Powder for use in a negative electrode of a battery and a battery comprising such a powder

Abstract

The present invention discloses a powder for use in a negative electrode of a battery, the powder comprising a mixture of the following materials: a first fraction by number of particles, the first fraction by number of particles comprising a carbonaceous matrix material and silicon-based particles dispersed therein; and a second fraction by number of particles, the second fraction by number of particles comprising Si-free carbonaceous particles containing graphitic domains having an average size of at least 10 nm and at most 45 nm, as determined by the Scherr formula applied to an X-ray diffraction peak of the powder attributable to C(002), the peak being at a 2θ angle between 26° and 27°. Cu IC has the maximum intensity.

Description

Technical Field

[0001] The present invention relates to powders for use in negative electrodes of batteries and batteries comprising such powders. Background Art

[0002] Lithium-ion (Li-ion) batteries are currently the best performing batteries and have become the standard for portable electronic devices. Furthermore, these batteries have penetrated other industries, such as automotive and electrical storage, and are experiencing rapid growth. Their advantages are high energy density combined with good power performance.

[0003] Li-ion batteries typically contain a plurality of so-called Li-ion cells, which in turn contain a positive electrode (also called cathode), a negative electrode (also called anode), and a separator immersed in an electrolyte. The most common Li-ion cells for portable applications are developed using electrochemically active materials such as lithium cobalt oxide or lithium cobalt nickel manganese oxide as cathode and natural or artificial graphite as anode.

[0004] It is known that one of the important limiting factors affecting battery performance and in particular battery energy density is the active material in the anode. Therefore, in order to improve energy density, the use of electrochemically active materials containing silicon in the negative electrode has been studied in the past few years.

[0005] In the art, the performance of batteries containing Si-based electrochemically active powders is typically quantified by the so-called cycle life of the full cell, which is defined as the number of times, or cycles, a battery cell containing such material can be charged and discharged before reaching 80% of its initial discharge capacity. Consequently, most work on Si-based electrochemically active powders has focused on improving cycle life.

[0006] A disadvantage of using silicon-based electrochemically active materials in anodes is their large volume expansion during charging, which can be as high as 300% when lithium ions are fully incorporated into the anode's active material (e.g., by alloying or intercalation), a process commonly referred to as lithiation. The large volume expansion of silicon-based materials during lithium incorporation can induce stresses in the silicon-based particles, which in turn can lead to mechanical degradation of the silicon material. During the cyclical charging and discharging of Li-ion batteries, the repeated mechanical degradation of silicon-based electrochemically active materials can reduce the battery's life to unacceptable levels.

[0007] Another negative side effect associated with silicon is the potential formation of a thick SEI (solid electrolyte interface) on the anode. The SEI is a complex reaction product between the electrolyte and lithium, which leads to the loss of lithium available for electrochemical reactions, resulting in poor cycling performance, that is, the loss of capacity with each charge-discharge cycle. A thick SEI can further increase the battery's resistance, thereby limiting its ability to charge and discharge at high currents.

[0008] In principle, SEI formation is a self-terminating process that stops once a "passivation layer" forms on the surface of the silicon-based material.

[0009] However, both the silicon-based particles and the SEI may be damaged during discharge (lithiation) and recharge (delithiation) due to the volume expansion of the silicon-based particles, thereby releasing new silicon surfaces and causing the initiation of new SEI formation.

[0010] To address these shortcomings, composite powders are often used. In these composite powders, nanoscale silicon-based particles are mixed with at least one component suitable for protecting the silicon-based particles from electrolyte decomposition and accommodating volume changes. Such a component can be a carbon-based material, preferably forming a matrix.

[0011] The composite powders usually additionally contain graphite particles in order to adjust their specific capacity to a practical level, which lies between 500 and 1500 mAh / g.

[0012] For example, such composite powders are mentioned in EP 3238296 B1, which discloses a mixture of particles comprising silicon domains embedded in a matrix and graphite particles not embedded in the matrix. In EP 2523241 A1, a powder comprising a carbon-containing core having an amorphous carbon layer continuously formed on its surface and metal particles is disclosed. X. Yang et al. (ECS Solid State Letters, 1 (2) M5-M7 (2012)) disclose a powder comprising a mixture of nano-sized Si particles dispersed in a carbon matrix consisting of graphite flakes and pyrolytic carbon. In WO 2019 / 218503 A1, a composite carbon material having nano-silicon dispersed therein is disclosed, wherein the composite carbon material comprises a graphite crystalline phase and an amorphous carbon phase. In US2020 / 006753 Al, an electrode comprising a nano-silicon-containing substance, multilayer graphene, a graphite material and a binder is disclosed. In US 2016 / 043384 Al, an anode layer composition is disclosed in which an anode active material (such as silicon) resides in the pores of a solid graphene foam.

[0013] Despite the use of such composite powders, there is still room for improvement in the performance of batteries containing Si-based electrochemically active powders. Specifically, existing composite powders, once used in batteries, do not allow for achieving both long cycle life and high rate performance, such as for fast-charging electric vehicles.

[0014] The object of the present invention is to provide a stable electrochemically active powder comprising a mixture of silicon-based particles and graphite particles which is advantageous once used in negative electrodes in Li-ion batteries since it allows achieving a long cycle life coupled with a high rate capability. Summary of the Invention

[0015] This object is achieved by providing a powder according to embodiment 1 which, once used in an anode of a Li-ion battery, allows achieving a long cycle life and high rate capability, as demonstrated in Examples 1 to 3 compared with Counter Examples 1 to 3.

[0016] The present invention relates to the following embodiments:

[0017] Implementation Plan 1

[0018] In a first aspect, the present invention relates to a powder suitable for use in a negative electrode of a battery, the powder comprising a mixture of:

[0019] a first fraction, by number, of particles comprising a carbonaceous matrix material and silicon-based particles dispersed in the carbonaceous matrix material, and

[0020] a second fraction, based on number, of particles comprising Si-free carbon-containing particles comprising graphitic domains,

[0021] The powder is characterized by:

[0022] - the graphite domains contained in the Si-free carbonaceous particles have an average size of at least 10 nm and at most 45 nm, as determined by the Scherrer formula applied to the powder's X-ray diffraction peak attributable to C(002), the X-ray diffraction peak being at a 2θ angle between 26° and 27°. Cu has the maximum intensity Ic, and

[0023] The particles comprising a carbon-containing matrix material and silicon-based particles dispersed in the carbon-containing matrix material do not contain graphitic domains having a size greater than 5 nm, preferably do not contain graphitic domains having a size greater than 2 nm.

