APPARATUS AND METHOD FOR THE CONTINUOUS OR SEMI-CONTINUOUS PRODUCTION OF A SILICON-BASED MATERIAL SUITABLE FOR THE MANUFACTURE OF LI-ION BATTERY ANODE

Abstract

The invention The present invention relates to a method for manufacturing an electrode material for lithium-ion batteries comprising: the reaction (200) of a mixture of Quartz (SiO2) and Silicon (Si) by heating, at a pressure below atmospheric pressure, to form a gas including silicon monoxide (SiO2), the condensation (300) of the gas including silicon monoxide (SiO2) to form crystals of amorphous silicon-based material SiOx, the grinding (400) of the crystals to obtain grains of amorphous silicon-based material SiOx having a particle size of less than 10 µm, the prelithiation (600) of the grains to obtain prelithified amorphous silicon-based material SiOx, the carbonation (700) of the grains to grow a carbon layer on the prelithified amorphous silicon-based material SiOx to obtain prelithified amorphous silicon-based material SiOx and Carbonate. Figure to be published with the abbreviation: Fig. 7

Description

Title of the invention: APPARATUS AND METHOD FOR THE CONTINUOUS OR SEMI-CONTINUOUS PRODUCTION OF A SILICON-BASED MATERIAL SUITABLE FOR THE MANUFACTURE OF LI-ION BATTERY ANODE FIELD OF INVENTION

[0001] The present invention relates to the general technical field of the production of silicon-based material usable for the manufacture of an electrode - in particular an anode - of lithium-ion batteries.

[0002] BACKGROUND OF THE INVENTION

[0003] 1. Use of graphite in lithium-ion batteries

[0004] Lithium-ion batteries have enjoyed enormous commercial success, particularly in the fields of electric vehicles and portable electronics.

[0005] The operation of such a battery is based on the reversible exchange of a lithium ion between: • a positive electrode, the cathode, and • a negative electrode, the anode.

[0006] Nowadays, lithium-ion battery technology relies heavily on the use of graphite-based anodes. However, it turns out that an anode using a graphite-based material has a theoretical limit of 372 mAh / g of specific energy capacity, as the amount of lithium that can be incorporated per unit mass of the graphite material is relatively small. This limits the potential for future increases in the specific energy capacity of lithium-ion batteries.

[0007] However, the growing markets for portable electronics and electric vehicles are leading to considerable demand for advanced lithium-ion batteries (LIBs) with high power and energy density. Conventional graphite anode materials cannot meet this demand due to their limited capacity.

[0008] 2. Use of silicon in lithium-ion batteries

[0009] To remedy this drawback, several research projects have turned to the use of silicon (Si) powder as a potential anode material for lithium-ion batteries.

[0010] Silicon has many advantages: • It exhibits higher gravimetric (3576 mAh / g) and volumetric (2194 Ah / L) capacities than lithium-ion batteries with a graphite-based anode (372 mAh / g, 719 Ah / L); indeed, the intercalated silicon and des- reversibly intercalates lithium ions through a reaction between silicon and lithium, 4Si + 15Li → Li₅Si₄, corresponding to a theoretical capacity of 3576 mAh / g (10 times greater than that of graphite-based anodes), • it is the second most abundant element in the Earth's crust (which (allows for a reduction in the manufacturing costs of lithium-ion batteries), and • It exhibits low electrochemical potential and environmental safety, enabling the development of safe, high-energy-density devices.

[0011] Thus, silicon-based anodes can often incorporate greater quantities of lithium per unit mass compared to graphite-based anodes that exchange lithium through the intercalation mechanism.

[0012] However, one of the disadvantages of silicon concerns its strong volume expansion: during lithiation and delithiation phases, silicon particles undergo a volume variation of the order of 280% (which induces very strong mechanical stresses likely to cause pulverization of anodes composed exclusively of silicon).

[0013] It follows that silicon-based anodes are not stable in cycling, exhibiting relatively weak reversibility and efficiency properties due to the tendency of silicon to change volume during lithiation and delithiation cycles.

[0014] This change in the volume of silicon can lead to the deterioration of the electrical contact between the grains of active material of the anode, which in turn will induce a decrease in the capacity - that is to say the amount of lithium that can be incorporated per unit mass - of the active anode material, throughout the life of the anode.

[0015] That is why, at present, the development of anodes based on pure silicon is rarely considered.

[0016] 3. Use of SiO₂

[0017] To improve the performance of silicon in cycling, it has already been proposed to make the anodes of lithium-ion batteries from silicon (Si) coated in non-stoichiometric silicon oxide (SiOx), the SiOx allowing to constrain the Si to limit its deformation.

[0018] This amorphous silicon-based SiOx material can be obtained from a mixture of a silicon (Si) filler of grade 3N or higher and a quartz (SiO2) filler by implementing a heating step and a cooling step. For the purposes of this invention, "3N grade silicon" means a silicon crystal with a purity of 99.9% (or "3N" for the sum of the "9s"). 3N grade silicon can be obtained by purifying metallurgical grade silicon (or "MG-Si" acronym for the Anglo-Saxon expression "Metallurgical Grade Silicon") to reduce the amount of impurities contained in the silicon crystal by a factor of 10.

[0019] In particular, the step of heating the mixture of silicon (Si) and quartz (SiO2) to a temperature of 1600°C at atmospheric pressure (the sublimation temperature of silicon monoxide SiO) makes it possible to obtain a gas containing silicon monoxide (SiO) according to the following reaction:

[0020] SiO2 + Si 2 SiO?.

[0021]

[0022] The step of cooling the gas containing silicon monoxide (SiO₂) to a temperature below 800°C to promote the restructuring, by disproportionation, of silicon monoxide (SiO₂) yields the amorphous silicon-based material SiO₂. More specifically, the condensation of the gas containing silicon monoxide (SiO₂) results in the following disproportionation reaction:

[0023] 2SiO -> SiO2 + Si,

[0024] to the production of the amorphous silicon-based material SiOx in solid form. This amorphous silicon-based material SiOx can then be ground to a desired particle size to obtain SiOx grains.

[0025] An example of a grain of amorphous silicon-based material SiOx is illustrated in [Fig. 1]. This grain consists of silicon PI particles Si precipitated in a matrix M of amorphous silicon dioxide SiO2.

[0026] The SiOx has: • a high capacity of -1000-2500 mAh g / g (depending on the x value), • a lower volumetric expansion (<150%) than that of pure silicon, and • Extended lifespan thanks to special microstructure engineering (formation of a Li4SiO4 compound acting as a buffer layer).

[0027] The resistance to volumetric expansion of a lithium-ion (Li-ion) battery anode made from these SiOx grains is improved, at the expense of the loss of part of the silicon capacity.

[0028] However, SiOx suffers from poor conductivity. The low initial Coulombic efficiency (ICE) of SiOx-based materials is one of the main drawbacks when they are used as anode materials in lithium-ion batteries, which consume lithium ions by shuttling between the cathode and the anode. This reduces the energy density of lithium-ion batteries including a SiOx-based anode.

[0029] Moreover, even if it is lower than that of pure silicon, the volumetric expansion of SiOx remains a problem, the mechanical stresses caused by this expansion always risking inducing deterioration of the SiOx-based anodes.

[0030] 4. Objective of the present invention

[0031] An object of the present invention is to propose a continuous or semi-continuous process—as opposed to batch production (or "batch" according to the terminology used in the field of industrial processes)—and an apparatus associated with this process, enabling the manufacture of an electrode material—in particular a negative electrode (anode)—for lithium-ion batteries, thereby remedying at least one of the aforementioned drawbacks.

[0032] In particular, an object of the present invention is to provide a continuous or semi-continuous process for manufacturing a material for obtaining micrometer-sized amorphous SiOx-based electrodes having: • significant stability of their capacity throughout their lifespan; • improved electrical conductivity, and • lower production costs due to the effect of continuous or semi-continuous production.

