EP3695449A1

EP3695449A1 - Cathode composition for lithium-ion battery, preparation process thereof, cathode and lithium-ion battery incorporating same

Info

Publication number: EP3695449A1
Application number: EP18808408.1A
Authority: EP
Inventors: Bruno Dufour; Marc Zimmermann; Ksenia ASTAFYEVA; Mélanie LECLERC
Original assignee: Hutchinson SA
Current assignee: Hutchinson SA
Priority date: 2017-10-09
Filing date: 2018-09-27
Publication date: 2020-08-19
Also published as: CN111512477B; JP2020537294A; FR3072213A1; KR20200083484A; US20200358095A1; US11817579B2; CN111512477A; WO2019073140A1

Abstract

The invention relates to a cathode composition for use in a lithium-ion battery, a process for preparing this composition, such a cathode and a lithium-ion battery incorporating this cathode. The composition comprises an active material which comprises an alloy of lithiated oxides of nickel, cobalt and aluminium, an electrically conductive filler and a polymeric binder, and is such that said polymeric binder comprises at least one modified polymer (Id2) which is the product of a thermal oxidation reaction of a starting polymer and which incorporates oxygenated groups comprising CO groups, the composition being able to be obtained by the melt route and without solvent evaporation, being the product of said thermal oxidation reaction applied to a precursor mixture comprising said active material, said electrically conductive filler, said starting polymer and a sacrificial polymeric phase.

Description

CATHODE COMPOSITION FOR LITHIUM-ION BATTERY, PROCESS FOR PREPARING THE SAME, CATHODE AND BATTERY

The present invention relates to a cathode composition that can be used in a lithium-ion battery, to a process for preparing this composition, to such a cathode and to a lithium-ion battery, the cell or each cell of which incorporates this cathode. There are two main types of lithium storage batteries: lithium metal batteries, where the negative electrode is composed of lithium metal (a material that poses safety problems in the presence of a liquid electrolyte), and lithium-ion batteries. ion, where the lithium remains in the ionic state.

Lithium-ion batteries consist of at least two faradic conducting electrodes of different polarities, the negative or anode electrode and the positive electrode or cathode, electrodes between which is a separator which consists of an electrical insulator impregnated with an aprotic electrolyte based on Li ⁺ cations ensuring the ionic conductivity. The electrolytes used in these lithium-ion batteries are usually constituted by a lithium salt, for example of formula LiPF ₆ , LiAsF ₆ , L1CF3SO3 or L1CIO4, which is dissolved in a mixture of non-aqueous solvents such as acetonitrile, tetrahydrofuran or most often a carbonate for example of ethylene or propylene.

A lithium-ion battery is based on the reversible exchange of the lithium ion between the anode and the cathode during charging and discharge of the battery, and it has a high energy density for a very low mass thanks to to the physical properties of lithium.

The active material of the anode of a lithium-ion battery is designed to be the seat of a reversible insertion / deinsertion of lithium and is typically made of graphite (theoretical capacity of 370 mAh / g and redox potential of 0.05 V with respect to the Li ⁺ / Li couple) or alternatively of oxides mixed metals among which there are lithiated titanium oxides of formula Li Ti ₅ Oi 2, for example. As for the active ingredient of the cathode, it is usually constituted:

an oxide of at least one transition metal such as alloys known as "NMC" of lithiated oxides of nickel, manganese and cobalt or alloys known as "NCA" of lithiated oxides of nickel, cobalt and aluminum, or

- a lithium iron phosphate.

These active materials allow a reversible insertion / disinsertion of lithium in the anode and cathode, and the higher their mass fractions are there, the greater the capacitance of the electrodes.

These electrodes must also contain an electrically conductive compound, such as carbon black and, to give them sufficient mechanical cohesion, a polymeric binder.

The lithium-ion battery electrodes are most often manufactured by a liquid process comprising successively a step of dissolving or dispersing the ingredients of the electrode in a solvent, a step of spreading the solution or dispersion obtained on a metal current collector, then finally a step of evaporation of the solvent. Processes using an organic solvent (such as that presented in US-A1-2010 / 0112441) have drawbacks in the fields of environment and safety, in particular the fact that it is necessary to evaporate quantities. These solvents are toxic or flammable. As for the processes using an aqueous solvent, their major disadvantage is that the electrode must be dried very thoroughly before it can be used, the traces of water limiting the useful life of lithium batteries. For example, CN 106450201 A describes a process for the liquid manufacture of a lithium-ion battery cathode, which teaches the active use of a combined NCA lithiated oxide alloy. to another lithiated cobalt oxide (LCO) alloy, and as a binder a polyvinylidene difluoride (PVDF). In the past, it has therefore been sought to manufacture electrodes for lithium-ion batteries without the use of solvents, in particular by means of melt processing techniques (for example by extrusion). Unfortunately, these molten processes generate major difficulties in the case of these batteries which require a mass fraction of active material in the polymer mixture of the upper electrode to 85% so that it has sufficient capacity within the drums. However, at such levels of active ingredient, the viscosity of the mixture becomes very high and entails risks of over-heating of the mixture and loss of mechanical cohesion after its implementation. US-A-5,749,927 discloses a method for the continuous preparation by extrusion of lithium polymer battery electrodes, which comprises mixing the electrode active material with an electrical conductor and a solid electrolyte composition comprising a polymeric binder such as a polyacrylonitrile (PAN), a PVDF or polyvinylpyrrolidone (PVP), a lithium salt and a propylene carbonate / ethylene carbonate mixture in large excess relative to this polymer. In this document, the mass fraction of active material present in the obtained anode polymer composition is less than 70%, being clearly insufficient for a lithium-ion battery.

The document WO-A1-2013/090487 teaches in its exemplary embodiments to use a PVDF as binder in a substantially solvent-free process for preparing a cathode composition for a lithium-ion battery whose active material is a lithium oxide alloy. NMC, depositing the cathode composition on a collector by friction. This document mentions, in addition to such a fluorinated polyolefin such as PVDF or a tetrafluoroethylene polymer, the possible use of unmodified polyolefins such as those prepared from ethylene, propylene or butylene.

US-B2-6,939,383 discloses using as a binder, in a lithium-ion battery electrode composition prepared without solvent in a multi-screw extruder, an ionically conductive polyether comprising a polar polymer of a alkene oxide such as a copolymer ethylene oxide-propylene oxide-allyl glycidyl ether, optionally combined with a non-ionically conductive polymer such as a PVDF, a PAN, PVP, an ethylene-propylene-diene terpolymer (EPDM) or a styrene-butadiene copolymer ( SBR) prepared in emulsion. In the sole exemplary embodiment of this document, the mass fraction of active material present in the electrode composition (a lithiated oxide of vanadium) is only 64.5%, which is clearly insufficient for a lithium-ion battery. .