[0024] A powder suitable for use in a negative electrode of a battery refers to an electrochemically active powder comprising electrochemically active particles capable of storing and releasing lithium ions during lithiation and delithiation, respectively, of the negative electrode of the battery. Such a powder may equivalently be referred to as an "active powder."

[0025] A mixture of a first fraction and a second fraction means that the powder comprises a mixture of two types of particles, the particles from the first fraction being different from the particles from the second fraction. Both fractions are different from zero.

[0026] Furthermore, in the powder according to the present invention, particles from one fraction cannot be contained within particles from the other fraction. Specifically, Si-free carbonaceous particles comprising graphite domains having an average size of at least 10 nm and at most 45 nm cannot be present within particles comprising a carbonaceous matrix material. However, some contact between particles from the two fractions may exist, located at their outer surfaces. This is even preferred to ensure good electronic conductivity of the powder, and thus high-rate capability of batteries containing the powder.

[0027] Number-based particle fraction refers to a particle fraction based on a visual analysis of a minimum number of particles present in a powder, with or without the aid of an image analysis program. This minimum number of particles is at least 100 particles. An example of determining number-based particle fraction is provided in the "Analytical Methods" section.

[0028] The silicon-based particles can have any shape, such as substantially spherical, but can also be irregularly shaped, rod-shaped, plate-shaped, and the like.

[0029] In silicon-based particles, the silicon is mostly present in the form of silicon metal, to which small amounts of other elements may have been added to improve properties, or may contain some impurities such as oxygen or trace metals.

[0030] The average silicon content in such silicon-based particles is preferably 80% by weight or more, and more preferably 90% by weight or more, relative to the total weight of the silicon-based particles, when all elements except oxygen are taken into account.

[0031] The silicon-based particles dispersed in the matrix material means that the silicon-based particles form agglomerates with a size of less than 1 μm or do not form agglomerates at all and are mostly, preferably completely, covered by the matrix material. Therefore, in the powder according to embodiment 1, the silicon-based particles are preferably only in contact with each other and / or with the matrix material.

[0032] For example, the presence of Si in the particles can be determined based on scanning electron microscopy and energy dispersive X-ray (SEM-EDX) analysis of powder cross sections. Since involuntary contamination can never be excluded, Si-free particles are understood here to be particles with a Si content of less than 0.5 atomic %.

[0033] For example, the presence of graphitic domains with a size greater than 5 nm, preferably greater than 2 nm, in the particles can be determined based on transmission electron microscopy (TEM) analysis. Examples of such analyses are provided in the "Analytical Methods" section.

[0034] Even amorphous carbonaceous matrix materials may contain very small graphite domains, with dimensions less than 5 nm, preferably less than 2 nm. A powder comprising particles comprising a matrix material with silicon-based particles dispersed therein and such very small graphite domains is not excluded as part of the present invention.

[0035] Furthermore, the presence of graphitic domains having a size greater than 5 nanometers, preferably greater than 2 nanometers, in 1% or less of the number of particles in a representative sample of at least 100 particles comprising a carbonaceous matrix material and silicon-based particles dispersed therein included in the powder would be considered incidental and does not exclude such powders from being part of the present invention.

[0036] It should be noted that the carbon-containing matrix comprising the silicon-based particles is amorphous, and thus the C(002) peak observed in the X-ray diffraction pattern of the powder can be attributed only to the Si-free carbon-containing particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm. If some or even all of the particles comprising the carbon-containing matrix material and the silicon-based particles dispersed therein also include graphitic domains having a size of less than 5 nm, preferably less than 2 nm, the contribution of the latter to the C(002) peak observed in the X-ray diffraction pattern of the powder is considered to be negligible in terms of both intensity and FWHM.

[0037] For the avoidance of doubt, it will be understood that in this document the word "silicon" refers to the element Si in its metallic (zero valent) state, whereas the symbol "Si" refers to the element silicon regardless of its oxidation state.

[0038] As is known to all, the Scherrer formula (P. Scherrer, Göttingen News ( Nachrichten)》2,98(1918)) is a formula for calculating the size of ordered (crystalline) domains from X-ray diffraction data. To avoid machine-to-machine variations, calibration can be performed using standardized samples.

[0039] By applying the Scherrer equation, graphitic domains with an average size of at least 10 nm and at most 45 nm are equivalent to a C(002) peak in X-ray diffraction (XRD) with a peak of at least 0.26° (2θ Cu ) and at most 0.89°(2θ Cu ) full width at half maximum (FWHM).

[0040] The Si-free carbon-containing particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm are distinct from the particles of the matrix material comprising silicon-based particles, and a mixture of these two different types of particles is advantageous for two reasons:

[0041] - the Si-free carbonaceous particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm ensure good electronic contact between the particles comprising the matrix material and the silicon-based particles dispersed therein, resulting in a high electronic conductivity of the powder, and

[0042] - Si-free carbonaceous particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm act as spacers between the particles comprising the matrix material and the silicon-based particles dispersed therein, thereby avoiding agglomeration of the latter which would lead to high volume expansion, cracks in the anode, reduced battery cycle life and low rate performance.

[0043] Graphitic materials consist of graphene planes or sheets that are more or less well-ordered perpendicular to the graphite planes along a certain direction (usually the c-direction, hence the use of the 002 peak in XRD). The size of a graphitic domain is understood to be the average distance perpendicular to the graphene planes over which the graphene planes are well-ordered, i.e., over which the graphitic order is maintained.

[0044] When the graphite domains included in the Si-free carbon-containing particles are larger than 45 nm, the graphene planes are well-ordered, the Si-free carbon-containing particles are highly crystalline, and their specific surface area (BET) is low. This reduces the ability of the Si-free carbon-containing particles to act as spacers between the particles comprising the matrix material and the silicon-based particles dispersed therein, and to prevent the latter from agglomerating, which has the negative consequences previously disclosed. Graphite is an example of a carbon-containing material having graphite domains larger than 45 nm.

[0045] When the graphite domains included in Si-free carbonaceous particles are smaller than 10 nm, the graphene planes are largely disordered, the Si-free carbonaceous particles have low crystallinity, and their specific surface area (BET) is high. This increases the surface area for reaction with the electrolyte and thereby enhances the formation of the SEI layer, thereby increasing the initial irreversible capacity loss of batteries containing such powders beyond the generally accepted range. Pure graphene powder is an example of a carbonaceous material having graphite domains smaller than 10 nm.

[0046] In the powder according to the invention, the sum of the first fraction of particles based on number and the second fraction of particles based on number cannot exceed 1. In case the powder comprises particles of more than two fractions, this sum may be lower than 1.

[0047] Implementation Plan 2

[0048] In a second embodiment according to embodiment 1, the average size of the graphite domains included in the Si-free carbon-containing particles is at least 12 nm and at most 39 nm.

