Electrochemical cell manufacturing process

Abstract

Method for manufacturing an electrochemical cell. The invention relates to a method for manufacturing an electrochemical cell comprising at least the following steps: A) impregnating a porosity of an electrode material comprising a plurality of particles (12) of a material comprising carbon, silicon, and oxygen of general formula SiOxCy, x and y being strictly positive, with fluorine (13) being grafted onto said particles, the plurality of particles forming a three-dimensional porous network, the active material further comprising carbon fibers (11) present in the porosity of the three-dimensional porous network and supporting the particles; and B) positioning the electrode material thus impregnated in an electrochemical cell, in contact with an electrolyte, the impregnation composition of step A) comprising the same charge carrier as the electrolyte of step B). Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing an electrochemical cell Technical field

[0001] The present disclosure relates to the field of electrochemical cells, and more particularly to the methods of manufacturing such cells. Prior art

[0002] Electrochemical cells and in particular batteries present technological challenges in energy supply.

[0003] For example, energy storage represents a major technical obstacle to the large-scale deployment of renewable energies and this is why development in this area remains very active.

[0004] Lithium-ion batteries have enabled improved performance in terms of energy density and lifespan compared to other batteries, notably Ni-MH and Ni-Cd. Nevertheless, there is still room for improvement for this technology, particularly in terms of energy density, but also in terms of lifespan, safety and cost.

[0005] If it is the positive electrodes which are limiting with regard to energy density, whether mass or volume, the strong research in this area requires the parallel development of new materials for the negative electrodes.

[0006] Currently, graphite is mainly used in negative electrodes. This material, which combines excellent reversibility, cyclability, conductivity and good availability of raw materials, has long been seen as the ideal electrode material.

[0007] However, graphite is a so-called insertion electrode material, the lithium ion will insert and disinsert between the graphite sheets. This property gives it good cycling stability, but may have insufficient energy density with respect to new emerging electrical systems, particularly in the field of aeronautics.

[0008] In addition, its oxidation-reduction potential close to lithium can, at high current densities, cause the formation of lithium dendrites which can cause internal short circuits.

[0009] Electrode materials of the alloy type, for example based on silicon, antimony, tin, or bismuth are good candidates for replacing graphite due to their high theoretical mass capacities (994 mAh.g 1 for tin, and 4200 mAh.g 1 for silicon compared to 372 mAh.g 1 for graphite).

[0010] However, the use of these materials is limited by numerous technological barriers.

[0011] In particular, they exhibit a significant change in volume during charge / discharge cycles, which generates internal stresses that can lead to delamination of the electrode, loss of percolation and premature death of the accumulator.

[0012] In addition, the metal particles will tend to coalesce into inactive clusters as the cycles progress, resulting in a reduction in capacity.

[0013] In addition, an interface is observed between the electrode and the electrolyte, called "SEI" for the English acronym "solid electrolyte interface". This interface, consisting mainly of oxides, fluorides and carbonates, will consume part of the lithium ions to form during the first cycle.

[0014] If it is stable, the SEI will act as a diffusion barrier for the electrolyte solvents, preventing their destructive intercalation into the material and will promote the exclusive diffusion of Li+ ions, thereby improving the battery life.

[0015] In electrodes based on alloy materials, the strong volume changes will lead to instability of the interface between the electrode and the electrolyte and therefore a consumption of additional electrons not only in the first cycle, but also in the following cycles, consequently reducing the life of the accumulator.

[0016] There therefore remains a need for a method for preparing an electrode material which addresses these issues, i.e. which has a mass capacity greater than that of graphite and better cycling performance than that of silicon. Description of the invention

[0017] The invention aims precisely to meet this need.

[0018] To this end, it proposes a method for manufacturing an electrochemical cell comprising at least the following steps: A) impregnation with an impregnation composition of a porosity of an electrode material comprising a plurality of particles of a material comprising carbon, silicon and oxygen of general formula SiOxCy, x and y being strictly positive, fluorine being grafted onto said particles, the plurality of particles forming a porous three-dimensional network, the active material further comprising carbon fibers present in the porosity of the porous three-dimensional network supporting the particles; and B) the positioning of the electrode material thus impregnated in an electrochemical cell, in contact with an electrolyte, the impregnation composition of step A) comprising the same charge carrier as the electrolyte of step B).