[0033] BRIEF DESCRIPTION OF THE INVENTION

[0034] To this end, the invention proposes a method for manufacturing an electrode material for lithium-ion batteries, the method comprising: • a step involving the introduction of a mixture of Quartz and Silicon into a reaction chamber, • a reaction step of the mixture in the reaction chamber, by heating to a silicon sublimation temperature and at a pressure lower than atmospheric pressure, to form a gas including silicon monoxide (SiO), • a condensation stage, in a condensation chamber, of the gas including silicon monoxide to form crystals of amorphous silicon-based material SiOx, remarkable in that the process also includes the following steps: • a grinding step, in a grinding chamber, of the crystals of amorphous silicon-based material SiOx to obtain grains of amorphous silicon-based material SiOx having a particle size of less than 10 pm, each grain comprising silicon particles included in a silicon dioxide matrix, • a prelithiation stage, in a prelithiation chamber, of grains to obtain prelithified amorphous silicon-based SiOx material grains, each grain comprising prelithiated silicon particles embedded in a lithium silicate matrix, • a carbonation step, in a carbonation chamber, to grow a layer of carbon on the prelithiated silicon-based amorphous material grains SiOx in order to obtain prelithiated and carbonized silicon-based amorphous material grains SiOx, each grain comprising the prelithiated silicon particles included in the lithium silicate matrix and a layer of carbon covering the lithium silicate matrix.

[0035] Thus, the method according to the invention proposes the implementation: • of one (or more) carbonation step(s) and • of one (or more) prelithification stage(s) • without the material formed being in contact with the ambient area until the prelithiation stage (including prelithiation); for the manufacture of carbonaceous and prelithiated SiOx - in a continuous or semi-continuous manner - usable for the manufacture of lithium-ion battery anodes.

[0036] The carbonation step(s) allow(s) a layer of carbon to be deposited on the surface of the SiOx particles. This carbon layer has two functions: • On the one hand, it allows the SiOx particles to be confined within a shell in order to reduce the undesirable effects linked to the volumetric expansion of SiOx, • On the other hand, the carbon layer improves the electrical conductivity of the SiOx particles, and therefore facilitates the transfer of lithium ions.

[0037] The prelithiation step(s) - the principle of which consists of adding in advance a lithium-containing material to the anode material to compensate for a loss of lithium during the first cycles of use of a lithium-ion battery - makes it possible to improve the coulombic efficiency (CE) and the cycle life of the lithium-ion battery.

[0038] Furthermore, the fact that the process is carried out continuously or semi-continuously reduces the costs (and improves the productivity) associated with the production of the silicon-based material suitable for manufacturing lithium-ion battery electrodes. Indeed, a common drawback of various batch processing methods is that their productivity is limited because the batch processing time is quite long, since it is necessary, for the production of each new batch, to perform: • loading the reaction chamber, • the generation of a depression in the reaction chamber and the condensation chamber, • heating the mixture of Silicon and Quartz placed in the reaction chamber, the cooling and atmospheric pressure adjustment of the reaction and condensation chambers for the recovery of amorphous silicon-based SiOx crystals, cleaning of reaction and condensation chambers, loading, unloading and cleaning the grinding chamber, • the loading, unloading, heating and cleaning of the different pre-carbonation, pre-lithiation, carbonation and fluorination chambers.

[0039] Also, the fact that the different stages of formation of the material based on silicon SiOx, grinding, pre-carbonation and pre-lithiation are carried out without contact with ambient air to limit the risks of oxidation of the surface of the crystals / grains by absorption of water or -OH- groups contained in the ambient air.

[0040] Preferred but not limiting aspects of the process according to the invention are as follows: for the reaction step: • The temperature can range between 1200°C and 1400°C, and • the pressure can be one thousand to ten thousand times lower than atmospheric pressure, in particular approximately equal to 10 Pascals; The prelithiation stage can be carried out before or after the carbonation stage; The prelithiation stage can be carried out in the solid phase, said prelithiation stage including the sub-stages consisting of: In a mixer in the prelithiation chamber, mix the grains of amorphous silicon-based SiOx material with a precursor powder to obtain a mixture: the precursor being chosen from lithium, lithium hydride or lithium carbonate, the quantity of precursor being less than 20% by weight of the mixture, preferably less than 15% by weight of the mixture, and even more preferably less than 10% by weight of the mixture, inject an inerting gas, said inerting gas including argon and / or nitrogen, to heat, at atmospheric pressure, in a rotary kiln of the prelithiation chamber, the mixture to a temperature below 1000°C, preferably below 900°C, and even more preferably approximately 800°C, in order to obtain the grains of amorphous material based on prelithiated silicon SiOx; The carbonation step can be carried out in the vapor phase, said carbonation step including the substeps consisting of: • Introduce the prelithiated silicon-based amorphous SiOx material grains into a rotary kiln in the carbonation chamber, • inject, into the rotary kiln of the carbonation chamber, a gas containing: • acetylene and nitrogen, or • acetylene and argon, • heat the grains and the gas, at atmospheric pressure, in the rotary kiln of the carbonation chamber, to a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains of amorphous material based on prelithified and carbonized silicon SiOx; the carbonation step may further include a substep consisting of injecting, into the rotary kiln of the carbonation chamber, a gas containing methanol; the process may further include a pre-carbonation step, in a pre-carbonation chamber, to grow a porous layer of carbon on the grains of silicon-based amorphous material SiOx, said pre-carbonation step being carried out prior to the pre-lithiation step and enabling the production of pre-carbonized silicon-based amorphous material SiOx grains, each grain (G2) comprising the pre-lithized silicon particles included in the silicon dioxide matrix, and a porous layer of carbon covering the silicon dioxide matrix; The pre-carbonation stage may include sub-stages consisting of: • Introduce the grains of amorphous silicon-based SiOx material into a rotary kiln in the pre-carbonation chamber, • inject, into the rotary kiln of the pre-carbonation chamber, a gas containing: • acetylene, methanol and nitrogen, or • acetylene, methanol and argon (Ar), • heat the grains and gas, at atmospheric pressure, in the rotary kiln of the pre-carbonation chamber, to a temperature below 1100°C, preferably below 1000°C, and even more preferably approximately equal to 900°C, to obtain the grains of amorphous material based on pre-carbonated silicon SiOx; • the process may further include a step of fluorinating prelithiated and carbonized silicon-based amorphous material grains in a fluorination chamber, to obtain prelithiated, carbonized and fluorinated silicon-based amorphous material grains, each grain comprising prelithiated silicon particles included in the lithium silicate matrix, the carbon layer covering the lithium silicate matrix, and fluorine particles on a surface of the carbon layer.

[0041] The invention also relates to an apparatus for manufacturing an electrode material for lithium-ion batteries, said apparatus comprising: • a reaction chamber including a heating system to form a gas including silicon monoxide by heating a mixture of quartz and silicon to a silicon sublimation temperature and a pressure below atmospheric pressure, • a condensation chamber for condensing the gas containing silicon monoxide and forming crystals of amorphous silicon-based material SiOx, notable in that the device further comprises: • a grinding chamber for grinding the crystals of amorphous silicon-based material SiOx to obtain grains of amorphous silicon-based material SiOx with a particle size of less than 10 pm, each grain comprising silicon particles included in a silicon dioxide matrix, • a prelithiation chamber downstream of the grinding chamber, to add lithium to the grains in order to obtain prelithified silicon-based amorphous SiOx material grains, each grain comprising the prelithified silicon particles included in a lithium silicate matrix, • a carbonation chamber downstream of the prelithiation chamber, to grow a layer of carbon on the prelithiated silicon-based amorphous material grains SiOx in order to obtain prelithiated and carbonized silicon-based amorphous material grains SiOx, each grain comprising the pelithiated silicon particles included in the lithium silicate matrix and a layer of carbon covering the lithium silicate matrix.

