WO2020169200A1

WO2020169200A1 - Nitrile solvent-based electrolyte for organic battery

Info

Publication number: WO2020169200A1
Application number: PCT/EP2019/054351
Authority: WO
Inventors: Thibaut Gutel; Lionel Picard; Daniel TOMASI
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2019-02-21
Filing date: 2019-02-21
Publication date: 2020-08-27
Also published as: EP3928367A1

Abstract

The present invention relates to an electrochemical cell for an organic battery, in particular for a lithium-ion battery, comprising: - at least one organic electrode comprising, as the active material at least one molecular compound, referred to as the active compound, which is selected from aromatic dianhydrides and the imide derivatives thereof, in particular the dianhydride of perylene 3,4,9,10 tetracarboxylic acid (PTCDA) or one of the reduced forms thereof; and - an electrolyte comprising at least one nitrile solvent selected from the mononitriles having the formula R1-CN where R1 represents a C1 to C3 alkyl group; and the dinitriles having the formula NC-R2-CN where R2 represents an alkylene group having an even number of carbon atoms.

Description

Title: Nitrile solvent-based electrolyte for organic battery

Technical area

The present invention relates to the field of electrochemical energy storage, in particular to batteries with organic electrode materials comprising, as active material, a molecular compound chosen from aromatic dianhydrides and imide derivatives thereof. , in particular the 3,4,9,10-tetracarboxylic acid dianhydride of perylene (symbolized by the abbreviation PTCDA). It relates more particularly to the formulation of a specific electrolyte based on mono- and / or dinitrile solvent (s) for these batteries with organic electrodes, in particular for lithium-ion batteries.

Prior art

Lithium batteries are increasingly used as stand-alone energy sources, particularly in portable equipment, where they are gradually replacing nickel-cadmium (NiCd) and nickel-metal hydride (NiMH) batteries. This development can be explained by the continuous improvement in the performance of lithium accumulators, thus giving them energy densities markedly higher than those offered by the NiCd and NiMH sectors. Lithium batteries find multiple applications, particularly in new information and communication technologies (NICT), medical devices, electric vehicles, the energy storage of photovoltaic cells, etc.

These lithium electrochemical generators conventionally operate on the principle of insertion or deinsertion (or intercalation-deintercalation) of lithium on at least one electrode. In particular, in a lithium-ion accumulator, the Li ⁺ cations thus go back and forth between the electrodes, positive or negative respectively, on each charge and discharge of the accumulator. The active material of the positive electrode is capable of releasing lithium ions at the time of charge and incorporating lithium ions at the time of discharge.

In general, the active compounds of electrodes used in commercial batteries are, for the positive electrode, lamellar oxides such as LiCoCk, LiNiCk and mixed Li (Ni, Co, Mn, Al) Ck, oxides of spinel structure of compositions close to LiMn ₂ 0 ₄ or alternatively of the lithium phosphate type, such as LiM ¹ P0 ₄ with M ¹ being chosen from Fe, Mn, Co and mixtures thereof.

The negative electrode is generally carbon (graphite, coke, etc.) or optionally LLTisO ^ spinel oxide or a metal forming an alloy with lithium (Sn, Si, etc.).

To respond more particularly to the new markets of portable electronics, hybrid and electric cars or solar photovoltaics, the constraints of cost, production volume and power performance require the search for new active electrode materials.

With this in mind, organic compounds (molecules and polymers) have already been developed, as active electrode material of lithium batteries (respectively sodium, magnesium, etc.), for their ability to capture lithium from reversible manner by releasing or capturing one or more electrons. Among these organic molecules, aromatic dianhydrides, such as 3,4,9,10-tetracarboxylic acid perylene (PTCDA, C24H8O6), have been proposed as electroactive electrode materials.

However, batteries incorporating electrodes based on an active material of the PTCDA type exhibit a rapid loss of capacity during repeated charge / discharge cycles, linked in particular to a phenomenon of dissolution of the starting material and of the electrochemically generated enolate derivatives, in the battery electrolyte, generally based on a mixture of carbonate solvents, for example based on ethylene carbonate (EC), diethyl carbonate (DEC) and / or dimethyl carbonate (DMC).

In order to limit this problem of dissolving the electroactive material of aromatic dianhydride type, for example PTCDA, and its intermediates, several strategies have already been considered.

It has for example been proposed, in order to improve the cycling stability of these bateries, to use PTCDA, not in the molecular state, but in an insoluble form, for example in the form of polyimides derived from PTCDA, and more particularly of poly (N - "- hcxyl-3,4,9,10-perylènc tetracarboxylic) imide (PTCI) [1], or in the form of a polymeric structure based on sulfur atoms, in in which the PTCDA units are interconnected with thioether bonds [2]

It has also been proposed to use PTCDA in carbonaceous composites. More particularly, Cui et al. [3] and Jing et al. [4] describe the synthesis of nanomaterials based on PTCDA and carbonaceous material, more particularly PTCDA / reduced graphene oxide (rGO) composites and PTCDA / carbon black (CB) composites, making it possible to limit the dissolution of PTCDA in the electrolyte via the establishment p- p interactions. However, this strategy makes it possible, on the one hand, to achieve limited electrochemical performance and, on the other hand, requires the preparation of new composite materials incorporating a high proportion of inactive mass (carbonaceous material).

It has also been shown that a change in the counterion implemented in organic batteries reduces the problems of dissolution of PTCDA. More particularly, the association with larger counter -ions, as is the case for sodium [5], potassium [6], magnesium and calcium [7] batteries, makes it possible to reduce, in a to a certain extent, the solubility of the intermediates formed with PTCDA in liquid electrolytes based on carbonate type solvents, for example in an ethylene carbonate (EC) / diethyl carbonate (DEC) mixture.

Other work [8] has also focused on stabilizing the performance of PTCDA-based electrodes for potassium batteries, by using a solid polymeric electrolyte based on polycarbonates.