[0019] The inventors have in fact noted that such a method presents numerous advantages compared to the manufacturing methods of the prior art.

[0020] The use of silicon as an active material makes it possible to achieve performances far superior to those achieved with graphite electrodes of the prior art.

[0021] Furthermore, each of the materials constituting the electrode material provides particular characteristics that are important for obtaining an active electrode material whose properties are superior to the materials of the prior art.

[0022] The carbon in the particles helps prevent the coalescence of silicon which, in the absence of carbon, tends to form clusters that consume part of the active electrode material. In addition, the carbon helps provide a certain conductivity to the material.

[0023] The carbon fibers present in the porosity of the network formed by the particles ensure better mechanical resistance to the electrode material which suffers less from expansion / contraction cycles during insertion / deinsertion of the active species.

[0024] The presence of fluorine ensures better stability for the SEI and therefore allows the electrochemical performance to be maintained over a large number of cycles. Furthermore, the presence of fluorine provides other advantages: the improvement of the electrical conductivity of SiOx and the improvement of the dispersion of the particles, thus limiting the coalescence phenomenon. Finally, fluorine makes it possible to clean the surface of the particles of the oxygenated groups that may be present there.

[0025] The structure of the active material and in particular its constitution as particles supported by the carbon fibers in the porous network ensures that the active material is directly usable as an electrode material. That is to say, it is not necessary to add a binder, a current collector and / or an additional electronically conductive agent, as is the case with the electrode materials of the prior art. Furthermore, it is not necessary to coat the electrode material on a rigid material, since the latter is sufficiently rigid to be introduced directly into a battery as an electrode. This results in a simplified method of preparing an electrode, and a further improved power and energy density, since it is then not necessary to add electrochemically inactive material such as the polymer binder, the conductive agent and the current collector.

[0026] Furthermore, the inventors found that impregnating the electrode material with an impregnation composition before its positioning in the electrochemical cell in contact with an electrolyte improved the properties of the electrode as well formed, by improving the diffusion depth of charge-carrying ions (Li for example) in the electrode, making it possible to obtain a higher mass capacity.

[0027] Also, the fact that the charge-carrying ion is the same in the impregnation solution and in the electrolyte ensures that there is perfect compatibility in the cell once it is formed.

[0028] In one embodiment, the electrolyte may be a liquid or solid electrolyte.

[0029] In one embodiment, the charge carrier of the electrolyte and the com impregnation position is chosen from lithium or sodium.

[0030] For example, the electrolyte may be a liquid electrolyte, for example a solvent comprising a salt comprising lithium ions, for example lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or LiPF6.

[0031] For example, the solvent may be a ternary mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate.

[0032] These solvents have shown the best properties for the intended application.

[0033] For example, the ternary mixture may comprise a volume portion of ethylene carbonate for one volume portion of ethylene carbonate of propylene carbonate and three volume portions of dimethyl carbonate.

[0034] In one embodiment, the electrolyte may be a solid electrolyte.

[0035] For example, the solid electrolyte may be a membrane comprising glass fibers impregnated with a composition comprising LiPF6, for example concentrated at one mole per liter in a ternary mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate.

[0036] For example, the ternary mixture may comprise one volume portion of ethylene carbonate to one volume portion of ethylene carbonate to propylene carbonate and three volume portions of dimethyl carbonate.

[0037] For example, the solid electrolyte may be an ionically conductive polymer membrane.

[0038] The use of a solid electrolyte makes it possible to avoid the use of flammable organic solvents and thus improves the safety of electrochemical cells. It also makes it possible to reduce parasitic reactions and thus increase the cyclability of the cells.

[0039] Also, it allows an improvement in performance density, because all species of the solid electrolyte are effective, where the solvent of a liquid electrolyte represents a large electrochemically inactive volume.

[0040] In one embodiment, the impregnation composition may comprise identical chemical species but in different concentrations.

[0041] In one embodiment, the impregnation composition may be the same as the composition used in the electrolyte.

[0042] For example, if the solid electrolyte is composed of a polymeric membrane impregnated with a composition, the impregnation composition may be identical to this composition impregnating the polymeric membrane of the solid electrolyte.

[0043] For example, if the electrolyte is liquid, the impregnation composition may have the same composition as the electrolyte.

