Solid polymeric electrolytes based on triblock copolymers, in particular polystyrene-poly(oxyethylene)-polystyrene copolymers

SOLID POLYMER ELECTROLYTES BASED ON TRIBLOCK COPOLYMERS IN PARTICULAR POLYSTYRENE-POLY (OXYETHYLENE) -

POLYSTYRENE

DESCRIPTION

TECHNICAL AREA

The invention relates to solid polymer electrolytes based on triblock copolymers which are in particular polystyrene-poly (oxyethylene) -polystyrene or PS-b-POE-b-PS copolymers.

The technical field of the invention can be defined, in general as that of solid polymer electrolytes or EPS which are used in particular in lithium Li accumulators.⁺.

An elementary cell of a rechargeable battery or lithium accumulator comprises (see FIG. 1) an anode (on discharge) (1), generally made of metallic lithium or carbon-based, and a cathode (idem: on discharge) ( 2), generally in a metal oxide type lithium insertion compound such as LiMn₂O₄, LiCoO₂ or LiNiO₂, between which is inserted an electrolyte conductor (3) of lithium ions.

In the event of use, therefore during the discharge of the battery (see figure 1), the lithium released by oxidation at the pole (-) by the anode (1) in ionic form Li⁺, migrates through the conductive electrolyte (3) and is inserted by a reduction reaction in the crystal lattice of the active material of the cathode (2) pole (+). The passage of each Li ion⁺ in the internal circuit of the accumulator is exactly compensated by the passage of an electron in the external circuit (4), generating an electric current which can be used to power various devices (5) in the field of portable electronics such as computers or telephones, or in the field of applications of greater power and energy density, such as electric vehicles.

When charging (Figure 2), the electrochemical reactions are reversed, the lithium ions are released by oxidation at the pole (+), "cathode" (2) (the cathode on discharge becomes the anode on recharge), they migrate through the conductive electrolyte (3) in the opposite direction to that in which they circulated during the discharge, and come to settle or be inserted by reduction at the pole (-), “Anode” (1) (similarly the anode at discharge becomes the cathode at recharging) where they can form dendrites of metallic lithium (6), possible causes of short circuits.

In accumulators, the electrolyte or ionic conductor (3) which separates the electrodes is a fundamental element.

This electrolyte can be liquid, solid, or can also be in the form of a porous polymer film, for example made of poly (vinylidene difluoride) (PVDF) or poly (vinylidene difluoride-hexafluoropropylene) (PVDF-HDP) of a liquid electrolyte. Liquid electrolytes are generally based on carbonates such as propylene carbonate, ethylene carbonate and dimethylcarbonate. These liquid electrolytes have good conductivity, of the order of 1 mS / cm at room temperature, and allow operation between -20 and 60⁰C. However, they do not offer optimum performance and safety conditions, in particular due to the formation of dendrites during charging, thermal runaway problems, possible leaks, etc. At the end of the 1970s, Armand et al. [1] demonstrated that "dry" polymers could eventually replace the liquid electrolytes in Li batteries⁺. Electrolytes based on dry polymers, such as poly (oxyethylene) (POE), although safer due to the absence of liquid, have conductivity values ​​much too low for use at room temperature.

Thus, the conductivity σ obtained in document [1] with a system composed of POE and LiClO₄ is only 10^"7 S / cm.

Since then, research and development of solid polymer electrolytes (EPS) not only light, flexible, easy to use but also having an ionic conductivity at room temperature comparable to liquid electrolytes has been actively pursued. Among the solid polymer electrolytes, there may be mentioned, in addition to those based on POE, those based on:<img file="WO2007113236A1_D0001.tif" />

CH,

from HN- CHoCHo <img file="WO2007113236A1_D0002.tif" />

<img file="WO2007113236A1_D0003.tif" />

CH₂CH₂CH₃

<img file="WO2007113236A1_D0004.tif" /> with p = 2 to 6.

We are particularly interested here in solid electrolytes based on POE.

In order to increase the conductivity of the POE matrix of the solid polymer electrolyte, various means have been envisaged in the literature, among which there may be mentioned, for example:

- The incorporation of a fraction of mineral nanofillers such as (SiO2, TiO2, or AI2O3) in the POE.

This incorporation of mineral nanofillers has the drawback of being tricky to obtain a homogeneous dispersion of the nanofillers, in addition, the presence of aggregates reduces the conductive and mechanical properties. - The crosslinking of POE chains also plays an essentially mechanical role. The conductivity decreases with the crosslinking rate by reducing the segmental mobilities and also degrades the performance of the interface between the pole (-) and the electrolyte (increase in interfacial resistance in the case of lithium, passivation, degradation of the quality contact).

The drawbacks associated with crosslinking are therefore essentially a problem of battery stability and lower conductivity.

- The copolymerization of POE macromers. We find the performance of POE in terms of conductivity because the sizes of the macromolecular chains are of the same order, otherwise the mechanical strength is insufficient. And finally,

- The development of block or block copolymers based on POE.