Disclosure of the invention

The present invention aims to provide a novel electrochemical cell for an organic battery, in particular for a lithium-ion battery, having an electrode comprising, as active material, a molecular compound chosen from aromatic dianhydrides and imide derivatives thereof, such as PTCDA, and making it possible to achieve improved electrochemical performance, in particular in terms of stability of the specific capacity during cycling.

Thus, the inventors have observed that the implementation of electrolytes based on mono-nitrile solvents and / or specific dinitriles, preferably based on acetonitrile, makes it possible to avoid the dissolution, in the electrolyte, of the material of electrode based on PTCDA during cycling, and lead to very stable specific capacities during charge-discharge cycles.

Thus, the invention relates, according to a first of its aspects, to an electrochemical cell for an organic battery, in particular for a lithium-ion battery, comprising: - at least one organic electrode comprising, as active material, a molecular compound chosen from aromatic dianhydrides and imide derivatives thereof, in particular 3,4,9,10 -tetracarboxylic acid dianhydride of perylene (PTCDA), or one of their reduced forms; and

an electrolyte comprising at least one nitrile solvent chosen from mononitriles of formula Ri-CN with Ri representing a C1 to C3 alkyl group; and dinitriles of formula NC-R2-CN with R2 representing an alkylene group having an even number of carbon atoms.

An electrochemical cell according to the invention thus advantageously uses an aromatic dianhydride or an imide derivative thereof, for example PTCDA, in the molecular state, without having recourse to a chemical or physical modification of the active material or of the electrode.

Also, as illustrated in the examples which follow, an electrochemical cell according to the invention, combining an electrode based on a compound of aromatic dianhydride type, in particular based on PTCDA, and an electrolyte based on mono and solvent (s). / or dinitrile (s) according to the invention exhibit excellent electrochemical performance, in particular in terms of cycling stability and resistance at high charge / discharge rates.

Advantageously, it has a high reversible capacity that is stable over several hundred cycles, unlike in particular electrochemical cells based on carbonate solvents.

Thus, an electrochemical cell according to the invention advantageously exhibits excellent cycling stability, whether in slow cycling regime (for example, C / 10) than in fast regime (for example, in C regime).

The invention also relates to the use of one or more nitrile compounds chosen from mononitriles of formula Ri-CN with Ri representing a C1 to C ₃ alkyl group, and dinitriles of formula NC-R ₂ -CN with R ₂ representing a alkylene group having an even number of carbon atoms, as solvent (s) in an electrolyte of an electrochemical cell for an organic battery, in which at least one of the electrodes comprises, as active material, a molecular compound chosen from aromatic dianhydrides , imide derivatives thereof, in particular PTCDA, and their reduced forms. In the remainder of the text, and unless otherwise indicated, the name “active compound of aromatic dianhydride type” will denote the compound (s) used as active material of at least one of the electrodes of. an electrochemical cell according to the invention, chosen (s) from aromatic dianhydrides, imide derivatives thereof and their reduced forms.

These active compounds are described more precisely in the remainder of the text.

The active compound of aromatic dianhydride type used according to the invention can be more particularly chosen from PTCDA, NTCDA, 1,2,4,5-tetracarboxylic acid dianhydride, imide derivatives of PTCDA, NTCDA and 1,2,4,5-tetracarboxylic acid dianhydride, and their reduced one or more electron forms.

Preferably, the active compound is chosen from PTCDA, NTCDA, 1,2,4,5-tetracarboxylic acid dianhydride, and their forms reduced to one or more electrons. More preferably, the active compound is PTCDA or one of its forms reduced to one or more electrons.

The nitrile solvents used in the electrolyte of an electrochemical cell according to the invention are more preferably chosen from acetonitrile, propionitrile, butyronitrile, succinonitrile, sebaconitrile and their mixtures. Preferably, the nitrile solvent is acetonitrile.

The invention also relates, according to another of its aspects, to an organic battery comprising at least one electrochemical cell as defined above.

Such an organic battery is more particularly a lithium-ion battery.

Other characteristics, variants and advantages of electrochemical cells for batteries according to the invention will become more apparent on reading the description, examples and figures which follow, given by way of illustration and not by way of limitation of the invention.

Brief description of the drawings

[Fig 1] shows the evolution of the specific capacity C (in mAh / g) as a function of the number of cycles N, in charge (¨) and in discharge (■), for the battery tested in example 1, implementing an electrolyte based on carbonate solvents. [Fig 2] shows the potential evolution curves (in V vs Li ⁺ / Li °) as a function of the specific capacity C (in mAh.g ¹ )) during the second charge-discharge cycle at a C / regime 10 batteries prepared according to Example 2, using electrolytes of different types;

[Fig 3] shows the evolution of the specific capacity C (in mAh / g) as a function of the number of cycles N, at increasing speeds (5 cycles at C / 10, C / 5, C / 2, C, 2C and 4C respectively) then at a rate of C, for batteries using electrolytes of different types as described in example 2;

[Fig 4] shows the evolution of the specific capacity C (in mAh / g) as a function of the number of cycles N, for two identical batteries, using an electrolyte based on acetonitrile and a lithium salt LiTFSI, for increasing regimes (5 cycles at C / 10, C / 5, C / 2, C, 2C and 4C respectively) then at a rate of C, as described in example 3.

[Fig 5] shows the evolution curves of the specific capacity C (mAh / g) as a function of the number of cycles N, for batteries using electrolytes based on nitrile solvents of different nature, as described in example 4 .

[Fig 6] shows the evolution curves of the specific capacity C (mAh / g) as a function of the number of cycles, for three identical batteries, using gelled electrodes comprising an electrolyte based on a succinonitrile solvent, prepared according to l Example 5, for different cycling regimes (C / 10 to 4C).

In the remainder of the text, the expressions "between ... and ..." and "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the terminals are included, unless otherwise stated.