US-B1-7,820,328 teaches using a thermoplastic polymer as a binder in a wet or dry lithium-ion battery electrode composition with thermal decomposition of a sacrificial polymer such as ethyl cellulose. , an acrylic resin, a polyvinyl alcohol, a polyvinyl butyral or a polyalkene carbonate. This decomposition is carried out under an inert atmosphere (i.e. non-oxidizing, eg under argon) for an anode composition and under either inert or oxidizing (e.g., air) atmosphere for a cathode composition. This document does not contain any example of the preparation of an anode or cathode composition with a specific active ingredient and a binder, indicating only that the conditions of decomposition of the sacrificial polymer under an inert or oxidizing atmosphere are carefully controlled. so as not to degrade the other ingredients of the composition such as the binder which is thus not modified and can be chosen from polyethylenes, polypropylenes and fluorinated polyolefins such as PVDF or PTFE. As for the active ingredient for the cathode, it may include lithiated oxides of nickel and / or cobalt.

EP-B1 -2 618 409 in the name of the Applicant teaches to prepare by melting and without evaporation of solvent a cathode composition for lithium-ion battery comprising at least 90% of active material by mass (consisting for example of a carbon-coated lithium-iron phosphate of formula C-LiFePO ₄ ), a polymeric binder consisting of a crosslinked diene elastomer such as a hydrogenated nitrile rubber (HNBR), and a non-volatile organic compound which can be used in the solvent of electrolyte of the battery. WO-A2-2015 / 124835 also in the name of the Applicant discloses a cathode composition for lithium-ion battery prepared by melting and without evaporation of solvent, using a sacrificial polymeric phase that is mixed an active material (which may be a lithiated oxide of a metal such as cobalt or manganese, or an alloy of NMC lithiated oxides), with a selected polymeric binder compatible with this phase for obtaining a precursor mixture, and then eliminated to obtain improved plasticization and fluidity during the implementation of the molten mixture despite a mass fraction of active ingredient in the composition greater than 80%. This document recommends to its embodiments to use a binder derived from a polar elastomer (HNBR or ethylene-ethyl acrylate copolymer) for its compatibility with the sacrificial phase, which is also polar, which is a polyalkene carbonate, to avoid macroseparation. of phases following the mixing of the ingredients and control the implementation, the integrity and the porosity of the composition, obtained by heat treatment in air oven of the precursor mixture to decompose the sacrificial phase. This document mentions alternatively the possible use of other binder polymers, subject to their compatibility with the chosen sacrificial phase, so that the latter is continuous in the precursor mixture in which the binder is in the dispersed or co-continuous phase, these other polymers may be chosen from polyolefins in the broad sense and elastomers such as polyisoprenes. This compatibility constraint therefore imposes the use of a binder of polarity similar to that of the sacrificial phase to avoid having two separate phases in the precursor mixture. As for the measured thickness of the cathode film obtained in the exemplary embodiments of this document, it is 50 μιτι.

The electrode compositions presented in these last two documents are generally satisfactory for a lithium-ion battery, however the Applicant has sought in recent research to further improve the electrochemical properties of cathode compositions obtained by melting with this high rate. actively. An object of the present invention is therefore to provide a new cathode composition for lithium-ion battery containing an active ingredient of more than 85% by weight, which is capable of being processed by melting and without solvent while being suitable. to impart to the cathode an improved surface density of energy compared with those obtained in the aforementioned prior art, with a reversibility in the first charge-discharge cycle, a capacitance and a cyclability (ie retention of the capacitance after a multitude of cycles) or at least not penalized.

This object is achieved in that the Applicant has surprisingly discovered that if one thermally oxidizes under controlled conditions a precursor mixture obtained by molten route and without solvent and comprising an active material specifically based on an alloy lithiated oxides of nickel, cobalt and aluminum (NCA), an electrically conductive filler, a starting polymer intended to form a binder and a sacrificial polymeric phase, then this starting polymer can advantageously be modified by CO 2 oxygen groups so that the binder thus obtained makes it possible, by a synergistic effect with the NCA alloy, to obtain a composition forming a cathode film with a thickness and thus a grammage much higher than in the prior art without penalizing the strength of the film at cycling, which gives the cathode a surface density of energy and robustness improved in operation in a lithium-ion battery.

In other words, a cathode composition according to the invention can be used in a lithium-ion battery, the composition comprising an active material which comprises a lithiated oxide alloy of nickel, cobalt and aluminum, an electrically conductive filler and a polymeric binder, and this composition is such that said polymeric binder comprises at least one modified polymer which is the product of a thermal oxidation reaction of a starting polymer and which incorporates oxygen groups comprising CO groups, the composition being capable of being obtained by melting and without solvent evaporation being the product of said applied thermal oxidation reaction a precursor mixture comprising said active material, said electrically conductive filler, said starting polymer and a sacrificial polymeric phase.

It will be noted that this functionalization of the binder combined with this active cathode mode comprising or consisting of an NCA-type alloy advantageously makes it possible to obtain very high thicknesses and therefore very high grammages (thicknesses that can exceed 150 μιτι and reach 250 μιτι, as explained below) for the cathode films deposited on the current collectors, and therefore high surface densities of energy, without penalizing the robustness of these films in operation in a lithium-ion battery.

It will also be noted that this synergistic effect between the polymer thus modified forming a binder and the active ingredient NCA is reflected in particular by an improved wettability of the cathode, which contributes to obtaining these improved electrochemical properties.

It will further be noted that the present invention differs from the prior art lithium-ion battery cathodes known from the Applicant, by its use of the NCA-type active material in a melt process without evaporation of solvent, and not by the liquid route which remains the most widespread to date.

According to another preferred feature of the invention, the composition, obtained by melt and without evaporation of solvent, is the product of said thermal oxidation reaction which is applied to said precursor mixture by decomposing said sacrificial polymeric phase under an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 ⁴ Pa and at an oxidation temperature between 150 ° C and 300 ° C (preferably between 190 ° C and 280 ° C), the oxygen of said atmosphere reacting with said starting polymer to produce said at least one modified polymer.

According to a first aspect of the invention, the composition is capable of forming a film deposited on a metal current collector forming the cathode with said film, with a thickness of said film equal to or greater than 90 μιτι and preferably between 150 μιτι and 250 μιτι.

