Powder for use in the negative electrode of a battery, a method for manufacturing such powder, and a battery containing such powder

Abstract

As a powder suitable for use in the negative electrode of a battery, the powder comprises particles, the particles comprise a matrix material and silicon-based sub-particles embedded in the matrix material, the matrix material comprises a carbonaceous material, and the powder further comprises sulfur, wherein the sulfur content in the powder by weight is at least 0.1% of the carbonaceous material content in the powder by weight and at most 1% of the carbonaceous material content in the powder by weight.

Description

Technology Field

[0001] The present invention relates to a powder for use in the negative electrode of a battery, a method for manufacturing such a powder, and a battery comprising such a powder. Background Technology

[0002] Lithium-ion (Li-ion) batteries are currently the highest-performing batteries and have already become the standard for portable electronic devices. Furthermore, these batteries are rapidly gaining a foothold in other industries, such as automobiles and electrical storage. The advantage of such batteries is high energy density combined with superior power performance.

[0003] Li-ion batteries typically comprise a number of so-called Li-ion cells, each containing a positive electrode, also called a cathode, a negative electrode, also called an anode, and a separator immersed in an electrolyte. Li-ion cells most frequently used in portable applications are developed using electrochemically active materials, such as lithium cobalt oxide or lithium nickel manganese cobalt oxide for the cathode and natural or synthetic graphite for the anode.

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

[0005] In this field, the performance of batteries containing Si-based electrochemical active powders is generally quantified by the so-called full-cell cycle life, which is defined as the number of times or cycles a cell containing such materials can be charged and discharged until it reaches 80% of its initial discharge capacity. Therefore, most research on silicon-based electrochemical active powders focuses on improving the cycle life.

[0006] A disadvantage of using silicon-based electrochemical active materials in the anode is their large volume expansion during charging, which can reach 300% when lithium ions are fully incorporated—for example, by alloying or inserting into the anode active material, a process commonly referred to as lithiation. The significant volume expansion of silicon-based materials during lithium incorporation can induce stress on the silicon particles, which can eventually lead to mechanical degradation of the silicon material. This repetitive mechanical degradation of silicon-based electrochemical active materials, which occurs periodically during the charging and discharging of Li-ion batteries, can reduce the battery's life to an unacceptable level.

[0007] Furthermore, a negative impact associated with silicon is that a thick SEI, or Solid-Electrolyte Interface, can form at the anode. The SEI is a complex reaction product of the electrolyte and lithium, which results in a loss of lithium availability for electrochemical reactions, leading to poor cycle performance characterized by capacity loss during every charge-discharge cycle. A thick SEI can further increase the battery's electrical resistance, thereby limiting the ability to charge and discharge at high currents.

[0008] In principle, SEI formation is a self-terminating process that stops as soon as a 'passivation layer' is formed on the surface of silicon-based materials. However, due to the volume expansion of silicon-based particles, both the silicon-based particles and the SEI may be damaged during discharge (lithiation) and recharging (de-lithiation), freeing up a new silicon surface and allowing SEI formation to start anew.

[0009] To address the aforementioned disadvantages, composite powders are commonly used. In such composite powders, nano-sized 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 may preferably be a carbon-based material forming a matrix.

[0010] Such composite powders are disclosed, for example, in US 10964940, wherein the particulate material is composed of composite particles, and the composite particles comprise a porous carbon framework and a plurality of nanoscale elemental silicon domains located within the pores of the porous carbon framework. WO 2020 / 129879 discloses a cathode mixture for an all-solid-state lithium-ion battery comprising a cathode material and a solid electrolyte, wherein the cathode material comprises a composite (A) containing silicon-containing particles and a carbonaceous material, and a cathode mixture comprising one or more types of components (B) selected from the carbonaceous material and graphite. The problem to be solved

[0011] Despite the use of such composite powders, there is still room for improvement in the performance of batteries containing Si-based electrochemically active powders. In particular, conventional composite powders cannot achieve both the high capacity and long cycle life essential for batteries, especially those for electric vehicles. means of solving the problem

[0012] The object of the present invention is to provide a stable electrochemically active powder comprising (i) a matrix material, a particle containing a silicon-based sub-particle embedded in the matrix material, and (ii) sulfur, which is advantageous in that once the powder is used in the negative electrode of a lithium-ion battery, it enables a long cycle life with high capacity.

[0013] Summary of the Invention

[0014] This objective is achieved by providing a powder according to Embodiment 1, which, once used in the anode of a Li-ion battery, enables the achievement of a higher initial coulombic efficiency (CE) and a higher average coulombic efficiency, as demonstrated in Examples 1 to 4 compared with Counterexamples 1 to 5.

[0015] The present invention relates to the following embodiments:

[0016] Embodiment 1

[0017] In a first aspect, the present invention relates to a powder comprising particles, wherein the particles comprise a matrix material and silicon-based sub-particles embedded in the matrix material, the matrix material comprises a carbonaceous material, and the powder further comprises sulfur, wherein the sulfur content in the powder by weight is at least 0.1% of the carbonaceous material content by weight and at most 1% of the carbonaceous material content by weight.

[0018] Preferably, the sulfur content in the powder by weight is up to 0.8% of the carbonaceous material content by weight, and more preferably up to 0.6% of the carbonaceous material content by weight.

[0019] Preferably, at least 50 weight percent of the matrix material is a carbonaceous material, more preferably at least 70 weight percent of the matrix material is a carbonaceous material, and most preferably at least 90 weight percent of the matrix material is a carbonaceous material.

[0020] Preferably, silicon-based sub-particles are embedded in a carbonaceous material.

