CA2514783C - Rechargeable electrochemical accumulator - Google Patents

Abstract

The invention relates to a metallic lithium rechargeable electrochemical accumulator, comprising at least one lithium metal electrode and at least one polymeric electrolyte gel. Said accumulator is capable of operating at temperatures from - 20 to 60 ·C, essentially without formation of lithium dendrites on the whole surface of the metallic lithium electrode. The above is also characterised by a particularly long life, even with intensive use at low temperature. Said inventive rechargeable accumulator can be produced by use of a production method with particular application of temperature control during the specific production stages. As a result of the extremely high electrochemical performance of said accumulator, in particular the remarkable stability thereof, said accumulator can be used in new application fields such as hybrid vehicles, electric vehicles and emergency supply systems such as those of the UPS type.

Description

RECHARGEABLE ELECTROCHEMICAL GENERATOR
FIELD OF THE INVENTION

The present invention relates to a rechargeable electrochemical generator at lithium metal having at least one lithium type electrode metallic and minus a gel polymer electrolyte.

The invention also relates to a method of preparing this generator and the use of it notably as a source of current in vehicles hybrid electric, electric vehicles or UPS.

BRIEF DESCRIPTION OF THE PRIOR ART
It is known to use metallic lithium in primary batteries to base of MnO2 as cathode. These batteries are used in the field of electronics, by example in watches as back up of memory. Because of the formation of lithium dendrites, these batteries are not rechargeable. This phenomenon undesirable seems caused by the use of liquid electrolytes, associated with this technology.

A technology known as ACEP has been developed by Hydro-Québec for try to solve the problem of forming dendrites. This technology who uses however, a dry polymer has only partially solved this problem. In effect, the normal operation of this technology remains at temperatures greater than 60 Celsius.

US-A-6,190,804 to Dai-Ichi Kogyo Seiyaku Co. discloses electrochemical generators having a solid electrolyte. The electrolyte solid is obtained by dissolving a tetrafunctional compound of specific formula and high weight molecularly with an electrolytic salt in a solvent and then realizing the crosslinking of the solution. Generators prepared according to the technology described in this patent have the disadvantage of only operating at so-called temperatures hot.

2 US-A-6,517,590 in the name of Hydro-Quebec describes the use of agents lubricants to improve performance at the rolling stage of the movie constituent of the electrode and at the level of the film covering the anode. The generators described However, in this document there is also a limitation regarding regards their use at low temperatures.

International application WO 03/063 287 in the name of Hydro-Québec describes a polymer electrolyte which may be in the form of a gel and which has a stability Electrochemical greater than 4 volts when used as an electrolyte for some hybrid supercapacitors and for electrochemical generators. The generators corresponding lithium standards, however, have limitations when recharge the battery, we then witness the formation of lithium dendrites.

There is therefore a need for new rechargeable generators without of the disadvantages usually associated with electrochemical systems of art prior.
There is also a need for rechargeable generators, presenting a duration of extended life, and stable even under unusual conditions of use as temperatures below 60 Celsius and can even be as low that- 20 Celsius.

SUMMARY OF THE INVENTION

The present invention meets the needs mentioned above by providing a Rechargeable lithium metal electrochemical generator comprising at least one lithium metal electrode and at least one gel polymer electrolyte.
This generator is able to operate at temperatures between - 20 and 60 Celsius, substantially without formation of lithium dendrites on the total surface electrode of metallic lithium type. It is also characterized by a lifetime remarkable even in intensive use at low temperatures.

3 The generator according to the invention is therefore very stable in operation and present unec particularly long service life, associated in particular with the virtual absence of -formation of lithium dendrites even under conditions of use adverse such as many cycling carried out at lower temperatures, lower at 60 Celsius.

This new rechargeable generator can be obtained by implementing a process of manufacturing involving in particular a control of the temperatures applied in of the specific stages of manufacture.
Because of its very high level of electrochemical performance, particular of his remarkable stability, this generator is usable in new areas applications such as hybrid vehicles, electric vehicles and the systems emergency power supply, for example those of UPS type. In fact, this new generator can be used in any type of application and even outdoors in regions cold.

The invention as well as its advantages will come out better on reading the description detailed and non-restrictive that follows, made with reference to the drawings attached.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram showing the internal structure of a generator rechargeable according to the invention comprising three base films including anode film with base of lithium, a separator film and a cathode film, the generator comprising also a movie of SEI (Solid Electrolyte Interface) passivation formed on the surface of the film basis of lithium and on the surface of the cathode film after crosslinking a electrolytic composition.

FIG. 2 is a diagram illustrating an embodiment of a method of manufacture of a lithium battery according to the invention in which lithium metallic Extruded and / or laminated is used with or without a current collector.

4 Figure 3 is a cycling curve of a battery prepared according to the invention, illustrating the stability of the lithium metal interface obtained with a prepared gel polymer by setting of a method according to the invention and tested in a rechargeable generator made as described in Example 1 below.

Figure 4 is a cycling curve comparing high-speed discharges a rechargeable lithium metal battery with those of a lithium-ion battery using a polymer gel electrolyte, the preparation of the components of this battery being described in Example 2 below.
Figure 5 is a cycling curve of an electrochemical generator rechargeable prepared according to the process of the invention hereinafter described in Example 3, if it's only the crosslinking temperature of the crosslinkable polymer / plasticizer / salt mixture of lithium is greater than the preparation temperature by rolling of the lithium film metallic.

Figure 6 is a photograph of two pressure devices (press cells) manufactured by Hydro-Québec, one of these devices being shown under form assembled, the other in disassembled form with a test battery positioned at interior one of his lids. These devices make it possible to control the pressure dynamic exerted on a battery placed inside the device, in the location provided for this effect. As illustrated, they are each composed of two lids interlocking are secured using four screw nut systems. When the device is assembled, the piston which passes through one of the covers exerts pressure on battery tested, the movement of the piston being ensured by an air inlet.

