DE102017212013A1 - Binder composition for electrochemical energy storage - Google Patents

Abstract

wobei R¹ und R² unabhängig voneinander ausgewählt sind aus:
einem linearen, verzweigten oder cyclischen, gesättigten oder ungesättigten Alkylrest mit 1 bis 15 Kohlenstoffatomen,
einem Arylrest mit 5 bis 15 Kohlenstoffatomen,
sowie Gemischen davon.
Die Verwendung der erfindungsgemäßen Bindemittelzusammensetzung wirkt sich positiv auf die Stabilität der Elektrode aus.

The invention relates to a binder composition for an electrode comprising at least one binder selected from polyacrylonitrile and polyvinylidene fluoride and mixtures thereof, and at least one solvent selected from at least one sulfoxide of the general formula (I):

wherein R ¹ and R ^{2 are} independently selected from:
a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms,
an aryl radical having 5 to 15 carbon atoms,
and mixtures thereof.
The use of the binder composition according to the invention has a positive effect on the stability of the electrode.

Description

State of the art

The invention relates to a binder composition for active material compositions of electrochemical energy stores, in particular electrochemical high-performance storage.

A conventional process for the preparation of electrodes comprises the preparation of a slurry (so-called slurry) of the active material of the electrode and optionally present additives in a solvent (active material slurry). Usually, a binder which is soluble in the solvent is previously added to the solvent. After applying the active material slurry to a substrate, the solvent is then removed to obtain a stable, coherent active material layer which is held together by the binder. Usually, a solution of carboxymethylcellulose (CMC) in water or a solution of polyvinylidene fluoride (PVdF) in N-methylpyrrolidone (NMP) is used as binder composition.

However, the use of water as a solvent often leads to undesirable side reactions with the active materials, especially in the field of electrochemical high energy storage. For example, water in combination with lithium titanates forms lithium hydroxide molecules, resulting in the formation of gases and thereby deterioration of the integrity of the active material composition of the electrode. In addition, CMC can attack the active material of the cathode during its decomposition. On the other hand, NMP is a highly toxic solvent, which requires costly measures for the protection of human health during handling of electrodes.

US 2016/0240854 A1 discloses a binder composition for cathodes comprising a graft copolymer of acrylonitrile and optionally other comonomers grafted onto polyvinyl alcohol. To prepare the active material slurry, N-methylpyrrolidone or dimethylsulfoxide is used as the solvent.

US 2015/280239 A1 discloses an aqueous binder composition for making electrodes. It proposes a composition comprising a polyvinylidene fluoride which is dispersed in an aqueous medium by adding a dispersant based on a (meth) acrylic polymer.

Disclosure of the invention

wobei R¹ und R² unabhängig voneinander ausgewählt sind aus:

• einem linearen, verzweigten oder cyclischen, gesättigten oder ungesättigten Alkylrest mit 1 bis 15 Kohlenstoffatomen,
• einem Arylrest mit 5 bis 15 Kohlenstoffatomen,
• sowie Gemischen davon.

The present invention relates to a binder composition for an electrode comprising at least one binder selected from polyacrylonitrile and polyvinylidene fluoride and mixtures thereof, and at least one solvent selected from at least one sulfoxide of the general formula (I):

wherein R ¹ and R ^{2 are} independently selected from:

• a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms,
• an aryl radical having 5 to 15 carbon atoms,
• and mixtures thereof.

It has been found that these solvents ensure good solubility of the binders and undergo little or no side reactions with the commonly used active materials.

In a preferred embodiment, R ^{1 is} selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms.

In one embodiment, R ^{1 is} selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms, and R ² is selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms and an aryl radical with 5 to 15 carbon atoms.

In a further preferred embodiment, R ¹ and R ^{2 are} independently selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms.

Especially suitable are solvents selected from a sulfoxide of the general formula (I) wherein R ¹ and R ^{2 are} independently selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso Butyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2-methylbutyl, 3-methylbutyl, 3-methylbut-2-yl, 2-methylbut-2-yl and a 2,2-dimethylpropyl radical.

