WO2013060410A1 - Use of comb polymers in lithium ion batteries - Google Patents

Abstract

The invention relates to the use of at least one polymer having a carbon primary chain and at least 5, preferably 10 carbon side chains connected to the primary chain, wherein the number of side chains equals 0.5 to 2.5 based on 100 monomer units of the primary chain, and, independently, the number of carbon atoms per side chain equals 100 to 500, characterized in that the polymer is used as an electrolyte component for a lithium ion battery.

Description

 Use of comb polymers in lithium ion batteries

Hereby, the entire content of the priority application DE 10 2011 1 17 262.2 by reference is part of the present application.

The present invention relates to the use of comb polymers as an electrolyte component in an electrolyte for a lithium-ion battery. The invention further relates to an electrolyte for a lithium ion battery comprising comb polymers, a separator comprising the electrolyte, an electrode comprising the electrolyte and a lithium-ion battery containing the electrolyte and / or the separator and / or the electrode having.

For applications of rechargeable lithium-ion batteries, for example, in vehicles with hybrid or pure electric drive or as a stationary Spei- rather, it is necessary that the electrolyte used in the battery still has low ion temperature or sufficient ionic conductivity, thus the battery as evenly as possible Electricity can be taken.

The object of the present invention is to provide an electrochemical cell, preferably a rechargeable lithium-ion battery, in which the electrolyte ensures good ionic conductivity even at low temperature.

This object is achieved by the use of a polymer or more polymers as defined in claim 1. Advantageous developments are defined in the subclaims and the independent claims. According to a first aspect, the invention relates to the use of at least one comb polymer as the electrolyte component in an electrolyte for a lithium-ion battery.

According to the invention, the comb polymer has a carbon backbone and at least 5 carbon side chains attached to the backbone. The carbon backbone of the polymer is obtainable by polymerization of olefinic monomer units. The side chain may preferably be introduced via functional groups located on the main chain. The number of side chains based on 100 monomer units of the main chain is chosen so that it is 0.5 to 2.5. The number of carbon atoms per side chain is independently from 100 to 500. In absolute terms, per carbon backbone of a comb polymer at least 5 carbon side chains, preferably at least 10, more preferably at least 50, more preferably at least 100 side chains.

The use of the at least one polymer as the electrolyte component in an electrolyte for a lithium-ion battery has the advantage that the electrolyte has a relatively uniform viscosity both at high and at low temperatures, so that the ionic conductivity in the electrolyte is relatively high over a wide temperature range is constant. Thus, the properties of the lithium-ion battery over a wide temperature range are uniform. An electrochemical cell containing the electrolyte containing the polymer used according to the invention can therefore be advantageously used in vehicles with hybrid drive or electric drive and in stationary storage.

In one embodiment, the number of side chains based on 100 monomer units of the main chain is 0.6 to 2.0.

In another embodiment, the number of side chains based on 100 monomer units of the main chain is 0.7 to 1.8. In another embodiment, the number of carbon atoms per side chain is independently 200 to 500.

In another embodiment, the number of carbon atoms per side chain is independently 350 to 450.

In a further embodiment, the polymers according to the invention are used in an amount of from 0.1% by weight to 50% by weight, based on the total amount of the electrolyte. Further usable amounts are in the range of 0.1 to 40 wt .-% or 0.1 to 30 wt .-% or 0.1 to 20 wt .-% or 0.1 to 10 wt .-%.

In a further embodiment, it is possible to increase the amount of the polymer used according to the invention in the electrolyte to more than 50 wt .-%. Such amounts may preferably be desired if the electrolyte is to be in the form of a solid electrolyte.

In one embodiment, the amount of polymer used in the invention is in the range of 50 to 60 wt.% Or 60 to 70 wt.% Or 70 to 80 wt.% Or 80 to 90 wt.% Or 90 to 98 wt .-%. In further embodiments, the amount of polymer used according to the invention is in the range of 50-98% by weight or 60-98% by weight or 70-98% by weight or 80-98% by weight. The terms used below are defined within the meaning of the invention. polymer