As explained below in relation to the cathode according to the invention, this unusually high thickness can exceed 150 μιτι and reach 250 μιτι can be obtained in a single pass (ie a single sequence of mixing steps and deposit from a single precursor mixture), and it is advantageously accompanied by excellent resistance of the cathode film obtained at the appearance of cracks or cracks in cycling in the lithium-ion battery.

In a general manner, said sacrificial phase may comprise any polymer preferably having a thermal decomposition temperature that is at least 20 ° C. lower than that of the binder, and even more preferably at least one polymer of an alkene carbonate.

According to a preferred embodiment of the invention, said sacrificial polymeric phase may comprise at least one poly (alkene carbonate) polyol having end groups of which more than 50% (or even more than 80%) in moles comprise hydroxyl functions. .

Advantageously according to this preferred embodiment, said at least one poly (alkene carbonate) polyol may be a linear aliphatic diol chosen from poly (ethylene carbonate) diols and poly (propylene carbonate) diols having a weight average molecular weight Mw between 500 g. / mol and 5000 g / mol, preferably between 700 g / mol and 2000 g / mol.

By way of example, it is advantageous to use a poly (propylene carbonate) diol of the following formula:

According to an example of said preferred embodiment, said sacrificial polymeric phase comprises:

said poly (alkene carbonate) polyol having a weight average molecular weight Mw of between 500 g / mol and 5000 g / mol, preferably according to a mass fraction in said phase of less than 50% (for example between 25% and 45%), and

a poly (alkene carbonate) with a molecular mass Mw of between 20,000 g / mol and 400,000 g / mol, preferably in a mass fraction in said phase greater than 50% (for example between 55% and 75%).

It will be noted that this minority presence in mass, in the sacrificial phase, of the poly (alkene carbonate) polyol of Mw of between 500 and 5000 g / mol makes it possible, unexpectedly, to improve the plasticization and the fluidity of the precursor mixture when it is set. implemented in the molten state and the mechanical strength of the composition obtained, in comparison with a majority presence in mass in said phase of this poly (alkene carbonate) polyol.

Even more advantageously according to said preferred embodiment of the invention, the composition may also comprise a polysiloxane or polyisocyanate reactive compound, said at least one poly (alkene carbonate) polyol then being functionalized by grafting onto said siloxane group end groups. or isocyanates which are derived from said reactive compound and which block these end groups.

It will be noted that the interaction of this reactive compound with the sacrificial polymeric phase comprising this poly (alkene carbonate) polyol which is thus modified by grafting said compound makes it possible to solve a technical problem inherent in the use of NCA alloys, which resides in the fact that the NCAs catalyze an undesirable degradation of this sacrificial phase within the precursor mixture (ie before thermal decomposition of this phase), when this mixture is kept at room temperature (eg between 20 and 25 ° C). This problem of stability of the precursor mixture, which softens and looses its cohesion due to the beginning of depolymerization of the poly (alkene carbonate) polyol catalyzed by the NCA, generally occurs after a few hours of storage at room temperature, typically after about 6 hours for some NCAs. In other words, said reactive compound of the invention makes it possible to carry out the process of the invention without having to immediately submit (ie within a few hours of its preparation) the precursor mixture to said oxidation reaction. to eliminate the sacrificial phase and modify the starting polymer of the binder, making it possible to preserve the precursor mixture during an increased lifetime, for example equal to or greater than two days, thanks to the blocking of the chain ends of the poly (alkene carbonate) ) polyol by this compound which thus performs a function of stabilizing the mixture by opposing the depolymerization of the poly (alkene carbonate) polyol.

The Applicant has verified that the use of this reactive compound does not interfere with the subsequent degradation at high temperature of the poly (alkene carbonate) polyol.

Preferably, said reactive compound is chosen from organodisiloxanes and organodiisocyanates, being even more preferably an aliphatic disiloxane such as, for example, hexamethylene disiloxane (HMDS), or an aliphatic diisocyanate such as, for example, hexamethylene diisocyanate (HMDI).

It should be noted, however, that other aliphatic or even aromatic disiloxanes and diisocyanates are usable, subject to their ability to block the chain ends of the poly (alkene carbonate) polyol.

In general, a composition according to the invention may advantageously have a volume porosity, obtained by decomposition of said sacrificial polymeric phase, greater than 30% and preferably between 35% and 60%.

According to a first embodiment of the invention that may include said preferential mode, said starting polymer for said polymeric binder comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which little ( each have a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked by said thermal oxidation reaction to give said at least one modified polymer.

According to this first embodiment, said polymeric binder can advantageously consist of a NBR and / or a HNBR thus modified (s).

Preferably according to said first embodiment of the invention, said starting polymer comprises a said hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has:

a mass ratio of units derived from acrylonitrile equal to or greater than 44%, preferably equal to or greater than 48%, and / or

an iodine value, measured according to the ASTM D5902-05 standard, greater than 10%.

According to a second embodiment of the invention that may include said preferential mode, said starting polymer is an apolar aliphatic polyolefin and said at least one modified polymer derived therefrom has an oxygen atom mass content of between 2% inclusive. and 10%, preferably inclusive of between 3% and 7%.

According to this second embodiment, said polymeric binder may advantageously consist of at least one said apolar aliphatic polyolefin thus modified.

Advantageously, said oxygen groups of said at least one modified polymer comprise said CO groups and OH groups and preferably comprise C = O, C-O and -OH bonds which can define:

carbonyl groups preferably comprising carboxylic acid, ketone and optionally ester functional groups,

aldehyde groups, and

alcohol groups.

With reference to said second embodiment, it will be noted that these oxygenated groups coupled to this oxygen content by mass of 2% to 10% (content m / m, for example, measured by elemental analysis) result in the fact that the said at least one polymer modified by these groups is more polar than the apolar aliphatic polyolefin of departure, while remaining generally apolar (ie little polar) by this functionalization whose rate in the chain of the modified polyolefin is controlled so as to be sufficient (cf mass content in oxygen d at least 2%) but not too high (cf oxygen mass content of at most 10%) to obtain the targeted electrochemical properties including the reversibility at the first cycle, the capacity for example at a C / 2 regime or C / 5 and the cyclability of the electrode (ie its capacity retention).

