance with the immediately preceding characteristic b., and particularly preferably in accordance with the immediately preceding characteristic d.

[0054] The term "non-metallic material" includes, in particular, plastics, glasses, and ceramic materials. The term "electrically insulating material" is to be understood broadly in this context. In principle, it includes any electrically insulating material, in particular also the aforementioned plastics. The term "ceramic material" is to be understood broadly in this context. In particular, it includes carbides, nitrides, oxides, silicides, or mixtures and derivatives of these compounds. The term "glass-ceramic material" particularly refers to a material containing crystalline particles embedded in an amorphous glass phase. The term "glass" basically refers to any inorganic glass that meets the thermal stability criteria defined above and is chemically stable with respect to any electrolyte that may be present in the cell. Particularly preferably, the anode current collector is made of copper or a copper alloy, while the cathode current collector is made of aluminum or an aluminum alloy, and the support material is aluminum oxide or titanium oxide.

[0055] In a particularly preferred embodiment, the energy storage element according to the invention has at least one of the following characteristics a. to c., as described immediately below: a. The free edge strip of the anode current collector and / or the free edge strip of the cathode current collector includes a first sub-region and a second sub-region, the first sub-region being coated with a support material while the second sub-region is uncoated. b. The first sub-region and the second sub-region are each linear or strip-shaped and extend parallel to each other. c. The first sub-region is located between the main region of the anode current collector or the cathode current collector and the second sub-region. It is particularly advantageous that the immediately preceding features a. to c. are realized in combination with one another.

[0056] In an alternative embodiment, it may be preferred that the energy storage element according to the invention is characterized by the following feature a., as set out immediately below. a. The free edge strip of the anode current collector and / or the free edge strip of the cathode current collector is completely coated with the support material. Coating the anode current collector with the support material can be carried out according to different methods, for example by dry coating or by deposition from a dispersion or deposition from the gas phase, optionally using a compatible binder system.

[0057] Particularly Preferred Embodiments of the Electrochemical System In a first, particularly preferred variant of the electrochemical system, the energy storage element according to the invention has the following characteristic a., which will be described immediately below. a. The negative electrode material comprises, as an active material, at least one material selected from the group consisting of silicon, aluminum, tin, antimony, and compounds or alloys of these materials capable of reversibly intercalating and deintercalating lithium, in an amount of 20 wt % to 90 wt %.

[0058] The weights stated herein refer to the dry mass of the negative electrode material, i.e., the weight without electrolyte and not taking into account the weight of the anode current collector.

[0059] Tin, aluminum, antimony and silicon are capable of forming intermetallic phases with lithium, and their capacity to absorb lithium, particularly in the case of silicon, exceeds that of graphite or comparable materials by many times.

[0060] The active materials mentioned can preferably be used in the form of particles, among which silicon is particularly preferred. According to the present invention, a negative electrode containing silicon as active material in a proportion of 20 wt.% to 90 wt.% is particularly preferred.

[0061] Similarly, some compounds of silicon, aluminum, tin, and / or antimony can reversibly deposit and remove lithium. For example, in some preferred embodiments, silicon can be present in the negative electrode in the form of an oxide. In these embodiments, it may be suitable for the negative electrode to contain an amount of silicon oxide ranging from 20 wt % to 90 wt %.

[0062] The design of the energy storage element according to the present invention offers significant advantages. As mentioned at the beginning, when the electrical connection of a cell is made via separate current conductors, the thermomechanical stresses acting on the electrodes during charging and discharging can be greater in the immediate vicinity of the current conductors than at locations further away from the current conductors. This difference is particularly pronounced for negative electrodes containing silicon, aluminum, tin, and / or antimony as active materials. On the other hand, electrically connecting the current collector via the contact element according to the present invention not only enables relatively uniform and efficient heat dissipation from the electrodes, but also distributes the thermomechanical stresses that occur evenly throughout the electrodes during charging and discharging. Surprisingly, this makes it possible to control a very high proportion of silicon, tin, and / or antimony in the negative electrode. Even with such a high proportion, relatively little or no damage occurs during charging and discharging as a result of the thermomechanical stresses. For example, by increasing the proportion of silicon in the anode, the energy density of the energy storage element according to the present invention can be significantly increased.

[0063] Those skilled in the art understand that tin, aluminum, silicon and antimony do not necessarily have to be metals in the purest form.For example, silicon particles (apart from lithium, which is always contained as a function of the state of charge), can also contain other elements, particularly other metals, in trace amounts or in a certain proportion, for example, up to 40% by weight, particularly up to 10% by weight.Therefore, alloys of tin, aluminum, silicon and antimony can also be used.

[0064] In a particularly preferred embodiment of the first particularly preferred variant, the energy storage element according to the invention has at least one of the following characteristics a. and b., which are described immediately below: a. The negative electrode material further comprises, as the negative active material, carbon-based particles capable of reversibly inserting and removing lithium, such as graphitic carbon, particularly mixtures of these carbon-based particles with silicon. b. The carbon-based particles capable of intercalating lithium are present in the electrode material in an amount of 5% to 75% by weight, and in particular in an amount of 15% to 45% by weight.

[0065] For example, carbon-based particles, such as graphitic carbon or non-graphitic carbon materials capable of intercalating lithium, can preferably be used as the active material in the negative electrode, also in particulate form. Alternatively, or additionally, lithium titanate (Li4Ti5O 12 ) or a derivative thereof may also be included in the negative electrode, preferably also in particulate form.

[0066] In a particularly preferred embodiment of the first further particularly preferred variant, the energy storage element according to the invention has at least one of the following characteristics a. to c., which are described immediately below: a. The negative electrode material includes an electrode binder and / or a conductive agent that increases the conductivity of the negative electrode. b. The electrode binder is contained in the negative electrode material at a ratio of 1 wt.% to 15 wt.%, particularly at a ratio of 1 wt.% to 5 wt.%. c. The conductive agent is present in the negative electrode material in a proportion of 0.1 wt.% to 15 wt.%, particularly in a proportion of 1 wt.% to 5 wt.%. It is particularly advantageous that the immediately preceding features a. to c. are realized in combination with one another.

[0067] Again, the active material is preferably embedded in a matrix of the electrode binder, with adjacent particles in the matrix preferably in contact with each other.

[0068] Suitable electrode binders are again, for example, those based on polyvinylidene fluoride (PVDF), polyacrylate, styrene-butadiene rubber (SBR) or carboxymethyl cellulose. Suitable conductive agents include carbon black, graphite, graphene, carbon nanofibers, and metal powders.

[0069] In the context of the first, particularly preferred variant, it is particularly preferred that the positive electrode material comprises a PVDF binder and the negative electrode material comprises a polyacrylate binder, in particular lithium polyacrylate.

[0070] In a first, particularly preferred variant, lithium metal oxides and lithium metal phosphate compounds, such as LiCoO2 and LiFePO4, are suitable active materials for the positive electrode. x Mn y Co z Lithium nickel manganese cobalt oxide (NMC) with the formula LiMnO2 (where x+y+z is typically 1), lithium manganese spinel (LMO) with the formula LiMn2O4, or lithium manganese oxide (LiMnO) with the formula LiNi x Co y Al z Lithium nickel cobalt alumina (NCA) having the formula Li 1.11 (Ni 0.40 Mn 0.39 Co 0.16 Al 0.05 ) 0.89Lithium Nickel Manganese Cobalt Alumina (NMCA) with O2, or Li 1+x MO compounds and / or mixtures of said materials can also be used.

[0071] The high silicon content in the anode of the energy storage element according to the invention requires a correspondingly large cathode capacity in order to be able to achieve good cell balance, and therefore NMC, NCA or NMCA are particularly suitable.

[0072] In a first particularly preferred embodiment, the positive electrode is characterized by at least one of the following features a. to e., which are described immediately below: a. The positive electrode material comprises as the active material at least one metal oxide compound capable of reversible lithium incorporation and removal, preferably one of the compounds listed above, in particular NMC, NCA or NMCA. b. The at least one oxide compound is present in the electrode material in a proportion of 50% by weight to 99% by weight, in particular in a proportion of 80% by weight to 99% by weight. c. The positive electrode material also preferably includes an electrode binder and / or a conductive agent. d. The electrode binder is present in the positive electrode material in a proportion of 0.5 wt.% to 15 wt.%, particularly preferably in a proportion of 1 wt.% to 10 wt.%, and in particular in a proportion of 1 wt.% to 2 wt.%. e. The conductive agent is contained in the positive electrode material in an amount of 0.1 wt % to 15 wt %. It is particularly preferred that the immediately preceding features a. to e. be realized in combination with one another. In both the positive and negative electrodes, it is preferred that the percentages of the individual components contained in the electrode material total 100% by weight.

