EP2789031A1 - Electrochemical cells comprising nitrogen-containing polymers - Google Patents

Abstract

Electrochemical cells comprise: (A) at least one cathode comprising at least one lithium ion-containing transition metal compound, (B) at least one anode, and at least one layer comprising (a) at least one polymer comprising monomer units comprising nitrogen-containing 5- or 6- membered heterocyclic aromatic structural units or comprising an organic radical which derives from a-aminophosphonic acid or from iminodiacetic acid, and (b) optionally at least one binder.

Description

 ELECTROCHEMICAL CELLS COMPRISING NITROGEN-CONTAINING POLYMERS

Description The present invention relates to electrochemical cells containing

 (A) at least one cathode containing at least one lithium-ion-containing transition metal compound,

 (B) at least one anode, and

 (C) at least one layer containing

 (a) at least one polymer comprising monomer units containing the nitrogen-containing 5- or

Contain 6-membered heterocyclic aromatic structural units or contain an organic radical derived from α-aminophosphonic acid or iminodiacetic acid, and

 (b) optionally at least one binder.

Furthermore, the present invention relates to the use of electrochemical cells according to the invention, and lithium-ion batteries, containing at least one electrochemical cell according to the invention. Saving energy has long been an object of growing interest. Electrochemical cells, such as batteries or accumulators, can be used to store electrical energy. Of particular interest since recently the so-called lithium-ion batteries. They are superior in some technical aspects to conventional batteries. So you can create with them voltages that are not accessible with batteries based on aqueous electrolytes.

In this case, the materials from which the electrodes are made, and in particular the material from which the cathode is made, play an important role. In many cases, use is made of lithium-containing transition metal mixed oxides, in particular lithium-containing nickel-cobalt-manganese oxides having a layer structure, or manganese-containing spinels which may be doped with one or more transition metals. A problem of many batteries, however, remains the cycle stability, which is still to be improved. Especially with such batteries, which contain a relatively high proportion of manganese, for example in electrochemical cells with a manganese-containing spinel electrode and a graphite anode, one often observes a strong loss of capacity within a relatively short time. Furthermore, it can be seen that in cases where one selects graphite anodes as counterelectrodes, elemental manganese is deposited on the anode. It is envisioned that these manganese nuclei deposited on the anode have a potential of less than 1 V vs. Li / Li ^{+ act} as a catalyst for a reductive decomposition of the electrolyte. It should also be irreversibly bound lithium, causing the lithium-ion battery gradually loses capacity. WO 2009/033627 discloses a sheet which can be used as a separator for lithium-ion batteries. It comprises a nonwoven as well as embedded in the nonwoven particles, which consist of organic polymers and optionally partly of inorganic material. Although such separators can be used to avoid short circuits caused by metal dendrites. In WO 2009/033627, however, no long-term cyclization experiments are disclosed.

WO 201 1/024149 discloses lithium-ion batteries containing an alkali metal such as lithium between the cathode and anode, which serves as a scavenger of unwanted by-products or impurities and is referred to as a scavenger. Both in the production of the secondary battery cells and in a later recycling of the disused cells due to the presence of highly reactive alkali metal appropriate safety precautions must be taken. It was therefore the object to provide electrical cells that have an improved life and in which you must observe no deposition of elemental manganese even after several cycles, or in whose production you can use a scavenger, which has a lower security problem than the alkali metals and prolongs the life of the cell to the desired extent.

This object is achieved by an initially defined electrochemical cell, which

(A) at least one cathode containing at least one lithium-ion-containing transition metal compound,

 (B) at least one anode, and

(C) at least one layer containing

 (A) at least one polymer comprising monomer units containing nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or iminodiacetic acid, and

 (b) optionally containing at least one binder.

The cathode (A) contains at least one lithium-ion-containing transition metal compound, such as the transition metal compounds L1C0O2, LiFeP0 ₄ or lithium manganese spinel known to those skilled in lithium ion battery technology. Preferably, the cathode (A) contains as lithium ion-containing transition metal compound, a lithium ion-containing transition metal oxide containing manganese as the transition metal.

In the context of the present invention, lithium ion-containing transition metal oxides which contain manganese as the transition metal are understood to mean not only those oxides which have at least one transition metal in cationic form but also those which have at least two transition metal oxides in cationic form. Moreover, in the context of the present invention, such compounds are also termed "lithium ions". NEN-containing transition metal oxides "which comprise, besides lithium, at least one metal in cationic form which is not a transition metal, for example aluminum or calcium." In a preferred embodiment, manganese may be present in the cathode (A) in the formal oxidation state Particularly preferred is manganese in cathode (A) in a formal oxidation state in the range of +3.5 to +4.

