WO2021018598A1

WO2021018598A1 - Composite material and method for preparing same

Info

Publication number: WO2021018598A1
Application number: PCT/EP2020/070054
Authority: WO
Inventors: Olga Burchak; Loïc BAGGETTO
Original assignee: Enwires
Priority date: 2019-07-26
Filing date: 2020-07-15
Publication date: 2021-02-04
Also published as: EP4004993A1

Abstract

A process for the preparation of a composite material comprising a polymer material and metalloid particles and the obtained polymeric composite material. A process for the preparation of a composite material comprising carbon fibers and metalloid particles, the obtained carbonaceous composite material and its use for the preparation of an electrode, notably an anode, that may be used in an energy storage device.

Description

COMPOSITE MATERIAL AND METHOD FOR PREPARING SAME

Technical field

The invention concerns a process for the preparation of a composite material comprising a polymer base material and metalloid particles. The invention is further directed to a polymeric composite material that may be obtained by carrying out the process according to the invention.

The invention also relates to a process for the preparation of a composite material comprising carbon fiber and metalloid particles from a polymeric composite material according the invention. The invention also concerns the obtained carbon composite material and its use for the preparation of an electrode that may be used in an energy storage device.

State of the art

The field of energy storage, notably of rechargeable batteries, is in constant evolution and requires materials having ever-increased electrical and electrochemical activities [1]

A typical Lithium-ion battery is made up of positive cathode and negative anode materials separated by a separator impregnated by an electrolyte. The electrodes store Lithium ions Li⁺ and electrons while the electrolyte allows ionic conduction and prevents electron shuttling. Each electrode is generally composed of a current collector foil (or current collector), i.e. Copper Cu for the anode and Aluminum A1 for the cathode, coated with an electrode composite structure made of a binder, a conductive additive and of an active material.

The negative electrode materials are generally made of carbonaceous materials, such as graphite, carbon black or hard carbon. Such materials however lack freedom of shape and have limited storage capacity (amount of stored Lithium ions Li⁺ per unit of weight or volume) and poor rate performance (capability to deliver electric charge under high load).

Since several years, polymer materials have been considered as promising materials to create lighter, safer and better performing rechargeable batteries, in particular for the automotive market [1] Polymers are advantageous in that they can be shaped into various forms such as nanofibers, which allows to create novel nano- architectures [1-4] that can boost the performances of ion-delivery materials, such as lithium-ion batteries.

One general drawback of polymers is their lack of electrical, or electrochemical, or catalytic activities. This can be alleviated by changing the core chemical structure of the polymer material. However, such modifications often impact on their other properties such as their optical or mechanical parameters.

In order to increase the storage capacity and rate performance of electrode materials for Lithium-ion batteries, the addition of a conductive agent, such as Germanium (Ge), or intrinsic Silicon (Si), or doped Silicon (Si), to the pure carbon material (hard carbon, graphite, carbon black) has been identified by many industrials researchers as a way to move forward. To obtain materials with higher performances, several routes have been undertaken such as, non-exhaustively: (i) physically mixing additive nanoparticles with carbon, (ii) fabricating additive nano-objects with superior properties directly onto a current collector to suppress the need for carbon, or (iii) by growing novel carbon architectures (e.g. nano-trees, nano-pillars, nano-fibers) and depositing additives directly on their surfaces. These routes are generally made of several steps, involving the fabrication of the carbon support, and subsequently of the additive material.

The main drawback for the use of Germanium (Ge), Silicon (Si), or any Li- alloying elements, is the repeated and very high volume change occurring during the lithiation/delithiation reactions. This volume change can be as high as about 300 %, and may cause various materials failures. For instance, this may lead to electrode fracturing or delamination and isolation of the active material, surface roughening, creation of internal porosity (voids), etc. Moreover, the large volume changes can cause the rupture of the protective solid electrolyte interphase (SEI) film naturally formed on the surface of the electrode. In turn, this re-exposes the Silicon (Si) surface to the electrolyte and negatively consumes more electrolyte and Lithium Li ions from the positive electrode. Overall, this results in a decrease of the capacity retention and of the rate performance, and leads to degraded battery cycle life and potential safety hazards.

To limit the absolute volume changes and the material’s fracturing, nanosizing the additive material has been pursued using various avenues. Nanowires have one of the most advantageous morphology to date for the use in optoelectronic and energy storage applications since they have a very high surface-to-volume ratio, promoting fast surface exchanges and lowering energy barriers required for ionic and charge transfer mobilities. For battery applications, the small radius of the nanowires provides a more mechanically robust material and promotes the capacity retention while ensuring higher reaction kinetics.

Nanowires can be made using Vapor - Liquid - Solid (VLS) chemical vapor deposition (CVD) techniques [5-9] The VLS CVD growth requires thermal energy to promote the dissociation of the precursor and to form an eutectic liquid alloy between the catalyst and Si. It is thus essential that the support material can withstand those temperatures. Carbonaceous materials such as graphite, carbon black, carbon nanofibers, or hard carbons are known materials capable of enduring temperatures necessitated by the growth process.

WO 2019/020938 discloses the preparation of anode material comprising silicon particles and silicon nanowires.

Polymers however are very less likely to withstand these high temperatures. In particular, polymer materials decompose at such high temperatures, notably they decompose before the additive growth can actually start.

None of the suggested materials have permit to solve the above-mentioned technical problems.

In particular, none of the above-described processes permit to satisfy the electrical and electrochemical expectations of the battery industry.

Moreover, none of the above-described processes permit to prepare conductive material that may be freely shaped to correspond to new battery architectures.

There is still the need to provide a conductive material with improved electrical and electrochemical properties and that may be used as an anode material in an energy storage device.

There is still the need to provide anode materials with an enhanced storage capacity.

There is still the need to provide anode materials with improved performances, i.e. with an improved capability to deliver electric charge under high load.

There is still the need to provide electrodes which, when used in an energy storage device, have an improved cyclability. Summary of the invention

A first object of the invention consists in a process for the preparation of a composite material comprising a polymer material and metalloid particles (polymeric composite material), said process comprising:

(1) introducing into a chamber of a reactor at least:

- a polymer material, and

- a catalyst,

(2) introducing into the chamber of the reactor a precursor composition of the metalloid particles,

(3) decreasing the di oxygen content in the chamber of the reactor,

(4) applying a thermal treatment at a temperature ranging from 200 °C to 600 °C, and

(5) recovering the obtained product.

Preferably, the polymer material has a decomposition temperature, determined by thermal gravimetric analysis, superior or equal to 200 °C, preferably superior or equal to 300 °C, more preferably superior or equal to 400 °C, advantageously superior or equal to 500 °C.

Advantageously, the polymer material is chosen from fibrous polymer materials of synthetic or natural origin, preferably from fibrous polymer materials of synthetic origin.

More advantageously, the polymer material is chosen from polybenzothiazoles, polyamines, polyimides, polyurethanes, polybenzoxazoles, polyamides, polybenzimidazoles and mixtures thereof, preferably chosen from polyamides.

Even more advantageously, the polymer material is poly-paraphenylene ter ephtal amide.

Preferably, the precursor composition comprises at least one precursor compound of metalloid particles, preferably at least one precursor compound of silicon particles, even more preferably the precursor compound is chosen from silanes.

Advantageously, the thermal treatment applied on step (4) is performed at a temperature ranging from 200 °C to 600 °C, preferably from 250 °C to 550 °C, more preferably from 350 °C to 450 °C, and still more preferably from 400 °C to 450 °C.

According to a preferred embodiment, the process according to the invention further comprising a step of mixing the polymer material or the obtained composite material with conductive fillers, said mixing step being carried out before step (3) or after step (5).

The invention also relates to a composite material comprising a polymer material and metalloid particles (polymeric composite material) that may be obtained by the process as defined above and as described in more details here-after.

According to a favourite embodiment of the composite material the metalloid particles are in the form of wires.

Preferably, the metalloid particles present in the polymeric composite material according to the invention have semi-conducting properties, more preferably the metalloid particles are silicon particles.

Even more preferably, the metalloid particles, preferably the semi-conducting particles, are in the form of wires or rods or filaments or spheres, preferably in the form of wires.

Advantageously, the metalloid particles, preferably the semi-conducting particles are in the form of wires having an average length ranging from 50 nm to 500 pm, preferably from 500 nm to 50 pm.

Advantageously, the metalloid particles, preferably the semi-conducting particles are in the form of wires having a diameter ranging from 5 nm to 5 pm, preferably ranging from 10 nm to 50 nm.

The invention also concerns a process for the preparation of a composite material comprising carbon fibers and metalloid particles (carbonaceous composite material), said process comprising:

(i) preparing a composite material comprising a polymer material and metalloid particles by carrying out the process as defined above and as described in more details here-after,

(ii) carbonizing the polymer material of the composite material, and

(iii) recovering the obtained product.

According to a first variant, the carbonization (step ii)) is performed by plasma treatment. Preferably, according to this first variant, the plasma is obtained from a gas selected from: dinitrogen N2, dioxygen O2, difluor F2, dichloride CI2 and mixtures thereof.

According to preferred variant, the carbonization (step ii)) is performed by thermal treatment under an inert or reducing atmosphere at a temperature ranging from 400 °C to 1,000 °C.

According to a preferred embodiment, the process for the preparation of a composite material comprising carbon fibers and metalloid particles as defined above and as described in more details here-after comprises an additional step of mixing the polymer material or the polymer composite or the obtained carbon composite material with conductive fillers, said additional step being carried out before step (i), between steps (i) and (ii) or after step (ii).

The invention also relates to a composite material comprising carbon fibers and metalloid particles (carbonaceous composite material) that may be obtained by the process as defined above and as described in more details here-after.