It is on this latter strategy that research work has developed in recent years thanks to the strong development of controlled radical polymerization methods such as ATRP

(“Atom Transfer Radical Polymerization” in English), NMP (“Nitroxide Mediated Polymerization” in English) in the mid-1990s making it possible to easily prepare these block copolymers.

The POE block copolymers used in solid polymer electrolytes (EPS) can be AB block copolymers or ABA triblock copolymers. As regards the diblock copolymers, Sodaway et al. [2] were the first to study block copolymers as the basis for a solid polymer electrolyte (EPS). As far as diblock copolymers are concerned, their work has essentially focused on diblock copolymers, the first block of which is a poly (alkyl methacrylate) such as poly (lauryl methacrylate) (PLMA), poly (n methacrylate). -butyl) (PnMBA), or poly (methyl methacrylate), and the second block is poly (polyethylene glycol methacrylate, 9 EO units) (PMAPEG). These copolymers were synthesized anionically or by the ATRP method.

The materials obtained are dimensionally stable, do not flow and behave like an elastomer. The PLMA-b- PMAPEG copolymer doped with LiCF₃SC&gt; 3 has a conductivity of the order of 8.10^~6 S / cm at room temperature and is electrochemically stable over a large window of potential.

Their work has also demonstrated that the conductivity of PMAPEG in these block copolymer electrolytes changes inversely at the glass transition temperature T_g of the second block. Thus, σpLMA- PMAPEG (TgPLMA^{= ~} 3 5 C)&gt; Op_notBMA-PMAPEG (TgPnBMA = 4 0 C)&gt;

OpMMA- PMAPEG (TgPMMA ⁼ 1 0 0 C).

A cycling test was also carried out on a Li / Li battery cell⁺/ VO_x, the electrolyte used is the PnBMA-PMAPEG copolymer doped with LiCF₃SO₃. The test has shown that the capacity of these batteries remains stable at 80% after 300 cycles. The disadvantages of EPS prepared with the copolymers of this document are low conductivity at room temperature.

It is certainly possible to increase the conductivity by lowering the glass transition temperature (T_g) materials (which then have an elastomeric character) but then the problem of the feasibility of the films arises.

With regard to triblock copolymers, Jannasch et al. [3] studied the triblock copolymers prepared by the ATRP method, the central block of which is a POE or a POE-co-PPO and the external block of which is poly (pentafluorostyrene) (PFS).

The short PFS blocks (T_g = 33 ° C) and the POE or POE-co-PPO block doped with LiN (CF₃SO₂) ₂ (T_g -65 ° C) are immiscible, which leads to a phase microseparation giving electrolytes interesting electrical and mechanical properties.

With this system, they obtained an ionic conductivity of 3.10^~5 S / cm. The conductivity of the PFS-POE-co-PPO-PFS copolymer is slightly higher than that of PFS-POE-PFS, this is simply due to the proportion of polyether which is higher in PFS-POE-co-PPO-PFS (85 wt%) than in PFS-POE-PFS (71 wt%).

The major drawback of this system is a conductivity which is not yet sufficiently improved at room temperature compared to the systems already described previously in the literature. The advantage of such a structure as EPS is not demonstrated compared with POE of the same molar mass. Recently, Niitani et al. {4] described a new triblock copolymer electrolyte composed of PMAPEG (23 EO units) as the central block and PS as the external blocks. This copolymer, the number average molecular mass (M_not) is 250,700 g / mol, is prepared by the ATRP method, the PS blocks represent 8% by mass of the copolymer. TEM images have shown that phase microseparation depends on the proportion of POE and PS in the copolymer. The size of the PS or POE domain is less than 100 nm and decreases with the increase in the proportion of POE. The LiClO-doped copolymer₄ with a ratio (OE / Li = 20) has good mechanical properties and has the highest ionic conductivity at T = 30⁰C (σ = 2.10^~4 S / cm) currently known for the EPS studied.

The Li / Li battery cell⁺/ LiCoθ2 shows a discharge capacity at room temperature of 100 mAh / g at 0.1 C, the battery also has good charge / discharge reversibility.

This document therefore highlights a marked improvement in the ionic conductivity, which is however not yet similar to that of liquid electrolytes.

In addition, the copolymers of this document have very high number average molecular weights (M_not = 250,700 g / mol) implying very high viscosities. As a result, they are very difficult to implement with conventional techniques such as extrusion. In addition, the number of Li + transport is low, which leads to poor power handling and a significant drop in capacity beyond C / 10.

There is therefore, in view of the above, a need for a solid polymer electrolyte

(EPS) which has not only excellent mechanical and thermal properties, but also excellent conductive properties, and in particular a high and improved ionic conductivity compared with known solid polymer electrolytes which can be implemented with conventional methods of obtaining films.

There is in particular a need for a solid polymer electrolyte which is light, flexible, handy, easy to implement, which has good mechanical strength and which also has a high ionic conductivity in particular at room temperature. The object of the present invention is to provide a solid polymer electrolyte (EPS) which meets, inter alia, the needs listed above.