The polymer used according to the invention or the polymers used according to the invention can also be referred to as comb polymers. The term "comb polymer" means one or more polymers containing a backbone from which side chains extend, and in English-speaking countries, the term "bottlebrush polymer" or "comb polymer" is also often used. The term "carbon side chains attached to the main chain" means that the side chains are bonded in a covalent bond to the main chain The polymers used according to the invention are known per se, for example from DE 10 2009 001 447, and / or can be prepared by known processes Suitable processes include, for example, the polymerization of alkenes and / or alkadienes, for example C 2 -C 10 alkenes such as ethylene, propylene, n-butene, isobutene, norbornene and / or C 4 -C 10 -alkadienes such as butadiene, isoprene, norbornadiene the monomer units in the polymer is preferably at least 70% by weight and more preferably at least 80% by weight and most preferably at least 90% by weight, based on the weight of the polymer In addition to the monomer units derived from alkenes and / or alkadienes Copolymerizable monomer units can also be used to prepare the comb polymer include and include, inter alia, alkyl (meth) acrylates, styrenic monomers, fumarates, maleates, vinyl esters and / or vinyl ethers. The proportion of these copolymerizable monomers is preferably at most 30% by weight, particularly preferably at most 15% by weight, based on the weight of the comb polymer (s). Furthermore, the monomer units may have initial groups and / or end groups which serve for functionalization. Through these groups, the side chains can be introduced into the polymer. The proportion of these initial groups and / or end groups is preferably at most 30 wt .-%, more preferably at most 15 wt .-%, based on the weight of the comb polymer.

Preferably, the number average molecular weight of the main chain is in the range of 500 to 50,000 g / mol, more preferably 700 to 10,000 g / mol, especially 1,500 to 5,500 g / mol, and most preferably 4,000 to 5,000 g / mol.

In addition to the olefinic monomer units, the comb polymers used according to the invention may comprise low molecular weight monomer units a molecular weight less than 500 g / mol. The term "low molecular weight" means that a part of the main chain of the comb polymer has a low molecular weight than 500 to 50,000 g / mol. Depending on the preparation, this molecular weight may result from the molecular weight of the monomers used to prepare the polymers. The molecular weight of the low molecular weight monomer units is preferably at most 400 g / mol, more preferably at most 200 g / mol, and most preferably at most 150 g / mol. These monomers include, but are not limited to, alkyl (meth) acrylates, styrenic monomers, fumarates, maleates, vinyl esters and / or vinyl ethers. Among the preferred low molecular weight monomers are styrene monomers having 8 to 17 carbon atoms, alkyl (meth) acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having 1 to 1 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group,

(Di) alkyl fumarates having 1 to 10 carbon atoms in the alcohol group, (di) alkyl maleates having 1 to 10 carbon atoms in the alcohol group and mixtures of these monomers are derived. These monomers are well known to those skilled in the art.

Examples of styrene monomers having 8 to 17 carbon atoms are styrene, substituted styrenes having an alkyl substituent in the side chain, such. B. ct-

Methylstyrene and α-ethylstyrene, substituted styrenes having an alkyl substituent on the ring such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes.

The term "(7Wetf) JacAy / ate" includes acrylates and methacrylates as well as mixtures of acrylates and metfiacrylates. The alkyl (meth) acrylates having 1 to 10 carbon atoms in the alcohol group include in particular (meth) acrylates derived from saturated alcohols, such as methyl (meth) acrylate,

Ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, 2-tert-butylheptyl (meth) acrylate, octyl (meth) acrylate, 3-iso-propylheptyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate; (Meth) acrylates which differ from unsaturated derived th alcohols, such as. 2-propynyl (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, oleyl (meth) acrylate; Cycloalkyl (meth) acrylates, such as cyclopentyl (meth) acrylate, 3-vinylcyclohexyl (meth) acrylate.

Preferred alkyl (meth) acrylates comprise 1 to 8, more preferably 1 to 4 carbon atoms in the alcohol group. The alcohol group may hereby be linear or branched.

Examples of vinyl esters having 1 to 1 carbon atoms in the acyl group include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate. Preferred vinyl esters include 2 to 9, more preferably 2 to 5 carbon atoms in the acyl group. The acyl group here may be linear or branched.

Examples of vinyl ethers having 1 to 10 carbon atoms in the alcohol group include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl butyl ether. Preferred vinyl ethers have 1 to 8, more preferably 1 to 4 carbon atoms in the alcohol group. The alcohol group may hereby be linear or branched.

The notation (di) ester means that monoesters, diesters and mixtures of esters, especially fumaric acid and / or maleic acid can be used. The (di) alkyl fumarates having 1 to 10 carbon atoms in the alcohol group include, but are not limited to, monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, methyl ethyl fumarate, monobutyl fumarate, dibutyl fumarate, dipentyl fumarate and dihexyl fumarate. preferred

(Di) alkyl fumarates include 1 to 8, more preferably 1 to 4, carbon atoms in the alcohol group. The alcohol group may hereby be linear or branched.

The (di) alkyl maleates having from 1 to 10 carbon atoms in the alcohol group include, among others, monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, methyl ethyl maleate, monobutyl maleate, dibutyl maleate. Preferred (di) alkyl maleates comprise 1 to 8, particularly preferably 1 to 4, carbon atoms. in the alcohol group. The alcohol group may hereby be linear or branched.