Many elements are ubiquitous. In certain very small proportions, for example, sodium, potassium and chloride can be detected in virtually all inorganic materials. In the context of the present invention, proportions of less than 0.1% by weight of cations or anions are neglected. A lithium ion-containing transition metal mixed oxide which contains less than 0.1% by weight of sodium is therefore considered to be sodium-free in the context of the present invention. Accordingly, a lithium ion-containing transition metal mixed oxide containing less than 0.1 wt .-% sulfate ions, in the context of the present invention as sulfate-free.

In one embodiment of the present invention, lithium ion-containing transition metal oxide is a transition metal mixed oxide containing at least one other transition metal in addition to manganese.

In one embodiment of the present invention, lithium ion-containing transition metal compound is selected from manganese-containing lithium iron phosphates and preferably from manganese-containing spinels and manganese-containing transition metal oxides having a layer structure, in particular manganese-containing transition metal mixed oxides having a layer structure.

In one embodiment of the present invention, lithium ion-containing transition metal compound is selected from those compounds having a more than stoichiometric amount of lithium. In one embodiment of the present invention, manganese-containing spinels are selected from those of the general formula (I) where the variables are defined as follows:

0.9 <a <1, 3, preferably 0.95 <a <1, 15,

O s b s 0.6, for example 0.0 or 0.5,

where, in the case of choosing M ¹ = Ni, it is preferred that 0.4 <b ^ 0.55,

-0.1 <d <0.4, preferably 0 <d <0.1, M ¹ is selected from one or more elements selected from Al, Mg, Ca, Na, B, Mo, W, and transition metals of the first period of the periodic table of the elements. Preferably, M ^{1 is} selected from Ni, Co, Cr, Zn, Al, and most preferably M ^{1 is} Ni. In one embodiment of the present invention, manganese-containing spinels are selected from those of the formula LiNio.sMn-i.sC-d and LiM.sup.-C.

In another embodiment of the present invention, manganese-containing transition metal oxides having a layer structure of those of the formula (II) where the variables are defined as follows: 0 <t <0.3 and

M ² selected from Al, Mg, B, Mo, W, Na, Ca and transition metals of the first period of the Periodic Table of the Elements, wherein the or at least one transition metal is manganese. In one embodiment of the present invention, at least 30 mol% of M ^{2 are} selected from manganese, preferably at least 35 mol%, based on total content of M ² .

In one embodiment of the present invention, M ^{2 is} selected from combinations of Ni, Co and Mn which contain no other elements in significant amounts.

In another embodiment, M ^{2 is} selected from combinations of Ni, Co and Mn which contain at least one further element in significant amounts, for example in the range from 1 to 10 mol% of Al, Ca or Na. In one embodiment of the present invention, manganese-containing transition metal oxides having a layered structure are selected from those in which M ^{2 is} selected from Nio, 33Coo, 33Mno, 33, Ni ₀ , 5Coo, 2Mn ₀ , 3, Ni ₀ , 4Coo, 3Mn ₀ , 4, Ni ₀ , 4Coo, 2Mn ₀ , 4 and Ni ₀ , 45Coo, ioMn ₀ , 45.

In one embodiment, lithium-containing transition metal oxide is present in the form of primary particles which are agglomerated to form spherical secondary particles, the average particle diameter (D50) of the primary particles in the range from 50 nm to 2 μm, and the mean particle diameter (D50) of the secondary particles in Range of 2 μηη to 50 μηη lies.

Cathode (A) may contain one or more ingredients. For example, cathode (A) may contain carbon in conductive modification, for example selected from graphite, carbon black, carbon nanotubes, graphene or mixtures of at least two of the aforementioned substances. Furthermore, cathode (A) may contain one or more binders, also called binders, for example one or more organic polymers. Suitable binders are, for example, organic (co) polymers. Suitable (co) polymers, ie homopolymers or copolymers, can be selected, for example, from (co) polymers obtainable by anionic, catalytic or free-radical (co) polymerization, in particular from polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and copolymers of at least two comonomers from ethylene, propylene, styrene, (meth) acrylonitrile and 1, 3-butadiene, in particular styrene-butadiene copolymers. In addition, polypropylene is suitable, furthermore polyisoprene and polyacrylates are suitable. Particularly preferred is polyacrylonitrile.

In the context of the present invention, polyacrylonitrile is understood to mean not only polyacrylonitrile homopolymers, but also copolymers of acrylonitrile with 1,3-butadiene or styrene. Preference is given to polyacrylonitrile homopolymers. In the context of the present invention, polyethylene is understood to mean not only homo-polyethylene, but also copolymers of ethylene which contain at least 50 mol% of ethylene and up to 50 mol% of at least one further comonomer, for example α-olefins such as Propylene, butylene (1-butene), 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-pentene, furthermore isobutene, vinylaromatics such as styrene, for example

(Meth) acrylic acid, vinyl acetate, vinyl propionate, Ci-Cio-alkyl esters of (meth) acrylic acid, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, further maleic acid, maleic anhydride and itaconic. Polyethylene may be HDPE or LDPE.