Unless otherwise indicated, the expression "comprising / comprising a (s)" should be understood as "comprising / comprising at least one".

detailed description

ORGANIC ELECTRODE

An electrochemical cell according to the invention more particularly comprises two electrodes of opposite polarity, respectively a positive electrode and a negative electrode, separated by an electrolyte, at least one of the electrodes comprising, as active material, a molecular compound chosen from dianhydrides aromatics and imide derivatives thereof, in particular perylene 3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), or a reduced form thereof.

For the purposes of the invention, the term “active electrode material (respectively compound)” means a material (respectively a compound) for inserting / deinserting a cation C ^{n +} in which n is 1 or 2 (Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ or Mg ²⁺ ) from an electrode of an electrochemical generator. More particularly, the active material (compound) of the positive electrode is capable of releasing C ^{n +} ions at the time of charging and of incorporating C ^{n +} ions at the time of discharge of the electrochemical generator. Conversely, the active material (compound) of the negative electrode is capable of incorporating C ^{n +} ions at the time of charge and of releasing C ^{n +} ions at the time of discharge of the electrochemical generator.

Aromatic dianhydride compounds and their imide derivatives, which can be used as active electrode materials, are described in the literature (eg, [2]).

In particular, these active compounds correspond to the following general formula (I): [Chem 1]

in which :

- Ar represents an aromatic, mono or polycyclic group, preferably formed from 1 to 5 rings, each ring preferably comprising 6 members; and

- X represents O (aromatic dianhydrides of cases), or NR, with R representing a hydrogen atom or an alkyl group -C _O (case of imide derivatives);

or one of its forms reduced to one or more electrons.

Preferably, Ar can represent a benzene ring or an aromatic group formed from two to five condensed aromatic rings, such as a naphthalene or perylene group. The compounds of aromatic dianhydride type used as active material of at least one of the electrodes according to the invention can be more particularly chosen from the following compounds:

Perylene 3,4,9,10-tetracarboxylic acid dianhydride, known by the abbreviation PCTDA, of the following formula:

[Chem 2]

or one of its imide derivatives of formula:

[Chem 3]

with R being as defined above; 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, known by the abbreviation NTCDA, of the following formula:

[Chem 4]

or one of its imide derivatives of formula:

[Chem 5]

with R being as defined above; 1,2,4,5-tetracarboxylic acid dianhydride, also known under the name “pyromellitic dianhydride”, of formula:

[Chem 6]

or one of its imide derivatives of formula:

[Chem 7]

and their forms reduced to one or more electrons.

The carbonyl groups of compounds of aromatic dianhydride type, used as active material according to the invention, are electron acceptor groups and therefore capable of being reduced, and can thus combine, for example with a Li ⁺ ion, to form lithium enolate groups. The charge / discharge cycle process of the electrochemical cell according to the invention is thus based on a reversible redox reaction of enolization of the carbonyl groups of the active compound (s) used, thus allowing the insertion / deinsertion of the Li cations. ⁺ (or Na ⁺ , K ⁺ , Mg ²⁺ or Ca ²⁺ ) at the level of the active material. This type of compound can thus enter into the constitution of a positive electrode, when the energy storage device uses a metallic counter-electrode, or into the constitution of a negative electrode, when the energy storage device is in Li-ion (or Na-ion, K-ion, Mg-ion or Ca-ion) configuration.

The reversible redox reaction on the basis of which the charge / discharge process of the electrochemical cell according to the invention is established, can be a one, two, three, or even up to 4 electron redox reaction.

According to a particular embodiment, the active compound can be PTCDA or one of its imide derivatives, or one of their forms reduced to one or more electrons.

Preferably, the active compound is PTCDA or one of its reduced forms.

The charge / discharge cycle process of an electrochemical cell according to the invention, comprising at least one PTCDA-based electrode, can be more particularly based on the redox reaction of reversible enolization to one or two electrons, preferably to two electrons, as shown below, in connection with the insertion / disinsertion of Li ⁺ cations.

[Chem 8]

PTCDA

In the context of an electrochemical cell for a lithium-ion battery, the PTCDA is preferably used in the PTCDA form as the active material of the negative electrode, the counter-electrode being a lithiated positive electrode.

PTCDA, used as an active electrode material, can alternatively be in the reduced form LLPTCDA, as shown above.

In the context of the implementation of the electrode for a Na-ion, K-ion, Ca-ion or Mg-ion battery, the active material can be respectively in the reduced form Na ₂ PTCDA, K ₂ PTCDA, CaPTCDA or MgPTCDA.

It is of course up to those skilled in the art to adjust the conditions of use of the electrochemical cell, and more particularly the potential domain, in order to target cycling on a reversible enolation reaction. For example, in the context of the implementation of an electrochemical cell for a lithium-ion battery, implementing an electrode based on PTCDA and a counter-electrode based on LiFeP0 ₄ , as described more precisely in the following section. text, the electrochemical conditions of use for its charge / discharge cycle process can be obtained between potential limits of 0.5 to 1.5 V vs Li ⁺ / Li.

The aromatic dianhydride compounds, used as an active electrode material according to the invention, may be commercially available or prepared by general methods known to those skilled in the art.

For example, PTCDA is commercially available, for example from the supplier Sigma-Aldrich or TCI.

The lithiated form of the compound of aromatic dianhydride type, for example the lithiated form of PTCDA, can be obtained beforehand, for example by reacting said compound with metallic lithium. Alternatively, it can be obtained electrochemically in situ from the use of said compound to prepare an electrode of an electrochemical generator, during the first reduction. The same applies, for example, to the potash and soda forms.

The compound (s) of aromatic dianhydride type, used as active material of at least one of the electrodes of an electrochemical cell according to the invention, advantageously represent from 10% to 99% by mass of the total mass of the electrode. , in particular more than 40% by mass, and more particularly from 80% to 99% by mass, relative to the total mass of the electrode.