According to an embodiment, the metalloid particles are in the form of wires. Preferably, the metalloid particles present in the carbonaceous composite material according to the invention have semi-conducting properties, more preferably the metalloid particles are silicon particles.

Advantageously, the metalloid particles, preferably the semi-conducting particles, are in the form of wires having an average length ranging from 50 nm to 500 pm, preferably from 500 nm to 50 pm.

Advantageously, the metalloid particles, preferably the semi-conducting particles, are in the form of wires having a diameter ranging from 5 nm to 5 pm, preferably ranging from 10 nm to 50 nm.

Preferably, the carbonaceous composite material according to the invention comprises less than 30 % by weight of residual polymer material, with respect to the total mass of the carbonaceous composite material, preferably less than 20 % by weight, more preferably less than 15 % by weight, even more preferably less than 10 % by weight, still more preferably less than 5 % by weight, and advantageously less than 1 % by weight.

The invention is also directed to an electrode that may be used in an energy storage device comprising a current collector and an active material layer, the active material layer comprising at least one binder and at least one carbonaceous composite material according to the invention.

The invention finally relates to an energy storage device comprising at least one electrode according to the invention.

Detailed description

The term "consists essentially of followed by one or more characteristics, means that may be included in the process or the material of the invention, besides explicitly listed components or steps, components or steps that do not materially affect the properties and characteristics of the invention.

The expression“comprised between X and Y” includes boundaries, unless explicitly stated otherwise. This expression means that the target range includes the X and Y values, and all values from X to Y.

The present invention relates to a process for the preparation of a composite material comprising carbon fibers and metalloid particles, said process comprising: a) the preparation of an intermediary composite material comprising a polymer material and metalloid particles, and

b) the carbonization of the polymer material into carbon fibers.

By “composite material”, we refer to a material made from at least two constituents materials with significantly different physical or chemical properties.

By“particles”, we refer to a divided material constituted of units having at least one of their external dimensions ranging from 50 nm to 500 pm, preferably ranging from 0.1 pm to 10 pm.

The external dimensions of the particles may be measured by any known method and notably by analysis of pictures obtained by scanning electron microscopy (SEM) of the composite material according to the invention. In the instant specification:

- the expressions“intermediary composite material” or“polymeric composite material” are used in an undifferentiated way to designate the composite material comprising a polymer material and metalloid particles, and

- the expression“carbonaceous composite material” is used to designate the composite material comprising carbon fibers and metalloid particles.

The invention firstly relates to a process for the preparation of a polymeric composite material, said process comprising:

(1) introducing into a chamber of a reactor at least:

- a polymer material, and

- a catalyst,

(3) decreasing the dioxygen content in the chamber of the reactor,

(4) applying a thermal treatment, and

(5) recovering the obtained product.

The invention also relates to a process for the preparation of a carbonaceous composite material, said process comprising:

i) preparing a composite material comprising a polymer material and metalloid particles according to the process defined above and which is described in more details here-after,

ii) carbonizing the polymer material of the polymeric composite material, and iii) recovering the obtained carbonaceous composite material. The polymer material

The process according to the invention comprises the use as a starting material of at least one polymer material.

By“polymer material”, we refer to a material predominantly composed of polymers. In the present description, the expression “polymer” denotes both homopolymers and copolymers. It includes mixtures of polymers, oligomers and mixtures of monomers, of oligomers and polymers.

Preferably, the polymer material is essentially constituted of polymers, and more preferably is solely constituted of polymers. Preferably, at least 75 % by mass of the polymer materials is constituted of polymers and their mixtures with monomers and/or oligomers, more preferably at least 80 % by mass, still more preferably at least 90 % by mass, even more preferably at least 95 % by masse, and advantageously at least 99 % by mass, with respect to the total mass of the polymer material.

The polymer material is selected among materials that may be used in the process of the invention as a support for the growth of the metalloid particles, preferably the semi-conducting particles.

It is important that the polymer material has an elevated heat-resistance so as to resist to the thermal treatment applied in step (4) of the process according to the invention.

The selection of polymer materials suitable for use in the present invention may be achieved by measuring their ability to resist temperature elevation in an inert or reducing atmosphere. This can be performed by measuring the temperature of decomposition of the polymer material, i.e. the minimal temperature value at which said polymer material begins to chemically decompose. The decomposition temperature of a polymer material may typically be determined by thermal gravimetric analysis (TGA).

Preferably, the polymer material has a decomposition temperature, determined by thermal gravimetric analysis, superior or equal to 200 °C, preferably superior or equal to 300 °C, more preferably superior or equal to 400 °C, and still more preferably superior or equal to 500 °C.

Advantageously, the polymer material is chosen from fibrous polymer materials.

More advantageously, the polymer material is constituted of pulp fibers.

By“fibrous polymer material”, we refer to a polymer material made of elongated polymer chains which are predominantly arranged along a same axis. More advantageously, the polymer material is chosen from synthetic and natural fibrous polymer materials, preferably from synthetic fibrous polymer materials.

Among natural fibrous polymer materials, mention may be made of fibers derived from bast, seeds, wood, fruits, grasses, leaves and their mixtures.

Preferably, the polymer material is chosen from synthetic fibrous polymer material. Advantageously, the synthetic polymer material is chosen from polybenzothiazoles, polyamines, polyimides, polyurethanes, polybenzoaxoles, polyamides, polybenzimidazoles and mixtures thereof.

More advantageously, the synthetic polymer material is chosen from polyamides.

Still more advantageously, the synthetic polymer material is chosen from polymers comprising aromatic and/or hetero cycles in their structure, more preferably from polymers comprising aromatic cycles.

According to a favourite embodiment, the synthetic polymer material is chosen from paraphenylene ter ephtal amide.

Such polymer materials are commercially available from the company DuPont de Nemours under the name Kevlar®.

The catalyst

The process according to the invention also comprises the introduction in the chamber of the reactor of a catalyst.

The function of the catalyst is to create growth sites on the surface of the polymer material.

Preferably, the catalyst is chosen from metals, bimetallic compounds, metallic oxides, metallic nitrides and metallic sulphides.

Among bimetallic compounds, mention may be made of Manganese and Platinum nanoparticles MnPt3, or Iron and Platinum nanoparticles FePt.

Among metallic oxides, mention may be made of ferric oxide nanoparticles FeiCh and tin oxide nanoparticles SnCh-_x (0 < x < 2).

Among metallic sulphides, mention may be made of Tin sulphides SnS.

Preferably, the catalyst is chosen from metals.

The metal which will form the catalyst is preferably introduced in the form of a thin metallic layer which, at the beginning of the process, liquefies under the effect of heat and then separates from its substrate by forming drops of liquid metal. The metal may also be introduced in the form of a metallic salt layer coated on the growth substrate which, at the beginning of the growth process, is reduced under the effect of a reducing gas such as for example dihydrogen FF. In pyrolytic processes, the metal may be introduced in the form of an organometallic compound which decomposes during the growth of the particles and which deposits metal in the form of nanoparticles or drops on the growth substrate.

Preferably, the catalyst is introduced into the chamber of the reactor in the form of drops or solid masses having a nanometric size.

More preferably, the catalyst is introduced into the chamber of the reactor in the form of metallic nanoparticles.

Even more preferably, the catalyst is chosen from Gold nanoparticles, Cobalt nanoparticles, Nickel nanoparticles, Bismuth nanoparticles, Tin nanoparticles, Iron nanoparticles, Indium nanoparticles, Aluminum nanoparticles, Manganese nanoparticles, Iridium nanoparticles, Silver nanoparticles, Copper nanoparticles and mixtures thereof.

Advantageously, the catalyst is chosen from Gold nanoparticles.

Preferably, the longest dimension of the catalyst nanoparticles ranges from 1 nm to 100 nm, more preferably from 1 nm to 50 nm, and still more preferably from 1 nm to 10 nm.

Advantageously, the catalyst nanoparticles are spherical and more advantageously, they have a diameter inferior or equal to 5 nm.

Gold nanoparticles that may be used in the process according to the invention are for example prepared and disclosed in M. Brust et al., J. Chemical Society, Chemical Communications , 7(7) : 801-802, 1994.

Preferably, the catalyst and the polymer material are introduced into the chamber of the reactor according to a mass ratio ranging from 1 : 1000 to 1 : 100, more preferably from 1 : 100 to 1 : 10, and still more preferably from 1 :50 to 1 :5.

According to a preferred embodiment, the polymer material and the catalyst are associated before their introduction into the reactor.

For the purposes of the invention, the term "associated" means that the polymer base material and the catalyst have previously undergone an association step corresponding to the attachment or deposition of at least a portion of the catalyst on at least part of the surface of the polymer base material. In other words, at least part of the catalyst is linked to the surface of the polymer base material, for example by physical bonding or by adsorption.

Preferably, at least 10 % of the surface of the polymer base material is coated with the catalyst, more preferably at least 25 %, and still more preferably at least 50 %. The association of the catalyst with the polymer base material allows the formation of a plurality of particles growth sites on the surface of the polymer base material.

The precursor composition of the metalloid particles

The process according to the invention also comprises the introduction into the chamber of the reactor of a precursor composition of metalloid particles.

By“metalloid particles”, we refer to particles comprising at least one element chosen from metalloid elements, said element being present in its elementary form or in the form of an oxide, a nitride or an alloy.

The precursor composition of metalloid particles comprises at least one precursor compound of metalloid particles.

By“precursor compound of metalloid particles”, we refer to a compound capable of forming metalloid particles on the surface of the polymer material by implementing the method according to the invention.

By“metalloid”, we refer to chemical elements which have properties in between those of metals and non-metals. In particular, and in the context of the invention, the term “metalloid” refers to any one of the following elements: Boron, Silicon, Germanium, Arsenic, Antimony and Tellurium.