[0073] High-capacity cathodes can reversibly store lithium in the range of 200–250 mAh / g, while the theoretical capacity of silicon is approximately 3500 mAh / g. This leads to relatively thick cathodes with high surface charge and very thin anodes with low surface charge. Because materials such as silicon react strongly to even small voltage changes due to their very high capacitance, the anode current collector must be coated as uniformly as possible. Even small differences in current collector loading and / or electrode material densification can result in large local deviations in electrode balance and / or stability.

[0074] For this reason, in a preferred embodiment of the first, particularly preferred variant, the negative electrode is characterized by the following feature a., which is set out immediately below: a. The weight per unit area of ​​the negative electrode is at least 10 cm 2 The maximum deviation per unit area is 2% from the average value. The mean value is the sum of at least 10 measurements divided by the number of measurements taken.

[0075] Furthermore, the energy storage element according to the present invention preferably comprises an electrolyte based on at least one lithium salt, such as, for example, lithium hexafluorophosphate (LiPF), dissolved in an organic solvent (e.g., a mixture of organic carbonates or a cyclic ether such as THF or a nitrile). Other lithium salts that can be used include lithium tetrafluoroborate (LiBF), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(oxalato)borate (LiBOB).

[0076] In a particularly preferred embodiment of the first particularly preferred variant, the energy storage element according to the invention has at least one of the following characteristics a. to d., which are described immediately below: a. The energy storage element includes an electrolyte comprising a mixture of tetrahydrofuran (THF) and 2-methyltetrahydrofuran (mTHF). b. The volume ratio of THF to mTHF in the mixture is in the range of 2:1 to 1:2, and most preferably 1:1. c. The energy storage element includes an electrolyte including LiPF6 as a conductive salt. d. The conductive salt is contained in the electrolyte at a ratio of 1 to 2.5M, particularly at a ratio of 1 to 1.5M. In a first, particularly preferred variant, the electrolyte is characterized by all of the above characteristics a. to d.

[0077] In an alternative, particularly preferred embodiment, the energy storage element according to the invention in a first, particularly preferred variant is characterized by at least one of the following features a. to e., as set out immediately below: a. The energy storage element includes an electrolyte comprising a mixture of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC). b. The volume ratio of FEC to EMC in the mixture is in the range of 1:7 to 5:7, and particularly preferably 3:7. c. The energy storage element includes an electrolyte including LiPF6 as a conductive salt. d. The conductive salt is present in the electrolyte at a concentration of 1.0 to 2.0 M, particularly 1.5 M. e. The electrolyte contains vinylene carbonate (VC), particularly in a proportion of 1-3% by weight. Particularly preferably, the electrolyte is characterized by all of the above characteristics a. to e.

[0078] To enhance cycling stability, the ratio of anode capacitance to cathode capacitance is preferably balanced so as not to fully utilize the silicon's potential capacitance.

[0079] In a first, particularly preferred variant, the energy storage element according to the invention has the following characteristics, which are described immediately below: The capacitance of the anode relative to the capacitance of the cathode of the energy storage element of the present invention is balanced so that only 700-1500 mAh per gram of negative electrode material is reversibly used during operation. This measure allows for reduced volumetric changes.

[0080] Other Particularly Preferred Embodiments of the Electrochemical System In a second, particularly preferred variant of the electrochemical system, the energy storage element according to the invention is particularly characterized by the following additional feature a., which is described immediately below. a. The negative electrode material layer contains metallic lithium.

[0081] High-capacity cathodes can reversibly store lithium in the range of 200–250 mAh / g, while the theoretical capacity of metallic lithium is approximately 3842 mAh / g. This allows for the production of cells with very thin anodes. However, a relatively high surface charge is required on the cathode side. Overall, however, the energy density can be significantly increased.

[0082] In some preferred embodiments of the second, particularly preferred variant of the electrochemical system, the anode may be present as a thin layer of metallic lithium, which may be deposited on the anode current collector from the gas phase, for example by means of a CVD or PVD method (CVD = chemical vapor deposition, PVD = physical vapor deposition).

[0083] However, the energy storage element according to the invention in a second, particularly preferred variant has at least one of the following two additional characteristics a. and b., which are described immediately below. a. The layer of negative electrode material comprises a conductive matrix having a porous, open pore structure. b. Metallic lithium is embedded in the pores of the matrix. Particularly preferably, the immediately preceding additional features a. and b. are realized in combination.

[0084] Optionally, the anode can include at least one additional material in addition to metallic lithium, for example, at least one metal alloyed with the lithium, which, if desired, is also embedded in the pores of the matrix.

[0085] One of the problems that has hindered the marketability of cells with metallic lithium anodes is that such anodes are completely degraded during full discharge. Thus, the capacity of the anode can approach zero during discharge. As in the case of silicon as the active material, this can lead to large volume changes in the cell, which are repeated in the opposite direction during charging. This problem is particularly serious when layered anodes and cathodes are stacked in alternating order, as in the case of the energy storage element of the present invention. In this case, the respective volume changes are summed up.

[0086] Another problem that can occur in cells with metallic lithium anodes is that during charging, metallic lithium can accumulate unevenly on the anode side, and in extreme cases, even lead to the formation of dendrites.

[0087] The conductive matrix with an open pore structure ensures that volume changes occurring on the anode side during charge and discharge processes are minimized. Starting from a charged state in which lithium occupies at least a majority, and if necessary, the entire pores of the matrix, lithium is consumed within the anode during discharge. However, unlike prior art cells with metallic lithium anodes, virtually no volume is lost in the anode, since the volume is determined primarily by the matrix. During charging, lithium can be uniformly re-deposited in the anode due to the conductivity of the matrix. Non-uniform lithium deposition and the associated local volume increase, and even dendrite formation, can thus be avoided. Additionally, in combination with connecting the free edge strips of the anode current collector and / or the free edge strips of the cathode current collector to the contact elements, voltage and temperature gradients are minimized.

[0088] The open pore structure of the matrix is ​​very important. As is commonly known, an open pore structure is a structure having a plurality of pores interconnected by channels or openings in the pore walls. As a result, an open pore structure generally has a large internal surface area.

[0089] In a preferred further development, the matrix of a second, particularly preferred variant of the electrochemical system has at least one of the following two additional features a. and b., which are described immediately below. a. The matrix has a porosity in the range of 40-95%. b. The pores in the matrix are characterized by an average diameter in the range of 2 to 50 μm. Particularly preferably, the immediately preceding additional features a. and b. are realized in combination.

[0090] Calculating the porosity (ratio of pore volume to the total volume of the matrix) and pore size distribution is no longer a problem these days. There are numerous measuring instruments that perform the corresponding calculations according to standardized methods. The above values ​​refer to calculations according to the ISO 15901-1 and DIN 66133 standards.

[0091] In a possible further development of the immediately preceding feature a, the matrix preferably has a porosity in the range of 50% to 95%, particularly preferably 70% to 95%, in particular 80% to 95%. In a possible further development of the immediately preceding feature b, the pores in the matrix preferably have an average diameter in the range of 7.5 to 150 μm, particularly preferably 9 to 130 μm, in particular 10 to 120 μm.

[0092] The pores in the matrix are particularly preferably connected by channels having an average diameter in the range of 0.5 μm to 50 μm, more preferably in the range of 1 to 40 μm, especially in the range of 1 to 25 μm, most preferably in the range of 1 to 10 μm. Ideally, the matrix is ​​made of a material that does not chemically change during charging and discharging of the cell.

[0093] In a preferred further development, the matrix in a second, particularly preferred variant of the electrochemical system is characterized by at least one of the following four additional features a. to d., which are described immediately below: a. The matrix comprises carbon formed by carbonization of organic compounds. b. The matrix contains carbon in a proportion ranging from 50 to 100% by weight. c. In addition to carbon, the matrix contains at least one filler material that has a higher or lower electrical conductivity than carbon. d. The filler is at least one member selected from the group consisting of carbon black, CNT, graphene, and metal particles. The immediately preceding additional features a. and b., and particularly preferably the immediately preceding additional features a. to d., are preferably realized in combination.

[0094] Suitable variations of carbonizable organic compounds and also carbonization methods are described in EP 2 669 260 A1, WO 2017 / 086609 A1 and U.S. Pat. No. 5,510,212 A, the contents of which are incorporated herein by reference in their entirety. It is highly preferred that the porous conductive matrix with an open pore structure is produced from a porous organic compound, in particular a polymer with a porous structure.