[0049] Implementation Plan 3

[0050] In a third embodiment according to embodiment 1 or 2, the powder, when analyzed by X-ray diffraction (XRD), has an XRD diffraction pattern having a peak assigned to C(002) at a 2θ between 26° and 27°. Cu and a peak attributable to Si(lll) at 2θ between 28° and 29° Cu The maximum intensity Is is located at the position where the ratio Ic / Is is greater than or equal to 0.2 and less than or equal to 2.0, preferably less than or equal to 1.5, more preferably less than or equal to 1.0.

[0051] When the ratio I c / I s Above 2.0, preferably above 1.5, more preferably above 1.0, the graphene planes are well ordered, the Si-free carbonaceous particles comprising graphitic domains are highly crystalline and their specific surface area (BET) is low, which may reduce their ability to act as spacers. This is unfavorable for the reasons given previously.

[0052] When the ratio I c / I s Below 0.2, the graphene planes are mostly disordered, the Si-free carbonaceous particles comprising graphitic domains have low crystallinity and their specific surface area (BET) is high. This is disadvantageous for the reasons given previously.

[0053] Implementation Plan 4

[0054] In a fourth embodiment according to any of embodiments 1 to 3, the Si-free carbonaceous particles comprising graphite are characterized by a number-based size distribution with a d50 less than or equal to 25 μm and greater than or equal to 6 μm, preferably greater than or equal to 8 μm.

[0055] The number-based size distribution is based on a visual analysis of the minimum number of Si-free carbon-containing particles including graphitic domains in the powder, with or without the aid of an image analysis program. This minimum number of Si-free carbon-containing particles including graphitic domains is at least 100 particles. An example of determining the number-based particle fraction is provided in the "Analytical Methods" section.

[0056] Si-free carbon-containing particles including graphite domains having a number-based size distribution with a d50 of less than 6 μm, preferably less than 8 μm, may have an extremely high specific surface area and thus increase the reaction surface with the electrolyte, which is disadvantageous for the reasons explained above. Si-free carbon-containing particles including graphite domains having a number-based size distribution with a d50 of greater than 25 μm may not ensure good electronic contact between the particles including the matrix material and the silicon-based particles dispersed therein, thereby resulting in reduced electronic conductivity of the powder and reduced rate performance of batteries including such powders.

[0057] Implementation Plan 5

[0058] In a fifth embodiment according to any one of embodiments 1 to 4, the Si-free carbon-containing particles comprising graphite domains are made of at least one of the following materials: exfoliated graphite, expanded graphite, graphene nanoplatelets.

[0059] Graphite is a three-dimensional material consisting of large stacks of graphene sheets or planes that are ordered perpendicular to the graphene sheets. The average distance that keeps graphite ordered is large (>45 nm). Therefore, graphite is not suitable as a Si-free carbon-containing particle that includes graphite domains with an average size of at least 10 nm and at most 45 nm.

[0060] Exfoliated or expanded graphite is graphite embedded with a substance (e.g., sulfuric acid) that is subsequently evaporated, causing a sudden increase in the interlayer distances between the graphene sheets. This results in a partial disordering of the graphene sheets and, consequently, a reduction in the stacking size of the graphene sheets and graphitic domains (<45 nm).

[0061] Graphene nanosheets are nanoparticles composed of small stacked graphene flakes that have the same shape as those found in the walls of carbon nanotubes, but in a flat form. The stacked graphene flakes are in the same size range as exfoliated graphite.

[0062] Finally, complete exfoliation of graphite produces graphene, which consists of randomly ordered graphene flakes with little or no graphitic order and, therefore, small graphitic domains (<10 nm).

[0063] Figure 1 A schematic diagram of these different classes of materials is given in .

[0064] Implementation Plan 6

[0065] In a sixth embodiment according to any one of embodiments 1 to 5, the silicon-based particles are characterized by having a number-based size distribution with a d50 greater than or equal to 20 nm and less than or equal to 150 nm.

[0066] The number-based size distribution is based on a visual analysis of a minimum number of silicon-based particles contained in the powder, with or without the aid of an image analysis program. This minimum number of silicon-based particles is at least 100 particles. An example of determining the number-based particle fraction is provided in the "Analytical Methods" section.

[0067] Silicon-based particles having a number-based size distribution with a d50 below 20 nm are very difficult to disperse effectively in a matrix material, which can reduce the electronic conductivity of the powder.

[0068] Silicon-based particles having a number-based size distribution with a d50 greater than 150 nm suffer more cracking during lithiation, resulting in a significant reduction in the cycle life of batteries containing such powders.

[0069] Implementation Plan 7

[0070] In a seventh embodiment according to any one of embodiments 1 to 6, the powder has a silicon content C expressed as a weight percentage (wt %), wherein 10 wt % ≤ C ≤ 60 wt %.

[0071] Implementation Plan 8

[0072] In an eighth embodiment according to any one of embodiments 1 to 7, the powder has a silicon content C and an oxygen content D, both expressed in weight percent (wt%), wherein D≦0.15C.

[0073] Too high an oxygen content can lead to an additional irreversible loss of lithium by forming lithium oxide (Li2O) during the first lithiation of the powder, thereby increasing the initial irreversible capacity loss of batteries containing such powders.

[0074] Implementation Plan 9

[0075] In a ninth embodiment according to any one of embodiments 1 to 8, the first fraction based on number of particles is at least 0.2 and at most 0.8 relative to a minimum number of 100 particles included in the powder.

[0076] In other words, 20% to 80% of the at least 100 particles observed in the powder are particles comprising the matrix material with the silicon-based particles dispersed therein.

[0077] Implementation Plan 10

[0078] In a tenth embodiment according to any one of embodiments 1 to 9, the second fraction based on number of particles is at least 0.2 and at most 0.8 relative to a minimum number of 100 particles included in the powder.

[0079] In other words, 20% to 80% of the at least 100 particles observed in the powder are Si-free carbonaceous particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm, as determined by the Scherrer equation applied to the powder's X-ray diffraction peak assigned to C(002), which peak is at a 2θ angle between 26° and 27°. Cu It has the maximum intensity Ic.

[0080] Implementation Plan 11

[0081] In an eleventh embodiment according to any one of embodiments 1 to 10, the powder comprises pores. The pores may be located in Si-free carbon-containing particles comprising graphitic domains and / or in particles comprising a matrix material with silicon-based particles dispersed therein.

[0082] The pores may be beneficial because the pores may buffer the volume expansion of the powder particles during the latter lithiation / delithiation, thereby reducing stress induction and cracks that may occur in the powder particles, thereby increasing the cycle life.