Preferably, the precursor composition comprises at least one precursor compound of metalloid particles having semi-conducting properties.

By“particles having semi-conducting properties”, we refer to particles made of a material having semi-conducting properties.

By“material having semi-conducting properties”, we refer to a material having an electrical conductivity value falling between that of a conductor, such as metallic Copper, and an insulator, such as glass.

More preferably, the precursor composition comprises at least one precursor compound of Silicon or Germanium particles.

Even more preferably, the precursor composition comprises at least one precursor compound of Silicon particles.

The precursor compound of Silicon particles is a compound comprising at least silicon. Preferably, the precursor compound of Silicon particles is a silane compound or a mixture of silane compounds.

For the purpose of the invention, the term“silane compound” refers to compounds of formula (I):

Ri-(SiR₂R₃)n-R4 (I)

wherein:

- n is an integer ranging from 1 to 10, and

- Ri, R._2, R₃ and R₄ are independently chosen from hydrogen, C₁-C₁₅ alkyl groups and aryl groups optionally substituted with a C₁-C₁₅ alkyl group.

According to a first variant, the silane compound is a simple silane compound of formula (II):

Si„H(2„₊₂₎ (II)

with n an integer ranging from 1 to 10.

Preferably, according to this first variant, the precursor compound of silicon particles is silane SiFLt.

According to a preferred embodiment, the silane compound is an organic silane compound.

For the purpose of the invention, the expression“organic silane compound” refers to a compound of formula (I) wherein at least one of the Ri, R₂, R₃ and R₄ groups is different from hydrogen.

Preferably, according to this variant, n is equal to 1 and the silane compound is chosen from compounds of formula (III):

wherein Ri, R₂, R₃ and R₄ are independently chosen from hydrogen, C₁-C₁₅ alkyl groups and aryl groups optionally substituted with a C₁-C₁₅ alkyl group, it is being understood that R₄ is different from hydrogen.

Preferably, Ri, R₂, R₃ and R₄ are independently chosen from hydrogen, C₁-C₁₀ alkyl groups and aryl groups optionally substituted with a C₁-C₁₀ alkyl group.

According to a first embodiment, the organic silane compound is chosen from mono-, di- and tri-alkylsilanes. According to a preferred embodiment, the organic silane compound is chosen from compounds of formula (III) wherein at least one of Ri, R₂, R₃ and R₄ groups is an aryl group optionally substituted by a C1-C10 alkyl group, preferably is a phenyl group.

Preferably, according to this embodiment, the organic silane compound is chosen from mono-, di-, tri-arylsilanes.

More preferably, still according to this embodiment, the organic silane compound is chosen from: monophenylsilane Si(C6H5)H3, diphenylsilane Si(C6H5)2H2, triphenylsilane Si(CeH5)3H and mixtures thereof.

These compounds are advantageous in that they are air stable et do not need specific precautions during their handling.

Advantageously, the precursor compound of silicon particles is diphenylsilane Si(C₆H₅)₂H2.

According to a preferred embodiment, the precursor composition mostly comprises precursor compounds of metalloid particles.

Preferably, and according to this preferred embodiment, the precursor composition comprises at least 80% by weight of precursor compounds of silicon particles, with respect to the total weight of the precursor composition, more preferably at least 90 % by weight, even more preferably at least 95 %, and advantageously at least 99 % by weight.

More preferably, the precursor composition is essentially constituted of, even more preferably solely constituted of, one or more precursor compounds of silicon particles.

Preferably, the precursor compounds of metalloid particles and the polymer material are introduced into the chamber of the reactor according to a mass ratio ranging from 10: 1 to 200: 1, preferably from 10: 1 to 100: 1, and most preferably from 10: 1 to 25: 1.

Doping material

According to an embodiment of the invention, the process according to the invention further comprises the introduction into the chamber of the reactor of at least one doping material. In the purpose of the invention, the expression“doping material” refers to a material that is capable of modifying the conductivity of the metalloid particles. A doping material is for example a material rich in Phosphorus, Bore or Nitrogen.

Preferably, the doping material is introduced into the reactor by means of a precursor chosen from diphenylphosphine, triphenylborane and di- or triphenylamine.

Preferably, the doping material is introduced in the reactor according to a molar proportion ranging from 10 ⁴ % to 10 % with respect to the quantity of precursor compounds of metalloid particles, more preferably from 10 ² % to 1 %.

Process for the preparation of the polymeric composite material

The invention relates to a process for the preparation of a composite material comprising a polymer material and metalloid particles (intermediary composite material), said process comprising:

(1) introducing into a chamber of a reactor at least:

- a polymer material, and

- a catalyst,

(3) decreasing the dioxygen content in the chamber of the reactor,

(4) applying a thermal treatment, and

(5) recovering the obtained product.

According to a first variant, the decreasing in the dioxygen content in the chamber of the reactor is performed by placing under vacuum the reactor, preferably to a pressure inferior or equal to 10 ¹ bar.

According to second variant, the decreasing in the dioxygen content in the chamber of the reactor is performed by washing the chamber of the reactor with an inert gas.

In the purpose of the invention, the expression“washing the chamber of the reactor with an inert gas” means that an inert gas flow is injected into the chamber of the reactor in order to replace the gas present in the reactor by the injected inert gas.

Preferably, the inert gas is chosen from dinitrogen N2, Argon Ar, and mixtures thereof. Preferably, the chamber of the reaction is washed at least twice, more preferably at least 3 times.

Preferably, at the end of step (3), the dioxygen content in the chamber of the reactor is inferior or equal to 1 % by volume, with respect to the total volume of the chamber of the reactor.

According to a preferred embodiment, the process according to the invention comprises a preliminary step of associating the polymer material with the catalyst.

Preferably, the association step of the polymer material with the catalyst comprises:

- suspending the polymer material and the catalyst in a solvent, and

- evaporating the solvent.

According to a preferred embodiment, before evaporating the solvent, the suspension comprising the polymer material and the catalyst is stirred in order to promote contact between the polymer material and the catalyst.

Preferably, the suspension is stirred for at least 5 minutes, more preferably for at least 10 minutes, even more preferably for at least 15 minutes, and advantageously for at least 30 min.

The solvent used to suspend the catalyst and the polymer material may typically be chosen from: hexane, toluene, acetone, petrol ether, chloroform and dichloromethane.

Preferably, the solvent is hexane.

The solvent evaporation is performed according to any method known by the skilled person and which is suitable for evaporating the chosen solvent.

In the context of hexane, the solvent evaporation may for example be performed by means of a rotating vacuum evaporator.

According to a first embodiment, the polymer material, the catalyst and the precursor composition of the metalloid particles are mixed together before their introduction into the reactor.

According to a preferred embodiment, the reactor comprises at least two loading areas: a first loading area for receiving the precursor composition of the particles, and a second area for receiving the polymer material and the catalyst.

According to first variant, the first loading area and the second loading area are located on the same level in the chamber of the reactor. According to a favourite variant, the second loading area is elevated with respect to the first loading area.

Figure 1 is a schematic representation of a reactor that may be used to perform a process according to the invention.

Referring to figure 1, the reactor (10) comprises a chamber (12). The Chamber (12) of the reactor (10) comprises a first loading area (14) and a second loading area (16), the second loading area (16) being elevated with respect to the first loading area (14). In the first loading area (14) is loaded the precursor composition of the metalloid particles (18). In the second loading area (16) are loaded the catalyst and the polymer material (20). After having reduced the di oxygen content in the reactor (10) by placing it under vacuum at a pressure equal to 10 ¹ bar, the reactor (10) is heated by applying a thermal treatment which initiates the vaporization of the precursor composition of the metalloid particles (18) located in the first loading area (14). The precursor composition of the metalloid particles (18) in gaseous form fills the chamber (12). In particular, the precursor composition of the metalloid particles (18) is put in contact with the polymer material and the catalyst (20) located in the second loading area (16). The arrows (22) represent the motion of the precursor composition of the metalloid particles (18) in gaseous film inside the chamber (12) of the reactor (10). Upon contact with the catalyst, the precursor composition in gaseous form reacts to form metalloid particles.

Preferably, when a doping material is used, the precursor compound of the doping material is introduced into the first loading area, preferably as a mixture with the precursor composition of the metalloid particles.

Preferably, the thermal treatment is performed at a temperature ranging 200 °C to 600 °C, more preferably ranging from 250 °C to 550 °C, still more preferably from 300 °C to 500 °C, even more preferably from 350 °C to 450 °C, and advantageously from 400 °C to 450 °C.

The temperature for the thermal treatment is chosen according to the polymer material selected. In particular, the temperature of the thermal temperature has to be inferior to the decomposition temperature of the polymer material in order to prevent the deterioration of the polymer material [10] The determination of a suitable temperature to perform the thermal treatment is based on the skilled person’s general knowledge. In this range of temperatures, the precursor composition of the metalloid particles is pyrolyzed. It means that the precursor composition thermally decomposes to form pyrolysis vapors which, in contact with the catalyst, react to form or to grow metalloid particles on the surface of the polymer material.

During the process according to the invention, and because of the thermal treatment, the pressure in the reactor may increase. In particular, the pressure may increase to a value ranging from 10 to 70 bars, preferably from 20 to 40 bars. This internal pressure depends on the thermal treatment that is applied and is not necessarily controlled or monitored.

Preferably, the thermal treatment is applied from 1 minute to 5 hours, preferably from 10 minutes to 2 hours, and more preferably from 30 minutes to 60 minutes.

According to a preferred embodiment, the process according to the invention comprises an additional step (6) of washing the composite material obtained at the end of step (5).

Preferably, the composite material obtained at the end of step (5) is washed with an organic solvent, preferably chosen from: chloroform, ethanol, toluene, acetone, dichloromethane, petrol ether and mixtures thereof.