[0095] The formation of this porous organic compound, particularly a polymer with a porous structure, can be achieved, for example, by polymerizing the monomer phase of a monomer-in-water emulsion, for example, by ring-opening metathesis polymerization (ROMP) of diene compounds readily available for this purpose, according to EP 2669260 A1. During polymerization, water droplets are trapped. After subsequent water removal, voids remain in their place. The resulting polymer matrix with these holes can be carbonized in a subsequent step, which may also require an intermediate step such as an oxidation treatment.

[0096] Carbonization in this context refers to the conversion of organic compounds to nearly pure carbon. Such conversion is generally carried out at very high temperatures and in the absence of oxygen. For example, polymers can be heated to temperatures ranging from 550°C to 2500°C, preferably in an oxygen-free atmosphere, for carbonization.

[0097] The properties of the matrix, in particular its pore size, can also be adjusted, in particular according to EP 2 669 260 A1. For this purpose, different amounts of surfactants can be added to the monomer-in-water emulsion. The volume fraction of surfactant preferably varies in the range of 0.1% to 8% (based on the amount of polymerizable monomer in the emulsion).

[0098] The fillers described in Feature c. can be used to selectively increase or decrease the conductivity of the matrix. To introduce the fillers, for example, the fillers can be added to the monomer-in-water emulsion described above. The matrix preferably contains at least one filler in a proportion ranging from 0.1 to 30% by weight.

[0099] In a preferred further development, the energy storage element according to the invention in a second, particularly preferred variant is characterized by the following additional feature a., which is mentioned immediately below. a. The layer of negative electrode material on the anode current collector has a thickness in the range of 5 to 100 μm.

[0100] Metallic lithium can be introduced into the pores of the matrix, for example, by electrochemical deposition. For this purpose, the matrix can be contacted with a lithium salt solution and connected to the negative pole of a DC voltage source. Alternatively, cathode materials containing lithium ions, such as NMC materials or LiMoO3, or Li3N, can be used on the cathode side. Electrochemical deposition of metallic lithium in the pores of the matrix is ​​then carried out during the first charge. Another possibility is to deposit lithium by CVD or PVD.

[0101] For the positive electrode, lithium metal oxide compounds and lithium metal phosphate compounds, such as LiCoO2 and LiFePO4, are suitable as active materials in a second, particularly preferred variant of the electrochemical system. In particular, derivatives of LiFePO4 in which Fe is partially replaced by Co, Ni or Mn are also of interest. Also well suited are, in particular, compounds of the formula LiNi x Mn y Co z Lithium nickel manganese cobalt oxide (NMC) with the formula LiMnO2 (where x+y+z is typically 1), lithium manganese spinel (LMO) with the formula LiMn2O4, or lithium manganese oxide (LiMnO) with the formula LiNi x Co y Al z Lithium nickel cobalt alumina (NCA) with the formula Li 1.11 (Ni 0.40 Mn 0.39 Co 0.16 Al 0.05 ) 0.89 Lithium Nickel Manganese Cobalt Alumina (NMCA) with O2, or Li 1+x MO compounds and / or mixtures of the above materials can also be used.The cathode active materials mentioned are preferably used in granular form.

[0102] In a particularly preferred embodiment of the second, particularly preferred variant, the cathode of the energy storage element according to the invention has correspondingly at least one of the following additional features a. to e., which are described immediately below: a. The positive electrode material comprises as an active material at least one metal oxide compound capable of reversible lithium insertion and removal, preferably a cobalt oxide and / or a manganese compound, particularly preferably NMC, NCA or NMCA. b. At least one metal oxide compound capable of reversible lithium incorporation and desorption is present in the electrode material in an amount of 80 wt% to 99 wt%. c. The positive electrode material includes an electrode binder and / or a conductive agent that increases the conductivity of the positive electrode. d. The electrode binder is present in the positive electrode material in an amount of 0.5% to 5% by weight, preferably 0.5% to 15% by weight. e. The conductive agent is present in the positive electrode material in an amount of 0.1% to 15% by weight, preferably 0.5% to 3.5% by weight. Preferably, the immediately preceding additional features a. to e. are implemented in combination.

[0103] Again, the cathode active material is preferably embedded in a matrix of electrode binder, with adjacent particles in the matrix preferably in direct contact with each other. Suitable electrode binders include, for example, polyvinylidene fluoride (PVDF), polyacrylate, styrene-butadiene rubber (SBR), or carboxymethyl cellulose-based binders. Suitable conductive agents include carbon black, graphite, graphene, carbon nanofibers, and metal powders.

[0104] In another particularly preferred embodiment of the second, particularly preferred variant, the energy storage element according to the invention has at least one of the following additional features a. and b., which are described immediately below: a. The layer of positive electrode material comprises a conductive matrix having a porous, open pore structure. b. Sulfur is incorporated into this matrix. Preferably, the immediately preceding additional features a. and b. are implemented in combination.

[0105] Therefore, in a preferred embodiment of the second, particularly preferred variant, the cathode is a cathode containing sulfur as an active material. The energy storage element according to the invention can therefore comprise a lithium-sulfur cell. For example, the cathode can comprise a mixture of sulfur and an additive that increases electrical conductivity, such as an additive from the group including graphite, carbon black, CNT, and graphene. Alternatively, the cathode can comprise sulfur in a chemically modified form, for example, as a polysulfide.

[0106] In a second, particularly preferred variant, the energy storage element according to the invention preferably comprises a separator made of at least one electrically insulating plastic film permeable to the liquid electrolyte, in particular a plastic film with appropriately dimensioned pores. The foil can be made of, for example, polyolefin or polyetherketone. Nonwovens and woven fabrics made of plastic materials or other electrically insulating sheet structures can also be used as separators within the scope of the second, particularly preferred variant. Separators with a thickness in the range of 5 μm to 50 μm are preferably used.

[0107] As an alternative to the combination of separator and liquid electrolyte, the cell can also have a solid electrolyte, such as the solid electrolyte already specified above, instead of the separator according to the second, particularly preferred variant. If the cathode has sulfur as the active material, the separator can have a protective layer that protects the anode from the electrolyte and any lithium sulfide dissolved in the electrolyte. This protective layer can be applied, for example, to the cathode side of the separator.

[0108] In a second, particularly preferred variant, the energy storage element according to the present invention preferably comprises, in addition to a separator composed of at least one electrically insulating plastic film, a liquid electrolyte composed of a solvent or a mixture of solvents and a lithium-ion-containing conductive salt, with which the separator is impregnated. Suitable conductive salts include LiTFSI, LiPF6, or LiBF4. Suitable solvents include organic carbonates, in particular ethylene carbonate (EC), propylene carbonate (PC), 1,2-dimethoxyethane (DME), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC), and mixtures thereof. When the cathode contains sulfur as the active material, for example, a mixture of dioxolane (DOL) and DME can be used as the solvent. In addition, the electrolyte may contain a passivating additive, such as lithium nitrate (LiNO3).

[0109] In a first, particularly preferred further development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following four additional characteristics a. to d., which are described immediately below: a. The electrolyte comprises a mixture of tetrahydrofuran (THF) and 2-methyltetrahydrofuran (mTHF). b. The volume ratio of THF to mTHF in the mixture ranges from 2:1 to 1:2, most preferably 1:1. c. The electrolyte contains lithium hexafluorophosphate (LiPF6) as a conductive salt. d. The conductive salt is present in the electrolyte in a proportion of 1.5 to 2.5M, especially 2M. Particularly preferably, the four immediately preceding features a. to d. are realized in combination with one another.

[0110] In a second, particularly preferred further development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following six additional characteristics a. to f., which are described immediately below: a. The electrolyte comprises a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). b. The volume ratio of EC to DMC in the mixture ranges from 1:7 to 5:7, and is particularly preferably 3:7. c. The electrolyte contains LiPF6 as a conductive salt. d. The conductive salt is present in the electrolyte at a concentration of 1.0 to 2.0 M, particularly 1.2 to 1.5 M. e. The electrolyte contains vinylene carbonate, particularly in a proportion of 1 to 3% by weight. f. The electrolyte contains ethylene sulfate (DTD), particularly in a proportion of 0.5-2% by weight. Particularly preferably, the six immediately preceding features a. to f. are realized in combination with one another.