In addition to the particularly preferred repeating units set out above, the comb polymers used according to the invention may comprise further repeating units derived from further comonomers, the proportion of which is preferably at most 20% by weight, preferably at most 10% by weight and particularly preferably at most 5% by weight. , based on the weight of the repeating units.

These include, but are not limited to, monomer units derived from alkyl (meth) acrylates having from 11 to 30 carbon atoms in the alcohol group, especially undecyl (meth) acrylate, 5-methylundecyl (meth) acrylate, dodecyl (meth) acrylate, 2- Methyldodecyl (meth) acrylate, tridecyl (meth) acrylate, 5-methyltridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, 2-methylhexadecyl (meth) acrylate, heptadecyl ( meth) acrylate, 5-iso-propylheptadecyl (meth) acrylate, 4-tert-butyloctadecyl (meth) acrylate, 5-ethyloctadecyl (meth) acrylate, 3-iso-propyloctadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, Cetyleicosyl (meth) acrylate, Stearyleicosyl (meth) acrylate, docosyl (meth) acrylate and / or Eicosyltetratriacontyl (meth) acrylate.

Since the comb polymers preferably contain ester moieties, which in one embodiment represent the end groups, the side chains can be attached to the carbon backbone via these end groups by transesterification with long-chain alcohols. Long-chain alcohols are preferably alcohols which can be prepared in a known manner by hydroxylation of long-chain polyolefins having a terminal double bond.

By the ratio of monomers to copolymers and / or the ratio of functionalized groups to the amount of alcohol used, the ratio of monomer units to the side chain can be controlled and thus adjusted. In one embodiment, the polymer or polymers in the main chain have monomer units derived from alkenes and / or alkadienes and copolymerizable monomer units selected from one or more of the following monomers: alkyl (meth) acrylates, styrene monomers, fumarates, Maleates, vinyl esters and / or vinyl ethers. The side chains are then linear and / or branched and / or cyclic carbon groups containing alkyl groups.

Electrolyte According to a second aspect, the invention relates to an electrolyte for a lithium-ion battery, wherein the electrolyte has at least one polymer as the electrolyte component, characterized in that the polymer has a carbon backbone and at least 5, preferably at least 10 carbon side chains attached to the main chain the carbon chain of the polymer is obtainable by polymerization of olefinic monomer units, wherein the number of side chains based on 100 monomer units of the main chain is 0.5 to 2.5, and the number of carbon atoms per side chain is independently 100 to 500. The term "electrolyte component" means a constituent of the electrolyte.Other constituents of the electrolyte, in addition to the comb polymer used according to the invention, are preferably an organic solvent and a lithium salt The electrolyte may additionally contain further constituents a liquid and a conductive salt. Preferably, the liquid is a solvent for the conducting salt. Preferably, the electrolyte is then present as an electrolyte solution.

Suitable solvents are preferably inert. Suitable solvents are preferably solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methyl propyl carbonate, butylmethyl carbonate, ethylpropyl carbonate, dipropyl carbonate, cyclopentanones, sulfolanes, dimethylsufoxide, 3-methyl-1,3-oxazolidin-2-one, γ-butyrolactone, 1, 2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, methyl acetate, ethyl acetate, nitromethane, 1, 3-propanesultone.

In one embodiment, ionic liquids may also be used as the solvent. Such "ionic liquids" contain only ions. Preferred cations which may in particular be alkylated are imidazolium, pyridinium, pyrrolidinium, guanidinium, uronium, thiuronium, piperidinium, morpholinium, sulfonium, ammonium and phosphonium cations. Examples of useful anions are halide, tetrafluoroborate, trifluoroacetate, triflate, hexafluorophosphate, phosphinate and tosylate anions.

Examples of ionic liquids which may be mentioned are: N-methyl-N-propyl piperidinium bis (trifluoromethylsulfonyl) imide, N-methyl-N-butylpyrrolidinium bis (trifluoromethylsulfonyl) imide, N-butyl-N trimethylammonium bis (trifluoromethylsulfonyl) imide, triethylsulfonium bis (trifluoromethylsulfonyl) imide, N, N-diethyl-N-methyl-N- (2-methoxyethyl) -ammonium bis (trifluoromethylsulfonyl) -imide.

Preferably, two or more of the above-mentioned liquids are used. Preferred conductive salts are lithium salts which have inert anions and which are preferably non-toxic. Suitable lithium salts are preferably lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoro-methylsulfonylimide), lithium trifluoromethanesulfonate, lithium tris (trifluoro-methylsulfonyl) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium bisoxalatoborate, lithium difluorooxalatoborate and / or lithium chloride; and mixtures of one or more of these salts.