Also preferred are binder compositions, wherein the solvent is at least one sulfoxide selected from dimethylsulfoxide, diethylsulfoxide, methylethylsulfoxide, di-n-propylsulfoxide, di-iso-propylsulfoxide, methyl-n-propylsulfoxide, ethylpropylsulfoxide, methyl-iso-propylsulfoxide, ethyliso- propylsulfoxide, di-n-butyl-sulfoxide, di-iso-butyl-sulfoxide, di-tert-butyl-sulfoxide, methyl-n-butyl-sulfoxide, methyl-iso-butyl-sulfoxide, methyl-tert-butyl-sulfoxide, ethyln -butyl-sulfoxide, ethyl-iso-butyl-sulfoxide, ethyl-tert-butyl-sulfoxide, n-propyl-n-butyl-sulfoxide, n-propyl-iso-butyl-sulfoxide, n-propyl-tert-butyl-sulfoxide iso-propyl-n-butyl-sulfoxide, iso-propyl-iso-butyl-sulfoxide, iso-propyl-tert-butyl-sulfoxide or a mixture thereof.

In a particularly preferred embodiment, the invention relates to a binder composition comprising at least one binder selected from polyacrylonitrile and polyvinylidene fluoride and mixtures thereof and at least one solvent selected from a sulfoxide of the general formula (I), wherein the solvent is selected from dimethyl sulfoxide, diethyl sulfoxide and Mixtures thereof. In a most preferred embodiment, the solvent is dimethylsulfoxide. These solvents are characterized by a very low toxicity, good solvent behavior towards the binders and a sufficiently high vapor pressure and to be removed from the Aktivmaterialaufschlämmung or the active material layer.

The binder composition further comprises at least one binder selected from selected from polyacrylonitrile and polyvinylidene fluoride and mixtures thereof. Preferably, the binder composition comprises the binder in an amount of from 0.1% to 20%, more preferably from 0.5% to 10%, and most preferably from 3% to 5% by weight, based on the total weight of the binder composition.

In one embodiment of the invention, the binder composition does not comprise polyacrylonitrile. In an alternative embodiment of the invention, the binder composition does not comprise polyvinylidene fluoride. In a further alternative embodiment of the invention, the binder composition comprises a mixture of polyacrylonitrile and polyvinylidene fluoride.

Polyvinylidene fluorides for the purposes of this invention are polymers which contain at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight and in particular at least 95% by weight, based on the total weight of the Polyvinylidenfluorids, are constructed from a repeat unit of the formula (II):

wobei R³, R⁴, R⁵ und R⁶ unabhängig voneinander ausgewählt sein können aus einem Wasserstoffatom, einem Fluoratom und einem C₁-C₅-Kohlenwasserstoffrest, insbesondere ein C₁-C₅-Alkylrest, welcher gegebenenfalls mit mindestens einem Fluoratom substituiert sein kann. In einer bevorzugten Ausführungsform stellt mindestens einer der Reste R³, R⁴, R⁵ und R⁶ ein Fluoratom dar. Die Comonomere können bis zu 50 Gew.-%, vorzugsweise bis zu 25 Gew.-%, stärker bevorzugt bis zu 10 Gew.-% und insbesondere bis zu 5 Gew.-% des Polyvinylidenfluorids, bezogen auf dessen Gesamtgewicht, ausmachen.Suitable comonomers are in particular those which form repeat units of the following general formula (IIb):

where R ³ , R ⁴ , R ⁵ and R ⁶ can be selected independently of one another from a hydrogen atom, a fluorine atom and a C ₁ -C ₅ -hydrocarbon radical, in particular a C ₁ -C ₅ -alkyl radical which optionally substituted by at least one fluorine atom can be. In a preferred embodiment, at least one of R ³ , R ⁴ , R ⁵ and R ^{6 represents} a fluorine atom. The comonomers may be up to 50% by weight, preferably up to 25% by weight, more preferably up to 10% by weight .-% and in particular up to 5 wt .-% of the polyvinylidene fluoride, based on its total weight account.