[0021] The statement that "the particles contain a matrix material and silicon-based subparticles embedded in the matrix material" means that the particles contained in the powder are, on average, larger in size than the silicon-based subparticles, because they contain the latter. The particles are typically micrometric in size, whereas the silicon-based subparticles are typically nanometric in size.

[0022] "Silicon-based sub-particles embedded in a matrix material" means that silicon-based sub-particles are fixed to and surrounded by the matrix material. The silicon-based sub-particles are covered by the matrix material, most of which, preferably the entirety thereof. Thus, in the powder according to Embodiment 1, the silicon-based sub-particles are preferably in contact only with each other and / or the matrix material.

[0023] Silicon-based subparticles may have any shape, for example, substantially spherical, but may also have irregular shapes, rod-shaped, plate-shaped, etc. In silicon-based subparticles, silicon exists mostly as silicon metal, and small amounts of other elements may be added to improve physical properties, or some impurities such as oxygen or trace amounts of metal may be contained. Considering all elements except oxygen, the average silicon content in such silicon-based subparticles is preferably 80 weight% or more, and more preferably 90 weight% or more, with respect to the total weight of the silicon-based subparticles.

[0024] Unbound by theory, the inventors believe that the presence of sulfur in the powder allows for the formation of bridges between small graphitic domains of the carbonaceous material contained in the matrix material, thereby increasing the elasticity of the carbonaceous material and, consequently, the elasticity of the matrix material. Thanks to its elastic properties, the matrix material can better accommodate the expansion / contraction of silicon-based subparticles during the charging / discharging of the battery, thereby reducing the risk of fracture of the matrix material, the formation of additional solid electrolyte interfaces (SEI), and the risk of silicon-based subparticles being exposed to the electrolyte, which consequently leads to a reduction in first-order and average Coulomb efficiency.

[0025] The sulfur content in the powder by weight must not be lower than 0.1% of the carbonaceous material content by weight, because if the sulfur content is too low, it will not allow the desired technical effect of increasing the elasticity of the carbonaceous material from the matrix to be achieved. Similarly, the sulfur content in the powder must not be higher than 1% of the carbonaceous material content by weight, preferably not higher than 0.8% of the carbonaceous material content by weight, and more preferably not higher than 0.6% of the carbonaceous material content by weight. If the sulfur content is too high, the carbonaceous material from the matrix becomes too elastic and may deform excessively, particularly during battery charging (i.e., lithiation of silicon-based sub-particles). This can potentially lead to unacceptable expansion of the anode, and if the anode expands more than permitted by the battery casing, it can cause both reduced cycle life and safety issues. Furthermore, since sulfur is electrochemically inert, it is best to limit its content to the level necessary to achieve the technical effect in order to maintain the specific capacity of the powder as high as possible.

[0026] The content of carbonaceous material contained in the matrix material of the powder can be measured using conventional techniques or calculated based on the specific volume of the powder. An example of such calculation is provided in the "Analysis Methods" section.

[0027] Preferably, the powder also has a silicon content A and a carbon content B, both expressed in weight percent (wt%), such that 10 wt% ≤ A ≤ 60 wt% and 30 wt% ≤ B ≤ 89 wt%. Too low a silicon content and / or too high a carbon content may result in a cathode material with too low a specific capacity, which is undesirable for industrial applications. Too high a silicon content will result in too high a volume expansion during cycling, which is undesirable primarily for safety reasons. Too low a carbon content will be insufficient to completely cover the silicon-based sub-particles, which will lead to a reaction between the surface of the silicon-based sub-particles and the electrolyte, resulting in the formation of an additional SEI layer and a decrease in battery performance.

[0028] Embodiment 2

[0029] In the second embodiment according to embodiment 1, the carbonaceous material comprises graphite domains, wherein the graphite domains have a mean size of less than 10 nm, determined by the Scherrer equation applied to the X-ray diffraction peak of the powder assigned to C (002), and a 2θ between 26° and 27°. Cu Maximum intensity I C has.

[0030] Preferably, the graphite domains have an average size of less than 5 nm, more preferably less than 3 nm, and most preferably less than 2 nm. Graphite domains having an average size of less than 10 nm, preferably less than 5 nm, more preferably less than 3 nm, and most preferably less than 2 nm are desirable because they result in higher electronic conductivity of the powder compared to graphite domains with a size of 10 nm or more. Furthermore, as previously mentioned, the presence of sulfur in the powder triggers the formation of bridges between small graphite domains of the carbonaceous material contained in the matrix, thereby increasing the elasticity of the carbonaceous material and, consequently, the matrix material. Thus, the smaller the average size of the graphite domains of the carbonaceous material contained in the matrix, the more bridges are formed and the higher the elasticity of the matrix material, which leads to an increase in first-order and average Coulomb efficiency as previously mentioned. That is, there is a synergistic effect between the graphite domain having a size of less than 10 nm, preferably less than 5 nm, more preferably less than 3 nm, and even more preferably less than 2 nm, and sulfur.

[0031] Scherrer equation 2, 98 (1918)) is a well-known equation for calculating the size of ordered (crystalline) domains in X-ray diffraction data. To prevent inter-machine variation, standardized samples can be used for calibration.

[0032] The presence or absence of graphite domains within the matrix material and the determination of their average size can be evaluated, for example, based on transmission electron microscopy (TEM) analysis. Examples of such analysis are provided in the "Analysis Methods" section.

[0033] Embodiment 3

[0034] In the third embodiment according to embodiment 1 or 2, the powder is 0.005 cm, determined by nitrogen adsorption / desorption measurement. 3 It has a total specific volume with a porosity lower than / g. Preferably, the powder is 0.003 cm² 3 It has a porosity lower than / g. More preferably, the powder is 0.002 cm 3 It has a porosity lower than / g. Ideally, the powder is non-porous or not porous.