[0042] Preferred but not limiting aspects of the apparatus according to the invention are as follows: The pre-lithiasis chamber may include: • a mixer to mix the grains of amorphous silicon-based SiOx material with a precursor powder to obtain a mixture: • the precursor being chosen from lithium, lithium hydride or lithium carbonate, • the quantity of precursor being less than 20% by weight of the mixture, preferably less than 15% by weight of the mixture, and even more preferably less than 10% by weight of the mixture, • a rotary kiln to heat, at atmospheric pressure, the mixture to a temperature below 1000°C, preferably below 900°C, and even more preferably substantially equal to 800°C, to obtain the grains of amorphous material based on prelithified silicon SiOx; The carbonation chamber may include a rotary kiln for heating prelithiated silicon-based amorphous SiOx material grains with a gas containing: • acetylene and nitrogen, or • acetylene (C2H2) and argon (Ar), • at a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains of amorphous material based on prelithified and carbonized silicon SiOx; The apparatus may further include a pre-carbonation chamber comprising a rotary kiln to heat the grains and a gas containing: • acetylene, methanol and nitrogen, or • acetylene, methanol and argon, • at a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains of amorphous material based on pre-carbonized silicon SiOx; The apparatus may further include a fluorination chamber for grains of prelithitized and carbon-based amorphous silicon-based material (SiOx), to obtain grains of prelithitized, carbon-based, and fluorinated amorphous silicon-based material (SiOx), each grain comprising silicon particles embedded in the lithium silicate matrix, the carbon layer covering the matrix of lithium silicate, and fluorine particles on a surface of the carbon layer. Brief description of the drawings

[0043] Other advantages and features of the method and apparatus according to the invention will become clearer from the following description of several embodiments, given by way of non-limiting examples, based on the accompanying drawings in which: • [Fig. 1] is a schematic representation of a grain of amorphous silicon-based material SiOx, • [Fig.2] is a schematic representation of the transformation of a grain of materials, at different stages of manufacturing, • [Fig. 3] is a schematic representation of a production apparatus for electrode material for lithium-ion batteries, • [Fig. 4] is a schematic representation of a reaction chamber and of a condensation chamber, • [Fig. 5] is a detailed schematic representation of the chamber of reaction illustrated in [Fig.4], • [Fig. 6] is a detailed schematic representation of the chamber of condensation illustrated in [Fig.4], • [Fig. 7] is a schematic representation of a manufacturing process for electrode material according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] We will now describe different embodiments of the invention with reference to the figures. In these different figures, equivalent elements are designated by the same numerical reference.

[0045] 1. General Information

[0046] The method described in detail in point 3 is intended to be implemented in the apparatus described in point 2.

[0047] This process makes it possible to produce an amorphous material based on carbonized and prelithied silicon SiOx usable for the manufacture of lithium-ion battery anodes.

[0048] More specifically, heating a mixture of Quartz (SiO2) and Silicon (Si) generates a gas containing silicon monoxide (SiO), the condensation of which by cooling yields an amorphous silicon-based material, SiOx. Prelithiation and carbonation of this amorphous silicon-based material, SiOx, result in a carbonized and prelithied amorphous silicon-based material, SiOx.

[0049] 2. Apparatus for manufacturing an electrode material

[0050] With reference to [Fig. 3], the apparatus for implementing the method according to the invention comprises: • a reaction chamber 1, and • a condensation chamber 2 connected to the reaction chamber 1, • a grinding chamber 3 connected to the condensation chamber 2, • possibly a pre-carbonation chamber 4 connected to the chamber of grinding 3, • a pre-lithiation chamber 5 connected to the pre-carbonation chamber 4 or to the grinding chamber 3 (if the apparatus does not have a pre-carbonation chamber 4), • a carbonation chamber 6 connected to the pre-lithiation chamber 5, • possibly a fluoridation chamber 7.

[0051] The reaction chamber 1 allows the generation of a gas containing silicon monoxide (SiOx, with x'l). During operation, the pressure in the reaction chamber 1 can be on the order of 5-50 Pa.

[0052] The condensation chamber 2 cools the gas (from the reaction chamber 1) containing silicon monoxide (SiOx, with x'l) in order to form crystals of silicon-based SiOx material. During operation, the pressure in the condensation chamber 2 can be on the order of 5-50 Pa.

[0053] The grinding chamber 3 reduces the silicon-based SiOx crystals from the condensation chamber 2 to powder, yielding amorphous silicon-based SiOx grains with a desired particle size. Such grains G1 are illustrated in [Fig. 2]. They consist of silicon particles P embedded in a silicon dioxide SiO2 matrix M. During operation, the pressure in the grinding chamber 3 can be close to atmospheric pressure.

[0054] The pre-carbonation chamber 4 allows a layer of carbon to be deposited on the silicon-based SiOx material grains, in order to obtain pre-carbonized silicon-based SiOx material grains. Such grains G2 comprise silicon particles P embedded in a silicon dioxide SiO2 matrix M, said matrix M being coated in a carbon layer C. During operation, the pressure in the pre-carbonation chamber 4 can be close to atmospheric pressure.

[0055] The prelithiation chamber 5 allows the silicon-based SiOx material grains (carbon-based or not) to be "passivated." More precisely, the prelithiation chamber 5 transforms the silicon dioxide SiO2 matrix M into a lithium silicate matrix M' (Li2SiO3; Li4SiO5). This yields prelithified silicon-based SiOx material grains G3. Such G3 grains contain prelithified silicon particles P' (by lithium absorption): a LixSi alloy is formed (with x < 15 / 4). These P' particles are included in the lithium silicate matrix M' (Li2SiO3; Li4SiO5) possibly covered with a carbon layer C (when the device includes a pre-carbonation chamber 4).

[0056] Thanks to the formation of the LixSi alloy, the volume of the G3 grains of prelithiated silicon-based SiOx material increases ("pre-swelling" of the grains "reserve" a place for the future increase in volume of the anode during the charge-discharge cycles of the lithium-ion battery made from this material).

[0057] The fact that this "pre-swelling" of the G3 grains is carried out at high temperature makes it possible to limit the deterioration of the matrix M', the latter being relatively ductile at high temperature.

[0058] During operation, the pressure in the prelithiation chamber 5 is close to atmospheric pressure.

[0059] The carbonation chamber 6 allows: • to deposit a layer of carbon onto the grains of prelithiated silicon-based SiOx material (when the device does not include a pre-carbonation chamber 4), or • to increase the thickness of the previously deposited carbon layer (when the device does not include a pre-carbonation chamber 4), • in order to obtain G4 grains of prelithiated and carbonized silicon-based material (SiOx), said G4 grains comprising silicon particles (P) embedded in a lithium silicate matrix (Li2SiO3; Li4SiO5) (M') coated in a carbon layer (C). During operation, the pressure in the carbonation chamber (6) can be close to atmospheric pressure.

[0060] The fluorination chamber 7 modifies the surface of the prelithiated and carbon-based silicon SiOx grains G4 by attaching fluorinated radicals to the carbon layer. It produces prelithiated, carbon-based, and fluorinated silicon SiOx grains G5, as illustrated in [Fig. 2]. These G5 grains consist of prelithiated silicon particles P' embedded in a lithium silicate matrix M' (Li2SiO3; Li4SiO5) embedded in a carbon layer C on which fluorinated particles F are arranged. During operation, the pressure in the fluorination chamber 7 can be close to atmospheric pressure.