Polyacrylonitriles for the purposes of this invention are polymers which contain at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight and in particular at least 95% by weight, based on the total weight of the Polyacrylonitrile, are constructed from a repeat unit of the formula (IIIa):

wobei R⁷, R⁸, R⁹ und R¹⁰ unabhängig voneinander ausgewählt sein können aus einem Wasserstoffatom, einem -CN-Rest und einem C₁-C₅-Kohlenwasserstoffrest, insbesondere ein C₁-C₅-Alkylrest, welcher gegebenenfalls mit mindestens einem -CN-Rest substituiert sein kann. In einer bevorzugten Ausführungsform stellt mindestens einer der Reste R⁷, R⁸, R⁹ und R¹⁰ einen - CN-Rest dar. Die Comonomere können bis zu 50 Gew.-%, vorzugsweise bis zu 25 Gew.-%, stärker bevorzugt bis zu 10 Gew.-% und insbesondere bis zu 5 Gew.-% des Polyacrylnitrils, bezogen auf dessen Gesamtgewicht, ausmachen.Suitable comonomers are in particular those which form repeat units of the following general formula (IIIb):

where R ⁷ , R ⁸ , R ⁹ and R ¹⁰ can be selected independently of one another from a hydrogen atom, a -CN radical and a C ₁ -C ₅ -hydrocarbon radical, in particular a C ₁ -C ₅ -alkyl radical, which is optionally substituted by at least a -CN radical may be substituted. In a preferred embodiment, at least one of R ⁷ , R ⁸ , R ⁹ and R ^{10 represents} a --CN radical. The comonomers may be up to 50% by weight, preferably up to 25% by weight, more preferably up to to 10 wt .-% and in particular up to 5 wt .-% of the polyacrylonitrile, based on the total weight account.

The invention also provides the use of a binder composition according to the invention for producing an electrode, wherein the electrode comprises at least one binder selected from polyacrylonitrile and polyvinylidene fluoride, at least one active material, and optionally conductive additives.

As the active material, any conventional active material may be used in principle, as far as it is used to prepare positive or negative electrodes, i. Cathodes or anodes, of electrochemical energy storage is suitable. Electrochemical energy stores in the context of this invention are, in particular, electrochemical cells which comprise lithium-containing active materials or highly porous carbons, in particular lithium-ion batteries, supercapacitors and hybrid supercapacitors based on lithium-containing active materials.

Suitable active materials for the negative electrode include both static capacitive active materials and electrochemical redox active materials or mixtures thereof. A suitable static capacitive active material in the sense of this invention is carbon in its various forms, such as activated carbon, activated carbon fibers, graphene and carbon nanotubes. Carbon modifications are preferably used, in particular activated carbon. A suitable electrochemical redox-active material for the negative electrode in the context of this invention is a material which is known from electrochemical secondary batteries, in particular lithium-ion batteries, and is suitable for initiating a reversible electrochemical or faradic lithium-ion intercalation reaction or a lithium Form an ion intercalation compound. Suitable electrochemical redox active materials for the negative electrode are in particular lithium titanates (LTO) such as Li ₄ Ti ₅ O ₁₂ , but also lithium vanadium phosphates such as Li ₃ V ₂ (PO ₄ ) ₃ .

Suitable active materials for the positive electrode include both static capacitive active material and electrochemical redox active materials or mixtures thereof. With regard to the static capacitive material of the positive electrode, all statements on the negative electrode apply accordingly. The active materials mentioned there are also suitable for the positive electrode.

Suitable electrochemical redox active materials for the positive electrode are, for example, lithiated intercalation compounds which are capable of reversibly taking up and releasing lithium ions. The positive active material may comprise a composite oxide containing at least one metal selected from the group consisting of cobalt, magnesium, nickel, and lithium.

One embodiment of the present invention comprises a positive electrode active material comprising a compound of the formula LiMO ₂ wherein M is selected from Co, Ni, Mn, Cr or mixtures of these and mixtures of these with Al. In a preferred embodiment, wherein the cathode active material is a material comprising nickel, ie LiNi ₁ - _x M _'x O _2, wherein M' is selected from Co, Mn, Cr and Al, and 0 ≤ x <. 1 Examples include lithium-nickel-cobalt-aluminum-oxide cathodes (eg LiNi ₀ , ₈ Co ₀ , ₁₅ Al ₀ , ₀₅ O ₂ , NCA) and lithium-nickel-manganese-cobalt-oxide cathodes (eg LiNi ₀ , ₈ Mn _0.1 Co _0.1 O ₂ ; NMC (811) or LiNi _0.33 Mn _0.33 Co _0.33 O ₂ ; NMC (111)).