DETAILED DESCRIPTION OF THE INVENTION

In the context of the present invention, the term polymer electrolyte gel a visco-elastic mass formed from a colloidal suspension which comprises at at least one cross-linkable polymer, at least one plasticizing solvent and at least one salt of lithium. The degree of crosslinking of the crosslinkable polymer (s) present in the gel is usually between 5 and 40% at room temperature.

In the context of the present invention, the term plasticizing solvent is understood to mean of a polymer crosslinkable an organic compound or a mixture of organic compounds able to solubilize the crosslinkable polymer and improve the plasticity of the polymer electrolyte gel obtained by crosslinking of this crosslinkable polymer, in admixture with the solvent plasticizer and with an ionic salt. The crosslinking step is carried out substantially without evaporation of the plasticizing solvent. The plasticizing solvent also for purpose to improve the ionic conductivity of the obtained gel polymer electrolyte, and this, in especially at low temperature of use.

A first object of the present invention resides in a generator electrochemical rechargeable lithium metal battery having at least one type electrode lithiur-11 metal and at least one gel polymer electrolyte, this generator being apt to operate substantially without dendrite formation on the total surface Electrode lithium metal type present in said generator.

More specifically, the invention as claimed resides in a generator electrochemical rechargeable lithium metal battery having at least one electrode made of a metallic lithium film or an alloy intermetallic rich in lithium and at least one cathode separated by a separator, each in the form of a film, said separator being impregnated with an electrolyte polymer gel, said generator being characterized in that the face of the electrode look electrolyte carries a passivation film and in that the electrolyte gel polymer occupies the space between the electrodes and the separator, as well as the porosities of the materials forming the electrodes and the separator.

5a This generator is characterized by the fact that it is likely to operate, to temperatures between - 20 and 60 Celsius, substantially without formation of dendrites (the lithium on the total surface of metal lithium type electrode.

Preferably, this rechargeable generator is designed so that after cyclings, the formation of lithium dendrites is only on less than 1%, from ln total area of lithium metal electrode, The stability of the generator with respect to the dendrites is evaluated by calculating the evolution of the coulombic efficiency of the generator during the cycles. To do this, we alternates lets load and discharge tests. It is considered that there is no formation of dendrites when the coulombic efficiency remains between 90 and 100%. When this efficiency drops below (the 90%, there is appearance of parasitic phenomena at level = ri of the structure of the generators. When coulombic efficiency exceeds 100 %, there is dendrites that have formed and then we measure the surfaces contaminated. The surface covered with dendrites is quantified using a microscope scanning electronics.

Preferably also, the rechargeable generator according to the invention is designed to way to have a stability such as cycling, after 200 cycles, that the dendrites of lithiuin formed occupy less than 1% of the total area of lithium-type metallic.

According to an advantageous embodiment of the present invention, the generator has at least three films. The first film constitutes an electrode positive. The second metal lithium film constitutes a negative electrode, while the third film acts as a separator between the positive electrode and electrode negative.
In this generator, the film that constitutes the positive electrode is advantageously consisting of a film of LiFePO4, LiCoO2, LiNiO2, Li4Ti5O12 or a mixture of these last. More advantageously, we will retain the positive electrodes whose film is made from a mixture of at least two LiCiO 2 LiNiO 2 compounds, LiFePO4 and Li4Ti5O12.

The lithium-based negative electrode is preferably a film of lithium metal and / or a mixture of lithium-rich intermetallic alloy such one lithium-aluminum, lithium steel, lithium-Sn and lithium-Pb mixtures. As examples mention may be made of lithium-rich intermetallic alloy mixtures which behave about 8% aluminum.

The separator is advantageously constituted of a film chosen from the group consisting of polyethylene, polypropylene, polyether and polyethylene / polypropylene.

More preferably, the rechargeable electrochemical generator according to the invention is designed to operate between 1.5 and 5 volts. The operating voltage is function of material used for example with LiFePO4 it is of the order of 3.5 volts, with LiCoO2 of the order of 3.7 Volts, with Li4Ti5O12 of the order of 1.5 Volts and with LiNiO2 of the order of 3.8 Volts.

According to the invention, a gel polymer electrolyte occupies not only the cavities that exist inside the generator between the electrodes and the separator, but also the porosities that exist inside the electrodes and the separator.

This gel polymer electrolyte is advantageously obtained by crosslinking a electrochemical composition consisting of at least a part of the polymer (s) crosslinkable agent (s) present in a crosslinkable polymer / solvent mixture plasticizer / salt lithium. The crosslinking is carried out with or without auxiliaries of crosslinking, preferably in situ, after constitution of the electrochemical generator rechargeable.
In practice, the crosslinkable polymer used is advantageously under solid form or liquid and the lithium salt is advantageously in solid form, like example in the form of a powder.

The plasticizing solvent in liquid form has in particular for function of Dissolve the crosslinkable polymer, and increase the conductivity electrochemical the polymer gel electrolyte, as well as its plasticity.

According to an advantageous variant, the crosslinking of the composition electrochemical is carried out in the presence of at least one additive, of organic nature and / or inorganic, likely to improve the mechanical characteristics such that the holding mechanics of separator between electrodes and / or system security electrochemicals in which gel electrolyte polymer is present.

Preferably the crosslinkable polymer is selected from the group of polymers crosslinkable to four branches. This crosslinkable polymer is then present alone or in combination with another component of polymeric or non-polymeric nature.

In the latter case, the crosslinkable four-branched polymer has preferably say hybrid terminations. Among the hybrid terminations envisaged one can mention the hybrid terminations acrylates (preferably methacrylate) and alkoxy (from preference alkoxy groups with 1 to 8 carbon atoms, more preferentially methoxy or ethoxy groups), or vinyl. At least one branch of polymer with four branches, and preferably at least two branches of polymers retained are likely to give rise to crosslinking.