The raw material obtained at the end of step (5) is preferably washed at least twice, more preferably at least three times, and even more preferably at least four times.

Preferably, after step (6), the process further comprises a supplementary step of drying the washed composite material.

Drying is for example performed by placing the composite material into an oven, preferably at a temperature superior or equal to 50 °C, more preferably superior or equal to 70 °C.

Preferably, the drying is performed from 15 minutes to 12 hours, more preferably from 15 minutes to 2 hours, and even more preferably from 15 minutes to 60 minutes.

The polymeric composite material

The invention also concerns a polymeric composite material that may be obtained by carrying out the process here-above described.

The polymeric composite material comprises a polymer material and metalloid particles.

Preferably, the particles are in contact with the surface of the polymer material. More preferably, the particles are physically linked to the surface of the polymer material.

Advantageously, at least 50 % of the particles are not chemically linked to the surface of the polymer material by their extremities, preferably at least 75 %, more preferably at least 90 %, and even more preferably at least 95 %.

More preferably, the polymeric composite material comprises Silicon and/or Germanium particles.

Even more preferably, the polymeric composite material comprises Silicon particles.

Advantageously, at least 50 % of the metalloid particles of the polymer composite material are Silicon particles, preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, even more preferably at least 90 %, still more preferably at least 90 %, and advantageously at least 95 %.

More advantageously, the metalloid particles of the polymer composite material are all Silicon particles.

The polymeric composite material is preferably obtained in the form of a powder.

Preferably, at least part of the surface of the composite material is functionalized by an organic layer.

This functionalized layer results in particular from the decomposition of the precursor compound of the particles. For example, when the precursor composition comprises diphenylsilane Si^TE^FE as silicon particles precursor compound, the organic layer comprises phenyl groups.

Preferably, the organic layer represents from 1 % to 50 % by weight of the total weight of the particles, more preferably from 5 % to 25 % by weight, and more preferably from 5 % to 15 % by weight.

Preferably, the particles are in the form of wires, rods, filaments or spheres, preferably in the form of wires.

For the purposes of the invention, the term "wire" is intended to mean an elongated element whose shape is similar to that of a wire.

The size of the particles may be measured by several techniques well known by the skilled person such as for example by analysis of pictures obtained by scanning electron microscopy (SEM) from one or more samples of the composite material. Preferably, the particles have at least one of their external dimensions ranging from 10 nm to 500 pm, preferably ranging from 10 nm to 500 nm.

According a preferred embodiment, the particles are in the form of nanowires.

Preferably, the nanowires have an average length ranging from 50 nm to 500 pm more preferably from 500 nm to 50 pm.

Preferably, the nanowires have an average diameter ranging from 5 nm to 5 pm, more preferably from 10 nm to 50 nm.

Advantageously, the nanowires have an aspect ratio ranging from 10 to 10 000, preferably from 100 to 2 000, the aspect ratio being defined as the ratio of the average length of the particles to their average diameter.

Preferentially, at least 10 % of the nanowires are not linked to the polymer material by their extremities, more preferably at least 25 %, still more preferably at least 50 %, even more preferably at least 90 %, and advantageously at least 95 %.

The metalloid particles, notably the silicon nanowires, represent from 1 % to 50 % by weight of the polymeric composite material, with respect to the total weight of the polymeric composite material, more preferably from 1 % to 20 % we by weight, even more preferably up to 15 % by weight, still more preferably up to 10 %.

Preferably, the polymeric composite material according to the invention has a mass ratio of particles with respect to the polymer material ranging from 1 : 100 to 95: 100, preferably from 5: 100 to 80: 100, and still more preferably from 10: 100 to 60: 100.

Process for the preparation of the carbonaceous composite material

The invention further relates to a process for the preparation of a composite material comprising carbon fibers and metalloid particles, said process comprising: i) providing a composite material comprising a polymer material and metalloid particles as defined above,

ii) carbonizing the polymer material, and

iii) recovering the carbonaceous composite material.

By “carbonization”, we refer to a process permitting to produce a solid carbonaceous residue by pyrolysis or incomplete combustion of a polymeric composite material as defined above. In particular, the carbonization of the polymeric composite material permits to transform the polymer material present in the polymeric composite material into carbon fibers.

The carbonization of the polymer material may be performed according to any method known to the skilled person.

Advantageously, the carbonization (step ii) is performed by plasma treatment and/or by thermal treatment of the polymeric composite material.

According to a first embodiment, the carbonization of the polymer material is performed by plasma treatment.

Preferably, the plasma is prepared from a gas selected from: dinitrogen N2, ammonia NH3, dihydrogen ¾, dioxygen O2, difluor F2, dichloride CI2 and mixtures thereof.

The plasma treatment may be performed at high pressure, low pressure or ambient pressure. Preferably, the plasma treatment is performed at ambient pressure.

Advantageously, the composite material is exposed to the plasma for from 0,1 minute to 10 hours, more preferably for from 1 min to 10 min.

Preferably, plasma treatment is achieved with a power per surface area value ranging from 10 mW/cm² to 100 W/cm², more preferably from 1 W/cm² to 10 W/cm².

The determination of a suitable power per surface area value for the plasma treatment is based on the skilled person’s general knowledge. The skilled person knows in particular that the power of the plasma has to be adjusted by taking into consideration both the chemical nature of the plasma and the nature of the polymer composite material.

According to a preferred embodiment, the carbonization of the polymer material is performed by thermal treatment or thermal annealing.

The thermal treatment may be performed under an inert or reducing atmosphere. Preferably, the thermal treatment is performed under a reducing atmosphere.

A reducing atmosphere is typically obtained by replacing the ambient atmosphere with a reducing gas. Preferably, the reducing gas is constituted of a mixture of dihydrogen ¾ with an inert gas chosen from: helium He, neon Ne, argon Ar, krypton Kr, xenon Xe, radon Rn and dinitrogen N2, preferably with argon Ar.

The thermal treatment may be performed at high pressure (superior to 1 bar), low pressure (inferior to 1 bar) or ambient pressure (approximately 1 bar). Preferably, the thermal treatment is performed at ambient pressure. Preferably, the thermal treatment is performed at a temperature ranging from 400 °C to 1,000 °C, more preferably from 700 °C to 900 °C, even more preferably from 700 °C to 800 °C.

The temperature for the thermal treatment is chosen according to the selected polymer material. In particular, the temperature of the thermal temperature has to be superior or equal to the decomposition temperature of the polymer material so as to initiate the transformation of the polymer material into carbon fibers. The determination of a suitable temperature is based on the skilled person’s general knowledge.

Preferably, the thermal treatment is applied from 10 minutes to 24 hours, more preferably from 15 minutes to 10 hours, even more preferably from 30 minutes to 5 hours, still more preferably from 1 hour to 2 hours.

The thermal treatment may be performed according to any method known by the skilled person. For example, the thermal treatment may be performed in a horizontal quartz tube furnace.

The polymeric composite material can be introduced into the furnace in the form of a powder or can be preliminary pressed to form pellets of the polymeric composite material.

When the polymeric composite material is introduced in the form of a powder, it is preferably placed in a crucible.

According to a specific embodiment, the carbonization (step ii)) may correspond to a combination of one or several thermal treatments with one or several plasma treatments. In particular, according to this specific embodiment, the plasma and the thermal treatments may be performed simultaneously or successively. A combination of plasma and thermal treatments may for example be used to promote the activation of the polymer material.

The determination of the suitable carbonization procedure depends on the nature of the polymer and of the degree of carbonization desired. The skilled professional knows how to adapt the carbonization procedure in order to obtain the desired carbonaceous composite polymer.

The carbonization of the polymer material may be partial or complete.

Preferably, and at the end of the carbonization step (step ii)), at least 50 % by weight of the polymer material has been transformed into carbonaceous material, with respect to the total weight of polymer material initially present in the polymeric composite material, more preferably at least 75 % by weight, even more preferably at least 80 % by weight, still more preferably at least 90 % by weight, advantageously at least 95 %, and even more advantageously at least 99 % by weight.

More preferably, the carbonization of the polymer is complete. In particular, and at the end of the carbonization step (step ii)), there is no more polymer material in the carbonaceous composite material obtained at step iii).

The carbonaceous composite material

The invention also concerns a carbonaceous composite material that may be obtained by carrying out the process here-above described.

The carbonaceous composite material comprises carbon fibers and metalloid particles.

As previously described, the process for the preparation of the carbonaceous composite material uses a polymeric composite material as defined above as starting product.

Furthermore, the thermal and/or plasma treatment applied in this process do not significantly modify the size and the structure of the particles present in the composite material.

As a consequence, all the preferential features detailed above to characterize the metalloid particles present in the polymeric composite material are also preferential features for the metalloid particles of the carbonaceous composite material.

Preferably, the particles are in contact with the surface of the carbon fibers.

More preferably, the particles are physically linked to the surface of the surface of the carbon fibers.

Advantageously, at least 50 % of the particles are not chemically linked to the surface of the carbon fibers by their extremities, preferably at least 75 %, more preferably at least 90 %, and even more preferably at least 95 %.

Preferably, the carbonaceous composite material comprises silicon and/or germanium particles.

More preferably, the carbonaceous composite material comprises silicon particles.

Advantageously, at least 50 % of the metalloid particles of the carbonaceous composite material are silicon particles, preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, even more preferably at least 90 %, and advantageously at least 95 %.

More advantageously, the metalloid particles of the carbonaceous composite material are all silicon particles.

The carbonaceous composite material is preferably obtained in the form of a powder.

Preferably, at least part of the surface of the carbonaceous composite material is coated with an amorphous carbonaceous layer.

The amorphous carbonaceous coating present on the carbonaceous composite material results from the transformation, during the carbonization step, of the organic layer present on the surface of the polymer composite material into a carbonaceous material.