In one embodiment, the organic solvent may be partly or completely omitted. The electrolyte may then be present in this embodiment as a solid mass or as a mass with a solid-like consistency.

In one embodiment, the electrolyte containing the comb polymer is present as a solid electrolyte before or as a polymer electrolyte. The term "polymer electrolyte" in this embodiment means an electrolyte comprising at least one lithium salt and a polymer having a carbon backbone and carbon side chains attached to the backbone, wherein the carbon backbone of the polymer is obtainable by polymerization of olefinic monomer units, wherein the number of side chains is based on 100 monomer units of the main chain is 0.5 to 2.5, and the number of carbon atoms per side chain is independently 100 to 500. The electrolyte according to the invention can be prepared by known methods by mixing the comb polymers with the other components of the electrolyte.

Separator Electrochemical cells, in particular rechargeable lithium-ion batteries, comprise a material that separates the positive electrode and the negative electrode. This material is permeable to lithium ions, so it conducts lithium ions, but is a non-conductor for electrons. Such materials used in lithium ion batteries are also referred to as separators.

In a preferred embodiment according to the present invention, polymers are used as separators. In one embodiment, the polymers are selected from the group consisting of: polyester, preferably polyethylene terephthalate or polybutylene terephthalate; Polyolefin, preferably polyethylene, polypropylene or polybutylene; polyacrylonitrile; polycarbonate; Polysulfone; polyether sulfone; polyvinylidene fluoride; polystyrene; polyetherimide; Polyether; Polyether ketone. The polymers can be used as a film, preferably in the form of a membrane, or as fibers. The fibers may be woven or plain. The use of glass fibers or cellulose fibers as a separator is also possible.

The polymers have pores so that they are permeable to lithium ions.

In a preferred embodiment according to the present invention, the separator comprises at least one polymer and at least one ceramic material, with which the polymer is coated. Consequently, the separator is also characterized by being in the form of a polymer film; or as a polymer film coated with a ceramic material; or as woven or non-woven polymer fibers; or as woven or non-woven polymer fibers coated with a ceramic material.

In a preferred embodiment, the separator comprises at least one polymer and at least one inorganic, preferably ion-conducting material, preferably selected from oxides, phosphates, silicates, titanates, sulfates, aluminosilicates, comprising at least one of the elements zirconium, aluminum, lithium.

Said separator of the battery according to the invention comprises polymer fibers in the form of a nonwoven. Preferably, the web is unwoven. Instead of the term "unwoven", the term "non-woven" is used. The relevant technical literature also includes terms such as "non-woven fabrics" or "non-woven material". The term "nonwoven" is used synonymously with the term "nonwoven". Nonwovens are known from the prior art and / or can be produced by the known processes, for example by spinning processes with subsequent solidification. Preferably, the web is flexible and is made in a thickness of less than 30 microns. Preferably, the polymer fibers are selected from the group of polymers consisting of polyester, polyolefin, polyamide, polyacrylonitrile, polyimide, polyetherimide, polysulfone, polyamide-imide, polyether, polyphenylene sulfide, aramid, or mixtures of two or more of these polymers.

Polyesters are, for example, polyethylene terephthalate and polybutylene terephthalate.

Polyolefins are, for example, polyethylene or polypropylene. Halogen-containing polyolefins such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride are also usable.

Polyamides are for example the known types PA 6.6 and PA 6.0, known under the brand names Perlon Nylon ^® and ^®.

Aramids are, for example meta-aramid and para-aramid, which are known under the brand names Nomex ^® and Kevlar ^®.

Polyamide are loading disallowed for example, under the trade name Kermel ^®.

Preferred polymer fibers are polymer fibers of polyethylene terephthalates.

In a preferred embodiment, the separator comprises a nonwoven, which is coated on one or both sides with an inorganic material.

The term "coating" also includes that the ionic conductive inorganic material may be located not only on one side or both sides of the web, but also within the web.

The ion-conducting inorganic material used for the coating is preferably at least one compound from the group of oxides, phosphates, sulfates, titanates, silicates, aluminosilicates at least one of zirconium, aluminum or lithium. The ion-conducting inorganic material is preferably ion-conducting in a temperature range from -40 ° C. to 200 ° C., ie ion-conducting for the lithium ions. In one embodiment, a separator may be used, which consists of an at least partially permeable carrier, which is not or only poorly electron-conducting. This support is coated on at least one side with an inorganic material. As an at least partially permeable carrier an organic material is used, which is designed as a nonwoven, so from non-woven polymer fibers. The organic material is in the form of polymer fibers, preferably polymer fibers of polyethylene terephthalate (PET). The nonwoven fabric is coated with an inorganic ion-conducting material which is preferably ion-conducting in a temperature range of -40 ° C to 200 ° C. The inorganic ion-conducting material preferably has at least one compound from the group of oxides, phosphates, sulfates, titanates, silicates, aluminosilicates with at least one of the elements zirconium, aluminum, lithium, particularly preferably zirconium oxide. The inorganic ion-conducting material preferably has particles with a maximum diameter of less than 100 nm.