Such four-branched polymers are extensively described in US patent 6,190,804 as well as in the international application WO 03/063 287.

The crosslinkable polymer may advantageously be associated with at least one component chosen in the following families poly (vinylyldienefluoride), also called (PVDF), of formula (CH2-CF2) r, in which n advantageously varies between 150 and 15,000, preferably n is greater than 1,500 and less than 4,000, more preferably still n is close to 2,300. Among these polymers, those having an average molecular weight of between 10,000 and 1 million, more preferably still those having a molecular weight average between 100,000 and 250,000;

poly (vinylydiene fluoro-co-hexafluoropropene) copolymers, of formula [(CH2-CF2), (CF2-CF (CF3)) 1, also known as (PVDF-HFP), in which n varies from 150 to 15,000, preferably n ranges from 1,500 to 4,000, more preferentially n is close to 2.300 and x preferably varies between 0.92 and 0.85. Among these polymers, those having a molecular weight average between 10,000 and 1 million, even more preferentially having an average molecular weight of between 100,000 and 250,000;

poly (tetrafluoroethylene), also called (PTFE), of chemical formula (CF2-CF2) n wherein n varies from 5 to 20,000, preferably with n varying of 50 to 10,000. Of these polymers, those having a molecular weight are preferred average between 500 and 5 million, more preferably still those having an average molecular weight of between 5,000 and 1,000,000, dt--preferably about 200,000;

poly (ethylene-co-propylene-co-5-methylene-2-norbornene) or ethylene propylene-diene copolymers, also called EPDMs, preferably those with an average molecular weight between 10,000 and 250,000, plus preferably between 20,000 and 100,000;

polyols such as:

polyvinyl alcohol with an average molecular weight of preferably between 50,000 and 1 million, or a cellulose, of preferably of average molecular weight between 5,000 and 250,000 part of the OH groupings is replaced by groupings OCH3, OC2H5, OCH4OH, OCH2CH (CH3) OH, OC (= O) CH3, or OC (= O) C2H5, and / or the condensation products of ethylene oxide, preferably those having an average molecular weight of between 1,000 and 5,000, preferably pure or in admixture with propylene oxide on glycerol or trimethylolpropane, and optionally cross-linked by a or tri-isocyanate of formula (O = C = N) - R with 2 <x <4 and R representing an aryl or alkyl group ensuring the polyfunctionality with the group (O = C = N).

poly (methylmetacrylate) also called (PMMA), of formula [(CH 2) C (CH3) / (CO2CH3)] n, wherein n preferably ranges from 100 to 10,000, more preferably still with n varying from 500 to 5,000. Among these polymers, those having an average molecular weight of between 10,000 and 1 million, more preferably still those with a weight average molecular weight of between 50,000 and 500,000;

Poly (acrylonitrile), also called (PAN), of chemical formula [CH 2 CH (CN)] n with n varying from 150 to 18,800, more preferably still with n ranging from 300 to 4,000. Among these polymers, those having a weight average molecular weight between 10,000 and 1 million, more preferably those with an average molecular weight between 20,000 and 10,200,000;

oxides of SiO 2 -Al 2 O 3; and particles of nano TiO 2 coated or not with an organic material which is preferably compatible, ie stable and / or not generating any reaction secondary parasite.

The criteria that are taken into account in optimizing the choice of electrolyte gel polymer used in the context of the present invention are:
- low vapor pressure;
good compatibility with metallic lithium;
good compatibility with the additives of the ceramic, glass, inorganic and / or organic added preferably before crosslinking;
good ionic conductivity; and - a large electrochemical operating window which is located advantageously from 0 to 5 volts.

The plasticizer / four-branched polymer ratio, expressed by weight, varies from preference in the ratios 95/5 to 5/95. The quantity of the initiator expressed by report to the amount of crosslinkable polymer is from 100 to 5,000 ppm, preferably from 500 to 1,500 ppm of initiator.

It will be noted that the ionic conductivity of the gel polymer electrolyte varies in function of plasticizer / crosslinkable polymer ratio. The safety of the battery is also function of this report.
According to an advantageous embodiment, the amount of crosslinkable polymer represented between 1 and 95%, preferably between 5 and 50%, more preferably again about 10% by weight of the amount of the electrolytic composition at crosslinking.
The lithium salt used to prepare the gel electrolyte gel is advantageously of LiBF4, LiPF6, LiTFSI, LiBETI, LIFSI or is a mixture of at least two of these last. More preferably still, the lithium salt is chosen from group consisting of LiTFSI, LiFSI and mixtures of LiTFSI and LiFSI.
The lithium salt present in the liquid electrolytic solution represents an amount from 0.5 to 2.5, preferably from 1 to 1.7, relative to the amount of plasticizer.
The plasticizing solvent used to prepare the gel polymer electrolyte is, at illustrative title, selected from the group consisting of gamma-buturolactone (y-BL), tetrasulfonoamine (TESA), propylene carbonate (PC), ethylene carbonate (EC) and mixtures of these.

The plasticizing solvent may also consist of a mixture, as for example example a mixture of at least two solvents selected from the group consisting of BL, the TESA, the PC and the EC.

The plasticizing solvent may also be chosen from the ternary mixtures of group consisting of y-BL + EC + PC, y-BL + EC, y -BL + PC, TESA + PC and y-BL + TESA +
PC + EC, for example in a ratio (3: 1: 1).

In a particularly advantageous embodiment, the gel polymer electrolyte is constituted ei weight:
about 10% of the commercial four-branch ERM-1 ELEXCELTM polymer by DKS; and - about 90% of 1.5 Molar LiTFSi in (EC + y-BL) ratio (1: 3).