Preferably, the amorphous carbonaceous layer represents from 1 % to 50 % by weight of the particles, more preferably from 5 % to 25 % by weight, and more preferably from 3 % to 15 % by weight.

Preferentially, at least 10 % of the nanowires are not linked to the carbon fibers by their extremities, more preferably at least 25 %, still more preferably at least 50 %, even more preferably at least 90 %, and advantageously at least 95 %.

Advantageously, the carbonaceous composite material comprises less than 30 % by weight of polymer material, with respect to the total mass of the carbonaceous composite material, preferably less than 20 % by weight, more preferably less than 15 % by weight, even more preferably less than 10 % by weight, still more preferably less than 5 % by weight, and advantageously less than 1 % by weight.

More advantageously, the carbonaceous composite material does not comprise polymer material.

The metalloid particles, notably the silicon nanowires, represent from 1 % to 50 % by weight of the carbonaceous composite material, with respect to the total weight of the carbonaceous composite material, more preferably from 1 % to 20 % we by weight, even more preferably up to 15 % by weight, still more preferably up to 10 %.

Preferably, the carbonaceous composite material according to the invention has a mass ratio of particles with respect to the carbon fibers ranging from 1 : 100 to 95: 100, preferably from 5: 100 to 80: 100, and still more preferably from 10: 100 to 60: 100. Advantageously, the carbonaceous composite material according to the invention has an initial storage capacity (amount of stored lithium ions Li⁺ per unit of weight or volume) ranging from 100 to 2,000 mAh/g, preferably from 200 to 1,500 mAh/g, more preferably from 250 to 1,000 mAh/g, even more preferably from 300 to 500 mAh/g.

Further(s) treatment(s)

Mixing with conductive fillers

According to a particular embodiment, the processes here-above described may comprise an additional step of mixing the polymer material or the polymeric composite material or the carbonaceous composite material with conductive fillers.

Preferably, the conductive fillers are chosen from conducting carbon fillers.

More preferably, the conductive fillers are chosen carbon black or acetylene black, nanoporous carbon, graphite (natural graphite, artificial graphite) and mixtures thereof.

Even more preferably, the conductive fillers are chosen from graphite powders.

As an example of graphite that may be used as conductive fillers in the context of the invention, mention may be made of the graphite powder commercialized by the company Imerys under the name C-NERGY™ Actilion GHDR-15-4.

The mixing of the polymer material or of the composite materials with conductive fillers may be performed by wet or dry mixing, using or not using mixing media like rods, balls, ...

In particular, the mixing may be performed according to any known process and with any known grinding or mixing equipment.

For example, the mixing may be performed in a Turbula® T2F equipment or with an IK A® Ultra-Turrax disperser.

Preferably, the mixing is performed for at least 1 minute, more preferably from 5 minutes to 2 hours, even more preferably from 10 minutes to 1 hour.

Preferably, the mass ratio of conductive fillers with respect to the polymer material or the polymeric composite material or the carbonaceous composite material is from 1 : 10 to 10: 1, more preferably from 1 :5 to 5: 1, even more preferably from 1 :3 to 3: 1, and still more preferably is equal to 1 : 1.

According to a first variant, conducting fillers are mixed with the starting polymer material. Preferably, according to this variant, mixing is performed before step (1).

According to a second variant, conducting fillers are mixed with the polymeric conductive material.

Preferably, according to this second variant, mixing is performed after step (5) or (5’) but before step ii).

According to a third embodiment, conducting fillers are mixed with the carbonaceous composite material.

Preferably, according to this variant, mixing is performed after step iii).

Further (s) particles srowth(s)

The process according to the invention may further comprise, after step 5), or after step 6), or after step iii), the application of at least one of the following cycles:

(G) introducing into a chamber of a reactor at least:

- the polymeric composite material obtained after step 5), or the polymeric composite material obtained after step 6), or the carbonaceous composite material obtained at the end of step iii), and

- a catalyst,

(2’) introducing into the chamber of the reactor a precursor composition of the metalloid particles,

(3’) decreasing the di oxygen content in the chamber of the reactor,

(4’) applying a thermal treatment,

(5’) recovering the obtained product, and

(6’) optionally, washing the obtained product.

Preferably, and according to this particular embodiment, the process according to the invention comprises, before and/or after the carbonization of the polymer material, the application of from 1 to 10 of the cycles defined above, preferably from 1 to 5 cycles, and even more preferably 1 or 2 cycles.

The conditions of implementation and the favourite embodiments of steps (G), (2’), (3’), (4’), (5’) and (6’) are respectively the same as those described here above in the context of steps (1), (2), (3), (4), (5) and (6).

From the second cycle, the product reintroduced into the reactor is no more the product obtained at the end of step 5), 6) or iii) but the product obtained at the end of the previous cycle, i.e. the product obtained at the end of the step (5’) or (6’) of the previous cycle.

Thus, and according to this particular embodiment, the process according to the invention is applied several times on the same material and permits to obtain polymer composite materials and/or carbonaceous composite materials with an increased metalloid particles content.

According to a first variant, the cycle defined above is applied after step (5) or (6) on the polymeric composite material, i.e. before the carbonization of the polymer material.

According to a second variant, the cycle defined above is applied after step iii) on the carbonaceous composite material, i.e. after the polymer material has been carbonized.

According to a third variant, the cycle defined above is firstly applied after step 5) or 6) on the polymeric composite material and then on the carbonaceous composite material obtained at step iii). In particular, and according to this variant, the composite material according to the invention had been twice submitted to at least one cycle as defined above, once before the carbonization of the polymer material and once after the carbonization of the polymer material.

According a specific embodiment, several reactors may be used in cascade. In particular, and according to this variant, after having recovered and optionally washed the product obtained in output of a first reactor, the second cycle is performed in the next reactor.

Industrial applications

The invention also relates to a process for the fabrication of an electrode, said process comprising forming of an electrode from a carbonaceous composite material obtained from the process according to the invention. The forming of the electrode may be implemented directly from the carbonaceous composite material obtained from the above described process or by carrying out/ the above described process.

In a known manner, we prepare an ink (liquid slurry) from a binder, a carbonaceous composite material according to the invention, and optionally a conductive material notably chosen from carbonaceous materials. The ink is coated on a current collector and then dried. The invention more particularly concerns a process for the fabrication of an electrode, comprising at least the following steps:

- preparing or providing a carbonaceous composite material according to the invention,

- preparing an ink from the carbonaceous composite material,

- coating at least one part of a face of a current collector with the ink, and

- drying the ink.

The invention further relates to an electrode that may be used in an energy storage device, said electrode comprising a current collector and at least one active material coated on at least one part of a face of the current collector, said active material comprising at least one binder, at least one conductive material, and at least one carbonaceous composite material as above disclosed.

Binders are well known from the prior. Mentions may be made, by way of example, of carboxymethylcellulose (CMC).

The invention also concerns a process for the fabrication an energy storage device, said process comprising the use of at least one electrode as defined above.

The carbonaceous composite material according to the invention may be used as active material in an electrode of an electrochemical battery, notably in an anode of a lithium-ion battery. The carbonaceous composite material of the invention may also be used as an electrode material in a supercapacitor. To that extent, the invention also relates to an energy storage device comprising an electrode, notably an anode, according to the invention. For example, said energy storage device can be a lithium-ion battery. The important specific surface of the conductive interconnected network made of the metalloid particles allows the electrode to optimally dispatch through the totality of the active material a flow of electric charges. This configuration provides to the batteries or the capacitors a very high eligible current density. In the batteries, this configuration leads to a homogenous repartition of the lithium ions flow and of the mechanical stresses resulting from the insertion/disinsertion of the lithium ions which permits to maintain the integrity of the material. The electrical interconnection is ensured on the one hand by the contacts between the metalloid particles from one another and on the other hand by the contact between the metalloid particles and the carbon fibers resulting from the carbonization of the polymer material on the surface of which the particles have grown. An easy control of the polymer material and of the precursor compounds of the particles allows the synthesis of materials with chosen cyclabilities. It has been previously detailed that the particles may be doped throughout their growth or after their growth. The doping permits to increase the conductivity of the particles. In some extreme cases, the conductivity of the doped particles may in particular get close to the conductivity of the metals. This increasing of the conductivity of the particles is advantageous since it permits to significantly reduce the resistance of the particles to the insertion of lithium ions. In this manner, the electrode according to the invention improves the capacity of the energy storage device at the highest load speeds, see Chen et al., published in Electrochimica Acta 2011) 56, 5210-5213.

The polymer material permits to limit the mobility of the catalyst during the growth of the particles in such a manner that the catalyst particles keep their small size and that the metalloid particles have a homogenous size.

The structure of the composite material permits to improve the characteristics of the material when it is used as anode material in a Lithium-ion battery. For example, the growth of the particles on the surface of a polymer material and its subsequent carbonization allows the preparation of a composite material, notably a nanostructured composite material, which does not present the risks associated to nanopowders, notably during their handling.

The highly important specific surface of the carbonaceous composite material, combined with an optional doping of the particles to provide an improved conductivity of the web and, optionally a surface treatment to ensure a long-term thermal stability of the web, allows obtaining supercapacitor, micro-supercapacitor or ultra-micro- supercapacitor with an important energy density. Furthermore, the homogeneous and thin diameter of the particles provide to the electrode of the lithium-ion batteries an important mechanical stability during the lithiation/delithiation cycles. In particular, it provides more reliable anodes for lithium-ion batteries. Indeed, preferably, the particles have a very little size, notably nanometric, which is homogenous on the whole material. In particular, the standard deviation in the distribution of the diameter of the particles is inferior or equal to 50 %.