In the context of the present invention, polypropylene is understood to mean not only homo-polypropylene but also copolymers of propylene which contain at least 50 mol% of propylene polymerized and up to 50 mol% of at least one further comonomer, for example ethylene and α-propylene. Olefins such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene. Polypropylene is preferably isotactic or substantially isotactic polypropylene.

In the context of the present invention, polystyrene is understood to mean not only homopolymers of styrene, but also copolymers with acrylonitrile, 1,3-butadiene, (meth) acrylic acid, C 1 -C 10 -alkyl esters of (meth) acrylic acid, divinylbenzene, in particular 1, 3. Divinylbenzene, 1, 2-diphenylethylene and a-methylstyrene.

Another preferred binder is polybutadiene.

Other suitable binders are selected from polyethylene oxide (PEO), cellulose, carboxymethyl cellulose, polyimides and polyvinyl alcohol. In one embodiment of the present invention, binders are selected from those (co) polymers which have an average molecular weight M _w in the range from 50,000 to 1,000,000 g / mol, preferably up to 500,000 g / mol. Binders may be crosslinked or uncrosslinked (co) polymers.

In a particularly preferred embodiment of the present invention, binders are selected from halogenated (co) polymers, in particular from fluorinated (co) polymers. Halogenated or fluorinated (co) polymers are understood as meaning those (co) polymers which contain at least one (co) monomer in copolymerized form which has at least one halogen atom or at least one fluorine atom per molecule, preferably at least two halogen atoms or at least two fluorine atoms per molecule.

Examples are polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymers, perfluoroalkylvinyl ether copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride copolymers. Chlorotrifluoroethylene copolymers and ethylene-chlorofluoroethylene copolymers. Suitable binders are in particular polyvinyl alcohol and halogenated (co) polymers, for example polyvinyl chloride or polyvinylidene chloride, in particular fluorinated (co) polymers such as polyvinyl fluoride and in particular polyvinylidene fluoride and polytetrafluoroethylene.

Furthermore, cathode (A) may comprise further conventional components, for example a current conductor, which may be configured in the form of a metal wire, metal grid, metal mesh, expanded metal, metal sheet or a metal foil. Aluminum foils are particularly suitable as metal foils.

In one embodiment of the present invention, cathode (A) has a thickness in the range of 25 to 200 μηη, preferably from 30 to 100 μηη, based on the thickness without Stromableiter.

Inventive electrochemical cells also contain at least one anode (B). In one embodiment of the present invention, anode (B) may be selected from anodes of carbon and anodes containing Sn or Si. For example, carbon anodes may be selected from hard carbon, soft carbon, graphene, graphite, and especially graphite, intercalated graphite, and mixtures of two or more of the aforementioned carbons. Anodes containing Sn or Si can be selected, for example, from nanoparticulate Si or Sn powder, Si or Sn fibers, carbon-Si or carbon-Sn composites and Si-metal or Sn metal alloys. Anode (B) may comprise one or more binders. In this case, one can choose as binder one or more of the abovementioned binders, which are mentioned in the context of the description of the cathode (A). Furthermore, anode (B) may have further conventional components, for example a current conductor, which may be designed in the form of a metal wire, metal grid, metal mesh, expanded metal, or a metal foil or a metal sheet. As metal foils in particular copper foils are suitable. In one embodiment of the present invention, anode (B) has a thickness in the range of 15 to 200 μηη, preferably from 30 to 100 μηη, based on the thickness without Stromableiter.

Electrochemical cells according to the invention furthermore contain (C) at least one layer, also called layer (C) for short, which contains (a) at least one polymer, also referred to as polymer (a), which comprises monomer units which contain nitrogen-containing 5- or 6-membered heterocyclic compounds - contain aromatic structural units, or which contain an organic radical derived from α-aminophosphonic acid or iminodiacetic acid, and which (b) optionally at least one binder, also referred to as binder (b).

Nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units are known to the person skilled in the art in principle. These may be monovalent or polyvalent, for example divalent or trivalent, monocyclic or polycyclic, substituted or unsubstituted structural units. Examples of such structural units are,

wherein the atom marked with ^* indicates the position over which the structural unit is incorporated in the polymer. Preferred is imidazolyl as a structural unit. Integral structural units may be linked directly or via a divalent link to a polymer backbone, while dinuclear structural units may be incorporated into a polymer backbone. In a preferred embodiment of the present invention, the polymer (a) contained in layer (C) comprises monomer units which contain nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or which contain an organic radical. which is derived from α-aminophosphonic acid or from iminodiacetic acid, those monomer units which are selected from the group of the monomer units consisting of

wherein X is O, S or NR and R is hydrogen or a C1-C4 alkyl group, such as methyl, ethyl, n-propyl or n-butyl. In a particularly preferred embodiment, the monomer unit is N-vinylimidazole.