The electrochemical generator of the invention may advantageously comprise at least Moiras a crosslinking agent added to the crosslinkable polymer / solvent mixture plasticizer / salt lithium. This additive is of organic and / or inorganic nature and is chosen to improve the mechanical characteristics of the generator, such as holding mechanical separator between the electrodes and / or the operating safety of the generator. AT
illustrative of such an additive, mention may be made of titanium oxides, aluminum oxides and mixtures of at least two of these oxides. Such additives are habitually present in the crosslinkable composition to less than 10%, and preferably less than 5 % in weight.

According to a variant of the invention, the crosslinking of the crosslinkable polymer is conduct in presence of a crosslinking agent, preferably selected from the group of peroxy.
More particularly, the crosslinking is carried out in the presence of benzoyl peroxide.
The crosslinking agent is then present in a proportion of 500 to 5,000 ppm / polymer, of preferably at a rate of 1,000 to 3,000 ppm, more preferably still at reason about 2,000 ppm.

According to another advantageous embodiment, the crosslinking of the crosslinkable polymers is performed at a temperature of between 20 and 90 Celsius, preferably between 45 and 80 Celsius, more preferably still at room temperature.

In order to obtain a polymer electrolyte having the desired consistency of gel, the crosslinking crosslinkable polymer is advantageously produced for a period of time which is between 15 minutes and 72 hours, preferably between 1 and hours, more preferably still about 24 hours.

The crosslinking can be carried out using various energy sources.
For example, by irradiation with an electron beam, by ultra purple, by infrared or thermal radiation, or by the use of at least two of these techniques.

Advantageously, an infrared emitter or a source is used thermal. We can also successfully achieve electron beam crosslinking and without use crosslinking agent.

The realization of the crosslinking by infrared generates a heating of the composition electrolytic and in particular makes it possible to obtain a passivation film of stable lithium, especially when cycling the battery.

A second object of the present invention resides in the method allowing of prepare the rechargeable electrochemical generator with high stability defined previously.

This method advantageously comprises a step of forming a film of lithium metal and / or a film of an intermetallic alloy mixture rich in lithium by rolling or extrusion. The film thus obtained plays in the generator the role negative electrode. The extrusion technique alone, with the settings necessary to level of the extrudate dimensions leaving the die, also allows provide a movie of suitable electrode.

This method also advantageously comprises a preliminary step to during which metallic lithium and / or intermetallic alloy mixture rich in lithium, initially in solid form such as blocks, bars, granules ...., is extruded before to be subjected to rolling. It is also advantageously implemented in an anhydrous enclosure and / or in the presence of a rare gas such as argon.
This method therefore comprises a step of deposition by rolling of a lithium film metal and / or a film of an intermetallic alloy mixture rich in lithium, of i._ preferably without support but optionally on an electrode support advantageously based on nickel, with formation, during rolling, of a layers passivation on the lithium film.

The extrusion and rolling techniques that can be used are described in short *
US-A-6,517,590.

It is important that the lamination of the lithium film is carried out at a temperature substantially identical to that used for the preliminary extrusion of the lithium.

The invention as claimed therefore resides more precisely in a process for preparing a rechargeable electrochemical generator as defined previously, to apply anode film and a cathode film to a separating film, characterized in that:
the anode film is obtained by extrusion or rolling of lithium or a intermetallic lithium alloy;
the separating film is a film of polymeric material;
the anode film, the separator film and a cathode film are assembled by bonding;
the separating film is impregnated, before or after contact with the anode film and the cathode film, by an electrolyte composition which comprises a crosslinkable polymer and a lithium salt, optionally at minus an additive and optionally a plasticizing solvent;
the electrolyte composition is subjected to crosslinking at a temperature between 20 and 90 C before or after assembly with the anode film and the cathode film;
the rolling, the extrusion and the crosslinking are carried out substantially at the same temperature;

14a the electrolyte composition is crosslinked in situ, after assembly of constituent parts of the generator and after filling its cavities with said electrolyte composition.

Advantageously, the method according to the invention makes it possible to prepare a generator Rechargeable electrochemical stable lithium metal battery and which features:
at least one metal-lithium electrode covered with a film based on lithium, said lithium film being deposited on the electrode by rolling with formation, during rolling, of a layer of passivation on the lithium film;

at least one cathode; and at least one gel polymer electrolyte.

The stability and the remarkable lifetime of this generator come from does it operates substantially without the formation of lithium dendrites on the surface Total of lithium metal electrode present in the generators.

More particularly, this generator which comprises an electrode based on lithium made a metallic lithium film and / or a mixture of intermetallic alloy rich in lithium, operates substantially without dendrite formation at temperatures of operating between - 20 and 60 Celsius.

The lithium film and / or a mixture of intermetallic alloy rich in lithium is advantageously prepared from the extrudate (mass leaving the the extruder) obtained by lithium extrusion or and / or an alloy mixture intermetallic rich in lithium in solid form.

Preferably, the process according to the invention is carried out in an anhydrous medium and / or er-i presence of a rare gas.

Advantageously, the rolling and extrusion temperatures are maintained substantially constant during the extrusion and rolling steps.

According to an advantageous variant, the extrusion of lithium metal and / or a mixed of lithium-rich intermetallic alloy is carried out at a temperature of between 10 50 and 100 Celsius and the rolling is carried out at a temperature varying from 5 to 80 Celsius.

An important feature of the process according to the invention lies in the make that the rolling step and the crosslinking step are carried out substantially at the even Temperature.

In the case where only the extrusion technique is considered for training of the film lithium type, the extrusion outlet temperatures and the crosslinking so that they are substantially the same. As an illustration, the temperatures measured at the exit of the extrusion of a lithium salt may be between 70 and 80 Celsius.