This quality gives to the final product an excellent cyclability, the small size of the particles allowing the relaxation of the mechanical stresses without a consequent volume change of composite material. The electrical energy storage element including said electrode has increased cycling durability relative to the electrodes of the prior art. Figures:

Figure 1 : schematic representation of a reactor that may be used for carrying out the process of preparation of a polymeric composite material according to the invention.

Figure 2: picture obtained by scanning electron microscopy from a sample of starting polymer material.

Figure 3A: picture obtained by scanning electron microscopy from a sample of Material 1.

Figure 3B: picture obtained by scanning electron microscopy from a sample of Material 2.

Figure 3C: picture obtained by zooming on Figure 3B centered on Silicon nanowires.

Figure 3D: picture obtained by scanning electron microscopy from a sample of Material 4.

Figure 4A: potential profile (X = the capacity of the cell in mA.h, Y = the potential of the cell in V) of the cell C2 prepared from Material 2.

Figure 4B: potential profile (X = the capacity of the cell in mA.h, Y = the potential of the cell in V) of the cell C4 prepared from Material 4.

Figure 5A: picture obtained by scanning electron microscopy from a sample of pure Si nanowires.

Figure 5B: picture obtained by zooming on Figure 5 A centered on Si nanowires.

Figure 6A: picture obtained by scanning electron microscopy from a sample of Material 8.

Figure 6B: picture obtained by zooming on Figure 6A centered on Si nanowire- based composite.

Figure 6C: picture obtained by zooming on Figure 6B centered on Si nanowires- based composite.

Figure 7A: picture obtained by scanning electron microscopy from a sample of Material 9.

Figure 7B: picture obtained by zooming on Figure 7A centered on Si nanowires- based composite.

Figure 8: potential profile (X = the capacity of the cell in mA.h, Y = the potential of the cell in V) of the cell C8 prepared from Material 8. It is understood that the examples and embodiments described herein are for illustrative purposes only and the various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. Accordingly, the following examples are offered to illustrate, but not to limit, the claimed invention.

Experimental part:

In the following examples, and unless otherwise indicated, the contents and percentages are given in mass.

Material

- polymer material: poly-paraphenylene ter ephtal amide having an average decomposition temperature equal to 550 °C. This polymer material is commercialized by the company E.I. du Pont de Nemours under the name Kevlar® 1F538.

- silicon precursor: diphenylsilane Si(C6H5)2H2, commercialized by the company Sigma-Aldrich (CAS Number: 775-12-2),

- silicon nanoparticles having an average particle size < 50 nm, commercialized by the company Alfa Aesar (CAS Number: 7440-21-3).

- catalyst: gold nanoparticles synthetized according to the protocol described in M. Brust et al., J. Chemical Society, Chemical Communications, 7(7), 801-802, 1994.

The diameter of the gold nanoparticles is from 1 to 4 nm (solution A) or about 5 nm (solution B). The surface of the gold nanoparticles is coated with 1-dodecanethiol molecules.

The gold nanoparticles are used in the form of a mother solution obtained by suspending the nanoparticles in toluene. The mother solutions A (1-4 nm) and B (5 nm) have a concentration of gold nanoparticles equal to 50 mg/mL.

- conductive fillers: graphite powder commercialized by the company Imerys under the name C-NERGY™ Actilion GHDR-15-4.

- carbon black, commercialized by the company Imerys under the commercial reference Timcal C-NERGY C65 (CAS Number: 1333-86-4).

- carboxymethylcellulose (CMC) commercialized by the company Alfa-Aesar (CAS Number: 9004-32-4). - styrene-butadiene rubber (SBR) commercialized by the company MTI Corporation (CAS Number: 9003-55-8).

- electrolyte: lithium hexaflurorophosphate LiPF₆ (1M) dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (1 : 1 in volume) comprising 10 % by weight of fluoroethylene carbonate (FEC) and 2 % by weight of vinylene carbonate (additive), commercialized by the company Solvionic.

- Reactor: stainless steel reactor (intern volume = 1L, diameter = 100 mm, height = 125 mm).

- Yttria stabilized zirconia (YSZ) grinding balls of 3 mm diameter commercialized by the company Inframat under the reference 4039GM-S030.

PART 1 - PROOF OF CONCEPT

- Preparation processes

A. Growth of silicon nanowires on a polymeric or carbonaceous material (Process 1)

a) Association of the polymer material with the catalyst

The polymer material (Kevlar®, 1 g) is suspended in dry hexane (50 mL). 80 mg of gold nanoparticles (1.6 mL of the mother solution A) are then added to the polymer material suspension under stirring. Stirring with a magnetic bar is conducted for 30 minutes. Subsequently, the mixture was dried on a rotatory evaporator (bath at 50 °C). b) Growth of the silicon nanowires

This step corresponds to the steps (1) to (5) of the process for the preparation of a polymer composite material according to the invention.

The recovered dry material obtained at the end of step a) is installed on a glass cup inside the reactor. 100 mL of diphenylsilane PhiSiFE are then poured at the bottom of the reactor.

The reactor is sealed and mounted inside a safety cabinet. After sealing the reactor, gas lines and temperature heating elements are connected to the reactor. The reactor is then put under vacuum and purged several times with N2 to remove air/moisture contaminants. Subsequently, the reactor is heated up by means of an electric resistance placed in contact with the exterior surface of the reactor. The heating cycle is as follows: a heating ramp of 30 minutes from 20 °C to 430 °C, a plateau of 60 minutes at 430 °C, the heating is stopped and then the reactor is cooled and maintained at ambient temperature for 3 hours. The reactor is finally opened to recover the obtained material.

Alternately, Process 1 can be applied to a material different from the polymer material. For example, Process 1 can be applied to a carbonaceous composite material.

B. Preparation of the carbonaceous composite material (Process 2)

The carbonization of the polymeric composite material is performed by thermal treatment.

The polymeric composite material obtained at the end of Process 1 is placed in a crucible which is then introduced in a horizontal quartz tube furnace. The inlet of the furnace is connected to argon Ar and dihydrogen FF gas lines with controlled amounts in a ratio of 94:6 (v/v) that are continuously flowed over the material. Thermal treatments are performed with a heating ramp of 10 °C/min up to a temperature equal to 750 °C for a duration of 2 h, followed by natural cooling. The furnace is finally opened to recover the carbonaceous composite material.

C. Mixing with conductive fillers (Process 3)

The starting polymer material or the polymeric composite material obtained at the end of Process 1, or the carbonaceous composite material obtained at the end of Process 1 + Process 2 is mixed with graphite powder using YSZ 3 mm diameter grinding balls, in an IKA® Ultra-Turrax disperser.

The polymer material or the polymeric composite material or the carbonaceous composite material and the graphite are introduced into the disperser according to a weight ratio equal to 1 : 1.

Mixing is performed for 10 minutes at rotational speed 7.

The mixed material is finally recovered for further processing or characterization. - Preparation of the materials

7 composite materials are prepared by alternating the processes 1, 2 and 3 here- above described:

Material 1 (according to the invention): Process 1

A composite material comprising a polymer material and silicon nanowires is prepared according to Process 1. Material 2 (according to the invention): Process 1 + Process 2

A carbonaceous composite material comprising carbon fibers and silicon nanowires is prepared by carbonizing Material 1. Material 2 thus results from the starting polymer material by the successive application of Process 1 and Process 2.

Material 3 (according to the invention): Process 1 + Process 2 + Process 1

The carbonized Material 2 is submitted to Process 1 (only step b)), the polymer/catalyst dry material being replaced by Material 2.

Material 4 (comparative): Process 2

The starting polymer material is carbonized according to Process 2.

Material 5 (according to the invention): Process 1 + Process 3 + Process 2

A composite material comprising a polymer material and silicon nanowires is initially prepared according to Process 1. The obtained polymeric composite material is then mixed with conductive fillers according to Process 3. The obtained mixture is finally carbonized according to Process 2. Material 5 thus results from the starting polymer material by the successive application of Process 1, Process 3 and Process 2.

Material 6 (according to the invention): Process 1 + Process 2 + Process 3

The carbonized Material 2 is further mixed with conductive fillers according to Process 3. Material 6 thus results from the starting polymer material by the successive application of Process 1, Process 2 and Process 3.

Material 7 (according to the invention): Process 3 + Process 1 + Process 2

The starting polymer material is mixed with conductive fillers according to Process 3. A polymer composite material is then prepared by submitting the obtained mixture to Process 1. The obtained polymer composite is finally carbonized according to Process 2. Material 7 thus results from the starting polymer material by the successive application of Process 3, Process 1 and Process 2.

Ill - Characterization of the materials

The topology of the starting polymer material and of the obtained materials 1, 2 and 4 is observed by scanning electron microscopy (SEM, ZEISS Gemini).

The obtained pictures are given on figures 2 and 3 A to 3D.

Figure 2 is a picture obtained by scanning electron microscopy of a sample of the starting polymer material. Figure 3A is a picture obtained by scanning electron microscopy of a sample of Material 1.

Figure 3B is a picture obtained by scanning electron microscopy of a sample of Material 2.

Figure 3C is a picture obtained by zooming on Figure 3B centered on Silicon nanowires.

Figure 3D is a picture obtained by scanning electron microscopy of a sample of Material 4.

On Figure 2, we observe that the starting polymer material does not have silicon nanowires on its surface. The sample is solely constituted of large polymeric fibers.

On Figure 3 A, we observe that the polymer material, after having been submitted to Process 1, retains a great deal of its original morphology. The original length of fibers is largely preserved. The loose individual fibers are more compact and closely packed due to the growth of silicon nanowires.

On Figure 3B, we observe the morphology of Material 2. A zoom on Figure 3B (Figure 3C) permits to observe the presence of a plurality of silicon nanowires on the surface of Material 2. The morphology of Material 2 is similar to that of the starting material with the presence of large fibers of compact strands.