[0044] As described, the electrode material has the general formula SiOxCy.

[0045] In one embodiment, x may be less than or equal to 4, or even less than or equal to 3, or better still less than or equal to 2.5.

[0046] The higher x is, the more Li2O is formed, which limits the volume expansion of the electrode. However, it is preferable that x is not too large because the Li2O species is not electrochemically active, and increasing x therefore decreases the active mass.

[0047] In one embodiment, y may be less than or equal to 40, or even less than or equal to 20.

[0048] The larger y is, the better the conductivity of the matrix.

[0049] In one embodiment, x is between 1.5 and 2.5 and y is between 15 and 25.

[0050] In one embodiment, the rate of impregnation of the electrode material by the impregnation composition can be measured as a percentage of the porosity of the electrode material.

[0051] Such a measurement can be carried out by knowing the maximum possible mass gain for a given volume, or equivalently a mass, of the electrode material. This maximum quantity of infiltration liquid corresponds to a 100% filling, and the mass gain is then linear with the proportion of porosity occupied by the impregnation composition.

[0052] In one embodiment, at least 20% of the porosity of the electrode material is impregnated with the impregnation composition during step A) of the method of the invention.

[0053] Preferably, between 20% and 40% of the porosity of the electrode material may be impregnated with the impregnation composition during step A).

[0054] This embodiment offers an optimum between the improvement provided by the impregnation of the electrode material and the cost of such impregnation.

[0055] It is possible to impregnate up to 100% of the porosity of the electrode material with the impregnation composition and this improves the behavior of the electrode material, but not linearly with the impregnation rate.

[0056] In one embodiment, the mass content of carbon fibers is less than or equal to 10%, for example between 1.5% and 3.5% and preferably equal to 2.5% relative to the total mass of the precursors leading to the non-SiOxCy material. impregnated.

[0057] This quantity of carbon fibers presents an optimum with on the one hand a sufficient quantity of fibers so that the electrical conductivity is improved, and on the other hand a sufficiently small quantity of fibers to ensure that the electrode material comprises a maximum of the SiOxCy material responsible for the electrochemical properties of the electrode material.

[0058] In one embodiment, the atomic ratio of fluorine to silicon in the particle material is less than or equal to 10%.

[0059] This atomic ratio reflects the fact that fluorination has taken place preferentially on the surface of the particles making up the C-SiOxCy material, which is the thermodynamically favored location. Thus, fluorine is substantially not present on the carbon fibers and this does not harm the conductivity of the electrode material.

[0060] In one embodiment, the carbon fibers may be hollow or solid, and may have a length less than or equal to 1000 pm, for example between 100 pm and 500 pm.

[0061] In one embodiment, the particles of the SiOxCy material have a median size of between 100 nm and 600 nm.

[0062] The particle size is understood as the largest dimension of the particles and the median is the value also called D50 which characterizes the statistical size at half of the population.

[0063] According to another of its aspects, the electrode material is obtained before step A) by a method comprising at least the following steps: (a) obtaining a mixture comprising a precursor sol of the particulate material, as well as fibers of a carbon or carbon precursor; b) gelling the sol to obtain a gel in which the carbon or carbon precursor fibers are present; c) drying the gel; (d) pyrolyzing the dried gel to obtain a pyrolyzed material; and e) fluorination of the obtained pyrolyzed material to obtain the active electrode material.

[0064] The method makes it possible to simply obtain an active electrode material having the advantages described above. In particular, the material obtained can be used directly as an electrode material after the impregnation step B) described, and does not require additional machining before impregnation, unlike the electrode materials of the prior art.

[0065] For example, it may be noted that the material no longer requires the steps of powdering, dissolving in a solvent to obtain an ink, the possible addition of binder and a conductive material, and coating on a current collector that can require the electrode materials of the prior art.

[0066] The use of a precursor sol of the particle material makes it possible to provide the constituent elements of the material and to mix them intimately, so as to obtain a material of general formula SiOxCy, in the form of a porous three-dimensional network of particles.

[0067] For example, the precursor sol of the particulate material may comprise a plurality of constituents whose mixture allows the desired proportion of each of the elements to be achieved to achieve the desired composition for the SiOxCy material, with x and y strictly positive.

[0068] In one embodiment, the precursor sol of the material may comprise a phenol or polyphenol, an aldehyde and one or more silicon oxide precursors comprising or not one or more amine groups.