Indeed, the Applicant has established in comparative tests that functionalization of the apolar aliphatic polyolefin is insufficient (ie with said mass content below 2% and for example zero, the apolar polyolefin is not modified in this case) or excessive (ie with said mass content greater than 10%) led to electrochemical properties at least partially unsatisfactory for a lithium-ion battery electrode, with in particular a first charge-discharge cycle efficiency and a capacity at a C regime Both are insufficient for this application.

It will also be noted that this particular functionalization of the apolar aliphatic polyolefin, both by said groups which characterize it and by its degree of functionalization by these groups, makes it possible, unexpectedly, in view of the teaching of the above-mentioned document WO-A2-2015 / 124835. to couple this apolar aliphatic polyolefin to a polar sacrificial phase (eg based on at least one alkene carbonate polymer), therefore incompatible with this apolar starting polyolefin. Also surprisingly, this apolar aliphatic polyolefin modified according to the invention can be used in a lithium-ion battery with a polar electrolyte of this battery, as shown below.

By "polyolefin" is meant in a manner known in the present description an aliphatic or aromatic polymer, homopolymer or copolymer ("copolymer" including by definition terpolymers), derived from at least one alkene and optionally additionally from a comonomer other than an alkene. By "aliphatic polyolefin" is meant a non-aromatic hydrocarbon polyolefin, which may be linear or branched, thus excluding in particular the polymers of an alkene oxide, alkene carbonate and homopolymers and copolymers derived from a vinylaromatic monomer such as styrene.

It will be noted that the apolar aliphatic polyolefins that can be used according to the invention exclude polyolefins with polar functional groups such as halogenated polyolefins, for example polyvinylidene polyfluorides or polyvinylchlorides (PVDF or PVDC), polyhexafluoropropylenes and polytetrafluoroethylenes (PTFE).

Even more preferably, said apolar aliphatic polyolefin may be selected from the group consisting of homopolymers of an aliphatic olefin, the copolymers of at least two aliphatic olefins and their mixtures being preferably:

a linear or branched non-halogenated homopolymer of an aliphatic mono-olefin, which may be of type:

^* Thermoplastic, for example chosen from polyethylenes (eg low or high density, respectively LDPE or HDPE), polypropylenes (PP), polybutene-1 and polymethylpentenes, or

^an elastomer, for example chosen from polyisobutylenes;

or

a linear or branched non-halogenated copolymer of two aliphatic mono-olefins, which can be of type:

^* Thermoplastic, for example selected from ethylene-octene (eg naming ELITE® 5230 G, are not limited to), ethylene-butene, propylene-butene and ethylene-butene-hexene, or

an elastomer, for example chosen from copolymers of ethylene and of an alpha-olefin such as ethylene-propylene copolymers (EPM) and ethylene-terpolymers; propylene-diene (EPDM, for example EPDM with the name Vistalon® 8600 (Exxon Mobil) or Nordel IP 5565 (Dow)). According to said second embodiment, said apolar aliphatic polyolefin is advantageously not cross-linked and may have a mass ratio of units derived from ethylene of greater than 50%, being for example a copolymer of ethylene and 1-octene and / or an EPDM.

It should be noted that these apolar aliphatic polyolefins, such as EPDM or polyethylenes, have the advantage of being inexpensive, especially in comparison with the HNBRs and the ethylene-ethyl acrylate copolymers used in the prior art in the melted process.

According to a second aspect of the invention, the composition may comprise:

according to a mass fraction greater than 85% and preferably equal to or greater than 90%, said active material which comprises and advantageously consists of a said alloy of lithium nickel, cobalt and aluminum oxides of the NCA type,

said polymeric binder having a mass fraction of less than 5%, preferably of between 1% and 4%, and

said electrically conductive filler, which is chosen from the group consisting of carbon blacks, cellulose-derived carbons, expanded graphites, carbon fibers, carbon nanotubes, graphenes and their mixtures, according to a mass fraction between 1% and 10%, preferably between 6% and 9%,

said sacrificial polymeric phase being at least partially removed by said thermal oxidation applied to said precursor mixture.

It will be noted that this mass fraction of more than 85% of said active material in the cathode composition contributes to imparting high performance to the lithium-ion battery incorporating it. It will also be noted that it is possible to incorporate one or other specific additives in a cathode composition according to the invention, in particular in order to improve or optimize its manufacturing process. A cathode according to the invention of lithium-ion battery is characterized in that the cathode comprises a current metal collector and a film covering it formed of a composition as defined above, said film having a thickness equal to or greater than 90 μιτι obtained in a single pass preparation of said precursor mixture melt and without solvent and being able to resist the appearance of cracks or cracks after several charge-discharge cycles of the cathode within the lithium-ion battery.

According to said first aspect of the invention, said film may advantageously have in a single pass a thickness of between 150 μιτι and 250 μιτι and be able to resist the appearance of said cracks or cracks after 20 cycles and preferably 40 charge cycles - Discharge of the cathode for example at a rate of C / 2.

Advantageously, the cathode may be adapted to confer on the lithium-ion battery incorporating a first charge-discharge efficiency greater than 70% when said first charge-discharge cycle is for example implemented between 4.3 V and 2.5 V at a rate of C / 5.

Also advantageously, the cathode may be able to confer on the lithium-ion battery incorporating it, for cycles implemented between 4.3 V and 2.5 V:

a capacity at a C / 5 rate greater than 140 mAh / g of cathode, and / or

a capacity at a C / 2 rate greater than 100 mAh / g of cathode, preferably greater than 130 mAh / g of cathode, and / or

a retention rate of capacity at C / 2 after 20 cycles and preferably further after 40 cycles relative to the first cycle, which is equal to or greater than 95%. A lithium-ion battery according to the invention comprises at least one cell comprising an anode, a cathode and an electrolyte based on a lithium salt and a non-aqueous solvent, and it is characterized in that the cathode is such that as defined above.

A method of preparation according to the invention of a cathode composition as defined above comprises successively:

a) melt-blending and without solvent, for example in an internal mixer or an extruder, ingredients of the composition comprising said active material, said starting polymer, said electrically conductive filler and said sacrificial polymeric phase, for the obtaining a precursor mixture of said composition,

b) a film deposit of said precursor mixture on a metal current collector, and

c) said thermal oxidation reaction of said film under an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 ⁴ Pa and at an oxidation temperature of between 150 ° C. and 300 ° C. for a period of variable oxidation (may vary from a few minutes to 30 minutes or more) for the total or partial elimination of said sacrificial phase and obtaining said at least one modified polymer.

It will thus be noted that this sacrificial phase may be absent from the composition obtained or present therein in a degraded residual form.