[0035] Powders with low or even non-porous properties are advantageous, whereas high porosity affects the powder's volumetric capacity (mAh / cm²). 3 Or it will lower the (in Ah / l units), which is contrary to the purpose of achieving a powder with a high specific capacity. Furthermore, the formation of bridges between small graphite domains of the carbonaceous material contained in the matrix is ​​enhanced when the matrix material is dense, that is, when the matrix material and therefore the powder have low porosity or are even non-porous.

[0036] The porosity of the powder can be measured by nitrogen adsorption / desorption measurements. The fact that the powder is not porous can be confirmed through microscopic observation (using SEM or TEM) of one or more cross-sections of the powder particles. Dense particles are considered non-porous, even if they contain a small number of irregularly distributed holes (less than 10 per cross-sectional image at ×50,000 magnification), as this is merely an undesirable result of thermal decomposition of the carbon precursor used to form the matrix material.

[0037] Embodiment 4

[0038] In the fourth embodiment according to embodiment 1 or 2, the carbonaceous material is soft carbon. The matrix material may be composed of soft carbon. Unlike hard carbon, which cannot be graphitized, soft carbon corresponds to an arrangement of small disordered graphite domains that can be converted into graphite when heated at a temperature of 3000 °C.

[0039] Soft carbon is desirable because it exhibits higher electronic conductivity compared to hard carbon. Furthermore, thanks to the disordered collection of small graphite domains that create nano-pores in the matrix material, the volume expansion of particles containing a matrix material primarily composed of soft carbon during anode lithiation is reduced compared to particles containing a matrix material primarily composed of graphite or graphene.

[0040] Embodiment 5

[0041] In the fifth embodiment according to any one of the prior embodiments, at least 80 weight percent of the sulfur contained in the powder is present in the matrix material, and preferably at least 90 weight percent of the sulfur contained in the powder is present in the matrix material.

[0042] That is, less than 20 weight percent, preferably less than 10 weight percent, of the sulfur contained in the powder is present outside the matrix material. While it is desirable for all the sulfur contained in the powder to be present in the matrix material, migration of some sulfur to silicon particles cannot be excluded.

[0043] As previously explained, the technical effect resulting from the presence of sulfur is a matrix material having increased elasticity. Although the technical effect can still be achieved with a reduced sulfur content, it is desirable that most of the sulfur, at least 80 weight percent, preferably at least 90 weight percent, be present in the matrix material. More specifically, the technical effect is expected to be fully maximized when the sulfur is contained in the soft carbon included in the matrix material.

[0044] Embodiment 6

[0045] In the sixth embodiment according to any one of the prior embodiments, the silicon-based sub-particle is d NS It has a number-based size distribution with 50, and d NS 50 is 40 nm or more and 150 nm or less.

[0046] The number-based size distribution can be based on a visual analysis of the minimum number of silicon-based subparticles contained in the powder, with or without the help of an image analysis program. This minimum number of silicon-based subparticles is at least 1,000. An example of determining the number-based fraction of particles is provided in the "Analysis Methods" section.

[0047] For clarity, for example, d of 100 nm NS 50 here means that at least 50% of the number of silicon-based sub-particles have a size smaller than 100 nm, and at least 50% of the number of silicon-based sub-particles have a size larger than 100 nm.

[0048] d of less than 40 nm NS Silicon-based subparticles with a number-based size distribution of 50 are very difficult to disperse efficiently in a matrix material, which can reduce the electronic conductivity of the powder.

[0049] d larger than 150 nm NSSilicon-based subparticles with a number-based size distribution of 50 are prone to cracking during lithiation, which leads to a dramatic reduction in the cycle life of batteries containing such powder.

[0050] d NS 50 is considered unaffected by the powder-making process, which is the d of the silicon-based powder used as a precursor in the process. NS The d value of silicon-based subparticles contained in the powder is 50. NS It means it is equal to the value of 50.

[0051] Embodiment 7

[0052] In the seventh embodiment according to any one of the prior embodiments, the silicon-based sub-particles have a silicon content of at least 80 wt% by weight. Preferably, the silicon-based sub-particles have a silicon content of at least 90 wt% by weight. Preferably, to avoid the specific volume of the silicon-based sub-particles being too low, the silicon-based sub-particles do not contain any elements other than Si and O. Since the silicon-based sub-particles are the main contributors to the specific volume of the powder, it is desirable that their own volume be as high as possible and their silicon content be as high as possible, in this case at least 80 wt%, preferably at least 90 wt%.

[0053] Embodiment 8

[0054] In the eighth embodiment according to any one of the prior embodiments, the powder has a silicon content A and an oxygen content C, both expressed in weight percent (wt%), where C ≤ 0.3 x A. Preferably, C ≤ 0.2 x A and more preferably, C ≤ 0.1 x A.

[0055] Powders with too high an oxygen content undergo additional irreversible consumption of lithium due to the formation of lithium oxide (Li2O) during the primary lithiation of the powder, and thus increase the initial irreversible capacity loss of batteries containing such powder.

[0056] Embodiment 9

[0057] In the ninth embodiment according to any one of the prior embodiments, the powder is up to 10 m 2 / g, preferably up to 5 m 2 It has a BET surface area of ​​ / g.

[0058] In order to limit the formation of a solid electrolyte interface (SEI) that consumes lithium and thereby limit irreversible capacity loss of a battery containing such powder, it is desirable to reduce the surface area of ​​electrochemically active particles in contact with the electrolyte by having the powder have a low BET specific surface area.