Said compound (s) of aromatic dianhydride type, for example PTCDA or one of its reduced forms, can be used, in a conventional manner, together with one or more electronically conductive additive (s).

Said electronically conductive additive (s) can be chosen from carbon fibers, carbon black, carbon nanotubes, graphene and their analogs, and metallic nanowires, such as for example copper nanowires.

Preferably, the organic electrode according to the invention, for example based on PTCDA, comprises, as electronically conductive additive, metallic nanowires. For the purposes of the invention, the term “nanowire” is understood to mean a wire whose thickness is between 1 and 100 nanometers and therefore the length can range up to 10 micrometers.

From a geometric point of view, they can advantageously have a form factor, corresponding to the ratio of the length of the nanowire to its diameter, ranging from 10 to 1,000,000, for example greater than 30.

Advantageously, these nanowires make it possible to ensure good electronic conduction and have very low percolation thresholds within the electrodes.

These metal nanowires can be metal nanowires selected from copper, nickel, silver, gold, platinum, titanium, palladium, zinc, aluminum and alloys thereof.

Preferably, they are nanowires made of copper, nickel or silver, these being particularly suitable for an active material exhibiting an electrochemical potential ranging from 0 to 3 V vs Li ° / Li ^+, like PTCDA.

Preferably, the metallic nanowires are copper nanowires.

Advantageously, said electronic conductive additive (s) may be present in the composition of the organic electrode, in an amount of 0.1 to 40%, preferably 1 to 10% by mass, relative to the total mass of the 'electrode.

According to a particular embodiment, said active compound (s) of aromatic dianhydride type, for example PTCDA or one of its reduced forms, and said electronically conductive additive (s) can be used in level of the electrode in a weight ratio of active compound (s) / electronically conductive additive (s) of between 50 and 5, preferably between 20 and 10, in particular between 17 and 15.

Also, the compound (s) of aromatic dianhydride type, for example PTCDA or one of its reduced forms, can be used together with one or more binder (s), in particular one or more polymeric binders.

Such binders can be chosen from fluorinated binders, in particular from polytetrafluoroethylene, polyvinylidene fluoride (PvdF), polymers derived from carboxymethylcellulose, polysaccharides and latexes, in particular of the styrene-butadiene rubber type (BR or in English " stryrene-butadiene rubber '). A particularly preferred binder is poly (vinylidene fluoride) (PvdF).

Said binder (s) may be present in an amount less than or equal to 20% by mass, relative to the total mass of the electrode, in particular less than or equal to 10% by mass, in particular less than or equal to 5% by mass , relative to the total mass of the electrode.

According to a particular embodiment, the said active compound (s) of aromatic dianhydride type, for example PTCDA or one of its reduced forms, and the said binder (s) can be used at the level of the electrode, in a ratio mass of active compound (s) / binder (s) of between 50 and 1, preferably between 20 and 2.

The electrode based on said compound (s) of aromatic dianhydride type according to the invention can thus comprise, in addition to said compound (s) of aromatic dianhydride type, for example PTCDA or one of its reduced forms, one or more additive (s) ) electronic conductor (s) and / or one or more binder (s), in particular as described above.

By way of example, an organic electrode used in an electrochemical cell according to the invention can comprise the active compound of aromatic dianhydride type, in particular PTCDA, combined with copper nanowires and poly (vinylidene fluoride).

Conventionally, each of the electrodes is in contact with a current collector.

For example, copper, aluminum, nickel, carbon felt, or stainless steel can be used as a current collector for a positive electrode; and copper, or steel, processed into a cut sheet, foamed metal or rolled sheet plate, for example, can be used as a current collector for a negative electrode.

According to a particular embodiment, an electrode according to the invention comprises a copper-based current collector, for example in the form of a copper foil or strip.

Preparation of the organic electrode An organic electrode based on one or more active compounds of aromatic dianhydride type according to the invention, for example based on PTCDA, can be prepared via at least the following steps:

(a) preparation of a dispersion comprising, in one or more aqueous and / or organic solvents, at least one active compound of aromatic dianhydride type, in particular PTCDA, and optionally one or more electronically conductive additive (s) ( s) and / or binder (s);

The solvent used can be an organic solvent, for example chosen from the group comprising N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), dimethylformamide (DMF), tetrahydrofuran (THF) and acetone. Fe solvent can be more particularly N-methyl-2-pyrrolidone (NMP).

The dispersion, more commonly known as "ink", can be homogenized before it is spread, for example using a deflocculator or a sonotrode.

(b) depositing the dispersion thus prepared on the surface of a current collector, for example, of the copper strip type;

The deposition of said dispersion can be carried out by coating, by a printing technique, by extrusion or by co-rolling. Those skilled in the art are able to adjust the conditions for implementing these different techniques.

(c) evaporation of said solvent (s) to form the electrode film.

Evaporation can be carried out by drying, for example in an oven, at a temperature of between 20 and 150 ° C, in particular between 50 and 80 ° C, for a period of between 1 and 15 hours.

Case of a gel electrode

According to a particular embodiment, the organic electrode based on one or more active compounds of aromatic dianhydride type according to the invention is a gelled electrode comprising, in addition to said active electrode material according to the invention, one or more nitrile compounds and at least one polymer, and advantageously one or more salts, in particular a lithium salt.

Fe nitrile compound used is preferably a dinitrile compound, preferably succinonitrile. Such gelled electrodes have for example been described in document WO 2017/032940.

The polymer used can be chosen from the group comprising poly (styrene-co-acrylonitrile); poly (butylmethacrylate-co-isobutylmethacrylate); poly (butylmethacrylate); poly (isobutylmethacrylate); poly (butylmethacrylate-co-methymethacrylate); poly (methyl methacrylate) (PMMA); poly (vinylidene-hexafluoropropylene fluoride) (PVdF-HFP); polyethylene oxide (POE), polyvinylpyrrolidone (P VP) and poly (vinylidene fluoride) (PVdF).