The object of the present invention is further to provide a solid polymer electrolyte (EPS) which does not have the defects, drawbacks, limitations and disadvantages of the solid polymer electrolytes of the prior art and which solves the problems of the solid polymer electrolytes of l prior art.

This object, and still others are achieved, in accordance with the invention, by a solid polymer electrolyte (EPS) which comprises at least one electrolyte salt, and at least one linear triblock copolymer ABA in which:

- the blocks A are polymers capable of being prepared from one or more monomers, chosen from styrene, o-methylstyrene, p-methylstyrene, mt-butoxystyrene, 2,4-dimethylstyrene, m-chlorostyrene, p-chlorostyrene, 4-carboxystyrene, vinylanisole, vinylbenzoic acid, vinylaniline, vinylnaphthalene, 9-vinylanthracene, alkyl methacrylates from 1 to 1OC, 4-chloromethylstyrene, divinylbenzene , trimethylol propane triacrylate, tetramethylolpropane tetraacrylate, alkyl acrylates from 1 to 1OC, acrylic acid, methacrylic acid.

- block B is a polymer capable of being prepared from one or more monomers chosen from ethylene oxide (OE), propylene oxide (OP), poly (ethylene glycol) acrylates ( APEG), and poly (ethylene glycol) methacrylates

(MAPEG).

The blocks A can be homopolymers capable of being prepared from a single monomer chosen from the monomers as listed above, or else they can be random copolymers capable of being prepared from several of the monomers mentioned. above.

In particular, the blocks A can be homopolymers capable of being prepared from a monomer chosen from styrene, o-methylstyrene, p-methylstyrene, mt-butoxystyrene, 2,4-dimethylstyrene, m- chlorostyrene, p-chlorostyrene, 4-carboxystyrene, vinylanisole, vinylbenzoic acid, vinylaniline, vinylnaphthalene, 9-vinylanthracene, alkyl methacrylates from 1 to 1OC, acrylic acid, methacrylic acid; or else the blocks A can be random copolymers capable of being prepared from a monomer described above and from one or more other monomers chosen from 4-chloromethyl styrene, divinyl benzene, trimethylolpropane triacrylate, tetramethylolpropane tetraacrylate , alkyl acrylates from 1 to 10 C, acrylic acid, methacrylic acid. Block B can be a homopolymer capable of being prepared from a single monomer chosen from the monomers listed above, or block B can be a random copolymer yes which can be prepared from several chosen monomers from the monomers listed above for block B.

The EPS according to the invention contain specific ABA type block copolymers whose implementation in EPS has never been described in the prior art.

The solid polymer electrolytes according to the invention exhibit a combination of mechanical and electrical properties, due essentially to the ABA copolymers used which has never been obtained until now. The EPS according to the invention in particular when they are in the form of films, membranes are flexible, flexible, have good mechanical strength and are easy to handle. In addition, surprisingly, they also have excellent electrical conductivity of up to 9.10, for example.^~4 S / cm^~2 at room temperature (i.e. typically 20⁰C to 30⁰C) which had never been reached in the prior art for solid electrolytes.

The solid polymer electrolyte according to the invention simultaneously and surprisingly satisfies the two fundamental requirements for a solid polymer electrolyte which are on the one hand a high ionic conductivity, and on the other hand excellent mechanical properties. These two characteristics were hitherto considered to be incompatible. The EPS according to the invention comprising the specific ABA copolymer described above therefore goes against a widely held prejudice in this field of technology and overcomes this prejudice.

In the EPS copolymers according to the invention, the blocks A for example of PS (polystyrene) give the EPS the excellent mechanical properties desired while the block B for example of POE provides them with the ionic conductivity.

ABA triblock polymers consist of two chemically dissimilar, therefore immiscible, polymers linked together by covalent bonds. Under certain conditions, a strong repulsion between the blocks induces phase microseparation characterized by the organization of microdomains into regular and periodic structures.

It has been unexpectedly demonstrated that the ABA triblock copolymers in which the block A represents respectively less than 30% by mass of the copolymer lead to a phase microseparation by forming microdomains as shown in FIG. 3 where we observe discrete domains of blocks A interconnected by blocks B.

According to the invention, the microstructuring of block copolymers in an EPS is used in a completely new and surprising manner. This microstructuring of the specific ABA copolymers used according to the invention seems to be the main cause leading to EPS exhibiting excellent mechanical properties.

Figures 4A and 4B show that the temperature range (T) for using EPS is lower than the Order-Disorder Temperature (T_ODT) block copolymers, and that it is combined with a high ionic conductivity.