On Figure 3D, we observe that the morphology of Material 4 is similar to that of the starting polymer material (Figure 2). In particular, we note the presence of large fibers of compact strands.

IV - Electrochemical performances of the materials

The electrochemical performances of the above prepared materials are evaluated by preparing coin-cells wherein the anode comprises one of the prepared materials as active material.

A - Preparation of a coin-cell

Liquid slurries (inks) are prepared by mixing, by use of an IKA® Ultra-Turrax disperser, each of the obtained material with carbon black as an electronic conductive additive, carboxymethylcellulose (CMC) with styrene-butadiene rubber (SBR) as binders, and deionized water as solvent. Mixing is achieved using YSZ 3mm diameter balls with a weight ratio of 6: 1 between balls and dry materials, here with 2 g of dry material and 12 g of YSZ balls. The weight ratios, with respect to the dry materials, are 90: 1 :9 (active material: carbon black:binders). Water is added to reach a viscosity allowing electrode processing, yielding to a dry content comprised between 30 and 40 % by weight, with respect to the total weight of the slurries.

Each electrode ink is cast on a copper foil (thickness = 12 pm). After drying in air, the electrodes are further dried at 65 °C in an oven for 2 hours. The electrodes are then cut into discs of 14 mm diameter, calendered at ca. 1 t/cm² and weighted, and were finally dried overnight in a vacuum drying at 110 °C.

Half coin-cells (Kanematsu KGK Corp®, stainless steel 316L) were prepared inside an Ar glovebox using metallic lithium Li as counter and reference electrodes (commercialized by MTI Corp.), a layer of Celgard 2325 (3 layers membrane, polypropylene-polyethylene-polypropylene, thickness = 25 pm) as separator, and the electrode of interest. The electrolyte used to impregnate the electrode and separator materials was 1M LiPF₆ dissolved in EC:DEC (1/1 v/v) with 10 wt% FEC (fluoroethylene carbonate) and 2 wt% VC (vinylene carbonate) additives. The cell was subsequently sealed with an automated press and taken out of the glovebox to be measured on a battery cycler.

The cells C2 and C4 have thus respectively been obtained from materials 2 and 4 here-above obtained.

B - Determination of the electrochemical performances

The performances of the cells C2 and C4 are determined by galvanostatic cycling using a Biologic BCS-805 cycling system equipped with 8 ways, each of the 8 ways comprising 2 different electrodes.

Three formation cycles were performed prior to regular cycling at 1 C-rate. The formation cycles are made of 1 cycle at C/20 and 2 cycles at C/10. Cycling is achieved using galvanostatic and potentiostatic discharging (lithiation), and galvanostatic charging (delithiation). 1 C-rate (1 C) corresponds to the current required to charge the electrode in 1 hour

1- Potential profile

The potential profile of the cells C2 and C4 have been determined during the cycling at C/10 by measuring the potential of the cell in function of its capacity.

The obtained profiles are given on Figures 4A and 4B. Figure 4A represents the potential profile obtained from cell C2 recorded during the second cycle at C/10 (third formation cycle).

Figure 4B represents the potential profiles obtained from cell C4 recorded during both the first and the second cycles at C/10 (second and third formation cycles).

On Figure 4A, we observe that the potential profile of the cell C2 obtained from

Material 2 shows the cumulation of the electrochemical activity of carbon black and silicon materials, which evidences that Material 1 is electrically and electrochemically active. The electrochemical activity of silicon with lithium ions is visible with the inflexion/pseudo-plateau near 0.45 V during charge (delithiation).

On Figure 4B, we observe that the potential profile of the cell C4 obtained from

Material 4 solely corresponds to the electrochemical activity of carbon black. In particular, we note that the carbonized polymer material does not modify the electrochemical properties of the cell.

2- Initial reversible capacity

The initial reversible capacity of the cells, measured at C/20 during the first cycle, is given in the following table:

Table 1

The cell C2 prepared from Material 2 (composite carbonaceous material according to the invention) has an increased reversible capacity with regard to the carbonized polymer used as starting material (cell C4, Material 4). Moreover, Material 2 exhibits a silicon active content of ca. 5 %.

The process according to the invention thus permits to obtain materials that may be used as active material in lithium-ion batteries and which have a high capacity value.

PART 2 - COMPARISON

This part relates to the comparison of two composite materials obtained respectively from direct growth of silicon nanowires on Kevlar® and from mixing Si nanowires, grown on silicon nanoparticles, with Kevlar® - Preparation processes

A. Composite Material 8: Direct growth of silicon nanowires on a polymeric material and subsequent carbonization

a) Association of the polymer material with the catalyst

The polymer material (Kevlar®, 1 g) is suspended in dry hexane (75 mL). 250 mg of gold nanoparticles (5 mL) of the mother solution B are then added to the polymer material suspension under stirring. Stirring with a magnetic bar is conducted for 30 min. Subsequently, the mixture was dried on a rotatory evaporator (bath at 45 °C).

b) Direct growth of the silicon nanowires

The recovered dry material obtained at the end of step a) is installed on a glass cup inside the reactor. 50 mL of diphenylsilane PhiSiLL are then poured at the bottom of the reactor.

c) Preparation of the carbonaceous composite material

The polymeric composite material is placed in a crucible which is then introduced in a horizontal quartz tube furnace. The inlet of the furnace is connected to argon Ar and dihydrogen ¾ mix gas line with controlled amounts in a ratio of 97:3 (v/v) that is continuously flowed over the material. Thermal treatment is performed with a heating ramp of 6 °C/min up to a temperature equal to 700 °C for a duration of 2 h, followed by natural cooling. The furnace is finally opened to recover the carbonaceous composite Material 8. B. Composite Material 9: mixing Si nanowires, grown on silicon nanoparticles with Kevlar® and subsequent carbonization

a) Synthesis of Silicon nanowires

Silicon nanowires are synthesized according to a previously described procedure (WO 2019/020938). A supported catalyst was prepared by disposing gold nanoparticles onto Si nanoparticles (Si NPs). The supported catalyst was prepared by impregnation. First, Si NPs (1.00 g) and «-hexane (75 mL) are mixed in a 250 mL round-bottom flask. 5 mL of the mother solution B (0.25 g) are added to the flask and the mixture is stirred at 1000 rpm for 2 h. The solvents are then evaporated using a rotary evaporator (bath at 45 °C).

The recovered dry material is installed on a glass cup inside the reactor. 50 mL of diphenylsilane PhiSiFL are then poured at the bottom of the reactor.

The material is then placed in a crucible which is then introduced in a horizontal quartz tube furnace. The inlet of the furnace is connected to argon Ar and dihydrogen FL gas lines with controlled amounts in a ratio of 97:3 (v/v) that are continuously flowed over the material. Thermal treatments are performed with a heating ramp of 6 °C/min up to a temperature equal to 700 °C for a duration of 2 hours, followed by natural cooling. The furnace is finally opened to recover the Si nanowires.

b) Preparation of polymeric composite material

A 2 L Erlenmeyer flask is filled with 4.66 g of Kevlar® and hexane (1 wt% solution). The suspension is stirred for 15 minutes at room temperature at 1200 rpm. 0.69 g of Si NWs grown on silicon nanoparticles are then added, and the mixture is stirred for 2 hours. The resulted mixture is filtered through a fritted glass funnel, washed with 200 mL of ethanol, and dried in an oven at 65 °C to recover the obtained material. c) Preparation of the carbonaceous composite material

The polymeric composite material is placed in a crucible which is then introduced in a horizontal quartz tube furnace. The inlet of the furnace is connected to an argon Ar and dihydrogen ¾ mix gas line with controlled amounts in a ratio of 97:3 (v/v) that are continuously flowed over the material. Thermal treatments are performed with a heating ramp of 6 °C/min up to a temperature equal to 700 °C for a duration of 2 hours, followed by natural cooling. The furnace is finally opened to recover the carbonaceous composite Material 9. - Characterization of the materials

The topology of Si nanowires grown on silicon nanoparticles and the obtained composite Materials 8 and 9 is observed by scanning electron microscopy (SEM, ZEISS Gemini).

The obtained pictures are given on Figures 5, 6 and 7.

Figure 5A is a picture obtained by scanning electron microscopy of a sample of pure Si nanowires.

Figure 5B is a picture obtained by zooming on Figure 5A centered on Silicon nanowires.

Figure 6A is a picture obtained by scanning electron microscopy of a sample of composite Material 8.

Figure 6B and 6C are pictures obtained by zooming on Figure 6A centered on Silicon nanowire-based composite.

Figure 7A is a picture obtained by scanning electron microscopy of a sample of composite Material 9.

Figure 7B is a picture obtained by zooming on Figure 7A centered on Silicon nanowire-based composite.

On Figure 5 A, we observe the morphology of Silicon nanowires grown on Silicon nanoparticles. A zoom on Figure 5A (Figure 5B) permits to observe the good dispersity in diameter of silicon nanowires (24) over silicon nanoparticles (26).

On Figure 6A, we observe the morphology of composite Material 8. The dash- dotted encompassed area highlights that the morphology of Material 8 is similar to that of the starting Kevlar® with the presence of large fibers of compact strands. Zooming on Figure 6A (Figure 6B) demonstrate the presence of a plurality of silicon nanowires (28) that are well dispersed all over the carbonaceous fibers (30). In addition, Figure 6C permits to observe that the silicon nanowires’ network is strongly embedded into the carbonaceous fibers (32) forming a continuous composite material.

On Figure 7A, we observe the morphology of composite Material 9. The morphology of Material 9 is similar to that of the starting Kevlar® with the presence of large fibers of compact strands (34). Zooming on Figure 7A (Figure 7B) shows that Si nanowires grown on silicon nanoparticles (36) are weakly anchored on the surface of the carbonaceous fibers (38).