According to said first aspect of the invention, steps a), b), c) can be carried out in a single pass by a single film obtained from said precursor mixture, this film then having a thickness equal to or greater than 90 μιτι and preferably between 150 μιτι and 250 μιτι.

According to said preferred embodiment of the invention, said sacrificial phase used in this process may comprise said at least one poly (alkene carbonate) polyol with end groups of which more than 50% (or even more than 80%) in moles comprise functional groups. hydroxyl, preferably a linear aliphatic diol selected from poly (ethylene carbonate) diols and poly (propylene carbonate) diols of molecular weight Mw between

500 g / mol and 5000 g / mol.

According to said example of said preferential mode, said sacrificial polymeric phase used in this method of the invention comprises:

said poly (alkene carbonate) polyol with a molecular mass Mw of between 500 g / mol and 5000 g / mol (liquid at ambient temperature and at atmospheric pressure), preferably with a mass fraction in said phase of less than 50%, and

a poly (alkene carbonate) with a molecular weight Mw of between 20,000 g / mol and 400,000 g / mol (solid at ambient temperature and at atmospheric pressure), preferably with a mass fraction in said phase greater than 50%.

As indicated above, this minority presence in mass in said poly (alkene carbonate) polyol phase of Mw between 500 and 5000 g / mol makes it possible to improve the plasticization and the fluidity of the precursor mixture and the mechanical strength of the composition which comes from it.

Advantageously according to said preferred embodiment of the invention, said ingredients mixed in step a) may further comprise said polysiloxane or polyisocyanate reactive compound which reacts during said mixing with said at least one poly (alkene carbonate) polyol by functionalizing it by grafting on said end groups of siloxane or isocyanate groups derived from said reactive compound, which is preferably selected from organodisiloxanes, such as aliphatic disiloxanes, and organodiisocyanates, such as aliphatic diisocyanates.

As for the mass fraction of said reactive compound in the precursor mixture, it is preferably between 0.1% and 2%.

As explained above, the use of this reactive compound makes it possible to simplify the process by allowing preservation of the precursor mixture during an increased lifetime (eg at least two days), thanks to the blocking of the poly (alkene) chain ends. carbonate) by this compound which is opposed to the depolymerization of the poly (alkene carbonate) polyol and thus stabilizes this mixture at room temperature, waiting for the oxidative heat treatment.

In a general manner, step c) can advantageously be implemented by a controlled temperature rise of a starting temperature, preferably between 40 ° C. and 60 ° C., at said oxidation temperature and then by an isotherm at this oxidation temperature during said oxidation time, for thermally decomposing said sacrificial phase and modifying said starting polymer such that said at least one modified polymer has said oxygen groups comprising said CO groups.

With reference to said first and second modes of the invention, it will be noted that the said thermal oxidation reaction is thus controlled so that in the composition obtained, the said starting polymer is modified as specified above (eg with in this second embodiment , the mass content of oxygen atoms in the polymer modified with CO and OH oxygen groups which is between 2% and 10% inclusive). Indeed, this method of the invention requires precise control of said reaction to achieve this particular operation, adapting the conditions of temperature, pressure and thermal oxidation time to the selected starting polymer.

According to said first embodiment of the invention optionally including said preferential mode, said starting polymer used in step a) comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has (nt) each a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked in step c) by said thermal oxidation reaction.

It will be noted that the starting polymer according to this first mode is present in the precursor mixture of step a) without macroseparation of phases between binder and sacrificial phase when the latter is in accordance with said preferential mode (ie at least one poly (alkene carbonate) polyol). According to said second embodiment of the invention, said starting polymer used in step a) comprises an apolar aliphatic polyolefin preferably selected from the group consisting of thermoplastic and elastomeric homopolymers of an aliphatic mono-olefin, thermoplastic copolymers and elastomers of at least two aliphatic monoolefins and mixtures thereof, said apolar aliphatic polyolefin being modified in step c) to give said at least one modified polymer having an oxygen atomic mass content of between 2% and 10%, and in said precursor mixture obtained in step a).

It will be noted that the starting polymer according to this second mode is present in the precursor mixture of step a) with macroseparation of phases between the binder and the sacrificial phase thus forming two separate phases, when the sacrificial phase is in accordance with said preferred embodiment.

It will be noted that it is thus possible to advantageously dispense with any compatibilizing compound to obtain the composition of the invention, despite the incompatibility between said apolar aliphatic polyolefin and said polar polar sacrificial polymer phase.

Thus, said second embodiment of the invention goes against the teaching of the aforementioned document WO-A2-2015 / 124835, because it uses for the binder an apolar starting polymer not compatible with the polar sacrificial phase in said preferential mode (and also incompatible with the electrolyte also polar used for the battery), starting polymer which is an apolar aliphatic polyolefin (ie excluding in the family of polyolefins aromatic polyolefins and polar polyolefins) and which is modified in a manner very particular and controlled in the composition obtained after removal of the sacrificial phase, by adding these oxygenated groups such that said at least one modified polymer satisfies the aforementioned restricted range for its mass content of oxygen. Other features, advantages and details of the present invention will become apparent on reading the following description of several exemplary embodiments of the invention, given by way of nonlimiting illustration in relation to the attached drawing, in which:

FIG. 1 is a graph illustrating the absorbance spectra measured by Fourier Transform Infrared Spectroscopy (FTIR for short) showing the evolution of the absorbance as a function of the wavenumber of two elastomer films consisting of a first binder control consisting of an unmodified HNBR and a first binder according to the invention formed of the same modified HNBR, and

FIG. 2 is a graph illustrating the absorbance spectra measured by FTIR showing the evolution of the absorbance as a function of the wavenumber of two elastomeric films consisting of a second control binder formed of an unmodified EPDM and a second binder according to the invention formed from the same modified EPDM.

Control and according to the invention examples of lithium-ion battery cathodes prepared by the molten route: In all these examples, the following ingredients were used: a) as active ingredients, two NCA alloys of lithium nickel oxides, cobalt and aluminum (Targray) of respective grades

a1) SNCA01001; and

a2) SNCA04001;

(b) as conductive fillers, a Super C65 carbon black (Timcal) and a cellulose-derived CMC carbonaceous material (Pyrograph);

c) as a sacrificial polymeric phase, a blend of two polypropylene carbonates (PPCs): one Nover Converge® Polyol 212-10 denominated diol-liquid and diol, and the other QPAC® 40-denominated solid of Empower Materials, present in this phase sacrificial at respective mass fractions of about 65% - 35% or 35% - 65%;

d) as starting polymers for forming the binder: d1) an HNBR Zetpol® 0020 (Zeon Chemicals) having an acrylonitrile level of 50% and an iodine number of 23; and

d2) a terpolymer according to the invention EPDM Vistalon® 8600 (Exxon Mobil) having a mass content of ethylene of 58.0% and a level of ethylidene norbornene (ENB) of 8.9%;

e) as a stabilizing agent, hexamethylenedisiloxane (HMDS), Sigma Aldrich.