Preferably, the blocks A are chosen from polystyrene blocks (PS), poly (1 to 10 C alkyl methacrylate) blocks, poly (acrylic acid) blocks, poly (methacrylic acid) blocks. , the statistical blocks of poly (styrene / acrylic acid), the statistical blocks of poly (styrene / methacrylic acid), the poly (alkyl methacrylate in 1 to CO 1 / acrylic acid) statistical blocks and the poly (alkyl methacrylate in 1 to CO 1 / methacrylic acid) statistical blocks. Preferably, the blocks B are chosen from blocks of poly (ethylene oxide) (POE), blocks of poly (propylene oxide) (POP), blocks of random POE / POP copolymers, blocks of poly ( poly (ethylene glycol) methacrylate), and poly (poly (ethylene glycol) acrylate) blocks.

Generally said poly (ethylene glycol) have from 2 to 5000 OE units.

Advantageously, the ABA triblock copolymer of EPS according to the invention is chosen from the following copolymers:

- the copolymers in which the block B is a block of POE and the two blocks A are blocks of poly (alkyl methacrylate in 1 to 10 C) (Formula (I)); - the copolymers in which the block B is a block of POE and the two blocks A are blocks of poly (acrylic acid) or else blocks of poly (methacrylic acid);

- the copolymers in which the block B is a block of POE and the blocks A are blocks of polystyrene;

- the copolymers in which the block B is a block of poly (poly (ethylene glycol) acrylate) or else of poly (poly (ethylene glycol) methacrylate) and the blocks A are polystyrene blocks; - the copolymers in which the block B is a block of poly (poly (ethylene glycol) acrylate) or else of poly (poly (ethylene glycol) methacrylate) and the blocks A are blocks of poly (acrylic) acid.

- the copolymers in which the block B is a block of poly (poly (ethylene glycol) acrylate) or else of poly (poly (ethylene glycol) methacrylate) and the blocks A are blocks of poly (alkyl methacrylate in 1 to 10 C) or poly (methacrylic acid).

The EPS copolymer according to the invention can correspond to one of the following formulas (I) (II) (III) (IV):

<img file="WO2007113236A1_D0005.tif" />

Ri = al kyle group Cl to Cl O

<img file="WO2007113236A1_D0006.tif" />

(H)

<img file="WO2007113236A1_D0007.tif" />

(III)

<img file="WO2007113236A1_D0008.tif" />

(IV)

in which m is an integer from 5 to 1000, n is an integer from 2 to 5000, p is an integer from 2 to 50, Ri represents an alkyl group from 1 to 1OC, and R represents H or CH₃.

The most preferred copolymers according to the invention are the copolymers in which the block

B is a block of POE and the blocks A are blocks of polystyrene, namely the copolymers PS-b-POE-b-PS

(Formula (II)).

Advantageously, the proportion of blocks A, for example of PS is less than or equal to 35%, preferably less than or equal to 30%, more preferably strictly less than 30%, better still less than or equal to 25% by mass relative to the total mass of the copolymer. Preferably, the proportion of blocks A, for example of PS, is from 10 to 35%, more preferably from 15 to 30%, better still from 20 to 25% by mass of the total mass of the copolymer.

The number-average molecular mass of each of the blocks A, for example of PS, is generally from 500 g / mol to 30,000 g / mol, preferably from 1000 g / mol to 10,000 g / mol, more preferably from 1,500 to

3000 g / mol for example 1800 g / mol.

The blocks A of the EPS copolymer according to the invention can be a photocrosslinkable or heat crosslinkable polymer in order to improve the mechanical properties of the EPS while retaining good ionic conduction of the matrix due to block B.

In other words, the blocks A can be photocrosslinked or thermocrosslinked after the nanostructuring and the preparation of the EPS.

The molecular mass (number average) of the block B for example of POE is generally from 2000 g / mol to 200000 g / mol, preferably from 5000 g / mol to

20000 g / mol, more preferably from 8000 to 15000 g / mol, for example 10000 g / mol.

The number-average molecular mass of the EPS copolymers according to the invention is generally from 2,500 g / mol to 260,000 g / mol, preferably from 10,000 g / mol to 50,000 g / mol, more preferably from 12,000 to 30,000 g / mol , for example 13600 g / mol.

The ABA triblock copolymers used according to the invention can be prepared by known methods.

The EPS copolymers according to the invention, in particular the PS-POE-PS copolymers can in particular be prepared by a method, an NMP process or an ATRP process.

In the following, the synthesis of PS-b-POE-b-PS triblock copolymers is essentially illustrated, but it is obvious that these synthesis methods can also be applied to the other block copolymers according to the invention with some adaptations to the scope of the skilled person in this technical field. The NMP method consists in first synthesizing a POE-based macroalkoxyamine and then in polymerizing styrene.

Several synthetic routes have been developed. The first consists of a coupling between the alkoxyamine AMA-SGl (V) and the dihydroxylated POE via the

N, N '-Dicyclohexyl-Carbodiimide (DCC) and 4-

Dimethylaminopyridine (DMAP) to form the difunctional macroalcoxyamine SGl-AMA-POE-AMA-SGl

(VI). The PS-POE-PS triblock copolymer is obtained by polymerization of styrene in the presence of the difunctional macroalkoxyamine at 110⁰vs.