Overall, these observations demonstrate that silicon nanowires are more strongly embedded into carbonaceous fibers in composite Material 8 than in composite Material 9, leading to the formation of a reinforced composite Material 8.

Further, Figures 6A, 6B and 6C of Material 8 show that the process according to the invention makes it possible to obtain materials wherein the silicon nanowires are dispersed homogenously over the entire surface of the polymer material. Whereas in the material obtained by simply mixing the silicon nanowires and the polymer material (Figure 7A), clusters of dispersed Si nanowires are observed.

Ill - Electrochemical characterization of the materials

The electrochemical characterization of the above prepared materials is performed by preparing coin-cells wherein the anode comprises one of the prepared materials as active material.

A Preparation of a coin-cell

The synthesized material was mixed with graphite powder (IMERYS Actilion) at a ratio of 1 :2. Carbon black C-NERGY C65 was added as an electronic conductive additive, carboxylmethyl cellulose (CMC) with styrene-butadiene rubber (SBR) were used as binders, and deionized water was employed as solvent. The weight ratios are 95: 1 :4 for the active material:C65:binders. Water is added to reach a viscosity allowing electrode processing, yielding to a dry content of about 40 wt%. Each electrode ink was cast on a copper foil of 20 pm. After drying in air, the electrodes were further dried at 65 °C in an oven for 2 hours. The electrodes were then cut into discs of 14 mm diameter, calendered at ca. 1 t/cm² and weighted, and were finally dried overnight in a vacuum drying at 110 °C.

Half coin-cells (Kanematsu KGK Corp®, stainless steel 316L) were prepared inside an Ar glovebox using metallic Li as counter and reference electrodes, a layer of Celgard 2325 as separator, and the electrode of interest. The electrolyte used to impregnate the electrode and separator materials was 1 M LiPF₆ dissolved in EC:DEC (1/1 v/v) with 10 wt% FEC (fluoroethylene carbonate) and 2 wt% VC (vinylene carbonate) additives. The cell was subsequently sealed with an automated press and taken out of the glovebox to be measured on a battery cycler. Thirteen formation cycles were performed prior to regular cycling at 1 C-rate. The formation cycles are made of 1 cycle at C/20 and 2 cycles at C/10 using galvanostatic and potentiostatic discharging (lithiation), and galvanostatic charging (delithiation).

The cells C8 and C9 have thus respectively been obtained from composite Materials 8 and 9 here-above obtained.

B Determination of the electrochemical performances

The performances of the cells C8 and C9 are determined by galvanostatic cycling using a Biologic BCS-805 cycling system equipped with 8 ways, each of the 8 ways comprising 2 different electrodes.

Three formation cycles were performed prior to regular cycling at 1 C-rate. The formation cycles are made of 1 cycle at C/20 and 2 cycles at C/10. Cycling is achieved using galvanostatic and potentiostatic discharging (lithiation), and galvanostatic charging (delithiation).

1- Potential profile

The potential profile of the cell C8 has been determined during the cycling at C/10 by measuring the potential of the cell in function of its capacity.

Figure 8 represents the potential profile obtained from cell C8 recorded during the second cycle at C/10 (third formation cycle).

On Figure 8, we observe that the potential profile of the cell C8 obtained from composite Material 8 shows the cumulation of the electrochemical activity of carbon black and silicon materials, which evidences that composite Material 8 is electrically and electrochemically active. The electrochemical activity of silicon with lithium ions is visible with the inflexion/pseudo-plateau near 0.45 V during charge (delithiation). 2- Initial reversible capacity

The initial reversible capacity of the cells, measured at C/20 during the first cycle, is given in the Table 2.

Table 2

The cell C8 prepared from composite Material 8 and the cell C9 prepared from composite Material 9 have similar initial reversible capacities. Therefore, composite Material 8 and composite Material 9 have the same silicon active content (ca. 16 %). Moreover, comparison of cell C8 and cell C2 reveals an improvement of the initial reversible capacity (460 vs. 360 mA.h/g), therefore and improvement of the silicon active content in composite Material 8 vs. composite Material 2 (ca. 16 vs. ca. 5 %). Overall, these results demonstrate that tuning reaction parameters allow the perfect control of the electrical and electrochemical performances of the carbonaceous composite materials.

BIBLIOGRAPHY

[1] M. Armand, J.-M. Tarascon, Building better batteries, Nature, 451 :652-657, 2008.

[2] George John, Subbiah Nagarajan, Praveen Kumar Vemula, Julian R. Silverman, C.K.S. Pill, Natural monomers: A mine for functional and sustainable materials - Occurrence, chemical modification and polymerization, Progress in Polymer Science , 92: 158-209, 2019.

[3] Romain Poupart, Daniel Grande, Benjamin Carbonnier, and Benjamin Le Droumaguet. Porous polymers and metallic nanoparticles: A hybrid wedding as a robust method toward efficient supported catalytic systems. Progress in Polymer Science , 96:21-42, 2019.

[4] S. Jothibasu, S. Mohanamurugan, R. Vijay, D. Lenin Singaravelu, A. Vinod, MR Sanjay, Investigation on the mechanical behavior of areca sheath fibers/jute fibers/glass fabrics reinforced hybrid composite for light weight applications, J. Industrial Textiles, 49(8), 1036-1060, 2020.

[5] Volker Schmidt, Joerg V Wittemann, Stephan Senz, and Ulrich Gosele. Silicon nanowires: a review on aspects of their growth and their electrical properties. Adv. Mater., 21(25-26):2681-2702, 2009.

[6] Candace K. Chan, Hailin Peng, Gao Liu, Kevin Mcllwrath, Xiao Feng Zhang, Robert A. Huggins, and Yi Cui. High-performance lithium battery anodes using silicon nanowires. Nat Nano, 3 ( 1 ) : 31—35 , January 2008.

[7] R.S. Wagner and W.C. Ellis. Vapor-liquid-solid mechanism of single crystal growth. Appl. Phys. Lett., 4(5):89-90, 1964.

[8] Mingyuan Ge, Jiepeng Rong, Xin Fang, and Chongwu Zhou. Porous doped silicon nanowires for lithium ion battery anode with long cycle life. Nano Lett, 12(5):2318— 2323, 2012. PMID: 22486769.

[9] Joo C Chan, Hoang Tran, James W Pattison, and Shankar B Rananavare. Facile pyrolytic synthesis of silicon nanowires. Solid-State Electron, 54(10): 1185—1191, 2010.

[10] B. Adeniran and R. Mokoya. Low temperature synthesized carbon superstructures with superior CO2 and hydrogen storage capacity. Journal of Materials Chemistry A, 3 :5148-5161(2015).

Claims

1. A process for the preparation of a composite material comprising a polymer material and metalloid particles, said process comprising:

(1) introducing into a chamber of a reactor at least:

- a polymer material, and

- a catalyst,

(3) decreasing the di oxygen content in the chamber of the reactor,

(5) recovering the obtained product. 2. The process according to claim 1, wherein the polymer material has a decomposition temperature, determined by thermal gravimetric analysis, superior or equal to 200 °C, preferably superior or equal to 300 °C, more preferably superior or equal to 400 °C, advantageously superior or equal to 500 °C. 3. The process according to any of claims 1 and 2, wherein the polymer material is chosen from fibrous polymer materials of synthetic or natural origin, preferably from fibrous polymer materials of synthetic origin.

4. The process according to any of the preceding claims, wherein the precursor composition comprises at least one precursor compound of silicon particles, preferably chosen from silanes.

5. A composite material comprising a polymer material and metalloid particles that may be obtained by the process as claimed in any of the preceding claims, wherein the particles are in the form of wires.

6. The composite material according to claim 5 wherein the metalloid particles are in the form of nanowires and the nanowires have an average length ranging from 50 nm to 500 mih, more preferably from 500 nm to 50 pm and an average diameter ranging from 5 nm to 5 pm, more preferably from 10 nm to 50 nm.

7. A process for the preparation of a composite material comprising carbon fibers and metalloid particles, said process comprising:

(i) preparing a composite material comprising a polymer material and metalloid particles by carrying out the process according to any of claims 1 to 4,

(ii) carbonizing the polymer material of the composite material, and

(iii) recovering the obtained product.

8. The process as claimed in claim 7, wherein the carbonization is performed by thermal treatment under an inert or reducing atmosphere at a temperature ranging from 400 °C to 1,000 °C.

9. The process as claimed in claim 7 or claim 8, comprising an additional step of mixing the polymer material or the polymer composite or the obtained carbon composite material with conductive fillers, said additional step being carried out before step (i), between steps (i) and (ii), or after step (ii).

10. A composite material comprising carbon fibers and metalloid particles that may be obtained by the process as claimed in any of claims 7 to 9 wherein the metalloid particles are in the form of wires.

11. The composite material as claimed in claim 10, wherein the metalloid particles have semi-conducting properties, preferably the metalloid particles are silicon particles.

12. The composite material as claimed in any of claims 10 and 11, wherein the semi conducting particles are in the form of wires having an average length ranging from 50 nm to 500 pm, preferably from 500 nm to 50 pm.

13. The composite material as claimed in claim 12, wherein the wires have a diameter ranging from 5 nm to 5 pm, preferably ranging from 10 nm to 50 nm.

14. The composite material according to any of claims 10 to 13, which comprises less than 30 % by weight of residual polymer material, with respect to the total mass of the composite material, preferably less than 20 % by weight, more preferably less than 15 % by weight, even more preferably less than 10 % by weight, still more preferably less than 5 % by weight, and advantageously less than 1 % by weight.

15. An electrode that may be used in an energy storage device comprising a current collector and an active material layer, the active material layer comprising at least one binder and at least one composite material as claimed in any of claims 10 to 14.

16. An energy storage device comprising at least one electrode as claimed in claim 15.