Protocol for casting cathodes by molten route:

Eight cathode compositions according to the invention 11-18 based on the ingredients a1) or a2), b), c), d1) or d2) and optionally e) (for the sole composition 12) were melted. ) by means of an internal mixer of Haake Polylab OS type, with a capacity of 69 cm ³ and at a temperature between 60 ° C and 75 ° C.

The mixtures thus obtained were calendered at room temperature using an external Scamex cylinder mixer until a thickness of 600 μιτι was obtained, then they were further calendered at 70 ° C. to reach a thickness of 90 μιτι. at 250 μιτι. The resulting precursor mixtures were deposited on a carbon-coated aluminum collector using a 70 ° C sheet-fed calender.

The cathode precursor films thus prepared were placed in a ventilated oven in order to extract the sacrificial phase (solid and liquid CPAP). They were subjected to a controlled ramp temperature of 50 ° C to 250 ° C and an isotherm of 30 min. at 250 ° C by subjecting them to thermal oxidation in ambient air, to decompose this sacrificial phase and functionalize the corresponding binder d1) or d2).

In addition, an example of control composition C1 with the precursor mixture of composition 18 subjected to the same treatment was carried out. the precursor mixture of 18 but not according to the invention because under an inert atmosphere (ie non-oxidizing), in a rotary kiln under nitrogen with a nitrogen flow rate of 1 L / min.

Compositions according to the invention were thus obtained 11, 12, 13, 14, 16, 17 each comprising a binder consisting of said modified HNBR, and compositions according to the invention 15 and 18 each comprising a binder consisting of said modified EPDM, with respective mass fractions of the two liquid and solid CPPs in the sacrificial phase of about 65% -35% for 11 -12 and about 35% -65% for 13-18.

Table 1 below lists the characteristics of the precursor mixtures and compositions obtained (mass fractions).

Table 1:

The compositions obtained 11 -18 each had a mass fraction of active material, consisting of an alloy NCA, equal to 90%, and a mass fraction of binder modified according to the invention Id1) or Id2), respectively constituted of said HNBR or said EPDM, ranging from 1.8% (compositions I6-I8) to 3% (compositions 11-15).

The precursor mixture from which the composition 12 comprising a stabilizing agent (HMDS) was obtained could advantageously be stored at room temperature for more than 48 hours, effectively opposing the depolymerization of the solid CPAP liquid-CPAP sacrificial phase. to the action of the active ingredient NCA.

The volume porosity of the compositions 11 -13, 16 was 37.7%, that of the compositions 14, 15, 17 and 18 was higher (about 50%). Characterization of modified binders according to the invention:

The binders d1) and d2), unmodified and modified according to the invention, have been characterized during this process by the melt method, by the FTIR ("FTIR" technique for giving "Fourier transform infrared spectroscopy") giving absorbance spectra. depending on the wave number. For this purpose:

1) For the binder d1), a film consisting of said HNBR (Zetpol® 0020) 100 μιτι thick was deposited on copper, and treated for 30 minutes at 240 ° C in air. This film was then studied by IRTF in "ATR" mode (for "attenuated total reflectance" in English, i.e. attenuated total reflectance).

FIG. 1 shows the two spectra obtained S1 and S2, respectively before and after this annealing. The spectrum S2 after this annealing shows:

a slight decrease in the band at 2240 cm ^-1 , characteristic of the nitrile groups -C≡ N,

an appearance of a band around 1600 cm ^-1 attributed to the appearance of C = C and C = N bonds,

an appearance of a band around 1740 cm ^-1 attributed to the appearance of C = O groups, and

an appearance of a band between 3200 cm ^-1 and 3500 cm ^-1 , attributed to C-OH bonds.

These bands are characteristic of the partial oxidation of nitrile groups and the crosslinking of HNBR by oxidation / dehydration of these nitrile groups (which are much more numerous than the unsaturations resulting from butadiene because of the high level of ACN in the HNBR). as described under similar conditions, for example in Ogawa et al., Carbon, Vol 33, No.6 p783 or Dalton et al., Polymer 40 (1999) 5531-5543. 2) For the binder d2), five films of Cd2 100 μιτι thick were deposited on copper, by evaporation of a solution in heptane, formed of the binder d2) consisting of Vistalon® 8600 EPDM. The five Cd2 films thus deposited were then treated in a controlled manner for 30 minutes. at 250 ° C. under ambient air, so as to obtain five films Id2 modified binder according to the invention each comprising CO and OH groups modifying d2). The Cd2 and Id2 films were then studied by IRTF in "ATR" mode.

Figure 2 shows the spectrum of Vistalon® 8600 EPDM of a non-heat treated Cd2 film (Cd2 incorporating unmodified binder d2) and the spectrum of the same EPDM of the Cd2 film but treated at 250 ° C for 30 min. as indicated above, and it can be seen that the latter spectrum has EPDM thermo-oxidation characteristic bands such as C = O bonds at 1712 cm ^-1 , CO at 1163 cm ^-1 and -OH At 3400 cm ^-1, the mass ratio of oxygen atoms in each of the five Id2 films of this modified EPDM was measured by elemental analysis, and an average value of 5.9% was found for this rate. with a standard deviation of 0.29% for the five measurements.

Protocol for electrochemical characterization of cathodes 11 -18 according to the invention and control C1 prepared by molten route:

The cathodes (16 mm diameter, surface 2.01 cm ² ) were punched out and weighed. The mass of active material was determined by subtracting the mass of the bare current collector prepared under the same conditions (heat treatments). They were put in an oven directly connected to a glove box. They were dried at 100 ° C under vacuum for 12 hours and then transferred to the glove box (argon atmosphere: 0.1 ppm H ₂ O and 0.1 ppm O 2).