Advantageously, the nitrile compound (s) and / or said salt (s), in particular the lithium salt, correspond to the constituents of the electrolyte used in the electrochemical cell according to the invention, as described more precisely below. of text.

Thus, according to an alternative embodiment, the organic electrode, based on one or more active compounds of aromatic dianhydride type according to the invention is a gelled electrode, the porosity of which is filled with the electrolyte used in the electrochemical cell. according to the invention.

The electrolyte can be directly added to the ink formulation coated on the surface of the current collector, when preparing the electrode as previously described.

Thus, the preparation of a gelled organic electrode can thus comprise the following steps:

- preparation of an ink comprising, in one or more solvents, said active electrode material, at least one nitrile compound, preferably dinitrile, at least one polymer and advantageously at least one salt, in particular a lithium salt; and

- ink deposit on a current collector; and

- evaporation of said solvent (s) to form the gelled electrode.

The use of a “gelled” electrode is particularly advantageous in the case where the nitrile solvent of the electrolyte, such as succinonitrile, exhibits poor wettability properties with respect to the surface of the electrode. The formulation of such a “gelled” electrode makes it possible to optimize the electrolyte / electrode interface of the electrochemical system, insofar as the electrolyte is already present in the porosity of the electrode.

Advantageously, the formulation of a gel electrode makes it possible to increase the specific capacity of the electrochemical cell.

Thus, according to a preferred embodiment variant, when the nitrile solvent for the electrolyte is succinonitrile, the organic electrode based on one or more active compounds of aromatic dianhydride type according to the invention is in the form of an electrode. gelled, comprising the electrolyte based on succinonitrle.

The formulation of a gel electrode also simplifies the manufacture of the electrochemical system, since it is no longer necessary to fill the cell with a liquid electrolyte once the battery is assembled.

In addition, since the electrolyte is trapped in the structure of the electrode, the risk of electrolyte leakage is avoided, and therefore, the safety of the electrochemical device is improved.

A gelled organic electrode implemented according to the invention can more particularly comprise from 20 to 50% by mass of a mixture of nitrile compound (s) and of lithium, sodium, potassium, calcium or magnesium salts, in particular lithium salts, preferably from 25 to 45% by weight and more particularly from 30 to 35% by weight, relative to the total weight of the electrode.

Thus, according to an alternative embodiment, the electrode based on said active compound (s) of aromatic dianhydride type according to the invention, in particular for a lithium-ion battery, may comprise, in addition to said compound (s) of aromatic dianhydride type, by example PTCDA or one of its reduced forms, one or more electronically conductive additive (s) and / or one or more binder (s), in particular as described above, one or more nitrile compounds , for example succinonitrile, and advantageously one or more salts, in particular a lithium salt.

By way of example, an organic electrode used in an electrochemical cell according to the invention for a lithium-ion battery can comprise PTCDA combined with copper nanowires, poly (vinylidene fluoride), a nitrile compound, in particular succinonitrile, and a lithium salt. COUNTER-ELECTRODE

An electrochemical cell according to the invention more particularly comprises two electrodes of opposite polarity, respectively a positive electrode and a negative electrode, separated by an electrolyte, at least one of the electrodes being an electrode based on one or more active compounds of type of aromatic dianhydride, as defined above.

Preferably, the organic electrode based on said active compound (s) of aromatic dianhydride type according to the invention, for example based on PTCDA, constitutes the negative electrode of the electrochemical cell according to the invention.

The nature of the counter-electrode, in particular the positive electrode, is of course chosen with regard to the nature of the desired battery, for example depending on whether it is a Li-ion battery, or even a Li-ion battery. 'a Na-ion, K-ion, Ca-ion or Mg-ion battery.

In the case where the electrode based on said active compound (s) of aromatic dianhydride type, for example based on PTCDA, constitutes the negative electrode of a lithium battery, the positive counter-electrode can typically be an electrode comprising, as active material, a lithium insertion material of the lithiated oxide type or of the lithiated phosphate type comprising at least one transition metallic element.

As examples of lithiated oxide compounds comprising at least one transition metallic element, mention may be made of single oxides or mixed oxides (that is to say oxides comprising several distinct transition metallic elements) comprising at least one metallic element of transition, such as oxides comprising nickel, cobalt, manganese and / or aluminum (these oxides can be mixed oxides).

More specifically, as mixed oxides comprising nickel, cobalt, manganese and / or aluminum, there may be mentioned the compounds of the following formula LiM ² 0 ₂ , in which M ² is an element chosen from Ni, Co, Mn , A1 and mixtures thereof.

As examples of such oxides, mention may be made of the lithiated oxides L1C0O2, LiNiCL and the mixed oxides Li (Ni, Co, Mn) C> 2 (such as Li (Nii / 3Mm / 3Coi / 3) 02) also known. under the name NMC), Li (Ni, Co, A1) C> ₂ (such as N i (N io.xCoo.15 A lo.os) Ch also known under the name NCA) or Li (Ni, Co, Mn , A1) 0 ₂ . As examples of lithiated phosphate compounds comprising at least one transition metallic element, mention may be made of compounds of formula LiM ¹ P0 ₄ , where M ¹ is chosen from Fe, Mn, Co and mixtures thereof, such as LiFePCL.

It can also be an electrode based on an oxide of spinel structure, such as LiM CL, LiMm, 5Nio, 504.

According to a particular embodiment, the counter-electrode of an electrochemical cell for a lithium battery according to the invention is based on LiFePCL.

As for the electrode based on said active compound (s) of aromatic dianhydride type, in addition to the presence of an active material, such as those defined above, the counter-electrode may comprise one or more binders, in particular one. polymeric binder such as polyvinylidene fluoride (PvdF), as well as one or more electrically conductive adjuvants, such as for example carbonaceous materials such as carbon black.