[0069] In one embodiment, the precursor sol of the material may comprise a mixture of resorcinol, formaldehyde, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS).

[0070] In embodiments where none of the silicon oxide precursors contain an amine group, a catalyst may be added.

[0071] In an identical or different embodiment, the precursor sol of the material comprises a solvent such as acetone. This solvent advantageously makes it possible to dissolve all of the constituents of the sol.

[0072] Other solvents could also be considered, for example, the solvent may comprise alcohols, for example ethanol, water, or a mixture of these solvents.

[0073] As described, the mixture also comprises fibers of a carbon or carbon precursor. These fibers present from the beginning of the manufacturing process will form the carbon fibers supporting the particles and present in the porosity of the active electrode material.

[0074] It will be noted that it is possible to use a carbon precursor, which will form, after the drying and pyrolysis steps, the carbon fibers of the active electrode material.

[0075] For example, the fibers of a carbon precursor may be cellulose fibers, which may be hollow.

[0076] The sol gelling step makes it possible to obtain a gel from the mixture comprising the precursor sol of the particle material.

[0077] The mixture also comprises the fibers of a carbon or carbon fiber precursor, entangled with the gel, precursor of the SiOxCy material, and the gelation makes it possible to maintain the intimate mixture between the material of the gelled particles and the fibers.

[0078] The method further comprises a step of drying the gel.

[0079] This drying can be obtained according to methods known as such. In particular, the drying can be carried out in air under conditions close to normal temperature and pressure conditions to obtain a xerogel, by supercritical drying to obtain an aerogel, by lyophilization to obtain a cryogel.

[0080] In one embodiment, the gel can be dried in air, optionally heated to, for example, 60°C, which simplifies and makes the method of the invention less expensive compared to prior art methods that use supercritical drying or freeze-drying.

[0081] Pyrolysis under neutral gas, for example under a nitrogen or argon atmosphere, of the dried gel then makes it possible to obtain a pyrolyzed material.

[0082] For example, the pyrolysis of the dried gel can be carried out at a pyrolysis temperature greater than or equal to 800°C, for example preferably between 800 and 1150°C.

[0083] In one embodiment, the duration of the pyrolysis cycle may be between 8 hours and 10 hours.

[0084] In one embodiment, the pyrolysis temperature may be greater than or equal to 800°C. This temperature may be imposed for a duration greater than or equal to 20 minutes, for example between 20 and 60 minutes, for example 30 minutes.

[0085] For example, the pyrolysis may comprise a rise in temperature according to a temperature ramp of between 3°C / min and 10°C / min, for example 5°C / min, a temperature maintenance for a period of between 20 minutes and one hour, for example 30 minutes and thermal cooling by exposure to air, for example for a period of between 3.5 and 4.5 hours.

[0086] Pyrolysis of the gel already comprising the carbon fibers or a carbon precursor makes it possible to directly obtain the desired structure with the fibers present in the porosity of the three-dimensional network of the particles and supporting the particles. The porosity comes from the pyrolysis of the precursors of the C-SiOxCy material, the space between the particles and the arrangement of the fibers surrounded by these particles.

[0087] Fluorination of the pyrolyzed material then makes it possible to obtain an active material as described above.

[0088] The fluorination of materials can be carried out using a gaseous fluorinating agent, for example pure molecular fluorine or diluted with nitrogen, argon, gaseous HF, liquid, for example aqueous HF or a solution containing a soluble fluorinated solid such as NH4F, or solid proceeding by thermal decomposition of a fluorine precursor, for example XeF2, TbF4, CeF4, CoF3, MoF3, AgF, CuF2, CuF, VF3 or CrF3 and generating atomic or radical fluorine.

[0089] In one embodiment, the fluorination is carried out by free radical fluorination of the pyrolyzed material, produced for example in an inert atmosphere.

[0090] In one embodiment, the radical fluorine is obtained by thermal decomposition of a radical fluorine precursor, for example by thermal decomposition of XeF2.

[0091] This fluorination method allows the preferential fluorination of the particles of the active electrode material SiOxCy, on the surface and over a thickness of approximately 10 nm to stabilize the interface which will then be in contact with the electrolyte in the accumulator. Indeed, it is desirable to avoid the fluorination of carbon fibers, because excessive fluorination of the latter reduces their conductivity.