[0083] The pores can be observed by SEM analysis of a cross section of the powder.

[0084] Implementation Plan 12

[0085] In a twelfth embodiment according to any one of embodiments 1 to 11, the powder includes particles having a volume-based particle size distribution, wherein the volume-based particle size distribution has D10, D50 and D90, wherein 1 μm≤D10≤10 μm, 8 μm≤D50≤25 μm and 10 μm≤D90≤40 μm.

[0086] Implementation Plan 13

[0087] In a thirteenth embodiment according to any one of embodiments 1 to 12, the powder has a maximum of 10 m 2 / g, preferably at most 5m 2 / g of BET surface area.

[0088] It is important that the powders have a low BET surface area to reduce the surface of the electrochemically active particles in contact with the electrolyte in order to limit the formation of lithium-depleting solid electrolyte interfaces (SEIs) and, therefore, irreversible capacity loss in batteries containing such powders.

[0089] Implementation Plan 14

[0090] In a fourteenth embodiment according to any one of embodiments 1 to 13, the matrix material is a product of thermal decomposition of at least one of the following materials: polyvinyl alcohol (PVA), polyvinyl chloride (PVC), sucrose, coal tar pitch, petroleum pitch, lignin, and resin.

[0091] The product of the thermal combination of at least one of these materials is amorphous carbon and therefore does not contribute to the C(002) peak observed in the X-ray diffraction pattern of the powder obtained during XRD analysis.

[0092] Implementation Plan 15

[0093] In a fifteenth embodiment, the present invention finally relates to a battery comprising the powder according to any one of embodiments 1 to 14. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 : Schematic representation of graphite domains in graphite (A), exfoliated / expanded graphite and graphene nanosheets (B), and graphene (C). dA, dB, and dC give an indication of the corresponding graphite domain sizes.

[0095] Figure 2 Schematic diagrams of powders according to Example 1 (A) to Counterexample 1 (B) and Counterexample 3 (C). 1: Si-free carbonaceous particle comprising graphite domains; 2: Particle comprising a matrix material and silicon-based particles dispersed therein; 3: Silicon-based particle. dA, dB, and dC provide an indication of the respective graphite domain sizes. DETAILED DESCRIPTION

[0096] In the following detailed description, preferred embodiments are described in detail for practicing the present invention. Although the present invention has been described with reference to these specific preferred embodiments, it should be understood that the present invention is not limited to these preferred embodiments. On the contrary, the present invention encompasses numerous alternatives, modifications, and equivalents, which will become apparent upon consideration of the following detailed description.

[0097] Analytical methods used

[0098] Determination of Si content

[0099] The Si content of the powders in the Examples and Counterexamples was measured by X-ray fluorescence (XRF) using an energy dispersive spectrometer. This method has an experimental random error of + / - 0.3 wt% Si.

[0100] Determination of oxygen content

[0101] The oxygen content of the powders in the Examples and Counterexamples was determined using a LECO TC600 oxygen and nitrogen analyzer using the following method. The powder sample was placed in a sealed tin container, which itself was placed in a nickel basket. The basket was then placed in a graphite crucible and heated to over 2000°C using helium as a carrier gas. This melted the sample, and oxygen reacted with the graphite in the crucible, forming CO or CO₂ gas. This gas was directed into an infrared measurement cell. The observed signal was recalculated as the oxygen content.

[0102] Determination of specific surface area (BET)

[0103] Specific surface area was measured using the Brunauer-Emmett-Teller (BET) method using a Micromeritics Tristar 3000. 2 g of the powder to be analyzed was first dried in an oven at 120°C for 2 hours, followed by a N2 purge. Prior to measurement, the powder was then degassed in a vacuum at 120°C for 1 hour to remove adsorbed species.

[0104] Determination of electrochemical properties

[0105] The electrochemical properties of the powders in Examples and Counterexamples were measured by the following methods.

[0106] The powder to be evaluated was sieved using a 45 μm sieve and mixed with carbon black, carbon fibers, and sodium carboxymethylcellulose binder in water (2.5 wt%). The ratio used was 89 parts active material powder / 1 part carbon black (C65) / 2 parts carbon fibers (VGCF) and 8 parts carboxymethylcellulose (CMC). These components were mixed in a Pulverisette 7 planetary ball mill at 250 rpm for 30 minutes.

[0107] Copper foil cleaned with ethanol was used as the current collector for the negative electrode. A 200 μm thick layer of the mixed components was coated on the copper foil. The coating was vacuum dried at 70°C for 45 minutes. A 13.86 cm thick sheet was punched out from the dried coated copper foil. 2 The rectangular electrodes were dried at 110 °C under vacuum overnight and used as negative electrodes in pouch cells.

[0108] The positive electrode was prepared as follows: commercial LiNi 3 / 5 Mn 1 / 5 Co 1 / 5 O2 (NMC 622) powder was mixed with a solution of carbon black (C65), carbon fiber (VGCF) and 8 wt% polyvinylidene fluoride (PVDF) binder in N-methyl-2-pyrrolidone (NMP). The ratio used was 92 parts by weight of commercial NMC 622 powder / 1 part by weight of carbon black / 3 parts by weight of carbon fiber and 4 parts by weight of PVDF. The components were mixed in a Pulverisette 7 planetary ball mill at 250 rpm for 30 minutes. Aluminum foil cleaned with ethanol was used as the current collector for the positive electrode. A layer of the mixed components was coated on the aluminum foil to a thickness that ensured a ratio of negative electrode capacity to positive electrode capacity of 1.1. The coating was vacuum dried at 70°C for 45 minutes. 11.02 cm thick pieces were punched out from the dried coated aluminum foil. 2 The rectangular electrodes were dried at 110 °C under vacuum overnight and used as the positive electrodes in pouch cells.

[0109] The electrolyte used was 1 M LiPF6 dissolved in EC / DEC solvent (1 / 1 volume) + 2 wt% VC + 10 wt% FEC additive.

[0110] The assembled pouch cells were then tested using the procedure described below, where the first cycle corresponds to conditioning of the cell, and where "CC" stands for "constant current" and "CCCV" stands for "constant current constant voltage."