[0059] Embodiment 10

[0060] In the 10th embodiment according to any one of the prior embodiments, the powder further comprises graphite particles.

[0061] In particular, graphite particles are not embedded in the matrix material. This can be visually confirmed based on the analysis of one or more SEM images of the powder cross-section. The fact that graphite particles are not embedded in the matrix material is beneficial for at least two reasons: (i) less matrix material is required, which has high irreversible capacity and low specific capacity, since only silicon-based sub-particles need to be covered by the matrix material, and (ii) particles containing a matrix material in which silicon-based sub-particles are embedded are smaller than when the matrix material also contains graphite particles, resulting in less volume expansion during the lithiation of particles during battery cycling.

[0062] However, some contact may exist between the two types of particles located on the outer surface. This is more desirable to ensure the good electronic conductivity of the powder and, consequently, the high rate capability of the battery containing the powder.

[0063] Graphite particles act as spacers between particles containing a matrix material in which silicon-based sub-particles are embedded, preventing these particles containing the matrix material from agglomerated into an agglomerated powder. In the absence of such spacers, mechanical processing such as a grinding step may be required for the agglomerated powder to be used as the negative electrode of a battery, which weakens the integrity of the matrix material and ultimately results in lower performance of the battery containing such agglomerated powder.

[0064] The presence of graphite particles in the powder can be determined, for example, through X-ray diffraction analysis. This method is described in the "Analysis Methods" section.

[0065] It is preferable that the powder contains graphite particles rather than graphene particles, because graphene particles typically have a much higher specific surface and thus significantly increase the formation of the SEI layer during cycling, which is expected to degrade the performance of batteries containing such powder containing graphene particles, especially in the early cycles.

[0066] Embodiment 11

[0067] In the eleventh embodiment, the present invention also relates to a method for producing any of the modified powders defined above. The method comprises the following steps.

[0068] In step A, a powder containing a carbon precursor, a powder containing silicon-based particles, and a powder containing sulfur are provided.

[0069] In Step B, the powder containing the carbon precursor and the powder containing sulfur are mixed, and while mixing to allow the mixture to flow, the resulting mixture is heated to a temperature higher than the softening point of the powder containing the carbon precursor and maintained at that temperature. This ensures good dispersion of the powder containing sulfur within the flow of the carbon precursor.

[0070] In step C, a powder containing silicon-based particles is added to the mixture obtained in step B at a temperature higher than the softening point of the powder containing the carbon precursor and under constant mixing. This ensures good dispersion of the powder containing silicon-based particles within a flow that already contains the powder containing sulfur.

[0071] In step D, the mixture obtained in step C is cooled to room temperature and then milled.

[0072] In step E, the heat treatment of the powder obtained in step D is performed at a temperature equal to at least 1000 °C under an oxygen-free atmosphere. Examples of oxygen-free atmospheres include an argon flow or a nitrogen flow.

[0073] An additional step may include final milling and / or sieving after the powder obtained in step E is cooled to room temperature.

[0074] Preferably, the powder containing silicon-based particles is d VS It has a volumetric particle size distribution with a value of 50, and d VS The value of 50 is up to 200 nm. This is desirable so that the powder containing silicon-based particles is easily dispersed during step C, and the powder obtained at the end of step E contains homogeneously distributed silicon-based sub-particles.

[0075] Embodiment 12

[0076] In the 12th embodiment according to Embodiment 11, the mixture obtained in step B has a sulfur content equal to at least 0.06 wt% and at most 0.65 wt% by weight. This is preferred to obtain the powder according to Embodiment 1.

[0077] Embodiment 13

[0078] In the 13th embodiment according to embodiment 11 or 12, the carbon precursor is converted into soft carbon during the heat treatment of step E. In order to completely convert the carbon precursor into soft carbon, it is important that the temperature at which the heat treatment is performed is at least 1000 °C. In order to prevent the formation of possible silicon carbide and the formation of graphite domains of the carbonaceous material contained in the matrix having an average size greater than 10 nm, the temperature at which the heat treatment is performed is preferably not higher than 1100 °C.

[0079] Embodiment 14

[0080] In the 14th embodiment according to any one of embodiments 11 to 13, the powder containing the carbon precursor is petroleum pitch. Petroleum pitch is advantageous in that it has a relatively high carbon yield of about 65 wt% when fired. When fired at a temperature of at least 1000 °C, the petroleum pitch is converted into soft carbon.

[0081] Embodiment 15

[0082] In the 15th embodiment, the present invention relates to a battery comprising a powder according to any one of embodiments 1 to 10. Specific details for implementing the invention

[0083] In the following detailed description, preferred embodiments are described in detail to enable the practice of the present invention. Although the present invention is described with reference to these specific preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. Conversely, the present invention includes numerous alternatives, modifications, and equivalents that will become apparent from the following detailed description.

[0084] Analysis methods used

[0085] Determination of Si content

[0086] In the examples and control examples, the Si content of the powder is measured by X-ray fluorescence (XRF) using an energy dispersive spectrometer. This method has an experimental random error of + / - 0.3 wt% Si.

[0087] When the Si content of specific particles containing Si-based subparticles or the Si content of the Si-based subparticles themselves needs to be measured, it may be difficult to measure the silicon content by XRF. In such cases, analysis using Scanning Electron Microscopy with Energy Dispersive X-Ray Spectrometry (SEM-EDS) may be preferable. This allows for the measurement of the silicon content in a given particle or subparticle. It is sufficient to analyze 10 particles or subparticles to obtain an average silicon content value.