[0111] In a third, particularly preferred development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following six additional characteristics a. to f., which are described immediately below: a. The electrolyte comprises a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl acetate (MA). b. The volume fractions of EC and MA in the mixture range from 20% to 40% by volume, respectively, and the volume fraction of DMC in the mixture ranges from 30% to 50% by volume. c. The electrolyte contains LiPF6 as a conductive salt. d. The conductive salt is present in the electrolyte at a concentration of 1.0 to 2.0 M, particularly 1.2 to 1.5 M. e. The electrolyte contains vinylene carbonate, particularly in a proportion of 1 to 3% by weight. f. The electrolyte contains ethylene sulfate (DTD), particularly in a proportion of 0.5-2% by weight. Particularly preferably, the six immediately preceding features a. to f. are realized in combination with one another.

[0112] In a fourth, particularly preferred further development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following four additional characteristics a. to d., which are described immediately below: a. The electrolyte comprises a mixture of 1,3-dioxolane (DOL) and dimethoxyethane (DME). b. The volume ratio of DOL to DME in the mixture ranges from 2:1 to 1:2, with 1:1 being particularly preferred. c. The electrolyte contains lithium bis(trifluoromethane)sulfonylimide (LiTFSI) as the conductive salt. d. The conductive salt is present in the electrolyte at a concentration of 0.5 to 2.0 M, particularly 1 M. Particularly preferably, the four immediately preceding features a. to d. are realized in combination with one another.

[0113] In a fifth, particularly preferred further development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following four additional characteristics a. to d., which are described immediately below: a. The electrolyte comprises at least one solvent selected from the group consisting of acetonitrile (AN), propylene carbonate (PC), tetrahydrofuran (THF), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), vinyl carbonate (VC), and fluoroethylene carbonate (FEC). b. Dissolved in the electrolyte is at least one compound selected from the group consisting of fluoromethane (FM), difluoromethane (DFM), fluoroethane (FE), 1,1-difluoroethane (1,1-DFE), 1,1,1,2-tetrafluoroethane (1,1,1,2-TFE), and 2-fluoropropane (2-FP). c. The electrolyte contains lithium bis(trifluoromethane)sulfonylimide (LiTFSI) as the conductive salt. d. The conductive salt is present in the electrolyte at a concentration of 0.5 to 2.0 M, especially 1.2 M. Particularly preferably, the four immediately preceding features a. to d. are realized in combination with one another.

[0114] In a sixth, particularly preferred further development of the second, particularly preferred variant, the energy storage element according to the invention has, with respect to the electrolyte, at least one of the following three additional characteristics a. to c., which are described immediately below: a. The electrolyte comprises at least one solvent selected from the group consisting of propylene carbonate (PC), dimethoxyethane (DME), acetonitrile (AN), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), sulfolane (SL), and ethyl acetate (EA). b. The electrolyte comprises a conductive salt in an amount of 2.5 to 6.0 molar. c. The conductive salt is LiTFSI. Particularly preferably, the three immediately preceding features a to c are realized in combination with one another.

[0115] Favorable structural characteristics of the electrodes and assemblies. The assembly of the energy storage element according to the invention is preferably formed of 2 to 1000 stacked electrodes, particularly preferably 10 to 500 stacked electrodes, and in particular 20 to 500 stacked electrodes. Within the assembly, the electrodes can form cells in the order "anode / separator / cathode" or "anode / solid electrolyte / cathode," with the separator or solid electrolyte spatially separating the oppositely polarized electrodes. Within the assembly, electrodes with the same polarity are preferably identical, particularly with respect to their capacitance.

[0116] Preferably, the energy storage element according to the invention has at least one of the following characteristics a. and b., as described immediately below: a. The electrodes are polygonal in shape; they are preferably rectangular in perimeter. b. The assembly has a prismatic shape. Particularly preferably, the two immediately preceding features a. and b. are realized in combination with each other. Particularly preferably, the electrodes are rectangular, for example, square. In some embodiments, a hexagonal shape is also particularly suitable. Correspondingly, the assembly of stacked rectangular electrodes preferably has a cuboid, in particular a cubic, geometric shape.

[0117] Thus, the assembly generally includes at least six sides. The sides from which the free edge strips of the anode current collector and the cathode current collector protrude can be opposing sides of the assembly or adjacent sides of the assembly. The electrodes preferably have a thickness in the range of 1 μm to 200 μm. In some embodiments, the anode is much thinner than the cathode, particularly when the anode and cathode are based on metallic lithium or include metallic silicon portions.

[0118] When the electrodes are polygonal, they preferably have a side length ranging from 0.5 cm to 200 cm. For rectangular electrodes, a side length ranging from 0.5 cm to 200 cm is also particularly suitable. The electrodes and the separator or solid electrolyte are preferably formed as flat, planar layers. Preferably, the electrodes stacked in the assembly each include two flat surfaces separated from each other by multiple edges, e.g., in the case of rectangular electrodes, by two longitudinal edges and two lateral edges. Apart from the terminal electrode of the assembly, in which only one of the flat surfaces can indirectly contact the adjacent electrode, each flat surface of the electrode contacts the adjacent electrode in the assembly via a separator or solid electrolyte layer, and these adjacent electrodes have opposite polarities. The flat surfaces in contact via the separator or solid electrolyte layer overlap in an overlap region, which is defined by the fact that within the overlap region, a line perpendicular to one of the flat surfaces also intersects the other flat surface.

[0119] If the stacked electrodes in the assembly are identical in size and not staggered, the size of the overlapping area corresponds exactly to the area of ​​the flat surface, preferably greater than 90%, more preferably greater than 95% of the area of ​​the flat surface.

[0120] The separators included in the assembly are preferably somewhat larger in size than the electrodes they separate. Preferably, the sides of the composite are formed by the edges of each separator, including the sides from which the free edge strips of the anode current collector and the cathode current collector protrude. The same applies if the assembly includes a layer of solid electrolyte instead of a separator.

[0121] The anodes and cathodes may be shaped and / or arranged relative to one another in an appropriate manner within the assembly to ensure that the free edge strips of the anode current collectors of the stacked electrodes protrude from one side of the assembly and the free edge strips of the cathode current collectors protrude from another side of the assembly. For example, The edge strip must have an appropriate width, and / or The anodes and cathodes, and optionally also the separators, can be arranged offset relative to one another within the assembly.

[0122] Within the assembly, the electrodes are preferably arranged so that the free edge strips of the cathode current collectors all protrude from one of the sides of the assembly and the free edge strips of the anode current collectors all protrude from another of the sides of the assembly. To this end, the electrodes can also be arranged staggered relative to one another within the stack.

[0123] It is particularly preferred that the edges of the anode and / or cathode current collector protrude from the side surfaces of the assembly by no more than 5000 μm, preferably no more than 3500 μm. Particularly preferably, the edges of the anode current collector protrude from one of the side surfaces of the assembly by no more than 2500 μm, particularly preferably no more than 1500 μm. Particularly preferably, the edges of the cathode current collector protrude from another side surface of the assembly by no more than 3500 μm, particularly preferably no more than 2500 μm.

[0124] The numbers on the protrusions of the anode and / or cathode current collectors refer to the free protrusions before their sides come into contact with the contact elements. When welding or soldering the contact elements, deformation of the edges of the current collectors may occur.

[0125] The smaller the selected free protrusion, the larger the main area of ​​the current collector that is covered with electrode material can be made, which can positively contribute to the energy density of the energy storage element according to the invention.

[0126] A particular advantage of the energy storage element according to the invention is that it is not only possible to provide the energy storage element with a particularly high specific energy density, but also with particularly good heat dissipation properties, as will be explained in more detail below.

[0127] Favourable characteristics of the contact element The concept of welding the edge of a current collector with contact elements is already known from WO 2017 / 215900 A1 or JP 2004-119330 A, but only in relation to cylindrical round cells. The use of contact elements allows for a particularly high current-carrying capacity and a low internal resistance. Therefore, reference is made in full to the contents of WO 2017 / 215900 A1 and JP 2004-119330 A for suitable methods for electrically connecting contact elements to the edge of a current collector.

[0128] Particularly preferably, the energy storage element according to the invention comprises two contact elements, one of which is in direct contact with the free edge of the anode current collector and the other of which is in direct contact with the free edge of the cathode current collector, the contact elements and the edges in contact with the contact elements being connected by welding or soldering, respectively.

[0129] In the manufacture of conventional electrode stacks consisting of several cells, care is taken to ensure that the lightning arresters connected to current collectors of opposite polarity do not protrude from each other to avoid the risk of short circuits.In accordance with the present invention, the free edge strip of the anode current collector protrudes from one side of the assembly and the free edge strip of the cathode current collector protrudes from another side of the assembly, so that in the energy storage element according to the present invention there is no risk of short circuits resulting from direct contact between oppositely polarized current collectors.