The polymer (a) contained in layer (C) may be a homopolymer which contains in each case only one monomer unit which contains a nitrogen-containing 5- or 6-membered heterocyclic aromatic structural unit or which contains an organic radical which differs from o

 Derived from aminophosphonic acid or from iminodiacetic acid. Further, the polymer (a) contained in layer (C) may be a copolymer containing, in addition to the at least one monomer unit containing a nitrogen-containing 5- or 6-membered heterocyclic aromatic moiety or containing an organic radical other than α-aminophosphonic acid or derives from imino-diacetic acid, contains at least one further monomer unit. The further monomer unit of the copolymer may, in principle, be any known monomer unit which is copolymerizable together with the former monomer unit.

The polymer (a) contained in layer (C) may contain the monomer units containing the nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or iminodiacetic acid in a proportion of 0.5% by weight up to 100% by weight, preferably of at least 5% by weight %, more preferably of at least 20 wt .-%, most preferably of at least 40 wt .-%, in particular of at least 50 wt .-% based on the total mass of the polymer (a). In a preferred embodiment of the present invention, the polymer (a) contained in layer (C) is a copolymer containing the monomer units N-vinylimidazole and N-vinyl-2-pyrrolidinone. Copolymers containing N-vinylimidazole and N-vinyl-2-pyrrolidinone are known. For example, a crosslinked copolymer containing N-vinyl imidazole and N-vinyl-2-pyrrolidinone as Divergan ^® HM of BASF is commercially available which sungsmitteln in all customary solu- is insoluble. However, there are containing N-vinyl-2-pyrrolidinone and N-vinylimidazole are commercially available, solutions of copolymers such as Sokalan ^® HP 56 K or Sokalan ^® HP 66 K from BASF.

Depending on the properties of the polymer (a) discussed above in layer (C), this polymer may be present in different form in layer (C). An insoluble polymer as the cross-linked copolymer Divergan ^® HM of BASF is preferably incorporated in the form of particles in layer (C), while a corresponding soluble polymer can be processed into a film or even homogeneous in the layer (C), for example on or in a carrier material, which may be of organic or inorganic origin, can be applied. For example, the separators described in WO 2009/033627 or the ingredients with a solution of a copolymer containing N-vinyl-2-pyrrolidinone and N-vinylimidazole, for example, a solution of Sokalan ^® HP 66 K or Luvitec VPI 55 K 72 ^® W can be treated, For example, be soaked or sprayed to get to a modified separator with which an electrochemical cell according to the invention can be produced. It is also possible to use polymer (a) in particulate form together with the inorganic or organic particles used in WO 2009/033627 for the production of correspondingly modified nonwovens. Also possible is the chemical attachment of a first polymer (a) or a monomer unit containing nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or iminodiacetic acid, to a Another polymer to go by grafting to new polymers (a), for example, by grafting of vinylimidazole to an aromatic polyether ketone or by grafting a copolymer of N-vinyl-2-pyrrolidinone and N-vinylimidazole on polyethylene glycol. In one embodiment of the present invention, the electrochemical cells according to the invention are characterized in that the polymer contained in layer (C) is present in particulate form, in the form of a film or homogeneously distributed in layer (C). The polymer contained in layer (C) is preferably present in particulate form. In the context of the present invention, polymers in particulate form can have an average particle diameter (D50) in the range from 0.05 to 100 μm, preferably 0.5 to 10 μm, particularly preferably 2 to 6 μm. The proportion by weight of the polymer (a) in the total mass of the layer (C) can be up to 100 wt .-%. The weight fraction of the polymer (a) in the total mass of the layer (C) is preferably at least 5% by weight, particularly preferably 40 to 80% by weight, in particular the weight fraction of the polymer (a) is based on the total mass of the layer (C ) in the range of 30 to 50 wt .-%.

In one embodiment of the present invention, binder (b) is selected from such binders as described in connection with binders for the cathode (s) (A). In a preferred embodiment of the present invention, layer (C) comprises a binder (b) selected from the group of polymers consisting of polyvinyl alcohol, styrene-butadiene rubber, polyacrylonitrile, carboxymethylcellulose and fluorine-containing (co) polymers, in particular selected from styrene-butadiene- Rubber and fluorine-containing (co) polymers. In one embodiment of the present invention, binder (b) and binder for cathode and for anode, if present, are the same.

In another embodiment, binder (b) differs from binder for cathode (A) and / or binder for anode (B), or binder for anode (B) and binder for cathode (A) are different.