In a preferred embodiment, the ion-conducting material comprises zirconium oxide or the ion-conducting material consists of zirconium oxide.

Such a separator is marketed in Germany, for example, under the trade name "Separion ^®" by the company Evonik AG.

Methods for producing such separators are known from the prior art, for example from EP 1 017 476 B1, WO 2004/021477 and WO 2004/021499.

In principle, too large pores and holes in separators used in secondary batteries can lead to an internal short circuit. The battery can then discharge itself very quickly in a dangerous reaction. In this case, such large electrical currents can occur that a closed Battery cell can even explode in the worst case. For this reason, the separator can also contribute significantly to the safety or lack of security of a high-performance lithium or lithium high-energy battery.

Polymer separators generally prevent any charge transport above a certain temperature (the so-called "shut-down temperature", which is approximately 120 ° C.). This happens because at this temperature, the pore structure of the separator collapses and all pores are closed. The fact that no ions can be transported, the dangerous reaction that can lead to an explosion, comes to a standstill. However, if the cell continues to be heated due to external circumstances, the so-called "break-down temperature" is exceeded at approx. 150 to 180 ° C. From this temperature, the separator melts, causing it to contract. In many places in the battery cell, there is now a direct contact between the two electrodes and thus to a large internal short circuit. This leads to an uncontrolled reaction, which can end with an explosion of the cell, or the resulting pressure must often be reduced by a pressure relief valve (a rupture disk) under fire phenomena.

In the case of the separator preferably used in the battery according to the invention comprising a non-woven of nonwoven polymer fibers and the inorganic coating, it can only come to shut-down (shutdown), when melted by the high temperature, the polymer structure of the carrier material and penetrates into the pores of the inorganic material and this closes it. On the other hand, the separator does not break down (collapse) since the inorganic particles ensure that complete melting of the separator can not occur. Thus, maximum care is taken that there are no operating conditions in which a large-area short circuit can occur.

By the type of nonwoven used, which has a particularly suitable combination of thickness and porosity, separators can be produced which can meet the requirements for separators in high-performance batteries, especially lithium high-performance batteries. The simultaneous use of particle particles of exactly matched oxide particles for the production of the porous (ceramic) coating results in a particularly high porosity of the finished separator, the pores still being sufficiently small to prevent undesired "lithium oxide" growth. Whiskers "through the separator to prevent.

Due to the high porosity of the separator, however, care must be taken to ensure that no or as little dead space as possible is created in the pores.

The separators which are preferably used for the battery according to the invention also have the advantage that the anions of the conducting salt partly adhere to the inorganic surfaces of the separator material, which leads to an improvement in the dissociation and thus to a better ionic conductivity in the high-current range.

The separator preferably usable for the battery according to the invention, comprising a flexible nonwoven with a porous inorganic coating on and in this nonwoven, the material of the nonwoven being selected from (preferably nonwoven) polymer fibers, is also characterized in that the nonwoven fabric has a thickness of less than 30 pm, a porosity of more than 50%, preferably from 50 to 97%, and a pore radius distribution in which at least 50% of the pores have a pore radius of 75 to 150 pm.

The separator particularly preferably comprises a nonwoven which has a thickness of 5 to 30 μm, preferably a thickness of 10 to 20 μm. Also particularly important is a homogeneous distribution of pore radii in the web as indicated above. An even more homogeneous pore radius distribution in the nonwoven, in combination with optimally matched oxide particles of a certain size, leads to an optimized porosity of the separator. The thickness of the substrate has a great influence on the properties of the separator, since on the one hand the flexibility but also the sheet resistance of the electrolyte-impregnated separator depends on the thickness of the substrate. Due to the small thickness, a particularly low electrical resistance of the separator is achieved in the application with an electrolyte. The separator itself has a very high electrical resistance, since it itself must have insulating properties against electrons. In addition, thinner separators allow increased packing density in a battery pack so that one can store a larger amount of energy in the same volume.

Preferably, the nonwoven web has a porosity of 60 to 90%, more preferably 70 to 90%. The porosity is defined as the volume of the web (100%) minus the volume of the fibers of the web, ie the proportion of the volume of the web that is not filled by material. The volume of the fleece can be calculated from the dimensions of the fleece. The volume of the fibers results from the measured weight of the fleece considered and the density of the polymer fibers. The large porosity of the substrate also allows a higher porosity of the separator, which is why a higher uptake of electrolytes with the separator can be achieved.