[0061] As illustrated in [Fig.3], the condensation chamber 2, the grinding chamber 3, the pre-carbonation chamber 4, the pre-lithiation chamber 5, the carbonation chamber 6 and the fluorination chamber 7 are connected by material transport channels V1-V5 allowing material to flow from the outlet of one chamber to the inlet of the next chamber: • A first transport pathway VI allows the silicon-based material crystals (SiOx) to be conveyed from the outlet of the condensation chamber 2 to the inlet of the grinding chamber 3, • a second transport channel V2 allows the G1 grains of amorphous silicon-based material SiOx to be conveyed from the outlet of the grinding chamber 3 to the inlet of the pre-carbonation chamber 4, • a third transport pathway V3 allows the G2 grains of pre-carbonized silicon-based SiOx material to be transported from the outlet of the pre-carbonation chamber 4 to the inlet of the pre-lithiation chamber 5, • a fourth transport channel V4 allows the prelithiated silicon-based SiOx material G3 grains to be transported from the outlet of the prelithiation chamber 5 to the inlet of the carbonation chamber 6, • a fifth transport channel V5 allows the G4 grains of prelithified and carbonized silicon-based SiOx material to be transported from the outlet of the carbonation chamber 6 to the inlet of the fluorination chamber 7.

[0062] Each transport path VI-V5 may consist of a worm gear housed in a gutter, the worm screw being made up of an axis on which helical threads are wound and whose rotation allows the material placed between said helical threads to be driven.

[0063] Advantageously, the first transport path V1 (for conveying the crystals between the condensation chamber 2 and the grinding chamber 3) may include an outlet chamber comprising a conduit associated with two (or more than two) sealed valves. A controller (not shown) allows the valves to be switched from a deactivated state to an activated state (and from an activated state to a deactivated state): • each valve blocking the passage of crystals and / or gas(s) between condensation chamber 2 and grinding chamber 3 in the deactivated state, • each valve allowing the passage of crystals and / or gas(s) between condensation chamber 2 and grinding chamber 3 in the activated state.

[0064] For filling the conduit, the controller activates the valve closest to the condensation chamber 2 and deactivates the valve closest to the grinding chamber 3. The crystals flow by gravity into the conduit. When the conduit is full of crystals, the controller deactivates the valve closest to the condensation chamber 2, then activates the valve closest to the grinding chamber 3. The crystals flow by gravity from the conduit to the grinding chamber 3. Once the conduit is empty, the controller deactivates the valve closest to the grinding chamber 3, and a new filling cycle can be initiated (activation of the valve closest to the condensation chamber 2 for filling the conduit, etc.). The presence of two valves allows the condensation chamber 2 to be maintained at a pressure lower than atmospheric pressure.

[0065] 2.1. Reaction chamber

[0066] With reference to [Fig. 4], the reaction chamber 1 comprises: • on the one hand, a set 11 including: • a dwelling 111, • a 112 reagent supply system, • a heating system 113, and • a crucible 114 intended to contain the reagents, allowing the reagents necessary for the generation of the gas containing silicon monoxide (SiO₂) to be contained and heated (at high temperature), and • on the other hand a supply line 12 allowing the circulation of the gas containing silicon monoxide (SiO) towards the condensation chamber 2.

[0067] 2.1.1. Housing

[0068] Housing 111 allows the gas generated during the reaction that forms the gas containing silicon monoxide (SiO₂) to be contained. Housing 111 is preferably airtight.

[0069] The housing 111 can be configured to withstand pressures lower than atmospheric pressure. Indeed, in certain embodiments (as illustrated in [Fig. 4]), the reaction chamber 1 can include one (or more) suction pump(s) (not shown) to generate a vacuum (or obtain an inert atmosphere) in the housing 111, the supply line 12, and the condensation chamber 2. In other words, the suction pump makes it possible to reduce the pressure inside: • of housing unit 111, • of the conveying conduit 12, and • of the condensation chamber 2 to a value lower than atmospheric pressure. This limits the temperature required to initiate the reaction that forms the gas containing silicon monoxide (SiO).

[0070] Furthermore, housing 111 is configured to withstand temperatures greater than or equal to 1000°C, in particular between 1200°C and 1800°C.

[0071] The housing 111 may be cylindrical, or of any other shape known to those skilled in the art. With reference to [Fig. 5], the housing 111 comprises a base 1112, one (or more) side wall(s) 1113, and a top wall 1114. In the embodiments illustrated in [Fig. 5], the top wall 1114 includes the opening 1111 allowing the flow of gas containing silicon monoxide (SiO) through the conveying pipe 12.

[0072] In certain embodiments, the housing 111 may include a thermally insulating structure 115 to reduce heat loss in the housing 111. Such a thermally insulating structure 115 may be composed of a thick ceramic packing of aluminum oxide (alumina or silicon carbide) arranged around the housing 111.

[0073] 2.1.2. Power Supply System

[0074] The reagent supply system 112 allows the crucible 114 to be filled with reagents, as will be shown from the following description of different embodiments of the process according to the invention.

[0075] The power supply system 112 comprises: • a receiving bowl 1121 intended to contain a reserve of reagents (Quartz and Silicon), • a distribution channel 1122 for the circulation of reagents, and • one (or more) airtight valve(s) 1123 to allow or stop the circulation of reagents.

[0076] The receiving bowl 1121 includes a base in which a through-hole is provided connected to one end of the distribution channel 1122, the other end of the distribution channel 1122 opening into the crucible 114. The valve(s) 1123 is / are mounted on the distribution channel 1122.

[0077] 2.1.3. Heating system

[0078] The heating system 113 allows the reactants to be heated to induce the reaction of generation of the gas containing silicon monoxide (SiO).

[0079] The heating system 113 can be of any type known to those skilled in the art. In particular, the heating system 113 can be of the resistive type, the inductive type, or the gas burner type.

[0080] For example, the heating system 113 includes one (or more) MoSi2 (molybdenum disilicate) resistance(s) disposed on the side wall(s) 1113 and possibly the bottom 1112 of the housing 111.

[0081] 2.1.4. Crucible

[0082] As illustrated in [Fig. 5], the crucible 114 can be made of a graphite frame externally coated with a refractory lining. Alternatively, the crucible 114 can be made of alumina, silica, metal, or silicon carbide (SiC).

[0083] The crucible 114 is configured to contain the reactants, and the by-products from the reaction generating the gas containing silicon monoxide (SiO).

[0084] The crucible 114 includes a pouring channel (or several channels) (not shown) for the evacuation of reaction by-products contained in the crucible 114 to an external pouch intended to receive it for subsequent storage. A sealing system - such as a plug made of carbon material - may be provided for opening and closing the casting channel(s).

[0085] 2.2. Condensation chamber

[0086] The condensation chamber 2 allows the silicon monoxide (SiO) contained in the gas from the reaction chamber 1 to be condensed. It can be of any type known to a person skilled in the art.

[0087] With reference to [Fig.6], the condensation chamber 2 may include a precipitation box 21, a cooling system 22, a vibrator 23 and an extraction nozzle 24.

[0088] 2.2.1. Precipitation chamber

[0089] The precipitation chamber 21 may be cylindrical in shape. It includes, for example, a side partition 212 and optionally a top partition and / or a bottom partition.

[0090] When the precipitation chamber 21 has an upper partition, this partition includes a through orifice connected to the conveying line 12 to allow the introduction - into the precipitation chamber 2 - of the gas from the reaction chamber 1. Similarly, when the precipitation chamber 21 has a lower partition, this partition includes a through orifice connected to the extraction nozzle 24.

[0091] When the precipitation box 21 is without an upper partition, an upper peripheral edge 211 of the side partition 212 is connected to the supply line 12. When the precipitation box 21 is without a lower partition, a lower peripheral edge 213 of the side partition 212 is connected to the extraction nozzle 24.

[0092] Advantageously, the side partition 212 (or all the partitions) of the precipitation chamber 21 may include a layer of smooth, non-adherent material such as a ceramic layer, a metal oxide layer, or a fluoropolymer layer. This facilitates / simplifies the detachment of the solidified amorphous silicon-based SiOx material deposited on the inner face of the side partition 212.

[0093] Furthermore, the side partition 212 of the precipitation chamber 21 may have a truncated cone shape. In particular, the generatrix of the side partition 212 may have a non-zero angle (especially between 1 and 45°) with the vertical axis A-A'. This also facilitates / simplifies the detachment of the solidified silicon monoxide deposited on the inner face of the side partition 212.