In one embodiment of the present invention, layer (C) has an average thickness in the range from 0.1 μm to 250 μm, preferably from 1 μm to 100 μm, and particularly preferably from 5 μm to 30 μm.

Layer (C) is preferably a layer which does not conduct the electric current, that is to say an electrical insulator. On the other hand, layer (C) is preferably a layer which permits the migration of ions, in particular of ions. Layer (C) is preferably arranged spatially between cathode and anode within the electrochemical cell according to the invention.

In electrochemical cells, the direct, short-circuiting contact of the anode with the cathode is usually prevented by the installation of a separator.

In a further embodiment of the present invention, the electrochemical cells according to the invention are characterized in that layer (C) is a separator.

Layer (C) may contain, in addition to the polymer (a) and the optional binder (b), further constituents, for example support materials such as fibers or nonwovens, which provide improved stability of layer (C) without compromising their necessary porosity and ion permeability. Alternatively or additionally, layer (C) may also contain at least one porous plastic layer, for example a polyolefin membrane, in particular a polyolefin membrane. lyethylene or a polypropylene membrane. In turn, polyolefin membranes can be composed of one or more layers. Porous polyolefin membranes or nonwovens themselves can usually fulfill the function of a separator alone. Also, layer (C) may contain particles of inorganic or organic nature, which are mentioned, for example, in WO 2009/033627.

In one embodiment of the present invention, the electrochemical cells according to the invention are characterized in that layer (C) additionally contains a nonwoven (c). Fleece (c) may be made of inorganic or organic materials.

Examples of organic nonwovens are polyester nonwovens, in particular polyethylene terephthalate nonwovens (PET nonwovens), polybutylene terephthalate nonwovens (PBT nonwovens), polyimide nonwovens, polyethylene and polypropylene nonwovens, PVdF nonwovens and PTFE nonwovens.

Examples of inorganic nonwovens are glass fiber nonwovens and ceramic fiber nonwovens.

Depending on the composition of the layer (C), this may be, for example, alone from the polymer (a), for example a porous film of the polymer (a), or from polymer (a) in particulate form and a binder (b) or from a Polyesterervliess with consist evenly distributed particles of the polymer (a). In these cases, layer (C) itself can already be used as a separator in the electrochemical cell according to the invention and can thus cover the cathode (A) or the anode (B) on at least one side. Furthermore, a layer (C) can also be applied to a commonly usable battery separator, such as a porous polyolefin membrane or a nonwoven, so that layer (C) covers a separator on at least one side. Layer (C) can also be applied as a thin layer on cathode or anode and the electrochemical cell according to the invention thus produced additionally contain a porous polyolefin membrane as a separator. In a further embodiment of the present invention, the electrochemical cells according to the invention are characterized in that layer (C) covers the cathode (A) or a separator or the anode (B) on at least one side.

Another object of the present invention is the use of a polymer (a), as described above, comprising monomer units containing nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or from Derives iminodiacetic acid, for the production of an electrochemical cell, in particular an electrochemical cell according to the invention, as described above.

The layer (C) contained in the electrochemical cell according to the invention can also be used independently of the assembly of the electrochemical cell according to the invention, depending on its structure. Rochemical cell are produced as semi-finished and later by a battery manufacturer as part of an electrochemical cell, for example as a finished separator or together with a typical battery separator, such as a PET nonwoven or a porous polyolefin membrane, between the cathode and anode in an electrochemical cell installed ,

Electrochemical cells according to the invention may further comprise customary constituents, for example conductive salt, nonaqueous solvent, furthermore cable connections and housings. In one embodiment of the present invention, electrochemical cells according to the invention contain at least one non-aqueous solvent, which may be liquid or solid at room temperature, preferably liquid at room temperature, and which is preferably selected from polymers, cyclic or non-cyclic ethers, cyclic or not cyclic acetals, cyclic or non-cyclic organic carbonates and ionic liquids.

Examples of suitable polymers are in particular polyalkylene glycols, preferably P0IV-C1-C4-alkylene glycols and in particular polyethylene glycols. Polyethylene glycols may contain up to 20 mol% of one or more C 1 -C 4 -alkylene glycols in copolymerized form. Polyalkylene glycols are preferably double-capped polyalkylene glycols with methyl or ethyl.

The molecular weight M _w of suitable polyalkylene glycols and especially of suitable polyethylene glycols may be at least 400 g / mol.

The molecular weight M _w of suitable polyalkylene glycols and in particular of suitable polyethylene glycols may be up to 5,000,000 g / mol, preferably up to 2,000,000 g / mol. Examples of suitable non-cyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, preference is 1, 2-dimethoxyethane.

Examples of suitable cyclic ethers are tetrahydrofuran and 1,4-dioxane. Examples of suitable non-cyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane and 1,1-diethoxyethane.