[0130] The contact element serves as a central conductor for the current drawn from the electrodes during operation of the energy storage element. Ideally, the free edge strips of the anode current collector and the cathode current collector are connected to the contact element along their entire length. Such electrical contact significantly reduces the internal resistance within the energy storage element according to the invention. The described arrangement is therefore very good at absorbing large currents. Minimizing the internal resistance reduces heat losses at high currents. In addition, the dissipation of thermal energy from the assembly is favorable. Therefore, under heavy loads, heating is uniformly distributed rather than localized.

[0131] In some preferred embodiments, the energy storage element according to the present invention has at least one of the following characteristics a. and b., as described immediately below: a. A metal sheet having a thickness in the range of 50 μm to 600 μm, preferably 150 to 350 μm, is used as the contact element. b. The contact elements, in particular the metal sheets, consist of alloys or non-alloys of aluminum, titanium, nickel or copper, or of stainless steel (for example 1.4303 or 1.4304 grade), or of nickel-plated steel. Preferably, the immediately preceding features a. and b. are implemented in combination with each other.

[0132] The shape and dimensions of the contact elements, in particular the metal sheets, are preferably adapted to the shape and dimensions of the side of the assembly from which the free edge strip of the current collector is made. In a preferred embodiment, the contact elements are rectangular in shape. They can therefore also be easily integrated into a housing that has a prismatic basic shape.

[0133] In some embodiments, contact elements can be used, in particular metal sheets with at least one slot and / or at least one perforation, which have the function of counteracting deformation of the contact element during the creation of a welded or soldered connection to the free edge strip of the current collector. The contact element can also have an embossment intended to improve material contact at the connection point.

[0134] In a particularly preferred embodiment, both the anode current collector and the contact element welded to the anode current collector, in particular the metal sheet welded or soldered to the current collector, consist of the same material, which is particularly preferably selected from the group comprising copper, nickel, titanium, nickel-plated steel and stainless steel.

[0135] In a further particularly preferred embodiment, both the cathode current collector and the contact elements welded to the cathode current collector, in particular the metal sheets welded or soldered to the cathode current collector, are made of the same material. This is particularly preferably selected from the group comprising aluminum, titanium alloys or non-alloys, and stainless steel (e.g., of 1.4404 standard). The free edge strip of the current collector protruding from the assembly is preferably in direct contact with the respective contact element along its length. This preferably results in a linear contact section between the contact element and the free edge strip.

[0136] To this end, in a preferred further development, the energy storage element according to the invention has at least one of the following characteristics a. to c., which are described immediately below: a. The free edge strip of the anode current collector is preferably in direct contact with a metallic contact element, in particular a metal sheet, along its length and is connected to this contact element, in particular this metal sheet, by welding or soldering, so that there is a linear contact section between the edge strip and the metallic contact element, in particular the metal sheet. b. The free edge strip of the cathode current collector is preferably in direct contact along its length with a metallic contact element, in particular a metal sheet, and is connected to this contact element, in particular a metal sheet, by welding or soldering, so that there is a linear contact section between the edge strip and the metallic contact element, in particular a metal sheet. c. The free edge strip of the anode current collector and / or the free edge strip of the cathode current collector each include one or more sections, each section being continuously connected over its entire length to a respective contact element, in particular a respective metal sheet, by a welded seam or soldering. The immediately preceding features a. and b. can be realized both independently of each other and in combination. Preferably, features a. and b. are in each case implemented in combination with the immediately preceding feature c.

[0137] In particularly preferred embodiments, the energy storage element according to the invention is characterized by at least one of the following features: a. The energy storage element includes at least one contact element having an L-shaped profile. b. The energy storage element includes at least one contact element having a U-shaped profile. c. The contact element has an angled fastening extension. Preferably, the immediately preceding features a. and c., or b. and c., are combined.

[0138] When using contact elements with an L-shaped profile, the protruding edge strips of the respective current collectors can be contacted on two sides of the assembly, and for this purpose it is of course necessary in the first place that the electrodes of the assembly comprise two edges at which the current collectors have a free edge area available for welding or soldering.

[0139] In the case of U-profile contact elements, the contact elements are generally arranged so that contact of the protruding edges of the respective current collectors occurs on three sides of the assembly. Angled fastening extensions, if provided, are primarily intended to secure the contact elements to the housing of the energy storage element, provided that the contact elements themselves are not part of the housing. Furthermore, the fastening extensions can also be part of an L- or U-profile and can also be used, for example, to attach pole studs.

[0140] The more sides of the assembly that have contact elements provided on them, the better the heat dissipation characteristics of the energy storage element according to the present invention. In some preferred embodiments, two contact elements, each having an L-shaped profile, are provided, one of the contact elements being provided for electrically contacting the anode of the assembly and the other contact element being provided for electrically contacting the cathode of the assembly.

[0141] In a preferred embodiment of the energy storage element according to the invention, one of the following features can be implemented: a. The walls of the prismatic housing serve as contact elements. b. The contact element is electrically connected to the housing.

[0142] The realization of the immediately preceding feature a. can be particularly advantageous. In the case of separate contact elements, an additional electrical connection must be made to the housing or to the poles of the pole bushing insulated from the housing, but this is not necessary if the free edge strip of the current collector is directly connected to the housing. On the one hand, stacked electrodes in an assembly can further enhance heat removal. On the other hand, the separate surge arrester is eliminated, and more internal space is available in the housing for the active material, which can be used to increase the capacity.

[0143] In principle, the immediately preceding features a. and b. can be combined with one another. For example, the energy storage element can include a separate contact element welded or soldered to the free edge strip of the cathode current collector, while the free edge strip of the anode current collector is welded or soldered directly to the wall of the housing. Preferred embodiments of the housing, in particular the wall of the housing acting as the contact element, are also described below.

[0144] In further preferred embodiments of the energy storage element according to the invention, the following features can be implemented: a. The housing has at least one pole bushing, which is in contact with the contact element.

[0145] When all current collectors of one polarity are electrically connected to the housing and all current collectors of the opposite polarity are electrically connected to the contact elements, the contact elements can be connected to the conductors of the pole bushing, for example, pole studs or pole pins extending from the housing. In this case, an electrical insulator is preferably provided to prevent electrical contact between the housing and the conductors of the pole bushing. The electrical insulator can be, for example, a glass or ceramic material, or a plastic. In other embodiments, the contact elements can be welded directly to the housing.

[0146] Preferred Embodiments of the Housing The prismatic housing of the energy storage element according to the invention preferably encloses the assembly in a gas- and / or liquid-tight manner and is preferably formed from two or more metallic housing parts, as described, for example, in EP 3117471 B1, which may be connected by welding, for example.

[0147] Preferably, the housing comprises not only several rectangular side walls but also a polygonal, in particular rectangular, bottom part and a polygonal, in particular rectangular, top part, which in particular can serve as contact elements, preferably as contact plates.

[0148] In a first, particularly preferred variant, the housing of the energy storage element according to the invention has at least one, particularly preferably a combination of two, of the following features a. and b., which are described immediately below: a. The housing includes a first housing part having a bottom and a plurality of side walls and an opening, and a second housing part closing the opening. b. The contact element, in particular the contact plate, is the bottom of the first housing part. Thus, in this embodiment, either the free edge strip of the anode current collector or the free edge strip of the cathode current collector is joined to the bottom of the first housing part by welding or soldering.

[0149] In a second, particularly preferred variant, the housing of the energy storage element according to the invention has at least one, particularly preferably a combination of two, of the following features a. and b., which are described immediately below: a. The housing includes a first housing part having a bottom and a plurality of side walls and an opening, and a second housing part closing the opening. b. The second housing part is a contact element. Thus, in this embodiment, either the free edge strip of the anode current collector or the free edge strip of the cathode current collector is connected to the second housing part by welding or soldering.

[0150] In either variant, the first housing part preferably has a rectangular cross section, and the second housing part and the bottom of the first housing part are preferably rectangular. Both the first housing part and the second housing part are preferably made of an electrically conductive material, in particular a metallic material. The housing parts can be made, for example, of nickel-plated steel or of an aluminum alloy or non-alloy.

[0151] In preferred developments of the first and second variants, the energy storage element according to the invention has the following characteristics a. to e., which are described immediately below: a. The free edge strip of the anode current collector or the free edge strip of the cathode current collector is connected to the first housing part by welding or soldering. b. The energy storage element includes a metallic contact element, in particular a metallic contact plate. c. The current collector that is not connected to the first housing part is connected to the contact element by welding or soldering. d. The first housing part and the second housing part are connected by welding or soldering. e. The contact element is preferably coupled to an electrical conductor that extends from the housing through an opening in the second housing component. The immediately preceding features a. to e. are particularly preferably realized in combination with one another.