The counter-electrode can be associated with a metallic current collector, as described above, for example an aluminum strip.

The counter electrode is preferably separate from a lithium or metallic sodium electrode. In fact, nitrile solvents are generally unstable at very low potentials on lithium and metallic sodium.

As positive counter-electrodes in the context of an electrochemical cell for a sodium battery, there may be mentioned, for example, electrodes of the “NVPF” type of formula Na ₃ V ₂ (P0 ₄ ) ₂ F ₃ , or else so-called electrodes of. “NMC” type, in particular in the form of lamellar oxides corresponding to the general formula NaNi _x Ln _y Co _z 0 ₂ with x + y + z = 1.

ELECTROLYTE BASED ON SOLVANIYS) NITRILE (S)

An electrolyte of an electrochemical device typically comprises at least one salt in one or more solvents to ensure conduction of ions, such as a lithium salt when the device is a lithium battery.

As mentioned above, an electrochemical cell according to the invention uses an electrolyte based on one or more nitrile solvents chosen from:

- mononitriles of formula Ri-CN with Ri representing an alkyl group in

Ci to C3; and - Dinitriles of formula NC-R ₂ -CN with R ₂ representing an alkylene group having an even number of carbon atoms.

In the remainder of the text, the term "nitrile solvent" is used to denote a solvent chosen from mononitrile and dinitrile compounds, as defined above, and their mixtures.

It is understood that the electrolyte can comprise a single mono- or dinitrile solvent, or a mixture of at least two solvents chosen from mono- and di-nitrile solvents.

The term “solvent” means the fact that the mono- or dinitrile compound, or mixture of mono- and / or dinitrile compounds, is capable of dissolving said salt (s).

The term “mononitrile” solvent (respectively, “dinitrile”) is intended to denote an organic solvent comprising a single nitrile group (respectively, two nitrile groups) of formula —CN.

The mononitrile solvent is chosen from acetonitrile (CH ₃ CN), propionitrile (CH ₃ CH ₂ CN) and butyronitrile (CH ₃ C ₂ H ₄ CN).

The dinitrile solvent can be more particularly chosen from the compounds of formula NC-R ₂ -CN with R ₂ representing a C _2n H _{4n group} with n being an integer between 1 and 8, in particular between 1 and 5.

In particular, the dinitrile solvent can be chosen from succinonitrile (C4H4N2) and sebaconitrile (C10H16N2).

As examples of lithium salt, mention may be made of LiPFe, FiCICL, L1BF4, LiAsFe, L1CF3SO3, FiN (CF3S02) 3, LiNfCLFsSCL), lithium bistrifluoromethylsulfonylimide FiN [S0 ₂ CF ₃ ] ₂ (known as abbreviation FiTFSI), lithium bis (fluorosulfonyl) amide (known by the abbreviation FiFSI) FiN [S0 ₂ F] ₂ and mixtures thereof.

Preferably, the electrolyte comprises, as the lithium salt, LiPFe or FiTFSI, preferably FiTFSI.

Fe or said salts, for example lithium salt, may be present in the electrolyte, in a content ranging from 0.3 M to 3 M.

The electrolyte can be in liquid or gel form. The liquid electrolyte according to the invention can be made to impregnate a separator element arranged between the negative electrode and the positive electrode of the electrochemical cell.

This separator can be made of a porous material, such as a polymeric material, capable of accommodating the liquid electrolyte in its porosity.

Preferably, the electrolyte used according to the invention is devoid of carbonate solvent. Preferably, the electrolyte does not include any solvent other than said mono- and / or dinitrile compound (s) as defined above.

The nitrile solvent (s) according to the invention preferably represent more than 40% of the total volume of the electrolyte, in particular more than 80% of the total volume of the electrolyte.

According to a particularly preferred embodiment, the electrolyte of an electrochemical cell for an organic battery according to the invention can be formed from one or more nitrile solvents as defined above, and from one or more salts, for example of a lithium salt for a lithium battery.

By way of example, an electrolyte of an electrochemical cell for a lithium battery according to the invention comprises, or even is formed, of one or more nitrile solvents, preferably acetonitrile and at least one lithium salt, in particular LiTFSI or LiPFe.

By way of example, an electrochemical cell for a lithium battery according to the invention comprises:

- an organic electrode based on PTCDA constituting the negative electrode;

a positive counter-electrode, preferably comprising, as active material, LiFePCL; and

- Said electrolyte disposed between said positive electrode and said negative electrode, said electrolyte comprising at least one nitrile solvent as defined in claim 1 or 9, preferably acetonitrile, and a lithium salt, preferably LiPFe or LiTFSI.

Preferably, said negative electrode comprises, besides the PTCDA, copper nanowires as an electronically conductive additive, and a polymer binder, in particular polyvinylidene fluoride. Preferably, the positive electrode comprises, in addition to LiFePCL, an electronically conductive additive, for example carbon black (Super P), and a polymeric binder, in particular polyvinylidene fluoride.

Preferably, said electrolyte is formed from said lithium salt in one or more nitrile solvents according to the invention.

According to a particular variant embodiment, in particular when the nitrile solvent for the electrolyte used is succinonitrile, the electrolyte can be introduced directly during the formulation of the ink used for the preparation of the PTCDA-based electrode. , and remains contained in the electrode after its realization.

ORGANIC BATTERY

An electrochemical cell according to the invention, comprising an organic electrode based on one or more active compounds of aromatic dianhydride type, in particular based on PTCDA, and an electrolyte based on nitrile solvent (s) such as (s) ) as defined above, is intended to enter into the constitution of batteries, and in particular for lithium (Li-ion), sodium (Na-ion), potassium (K-ion) and calcium batteries (Ca-ion) or magnesium (Mg-ion).

Thus, the invention also relates, according to another of its aspects, to an organic battery comprising at least one electrochemical cell as described above.

Preferably, it is a lithium-ion battery.

The remainder of the battery can be formed using conventional methods.