Preferably, the difference in temperature of completion of the steps of rolling and crosslinking is less than or equal to 2 Celsius. More preferentially again, this gap is less than or equal to 1 Celsius.

Advantageously, the gel polymer electrolyte used is obtained by crosslinking of a crosslinkable mixture comprising at least one crosslinkable polymer, at least one solvent plasticizer and at least one lithium salt. The crosslinking of the polymer crosslinkable is advantageously achieved after assembly of the constituent parts of the generator and after the filling of its cavities by the crosslinkable composition.

The crosslinking is advantageously of the IR or thermal type and is preference, by exerting pressure on the outer walls and / or the internal interfaces generator to improve the welding of the internal interfaces. She varied advantageously from 0.1 PSI to 75 PSI.

According to another particularly advantageous variant, the method of preparation of a Rechargeable electrochemical generator according to the invention comprises at least the three preparation steps, namely:
the preparation of a first lithium film from lithium and / or a mixture of lithium-rich intermetallic alloy in the form of solid by extrusion and then by rolling or only by extrusion;
the preparation of a second film applied to an electrode support to form the cathode; and eventually - a third laminating film or by Doctor BladeTM on a support.

It should be noted that during the implementation of the method, the three films are prepared one after another, in an indifferent order, or simultaneously. It is possible to proceed from continuously or discontinuously.

A third object of the present invention is the use of the generator electrochemical rechargeable battery described above or as prepared according to process also described above, as a source of current in vehicles hybrid electric vehicles, in electric vehicles or in power sources emergency, for example UPS type.

As an example of use, it is possible to mention the implantation in air and use to temperatures below 0 Celsius.

DESCRIPTION OF A PREFERENTIAL EMBODIMENT
THE INVENTION

An example of preparation of the polymer matrix by crosslinking the polymer used as an electrolyte in a battery having a lithium-based anode metallic is after given. The technology associated with this new type of batteries is functional low temperature, especially at temperatures ranging from -20 to 600 Celsius.

The process for preparing the gel polymer electrolyte from the composition electrolytic system comprises at least the two steps, namely:
1. the preparation of the electrolytic composition; and 2. the crosslinking of the electrolytic composition.
Among the parameters influencing the preparation of the polymer electrolyte, can mention:
3. the nature of the crosslinking source;
4. the nature of the additives and their effects on the elimination of dendrites; and 5. the choice of the stage of the manufacturing process of the generators during which crosslinking of the crosslinkable polymer is carried out, for example in situ during of final assembly of the battery.

1 - Preparation of the electrolytic composition In the example given, the electrolytic composition is prepared with the aid of minus one crosslinkable polymer and at least one liquid plasticizer capable of increase the ionic conductivity with assistance of at least one salt or at least one salt mixture chosen preferably from:
LiTFSI or LiFSI;
a mixture of LiTFSI and LiFSI; or a mixture of LiBF4 and LiTFSI.

It turned out that the choice of the liquid electrolyte is very important for training, intimate way, from a chemical and physical gel.

Among the recommended liquid electrolytes, mention may be made of those present lem following characteristics:
= good conductivity at low temperature (BT), that is to say at temperatures below 25 Celsius and above 0 Celsius;
= a high boiling point, that is to say preferentially greater than 200 Celsius;
the ability to form a passivation film on lithium metal, stable s high current density;
= a low vapor pressure, that is to say preferably less than 50 mm of Hg at 120 Celsius; and = an electrochemical window of 0 to 5 volts.

Among the plasticizers advantageously used in this context, mention is made of the GAMMA-BL, PC, EC and mixtures thereof with at least one crosslinkable polymer.

2 - Crosslinking of the electrolyte composition This procedure is particularly important for obtaining a electrolyte gel polymer having a very good mechanical strength, which proved ensure a very good interface between lithium and the polymer gel electrolyte, as well between the gel polymer electrolyte and the cathode. For this purpose, different methods of crosslinking have been used successfully.

One of the most important aspects of the method chosen is the choice of crosslinking temperature which should preferably be substantially less than lithium extrusion temperature.

It has also been unexpectedly found that a generator electrochemical particularly stable is obtained when the ambient temperature of crosslinking is substantially the same as the temperature at which rolling is performed. he appears this precaution makes it possible to avoid damage to the passivation film of the lithium that normally occurs and that results in the formation of dendrites, phenomenon corresponding to the formation of layers of Li20 and Li2Co3.

In the case where the lithium metal is just extruded, the polymerization of the mixed containing the plasticizing solvent and the crosslinkable polymer is carried out at temperature to the output of the extruder.

The following four techniques are advantageously used to achieve the cross-linking, ie exposure:
a) to an electron beam;
(b) ultraviolet radiation;
c) infrared radiation generated preferably by an optical source then converted in situ into a thermal source; and d) a non-optical thermal source.
The last two processes (c, d) have proved to be the most advantageous. These processes of crosslinking can be applied to the crosslinkable polymer in the steps of preparation of the electrolytic composition but it is better to apply them in located in the generator after assembly.
Surprisingly, the crosslinking gives a physical and mechanical power at separator (electrolyte). Lithium is also prevented from forming dendrites during the cycling of the battery, in particular on the fragile surface constituted by the joints of grain on the surface of metallic lithium.
3 - Nature of the source of the crosslinking The operational characteristics of the crosslinking sources mentioned in the part above 2 above are preferentially:
a) For electron beam irradiation When the electrolyte separator is formed from a membrane of crosslinkable polymer, the crosslinking dose range is preferentially dc: 2 Mrad at 20 Mrad, preferably about 5 Mrad. The liquid electrolyte is 1 introduced into the polymer membrane and the ionic conductivity is ensured By the liquid polymer-plasticizer mixture. In this case, it is not required to use a separator like PP or PE or their mixture. Indeed, the membranes polymer acts as a separator and electrolyte at the same time.