<img file="WO2007113236A1_D0009.tif" /> b JPS

<img file="WO2007113236A1_D0010.tif" />

(V) Note that SGl designates the fragment

<img file="WO2007113236A1_D0011.tif" />

The second consists of a coupling between an acryloyl halide and the dihydroxy POE in the presence of triethylamine to form a poly (ethylene oxide) diacrylate (VII). The difunctional macroalkoxyamine SG1-MAMA-POE-MAMA-SG1 (IX) is then obtained by 1,2 addition reaction of MAMA-SG1 (BlocBuilder ™ (VIII)) on poly (ethylene oxide) diacrylate. The PS-POE-PS triblock copolymer is obtained by polymerization of styrene in the presence of the difunctional macroalkoxyamine at 110⁰vs.

<img file="WO2007113236A1_D0012.tif" />

<img file="WO2007113236A1_D0013.tif" /> (Flight)

The ATRP method consists first of all in coupling the bromoisobutyryl bromide and the dihydroxylated POE in the presence of triethylamine to form the difunctional macro-initiator Br-POE-Br. The PS-POE-PS triblock copolymer is produced by priming styrene with the difunctional macroinitiator at 110⁰C in the presence of CuBr and N- [2- (Dimethylamino) ethyl] N, N ', N' -trimethyl- 1.2-ethanediamine (PMDETA) as ligand.

CuBi / PMDCTΛ Bi IVb-PfCU₁-PS

<img file="WO2007113236A1_D0014.tif" /><img file="WO2007113236A1_D0015.tif" /> The solid polymer electrolyte of the present invention comprises at least one ABA copolymer as described above and an electrolyte salt.

One can use, for example, a single ABA copolymer; a mixture of several ABA copolymers, each with different structural units; or a mixture of at least one ABA copolymer and at least one other copolymer (which is not an ABA) and / or of a homopolymer. Said other copolymer or homopolymer is chosen, for example, from PEOs, PSs, PS-b-PEOs, preferably a PEO is chosen.

A preferred solid polymer electrolyte comprises a linear triblock copolymer ABA for example PS-PEO-PS and a PEO, and of course an electrolyte salt. The electrolyte salt used in

1 solid polymer electrolyte according to the invention can be any electrolyte salt known to those skilled in the art.

Examples of these salts include alkali metal salts, quaternary ammonium salts such as (CH₃) ₄NBF₆, quaternary phosphonium salts such as (CH₃) ₄PBF₆, transition metal salts such as AgClO₄, or acids such as hydrochloric acid, perchloric acid, fluoroboric acid, phosphoric acid, and sulfuric acid.

Examples of the electrolyte salts include conventional alkali metal salts such as LiCF₃SO₃, LiB (C₂O₄) ₂, LiN (CF₃SO₂) 2, LiC (CF₃SO₂) ₃, LiC (CH₃) (CF₃SO₂) ₂, LiCH (CF₃SO₂) ₂, LiCH₂(CF₃SO₂), LiC₂F₅SO₃, LiN (C₂F₅SO₂) ₂, LiN (CF₃SO₂), LiB (CF₃SO₂) ₂, LiPF₆, LiSbF₆, LiClO₄, LiSCN, LiAsF₆, NaCF₃SO₃, NaPF₆, NaClO₄, NaI, NaBF₄, NaAsF₆, KCF₃SO₃, KPF₆, Kl, LiCF₃CO₃, NaClO₃, NaSCN, KBF₄, KPF₆, Mg (ClO₄) ₂, and Mg (BF₄) ₂ and their mixtures.

Lithium salts are particularly preferred. The amount of electrolyte salt added defined by the ratio [central block B such as EO / Li (in mole), is generally in the range of 0.01 to 200, preferably 0.02 to 100, more preferably 15 to 30. The solid polymer electrolyte according to the invention can also comprise a mineral filler. This mineral filler is generally chosen from oxides such as SiO₂, TiO₂, Al₂O₃ and their mixtures. Generally, this mineral filler is in the form of nanoparticles.

The mineral filler generally represents from 1 to 20%, preferably 1 to 15% by weight of the EPS.

A solid polymer electrolyte according to the invention can be prepared by a process in which the ABA copolymer and the electrolyte salt are dissolved, in the desired [OE] / Li ratio, in an adequate solvent chosen, for example, from tetrahydrofuran, methyl- ethyl ketone, acetonitrile, ethanol, dimethyl formamide, CH₃CN, CH₂Cl₂ and their mixtures.

The solution obtained generally has a concentration of 1 to 20% by weight, for example 5% by weight. It is then possible optionally to add to said solution the mineral filler, for example of TiO₂, SiO₂, or Al₂O₃ preferably in the form of nanoparticles. The solution obtained after the optional addition of the mineral filler generally has a concentration by weight of 1 to 20% by weight, for example 10% by weight. Said solution can then be homogenized for a period generally of 15 min to 10 hours, for example two hours, and the solvent is evaporated by slow evaporation.