[0111] Cycle 1 (Adjustment)

[0112] ο Charge at 0.025C CC until it reaches 15% of the theoretical battery capacity

[0113] οSet aside for 12 hours

[0114] Charge to 4.2V at 0.05C CC

[0115] ο Set aside for 5 minutes

[0116] οDischarge to 2.7V at 0.05C CC

[0117] Fast charging test cycle 2 (reference cycle)

[0118] ο Set aside for 5 minutes

[0119] ο Charge to 4.2V at 0.1C CC

[0120] ο Set aside for 5 minutes

[0121] οDischarge to 2.7V at 0.1C CC

[0122] Fast charging test cycle 3

[0123] ο Set aside for 5 minutes

[0124] ο Charge to 4.2V at 0.2C CC

[0125] ο Set aside for 5 minutes

[0126] οDischarge to 2.7V at 0.2C CC

[0127] Fast charge test cycles 4, 5, 6, 7 and 8

[0128] ο Set aside for 5 minutes

[0129] ο Charge to 4.2V at 0.5C (cycle 4) CC - 1C (cycle 5) CC - 2C (cycle 6) CC - 3C (cycle 7) CC - 5C (cycle 8) CC

[0130] ο Set aside for 5 minutes

[0131] οDischarged at 0.1C CC to 2.7V for all cycles

[0132] Starting from loop 9:

[0133] ο Set aside for 5 minutes

[0134] o Charge to 4.2V at 0.5C CC, then CV charge until C / 20

[0135] ο Set aside for 5 minutes

[0136] οDischarge to 2.7V at 0.5C CC

[0137] Here, rate performance is measured as the charge capacity at 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, and 5C rates, expressed as a percentage of the 0.1C rate. 0.1C corresponds to the current that theoretically allows the battery to be charged at a constant current for 10 hours. For example, 1C is 10 times the current of 0.1C and theoretically allows the battery to be charged for 1 hour.

[0138] The coulombic efficiency (CE) of a pouch cell calculated for the initial cycle is the ratio of the capacity during discharge to the capacity during charge at a given cycle. The initial cycle is the most important cycle in terms of coulombic efficiency because the reaction of SEI formation has a huge impact on CE.

[0139] Furthermore, it is well established that for commercial applications, a cycle life of at least 150 cycles is required in such pouch cells for anode materials with a specific capacity of about 1300 mAh / g. These high-capacity powders can be further diluted during negative electrode preparation, for example with graphite, to a capacity of 600 to 700 mAh / g to achieve a cycle life of more than 300 cycles.

[0140] Determination of the number-based particle fraction in powders

[0141] The number-based particle fraction in the powder is determined by electron microscopic analysis (SEM or TEM) of a cross section of the powder in combination with image analysis, preferably with the aid of an image analysis program.

[0142] To this end, a cross section of the powder to be analyzed is prepared according to the procedure described below, which includes a plurality of cross sections from two fractions of particles (i.e., a cross section of a particle comprising matrix material and silicon-based particles dispersed therein, and a cross section of a Si-free carbonaceous particle comprising graphitic domains). In this case, the size of a particle is considered to be equivalent to the maximum straight-line distance between two points on the perimeter of a discrete cross section of the particle, also referred to as d max .

[0143] In order to perform the analysis using the SEM equipment, the sample preparation was performed as follows. 500 mg of the powder to be analyzed were embedded in 7 g of resin (Buehler EpoxiCure 2), which consisted of a mixture of 4 parts of epoxy resin (20-3430-128) and 1 part of epoxy hardener (20-3432-032). The resulting 1 "diameter sample was dried during at least 8 hours. It was then first mechanically polished using a Struers Tegramin-30 until a maximum thickness of 5 mm was reached and then further polished by ion beam polishing (cross section polisher JeolSM-09010) at 6 kV for about 6 hours to obtain a polished surface. Finally, a carbon coating was applied to this polished surface by carbon sputtering for 12 seconds using a Cressington 208 carbon coater to obtain the sample to be analyzed by SEM, also called a "cross section".

[0144] Then, the EDS was measured using an Xflash 5030--127 (30 mm 2 The cross sections were analyzed using a FEG-SEM JSM-7600F from JEOL using a CMOS process (100 nm CMOS, 127 eV).

[0145] The signal from this detector was processed by a Quantax 800 EDS system from Bruker.

[0146] Amplification is generated by applying a voltage of 15 kV at a working distance of a few millimeters. An image of the backscattered electrons is recorded when the value is added to an image from an optical microscope.

[0147] In the case of TEM analysis, 10 mg of the powder to be analyzed was placed in a focused ion beam scanning electron microscope (FIB-SEM) instrument. A platinum layer was deposited on top of the surface of the active material powder. A thin slice of the active material powder was extracted using the FIB. This slice was further placed in a TEM sample holder and analyzed according to the following procedure.

[0148] For illustrative purposes in a non-limiting manner, a TEM-based procedure for determining the particle fraction in a powder based on number is provided below.

[0149] 1. Collect multiple TEM images of a cross section of a powder comprising two fractions of particles.

[0150] 2. Adjust the image contrast and brightness settings to facilitate observation of cross-sections of different types of particles: particles comprising matrix material with silicon-based particles dispersed therein, and Si-free carbonaceous particles comprising graphitic domains. Differences in brightness allow for easy differentiation of the different types of particles from the matrix due to their different chemical compositions.

[0151] 3. Using a suitable image analysis program, select from one or several acquired TEM images at least 100 discrete cross sections of the particle that do not overlap with another cross section of the particle. These discrete cross sections may be selected from one or more cross sections of a powder comprising the particle.

[0152] 4. For each of at least 100 selected discrete cross-sections of the particle, determine whether it is a cross-section of a particle comprising a carbon-containing matrix material and silicon-based particles dispersed therein, a cross-section of a Si-free carbon-containing particle comprising graphitic domains, or a cross-section of another type of particle. Then, finally, calculate the fraction of the particle comprising a carbon-containing matrix material and silicon-based particles dispersed therein and the fraction of the Si-free carbon-containing particle comprising graphitic domains.

[0153] Note that for each particle, the TEM analysis is described only after which it is possible to check whether the Si-free carbon-containing particles actually contain graphitic domains and to measure the size of the graphitic domains. Given that measuring the size of the graphitic domains for each particle would be very complex and laborious, it is sufficient to measure the average size of the graphitic domains for the entire powder sample by XRD analysis, as will be explained in detail in the next section, and to assume that all graphitic domains included in the Si-free carbon-containing particles have this average size. In this case, SEM analysis may be sufficient, which allows for distinguishing particles comprising carbon-containing matrix material and silicon-based particles dispersed therein from Si-free carbon-containing particles comprising graphitic domains.

[0154] Determination of number-based particle size distribution

[0155] The number-based particle size distribution of the silicon-based particles and / or the Si-free carbon-containing particles comprising graphite domains contained in the powder according to the invention is determined by electron microscopic analysis (SEM or TEM) of a cross section of the powder in combination with image analysis, preferably with the aid of an image analysis program. The preparation of the sample to be analyzed is identical to that previously described in detail.