b) UV crosslinking The implementation of this method is similar to that described in point 3 a) previous, with the difference that we add in addition 10,000 to 50,000 ppm a photo initiator (1% -5% w / polymer) in the polymer to ensure crosslinking, after introduction of the latter into the polymer mixture crosslinkable - plasticizer. The UV irradiation source is in direct contact with the polymer.

c) IR cross-linking This technique can be applied directly or indirectly to the polymer cross-linkable, which is not the case in the techniques mentioned in the parts 3 a) and 3 b). The gel polymer electrolyte is obtained after an intimate mixing of the polymer with the liquid electrolyte and with the initiator. This mixture is then injected into the porous part of the PP or PE separator. Crosslinking is provided by an Infra Red lamp operating at a temperature between 25 and 80 Celsius, preferably for 24 hours or at 80 Celsius for one hour, more preferably still at 25 Celsius for 24 hours. In the In the case of indirect crosslinking, the injection of the mixture (polymer, electrolyte liquid, initiator) is done during the manufacture of the battery. In this case, the electrolyte also occupies the porous space (porosity) of the cathode and the joint of lithium grain. This type of crosslinking is ensured by maintaining the drums under pressure to obtain a very good interface between the lithiutn, the électrolyte---- and the electrolyte / cathode.

d) Thermal cross-linking This crosslinking process is equivalent to that of Part 3 (c) at difference that the heat source is not optical.

4. Nature of the additives and their effect on the elimination of dendrites The combined use of a cross-linking source and additives of the type Ti02, A1203 or SiO2 improves mechanical properties and ionic conductivity of the electrolyte / lithium interface.

IR or thermal crosslinking in the presence of TiO 2, Al 2 O 3 or SiO 2 is used in the process of manufacturing the electrolyte at low temperature. The realized experiences have surprisingly demonstrated the important role of these additives, likely to increase the mechanical strength of the gel electrolyte, by welding the interfaces lithium gel electrolyte and cathode / gel electrolyte. The added benefit found live in the fact that this ensures good battery safety, especially when a boost.

Moreover other parameters favorably influencing the conductivity of electrolyte and the interfacial resistance of the lithium battery have been put in evidence. So, among the parameters that allow to obtain at the same time a very good conductivity of the gel electrolyte and a low interfacial resistance, it can be pointed out that nature of salt advantageously of LiFSi or LiTFSi type and its concentration in the electrolyte polymer, as well as the nature of the plasticizer preferably present in 0.5 to 2.5 Moles in the plasticizer / crosslinkable polymer mixture.

It should also be noted that the ionic conductivity of the gel depends on the nature of salt and of its concentration, the choice of the liquid electrolyte and the ratio polymer / electrolyte liquid.

The concentration of the salt is thus advantageously chosen preferably between 1 and 2 moles and the salt is preferably dissolved in a solvent of the group y-BL, y-BL + EC
and y-BL + PC. The crosslinkable polymer / plasticizer percentage is when it is advantageously 10/90% by weight.

Low initial interfacial resistance is obtained with y-BL and a strong resistance interfacial is obtained with y-BL + PC, in addition the following relation is checked for interfacial resistances y-BL <y-BL + EC <y-BL + PC.

The interfacial resistance of this new type of electrochemical generators rechargeable batteries remains low during long term storage of the battery at lithium, at the ambient temperature. This interface resistance is obtained with the sequence following decreasing y -BL <y -BL + PC <y-BL + EC, (y -BL) representing the weaker value and (y-BL + EC) representing the highest value.

Crosslinking process and manufacture of the battery.

Figures 1 and 2 show the detail of the method of manufacturing a battery lithium by in situ polymerization of the polymer electrolyte by infrared lamp (optics) or thermal.
As shown in Figure 2, three films are prepared simultaneously by rolling. The metallic lithium film is prepared from a lithium extrudate solid that is laminated, optionally on an electrode support film. The separator film is prepared from an extrudate of polypropylene granules. The film of the cathode is laminated, optionally on a support. At the exit of the rollers (1), (2) and (3) rolling, the three films are assembled under the effect of a pressure exerted by the rollers (4) between the different films. We adjust the distance between rolls for him remain micro-spaces between the different. These micro-spaces are filled over there crosslinkable electrolytic composition. The multilayer film is cut in the length desired using a knife not shown in Figure 2 but positioned at proximitc of the roll (5). The multilayer film sections thus obtained are impregnated successively in the baths (6) and (6 ') filled with the polymer mixture crosslinkable / plasticizing solvent / lithium salt. Soaked sections as well prepared his -t welded at one end for example using ulta-sounds. The generators so assembled are subjected to an infrared source in the heating zone (8).
Irradiation causes the formation of the polymer gel electrolyte to inside cavities of the generator but also inside the porosities present in the electrodes and in the separator film. The temperature measured in the exposure area of the generator infrared light by the temperature sensor (12) is adjusted with the measured one by the temperature sensor (11) indicating the rolling temperature of the film of lithium. The adjustment is made using the temperature control (13).
Laréticulation is stopped when the polymer gel electrolyte has reached the consistency of a freeze which corresponds to a value of the degree of crosslinking of the crosslinkable polymer in the crosslinkable polymer mixture / plasticizing solvent / lithium salt between 5 and 40%.
Unlike a traditional solvent, the plasticizing solvent does not evaporate substantially not during the crosslinking step and the solvent plasticizer remains trapped in the gel electrolyte polymer structure to contribute to its conductivity and its plasticity.

The following examples are given for illustrative purposes only, and would not know be interpreted as constituting any limitation of the object claims.