In general, lithium-ion batteries have an architecture with two electrodes (a positive electrode and a negative electrode), both coated on an electrically conductive current collector, arranged on either side of an organic separator or inorganic. The two mounting techniques of this architecture currently the most used are the winding (winding of the various constituents in a cylindrical or prismatic geometry) and the stack (stacking layer by layer of the various elements). Of course, other assembly techniques to form a battery are possible, such as printing techniques.

The invention will now be described by means of the following figures and examples, given of course by way of illustration and without limitation of the invention. Example

EXAMPLE 1 (comparative)

A commercially available PTCDA powder is dispersed with copper nanowires (CuNW) (prepared according to the protocol described in document WO2017 / 137591) in an 8% solution of polyvinylidene fluoride (PvdF) in N- methylpyrrolidinone in a proportion of 85% PTCDA / 5% CuNW / 10% PvdF (by weight), then the formulation is coated on a copper strip.

After drying at 55 ° C. overnight, electrodes are cut and dried under vacuum for 48 hours.

Electrodes of composition 90% LiFeP0 _4.5 % Super P, 5% PvdF, are prepared according to the same process.

These electrodes are assembled in a glove box in a battery using two polyolefin separators, with an electrolyte based on carbonates (mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC)) and LiPFe salts.

Electrochemical tests are carried out by galvanostatic cycling at a rate of C / 10 with potential terminals set at [0.5; 1.5 V]

The change in the specific capacity as a function of the number of charging and discharging cycles is shown in Figure 1.

EXAMPLE 2

As in Example 1, a PTCDA powder is dispersed with copper nanowires (CuNW) in an 8% solution of polyvinylidene fluoride (PvdF) in N-methylpyrrolidinone in a proportion of 85% PTCDA / 5% CuNW / 10 % PvdF (by weight), then the formulation is coated on a copper strip.

Electrodes of composition 90% LiFePCE, 5% Super P, 5% PvdF, are prepared according to the same process.

These electrodes are assembled in a glove box within a battery using two polyolefin separators with different electrolytes formed from an ether type solvent (dimethyl ether (DME), tetrahydrofuran (THF)), carbonate (dimethyl carbonate) (DMC)), lactone (gamma-butyrolactone (GBL)), mono-nitrile (acetonitrile (CH ₃ CN)) or ionic liquid (PyrFSI ^), and a lithium or sodium salt (LiFSI, LiTFSI, NaPFe ).

⁽ *> PyrFSI: 1-propyl-1-methyl pyrrolidinium bis (fluorosulfonyl) imide.

Electrochemical tests are carried out in galvanostatic cycling at increasing regimes (C / 10 to 4C), with potential limits set at [0.5; 1.5 V]

Figure 2 shows the curves of the potential as a function of the specific capacity, during the second charge-discharge cycle at a C / 10 regime.

Figure 3 shows the evolution of the specific capacity C (in mAh / g) as a function of the number of cycles N, at increasing speeds (5 cycles at C / 10, C / 5, C / 2, C, 2C and 4C respectively) then at a regime of C.

Conclusion

A high capacity in the second charge-discharge cycle is obtained for the battery using the acetonitrile-based electrolyte. Also, the capacity of the battery using the nitrile solvent remains stable with cycling.

In contrast, the specific capacity of batteries prepared from electrolytes based on solvents other than a nitrile solvent, particularly from a carbonate based electrolyte, drops significantly with the number of cycles.

EXAMPLE 3

Electrodes of composition 90% LiFePCL, 5% Super P, 5% PvdF, are prepared according to the same process.

These electrodes are assembled in a glove box in a battery using two polyolefin separators, with an electrolyte based on acetonitrile and LiTFSI salts.

The experiment is carried out on two identical batteries. Electrochemical tests are carried out in galvanostatic cycling at increasing regimes (C / 10 to 4C) with potential limits set at [0.5; 1.5V].

The results are shown in Figure 4, at increasing rates (5 cycles at C / 10, C / 5, C / 2, C, 2C and 4C respectively) then at a rate of C.

Conclusion

The capacity of the battery using an acetonitrile-based electrolyte remains stable during cycling. This experiment is reproducible on both batteries.

EXAMPLE 4

Electrodes of compositions 90% LiFePCL, 5% Super P, 5% PvdF, are prepared according to the same process.

These electrodes are assembled in a glove box in a battery using two polyolefin separators, with different electrolytes based on different nitrile solvents (acetonitrile (CFLCN), succinonitrile (SN) and sebaconitrile (SB)) and LiTFSI salts.

Electrochemical tests are carried out by galvanostatic cycling at increasing rates (5 cycles at C / 10, C / 5, C / 2, C, 2C and 4C respectively) then at a rate of C, with potential limits set at [ 0.5; 1.5V].

Figure 5 shows the evolution curves of the specific capacity C (in mAh / g) as a function of the number of cycles N at different speeds.

Conclusion

It is observed that the specific capacity remains stable with the number of cycles for the battery using an electrolyte based on acetonitrile, succinonitrile or sebaconitrile. The specific capacity is high for the battery using an acetonitrile-based electrolyte. It is lower in the case of the use of succinonitrile or sebaconitrile, due in particular to the strong polarization induced by these viscous electrolytes. It is possible to overcome this drawback and improve the specific capacity of these batteries, via the formulation of a gelled electrode as presented in Example 5 below.

EXAMPLE 5

Realization of a gel electrode

A PTCDA powder is dispersed with copper nanowires (CuNW) in an 8% solution of polyvinylidene fluoride (PvdF) in N-methylpyrrolidinone in a proportion of 85% PTCDA / 5% CuNW / 10% PvdF (by weight), to which is added 35% by mass of succinonitrile (SN) containing IM LiTFSI, then coated on a copper strip.

Electrodes of 90% LiFeP0 ₄ , 5% Super P, 5% PvdF compositions are prepared according to the same process.