[0156] For purposes of illustration in a non-limiting manner, a TEM-based procedure is provided below for determining the particle size distribution of silicon-based particles and / or Si-free carbonaceous particles comprising graphitic domains comprised in a powder.

[0157] 1. Acquire multiple TEM images of a cross section of the powder, including multiple cross sections of silicon-based particles and multiple cross sections of Si-free carbon-containing particles including graphitic domains.

[0158] 2. Adjust the image contrast and brightness settings to facilitate observation of cross-sections of different types of particles: particles of matrix material, including silicon-based particles, and Si-free carbonaceous particles, including graphitic domains. The difference in brightness allows for easy differentiation of the different types of particles from the matrix due to their different chemical compositions.

[0159] 3. Using a suitable image analysis program, select from one or more acquired TEM images at least 100 discrete cross-sections of the silicon-based particles and / or at least 100 discrete cross-sections of the Si-free carbon-containing particles that do not overlap with another cross-section of the particles. These discrete cross-sections can be selected from one or more cross-sections of a powder comprising the particles.

[0160] 4. Preferably, a suitable image analysis program is used to measure the d of at least 100 discrete cross-sections of the silicon-based particles and / or at least 100 discrete cross-sections of the Si-free carbon-containing particles comprising graphitic domains. max value.

[0161] Then, the d10, d50 and d90 values of the number-based particle size distribution of the silicon-based particles and / or the Si-free carbon-containing particles including graphite domains determined using the above method are calculated. These number-based particle size distributions can be easily converted to weight-based or volume-based particle size distributions via well-known mathematical formulas.

[0162] Determination of volume-based particle size distribution

[0163] The volume-based particle size distribution of the silicon-based powder was measured by centrifugal sedimentation using a centrifugal sedimentation spectrometer DC20000 (CPS Instruments, Inc, USA).

[0164] The instrument was equipped with a hollow polycarbonate disk with an inner radius of 4.74 cm. The rotation speed was set to 20,000 rpm, which corresponds to approximately 1.9 × 10 5 m / s 2 centrifugal acceleration force.

[0165] The disk was filled with 16 ml of a linear density gradient (10% to 5%) of Halocarbon 1.8 (chlorotrifluoroethylene-PCTFE) in ethyl 2-butoxyacetate (casrnll2-07-2).

[0166] As a reference material, a 0.52 μm average diameter and a specific density of 3.515 g / cm 3 Diamond particles. Sample preparation:

[0167] A 10 wt% suspension of the silicon-based powder to be analyzed in isopropanol was prepared using ultrasound (Branson sonifier 550 W).The suspension was diluted with ethyl butoxyacetate to a final concentration of 0.05 wt% silicon.

[0168] 0.050 ml of the resulting sample was injected into the dish and the absorbance was recorded as a function of time at a wavelength of 470 nm.

[0169] The resulting time-absorbance curves were converted to particle size distribution (mass or volume) using the built-in algorithm (DCCS software) and the following parameters:

[0170] Rotating fluid density: 2.33 g / cm 3

[0171] Refractive index of rotating fluid: 1.482

[0172] Silicon density: 2.33g / cm 3

[0173] Silicon refractive index: 4.49

[0174] Silicon adsorption coefficient: 17.2K

[0175] The volume-based particle size distribution of the silicon-based powder was determined using the method described above and assigned D10, D50, and D90 values.

[0176] The volume-based particle size distribution of powders according to or not according to the invention was determined by laser diffraction Sympatec (Sympatec-Helos / BFS-Magic 1812) according to the user's instructions. The following settings were used for the measurement:

[0177] -Dispersed system: Sympatec-Rodos-M

[0178] - Disperser: Sympatec-Vibri 1227

[0179] - Lens: R2 (0.45μm-87.5μm range)

[0180] -Dispersion: 3 bar compressed air

[0181] -Optical density: 3%-12%

[0182] - Start / Stop: 2%

[0183] -Time base: 100ms

[0184] -Feed rate: 80%

[0185] -Aperture: 1.0mm

[0186] It is important to note that feed rate and aperture setting can vary with optical density.

[0187] Then, the D10, D50 and D90 values of the volume-based particle size distribution of the powder (according to or not according to the invention) determined using the above-described method are calculated.

[0188] Determination of the size of graphitic domains

[0189] The size of the graphitic domains can be determined by TEM analysis of a cross section of the powder, as explained previously.

[0190] However, the preferred method is X-ray diffraction (XRD) analysis of the powder. The following method is used.

[0191] The CuKal and CuKo2 irradiation was performed on Panalytical's X Pert Pro system to measure at least about 2 cm 3 The flat surface of the powder material was subjected to XRD measurement with λ=0.15418 nm, a step size of 0.017° 2θ, a scan rate of 34 min (2064 s), and a measurement of 2θ from 5° to 90°, using the ICDD database PDF-4+ to identify the compounds of the present invention.

[0192] In the 2θ range between 26° and 27° Cu The XRD peak with a maximum at 0.02 corresponds to the (002) reflection of graphitic carbon, which is generated by X-ray diffraction from the interplanar graphene layers. First, the background is subtracted from the raw XRD data. Then, the 2θ values at half maximum intensity on the left and right sides of the C(002) peak are measured. Cu The full-width-at-half-maximum (FWHM) value is the value of these two 2θ Cu The difference between the values is calculated using the FWHM value. The FWHM value is typically determined using the program provided with the X-ray diffractometer. Manual calculations can also be used.

[0193] Finally, the average size of graphite domains included in the Si-free carbonaceous particles is calculated by applying the Scherrer equation to the C(002) peak using the just measured FWHM value, the X-ray wavelength of the device, and the position of the C(002) peak.

[0194] Determination ratio I c / I s

[0195] The powders were analyzed using the X-ray diffraction method described previously. After background subtraction from the raw XRD data, the 2θ values of the peaks assigned to C(002) between 26° and 27° were measured using a program or manually. Cu The maximum intensity I c , and the peaks at 2θ between 28° and 29° are attributed to Si(111). Cu The maximum intensity I s Then calculate the ratio I c / I s .

[0196] Experimental preparation of counterexamples and examples

[0197] Example 1 (E1) according to the present invention

[0198] To produce the powder of Example 1, silicon powder was first obtained by applying a 60 kW radio frequency (RF) inductively coupled plasma (ICP) using argon as the plasma gas, into which a micron-sized silicon powder precursor was injected at a rate of about 50 g / h, thereby obtaining a prevailing (i.e., in the reaction zone) temperature of more than 2000 K. In this first process step, the precursor became completely evaporated. In a second process step, 18 Nm 3 A flow of argon at 100 l / h was used as a quench gas immediately downstream of the reaction zone to reduce the gas temperature to below 1600 K, thereby causing the nucleation of metallic submicron silicon powder. Finally, a passivation step was carried out at a temperature of 100° C. by adding 100 l / h of an N2 / O2 mixture containing 1 mol% oxygen over 5 minutes.