EXAMPLE 1 - Battery with lithium metal and gel -Gel (E-BEAM) The complete process of film preparation and generator assembly corresponding below used is carried out continuously in a glove box ave c temperature and under argon, according to the diagram shown in the Figure 2 _ The manufacture of extruded lithium metal extrudate is carried out at 25 Celsius in the glove box made anhydrous.

The preparation of the lithium metal film is carried out by extrusion of a bar of metallic lithium and the extrudate obtained from a thickness of about 250 micrometers is subjected to rolling to result in a continuous film of a thickness about 34 micrometers.

The manufacture of the cathode is made from LiFePO4 and black of carbon mixed with the fluorinated polyvinylidene binder (PVDF) marketed under the Mark of Kruha trade: KF-1700TM, in the mass ratio 87: 3: 10 in the solvent n-methyl pyrolidone.

This mixture is applied to an aluminum collector by the Doctor method BladeTM.
The electrode thus obtained is dried under vacuum at 120 Celsius for 24 hours.
hours.
The polymer electrolyte of the four-branched polymer type marketed under the trademark ERM-1 ELEXCELTM by the company DKS lot 8K1201 is also prepared by Doctor BladeTM then crosslinked using Electron-beam. The cathode and the polymer separator are first soaked in the plasticizer-based mixture 1.5M
LiBF4 in EC / GBL (1: 3).

Lithium metal is used as anode mounted facing the cathode and separated by the movie of polymer.

Care was taken to carry out the crosslinking of the crosslinkable polymer mixture -plasticizer -lithium salt at the same temperature as that used for the rolling of the extrudate of metallic lithium.

Thus an electrochemical cell with a surface area of 4 cm 2 is obtained.

The battery is cycled between 2.5 and 4.0 volts, at a rate of C / 3. Figure 3 show it battery cycling result which maintains a good stability of the interface of lithium with the polymer after 60 cycles.
EXAMPLE 2 Gel Configuration: Battery with Lithium Metal Compared to a Li-ion battery - Gel (thermal) A) lithium metal battery The cathode is prepared in the same way as in Example 1. In particular the extrusion temperatures of lithium metal, extrudate rolling corresponding and crosslinking the polymer / plasticizer / lithium salt mixture are adjusted to a worth 25 Celsius.
The anode is prepared from a spherical natural graphite mixed with the binder fluorinated polyvinylidene (PVDF) (Kruha: KF-1700 TM) and n-methyl pyrolidone in one 90:10 mass ratio. This mixture is applied to a copper collector the Doctor BladeTM method. The graphite electrode thus obtained is dried vacuum to 120 Celsius for 24 hours.

The polymer electrolyte is prepared from ERM-1 ELEXCELTM (4 branches) of DKS lot 8K1201 with 1.5 Moles of LiBF4 in EC / GBL (1: 3) of Tomiyama, in which is added 1000 ppm of the thermonitiator Perkadox 16 TM of the Akzo Nobel company.

The manufacture of the anode is carried out using a lithium strip 40 metal m thick rolled on a metal copper strip. The catches contacts negative are performed by ultrasound (UL TRAWELD, AmTech Model 2000BTM).

The technological assembly of the battery is made by stacking the films anode Celgard (D and cathode, following the anode // Celgard // cathode sequence.

This configuration is put in a plastic metal bag and sealed.
The electrolyte polymer is injected into the cell, then a second seal follows. The battery is put in the oven at 25 Celsius for 48 hours for adequate crosslinking, thus the gel is formed in situ and the battery A is obtained.

B) Li-ion battery This type of battery does not usually give rise to the formation of dendrites.

A second battery (B) is mounted, in the same way, also with a control of temperature, replacing the lithium anode with an anode based on the graphite. The anode is prepared by mixing the spherical graphite with the polyvinylidene binder fluorinated (PVDF) (KruhaTM: KF-1700) and n-methyl pyrolidone, in a mass ratio 90:10.
This mixture is applied on a copper collector by the method of Doctor BladeTM.
The graphite electrode thus obtained is dried under vacuum at 120 Celsius during 24 hours Electrochemical validation is based on the Ragone test which consists of achieve a series of cycles at different discharge regimes. Figure 4 shows a comparison batteries A and B.

The results obtained clearly show that the rechargeable capacity impairment is no longer high for the configuration with lithium metal (battery A) that with the configuration lithium ion. This is associated with a better stability of the gel interface with lithium metal.

EXAMPLE 3 - highlighting the importance of a temperature control rolling at 25 Celsius and crosslinking at 80 Celsius The process implemented is that illustrated in FIG.
the extrudate Lithium metal is made at 25 Celsius.

The gel polymer electrolyte is prepared from a mixture of 10% of the polymer with 4 branches ERM-1 ELECELTM marketed by DKS and 90% of 1.5T ~ / I
LiFSI in EC + GBL plasticizer mixture (1: 3) with addition of 2,000 ppm of the agent crosslinking used in Example 1.

The cathode consists of a film of LiFePO4 and the separator is constituted of a film of polyethylene.

Crosslinking of the crosslinkable polymer mixture is carried out at a temperature different imposed during the rolling stage, ie 80 Celsius during 3 hours.
The cycling conditions are 2.5 to 4 volts, the discharge in C / 3 and the load in C / 1.

The cycling curve shown in Figure 5 clearly shows a fall fast of the capacity according to the cyclability. In addition, efficiency has increased (>
at 100%), this which demonstrates dendritic activity.

Although the present invention has been described using implementations specific, he It is understood that many variations and modifications can be added to say put the purpose of this application is to cover such changes, uses or adaptations of the present invention, in general, the principles of the invention and including any variation of this description that will become known or Convention in the field of activity in which this invention, and which can be applied to the essential elements mentioned above, in agreement with the scope of the following claims.