Alternatively, the solid electrolyte can be prepared by a process in which the copolymer and the electrolyte salt are mixed mechanically either at room temperature or with heating.

The solid polymer electrolyte thus prepared can then be put into any desired form, for example in the form of a membrane, of a film, or of a sheet with a thickness for example of 10 to

200 μm.

To prepare a solid electrolyte in the form of a sheet, film or membrane, any known technique can be used such as centrifugal coating (“spin coating”), roller coating, application curtain coating, extrusion, etc.

For example, an EPS solution containing a copolymer, an electrolyte salt and optionally a filler is deposited on a substrate, the solvent is evaporated to form a film on said substrate and then the substrate is separated from the film or membrane.

EPS can undergo heat treatment for example at a temperature of 40 to 100⁰C for a period of 2 hours to 300 hours, for example for 96 hours to 50⁰vs.

The invention also relates to a cell of a rechargeable battery or accumulator comprising an anode and a cathode between which is interposed a solid polymer electrolyte as described above.

Preferably, the anode is made of metallic or carbon-based lithium and the cathode is made of a lithium insertion compound.

Embodiments of the invention will now be described in the following, in particular with reference to examples given by way of illustration and not limitation. This description is made in relation to the accompanying drawings, in which:

- Figure 1 is a schematic view of an elementary cell of a lithium battery during discharge. - Figure 2 is a schematic view of an elementary cell of a lithium battery during charging.

- Figure 3 is a schematic view which shows the structure of ABA block copolymers in which the block A represents less than 30% by weight of the copolymer.

- Figure 4A is a schematic view which represents the microstructuring of ABA block copolymers at a temperature T higher than the order-disorder temperature (T_ODT) of these ABA block copolymers. - Figure 4B is a schematic view which represents the microstructuring (on a scale of 10 to

100 nm) ABA block copolymers at a temperature T lower than the order-disorder temperature (T_ODT) of these ABA block copolymers.

FIG. 5 is an AFM (“Atomic Force Microscopy”) image of the thin film of the PS-POE-PS copolymer of Example 3: 5, 6K-10K-5, 6K (48% by weight of POE) ditto Figure 6 - Figure 6 is an AFM image of a thin film of the PS-POE-PS copolymer of Example 4: 1.8K-IO-I, 8K (75% by weight of POE). The scale shown in the image is 200 nm.

Figure 7 is a differential scanning calorimetry (DSC) graph which shows the influence of the size, length of the POE blocks on the melting temperature T_f of the POE block of various copolymers: namely: a POE-Br2 (Precursor X, difunctional POE) (curve A); a PS-POE-PS copolymer at 75% by weight of POE (curve B); a PS-POE-PS copolymer containing 56% POE (curve C); and a PS-POE-PS copolymer containing 25% POE (insert curve).

On the abscissa is plotted the temperature T (in ⁰C) and on the ordinate is the heat flux (in W / g).

FIG. 8 is a graph of differential scanning calorimetry (DSC) which shows the influence of microstructuring on the melting temperature T_f of the POE block of various copolymers, PS-POE-PS (9, 7K-10K-9, 7K). Namely: a precipitated, non-nanostructured polymer having undergone a first heating cycle (curve A), a precipitated, non-nanostructured polymer having undergone a second heating cycle

(curve B); and finally a microstructured film obtained by casting with toluene (curve C).

FIG. 9 is a graph of differential scanning calorimetry (DSC) which shows the influence of the proportion of addition of the lithium salt in an EPS prepared with the copolymer of example 4. Namely: copolymer with [OE] / Li = 30 (curve A), copolymer without Li (curve B) and copolymer with [OE] / Li = 15 (curve C).

FIG. 10 is a schematic sectional view of a “Swagelok” type cell used for measuring the conductivity of EPS films.

Figure 11 is a graph showing the conductivity of various EPS films based on the PS-POE-PS copolymer (1, 8K-10K-1, 8K). Namely an EPS with a ratio [OE] / [Li] = 30 (curve with •); an EPS with a ratio [OE] / [Li] = 15 with addition of TiO2 (curve with O); and finally a reference POE (molecular weight from 20,000 to 40,000) (curve with •).

The conductivity is plotted on the ordinate (in S. cm^"1) and on the abscissa is protected 1000 / T (in ÎO ^ .K^"1). - Figure 12 is a graph showing the conductivity of various EPS as a function of temperature.

Namely the EPS of JANNASH [3] (PFS-PEGPG-PFS) (curve A), the EPS of NIITANI [4] (PFS-PEGPG-PFS) (curve B), and finally the EPS according to invention (curve C). On the ordinate, the conductivity is plotted (log / σ in S / cm) and on the abscissa is plotted 1000 / T (K^"1) .