[0094] 2.2.2. Cooling system

[0095] The cooling system 22 can be composed, for example, of one (or more) heat exchanger(s) in which a heat transfer fluid circulates.

[0096] The integration of a cooling system 22 makes it possible to cool the gas from the reaction chamber 1 in order to condense the silicon monoxide (SiO) contained in the gas from the reaction chamber 1 on the inner face of the side partition 212.

[0097] In the embodiment illustrated in [Fig. 6], the cooling system 22 comprises a coil surrounding the side partition 212 along its entire height. A heat transfer fluid – such as water – circulates in the coil.

[0098] This makes it possible to reduce the temperature of the gas containing silicon (II) monoxide: • from a temperature of 1200°C to a temperature below 800°C when the device is used at a pressure below atmospheric pressure, or • from a temperature of 1600°C to a temperature below 800°C when the device is used at atmospheric pressure.

[0099] Cooling the gas contained in the condensation chamber 2 induces the solidification of the amorphous silicon-based material SiOx. This solidified amorphous silicon-based material SiOx is deposited on the inner face of the side wall 212 of the precipitation chamber 21.

[0100] 2.2.3. Vibrator

[0101] In order to ensure the efficiency of the gas cooling, the precipitation box 21 is associated with the vibrator 23 of the condensation chamber 2. The vibrator 23 is configured to generate vibrations on the surface of the side partition 212.

[0102] The generation of vibrations makes it possible to detach the solidified silicon-based amorphous material SiOx deposited on the inner face of the side partition 212.

[0103] Thus, the presence of a vibrator 23 makes it possible to limit the thickness of the layer of amorphous silicon-based SiOx material deposited on the inner face of the side partition 212 in order to ensure efficient cooling of the gas contained in the condensation chamber 2.

[0104] The vibrator 23 can be of the acoustic type, that is to say a vibrator converting electrical energy into acoustic energy in the ultrasonic range.

[0105] Alternatively, the vibrator 23 may be of the mechanical type, i.e. a mechanical system generating vibrations using a rotary, linear or electromagnetic mechanism.

[0106] 2.3. Grinding chamber

[0107] The grinding chamber 3 is of the "jet mill" type (also known as a "fluidized bed mill"). It allows granular or powdery materials to be ground by collision (attrition).

[0108] The grinding chamber comprises: • a container designed to hold the silicon-based SiOx crystals from condensation chamber 2, which may be introduced into the container continuously or not, and • fluid ejection nozzles (mixture of a neutral carrier gas, Nitrogen or Argon and the particles to be ground).

[0109] The enclosure comprises a substantially cylindrical body and a frustoconical bottom. An opening is provided in the upper part of the enclosure for the evacuation, towards the pre-carbonation chamber 4, of the grains G1 of amorphous silicon-based SiOx material whose size meets a desired particle size.

[0110] The fluid ejection nozzles are supplied with pressurized fluid (gas or inert vapor, such as nitrogen, argon, or air) via fluid sources (such as a compressor supplying the nozzles with fluid at a pressure between 7 and 30 bar) not shown. These ejection nozzles, housed in the side wall of the enclosure, are configured to generate substantially horizontal centripetal jets within the crystals contained in the enclosure in order to create crushing zones through impacts between the crystals (attrition).

[0111] These centripetal jets allow the finest grains (whose dimensions satisfy the desired particle size) to rise and are then continuously extracted from the upper part of the enclosure, while the larger grains (whose size is greater than the desired particle size), because they are insufficiently ground, fall back laterally into the enclosure.

[0112] Advantageously, the grinding chamber 3 may include a separator at the chamber outlet. This separator separates the coarse grains that can be carried along with the fine grains of the desired particle size towards the chamber outlet. These coarse grains, whose size exceeds the desired particle size, can be reintroduced into the chamber by any known technique for further grinding.

[0113] Such a grinding chamber 3 is known to those skilled in the art. Indeed, the fluidized bed grinding technique is described in particular in document WO 2012 / 014985.

[0114] The grains ground to the desired particle size are then moved to the pre-carbonation chamber 4.

[0115] 2.4. Pre-carbonation chamber and carbonation chamber

[0116] The pre-carbonation chamber 4 allows the G1 grains of amorphous silicon-based SiOx material to be thermally treated, the size of which meets the desired particle size.

[0117] The pre-carbonation chamber 4 comprises a tubular rotary kiln - of any type known to those skilled in the art - adapted to withstand lower temperatures at 2000°C, preferably 1500°C, even more preferably 1000°C, and in particular a temperature of 900°C.

[0118] Such a rotary kiln may include, for example: • a tubular reactor lined with an internal refractory material (e.g., graphite) associated with • means of propulsion (such as a motor) to drive the tubular reactor in rotation, • heating methods (flame, electric, inductive, microwave, etc.) to heat the inside of the tubular reactor, particularly to a temperature of 900°C • means of introducing a gas including one (or more) gaseous precursor(s) such as acetylene (C2H2) and / or argon (Ar), • an inlet for receiving G1 grains of amorphous silicon-based SiOx material, • an outlet for the evacuation of G2 grains of pre-carbonized silicon-based SiOx material, • an outlet for the gaseous products of the reaction (in particular H2 and argon).

[0119] Preferably, the rotating tubular furnace is slightly inclined relative to a horizontal plane in order to ensure good mixing of the G1 grains and to guarantee homogeneous deposition of carbon on the Gl grains.

[0120] Such a pre-carbonation chamber 4 being known to the person skilled in the art, it will not be described in further detail hereafter.

[0121] The reader will appreciate that the carbonation chamber 6 can be of the same type as the pre-carbonation chamber: • an inlet of the carbonation chamber 6 being configured to receive G3 grains of pre-carbonized and pre-lithianed silicon-based amorphous material SiOx, and • an outlet of the carbonation chamber 6 being configured to evacuate G4 grains of prelithiated and carbonized silicon-based SiOx material.

[0122] 2.5. Prelithiation chamber

[0123] The pre-lithiation chamber allows an amount of active lithium to be added to the silicon-based material used for manufacturing a lithium-ion battery electrode before the lithium-ion battery is put into operation.

[0124] This makes it possible to enrich the silicon-based material with lithium, in order to improve the stability of the capacity (energy storage) of the lithium-ion battery (obtained from said material) throughout its lifetime.

[0125] Indeed, during the first charge cycle of a lithium-ion battery, when the active material of the anode is brought to a lithium insertion potential, some of the lithium will react with the electrolyte to form a passivation layer on the surface of the anode.

[0126] The formation of this passivation layer consumes a non-negligible amount of lithium ions, which results in an irreversible loss of capacity of the lithium-ion battery (this loss being described as irreversible capacity and can be estimated at 5 to 20% of the initial capacity of the positive electrode), because the lithium ions that have reacted are no longer available for subsequent charge / discharge cycles of the lithium-ion battery.

[0127] Implementing a prelithiation step makes it possible to minimize, as much as possible, this loss during the first charge, so that the energy density of the lithium-ion battery is as high as possible.

[0128] With reference to the figure in [Fig.3], the prelithiation chamber 5 comprises: • a mixer 51, and • a rotary oven 52 downstream of the mixer 51.

[0129] The mixer 51 can be of any type known to those skilled in the art. It comprises: • a first inlet channel for the introduction of a powder containing lithium and / or lithium hydride and / or lithium carbonate, • a second inlet channel for the introduction of G2 grains of pre-carbonized silicon-based SiOx material, • a container configured to receive lithium and / or lithium hydride powder on the one hand, and G2 grains of pre-carbonized silicon-based SiOx material on the other hand, • an agitator to mix the G2 grains of pre-carbonized silicon-based SiOx material with lithium and / or lithium hydride powder.