[0152] In further preferred developments of the first and second variants, the energy storage element according to the invention has the following characteristics a. to e., which are described immediately below: a. The free edge strip of the anode current collector or the free edge strip of the cathode current collector is connected to the second housing part by welding or soldering. b. The energy storage element includes a metallic contact element, in particular a metallic contact plate. c. The current collector that is not connected to the first housing part is connected to the contact element by welding or soldering. d. The first housing part and the second housing part are connected by welding or soldering. e. The contact element is preferably coupled to an electrical conductor extending from the housing through an opening in the first housing component. It is particularly preferred that the immediately preceding features a. to e. are realized in combination with one another. In these developments, the housing parts are electrically connected.

[0153] In a third, preferred variant, the housing of the energy storage element according to the invention has at least one of the following characteristics a. and b., which are described immediately below, and particularly preferably a combination of two of these characteristics: a. The housing includes a tubular first housing part having two terminal openings, a second housing part that closes one of the openings, and a third housing part that closes the other of the openings. b. The contact element, in particular the contact plate, is a second housing part and / or a third housing part.

[0154] In this variant, the cell housing is also prismatic. The tubular first housing part preferably has a polygonal, in particular rectangular or hexagonal, cross section, and the second and third housing parts are also preferably polygonal, in particular rectangular or hexagonal, correspondingly. The three housing parts are preferably connected by welding or soldering. Thus, they preferably have the same electrical polarity.

[0155] In a preferred development of this variant, the free edge strip of the anode current collector or the free edge strip of the cathode current collector is connected to the second housing part by welding or soldering, and the current collector not connected to the second housing part is connected to a separate contact element by welding or soldering, which is coupled to an electrical conductor leading out of the housing, in particular through an opening in the first housing part or through an opening in the third housing part.

[0156] Both the first and second housing parts, and, if applicable, the third housing part, are preferably made of an electrically conductive material, in particular a metallic material. The housing parts can be made of, for example, nickel-plated steel, stainless steel (e.g., 1.4303 or 1.4304 grade), copper, nickel-plated copper, or alloyed or unalloyed aluminum. It may also be suitable for the housing part electrically connected to the cathode to be made of aluminum or an aluminum alloy, and for the housing part electrically connected to the anode to be made of copper or a copper alloy, or nickel-plated copper.

[0157] The main advantage of this variant is that no housing parts need to be produced by upstream molding and / or casting operations to form the housing. Rather, a tubular first housing part with a polygonal cross section serves as the starting point.

[0158] The prismatic housings described above can be particularly well filled by prismatic composite assemblies, and for this purpose it is particularly preferred that the stacked electrodes of the assemblies have a substantially rectangular basic shape.

[0159] The housing parts are preferably sheet metal parts having a thickness in the range of 50 μm to 600 μm, preferably in the range of 150-350 μm, which in turn are preferably made of alloys or non-alloys of aluminum, titanium, nickel or copper, optionally also stainless steel (for example of 1.4303 or 1.4304 standard) or nickel-plated steel.

[0160] Welding or soldering the contact elements to the current collector The concept of welding the edges of current collectors with contact elements is known from WO 2017 / 215900 A1 or JP 2004-119330 A1. This technique allows a particularly high current-carrying capacity and a low internal resistance. Therefore, reference is made in full to the contents of WO 2017 / 215900 A1 and JP 2004-119330 A1 with regard to the methods for electrically connecting contact elements to the edges of current collectors.

[0161] There are several ways in which the contact elements can be connected to the edge of the current collector. The contact elements can be connected to the edge along the aforementioned linear contact section via at least one weld seam. Each edge can thus comprise one or more sections, each of which is continuously connected to one or more contact elements over its entire length via a weld seam. It is particularly preferred that these sections have a minimum length of 5 mm, preferably 10 mm, and particularly preferably 20 mm.

[0162] In one possible development, the section or sections connected to the contact element continuously over their entire length extend over at least 25%, preferably over at least 50%, more preferably over at least 75% of the total length of the respective edge of the current collector. In some preferred embodiments, the edge is continuously welded to the contact element along its entire length. In a further possible embodiment, the contact element is connected to the edge of the current collector via multiple weld spots.

[0163] Soldering the edges of the current collector to the contact elements can be achieved, for example, by providing the contact elements with a solder coating. The solder joint can be created by pressing the edges of the current collector together, coating them, and heating the contact elements to a temperature above the melting temperature of the solder. As is known, solder is an agent that connects metals by soldering. Generally, solders are alloys of different metals. Alloys containing at least one metal from the group consisting of lead, tin, zinc, silver, and copper are particularly frequently used.

[0164] Lithium Depot The functionality of a lithium-ion cell is based on the availability of sufficient mobile lithium ions (mobile lithium) to balance the current drawn by the traffic between the anode and cathode or between the negative and positive electrodes. Mobile lithium means that lithium is available for storage and that removal processes within the electrodes can be activated for this purpose during the discharge and charge processes of the lithium-ion cell. Over time, losses of mobile lithium occur during the discharge and charge processes of a lithium-ion cell. These losses occur as a result of various, largely unavoidable, side reactions. Losses of mobile lithium already occur during the first charge / discharge cycle of a lithium-ion cell. During this first charge / discharge cycle, a top layer typically forms on the surface of the electrochemically active components of the negative electrode. This top layer, called the solid electrolyte interphase (SEI), typically consists primarily of electrolyte decomposition products but also a certain amount of lithium tightly bound within this layer. The loss of mobile lithium associated with this process is particularly significant in cells in which the anode contains silicon moieties.

[0165] To compensate for these losses, the energy storage element according to the invention preferably has at least one of the following characteristics a. to c., which are described immediately below: a. The energy storage element includes an electrode capable of reversibly accepting and releasing lithium, an organic electrolyte including a lithium-conducting salt, and a depot of lithium or lithium-containing material not contained in the electrode or electrolyte that can be used to replace the loss of mobile lithium during operation of the energy storage element. b. The depot is in contact with an electrolyte. c. The energy storage element has at least one electrical conductor and, if necessary, additionally at least one controllable switch, via which the depot can be electrically connected to at least one of the positive electrodes or at least one of the negative electrodes of the energy storage element. It is particularly preferred that the immediately preceding features a. to c. are realized in combination with one another. For convenience, the depot is preferably arranged within the housing of the energy storage element according to the invention.

[0166] The electrically accessible lithium depot allows for the supply of lithium to the electrode as needed or the removal of excess lithium from the electrode to prevent lithium plating. To this end, the lithium depot can be connected to the negative electrode or the positive electrode via at least one electrical conductor. Excess lithium can be delivered to the lithium depot and deposited there as needed. For these applications, means can be provided to allow external observation of cell balance by separately monitoring the individual potential differences of the anode and cathode and / or via electrochemical analysis such as DVA (differential voltage analysis).

[0167] The electrical conductors and associated lithium depots are suitably electrically insulated from the positive and negative electrodes and components electrically coupled thereto.

[0168] The lithium or lithium-containing material of the lithium depot can be, for example, metallic lithium, lithium metal oxide, lithium metal phosphate, or other materials well known to those skilled in the art.

[0169] Another preferred embodiment of the energy storage element. In some particularly preferred embodiments, the housing of the energy storage element is cuboid in shape and characterized by side lengths ranging from 0.5 cm to 200 cm. The nominal capacity of the energy storage element is preferably 100 amp hours.

[0170] In the European Union, manufacturers are strictly regulated when providing information about the nominal capacity of secondary batteries. For example, information about the nominal capacity of secondary nickel-cadmium batteries must be based on measurements in accordance with the IEC / EN61951-1 and IEC / EN60622 standards, information about the nominal capacity of secondary nickel-metal hydride batteries must be based on measurements in accordance with the IEC / EN61951-2 standard, information about the nominal capacity of secondary lithium batteries must be based on measurements in accordance with the IEC / EN61960 standard, and information about the nominal capacity of secondary lead-acid batteries must be based on measurements in accordance with the IEC / EN61056-1 standard. Preferably, all information about nominal capacity in this application is also based on these standards.