Example 1 Synthesis of the Macroalkoxyamine SGl-AMA-POE-AMA-SGl (VI)

In a 100 ml two-necked flask, 15 g of POE α, ω hydroxylated (Mn = 10,000 g / mol), 2.2 g of alkoxyamine AMA-SGl (2 equivalents), 0.37 g of DMAP (1 equivalent) are solubilized in 45 mL of dichloromethane. The reaction mixture is degassed by bubbling nitrogen for 10 minutes. Using a syringe, 1.5 g of DCC (2.4 equivalent) dissolved in 5 ml of dichloromethane are added dropwise to the reaction mixture at a temperature of 0⁰C. It is left to react for 20 hours, then the reaction mixture is filtered to remove the dicyclohexylurea formed. Then the filtrate is precipitated in diethyl ether. The macroalkoxyamine SGl-AMA-POE-AMA-SGl (VI) is recovered by filtration and then dried under vacuum. The coupling rate determined by NMR¹H is 98%.

Example 2: Synthesis of the macroalkoxyamine SGl-MAMA-POE-MAMA-SGl (IX) In a three-necked flask, 10 g of POE α, ω hydroxylated (Mn = 10,000 g / mol), 1.4 ml of triethylamine are dissolved in 40 mL of dichloromethane. The reaction mixture is degassed by bubbling nitrogen for 20 minutes. Using a dropping funnel, dropwise introduced at a temperature of 0⁰C, 0.9 mL of acryloyl chloride dissolved (5 equivalent) in 10 mL of dichloromethane. It is left to react for approximately 15 hours. The reaction mixture is filtered to remove the triethylammonium chloride. The filtrate is washed twice with 20 ml of a saturated aqueous solution of NaHCU3. The organic phase is precipitated in diethyl ether. The POE diacrylate is recovered by filtration and then dried under vacuum. NMR analysis¹H shows a coupling rate greater than 95%. Then 2 g of POE diacrylate are introduced into a "Schlenk" fitted with a "Rotaflo". 0.16g (4.2mmol) of MAMA-SGl (VIII) dissolved in 6mL of THF is introduced onto the POE diacrylate. The suspension is deoxygenated by bubbling nitrogen through for 30 minutes. The "Schlenk" is immersed in an oil bath thermostatically controlled at 100⁰C for 1 hour. THF and evaporated in vacuo at room temperature.

RNM analysis ¹H shows a radical coupling rate around 85%. RNM analysis³¹P shows the disappearance of the methacrylic acid-SG1 alkoxyamine (27.4 ppm) and the appearance of dialkoxyamine at 24.23 ppm (majority diastereomer, 69%) and at 24.6 ppm (minority diastereomer, 31%).

Example 3 Synthesis of PS-POE-PS Block Copolymers of Molar Mass (5600 g / mol-10000 g / mol-5600 g / mol)

In a 100 mL three-necked flask, 6.3 g of macroalkoxyamine (VI), 15 g of styrene and 10 g of toluene are introduced at room temperature. After 20 min of degassing by bubbling nitrogen, the reaction medium is brought to 110⁰C and maintained at this temperature by thermal regulation for 5 h. The PS-POE-PS copolymer is recovered by precipitation in ether, filtered and dried under reduced pressure at room temperature. The mass percentage of POE in the copolymer is 48% and the M_not = 21200 g / mol.

Example 4 Synthesis of PS-POE-PS Block Copolymers with Molar Mass (1800 g / mol-10000 g / mol-1800 g / mol)

In a 100 ml three-necked flask, 6 g of macroalkoxyamine (VI) 9 g of styrene and 15 g of toluene are introduced at room temperature. After 20 min of degassing by bubbling nitrogen, the reaction medium is brought to 110⁰C and maintained at this temperature by thermal regulation for 150 min. The PS-POE-PS copolymer is recovered by precipitation in ether, filtered and dried under reduced pressure at room temperature. The mass percentage of POE in the copolymer is 75% and the M_not = 13600g / mol.

Example 5: Preparation of a thin film of the copolymer

The copolymer prepared in Example 4 or in Example 5 is dissolved in toluene at a concentration of 10% w / v. The solution is filtered on a 0.45 μm filter and then deposited on a silicon wafer by spin-coating (200 rpm for 10 s). The solvent is evaporated slowly under a bell at room temperature. The films have a thickness of the order of 40 nm. AFM analyzes were performed on an AFM Dimension 3100^R (Veeco Instruments ") operated in" tapping "mode at room temperature. Example 6

The thin films prepared in Example 5 are observed by AFM. The AFM (“Atomic Force Microscopy”) images of the different thin films obtained are presented in FIGS. 5 to -9-6 respectively for the copolymers 5, 6K-10K-5, 6K (48% POE) and 1, 8K-10K-1, 8K (75% POE).

Whatever their topology, these well defined copolymers are organized in a conventional manner and in accordance with the literature.

An organization with different orientations can be observed, depending on the surface energy of the blocks and that of the substrate, for example cylinders oriented parallel or perpendicular to the substrate are observed.

More specifically, the film of the copolymer of Example 3 (5,6K-10K-5,6K) with 48% by weight of POE is lamellar (Fig. 5), and the film of the copolymer of Example 4 (1, 8K-10K-1, 8) with 75% by weight of POE has polystyrene cylinders 18 nm in diameter (Fig. 6).