[0088] Determination of oxygen content

[0089] In the examples and control examples, the oxygen content of the powder is determined by the following method using an oxygen-nitrogen analyzer (Leco TC600). The powder sample to be analyzed is placed in a closed tin capsule, which is then placed in a nickel basket. The basket is placed in a graphite crucible and heated to a temperature higher than 2000 °C under helium as a carrier gas. This causes the sample to melt, and oxygen reacts with the graphite to form CO or CO2 gas from the crucible. This gas is then guided to an infrared measurement cell. The observed signal is recalculated as the oxygen content.

[0090] Determination of carbon content

[0091] In the examples and control examples, the carbon content of the powder is determined by the following method using a carbon-sulfur analyzer (Leco CS230). The sample is melted in a ceramic crucible of a high-frequency furnace under a constant oxygen flow. The carbon in the sample reacts with oxygen gas and leaves the crucible as CO or CO2. After the CO present is finally converted to CO2, all generated CO2 is detected by an infrared detector. The acquired signal is finally converted into carbon content.

[0092] Determination of sulfur content

[0093] In the examples and control examples, the sulfur content of the powder is determined by the following method using a carbon-sulfur analyzer (Leco CS230). The sulfur in the sample reacts with oxygen gas and leaves the crucible as SO2. All generated SO2 is detected by an infrared detector. The acquired signal is finally converted into sulfur content.

[0094] Determination of specific surface area (BET)

[0095] The specific surface area of ​​the powder is measured using the Brunauer-Emmett-Teller (BET) method with a Micromeritics Tristar 3000. 2 g of the powder to be analyzed is first dried in a 120 °C oven for 2 hours, and then N2 purging is performed. Then, the powder is degassed in a vacuum at 120 °C for 1 hour prior to measurement to remove adsorbed species.

[0096] Determination of the total specific volume of porosity

[0097] In the examples and control examples, the total specific volume of the porosity of the powder is determined by the following method using nitrogen adsorption / desorption analysis (Micromeritics Tristar 3020). The powder is introduced into a sample tube and prepared (heating, vacuum, or N2 gas flushing) to remove all foreign molecules from the powder surface and the sample tube.

[0098] Then, it is cooled to the liquid N2 temperature, where N2 adsorption occurs on the powder particles. This adsorption occurs at a relative pressure (P / P) of 0.10 to 0.99. o It is measured at ). Then, the relative pressure is dropped again to cause N2 desorption from the powder particles. This is a relative pressure of 0.99 to 0.10 (P / P o It is measured in ). In this way, the BJH pore size distribution curve is obtained. Finally, the total specific volume of porosity is calculated.

[0099] Determination of electrochemical performance

[0100] In the examples and control examples, the electrochemical performance of the powder is determined by the following method.

[0101] The powder to be evaluated is sieved using a 45 μm sieve and mixed with carbon black, carbon fiber, sodium carboxymethyl cellulose binder, and water (2.5 wt%). The ratio used is 89 weight parts of the powder to be evaluated / 1 weight part of carbon black (C65) / 2 weight parts of carbon fiber (VGCF) and 8 weight parts of carboxymethyl cellulose (CMC). These components are mixed in a Pulverisette 7 planetary ball mill at 250 rpm for 30 minutes.

[0102] Copper foil cleaned with ethanol is used as a current collector. A 200 μm thick layer of the mixed components is coated onto the copper foil. The coated copper foil is then dried under vacuum at 70 °C for 45 minutes. A 1.27 cm² circle is punched from the dried coated copper foil and used as an electrode for a coin cell using lithium metal as the counter electrode. The electrolyte is 1M LiPF6 dissolved in an EC / DEC 1 / 1 + 2% VC + 10% FEC solvent.

[0103] All coin cells are cycled using a high-precision battery tester (Maccor 4000 series) according to the procedure described below, where "CC" represents "constant current" and "CV" represents "constant voltage".

[0104] ● Cycle 1:

[0105] o 6 hours rest

[0106] o CC lithiation from C / 10 to 10 mV, then CV lithiation to C / 100

[0107] o 5-minute break

[0108] o CC delithiation from C / 10 to 1.5 V

[0109] o 5-minute break

[0110] ● From Cycle 2 on:

[0111] o CC lithiation from C / 2 to 10 mV, then CV lithiation to C / 50

[0112] o 5-minute break

[0113] o CC delithiation from C / 2 to 1.2 V

[0114] o 5-minute break

[0115] The Coulombic efficiency (CE) of a coin cell, which is the ratio of the capacity upon delithiation to the capacity upon lithiation in a given cycle, is calculated for the initial and subsequent cycles. Since the SEI formation reaction has a significant impact on CE, the initial cycle is the most critical cycle in terms of Coulombic efficiency. Typically, for silicon-based powders, the Coulombic efficiency in the initial cycle can be as low as 80% (or less), which corresponds to an irreversible capacity loss of 20% for the coin cell, which is very significant. The goal is to reach at least 90% CE in the initial cycle.

[0116] Even if CE increases significantly for subsequent cycles, usually exceeding 99%, an experienced person will recognize that even a small difference in Coulomb efficiency per cycle will have a significant cumulative effect over the hundreds or thousands of charge-discharge cycles the battery is expected to last. For example, a cell with an initial capacity of 1 Ah and an average CE of 99.8% will have a remaining capacity of 0.8 Ah after 100 charge-discharge cycles, which is 60% higher than a cell with an average CE of 99.5% (remaining capacity of 0.5 Ah).

[0117] For a cell containing a cathode powder having a specific capacity of 840 ± 20 mAh / g, the goal is to achieve a Coulomb efficiency (CE) of at least 90% in the initial cycle and an average CE of at least 99.7% from cycle 5 to cycle 50.