Examples of suitable cyclic acetals are 1, 3-dioxane and in particular 1, 3-dioxolane. Examples of suitable non-cyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate. Examples of suitable cyclic organic carbonates are compounds of the general formulas (X) and (XI)

in which R ¹ , R ² and R ^{3 may be} identical or different and selected from hydrogen and C 1 -C 4 -alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec. Butyl and tert-butyl, preferably R ² and R ^{3 are} not both tert-butyl.

In particularly preferred embodiments, R ^{1 is} methyl and R ² and R ³ are each hydrogen, or R ¹ , R ² and R ³ are each hydrogen.

Another preferred cyclic organic carbonate is vinylene carbonate, formula (XII).

O

} X o

 \ = J

Preferably, the solvent or solvents are used in the so-called anhydrous state, i. with a water content in the range of 1 ppm to 0.1 wt .-%, determined for example by Karl Fischer titration.

Inventive electrochemical cells also contain at least one conductive salt. Suitable conductive salts are in particular lithium salts. Examples of suitable lithium salts are LiPF ₆ , LiBF ₄ , UCIO ₄ , LiAsF ₆ , UCF 3 SO 3, LiC (CnF _{2n +} iSO 2) 3, lithium imides such as LiN (CnF ₂ n ₊ iSO ₂ ) ₂ , where n is an integer in the range of 1 to 20 , LiN (SO 2 F) 2, Li 2 SiFe, LiSbF 6, LiAICU, and salts of the general formula (C _n F 2n + i SO 2) m X Li, where m is defined as follows:

m = 1, if X is selected from oxygen and sulfur,

m = 2 when X is selected from nitrogen and phosphorus, and

m = 3, when X is selected from carbon and silicon.

Preferred conductive salts are selected from LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiPF ₆ , LiBF ₄ , LiCl ₄ , and particularly preferred are LiPF 6 and LiN (CF 2 SO 2) 2. Electrochemical cells according to the invention furthermore contain a housing which can have any shape, for example cuboid or the shape of a cylinder. In another embodiment, electrochemical cells according to the invention have the shape of a prism. In one variant, a metal-plastic composite film prepared as a bag is used as the housing.

Inventive electrochemical cells provide a high voltage of up to about 4.8 V and are characterized by a high energy density and good stability. In particular, electrochemical cells according to the invention are characterized by only a very small loss of capacity during repeated cycling.

Another object of the present invention is the use of electrochemical cells according to the invention in lithium-ion batteries. Another object of the present invention are lithium-ion batteries, containing at least one electrochemical cell according to the invention. Inventive electrochemical cells can be combined with one another in lithium-ion batteries according to the invention, for example in series connection or in parallel connection. Series connection is preferred.

Another object of the present invention is the use of inventive electrochemical cells as described above in automobiles, powered by electric motor two-wheelers, aircraft, ships or stationary energy storage.

Another object of the present invention is therefore also the use of lithium-ion batteries according to the invention in devices, in particular in mobile devices. Examples of mobile devices are vehicles, for example automobiles, two-wheeled vehicles, aircraft or watercraft, such as boats or ships. Other examples of mobile devices are those that you move yourself, such as computers, especially laptops, phones or electrical tools, for example, in the field of construction, in particular drills, cordless screwdrivers or cordless tackers.

The use of lithium-ion batteries in devices according to the invention offers the advantage of a longer running time before recharging as well as a lower capacity loss with a longer running time. If one wanted to realize an equal running time with electrochemical cells with a lower energy density, then one would have to accept a higher weight for electrochemical cells.

The invention is illustrated by the following, but not limiting examples of the invention. Percentages are by weight in each case, unless expressly stated otherwise. 1.1 Production of a Separator According to the Invention (S.1)

A crosslinked copolymer of vinylpyrrolidone (VP) and N-vinylimidazole (VI) in the ratio 10:90 (Divergan ^® HM from BASF) was dissolved in a fluid-bed opposed jet mill AFG on particle large ground (less than 8 μηη x10 = 1, 2 μηη, x50 = 4.7 μηη, x90 = 7.9 μηη). The determination of the particle size distribution was carried out by means of laser diffraction technology in powder form with a mastersizer from Malvern Instruments GmbH, Herrenberg, Germany.

From a glass fiber fleece (Whatman, 260 μηη thickness) punched out discs with 13 mm diameter and dried in a drying oven at 120 ° C for several hours. Thereafter, the glass fiber nonwoven discs were transferred to an argon-filled glove box. Each glass fiber fleece disc was divided into two parts, so that from a 260 μηη thick glass fiber fleece disc two glass fiber fleece discs emerged, each about 130 μηη thick. Was previously ground crosslinked copolymer of VI and VP (90:10) (Divergan ^® HM) was uniform and bleed partitioned between the two fiberglass discs, so that a glass fiber fleece / Divergan ^® HM / glass fiber fleece sandwich about a relative surface coverage having at Divergan ^® HM of about 5-10 mg / cm ^2.