[0092] In one embodiment, the electrochemical cell is an accumulator or a battery.

[0093] In one embodiment, the electrode material forms the anode of the electrochemical cell, for example of an accumulator or a battery. Brief description of the drawings

[0094] [Fig.l] [Fig.l] is a schematic representation of the architecture of the material in one embodiment.

[0095] [Fig.2] [Fig.2] schematically represents a battery described as an example. Description of the embodiments

[0096] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0097] [Fig.l] shows the structure of the electrode active material in one embodiment.

[0098] The material comprises carbon fibers 11. The material further comprises a plurality of particles 12 of a material of general formula SiOxCy onto which fluorine 13 is grafted.

[0099] As shown in [Fig.l], the particles 12 are linked together, and they are so by covalent bonds.

[0100] The particles 12 are also bonded to the carbon fibers 11, and they are bonded by non-covalent bonds.

[0101] The carbon fibers 11 ensure that the electrode is self-supported, that is to say that the carbon fibers provide sufficient rigidity to the active material so that it can serve alone as an electrode, and without needing to be placed on a third-party material forming a support.

[0102] As described above, the material can be obtained by means of a sol-gel process where the sol contains all the precursors of the particles as well as the fibers of the carbon or carbon precursor followed by a drying and pyrolysis step, allowing forming the network of particles 12 with fibers 11 present in the porosity of the network and supporting the particles.

[0103] In one embodiment, the fibers participate in creating the overall porosity of the electrode material.

[0104] The material is then fluorinated to achieve the desired active electrode material.

[0105] It is shown in [Fig.l] that fluorine 13 is grafted to the surface of the particles 12. Fluorine 13 allows the stabilization of the SEI and thus increases the performance of such an electrode over time.

[0106] For example, the fluorination of materials can be carried out using a gaseous fluorinating agent, for example pure molecular fluorine or diluted with a neutral gas such as nitrogen, or argon, gaseous HF, liquid, for example aqueous HF or a solution containing a soluble fluorinated solid such as NH4F, or solid by proceeding by thermal decomposition like the fluorination process of XeF2 or one or more of the compounds chosen from: TbF4, CeF4, CoF3, MoF3, AgF, Ag2F, CuF2, CuF, VF3, FeF3, CrF3 and generating atomic or radical fluorine by decomposition.

[0107] In one embodiment, the fluorination takes place by bringing the composite material into contact with atomic fluorine or gaseous radical fluorine, obtained by thermal decomposition of a precursor. The duration of the fluorination can be between 10 minutes and 24 hours. The temperature imposed during the fluorination can be between 20°C and 600°C.

[0108] In a preferred embodiment, the fluorination is carried out by exposure to radical fluorine obtained by decomposition of XeF2 under an inert atmosphere. The radical fluorine produced at a temperature of 120°C has optimal diffusion kinetics allowing the grafting of fluorine to the surface in a homogeneous manner without saturation of the surface and fluorination going at most up to 10 nm below the surface of the particles. Examples

[0109] Example 1: Preparation of an active electrode material

[0110] A solution is prepared by mixing resorcinol, formaldehyde, tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES) in acetone.

[0111] Hollow cellulose fibers are added to this solution, in a mass content of 2.5% relative to the total mass of the solution.

[0112] The solution is then gelled by heating to 60°C in a closed bottle.

[0113] The gel thus obtained is then dried in an oven for 16 hours at 60°C.

[0114] The gel is pyrolyzed at 1000°C to obtain the three-dimensional network of particles, around or supported by the carbon fibers present in the porosity of the network.

[0115] In order to obtain the active electrode material, fluorine is then grafted onto the pyrolyzed material.

[0116] In a glove box under an argon atmosphere, the pyrolyzed gel is brought into contact at 120°C with XeF2.

[0117] The thermal decomposition of XeF2 produces radical fluorine which will preferentially deposit on the SiO2C[8 particles to form the active electrode material.

[0118] Example 2: Comparison of specific capacities

[0119] To compare the specific capacities, different electrodes were prepared.

[0120] A first electrode is formed from a first active material based on graphite carbon.

[0121] For the preparation of the first electrode, graphite carbon powder is mixed with acetylene black and polyvinylidene fluoride (PVDF) so that the mass contents of the compounds are 80%, 10% and 10% respectively.