[0199] The specific surface area (BET) of the silicon powder obtained was measured to be 83 m 2 The oxygen content of the silicon powder obtained was measured to be 8.6% by weight. The volume-based particle size distribution of the silicon powder was determined to be: D10=62 nm, D50=112 nm and D90=198 nm.

[0200] Then, a blend was prepared from 26 g of the obtained silicon-based powder and 38 g of petroleum-based asphalt powder.

[0201] The blend was heated to 450°C under N2 to melt the bitumen and, after a waiting period of 60 minutes, mixed under high shear for 30 minutes by means of a Cowles dissolver mixer operated at 1000 rpm.

[0202] The mixture of silicon-based powder in pitch thus obtained was cooled to room temperature under N2 and, once solidified, pulverized and sieved on a 400 mesh sieve to produce an intermediate powder.

[0203] Then, 20 g of the intermediate powder was mixed with 7 g of Si-free carbonaceous particles including graphite domains (i.e., graphene nanosheets (XGSciences The graphene nanoplatelets (i.e., carbonaceous particles containing Si-free graphite domains) were mixed on a roller table for 3 hours, after which the resulting mixture was passed through a grinder to deagglomerate it. Under these conditions, good mixing was achieved, but the graphene nanoplatelets (i.e., carbonaceous particles containing Si-free graphite domains) were not embedded in the pitch.

[0204] The resulting mixture of intermediate powder and graphene nanosheets was further subjected to a thermal post-treatment by placing the product in a quartz crucible in a tube furnace, heating it to 1000°C at a heating rate of 3°C / min, holding it at that temperature for two hours, and then cooling it. All of this was done under an argon atmosphere.

[0205] Finally, the calcined product was manually crushed in a mortar and sieved on a 325 mesh screen to form the final powder.

[0206] The total Si content of the powder was measured by XRF to be 34.6 wt %, with an experimental error of + / - 0.3 wt %. This corresponds to a calculated value based on a weight loss of about 35 wt % of the pitch upon heating and an insignificant weight loss upon heating of the other components. The oxygen content of the powder was measured to be 3.4 wt %. The specific surface area (BET) of the obtained powder was measured to be 4.1 m 2 The volume-based particle size distribution of the powder had D10 equal to 4.1 μm, D50 equal to 13.3 μm and D90 equal to 28.8 μm.

[0207] The average size of the graphitic domains measured by XRD using the Scherrer formula is equal to 13 nm. Cu The XRD peak with the maximum intensity at 28° and 29° at 2θ is attributed to Si(111). Cu The intensity ratio I of the peak with maximum intensity at c / I s Equal to 0.29.

[0208] Based on a visual analysis of 156 cross-sections of particles of the powder of Example 1 observed by TEM, 50 of which were particles containing only some matrix material with Si-based particles dispersed therein and 106 of which were Si-free carbon-containing particles containing graphite domains, this corresponds to a fraction of 0.32 for particles containing matrix material with Si-based domains dispersed therein and a fraction of 0.68 for Si-free carbon-containing particles containing graphite domains with an average size of 13 nm, resulting in a total fraction of 1. The number-based size distribution of the Si-free carbon-containing particles containing graphite domains in the powder had a d50 of 6.2 μm. In addition, pores were observed in the particles of the powder.

[0209] Examples 2 and 3 (E2 and E3) according to the present invention

[0210] To produce the powders of Example 2 (E2) and Example 3 (E3), the same procedure as in Example 1 was used, except that different types of Si-free carbonaceous particles containing graphite domains were mixed with the intermediate powder. E2 and E3 were prepared using two different types of expanded graphite powders, having particles of different sizes and containing graphite domains of different sizes. The results of the analyses performed on the powders from E2 and E3 are given in Table 1.

[0211] The Si and O contents of both powders were comparable to those of the powder of Example 1. The BET values of the powders from E2 and E3 were 3.9 m2 / g and 3.6m 2 The volume-based particle size distribution of the powder from E2 was 4.8 μm with a D10 of 14.3 μm, and a D90 of 29.8 μm. The volume-based particle size distribution of the powder from E3 was 5.2 μm with a D10 of 14.9 μm, and a D90 of 30.8 μm.

[0212] Counterexamples 1 and 2 (CE1 and CE2) not according to the present invention

[0213] To produce the powders of Counterexample 1 (CE1) and Counterexample 2 (CE2), the same procedure as for Example 1 was used, except that different types of Si-free carbon-containing particles comprising graphite domains were mixed with the intermediate powder. CE1 was prepared using graphite particles having large graphite domains (>100 nm). CE2 was prepared using graphene particles having very small graphite domains (<2 nm).

[0214] It may be noted that the powder of Counterexample 1 was produced according to the teaching of prior art document EP 3238296 B1.

[0215] Table 1 gives the results of the analyses performed on the powders from CE1 and CE2.

[0216] For both powders from CE1 and CE2, the fraction of particles comprising Si-free carbonaceous particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm is equal to zero, since for CE1 the average size of the graphitic domains is equal to 180 nm and for CE2 the average size of the graphitic domains is lower than 2 nm, both determined by the Scherrer formula applied to the X-ray diffraction peak of the corresponding powders attributable to C(002), which peak is located between 26° and 27° in 2θ. Cu The maximum intensity I c .

[0217] The Si content, O content and particle size distribution of both powders are comparable to those of the powders from E1, E2 and E3. The BET values of the powders from CE1 and CE2 are equal to 3.6 m 2 / g and 5.8m 2 / g.

[0218] Counterexample 3 (CE3) not according to the present invention

[0219] To produce the powder of Counter Example 3 (CE3), the same silicon-based powder as used for Example 1 was used.

[0220] A blend was prepared from 26g of silicon-based powder, 38g of petroleum-based pitch powder, and 17.7g of expanded graphite powder with a volume-based particle size distribution (D50) of less than 5μm. The blend was heated to 450°C under nitrogen to melt the pitch. After a 60-minute wait, it was mixed under high shear for 30 minutes using a Cowles dissolver mixer operating at 1000 rpm. Under these conditions, the expanded graphite particles (i.e., Si-free carbonaceous particles comprising graphitic domains) became embedded in the pitch.

[0221] The mixture of silicon-based powder and expanded graphite powder in pitch thus obtained was cooled to room temperature under N2 and, once solidified, pulverized and sieved on a 400 mesh sieve to prepare an intermediate powder.