Claims (31)

1. Rechargeable Lithium Metal Electrochemical Generator Featuring at least one electrode made of a metallic lithium film or a alloy intermetallic rich in lithium and at least one cathode separated by a separator, each in the form of a film, said separator being impregnated with a electrolyte polymer, said generator being characterized in that the face of the electrode in look at the electrolyte carries a passivation film and in that electrolyte polymer gel occupies the space between the electrodes and the separator, as well as the porosities of the materials forming the electrodes and the separator. 2. Generator according to the coating 1, characterized in that the cathode is consisting of a material selected from LiFePO4, LiCoO2, LiNiO2, Li4Ti4O12 and their mixtures. 3. Generator according to claim 1 or 2, characterized in that the alloy The internietallic electrode is a Li-Al, Li-steel, Li-Sn or Li-Li alloy.
Pb. 4. Generator according to any one of claims 1 to 3, characterized in what the separator is constituted by a polyethylene, a polypropylene, a polyether or a polyethylene / polypropylene blend. Generator according to one of Claims 1 to 4, characterized in it also includes at least one additive of organic nature and / or inorganic. 6. Generator according to claim 5, characterized in that the additive is a ceramic or a glass. 7. Generator according to claim 5, characterized in that the additive is selected among titanium oxides, aluminum oxycides and mixtures thereof, and what the content of the additive is less than 10% by weight. 8. Generator according to any one of claims 1 to 7, characterized in that that the gel polymer electrolyte contains a lithium salt selected from LiBF4, LiPFE, LiTFSI, LiBETI, LiFSI and mixtures thereof. 9. Generator according to claim 1, characterized in that the cathode is constituted by a material chosen from LiFePO4, LiCoO2, LiNiO2, Li4Ti5O12, and mixtures thereof;

the anode is made of metallic lithium or an alloy intermetallic selected from Li-Al, Li-steel, Li-Sn or Li alloy alloys Pb;
the polymer gel electrolyte contains a lithium salt and a chosen additive among titanium oxides, aluminum oxides and mixtures thereof, and in that the content of the additive is less than 10% by weight. 10. Process for preparing a rechargeable electrochemical generator according to any one of claims 1 to 9, applying a film anode and a cathode film on a separator film, characterized in that:
the anode film is obtained by extrusion or rolling of lithium or a intermetallic lithium alloy;
the separating film is a film of polymeric material;
the anode film, the separator film and a cathode film are assembled by colaminating;
the separating film is impregnated before or after contacting the film anode and the cathode film, by an electrolyte composition which comprises a crosslinkable polymer and a lithium salt, optionally at minus an additive and optionally a plasticizing solvent;
the electrolyte composition is cross-linked at a temperature between 20 and 90 ° C before or after assembly with the film anode and the cathode film;

the rolling, the extrusion and the crosslinking are carried out substantially at the same temperature;
the electrolyte composition is crosslinked in situ, after assembly of constituent parts of the generator and after filling its cavities with said electrolyte composition. 11. Process according to claim 10, characterized in that the polymer crosslinkable is a four-branched polymer. Method according to claim 10 or 11, characterized in that the content in crosslinkable polymer in the electrolyte composition is from 1 to 95% by weight weight of crosslinkable mixture. Method according to one of claims 10 to 12, characterized that the lithium salt of the electrolyte composition is selected from LiBF4, LiPF6, LiTFSI, LiBETI, LiFSI and mixtures thereof. 14. Process according to claim 13, characterized in that the salt content of lithium represents 0.5 to 2.5 molar relative to the amount of the solvent plasticizer present in the crosslinkable mixture, 15. Process according to any one of claims 10 to 14, characterized the plasticizing solvent is selected from gamma-buturolactone, tretrasulfonoamine, propylene carbonate, ethylene carbonate and their mixtures. 16. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out in the presence of a peroxycarbonate as as crosslinking agent. 17. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out in the presence of benzoyl peroxide. 18. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out for a duration of between 15 minutes and 72 hours. 19. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out using a beam irradiation electron ultraviolet radiation, infrared or thermal radiation, or a combination of at least two of these techniques. 20. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out using an electron beam, without addition crosslinking agent. 21. Process according to any one of claims 10 to 20, characterized in that the anode film is prepared in an anhydrous medium and / or in the presence of a gas rare. 22. Process according to claim 21, characterized in that the temperatures rolling and extrusion are kept substantially constant during the extrusion and rolling steps. 23. Process according to any one of claims 10 to 22, characterized that the anode film is obtained by extrusion of lithium metal and / or a of lithium-rich intermetallic alloy at a temperature of between 50 and and 100 ° C and the rolling is carried out at a temperature of 5 to 80 ° C. 24. Process according to any one of claims 10 to 23, characterized in what the difference between the temperature at the exit of the extrusion and the temperature of crosslinking is less than or equal to 2 ° C. 25. Process according to any one of claims 10 to 15, characterized that the crosslinking is carried out by infrared irradiation or by thermal, and exerting pressure on the outer walls and / or on the interfaces internal generator to improve the welding of the internal interfaces. 26. Process according to claim 25, characterized in that the pressure exercised ranges from 0.1 PSI to 75 PSI. 27. Process according to claim 10, characterized in that a lithium film is prepared from lithium and / or an alloy intermetallic rich lithium in solid form by extrusion followed rolling or extrusion only;
a second film is prepared and applied on an electrode support for to form a cathode; and eventually a separating film is prepared by rolling or by Doctor Blade optionally on a support. 28. Process according to claim 27, characterized in that the three films mentioned are prepared one after the other, in any order, or simultaneously. 29. The method of claim 10, carried out continuously. 30. Use of a generator according to any one of claims 1 to or as obtained by a process according to any one of claims 10 to as a power source in hybrid electric vehicles, in electric vehicles or in Uninterruptable Power Supply (UPS). 31. Use of a generator according to any one of claims 1 to or as obtained by a process according to any one of claims 10 to outdoors at temperatures below 0 ° C.