In order to obtain a separator having insulating properties, as polymer fibers for the non-woven fabric, it preferably has non-electrically conductive fibers of polymers as defined above. Preferably, these are selected from the polymers listed above, preferably polyacrylonitrile, polyester, such as. As polyethylene terephthalate and / or polyolefin, such as. As polypropylene or polyethylene, or mixtures of such polyolefins.

The polymer fibers of the nonwovens preferably have a diameter of from 0.1 to 10 μm, more preferably from 1 to 4 μm.

Particularly preferred flexible nonwovens have a basis weight of less than 20 g / m ² , preferably from 5 to 10 g / m ² . The separator preferably has a porous, electrically insulating, ceramic coating in the preferably non-woven nonwoven fabric. Preferably, the porous inorganic coating on and in the nonwoven comprises oxide particles of the elements Li, Al, Si and / or Zr having an average particle size of from 0.5 to 7 μm, preferably from 1 to 5 μm, and very particularly preferably from 1, 5 to 3 pm. The separator particularly preferably has a porous inorganic coating on and in the nonwoven, the aluminum oxide particles having an average particle size of from 0.5 to 7 μm, preferably from 1 to 5 μm and very particularly preferably from 1.5 to 3 μm which are bonded to an oxide of the elements Zr or Si. In order to achieve the highest possible porosity, preferably more than 50% by weight and more preferably more than 80% by weight of all particles are within the abovementioned limits of average particle size. As already described above, the maximum particle size is preferably 1/3 to 1/5 and particularly preferably less than or equal to 1/10 of the thickness of the nonwoven used.

The nonwoven and ceramic coating separator preferably has a porosity of from 30 to 80%, preferably from 40 to 75% and particularly preferably from 45 to 70%. The porosity refers to the achievable, ie open pores. The porosity can be determined by the known method of mercury porosimetry or can be calculated from the volume and density of the starting materials used, if it is assumed that only open pores are present. The separators preferably used for the battery according to the invention are also distinguished by the fact that they can have a tensile strength of at least 1 N / cm, preferably of at least 3 N / cm and very particularly preferably of 3 to 10 N / cm. The separators can preferably be bent without damage down to any radius down to 100 mm, preferably down to 50 mm and most preferably down to 1 mm. This also makes the separator operational in combination with wound electrodes. The high tensile strength and the good bendability of the separator also have the advantage that changes occurring in the charging and discharging of a battery of the geometries of the electrodes can be through the separator, without this being damaged. This is extremely favorable for the stability and safety of the cell.

In one embodiment, it is possible to design the separator to have the shape of a concave or convex sponge or pad, or the shape of wires or a felt. This embodiment is well suited to compensate for volume changes in the battery. Corresponding preparation methods are known to the person skilled in the art.

In a further embodiment, the polymer fleece used in the separator has a further polymer. Preferably, this polymer is arranged between the separator and the positive electrode and / or the separator and the negative electrode, preferably in the form of a polymer layer.

In one embodiment, the separator is coated with this polymer on one or both sides.

Said polymer may be in the form of a porous membrane, i. as a film, or in the form of a nonwoven, preferably in the form of a nonwoven fabric of non-woven polymer fibers. These polymers are preferably selected from the group consisting of polyester, polyolefin, polyacrylonitrile, polycarbonate, polysulfone, polyethersulfone, polyvinylidene fluoride, polystyrene, polyetherimide.

Preferably, the further polymer is a polyolefin. Preferred polyolefins are polyethylene and polypropylene.

The separator is preferably coated with one or more layers of the further polymer, preferably of the polyolefin, which is preferably also present as a nonwoven, that is to say as nonwoven polymer fibers. Preferably, a non-woven of polyethylene terephthalate is used in the separator, which is coated with one or more layers of the other polymer, preferably the polyolefin, which is preferably also present as a nonwoven, so as non-woven polymer fibers.

Particular preference is given to a separator of the above-described type of separation which is coated with one or more layers of the further polymer, preferably of the polyolefin, which is preferably also present as a nonwoven, ie preferably as nonwoven polymer fibers.

The coating with the further polymer, preferably with the polyolefin, can be achieved by adhesion, lamination, by a chemical reaction, by welding or by a mechanical connection. Such polymer composites and processes for their preparation are known from EP 1 852 926.

Preferably, the nonwovens usable in the separator are made of nanofibers of the polymers used, whereby nonwovens are formed which have a high porosity with formation of small pore diameters. Thus, both the risk of short-circuit reactions can be further reduced.

The fiber diameters of the polyethylene terephthalate fleece are preferably larger than the fiber diameters of the further polymer fleece, preferably the polyolefin fleece, with which the separator is coated on one or both sides.