Furthermore, as preferred positive active materials, mention may be made of overlaid layered oxides which are known to the person skilled in the art. Examples are Li _{1 + x} Mn _2-y M _y O ₄ where x ≤ 0.8, y <2; Li ₁ + _x Co _{1 -y} M _y O ₂ where x ≤ 0.8, y <1; Li _{1 + x} Ni _{1 -yz} Co _y M _z O ₄ where x ≤ 0.8, y <1, z <1 and y + z <1. In the aforementioned compounds, M may be selected from Al, Mg and / or Mn.

In particular, two or more of the positive active materials may also be used in combination with each other. A preferred embodiment comprises, for example, compounds of the formula n (Li ₂ MnO ₃ ): n-1 (LiNi _x M ' _x O ₂ ) where M' is selected from Co, Mn, Cr and Al and 0 <n <1 and 0 <x <1.

Furthermore, in particular spinel compounds (eg LiMn ₂ O ₄ ), olivine compounds (eg LiFePO ₄ ), silicate compounds (eg Li ₂ FeSiO ₄ ), tavorite compounds (eg LiVPO ₄ F), Li ₂ MnO ₃ , Li _1.17 Ni _0.17 Co _0.1 Mn _0.56 O ₂ and Li ₃ V ₂ (PO ₄ ) ₃ as suitable positive active materials.

Particularly preferred active materials are activated carbon, Li ₄ Ti ₅ O ₁₂ , LiMn ₂ O ₄ and Li ₃ V ₂ (PO ₄ ) ₃ .

1. (a) Bereitstellen einer Aktivmaterialaufschlämmung, umfassend mindestens ein Bindemittel, ausgewählt aus Polyacrylnitril, Polyvinylidenfluorid oder einem Gemisch davon, mindestens ein Lösungsmittel ausgewählt aus einem Sulfoxid der allgemeinen Formel (l):
   
   wobei R¹ und R² unabhängig voneinander ausgewählt sind aus einem linearen, verzweigten oder cyclischen, gesättigten oder ungesättigten Alkylrest mit 1 bis 15 Kohlenstoffatomen, einem Arylrest mit 5 bis 15 Kohlenstoffatomen, oder einem Gemisch davon; und mindestens ein Aktivmaterial, sowie gegebenenfalls Leitzusätze;
2. (b) Aufbringen der Aktivmaterialaufschlämmung auf mindestens eine Substratoberfläche; und
3. (c) Entfernen des Lösungsmittels aus der Aktivmaterialaufschlämmung, um eine Aktivmaterialschicht zu bilden.

The invention also provides a process for producing an electrode, comprising the steps:

1. (a) providing an active material slurry comprising at least one binder selected from polyacrylonitrile, polyvinylidene fluoride or a mixture thereof, at least one solvent selected from a sulfoxide of the general formula (I):
   
   wherein R ¹ and R ^{2 are} independently selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms, an aryl radical having 5 to 15 carbon atoms, or a mixture thereof; and at least one active material, and optionally lead additives;
2. (b) applying the active material slurry to at least one substrate surface; and
3. (c) removing the solvent from the active material slurry to form an active material layer.