The copolymers prepared in Examples 3 to 4 are also characterized by modulated DSC (Figures 7 and 8). All copolymers have two glass transition temperatures T_g distinct indicating the immiscibility of these two blocks.

The T_g PS blocks (94 ° C) is close to that of homoPS (T_g = 100⁰C), while the T_g of the POE block is much higher (around 9 ° C) than that of homoPOE (T_g ) = -56 ° C). This can be explained by the fact that the POE block is the central block of a triblock copolymer, therefore its properties would be different from those of a homopolymer. FIG. 7 shows that the length of the PS blocks inhibits the crystallization of the POE block and consequently indicates a decrease in the melting temperature (Tf) of the POE when the length of the PS blocks increases. We also observe the influence of nanostructuring on the POE melting temperature.

For the same copolymer, the “organized” film has a T_f lower than that of an unorganized film

(Figure 8). It is noted that the heat treatment facilitates the self-organization of the chains; indeed, a second T_f, assigned to the organized areas of the sample, appears during the second heating cycle.

Example 7

In this example, a solid polymer electrolyte (EPS) is prepared with the copolymer of Example 4 which is mixed with the salt LiN (CF₃SO₂) 2 (LITFSI). The [EO] / [Li] ratio is 30. A film is then made with the EPS thus prepared in the following manner: 0.5 g of PS-POE-PS copolymer (Mn = 13,600 g / mol) and 0 .08 g

(OE / Li = 30) of LiN (CF₃SO₂) ₂ are dissolved in 5 ml of a mixture of acetonitrile-dichloromethane (60:40 v / v). The homogeneous solution is then spread on a Teflon support. The solvent is evaporated at room temperature for 24 hours, then at 60⁰C vacuum for 24 hours. A uniform solid polymer electrolyte film is obtained having a thickness of the order of 110 μm. The film is mounted on a "Swagelok" type impedance measuring cell.

Example 8

In this example, a solid polymer electrolyte (EPS) is prepared with the polymer of Example 4 which is mixed with the salt LiN (CF3SO2) 2 • The ratio [OE] / [Li] is 15. The conditions of the manufacture of EPS are similar to those of Example 7.

A film is then made with the EPS thus prepared in the same manner as in Example 7. A DSC analysis of the EPS of Examples 7 and 8 is carried out: it clearly appears that the copolymer with [OE] / [Li] = 15 has much more crystalline area.

Example 9

A solid polymer electrolyte and a film of this EPS are prepared under the same conditions as in Example 7, but an inorganic filler which is TiO is added.₂ in a proportion of 10% of the solid polymer electrolyte.

Solid polymer electrolyte films

(EPS) of examples 7 to 9 are mounted in a “Swagelok” type conductivity measuring cell such as that shown in FIG. 13. In such a cell, a film (11) of the solid polymer electrolyte is placed between two stainless steel pistons (12) provided with a spring (13). The measurements are carried out by impedance spectroscopy first towards low temperatures, then, secondly, towards higher temperatures before returning to ambient temperature, the range of measurement frequencies extends from 0, 1 Hz to 100 kHz. For each temperature a 24 hour stabilization period was used before taking the measurement. The ionic conductivity is calculated by the relation: σ = 1 / (RxA) where

- 1 is the thickness of the film - A is the surface of the cell

- R is resistance.

The results of the conductivity measurements obtained are presented in Figure 11 where the evolution of the conductivity has been plotted (in S. cm^"1) as a function of the temperature for the various EPS films studied.

For a salt concentration, the addition of Tiθ2 hardly improves the ionic conductivity of the EPS, however the presence of Tiθ2 provides mechanical strength to the film with high salt concentration (EO / Li = 15).

Over the temperature range studied, there is a slight hysteresis phenomenon and a change in slope for the film having OE / Li = 30. (characteristic of the fusion of the crystallized domains of PEO). The conductivity increases by more than 2 orders of magnitude for the film with EO / Li = 30 and 1 order of magnitude for the film with EO / Li = 15 during the second passage of the sample towards the high temperatures. This improvement is attributed to the nanostructuring of the film facilitated by the heat treatment.

The best conductivity at room temperature obtained in this study is equal to

9.10^~4 S / cm for an EPS composed of triblock copolymers

PSi, 8κ-POEi_okay-PSi, 8κ (75 wt% POE) doped with LITFSI at an OE / Li salt concentration = 15.

In Figure 12, the conductivity of various EPS is shown as a function of temperature. Namely the EPS of JANNASH [3] (PFS-PEGPG-PFS) (curve A), the EPS of NIITANI [4] (PFS-PEGPG-PFS) (curve B) and finally the EPS according to the invention (curve C) (EPS of Example 8).

It should be noted that the EPS according to the invention has a conductivity greater than that of the EPS of the prior art, in particular at ambient temperature (vertical dotted line).

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