[0222] 27 g of this intermediate powder was further subjected to thermal post-treatment as follows: the product was placed in a quartz crucible in a tube furnace, heated to 1000° C. at a heating rate of 3° C. / min, held at this temperature for two hours, and then cooled. All this was done under an argon atmosphere.

[0223] Finally, the calcined product was manually crushed in a mortar and sieved on a 325 mesh screen to form the final powder.

[0224] The results of the analysis carried out on the powder from CE3 are given in Table 1. The average size of the graphite domains measured by XRD using the Scherrer formula is equal to 26 nm.

[0225] Based on a visual analysis of 128 cross-sections of particles of the powder of Counterexample 3 observed by TEM, only one type of particle was present: particles comprising both matrix material and silicon-based particles, and Si-free carbon-containing particles comprising graphite domains dispersed therein. Since all particles of the powder comprised graphite domains having an average size of 26 nm, the fraction of particles comprising matrix material and silicon-based domains dispersed therein, and not comprising graphite domains having a size greater than 5 nm, preferably greater than 2 nm, was equal to 0, and the fraction of particles comprising Si-free carbon-containing particles comprising graphite domains was equal to 1.

[0226] The Si and O contents of the powders are comparable to those of the powders from E1, E2 and E3. The BET of the powder from CE3 is equal to 5.2 m 2 The volume-based particle size distribution of the powder had D10 equal to 6.5 μm, D50 equal to 17.8 μm and D90 equal to 35.6 μm.

[0227] Table 1: Physical properties of powders E1 to E3 and CE1 to CE3. Fraction (1): Fraction of particles comprising matrix material and silicon-based particles dispersed therein, without graphitic domains having a size greater than 5 nm. Fraction (2): Fraction of particles comprising Si-free carbonaceous particles comprising graphitic domains having an average size of at least 10 nm and at most 45 nm.

[0228]

[0229] Electrochemical evaluation of powders

[0230] The prepared powders were tested in full pouch cells according to the procedure specified above. All powders tested had a specific capacity of 1300 mAh / g ± 10 mAh / g. All pouch cells had a theoretical initial charge capacity of 60 mAh ± 2 mAh. The results obtained for initial coulombic efficiency and cycle life are given in Table 2, and the results obtained for rate performance are given in Table 3.

[0231] As regards the cycle life, the results of the powders from E1, E2 and E3 are compared with the powder from CE1 according to the invention and it can be seen in E1, E2 and E3 that, for the reasons given previously, the cycle life increases with decreasing size of the graphite domains and with the ratio I c / I s The number-based particle size distribution with a low d50 for Si-free carbonaceous particles including graphitic domains (combined with very small graphitic domains (CE2)) leads to a reduced cycle life and low initial coulombic efficiency. The same results are observed when only one type of particle is present (CE3).

[0232] Regarding the rate performance, the results from the powders E1, E2 and E3 are compared with the powder from CE1 according to the invention and it can be seen in E1, E2 and E3 that, for the reasons given previously, the rate performance increases with decreasing size of the graphitic domains and with the ratio I c / I s The capacity charged at a large current (i.e., a large charging rate) increases, and in particular, the electronic conductivity of the powder increases.

[0233] The presence of only one type of particles resulted in a decrease in capacity when charged at high currents, which may originate from the reduced electronic conductivity of powder CE3.

[0234] Table 2: Performance of full cells containing powders E1 to E3 and CE1 to CE3

[0235]

[0236] Table 3: Rate performance of full cells containing powders E1 to E3 and CE1 to CE3

[0237]

Claims

1. A powder for use in a negative electrode of a battery, the powder comprising a mixture of: a first fraction, by number, of particles comprising a carbonaceous matrix material and silicon-based particles dispersed in the carbonaceous matrix material, and a second fraction, based on number, of particles comprising Si-free carbon-containing particles comprising graphitic domains, The powder is characterized by: - the graphite domains contained in the Si-free carbonaceous particles have an average size of at least 10 nm and at most 45 nm, as determined by the Scherrer equation applied to the X-ray diffraction peak of the powder attributable to C(002), the X-ray diffraction peak being at a 2θ angle between 26° and 27° Cu The maximum intensity I c ,and - said particles comprising a carbon-containing matrix material and silicon-based particles dispersed in said carbon-containing matrix material do not contain graphitic domains having a size greater than 5 nm.

2. The powder according to claim 1, wherein the average size of the graphitic domains is at least 12 nm and at most 39 nm.

3. The powder according to claim 1 or 2, wherein the powder is characterized in that the X-ray diffraction pattern of the powder has a peak attributed to C(002) and a peak attributed to Si(111), and the peak attributed to C(002) is at a 2θ angle between 26° and 27°. Cu The maximum intensity I c The peak attributed to Si(111) is between 28° and 29° 2θ Cu The maximum intensity I s , ratio I c / I s Greater than or equal to 0.2 and less than or equal to 2.

0.

4. The powder of claim 1, wherein the Si-free carbon-containing particles comprising graphitic domains are characterized by a number-based size distribution having a d50 less than or equal to 25 μm and greater than or equal to 6 μm.

5. The powder according to claim 1, wherein the Si-free carbon-containing particles comprising graphite domains are made of at least one of the following materials: exfoliated graphite, expanded graphite, graphene nanoplatelets.

6. The powder of claim 1, wherein the silicon-based particles are characterized by a number-based size distribution having a d50 greater than or equal to 20 nm and less than or equal to 150 nm.

7. The powder according to claim 1, having a silicon content C expressed as weight percentage (wt%), wherein 10 wt% ≤ C ≤ 60 wt%.

8. The powder according to claim 1, having a silicon content C and an oxygen content D, both expressed in weight percent (wt%), wherein D≤0.15C. 9 . The powder according to claim 1 , wherein the first fraction based on number of the particles is at least 0.2 and at most 0.8 with respect to a minimum number of 100 particles included in the powder. 10 . The powder according to claim 1 , wherein the second fraction based on number of the particles is at least 0.2 and at most 0.8 with respect to a minimum number of 100 particles included in the powder.

11. The powder of claim 1 comprising pores.

12. The powder of claim 1, wherein the particles of the powder have a volume-based particle size distribution having D10, D50, and D90, wherein 1 μm ≤ D10 ≤ 10 μm, 8 μm ≤ D50 ≤ 25 μm, and 10 μm ≤ D90 ≤ 40 μm.

13. The powder according to claim 1, wherein the powder has a particle size of at most 10 m 2 / g of BET surface area.

14. The powder according to claim 1, characterized in that the matrix material is a product of thermal decomposition of at least one of the following materials: sucrose, coal tar pitch, petroleum pitch, lignin, and resin.

15. A battery comprising the powder according to any one of claims 1 to 14.

Images