[0122] The mixture is then dissolved in N-methyl-2-pyrrolidone (NMP) to form a suspension.

[0123] To form an electrode, the solution is then coated onto a copper foil acting as a current collector, and dried in a vacuum oven at 120°C for one hour.

[0124] A second electrode is prepared in an identical manner to the first, but with a powder of a material of formula C-SiO2Ci8 as the active material and not graphite carbon. The mass proportions are identical to those of the first electrode, and the preparation steps are also the same as for the first electrode.

[0125] A third electrode is prepared with an active material prepared in an identical manner to that described in Example 1, except that it is not powdered but used in the form of a block cut to the size of the electrode without acetylene black and without a polymer binder. Such a material can be used alone as an electrode active material, without having to be coated on a current collector.

[0126] Finally, a fourth electrode is prepared with a fluorinated active material implemented as obtained in the previous example.

[0127] Electrochemical cells are manufactured to evaluate the electrochemical performances of different electrodes. Unlike the final use of the active material, for these test phases it will constitute the positive electrode and lithium will be the negative electrode material.

[0128] The batteries are manufactured in glove boxes under an argon atmosphere in order to avoid any nitriding or oxidation of the lithium surface by air or water vapor.

[0129] These cells are in the form of button batteries, and are shown schematically in [Fig.2]. They comprise an upper cover 121, a spring 122, spacers 123, a lithium disc 124, separators 125, an electrode comprising the active material 126 and a lower cover 127.

[0130] The counter-electrode (negative electrode) of the cell is the metallic lithium disc. The separator in contact with the electrode 125a is a polypropylene polymer film (Celgard). This separator is advantageous because it has a very smooth surface and does not risk contaminating the electrode, the latter then being able to be studied after cycling. The battery also comprises a Whatman 125b type glass fiber separator. This separator 125b is much thicker than the first separator 125a, and makes it possible to absorb a large quantity of electrolyte, and to ensure that the quantity of available electrolyte is not limiting in long-term cycling.

[0131] The two electrodes are separated by a non-aqueous electrolytic solution impregnated in the glass fiber separator. The electrolyte used is prepared from lithium salt LiPF6 concentrated to one mole per liter dissolved in a ternary mixture of ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC), in the volume proportions 1 / 1 / 3.

[0132] Lithium plays the dual role of counter-electrode and reference electrode. The measured potentials are within the electrochemical stability range of the electrolyte solvents, i.e. between 4.5 V and 0.0 V relative to the Li+ / Li oxidation-reduction couple. The electrochemical properties were obtained in galvanostatic mode, i.e. by applying a current of constant intensity I and by following the evolution of the battery voltage as a function of time. The potential window is fixed between 0.05 V in discharge and 3 V in charge. The current density for cycling is 168 mA.g '.

[0133] The evolution of the specific capacity of each electrode is evaluated over time and the results are presented in Table 1.

[0134] [Tables 1] Specific capacity (mAh.g1) Carbon-graphite C-SiO2C18 powder C-SiO2C18 non-fluorinated block C-SiO2C18 fluorinated block Electrolyte Organic liquid Organic liquid Organic liquid Organic liquid 1st cycle - 931 1050 2145 10 cycles - 984 1073 2024 50 cycles - 975 1060 1765 100 cycles 300 925 1039 1678

[0135] In Table 1, the specific capacities of each of the electrodes are expressed per gram of active material, here SiO2, so that they are easily comparable from one electrode to another.

[0136] It results from the analysis of the different specific capacities that the C-SiO2Ci8 material does indeed have a specific capacity much higher than that of graphite carbon.

[0137] Furthermore, Table 1 shows that the C-SiO2Ci8 material does indeed exhibit greater specific capacities when formulated as a block rather than as a powder.

[0138] Also, the block formulation greatly simplifies the preparation of the electrode since the latter does not require powdering of the material, the production of an ink comprising the active material, a conductive carbon black and a binder, which should be coated on a current collector but can be used directly and in this case without a current collector.

[0139] Finally, Table 1 shows a significant gain in performance due to fluorination, since even after 100 cycles, the specific capacity is still much higher for the fluorinated material compared to the active material which is not.

[0140] Table 1 therefore demonstrates the obtaining of an active electrode material making it possible to meet the technical needs expressed by studying the solutions proposed in the prior art.