The button cells (CR1620 format) were then assembled using a lithium metal counter-electrode, a Cellgard 2500 separator and a LiPF6 EC / DMC battery grade electrolyte (50% / 50% by mass ratio). Batteries were characterized on a Biology VMP3 potentiostat, in constant current charge / discharge cycles between 4.3 V and 2.5 V. The diet was C / 5 considering the mass of active ingredient and a theoretical capacity of 170 mAh / g. In order to compare the performances of the different systems, the capacities (expressed in mAh per g of cathode) were evaluated during the first discharge for lithium deisertion (ie initial capacity after the first charge-discharge cycle), the second discharge (first cycle performance measurement), after 20 cycles and after 40 cycles, to calculate the retention rate (in%) defined by the capacity ratio at 20 or 40 cycles on the first cycle capacity at one same scheme (C / 2). In addition to the capacities at a C / 5 and C / 2 regime, the capacities at C, 2C and 5C regimes for these cathodes were measured (all these capacities being expressed in mAh per g of cathode).

Table 2 below gives the characterization results for the cathodes 11-18 in each cell thus obtained, it being specified that films of different thicknesses were obtained for each composition 14, 15, 16, 17, 18, and that the above-mentioned control test for the composition C1, resulting from the same precursor mixture as 18 but thermally degraded under a nitrogen (non-oxidizing) atmosphere, was furthermore carried out.

Table 2:

Thickness Yield Capacity Capacity Capacity Capacity to μητι - Cycle ¹ C / 5 to C / 2 ACAU ¹ to 2C to 5C to C / 2 Weight Cycle ¹ Cycle ¹ Cycle 1 ^Cycle ¹ cycle 20 ^th cycle - mg / cm ² (mAh / g) (mAh / g) (mAh / g) (mAh / g) (mAh / g) 40 ^th cycle

(MAh / g)

87 μηη 75% 133 110 46

95 μιτι 75% 126 81 -

90 μηη 75% 128 78 24

75 μιτι 78% 143 121

18 mg / cm ²

120 μηη 77% 140,117

25 mg / cm ²

76 μηη 80% 150 125

16 mg / cm ²

126 μηη 78% 143,110

28 mg / cm ²

78 μηη 76% 134 115 70 14

113 μηη 75% 121 95 24 4

142 μηη 75% 129 75 20 -

192 μηη 71% 102 28 9 -

67 μm 75% 113 96 73 -

70 μm 148 138 134- 132

124 μηη 75% 135 108 - -

218 μm 74% 120 41 9 -

89 μηη 76% 137 123 91 21

124 μm 75% 118 58 5 -

205 μm 73% 111 53 17 -

89 μηη No signal (capacity close to zero) Table 2 shows the obtaining of very high thicknesses, in particular for cathode compositions 16 to 18 (thicknesses greater than 150 μιτι, or even 200 μιτι), which generates also high surface energy densities for these cathodes according to US Pat. 'invention. It was verified that the cathode films of these compositions 11-18 according to the invention were free of cracks or cracks during cycling.

Table 2 also shows that these compositions 11 -18 of the invention make it possible to obtain high yields in the first cycle (greater than 70%) indicating satisfactory reversibility, and capacities at C / 5, C regimes. / 2, C, 2C and if appropriate 5C equally satisfactory.

Table 2 also shows a very satisfactory cyclability for the cathode film 17 of the invention having a thickness of 70 μιτι after 20 and even 40 cycles (see the rate of retention of capacity at C / 2 after 20 and 40 cycles which is greater than 95%).

More specifically, the tests with the compositions:

11 and 12 show that the use of HMDS in 12 as a stabilizing agent does not really penalize the electrochemical properties of cathode 12 with respect to 11;

11 and 13 show an improvement in the electrochemical properties of the cathode 11 obtained with a relative majority of liquid PPC with respect to the solid PPC, with respect to the cathode 13 obtained with a relative minority of liquid PPC with respect to the solid PPC;

14 and 15 show an improvement in the electrochemical properties of the cathode 15 obtained with a modified EPDM binder with respect to the cathode 14 obtained with a modified HNBR binder; and

16, 17 and 18 show a limited effect on the electrochemical properties of the thickness of the cathode films and the volume porosity of the compositions 17 and 18, much higher than that of the composition 16.

Claims

1) A cathode composition that can be used in a lithium-ion battery, the composition comprising an active material that comprises an alloy of lithiated oxides of nickel, cobalt and aluminum, an electrically conductive filler and a polymeric binder, characterized in that said polymeric binder comprises at least one modified polymer (Id2) which is the product of a thermal oxidation reaction of a starting polymer and which incorporates oxygen groups comprising CO groups, the composition being capable of being obtained by melting and without solvent evaporation being the product of said thermal oxidation reaction applied to a precursor mixture comprising said active material, said electrically conductive filler, said starting polymer and a sacrificial polymeric phase.

2) A composition according to claim 1, wherein the composition, obtained melt and without evaporation of solvent, is the product of said thermal oxidation reaction which is applied to said precursor mixture by decomposing said sacrificial polymeric phase in an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 ⁴ Pa and at an oxidation temperature between 150 ° C and 300 ° C, the oxygen of said atmosphere reacting with said starting polymer to produce said at least one modified polymer. 3) Composition according to claim 1 or 2, wherein the composition is capable of forming a film deposited on a metal current collector forming the cathode with said film, with a thickness of said film equal to or greater than 90 μιτι and preferably between 150 μιτι and 250 μιτι. 4) Composition according to one of the preceding claims, wherein said sacrificial polymeric phase comprises at least one poly (alkene carbonate) polyol having end groups of which more than 50 mol% include hydroxyl functions.

5) A composition according to claim 4, wherein said at least one poly (alkene carbonate) polyol is a linear aliphatic diol selected from poly (ethylene carbonate) diols and poly (propylene carbonate) diols having a weight average molecular weight of between 500 g / mol and 5000 g / mol, preferably between 700 g / mol and 2000 g / mol. The composition of claim 4 or 5, wherein said sacrificial polymeric phase comprises:

said poly (alkene carbonate) polyol having a weight-average molecular weight of between 500 g / mol and 5000 g / mol, preferably a mass fraction in said phase of less than 50%, and

a poly (alkene carbonate) having a weight-average molecular mass of between 20,000 g / mol and 400,000 g / mol, preferably in a mass fraction in said phase greater than 50%.

7) Composition according to one of claims 4 to 6, wherein the composition further comprises a polysiloxane or polyisocyanate reactive compound, said at least one poly (alkene carbonate) polyol being functionalized by grafting on said end groups of siloxane or isocyanate groups. from said reactive compound. 8) The composition of claim 7, wherein said reactive compound is selected from organodisiloxanes and organodiisocyanates, preferably being an aliphatic disiloxane or an aliphatic diisocyanate. 9) Composition according to one of the preceding claims, wherein the composition has a volume porosity, obtained by decomposition of said sacrificial polymeric phase, greater than 30% and preferably between 35% and 60%.