I.2 producing a separator (S.2) of the invention An aqueous solution of an uncrosslinked copolymer of vinylpyrrolidone and N-vinylimidazole in the ratio 45:55 (Luvitec VPI 55 K 72 W ^® from BASF) was in the oven at 40 ° C overnight evaporated in vacuo. The residue was coarsely ground with a mortar and pestle and then dried in an evacuated desiccator over P2O5 for 2 days. The dried residue was finely ground under argon blanketing gas with an agate gravy tray until the particle size was below about 20 μm. From a glass fiber fleece (Whatman, 260 μηη thickness) punched out discs with 13 mm diameter and dried in a drying oven at 120 ° C for several hours. Thereafter, the glass fiber fleece discs were transferred into an argon filled glove box. Each glass fiber fleece disc was divided into two parts, so that from a 260 μηη thick glass fiber fleece disc two glass fiber fleece discs emerged, each about 130 μηη thick. The above-ground Luvitec ^® VPI 55 K 72 W was uniform and bleed partitioned between the two fiberglass discs, so that a glass fiber fleece / Luvitec ^® VPI 55 K 72 VW fiberglass mat sandwich was that W about a relative area coverage of Luvitec ^® VPI 55 K 72 of about 5-10 mg / cm ² . I.3 Production of a Separator According to the Invention (S.3)

1, 9 g of Divergan previously prepared ^® HM fine material from Example 1.1 were large with 0.2 g of a 50 wt .-% aqueous emulsion of a styrene-butadiene rubber (average particle: 190 nm, glass transition temperature: - 10 °. C; Binder 20-01) and 8 ml of water to a stirrable suspension and stirred for about 1 h. The suspension thus obtained is stretched uniformly to a PET web, commercially available as nonwoven "PES20" from. Apodis filter OHG and drying the coated nonwoven overnight at room temperature. After drying to obtain a fabric having a Divergan ^® HM occupation rules 5-10 mg / cm ² each, followed by punching 13 mm diameter slices therefrom and drying again in a vacuum drying oven at 120 ° C. for 16 hours.

 Subsequently, this disc was transferred to an argon-filled glove box.

I.4 Preparation of a Separator Not According to the Invention (V-S.4)

The experiment of Example 1.1 and I.2 was repeated mutatis mutandis in the same conditions, however, the glass fiber fleece now has not been 55 K 72 W filled with Divergan ^® HM or ^® Luvitec VPI, but used unchanged, to obtain Vergleichsseparator VS.4. I.5 Preparation of a Separator Not According to the Invention (VS.5)

The experiment of Example I.3 was repeated under the same conditions, however, the PET web was not coated with Divergan ^® HM but uncoated used to obtain Vergleichsseparator VS.5.

II. Production of Electrochemical Cells and Their Testing

The following electrodes were always used: Cathode (A.1): in each case one used a lithium-nickel-manganese spinel electrode, which was produced as follows. One mixed with each other:

85% LiMni, ₅ Ni ₀ , ₅ O4,

6% PVdF, commercially available as Kynar Flex ^® 2801 Arkema Group,

6% carbon black, BET surface area of 62 m ² / g, commercially available as "Super P Li" from Timcal, 3% graphite, commercially available as KS6 from Timcal;

in a screw-in container. With stirring, it was mixed with as much N-methyl-pyrrolidone until a tough lump-free paste was obtained. It was stirred for 16 hours.

Then, the resulting paste was lazelte on 20 μηη thick aluminum foil and dried for 16 hours in a vacuum oven at 120 ° C. The thickness of the coating was 30 μηη after drying. Then punched out circular disk-shaped segments, diameter: 12 mm. Anode (B.1): One mixed with each other

91% graphite ConocoPhillips C5,

6% PVdF, commercially available as Kynar Flex ^® 2801 Arkema Group,

3% carbon black, BET surface area of 62 m ² / g, commercially available as "Super P Li" from Timcal in a screw-on vessel with stirring, adding so much N-methyl pyrrolidone until a viscous lump-free paste was obtained It was stirred for 16 hours.

Then, the resulting paste was laced to 20 μηη thick copper foil and dried for 16 hours in a vacuum oven at 120 ° C. The thickness of the coating was after drying 35 μηη. Then punched out circular disk-shaped segments, diameter: 12 mm.