[0130] The rotary kiln 52 can be of the same type as the kiln in the pre-carbonation and carbonation chambers. It allows the production of G3 grains of pre-carbonized and pre-lithiated silicon-based SiOx material by reaction of the following mixture: • G2 grains of pre-carbonized silicon-based SiOx material and • lithium powder and / or lithium hydride powder.

[0131] The rotary kiln 52 comprises: • an inlet for introducing the mixture composed of the powder containing the lithium source (stabilized metallic lithium or hydride) of lithium or lithium carbonate), and G2 grains of pre-carbonized silicon-based SiOx material, • an outlet light for the removal of G3 grains of pre-carbonized and pre-lithiated silicon-based SiOx material, • an outlet for the gaseous products of the reaction (including H2, CO, CO2 and argon).

[0132] The use of a tubular rotary kiln for heating the mixture (SiOx + Li or SiOx + LiH) ensures good mixing of the grains so that the reaction is homogeneous over the entire treated volume.

[0133] 2.6. Fluoride chamber

[0134] The fluorination chamber 7 allows the surface of the G4 grains from the carbonation chamber to be modified by attaching fluorinated radicals to them.

[0135] The fluoridation chamber 7 comprises a furnace including: • initial access for the introduction of G5 grains of prelithiated and carbonized silicon-based SiOx material, • a second access point for the introduction of a gas including an argon-based compound (Ar), and a tetrafluoromethane-based compound (CF4), • a tank to contain the G5 grains and the gas, • a heating element (gas burner, electric burner, etc.) to apply a heat treatment in the tank, • a third access point for the removal of G5 grains of carbonaceous, prelithiated and fluorinated silicon-based SiOx material, • an outlet for the gaseous products of the reaction (including H2, SiF4, CF4 and argon).

[0136] Fluorination of the G5 grains of prelithiated and fluorinated silicon-based SiOx material allows modification of the surface of said G5 grains. This has the effect of limiting the decomposition of electrolyte on the surface of the anodes of lithium-ion batteries made with such a material.

[0137] 3. Method for manufacturing the electrode material

[0138] We will now describe different examples of the process according to the invention for the manufacture of the amorphous silicon-based material SiOx suitable for the production of lithium-ion battery anodes.

[0139] With reference to [Fig.7], the process comprises: • an introduction step 100 into the reaction chamber 1 of a mixture composed of: • a charge of quartz (SiO2), and • of a silicon (Si) charge, • a reaction step 200 to produce the gas containing silicon monoxide, the reaction step including a substep of heating the mixture, • a 300 condensation step of the gas containing silicon monoxide to produce crystals of amorphous silicon-based material SiOx, • a 400 grinding step to reduce the crystals into G1 grains of amorphous silicon-based SiOx material, • an optional pre-carbonation step 500 to deposit a carbon layer on the G1 grains in order to obtain G2 grains of pre-carbonized silicon-based amorphous material SiOx, • a prelithiation step 600 to incorporate lithium into the G2 grains in order to obtain G3 grains of amorphous material based on pre-carbonized and pre-lithiated silicon SiOx, • a carbonation step 700 to grow the carbon layer on the G3 grains in order to obtain G4 grains of amorphous material based on prelithified and carbonized silicon SiOx, • an optional 800 fluorination step to deposit fluorinated radicals on the carbon layer of the G4 grains in order to obtain G5 grains of amorphous material based on prelithified, carbonized and fluorinated silicon SiOx.

[0140] 3.1. Introduction step and reaction step

[0141] The introduction steps 100 and reaction steps 200 can be implemented in the reaction chamber 1.

[0142] The introduction step 100 of the process includes filling the crucible 114 with a mixture composed of a quartz charge and a silicon charge, for example 3N grade silicon.

[0143] This mixture can be introduced into the crucible 114 by means of the feeding system 112 of the apparatus described previously.

[0144] The mixture contained in the tank 114 is then heated by the heating system 113 to induce the generation of the gas containing silicon monoxide (SiO₂). In particular, the heating step, at a temperature between 1200°C and 1400°C (the sublimation temperature of silicon monoxide SiO₂) at a pressure less than 10 times atmospheric pressure, of the mixture composed of doped silicon (Si) and quartz (SiO₂), makes it possible to obtain the gas containing silicon monoxide (SiO₂) according to the following reduction reaction:

[0145] SiO2 + Si 2 SiO?

[0146] Reducing the pressure in housing 111 of reaction chamber 1 to a value below atmospheric pressure makes it possible to limit the temperature required to initiate the chemical reduction reaction of quartz.

[0147] The gas containing silicon monoxide (SiO) is then condensed to form crystals of amorphous silicon-based material SiOx.

[0148] 3.2. Condensation stage

[0149] The condensation step 300 can be carried out in the condensation chamber 2 of the apparatus described above. To do this, the gas from the reaction chamber 1 is conveyed to the condensation chamber 2.

[0150] The condensation step 300 allows the gas containing silicon monoxide (SiO) to be condensed. During the condensation step, the silicon monoxide (SiO) restructures by disproportionation, to form the amorphous silicon-based material SiOx:

[0151] 2SiO → SiO2 + Si.

[0152] The amorphous silicon-based material SiOx solidifies on the walls of the precipitation chamber 21. This solidification yields crystals of the amorphous silicon-based material SiOx. These crystals are collected in the extraction nozzle 24.

[0153] The amorphous silicon-based SiOx material crystals can then be ground to a desired particle size to obtain the G1 grains of SiOx.

[0154] The reader will appreciate that the reaction and condensation steps can be carried out at a pressure lower than atmospheric pressure (for example under vacuum, in particular at a pressure of 10 Pascals), while the grinding, pre-carbonation, pre-lithiation, carbonation and fluorination steps can be carried out at atmospheric pressure.

[0155] 3.3. Grinding step

[0156] The grinding step 400 can be carried out in the grinding chamber 3 of the apparatus described above. Of course, the grinding step can be carried out in any other type of mechanical crusher known to those skilled in the art.

[0157] For use in the field of lithium-ion (Li-ion) battery anodes, SiOx grains with a size of 6 micrometers are generally used. Each SiOx grain (Si+SiO2) comprises silicon (Si) particles embedded in a silicon dioxide (SiO2) matrix.

[0158] The grinding step 400 reduces the crystals into G1 grains of micrometric and submicron sizes, between 0.5 and 20 pm, for example to sizes less than 10 pm and preferably less than 5 pm.

[0159] The grinding step is known to those skilled in the art. Indeed, the fluidized bed grinding technique is described in particular in document WO 2012 / 014985. Therefore, this step will not be described in further detail hereafter.

[0160] The crushed crystals thus produced are moved to a classification device in which an upward airflow circulates. Grains larger than a threshold value (for example, 15 pm, 10 pm, or 5 pm in the preferred case) are rejected, and G1 grains smaller than 10 pm (preferably smaller than 5 pm) are collected for transfer: • to the pre-carbonation chamber when the process includes the pre-carbonation step, or • to the pre-lithiation chamber when the process does not include the pre-carbonation step.

[0161] 3.4. Pre-carbonation step

[0162] As previously stated, the pre-carbonation step 500 is optional and can be implemented in the pre-carbonation chamber 4 of the apparatus described in point 2.

[0163] The pre-carbonation step 500 coats the G1 grains with a layer of carbon to obtain G2 grains of pre-carbonized silicon-based amorphous material (SiOx). This coating improves the electrical conductivity of the G2 grains.

[0164] Preferably, the pre-carbonation step 500 consists of chemical vapor deposition (CVD) of the carbon layer onto the Gl grains. This makes it possible to obtain higher-quality pre-carbonized silicon-based amorphous SiOx-based amorphous material grains G2 by limiting the problems of: • agglomeration of the grains together, and • irregular deposition of the carbon layer on the grains.