10) Composition according to one of claims 1 to 9, wherein said starting polymer for said polymeric binder comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which present (s) each a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked by said thermal oxidation reaction to give said at least one modified polymer.

The composition of claim 10, wherein said starting polymer comprises a said hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has:

an iodine value, measured according to the ASTM D5902-05 standard, greater than 10%. 12) Composition according to one of claims 1 to 9, wherein said starting polymer is an apolar aliphatic polyolefin and wherein said at least one modified polymer derived therefrom has an oxygen atomic mass content of between 2% and 10%, preferably inclusive of between 3% and 7%.

13) The composition according to claim 12, wherein said oxygenated groups of said at least one modified polymer comprise said CO groups and OH groups, and comprise C = O, C-O and -OH bonds defining:

aldehyde groups, and alcohol groups.

The composition of claim 12 or 13, wherein said apolar aliphatic polyolefin is selected from the group consisting of homopolymers of an aliphatic olefin, the copolymers of at least two aliphatic olefins and mixtures thereof being preferably:

a linear or branched non-halogenated homopolymer of an aliphatic monoolefin, of type:

^* Thermoplastic, for example chosen from polyethylenes, polypropylenes, polybutenes-1 and polymethylpentenes, or

^an elastomer, for example chosen from polyisobutylenes;

or

a linear or branched non-halogenated copolymer of two aliphatic mono-olefins, of type:

thermoplastic, for example chosen from ethylene-octene, ethylene-butene, propylene-butene and ethylene-butene-hexene copolymers, or

elastomer, for example chosen from copolymers of ethylene and an alpha-olefin such as ethylene-propylene copolymers (EPM) and ethylene-propylene-diene terpolymers (EPDM).

15) Composition according to claim 14, wherein said apolar aliphatic polyolefin is not crosslinked and preferably has a mass ratio of units derived from ethylene greater than 50%, being for example a copolymer of ethylene and 1 octene and / or EPDM.

16) Composition according to one of the preceding claims, wherein the composition comprises:

according to a mass fraction greater than 85% and preferably equal to or greater than 90%, said active ingredient which is consisting of a said alloy of lithium oxides of nickel, cobalt and aluminum type NCA,

17) Lithium-ion battery cathode, characterized in that the cathode comprises a current metal collector and a film covering it formed of a composition according to one of the preceding claims, said film having a thickness equal to or greater than 90 μιτι obtained in a single pass preparation of said precursor mixture melt and without solvent and being able to resist the appearance of cracks or cracks after several charge-discharge cycles of the cathode within the lithium-ion battery.

18) A cathode according to claim 17, wherein said film has a thickness of between 150 μιτι and 250 μιτι and is able to resist the appearance of said cracks or cracks after 20 cycles and preferably 40 charge-discharge cycles of the cathode to a C / 2 regime.

19) A cathode according to claim 17 or 18, wherein the cathode is adapted to confer on the lithium-ion battery incorporating a first charge-discharge efficiency greater than 70%, said first charge-discharge cycle being set implemented between 4.3 V and 2.5 V at a C / 5 regime. 20) Cathode according to one of claims 17 to 19, wherein the cathode is adapted to confer the lithium-ion battery incorporating it for cycles implemented between 4.3 V and 2.5 V:

a capacity at a C / 5 rate greater than 140 mAh / g of cathode, and / or

a retention rate of capacity at C / 2 after 20 cycles and preferably further after 40 cycles relative to the first cycle, which is equal to or greater than 95%.

21) lithium-ion battery comprising at least one cell comprising an anode, a cathode and an electrolyte based on a lithium salt and a non-aqueous solvent, characterized in that the cathode is according to one of claims 17 to 20; .

22) Process for the preparation of a composition according to one of claims 1 to 16, characterized in that the process comprises successively:

b) a film deposit of said precursor mixture on a metal current collector, and

c) said thermal oxidation reaction of said film under an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 ⁴ Pa and at an oxidation temperature of between 150 ° C and 300 ° C, for the total or partial elimination of said sacrificial polymer phase and obtaining said at least one modified polymer. 23) The method of claim 22, wherein it implements steps a), b), c) in a single pass by a single said film obtained from said precursor mixture, said film having a thickness equal to or greater than 90 μιτι and preferably between 150 μιτι and 250 μιτι.

The method of claim 22 or 23, wherein said sacrificial polymeric phase comprises at least one poly (alkene carbonate) polyol having end groups of which more than 50 mol% comprise hydroxyl functions, and preferably wherein said at least one poly (alkene carbonate) polyol is a linear aliphatic diol chosen from poly (ethylene carbonate) diols and poly (propylene carbonate) diols having a weight-average molecular weight of between 500 g / mol and 5000 g / mol. The method of claim 24, wherein said sacrificial polymeric phase comprises:

The method according to claim 24 or 25, wherein said ingredients mixed in step a) further comprise a polysiloxane or polyisocyanate reactive compound which reacts upon said mixing with said at least one poly (alkene carbonate) polyol by functionalizing it with grafting onto said end groups of siloxane or isocyanate groups derived from said reactive compound, which is preferably selected from organodisiloxanes, such as aliphatic disiloxanes, and organodiisocyanates, such as aliphatic diisocyanates. 27) Method according to one of claims 22 to 26, wherein it implements step c) by a controlled temperature rise of a starting temperature preferably between 40 ° C and 60 ° C at said temperature of then oxidizing by an isotherm at said oxidation temperature, to thermally decompose said sacrificial polymer phase and modify said starting polymer so that said at least one modified polymer has said oxygenated groups.

The process according to one of claims 22 to 27, wherein said starting polymer used in step a) comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has nt) each a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked in step c) by said thermal oxidation reaction.

29) Method according to one of claims 22 to 27, wherein said starting polymer used in step a) comprises an apolar aliphatic polyolefin preferably selected from the group consisting of thermoplastic homopolymers and elastomers of an aliphatic mono-olefin, thermoplastic and elastomeric copolymers of at least two aliphatic mono-olefins and mixtures thereof, said apolar aliphatic polyolefin being modified in step c) to give said at least one modified polymer having an oxygen atomic mass content inclusive of between 2% and 10%, and in said precursor mixture obtained in step a).

The method of one of claims 24 to 26 and claim 29, wherein said starting polymer and said sacrificial polymeric phase form two separate phases.