[0171] The resulting advantages of the present invention as well as further features thereof can be derived from the following description of preferred examples in conjunction with the drawings, in which each individual feature can be realized either separately or in combination with one another. The examples of embodiments described below merely serve to illustrate and allow a better understanding of the present invention and are not to be understood as limiting in any way. The drawings show, in a schematic manner: [Brief explanation of the drawings]

[0172] [Figure 1] 1 is a top view of a preferred embodiment of a current collector that may be part of an electrode of an energy storage element according to the present invention; [Figure 2] Cross section of the current collector shown in Figure 1 [Figure 3] FIG. 3 is a top view of an anode including the current collector shown in FIGS. 1 and 2. [Figure 4] Cross-section of the anode shown in Figure 3 [Figure 5] FIG. 4 is a top view of a cell fabricated using the anode shown in FIG. 3, which may be part of an assembly of an energy storage element according to the present invention. [Figure 6]Cross-section of the cell shown in Figure 5 [Figure 7A] 1 is a top view of a preferred embodiment of an anode of an energy storage element having a rectangular base in accordance with the present invention; [Figure 7B] 1 is a top view of a preferred embodiment of a cathode of an energy storage element having a rectangular base in accordance with the present invention; [Figure 7C] FIG. 7B is a top view of an assembly formed using the electrodes shown in FIGS. 7A and 7B. [Figure 8] FIG. 10 is a cross-sectional view of a preferred embodiment of an energy storage element having a housing according to the third preferred embodiment. [Figure 9] 3 shows a cross-sectional view of a further preferred embodiment of an energy storage element having a housing according to the first preferred variant described above; [Figure 10] 1 is a cross-sectional view of a further preferred embodiment of an energy storage element having a housing according to the first preferred variant described above, showing details of the structure of the individual cells; DETAILED DESCRIPTION OF THE INVENTION

[0173] 1 and 2 illustrate the design of a current collector 115, which may be part of an electrode of an energy storage element according to the present invention. FIG. 2 is a cross-sectional view along S1. The current collector 115 includes a plurality of openings 211, which are rectangular holes. Region 115x is characterized by the openings 211, while region 115z along longitudinal edge 115a is free of openings. Thus, current collector 115 has a significantly lower weight per unit area in region 115x than in region 115z.

[0174] Figures 3 and 4 illustrate an anode 120 fabricated by applying anode material 155 to both sides of the current collector 115 shown in Figures 1 and 2. Figure 4 is a cross-sectional view along S2. The current collector 115 now has a main area 122 filled with a layer of anode material 123 and a free edge strip 121 extending along the longitudinal edge 115a that is not filled with electrode material 155. In addition, the electrode material 155 also fills the opening 211.

[0175] 5 and 6 illustrate the simplest case of an electrochemical cell 104 constructed using the anode 120 shown in FIGS. 3 and 4. Additionally, the electrochemical cell includes a cathode 130 and separators 118 and 119. FIG. 6 is a cross-sectional view along S3. The cathode 130 is based on the same current collector design as the anode 120. The current collectors 115 and 125 of the anode 120 and cathode 130 preferably differ only in their respective material selection. For example, the current collector 125 of the cathode 130 includes a main region 116 filled with a layer of positive electrode material 123 and a free edge strip 117 extending along a longitudinal edge 125a that is not filled with electrode material 123. The cell 104 can be combined with additional electrodes and separators into an assembly 105, such as may be included in an energy storage element 100 according to the present invention.

[0176] In some preferred embodiments, the free edge strips 117 and 121 are coated on both sides and in at least some areas with an electrically insulating support material, e.g., a ceramic material such as silicon oxide or aluminum oxide. The cathode current collector 125 can be formed, for example, of aluminum, and the active material coating 123 thereon can be formed, for example, of NMCA (lithium nickel manganese cobalt aluminum oxide). The anode current collector 115 can be formed, for example, of copper, and the active material coating 155 thereon can be, for example, a mixture of graphite and silicon. It is worth noting that the separators 118 and 119 can be replaced with a layer of solid electrolyte, depending on the electrochemical system used.

[0177] 7A, 7B, and 7C illustrate the structure of assembly 105.

[0178] 7A shows a cathode 130 having a rectangular base. Similar to the cathode shown in FIG. 6, this cathode includes a cathode current collector coated with positive electrode material 123 in a main region 116, with edge strips 117 along two adjacent sides of the cathode 130 that are free of electrode material 123. However, a ceramic coating 165 is provided in a subregion of the streaky edge strip 117 as support material. The two side edges 125a of the cathode current collector that are coated with ceramic coating 165 are not covered by support material.

[0179] 7B shows an anode 120 having a rectangular base. Similar to the anode shown in FIG. 6, this anode includes an anode current collector coated with anode material 155 in a main region 122, and along two adjacent sides of the anode 120 are edge strips 121 free of electrode material 155. A ceramic coating 165 is provided on a subregion of the edge strip 121, similarly striped, as support material. However, the two side edges 115a to which the ceramic coating 165 is applied are not covered by the support material.

[0180] 7A and 7B. The anode 120 and cathode 130 are the two upper electrodes of the composite; the additional electrodes below are not visible in this top view. In this composite, the electrodes of the same polarity are identically formed in each case. A separator 118 is arranged between the anode 120 and the cathode 130.

[0181] The anode 120 and cathode 130 of each cell are each the same size. They are slightly offset from one another so that an edge 125a of the cathode current collector protrudes from two adjacent sides of the assembly, and an edge 115a of the anode current collector protrudes from the other two adjacent sides of the assembly 105. Contact elements 102 and 112 are welded to these sides. Each of the two contact elements 102 and 112 has an L-shaped cross section.

[0182] The energy storage element 100 shown in Figure 8 includes a prismatic assembly 105 having six rectangular faces and axially inserted into a tubular housing part 101 having a rectangular cross section. At its ends, housing part 101 has two rectangular openings into which rectangular housing parts 111 and 145 are inserted. Ideally, both housing parts 111 and 145 are constructed entirely or partially from metal. Edges 111a and 145a of housing parts 111 and 145 are connected to housing part 101 by welding such that housing parts 101, 110, and 145 form a liquid-tight housing.

[0183] The assembly 105 is formed from a plurality of rectangular electrodes. Each electrode includes a current collector, with the negative current collector filled with a layer of negative electrode material and the positive current collector filled with a layer of positive electrode material. A longitudinal edge 115a of the anode current collector extends beyond the upper side 105b of the assembly 105. A longitudinal edge 125a of the cathode current collector extends beyond the bottom surface 105c of the assembly 105.

[0184] Residing directly on the longitudinal edge 115a of the anode current collector is a metal sheet serving as contact element 102. It is connected to the longitudinal edge 115a by welding.

[0185] Energy storage element 100 further includes a metallic pole pin 108 that is welded to contact element 102 and extends from the housing of energy storage element 100 through a central opening in housing part 111. Pole pin 108 is electrically insulated from housing part 111 using insulating means 103.

[0186] The longitudinal edge 125a of the cathode current collector directly abuts the inner (upper) surface of the housing part 145. The longitudinal edge 125a is connected to the housing part 145 by welding. The welding can be performed, for example, by welding through the housing part 145 with a laser. The housing part 145 here functions as the second contact element 112.

[0187] The energy storage element 100 shown in FIG. 9 includes a prismatic assembly 105 having six rectangular sides and axially inserted into a housing part 107. The housing part 107 includes a rectangular bottom 107a and has a rectangular cross section. At its upper end, the housing part 107 has a rectangular opening into which a rectangular housing part 111 is inserted. Ideally, both housing parts 107 and 111 are constructed entirely or partially from metal. An edge 111a of the housing part 111 is connected to the housing part 107 by welding, so that the housing parts 107 and 111 form a liquid-tight housing.

[0188] The assembly 105 is formed of a plurality of rectangular electrode cells. Each electrode includes a current collector, with the negative electrode current collector filled with a layer of negative electrode material and the positive electrode current collector filled with a layer of positive electrode material. A longitudinal edge 115a of the anode current collector extends beyond the upper side 105b of the assembly 105. A longitudinal edge 125a of the cathode current collector extends beyond the bottom surface 105c of the assembly 105.

[0189] Residing directly on the longitudinal edge 115a of the anode current collector is a metal sheet serving as contact element 102. It is connected to the longitudinal edge 115a by welding.

[0190] Energy storage element 100 further includes a metallic pole pin 108 that is welded to contact element 102 and extends from the housing of energy storage element 100 through a central opening in housing part 111. Pole pin 108 is electrically insulated from housing part 111 using insulating means 103.

[0191] The longitudinal edge 125a of the cathode current collector directly abuts the inner (upper) surface of the bottom portion 107a. The longitudinal edge 125a is connected to the bottom portion 107a by welding. The welding can be performed, for example, by welding through the bottom portion 107a with a laser. The bottom portion 107a here functions as the second contact element 112.