Preferably, the nonwoven made of polyethylene terephthalate then has a higher pore diameter than the nonwoven, which is made of the other polymer.

The use of a polyolefin in addition to the polyethylene terephthalate ensures increased safety of the electrochemical cell, since in undesired or excessive heating of the cell, the pores of the polyolefin contract and the charge transport through the separator through is made or terminated. Should the temperature of the electrochemical cell increase to such an extent that the polyolefin begins to melt, the polyethylene terephthalate effectively counteracts the melting together of the separator and thus an uncontrolled destruction of the electrochemical cell.

The good or even sufficient ion conductivity of the Separion® type separator for lithium ions, even at low temperatures, for example at -40 ° C., in combination with the sufficient ionic conductivity of the electrolyte used in a lithium-ion battery due to the use according to the invention, also at low outside temperature, is extremely beneficial for lithium ion batteries.

In one embodiment, the separator comprises the electrolyte according to the invention according to the second aspect. Preferably, then the separator is impregnated with the electrolyte.

In one embodiment, the electrolyte containing the comb polymer is present in the separator as a solid electrolyte. Also preferred is an embodiment in which the separator forms a polymer electrolyte together with the lithium salt electrolyte.

According to a third aspect, the invention relates to a separator for a lithium-ion battery, wherein the separator comprises an electrolyte, characterized in that the electrolyte comprises a polymer having a carbon backbone and at least 5, preferably at least 10 carbon side chains attached to the backbone the carbon backbone of the polymer is obtainable by polymerization of olefinic monomer units, wherein the number of side chains based on 100 monomer units of the main chain is 0.5 to 2.5, and the number of carbon atoms per side chain is independently 100 to 500. electrodes

The electrochemical cell of the invention has at least two electrodes, i. a positive and a negative electrode. In this case, both electrodes each have a material which can conduct lithium ions or intercalate lithium ions or metallic lithium.

The term "positive electrode" means the electrode that is capable of accepting electrons when the battery is connected to a load such as an electric motor. It represents the cathode in this nomenclature.

The term "negative electrode" means the electrode that is capable of delivering electrons when in use. It is the anode in this nomenclature. The electrodes preferably comprise inorganic material or inorganic compounds or substances which can be used for or in or on an electrode or as an electrode. These are preferably compounds or substances which, under the working conditions of the lithium ion battery, due to their chemical nature, conduct lithium ions or absorb (intercalate) and also release lithium ions or metallic lithium. In the prior art, such a material is also referred to as "active material" of the electrode. This material is preferably applied to a carrier for use in an electrochemical cell or battery, preferably a metallic carrier, preferably aluminum or copper. This carrier is also referred to as a "Abieiter" or as a "collector".

Positive electrode

As the active material for the positive electrode, there can be used any of materials known in the related art. Thus, there is no limitation with regard to the positive electrode in the sense of the present invention. In one embodiment, as the positive electrode active material, lithium phosphates may be used, preferably the molecular formula L1XPO4 with X = Mn, Fe, Co or Ni, or combinations thereof. Other suitable compounds are lithium manganate, preferably LiMn ₂ 0 ₄ , lithium cobaltate, preferably LiCo0 ₂ , lithium nickelate, preferably LiNi0 ₂ , or mixtures of two or more of these oxides, or their mixed oxides. To increase the conductivity further compounds may be present in the active material, preferably carbon-containing compounds, or carbon, preferably in the form of Leitruß or graphite. The carbon can also be introduced in the form of carbon nanotubes. Such additives are preferably applied in an amount of 1 to 6 wt .-%, preferably 1 to 3 wt .-% based on the applied to the carrier mass of the positive electrode.

The active material may also contain mixtures of two or more of the substances mentioned.

Negative electrode

Suitable materials for the negative electrode are selected from: lithium metal oxides such as lithium titanium oxide, carbonaceous materials, preferably graphite, synthetic graphite, graphene, carbon black, mesocarbon, doped carbon, fullerenes. As the electrode material for the negative electrode, niobium pentoxide, tin alloys, titanium dioxide, tin dioxide, silicon are also preferable.

binder

The materials used for the positive or negative electrode, such as the active materials, may be held together by one or more binders, which may or may not hold these materials on the electrode or on the Abieiter. Suitable binders are preferably styrene-butadiene rubber (SBR), polyvinylidene fluoride, polyethylene oxide, polyethylene polypropylene, polytetrafluoroethylene, polyacrylate, ethylene (propylene diene monomer) copolymer (EPDM) and blends and copolymers thereof.

In one embodiment, an electrode can also be coated with the electrolyte according to the invention.