The following electrolytes were always used:

 1 M solution of LiPF 6 in anhydrous ethylene carbonate-ethylmethyl carbonate mixture (parts by weight 1: 1)

11.1 Production of an Electrochemical Cell EZ.1 According to the Invention and Testing

The inventive separator (S.1) prepared according to 1.1 was dripped with electrolyte in an argon-filled glove box and positioned between a cathode (A.1) and an anode (B.1), so that both the anode and the Cathode had direct contact with the separator. Inventive electrochemical cell EZ.1 was obtained. The electrochemical examination took place between 4.25 V and 4.8 V in so-called Swagelok cells. The first two cycles were run at 0.2C rate for formation; cycles # 3 to # 50 were cycled at 1 C rate, followed by another 2 cycles at 0.2C rate followed by 48 cycles at 1 C rate, etc. Charging or discharging the cell was accomplished with the aid of a "MACCOR Battery Tester" performed at room temperature.

 It could be shown that the battery capacity remained very stable over repeated charging and discharging.

11.2 to II.5 Preparation of the Electrochemical Cells EZ.2, EZ.3, and V-EZ.4, V-EZ.5 and Testing Analogously to Example 11.1 were prepared from the separators S.2, S.3, and VS. 4, and VS.5 the electrochemical cells EZ.2, EZ.3, as well as V-EZ.4, and V-EZ.5 prepared and tested accordingly.

FIG. 1 shows the schematic structure of a disassembled electrochemical cell for testing separators according to the invention and not according to the invention. The explanations in FIG. 1 mean:

1, 1 'stamp

2, 2 'mother

3, 3 'sealing ring - each double, the second, slightly smaller sealing ring is not shown here

 4 spiral spring

 5 current conductors made of nickel

 6 housing

Results:

The electrochemical cell EZ.1 could be charged and discharged very stably over 160 cycles and lost only 27% of the starting capacity after 130 cycles.

The electrochemical cell EZ.2 could be charged and discharged very stably over 160 cycles and lost only 1 1% of the starting capacity after 130 cycles.

The electrochemical cell EZ.3 could be charged and discharged very stably over 160 cycles and lost only 14% of the starting capacity after 130 cycles.

The electrochemical cells V-EZ.4 degraded relatively strong and lost after about 130 cycles 46% of the starting capacity. The electrochemical cells V-EZ.5 from the comparative example degraded relatively strongly and also lost 46% of the starting capacity after about 130 cycles.

Claims

claims 1 . Electrochemical cell containing (A) at least one cathode containing at least one lithium-ion-containing transition metal compound,  (B) at least one anode, and  (C) at least one layer containing  (A) at least one polymer comprising monomer units containing nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or iminodiacetic acid, and  (b) optionally at least one binder. 2. An electrochemical cell according to claim 1, characterized in that lithium ion-containing transition metal compound selected from manganese-containing spinels and manganese-containing transition metal oxides having a layer structure. 3. An electrochemical cell according to claim 1 or 2, characterized in that anode (B) is selected from anodes of carbon and anodes containing Sn or Si. 4. An electrochemical cell according to any one of claims 1 to 3, characterized in that the polymer contained in layer (C) comprises monomer units which are selected from the group of monomer units consisting of wherein X is O, S or NR and R is hydrogen or a C1-C4 alkyl group. 5. An electrochemical cell according to any one of claims 1 to 3, characterized in that the polymer contained in layer (C) is a copolymer containing the monomer units N-vinylimidazole and N-vinyl-2-pyrrolidinone. 6. An electrochemical cell according to any one of claims 1 to 5, characterized in that in layer (C) containing polymer in particulate form, in the form of a film or homogeneously distributed in layer (C) is present. 7. Electrochemical cell according to one of claims 1 to 6, characterized in that layer (C) contains a binder (b) selected from the group of polymers consisting of polyvinyl alcohol, styrene-butadiene rubber, polyacrylonitrile, carboxymethylcellulose and fluorine-containing ( co) polymers. 8. An electrochemical cell according to any one of claims 1 to 7, characterized in that layer (C) has an average thickness in the range of 9 to 50 μηη. 9. An electrochemical cell according to any one of claims 1 to 8, characterized in that layer (C) is a separator. 10. An electrochemical cell according to any one of claims 1 to 9, characterized in that layer (C) additionally contains a fleece (c). 1 1. Electrochemical cell according to one of claims 1 to 10, characterized in that layer (C) covers the cathode (A) or a separator or the anode (B) on at least one side. 12. Use of electrochemical cells according to one of claims 1 to 1 1 in lithium-ion batteries. 13. Lithium-ion battery, comprising at least one electrochemical cell according to one of claims 1 to 1 1st 14. Use of electrochemical cells according to any one of claims 1 to 1 1 in automobiles, powered by electric motor two-wheelers, aircraft, ships or stationary energy storage. Use of a polymer comprising monomer units containing nitrogen-containing 5- or 6-membered heterocyclic aromatic structural units or containing an organic radical derived from α-aminophosphonic acid or iminodiacetic acid for the preparation of an electrochemical cell.