[0141] Example 3: Effect of impregnation.

[0142] In order to compare the gain achieved by impregnating the electrode material before its placement in the electrochemical cell, different materials from Example 2 were placed opposite different electrolytes, some being impregnated and others not.

[0143] For impregnated electrodes, the impregnation solution is a mixture of polymer loaded with lithium salts dissolved in acetonitrile, identical for the example, to the solution allowing the solid electrolyte to be obtained.

[0144] The electrodes are immersed in the impregnation solution until the impregnation of the electrode is 30% by mass.

[0145] Then, the electrodes are placed in an electrochemical cell, like the one described in [Fig.2].

[0146] In the case of the solid electrolyte, the separators 125a and 125b are replaced by a polymer membrane impregnated with lithium salts which acts as both separator and electrolyte.

[0147] Table 2 lists the results obtained for these materials according to the invention and outside the invention. Capacity in charge (mAh.g-1) C- SiO2C18 in block C- SiO2C[8 in fluorinated block C- SiO2C[8 in block Impregnation of the material Yes (according to the invention) Yes (according to the invention) Not impregnated (outside the invention) Electrolyte Liquid Organic liquid Organic liquid organic 1st cycle 1065 1124 945 5th cycle 973 1068 865 Capacity loss after 5 cycles (%) 8.7% 5.0% 8.3%

[0148] The results show a beneficial effect of impregnating the active electrode material with the polymer electrolyte solution, making it possible to improve the diffusion of Li ions, and thus the mass capacity.

[0149] In addition, fluorination makes it possible to improve the stability of the interface between the electrode and the electrolyte known as SEI, which reduces the loss of capacity.

[0150] The results presented here differ in absolute value from the results in Table 1, which is attributable to the aging of the samples between the obtaining of the two sets of data.

[0151] In particular, the difference in values ​​between the two fluorinated blocks, impregnated or not, is not due to the impregnation as such but also to a reduction in the fluorination observed due to the aging of the sample.

[0152] Similar results are obtained for a solid electrolyte showing better charge capacity and lower capacity loss after 5 cycles when the electrode material is impregnated and fluorinated.

Claims

Claims

1. A method of manufacturing an electrochemical cell comprising at least the following steps: A) impregnating with an impregnation composition a porosity of an electrode material comprising a plurality of particles (12) of a material comprising carbon, silicon and oxygen of general formula SiOxCy, x and y being strictly positive, fluorine (13) being grafted onto said particles, the plurality of particles forming a porous three-dimensional network, the active material further comprising carbon fibers (11) present in the porosity of the porous three-dimensional network and supporting the particles; and B) positioning the electrode material thus impregnated in an electrochemical cell, in contact with an electrolyte, the impregnation composition of step A) comprising the same charge carrier as the electrolyte of step B).

2. The manufacturing method of claim 1, wherein at least 20% of the porosity of the electrode material is impregnated with the impregnating composition.

3. Manufacturing method according to one of claims 1 or 2, in which the electrolyte is chosen from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiPF6 or an ionically conductive polymer membrane.

4. Manufacturing method according to any one of claims 1 to 3, in which the mass content of carbon fibers is between 1.5% and 3.5% relative to the total mass of the precursors leading to the non-impregnated SiOxCy material.

5. A manufacturing method according to any one of claims 1 to 4, wherein x is less than or equal to 4.

6. A manufacturing method according to any one of claims 1 to 5, wherein y is less than or equal to 40.

7. A manufacturing method according to any one of claims 1 to 6, wherein the electrode material forms the anode of the electrochemical cell.

8. Manufacturing method according to any one of claims 1 to 7, wherein the electrode material is obtained before step A) by a method comprising at least the following steps: a. obtaining a mixture comprising a precursor sol of the

9. particle material, as well as fibers of a carbon or carbon precursor; b. gelling the sol to obtain a gel in which the carbon or carbon precursor fibers are present; c. drying the gel; d. pyrolysis of the dried gel to obtain a pyrolyzed material; and e. fluorination of the resulting pyrolyzed material to obtain the active electrode material. Manufacturing method according to claim 8, wherein the precursor sol of step a) comprises a phenol or a polyphenol, an aldehyde and one or more silicon oxide precursors comprising or not one or more amine groups.

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