[0118] Determination of the volumetric particle size distribution of powder

[0119] The volumetric particle size distribution of the powder is determined by the Laser Diffraction Sympatec (Sympatec-Helos / BFS-Magic 1812) according to user instructions. The following settings are used for measurement:

[0120] - Distributed System: Sympatec-Rodos-M

[0121] - Disperser: Sympatec-Vibri 1227

[0122] - Lens: R2 (range 0.45 - 87.5 μm)

[0123] - Dispersion: 3 bar compressed air

[0124] - Optical concentration: 3 - 12 %

[0125] - Start / Stop: 2 %

[0126] - Time base: 100 ms

[0127] - Feed rate: 80%

[0128] - Aperture: 1.0 mm

[0129] It should be noted that the supply rate and aperture settings may vary as a function of optical density.

[0130] Next, d of the volumetric particle size distribution of the powder containing silicon-based particles, determined using the method described above VS 10, d VS 50 and d VS The value 90 is calculated.

[0131] Determination of number-based particle size distribution

[0132] The number-based particle size distribution of silicon-based subparticles is determined through electron microscopy analysis (SEM or TEM) of powder cross-sections combined with image analysis.

[0133] To perform this, a cross-section of powder, each comprising multiple cross-sections of silicon-based sub-particles and multiple cross-sections of particles of the matrix material, is prepared according to the procedure described below. 500 mg of powder to be analyzed is embedded in 7 g of resin (Buehler EpoxiCure 2), which consists of a mixture of 4 parts of epoxy resin (20-3430-128) and 1 part of epoxy hardener (20-3432-032). A prepared sample with a diameter of 1″ is dried for at least 8 hours. It is then mechanically polished first using Struers Tegramin-30 until a maximum thickness of 5 mm is reached, and then further polished by an ion beam polisher (Cross Section Polisher Jeol SM-09010) at 6 kV for about 6 hours to obtain a polished surface. A carbon coating is finally applied to this polished surface by carbon sputtering for 12 seconds using a Cressington 208 carbon coater to obtain a sample to be analyzed by SEM—also called a "cross-section."

[0134] The prepared cross-section is then Bruker's EDS detector Xflash 5030-127 (30 mm 2 Analysis is performed using JEOL’s FEG-SEM JSM-7600F equipped with a detector (127 eV). The signal from this detector is processed by Bruker’s Quantax 800 EDS system.

[0135] An enlarged version is generated by applying a voltage of 15 kV at an operating distance of several millimeters. Images from backscattered electrons are reported when values ​​are added to images from an optical microscope.

[0136] The size of silicon-based sub-particles is considered to be equal to the maximum straight-line distance between two points on the perimeter of the individual cross-section of the particle.

[0137] To describe the determination of the number-based particle size distribution of silicon-based subparticles in a non-limiting manner, an SEM-based procedure is provided below.

[0138] 1. Multiple SEM images are obtained of cross-sections of a powder containing particles of a matrix material in which silicon-based sub-particles are dispersed.

[0139] 2. The contrast and brightness settings of the images are adjusted so that cross-sections of the matrix material particles and silicon-based sub-particles can be easily visualized. Due to different chemical compositions, differences in brightness allow for easy distinction between the particles and sub-particles.

[0140] 3. At least 1,000 discrete cross-sections of silicon-based subparticles that do not overlap with another cross-section of the silicon-based subparticles are selected from one or more acquired SEM image(s) using suitable image analysis software. These discrete cross-sections of silicon-based subparticles may be selected from one or more cross-sections of a powder containing particles of a matrix material and silicon-based subparticles.

[0141] 4. The size of individual cross-sections of silicon-based subparticles is measured using appropriate image analysis software for each of at least 1,000 individual cross-sections of silicon-based subparticles.

[0142] Then, d of the number-based particle size distribution of silicon-based subparticles determined using the method described above NS 10, d NS 50 and d NS 90 values ​​are calculated. These number-based particle size distributions can be easily converted into weight- or volume-based particle size distributions through well-known mathematical equations.

[0143] Determination of graphite domain size

[0144] The size of the graphite domains contained in carbonaceous materials can be determined through TEM analysis of the powder cross-section obtained as previously described.

[0145] However, the preferred method is X-ray diffraction (XRD) analysis of the powder. The following methods are used.

[0146] XRD measurements of the powder were performed on a Panalytical 'X Pert Pro' system with CuKα1 and CuKα2 radiation, λ = 0.15418 nm, using the ICDD database PDF-4+ to identify the compound, with a step size of 0.017° 2θ, a scan rate of 34 minutes (2064 seconds), and at least about 2 cm 3 Measure 2θ from 5° to 90° on a flat surface of the powder material.

[0147] 2θ between 26° and 27° Cu The XRD peak with a maximum value corresponds to the (002) reflection of graphitic carbon, which arises from X-ray diffraction from inter-plane graphene layers. First, the background is subtracted from the raw XRD data. Then, at half the maximum intensity to the left and right of the C(002) peak, 2θ Cu The value is determined. The Full Width at Half Maximum (FWHM) value is these two 2θ CuIt is the difference between the values. The FWHM value is usually determined using a program provided with the X-ray diffractometer. Manual calculation can also be used.

[0148] Using the FWHM value just measured, the X-ray wavelength of the equipment, and the position of the C(002) peak, the average size of the graphite domains is finally calculated by applying the Scherrer equation to the C(002) peak.

[0149] Determination of the content of carbonaceous material contained in the powder matrix material

[0150] When it is difficult to directly measure the content of carbonaceous material contained in the matrix material of a powder using known physicochemical analysis techniques, the following mathematical method may be used to calculate this content.