[0165] Chemical vapor deposition (CVD) is carried out at atmospheric pressure and a temperature of approximately 900°C. A gas containing various precursors is injected into the pre-carbonation chamber containing the Gl grains to be treated. This gas can be composed of a mixture of acetylene (C2H2) and nitrogen (N2), or a mixture of acetylene (C2H2) and argon (Ar). Such a mixture (C2H2+N2 or C2H2+Ar) allows the formation of an amorphous and partially porous carbon layer (which is preferable for the subsequent prelithiation step).

[0166] Advantageously, methanol (CH3OH) can be added to the mixture forming the gas injected into the pre-carbonation chamber. This makes it possible to reduce the temperature required to carry out the pre-carbonation step, the chemical reaction of which is as follows: T>800°C C2W2-----> 2C i +H2 î

[0167] The pre-carbonation step lasts approximately 4 hours. This allows a 15 nm thick layer of carbon to be deposited on the surface of the amorphous silicon-based SiOx material grains.

[0168] The pre-carbonation step 500 makes it possible to obtain G2 grains of pre-carbonized silicon-based amorphous material SiOx, each including a porous carbon layer with a thickness of 15nm.

[0169] The G2 grains thus obtained are then transferred to the prelithiation chamber for the implementation of the prelithiation step

[0170] 3.5. Prelithiation stage

[0171] The prelithiation step 600 can be implemented in the prelithiation chamber 5 of the apparatus described above.

[0172] The principle of prelithiation consists of adding lithium in advance to the grains of material suitable for manufacturing lithium-ion battery anodes. This makes it possible to compensate for the loss of lithium occurring during the first charge / discharge cycles of lithium-ion batteries.

[0173] Thus the prelithiation step makes it possible to improve the coulombic efficiency and the cyclability of lithium-ion batteries using the electrode material obtained from the process and device according to the invention.

[0174] In the embodiment illustrated in [Fig.7], the prelithiation step is carried out in the solid phase. Indeed, to allow lithium doping of the G2 grains from the pre-carbonation chamber (or of the G1 grains from the grinding chamber in the case where the pre-carbonation step is not implemented), a powder of a micrometric solid Lithium precursor is mixed with the G2 (or Gl) grains of pre-carbonized (or non-pre-carbonized) amorphous silicon-based SiOx material.

[0175] Thus, the prelithiation step includes a substep consisting of mixing the grains (G1 or G2) with: • Stabilized lithium powder (Listab), the quantity of lithium powder representing between 5 and 15% (and preferably 8%) by weight of the mixture, said powder having a particle size of 50 µm, or with • Lithium hydride (LiH) powder, the quantity of lithium hydride powder representing between 5 and 15% (and preferably 9%) by weight of the mixture, said powder having a particle size of 50 µm, or with • Lithium carbonate powder (Li2CO3), the quantity of lithium carbonate powder representing between 5 and 15% (and preferably 9%) by weight of the mixture, said powder having a particle size of 50 µm.

[0176] Advantageously, the mixing substep is carried out under inerting (injection of argon (Ar) or nitrogen (N2) gas).

[0177] The prelithiation step also includes a substep consisting of heating the mixture to a temperature of 800°C to initiate a reaction between liquid lithium and the SiO2 matrix of the grains (G1 or G2) of amorphous SiOx-based material. This reaction induces the transformation of the SiO2 matrix into a lithium silicate matrix (Li2SiO3; Li4SiO5).

[0178] When the mixture contains lithium, the prelithiation reaction is as follows: T^600°C 3SiO2 + 4Li------* - 2Li2SiO3 + 2Si Tx600°C 4SiO2 + 4Li-----» = 2Li4SiO4 + 3Si

[0179] When the mixture contains lithium hydride, the prelithiation reaction is as follows: T^600°C 3SiO2 H - 4LiH------> = 2£i2^^3 4" 2SÎ+ 2 / ^2 î T«600°C 4SïO2 + 4LiH-----> = 2Li4SiO4 4-

[0180] When the powder contains lithium carbonate, the prelithiation reaction is as follows: T~800°C 4SîO2 + Li2CO3-----» = 2Li4SiO4 + 3Si

[0181] The prelithiation step allows the G3 grains of prelithified silicon-based SiOx material to be obtained. These G3 grains are transferred to the carbonation chamber 6 for the implementation of the carbonation step 700.

[0182] 3.6. Carbonation stage

[0183] The carbonation step 700 can be carried out in the carbonation chamber 6 of the apparatus described above. As with the pre-carbonation step, the carbonation step consists of depositing a layer of carbon on the surface of the grains. This carbon layer has a dual role: • On the one hand, it reduces the undesirable effects associated with volumetric expansion by "confining" the SiOx grains within a shell, • on the other hand, it improves the electrical conductivity of the SiOx grains, which facilitates the transfer of lithium ions during the charge / discharge cycles of lithium-ion batteries whose electrodes (in particular the anode) are made from the material according to the invention.

[0184] The carbonation step is substantially identical to the pre-carbonation step, only the durations of these two steps being different (duration of the carbonation step between 4 and 10 hours, preferably between 5 and 8 hours, and even more preferably around 6 hours).

[0185] It allows the deposition of a carbon layer with a thickness between 20 and 30 nm on the G3 grains. This yields the G4 grains of prelithiated and carbonized silicon-based SiOx material. These G4 grains exhibit excellent performance in both cycling and speed performance tests.

[0186] The presence of carbon (compared to "naked" SiOx) changes the nature of the solid electrolyte interphase (SEI) of anodes made from this material. In the case of anodes made from G4 grains, the SEI is close to that of graphite (a very electrochemically stable material).

[0187] Furthermore, the presence of a layer of (or a coating of) Carbon makes it possible to limit the spraying phenomena observed on pure and micrometric Silicon particles.

[0188] 3.7. Fluoridation stage

[0189] As indicated above, the fluorination step 800 is optional and can be implemented in the fluorination chamber 7 of the apparatus described above.

[0190] It allows fluorinated radicals to be attached to the surface of the carbon layer of each grain. This surface modification limits the phenomenon of electrolyte decomposition on the surface of the anodes made from the material according to the invention.

[0191] Preferably, the fluorination step 800 is carried out at atmospheric pressure and at a temperature of around 600°C. A gas containing various precursors is injected into the pre-carbonation chamber containing the grains G1 to be treated. This gas may be composed of a mixture of tetrafluoromethane (CF4) and argon (Ar).

[0192] Following the fluorination step, prelithiated, carbon- and fluorinated silicon-based SiOx grains G5 are obtained. These G5 grains – illustrated in [Fig. 2] – comprise silicon particles P embedded in a lithium silicate matrix M' (Li2SiO3; Li4SiO5) embedded in a carbon layer C on which fluorinated particles F are arranged.

[0193] These grains can be used for the manufacture of anodes, in order to produce lithium-ion batteries with better properties than existing lithium-ion batteries.

[0194] 4. Conclusions

[0195] The main disadvantages of silicon Li-ion battery anodes concern: • their manufacturing cost, and • their resistance to cycling.

[0196]

[0197] The process described above provides a solution to both of these problems. The reader will have understood that many modifications can be made to the invention described above without materially departing from the new lessons and advantages described here.

Claims

Demands

1. A method for manufacturing an electrode material for lithium-ion batteries, the method comprising: • a step of introducing (100) a mixture of Quartz (SiO2) and Silicon (Si) into a reaction chamber (1), • a reaction step (200) of the mixture in the reaction chamber (1), by heating to a silicon sublimation temperature and at a pressure lower than atmospheric pressure, to form a gas including silicon monoxide (SiO), • a condensation step (300), in a condensation chamber (2), of the gas including silicon monoxide (SiO) to form crystals of amorphous silicon-based material SiOx, characterized in that the process further comprises the following steps: a grinding step (400), in a grinding chamber (3), of crystals of silicon-based amorphous material SiOx to obtain grains (Gl) of silicon-based amorphous material SiOx having a particle size of less than 10 pm, each grain (Gl) comprising silicon particles (P) included in a silicon dioxide matrix (M), a prelithiation step (600), in a prelithiation chamber (5), of grains (Gl, G2) to obtain grains (G3) of prelithified silicon-based amorphous material SiOx, each grain (G3) comprising prelithified silicon particles (P') included in a lithium silicate matrix (M'), a carbonation step (700), in a carbonation chamber (6), to grow a carbon layer on the grains (G3) of prelithiated silicon-based amorphous SiOx material in order to obtain grains (G4) of prelithiated and carbonized silicon-based amorphous SiOx material, each grain (G4) comprising the particles (P') of prelithiated silicon included in the (M') lithium silicate matrix and a carbon layer covering the (M') lithium silicate matrix.