These electrodes are assembled in a glove box in a battery using two polyolefin separators, with an electrolyte based on succinonitrile (SN) and LiTFSI salts.

The experiment is carried out on three identical batteries.

Electrochemical tests are carried out in galvanostatic cycling at increasing regimes (C / 10 to 4C) with potential limits set at [0.5; 1.5V].

Figure 6 shows the evolution curves of the specific capacity C (mAh / g) as a function of the number of cycles, for different cycling regimes (C / 10 to 4C).

Conclusion

The capacity remains stable whatever the speed (C / 10, C / 5, C / 2, C, 2C and 4C respectively) then during prolonged cycling at a speed of C. The use of a d configuration on the other hand, the gel electrode reduces the polarization of the system and to obtain a higher capacity, in comparison with the capacity obtained in Example 4.

List of documents cited

[1] Iordache et al., A tACS Appl. Mater. Interfaces, 2016, 8, 22762-22767;

[2] Han et al., Adv. Mater., 2007, 19, 1616-1621;

[3] Cui et al., J. Mater. Chem., 2016, 4, 9177

[4] Jing et al., Electrochimica Acta, 2018,

[5] Luo et al., Adv. Energy Mater, 2014, 4, 1400554;

[6] Chen et al., Nano Energy (2015) 18, 205-211;

[7] Rodriguez -Perez et al., J. Am. Chem. Soc. 2017, 139, 13031-13037

[8] Fei, J. Power Sources, 399 (2018) 294-298.

Claims

1. Electrochemical cell for organic battery, in particular for lithium-ion battery, comprising:

- at least one organic electrode comprising, as active material, at least one molecular compound, called an active compound, chosen from aromatic dianhydrides and imide derivatives thereof, in particular the dianhydride of acid 3, 4, 9,10-perylene tetracarboxylic acid (PTCDA), or a reduced form thereof; and

2. An electrochemical cell according to the preceding claim, wherein said active compound of the organic electrode is of formula (I)

[Chem 1]

in which :

- X represents O or N-R, with R representing a hydrogen atom or a C1-C6 alkyl group;

or one of its forms reduced to one or more electrons.

3. Electrochemical cell according to any one of the preceding claims, in which said active compound of the organic electrode is chosen from perylene 3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), dianhydride of perylene. 1,4,5,8-naphthalenetetracarboxylic acid (NTCDA), 1,2,4,5-tetracarboxylic acid dianhydride, imide derivatives of PTCDA, NTCDA and acid 1 dianhydride , 2,4,5-tetracarboxylic, and their forms reduced to one or more electrons.

4. An electrochemical cell according to any preceding claim, wherein said active compound of the organic electrode is PTCDA or one of its reduced to one or more electron forms.

5. An electrochemical cell according to any one of the preceding claims, in which the said active compound (s) represents (s) from 10% to 99% by mass of the total mass of said electrode, in particular more than 40% by mass and more particularly of 80% to 99% by mass, of the total mass of said electrode.

6. An electrochemical cell according to any one of the preceding claims, wherein said organic electrode further comprises one or more electronically conductive additives, preferably metallic nanowires, in particular copper nanowires.

7. An electrochemical cell according to any preceding claim, wherein said organic electrode further comprises one or more polymeric binders, preferably poly (vinylidene fluoride).

8. An electrochemical cell according to any one of the preceding claims, in which said organic electrode is a gelled electrode comprising, in addition, one or more nitrile compounds, in particular a dinitrile compound, and at least one polymer, and advantageously one or more. salts, in particular a lithium salt.

9. An electrochemical cell according to any one of the preceding claims, wherein said nitrile solvent is selected from acetonitrile, propionitrile, butyronitrile, succinonitrile, sebaconitrile and mixtures thereof, preferably said nitrile solvent is acetonitrile.

10. An electrochemical cell according to any one of the preceding claims, for a lithium-ion battery, in which the electrolyte comprises, or even is formed, one or more nitrile solvents, preferably acetonitrile, and at least one. lithium salt, in particular LiPFe or LiTFSI.

11. An electrochemical cell according to any one of the preceding claims, for a lithium-ion battery, comprising:

- an organic electrode based on PTCDA constituting the negative electrode;

a positive counter-electrode, preferably comprising, as active material, LiFeP04; and

- said electrolyte disposed between said positive electrode and said negative electrode, said electrolyte comprising at least one nitrile solvent as defined in claim 1 or 9, preferably racetonitrile, and a lithium salt, preferably LiPFr, or LiTFSI.

12. Electrochemical cell according to the preceding claim, wherein said negative electrode comprises, in addition to PTCDA, copper nanowires as an electronically conductive additive, and a polymer binder, in particular polyvinylidene fluoride.

13. An electrochemical cell according to claim 11 or 12, wherein said positive electrode comprises, in addition to said active material, an electronically conductive additive, in particular carbon black, and a polymeric binder, in particular polyvinylidene fluoride.

14. Use of one or more nitrile compounds chosen from mononitriles of formula R 1 - CN with R 1 representing a C ₁ to C ₃ alkyl group; and dinitriles of formula NC-R ₂ -CN with R ₂ representing an alkylene group having an even number of carbon atoms, as solvent (s) in an electrolyte of an electrochemical cell for an organic battery, in which at least one electrodes comprises, as active material, a molecular compound chosen from aromatic dianhydrides, imide derivatives thereof, in particular PTCDA, and their reduced forms.

15. Use according to claim 14, characterized in that said electrode is as defined in any one of claims 2 to 8.

16. Use according to claim 14 or 15, characterized in that the said nitrile compound or compounds are chosen from acetonitrile, propionitrile, butyronitrile, succinonitrile, sebaconitrile and their mixtures, preferably the nitrile compound is acetonitrile. .

17. Organic battery, in particular lithium-ion battery, comprising at least one electrochemical cell as defined in any one of claims 1 to 13.