[0151] Two powders will be used as examples for the application of the method. The first powder (Ex1) has a content of silicon (Si) 20.0 wt%, oxygen (O) 1.6 wt%, sulfur (S) 0.4 wt%, and carbon I 78 wt%, and the average delithiation capacity measured in the first cycle of three identical coin cells using the previously described method is 795 mAh / g. A carbonaceous material containing Si-based particles and graphite domains having an average size of less than 10 nm is observed by TEM, and the average size of said domains is determined by applying the Scherrer equation described earlier. No graphite particles or other materials having graphite domains larger than 10 nm are observed.

[0152] The second powder (Ex2) has 20.0 wt% Si, 1.7 wt% O, 0.3 wt% S, and 78 wt% C, and the average delithiation capacity measured in the first cycle of three identical coin cells using the previously described method is 820 mAh / g. Both the carbonaceous material containing Si-based particles and graphite domains with an average size of less than 10 nm, and the graphite particles not embedded in the matrix material, are observed by combining TEM and XRD analysis.

[0153] Carbonaceous materials having graphite domains smaller than 10 nm, particularly soft carbon, are known to typically have a specific capacity of about 250 mAh / g as cathode materials. Additionally, graphite particles are known to have a capacity of about 350 mAh / g as cathode materials. In the case of silicon, a specific capacity of 3,000 mAh / g is used, taking into account the irreversible capacity loss occurring during the first cycle.

[0154] Then, the specific volume of the powder is calculated as follows:

[0155] (Equation 1)

[0156] (Equation 2)

[0157] Substituting Equation 2 into Equation 1 yields the following Equation 1:

[0158] (Equation 1)

[0159] Then, the graphite content can be calculated using Equation 2.

[0160] The individual contents for powders Ex1 and Ex2 were calculated using Equation 1 and Equation 2 and are reported in Table 1.

[0161] Individual chemical contents of exemplary examples Ex1 and Ex2 Table 1 Components Powder Ex1 Powder Ex2 Silicon (Si) (wt%) 20.0 20.0 Oxygen (O) (wt%) 1.6 1.7 Sulfur (S) (wt%) 0.4 0.3 Carbonaceous material (wt%) in matrix 78.0 53.0 Graphite (not in the matrix) (wt%) 0.0 25.0 "Carbonaceous material in S / Matrix" ratio 0.51% 0.57%

[0162] It may be mentioned that both powder Ex1 and Ex2 are powders according to the present invention.

[0163] This mathematical method was evaluated using 20 samples with known content of various components and was proven to have a precision margin of at least 10%.

[0164] Experimental preparation of control examples and examples

[0165] Example 1 (E1) according to the present invention

[0166] To prepare the powder of Example 1, a silicon-based powder is first obtained by applying a 60 kW radio frequency (RF) inductively coupled plasma (ICP) using argon as the plasma gas—injecting a micron-sized silicon powder precursor at a rate of approximately 200 g / h to generate a prevalent temperature (i.e., in the reaction zone) exceeding 2000 K. In this first process step, the precursor is completely vaporized. In the second process step, 20 Nm² is applied immediately downstream of the reaction zone to lower the gas temperature to below 1600 K. 3 Nucleation of the metallic sub-micron silicon powder is induced using an argon flow of / h as a quench gas. Finally, a passivation step is performed at a temperature of 100°C for 5 minutes by adding an N2 / O2 mixture containing 1 mole% oxygen at a rate of 100 l / h.

[0167] The specific surface area (BET) of the obtained silicon powder is 81 m² 2 It was measured as / g. The oxygen content of the obtained silicon powder was measured as 7.8 wt%. The number-based particle size distribution of the silicon powder is d NS 10 = 59 nm, d NS 50 = 114 nm and d NS It is determined that 90 = 192 nm.

[0168] Then, a dry blend is prepared with 200 g of petroleum-based pitch powder and 0.25 g of sulfur powder (Sigma-Aldrich, 99.98% purity). It is noted that the sulfur content of the petroleum-based pitch powder used here was measured using the previously mentioned method and was below the detection limit of the equipment. Therefore, the contribution of the pitch powder to the sulfur content in the final powder can be ignored.

[0169] The above blend is heated to a temperature of 400°C under a nitrogen flow, and after a waiting period of 60 minutes, is mixed for 30 minutes under high shear by a Cowles dissolver type mixer operating at 1000 rpm.

[0170] Then, 100 g of silicon powder is added to the mixture just obtained at 400 ℃. The blend is heated to a temperature of 400 ℃ under a nitrogen flow, and after a waiting period of 60 minutes, is mixed for 30 minutes under high shear by a Kauls melter-type mixer operating at 1000 rpm.

[0171] The mixture of silicon-based pitch powder obtained in this way is cooled to room temperature, and once solidified, is ground and sieved through a 400-mesh sieve. Medium powder Manufactures (intermediate powder).

[0172] Thermal post-treatment is additionally provided to the intermediate powder as follows: the product is placed in a quartz crucible of a tube furnace, heated to 1020°C at a heating rate of 3°C / min, maintained at that temperature for 2 hours, and then cooled. All of these operations are performed under an argon atmosphere.

[0173] The fired product is finally manually ground in a mortar and sieved through a 325-mesh sieve to form the final powder.

[0174] The total Si content of this powder was measured to be 40.1 wt% by XRF. The oxygen, carbon, and sulfur content of this powder were measured to be 3.4 wt%, 56.4 wt%, and 0.109 wt%, respectively. Since all carbon is within the matrix material and corresponds to soft carbon with graphite domains of less than 10 nm, the ratio of "S / carbonaceous material within the matrix" is equal to 0.193%.

[0175] The specific surface area (BET) of the obtained powder is 4.8 m² 2 It was measured as / g.