In one embodiment, the electrode is coated with the electrolyte according to the invention. According to a fourth aspect, the invention relates to an electrode for a lithium ion battery, wherein the electrode comprises an electrolyte, characterized in that the electrolyte comprises a polymer having a carbon backbone and at least 5, preferably at least 10 carbon side chains attached to the main chain, wherein the main carbon chain of the polymer is obtainable by polymerization of olefinic monomer units, wherein the number of side chains based on 100 monomer units of the main chain is 0.5 to 2.5, and the number of carbon atoms per side chain is independently 100 to 500. battery

 The present invention also relates to a lithium ion battery comprising at least a negative electrode, a positive electrode, a separator between the negative and the positive electrodes, and an electrolyte.

The terms "lithium ion battery", "rechargeable lithium ion battery" and "lithium ion secondary battery" are used synonymously. The terms also include the terms "lithium battery", "lithium ion secondary battery" and "lithium ion cell". Thus, the term "lithium-ion battery" is used as a generic term for the abovementioned terms used in the prior art. It means both rechargeable batteries (secondary batteries) as well as non-rechargeable batteries (primary batteries). In particular, a "battery" in the context of the present invention also includes a single or single "electrochemical cell". Preferably, in a "battery" two or more such electrochemical cells connected together, either in series (ie in a row) or in parallel.

The battery according to the invention can be produced by methods known in the art, such as by laminating electrodes with the separator, preferably the separator according to the third aspect, with one or more electrodes, preferably with electrodes according to the fourth aspect. The battery may also be filled with an electrolyte, preferably with an electrolyte according to the second aspect.

Accordingly, in a fifth aspect, the present invention relates to a lithium ion battery comprising at least a negative electrode, a positive electrode, a separator between the negative and positive electrodes, and an electrolyte, characterized in that the battery is the electrolyte according to the second aspect of the invention, and / or a separator according to the third aspect, and / or a negative / and / or a positive electrode according to the fourth aspect.

Use of the erfindunasaemäßen battery

According to a sixth aspect, the invention relates to the use of the battery according to the invention or the battery produced by the method according to the invention.

Preferably, the lithium battery according to the invention can be operated at ambient temperatures of -40 to +100 ° C.

Preferred discharge currents of a battery according to the invention are greater than 100 A, preferably greater than 200 A, preferably greater than 300 A, more preferably greater than 400 A.

The battery / electrochemical cell according to the invention can be used for power supply for mobile information devices, tools, electrically operated Automobiles, used for automobiles with hybrid drive and for stationary energy storage.

Claims

claims 1. Use of at least one polymer having a main carbon chain and at least 5, preferably at least 10, carbon sides attached to the main chain, the main chain of the polymer being obtainable by polymerization of olefinic monomer units, the number of side chains being based on 100 monomer units of the main chain 0, Is 5 to 2.5, and the number of carbon atoms per side chain is independently from 00 to 500, characterized in that the polymer is used as the electrolyte component for a lithium ion battery. 2. Use according to claim 1, wherein the number of side chains based on 100 monomer units of the main chain is 0.6 to 2.0. 3. Use according to claim 1 or 2, wherein the number of side chains based on 100 monomer units of the main chain is 0.7 to 1.8. Use according to any one of the preceding claims, wherein the number of carbon atoms per side chain is independently from 200 to 500. Use according to any one of the preceding claims, wherein the number of carbon atoms per side chain is independently from 350 to 450. 6. Use according to one of the preceding claims, wherein the polymer is added in an amount of 0.1 to 30 wt .-% of the electrolyte based on the total amount of the electrolyte. 7. Use according to one of claims 1 to 5, wherein the polymer is added in an amount of 50 to 98 wt .-% of the electrolyte based on the total amount of the electrolyte. 8. An electrolyte for a lithium-ion battery, characterized in that the electrolyte comprises a polymer having a carbon backbone and at least 5, preferably at least 10 carbon side chains attached to the backbone, the backbone of the polymer being obtainable by polymerization of olefinic monomer units, said Number of side chains based on 100 monomer units of the main chain is 0.5 to 2, and the number of carbon atoms per side chain is independently 100 to 500. 9. Separator for a lithium-ion battery, characterized in that the separator comprises the electrolyte according to claim 8. 10. electrode for a lithium-ion battery, characterized in that the electrode comprises the electrolyte according to claim 8. 11. A lithium ion battery comprising at least: a negative electrode, a positive electrode, a separator between the negative and the positive electrodes, and an electrolyte, characterized in that the battery comprises the electrolyte according to claim 8, and / or a separator according to claim 9, and / or the negative electrode and / or the positive electrode is an electrode according to claim 10. 12. Use of the lithium-ion battery according to claim 1 1 for energy supply for mobile information equipment, tools, electrically powered cars, for automobiles with hybrid drive and for stationary energy storage.