2. A process according to claim 1, wherein for the reaction step (200): • the temperature is between 1200°C and 1400°C, and • the pressure is one thousand to ten thousand times lower than atmospheric pressure, in particular substantially equal to 10 Pascals).

3. A process according to any one of claims 1 or 2, wherein the prelithiation step (600) is carried out prior to or subsequent to the carbonation step (700).

4. A method according to any one of claims 1 to 3, wherein the prelithiation step (600) is carried out in the solid phase, said prelithiation step including the substeps of: • mixing, in a mixer (51) of the prelithiation chamber (5), the grains (G1, G2) of amorphous silicon-based SiOx material with a precursor powder to obtain a mixture: • the precursor being selected from lithium, lithium hydride, or lithium carbonate, • the quantity of precursor being less than 20% by weight of the mixture, preferably less than 15% by weight of the mixture, and even more preferably less than 10% by weight of the mixture, • injecting an inerting gas, said inerting gas including argon (Ar) and / or nitrogen (N2), • heating, at atmospheric pressure, in a rotary kiln (52) of the prelithiation chamber (5), the mixture to a temperature below 1000°C,preferably at a temperature below 900°C, and even more preferably approximately equal to 800°C, to obtain the grains (G3) of amorphous material based on prelithified silicon SiOx.

5. A method according to any one of claims 1 to 4, wherein the carbonation step (700) is carried out in the carbonation vapor deposition (CVD) phase, said carbonation step including the substeps of: • introducing the grains (G3) of prelithified silicon-based amorphous SiOx material into a rotary furnace of the carbonation chamber (6), • injecting, into the rotary furnace of the carbonation chamber (6), a gas containing: • acetylene (C2H2) and nitrogen (N2), or • acetylene (C2H2) and argon (Ar), • heating the grains (G3) and the gas, at atmospheric pressure, in the rotary furnace of the carbonation chamber (6), to a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains (G4) of material amorphous silicon-based prelithiated and carbonized SiOx.

6. A process according to claim 5, wherein the carbonation step (700) further comprises a substep consisting of injecting, into the rotary kiln of the carbonation chamber (6), a gas containing methanol (CH3OH).

7. A method according to any one of claims 1 to 6, further comprising a pre-carbonation step (500), in a pre-carbonation chamber (4), for growing a porous layer of carbon on the grains (G1) of silicon-based amorphous SiOx material, said pre-carbonation step being carried out prior to the pre-lithiation step (600) and enabling the production of grains (G2) of pre-carbonized silicon-based amorphous SiOx material, each grain (G2) comprising the pre-lithiated silicon particles (P') included in the silicon dioxide matrix (M), and a porous layer of carbon covering the silicon dioxide matrix (M).

8. A process according to claim 7, wherein the precarbonation step (500) includes the substeps of: • introduce the grains (Gl) of silicon-based amorphous material SiOx into a rotary furnace of the pre-carbonation chamber (4), • inject, into the rotary furnace of the pre-carbonation chamber (4), a gas containing: • acetylene (C2H2), methanol (CH30H) and nitrogen (N2), or • acetylene (C2H2), methanol (CH3OH) and argon (Ar), • heat the grains (Gl) and the gas, at atmospheric pressure, in the rotary furnace of the pre-carbonation chamber (4), to a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains (G2) of pre-carbonized silicon-based amorphous material SiOx.

9. A method according to any one of claims 1 to 6, further comprising a fluorination step (800) of prelithiated and carbonized silicon-based amorphous SiOx material grains (G4) in a fluorination chamber, to obtain prelithiated, carbonized and fluorinated silicon-based amorphous SiOx material grains (G5), each grain (G5) comprising prelithiated silicon particles (P') included in the lithium silicate matrix (M'), the carbon layer covering the lithium silicate matrix (M'), and fluorine particles on a surface of the carbon layer.

10. Apparatus for manufacturing an electrode material for lithium-ion batteries, said apparatus comprising: • a reaction chamber (1) including a heating system (113) for forming a gas including silicon monoxide (SiO) by heating a mixture of Quartz (SiO2) and Silicon (Si), at a silicon sublimation temperature and at a pressure lower than atmospheric pressure, • a condensation chamber (2) for condensing the gas including silicon monoxide and forming crystals of amorphous silicon-based material SiOx,

11. characterized in that the device further comprises: • a grinding chamber (3) for grinding the crystals of amorphous silicon-based material SiOx to obtain grains (Gl) of amorphous silicon-based material SiOx having a particle size of less than 10 pm, each grain (Gl) comprising silicon particles (P) included in a silicon dioxide matrix (M), • a prelithiation chamber (5) downstream of the grinding chamber (3), to add lithium to the grains (G1, G2) in order to obtain grains (G3) of prelithified silicon-based amorphous material SiOx, each grain (G3) comprising the particles (P') of pelithified silicon included in a matrix (M') of lithium silicate, • a carbonation chamber (6) downstream of the prelithiation chamber (3), to grow a layer of carbon on the grains (G3) of prelithified silicon-based amorphous material SiOx in order to obtain grains (G4) of prelithified and carbonized silicon-based amorphous material SiOx, each grain (G4) comprising the pelithified silicon particles (P') included in the lithium silicate matrix (M') and a layer of carbon covering the lithium silicate matrix (M'). A manufacturing apparatus according to claim 10, in which the prelithiation chamber (5) comprises: • a mixer (51) for mixing the grains (Gl, G2) of amorphous silicon-based SiOx material with a precursor powder to obtain a mixture: • the precursor being chosen from lithium, lithium hydride or lithium carbonate, • the quantity of precursor being less than 20% by weight of the mixture, preferably less than 15% by weight of the mixture, and even more preferably less than 10% by weight of the mixture, • a rotary kiln (52) for heating the mixture, at atmospheric pressure, to a temperature below 1000°C, preferably to a temperature below 900°C, and even more preferably approximately equal to 800°C, to obtain the grains (G3) of amorphous material based on prelithified silicon SiOx.

12. A manufacturing apparatus according to any one of claims 10 or 11, wherein the carbonation chamber (6) comprises a rotary furnace for heating the grains (G3) of prelithified silicon SiOx amorphous material with a gas containing: • acetylene (C2H2) and nitrogen (N2), or • acetylene (C2H2) and argon (Ar), • at a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain the grains (G4) of prelithified and carbonized silicon SiOx amorphous material.

13. A manufacturing apparatus according to any one of claims 10 to 12, further comprising a pre-carbonization chamber (4) including a rotary oven for heating grains (G1) and a gas containing: • acetylene (C2H2), methanol (CH3OH) and nitrogen (N2), or • acetylene (C2H2), methanol (CH3OH) and argon (Ar), • at a temperature below 1100°C, preferably below 1000°C, and even more preferably substantially equal to 900°C, to obtain grains (G2) of pre-carbonized silicon-based amorphous SiOx material.

14. A manufacturing apparatus according to any one of claims 10 to 13, further comprising a fluorination chamber (7) for grains (G4) of prelithiated and carbonized silicon-based amorphous material SiOx, to obtain grains (G5) of prelithiated, carbonized and fluorinated silicon-based amorphous material SiOx, each grain (G5) comprising silicon particles (P) included in the lithium silicate matrix (M'), the carbon layer covering the lithium silicate matrix (M'), and fluorine particles on a surface of the carbon layer.

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