The provision of the active material slurry is achieved, for example, in such a way that the active material (s) and optionally used additives such as, in particular, conductive additives (for example graphite or carbon black) are premixed dry in a mixer. In another mixer, the binder (s) is dissolved in the solvent or solvent mixture. Subsequently, the binder solution is added to the active material mixture and the ingredients are intimately mixed to obtain the active material slurry. This step can be wholly or partly at an elevated ambient temperature (eg in the range of 30 ° C to 100 ° C) to increase the solubility of the binder in the solvent and / or to reduce the viscosity of the solvent or solvent-containing binder composition ,

In an alternative embodiment, the active material or the active materials are first dry premixed with the binder and any additives used, in particular conductive additives (for example graphite) in a mixer. Subsequently, the solvent is added to the binder-containing active material mixture, and the ingredients are intimately mixed to obtain the active material slurry. This step can be wholly or partly at an elevated ambient temperature (eg in the range of 30 ° C to 100 ° C) to increase the solubility of the binder in the solvent and / or to reduce the viscosity of the solvent or solvent-containing binder composition ,

It will be appreciated by those skilled in the art that the order and type of blending of the constituents of the active material slurry may be arbitrary and adapted to the particular process as long as the resulting active material slurry comprises all ingredients. Preferably, the active material slurry, based on the total weight of the active material slurry, comprises from 1 to 50% by weight, especially from 5 to 40% by weight, of solvent. This allows good wetting of the active material with the binder composition. Nevertheless, the resulting active material slurry is sufficiently strong to be subsequently controllably applied to a substrate surface without deliquescing.

The active material slurry is then applied to at least one substrate surface. This can be done by any method known to those skilled in the art, in particular by doctoring, extruding and / or calendering.

Preferably, the substrate surface is at least one surface of a current collector. The current collector is preferably made of an electrically conductive material, in particular a metal such as aluminum, nickel, copper, and alloys of these metals with each other or with other metals.

In an alternative embodiment, the substrate surface may be the surface of a non-electrically conductive material, for example a non-electrically conductive plastic. Thus, a freestanding active material layer comprising at least one binder can be formed, which can then be applied to a current collector.

The removal of the solvent is preferably carried out at an elevated ambient temperature and / or a reduced ambient pressure. For example, an ambient temperature in a range of 30 ° C to 200 ° C, especially 50 ° C to 150 ° C is applied. The ambient pressure is selected, for example, in a range of 0.01 bar to 1 bar, preferably in a range of 0.1 to 0.7 bar.

The electrode obtained in this way can advantageously be used in an electrochemical energy store. The invention thus also relates to the electrode obtained by the process described and the electrochemical Energy storage, which comprises at least one electrode obtained by the described method. The electrochemical energy store comprises the conventional further components, in particular electrolytes and separators. These are known to the person skilled in the art and are selected within the framework of his specialist knowledge.

Advantages of the invention

The binder composition according to the invention is characterized in that it does not or only to a minor extent undergoes side reactions with the conventionally used active materials, in particular with activated carbon, Li ₄ Ti ₅ O ₁₂ , LiMn ₂ O ₄ and Li ₃ V ₂ (PO ₄ ) ₃ , In addition, the binder composition comprises little or no toxic compounds so that the health protection measures when handling the binder composition can be reduced compared to NMP-containing binder compositions. The resulting electrodes or the energy stores produced therefrom have a higher cycle stability compared to conventional electrodes.

list of figures

• 1 zeigt die Entladungskapazität verschiedener Elektroden über den Verlauf mehrerer Be- und Entlandungszyklen.

Embodiments of the invention will be explained in more detail with reference to a drawing and the following description:

• 1 shows the discharge capacity of different electrodes over the course of several loading and unloading cycles.

Embodiments of the invention

The invention will be illustrated by the following examples.

example 1

Production of a positive electrode

To prepare the positive electrode, a dry mixture of 3.25 g of LiMn ₂ O ₄ and 1.75 g of activated carbon as the active material and 0.25 g of carbon black as a conductive additive is prepared. Then 5.5 g of a 4.76% binder solution (polyvinylidene fluoride in dimethyl sulfoxide) and 5.4 g of pure dimethyl sulfoxide are added and mixed intimately. The suspension obtained is poured by means of a doctor blade method directly onto a current collector with a layer thickness of about 100 microns to a positive electrode and dried.

Production of the negative electrode

To prepare the negative electrode, a dry mixture of 3.7 g of Li ₄ Ti ₅ O ₁₂ as the active material and 1 g of carbon black as a conductive additive is prepared. Then 12.5 g of a 2% binder solution (polyvinylidene fluoride in dimethyl sulfoxide) and 6 g of pure dimethyl sulfoxide are added and mixed intimately. The suspension obtained is poured by means of a doctor blade method directly onto a current collector with a layer thickness of about 100 microns to a positive electrode and dried.