[0192] The energy storage element 100 shown in FIG. 10 includes a housing part 107, which includes a rectangular bottom 107a, a rectangular cross-section, and a circular opening (defined by an edge 101a). The housing part 107 is a deep-drawn part. At its upper end, the housing part 107 has a rectangular opening into which a rectangular housing part 111 is inserted. Ideally, both housing parts 107 and 111 are constructed entirely or partially of metal. The edge 111a of the housing part 111 is connected to the housing part 107 by welding, so that the housing parts 107 and 111 form a liquid-tight housing. The edge 107a of the housing part 101 is bent inward approximately 90° over the edge 111a of the housing part 111. The housing part 107, together with the housing part 111, encloses an interior space 137 in which the composite assembly 105 is disposed.

[0193] Prismatic assembly 105 has six rectangular sides and is formed from a plurality of rectangular electrodes and separators (exemplified by separators 118 and 119). Each electrode includes a current collector. The longitudinal edges of the separators form two side surfaces of assembly 105, from which current collectors (115 and 125) project. Corresponding projections are labeled d1 and d2. A longitudinal edge 115a of the anode current collector projects from side surface 105b of assembly 105, here located at the top. Projecting from bottom surface 105c of assembly 105 is a longitudinal edge 125a of the cathode current collector.

[0194] Each anode current collector 115 is filled at its main area with a layer of negative electrode material 155. Each cathode current collector 125 is filled at its main area with a layer of positive electrode material 123. Each anode current collector 115 has an edge strip 121 extending along its longitudinal edge 115a that is not filled with electrode material 155. Instead, each current collector is applied with a coating 165 of ceramic support material to stabilize the current collector in the area. Each cathode current collector 125 has an edge strip 117 extending along its longitudinal edge 125a that is not filled with electrode material 123. Instead, each current collector is likewise applied with a coating 165 of ceramic support material.

[0195] Residing directly on the longitudinal edge 115a of the anode current collector is a metal sheet serving as contact element 102. It is connected to the longitudinal edge 115a by welding.

[0196] Energy storage element 100 further includes a metallic pole pin 108 that is welded to contact element 102 and extends from the housing of energy storage element 100 through a central opening in housing part 111. Pole pin 108 is electrically insulated from housing part 111 using insulating means 103.

[0197] The longitudinal edge 125a of the cathode current collector directly abuts the inner (upper) surface of the bottom portion 107a. The longitudinal edge 125a is connected to the bottom portion 107a by welding. The welding can be performed, for example, by welding through the bottom portion 107a with a laser. The bottom portion 107a here functions as the second contact element 112.

[0198] The positive electrode included in assembly 105 can include, for example, 95 wt% NMCA, 2 wt% electrode binder, and 3 wt% carbon black as a conductive agent. In a preferred embodiment, the negative electrode included in assembly 105 can include, for example, 70 wt% silicon, 25 wt% graphite, 2 wt% electrode binder, and 3 wt% carbon black as a conductive agent. For example, a solution of 2 M LiPF in THF / mTHF (1:1) or a solution of 1.5 M LiPF in FEC / EMC (3:7) can be used as the electrolyte with 2 wt% vinylene carbonate (VC).

[0199] The current collector, and in particular the anode current collector 115, may have a plurality of openings. These may be, for example, square or circular holes. Preferably, the openings are located only in the area of ​​the current collector that is coated with the active material. The edge areas that are not coated with the active material are preferably free of openings. The current collector is therefore characterized by a significantly reduced weight per unit area in the areas with openings. If the current collector is coated with an active material, the active material can also be deposited in the openings, thus allowing for a larger application volume.

Claims

1. An energy storage element (100), comprising: a. a plurality of anodes (120) and cathodes (130); b. each of said anodes (120) comprises an anode current collector (115); c. each of said anode current collectors (115) a main area filled with a layer of anode material (155); a free edge strip (121) extending along the edge (110a) of said anode current collector (110) and not filled with said negative electrode material (155); d. each of said cathodes (130) comprises a cathode current collector (125); e. each of said cathode current collectors (125) comprises: a main area filled with a layer of positive electrode material (123); a free edge strip (117) extending along the edge (125a) of said cathode current collector (125) and not filled with said positive electrode material (123); f. The anode (120) and the cathode (130) are stacked to form an assembly (105), the anode (120) and the cathode (130) being separated by a separator (118, 119) or a layer of solid electrolyte; g. The assembly (105) is enclosed in a prismatic housing; h. the free edge strip (121) of the anode current collector (115) protrudes from at least two sides of the assembly (105) and the free edge strip (117) of the cathode current collector (125) protrudes from at least two other sides of the assembly (105); i. the energy storage element has at least one metallic contact element (102, 112) connected to the free edge strips (117, 121) of the anode current collector (115) and / or the cathode current collector (125) by welding or soldering; An energy storage element (100) characterized by:

2. The following additional features: a. The anode (120) and the cathode (130) are polygonal in shape; b. The assembly (105) has a prismatic shape; 10. The energy storage element of claim 1, comprising at least one of:

3. The following characteristics: a. at least one contact element (102, 112) having an L-shaped profile; b. at least one contact element having a U-shaped profile; 3. The energy storage element according to claim 1, wherein the energy storage element comprises at least one of:

4. The following characteristics: a. the walls of the prismatic housing serve as the contact elements (112); b) the contact element is electrically connected to the housing; The energy storage element according to any one of claims 1 to 3, wherein the energy storage element has any one of the following:

5. The following additional features: a. the housing has at least one pole bushing (108), the pole bushing being electrically connected to the contact element (102); The energy storage element according to any one of claims 1 to 4, wherein

6. An energy storage element (100) according to any one of claims 1 to 5, characterized in that it has the following additional features: a. comprising a solid electrolyte between the anode (120) and the cathode (130); The energy storage element (100) having

7. The following additional features: a. the free edge strip (121) of the anode current collector (115) and / or the free edge strip (117) of the cathode current collector (125) are coated with a support material (165) different from the positive electrode material (123) and the negative electrode material (155) disposed on the respective current collectors; The energy storage element according to any one of claims 1 to 6, wherein

8. The following additional features: a. the support material (165) is a non-metallic material; b. The support material (165) is an electrically insulating material; c. The non-metallic material is a ceramic material, a glass-ceramic material, or a glass; d. The ceramic material is aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), titanium nitride (TiN), titanium aluminum nitride (TiAlN), silicon oxide or titanium carbonitride (TiCN); 8. The energy storage element of claim 7, comprising at least one of:

9. The following additional features: a. the free edge strip (121) of the anode current collector (115) and / or the free edge strip (117) of the cathode current collector (125) each include a first sub-region and a second sub-region, the first sub-region being coated with the support material (165) while the second sub-region is not coated; b. the first sub-region and the second sub-region are each linear or strip-shaped and extend parallel to each other; c. the first sub-region is located between the main region and the second sub-region of the anode current collector (115) or the cathode current collector (125); 9. The energy storage element according to claim 7 or 8, comprising at least one of:

10. The following additional features: a. the free edge strip (121) of the anode current collector (115) and / or the free edge strip (117) of the cathode current collector (125) are coated with the support material (165) up to the edge of the respective current collector; The energy storage element according to any one of claims 7 to 9, wherein

11. The following additional features: a. the separator (118, 119) comprises at least one inorganic material that enhances resistance to thermal stress; The energy storage element according to any one of claims 1 to 10, wherein

12. The following additional features: a. the at least one inorganic material is included in the separator (118, 119) as a particulate filler; 12. The energy storage element of claim 11, wherein

13. The following additional features: a. the at least one inorganic material is present as a coating on the surface of the separator (118, 119); 13. The energy storage element of claim 11 or claim 12, wherein

14. The following additional features: a. the at least one inorganic material is or comprises an electrically insulating material; b) the at least one inorganic material is or comprises at least one material selected from the group consisting of a ceramic material, a glass-ceramic material, and a glass; c. the at least one inorganic material is or comprises a lithium ion conducting ceramic material; d. the at least one inorganic material is or comprises an oxide material; e. The ceramic material or the oxide material is aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), titanium nitride (TiN), titanium aluminum nitride (TiAlN), silicon oxide or titanium carbonitride (TiCN); The energy storage element according to any one of claims 11 to 13, comprising at least one of:

15. The following additional features: a. the separator (118, 119) contains the at least one inorganic material only in certain regions; b. said separators (118, 119) have an edge strip along at least one of their edges that includes said at least one inorganic material as a coating and / or as a particulate filler; c. the separator (118, 119) has a major area free of the at least one inorganic material; The energy storage element according to any one of claims 11 to 14, comprising at least one of:

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