The electrodes are joined together with a cellulose-based separator in a housing. An electrolyte comprising a lithium salt (LiClO ₄ ) and an aprotic solvent (acetonitrile) is charged into the housing. The housing is closed so as to form an electrochemical cell.

Example 2

An electrochemical cell is prepared as described in Example 1, except that the positive electrode is fabricated using polyacrylonitrile as a binder (5.5 g of a 4.76% solution of polyacrylonitrile in dimethylsulfoxide).

Comparative Example 1

An electrochemical cell is prepared as described in Example 1 except that the positive electrode is fabricated using polytetrafluoroethene (PTFE) as a binder with NMP as the solvent.

Comparative Example 2

An electrochemical cell is prepared as described in Example 1 except that the positive electrode is made using carboxymethyl cellulose and styrene-butadiene rubber as a binder with water as the solvent.

The normalized discharge capacities ( C ) of the electrochemical cells of Example 1 (curve 1 ), of Example 2 (curve 2 ), and Comparative Example 1 (curve 3 ) and Comparative Example 2 (curve 4 ) was determined over several charging and discharging cycles n. The results are in 1 shown. The abscissa axis shows the number of charging and discharging cycles n. On the ordinate axis is the normalized discharge capacity C shown. The output value at n = 0 is normalized to 1. It can be clearly seen that the examples according to the invention have significantly lower discharge capacity losses than the comparative example.

The invention is not limited to the embodiments described herein and therein highlighted aspects. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• US 2016/0240854 A1 [0004]
• US 2015280239 A1 [0005]

Claims (10)

A binder composition for an electrode, comprising at least one binder selected from polyacrylonitrile and polyvinylidene fluoride and mixtures thereof, and at least one solvent selected from at least one sulfoxide of the general formula (I):

wherein R ¹ and R ^{2 are} independently selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms, an aryl radical having 5 to 15 carbon atoms, and mixtures thereof. Binder composition according to Claim 1 wherein R ¹ and R ^{2 are} independently selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms. Binder composition according to Claim 1 or 2 wherein R ¹ and R ^{2 are} independently selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, Pentyl radical, a 3-pentyl radical, a 2-methylbutyl radical, a 3-methylbutyl radical, a 3-methylbut-2-yl radical, a 2-methylbut-2-yl radical, and a 2,2-dimethylpropyl radical. Binder composition according to one of Claims 1 to 3 wherein the solvent is selected from dimethylsulfoxide, diethylsulfoxide and mixtures thereof. Binder composition according to one of Claims 1 to 4 wherein the binder composition comprises the binder in an amount of 0.1 to 20% by weight, more preferably 0.5 to 10% by weight and especially 3 to 5% by weight, based on the total weight of the binder composition. Use of a binder composition according to any one of Claims 1 to 5 for producing an electrode, wherein the electrode comprises at least one binder selected from polyacrylonitrile and polyvinylidene fluoride, at least one active material, and optionally conductive additives. Use after Claim 6 wherein the active material is at least one selected from activated carbon, Li ₄ Ti ₅ O ₁₂ , LiMn ₂ O ₄ and Li ₃ V ₂ (PO ₄ ) ₃ . A method of making an electrode comprising the steps of: (a) providing an active material slurry comprising at least one binder selected from polyacrylonitrile, polyvinylidene fluoride or a mixture thereof, at least one solvent selected from a sulfoxide of general formula (I):

wherein R ¹ and R ^{2 are} independently selected from a linear, branched or cyclic, saturated or unsaturated alkyl radical having 1 to 15 carbon atoms, an aryl radical having 5 to 15 carbon atoms, or a mixture thereof; and at least one active material, and optionally lead additives; (b) applying the active material slurry to at least one substrate surface; and (c) removing the solvent from the slurry of active material to form an active material layer. Electrode obtained by a method according to Claim 8 , Electrochemical energy store, comprising at least one electrode after Claim 9 ,

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