[0176] The main physicochemical properties of powder E1 are reported in Table 2.

[0177] Examples 2 (E2) and 3 (E3) according to the present invention

[0178] To prepare the powders of Example 2 (E2) and Example 3 (E3), the same method as for the powder of Example 1 is used, except that amounts of 0.45 g and 0.7 g of sulfur powder are used, respectively, instead of 0.25 g of sulfur powder for Example 1. The main physicochemical properties of the powders E2 and E3 obtained accordingly are reported in Table 2.

[0179] Comparative Example 1 (CE1) not in accordance with the present invention

[0180] To prepare the powder of Control Example 1 (CE1), the same method as for the powder of Example 1 is used, except that sulfur powder is not used. The main physicochemical properties of the powder CE1 obtained accordingly are reported in Table 2.

[0181] Comparative Example 2 (CE2) not in accordance with the present invention

[0182] To prepare the powder of Control Example 2 (CE2), the same method as for the powder of Example 1 is used, except that 0.1 g of sulfur powder is used instead of 0.25 g of sulfur powder for Example 1. The main physicochemical properties of the powder CE2 obtained accordingly are reported in Table 2.

[0183] Comparative Example 3 (CE3) not in accordance with the present invention

[0184] To prepare the powder of Control Example 3 (CE3), the same method as for the powder of Example 1 is used, except that 1.7 g of sulfur powder is used instead of 0.25 g of sulfur powder for Example 1. The main physicochemical properties of the powder CE3 obtained accordingly are reported in Table 2.

[0185] Comparative Example 4 (CE4) not in accordance with the present invention

[0186] To prepare the powder of Comparative Example 4 (CE4), the same method as for the powder of Example 3 is used, except that the additional thermal post-treatment provided to the intermediate powder is performed at 1200°C for 8 hours instead of 1020°C for 2 hours for the powder of Example 3. The main result of this thermal post-treatment performed at a higher temperature for a longer period is that the average size of the graphite domains of the carbonaceous material contained in the matrix of powder CE4 is 14 nm, whereas for all other powders produced at a temperature of 1020°C, particularly powder E3, the average size of the graphite domains of the carbonaceous material contained in the matrix is ​​smaller than 10 nm. Accordingly, the main physicochemical properties of the obtained powder CE4 are reported in Table 2.

[0187] Comparative Example 5 (CE5) not in accordance with the present invention

[0188] To prepare the powder of Comparative Example 5 (CE5), a blend is made with 100 g of the silicon-based powder prepared in Example 1 and a thermosetting polymer. The weight ratio of the thermosetting polymer to Si is 0.2. The polymer used is a phenol-formaldehyde resin. The blend is further placed in an aerated oven, where the thermosetting polymer is cured at a temperature of 150 °C. The obtained cured powder is subsequently bead-milled into submicron particles.

[0189] Then, a dry blend is prepared with 180 g of petroleum-based pitch powder and 0.7 g of sulfur powder. The blend is heated to a temperature of 400 ℃ under a nitrogen flow, and after a waiting period of 60 minutes, is mixed for 30 minutes under high shear by a Kauls melting type mixer operating at 1000 rpm. Then, 100 g of milled silicon-polymer particles are added to the mixture just obtained, still at 400 ℃. The blend is heated to a temperature of 400 ℃ under a nitrogen flow, and after a waiting period of 60 minutes, is mixed for 30 minutes under high shear by a Kauls melting type mixer operating at 1000 rpm.

[0190] The mixture of silicon-polymer particles in the pitch obtained in this way is cooled to room temperature, and once solidified, it is crushed and sieved through a 400-mesh sieve to produce an intermediate powder.

[0191] Thermal post-treatment is further provided to this intermediate powder as follows: the product is placed in a quartz crucible of a tube furnace and heated to 1020 °C at a heating rate of 3 °C / min, maintained at that temperature for 2 hours, and then cooled. All of these operations are performed under an argon atmosphere. The thermosetting polymer present in the mixture decomposes without undergoing an actual melting phase, consequently leaving pores within the carbon matrix created during the heat treatment. The thermosetting polymer acts as a sacrificial material to create porosity.

[0192] The calcined product is finally manually ground in a mortar and pestle and sieved through a 325-mesh sieve to form the final powder.

[0193] The total Si content of this powder was measured to be 40.1 wt% by XRF. The oxygen, carbon, and sulfur contents of this powder were measured to be 3.4 wt%, 56.2 wt%, and 0.305 wt%, respectively. The total specific volume of porosity was 0.016 cm³. 3 / g, whereas the total specific volume of porosity of all powders E1-E3 and C1-CE4 is 0.002 cm 3 / g to 0.004 cm 3 It consists of / g. The matrix material observed by SEM microscopy of various cross-sections of powder CE5 particles appears porous, whereas the matrix material observed by SEM microscopy of various cross-sections of powder E1-E3 and C1-CE4 particles is dense and does not exhibit porosity.

[0194] Example 4 (E4) according to the present invention

[0195] To produce the powder of Example 4 (E4), 20 g of the intermediate powder obtained in Example 2 is mixed with 20 g of graphite on a roller bench for 3 hours, and then the resulting mixture is passed through a mill to de-agglomerate. Under these conditions, good mixing is obtained, but the graphite particles are not embedded in the pitch.

[0196] The obtained mixture is further subjected to thermal post-treatment as follows: the product is placed in a quartz crucible of a tube furnace and heated to 1000°C at a heating rate of 3°C / min, maintained at that temperature for 2 hours, and then cooled. All of these operations are performed under an argon atmosphere.

[0197] The calcined product is finally manually ground in a mortar and pestle and sieved through a 325-mesh sieve to form the final composite powder. The main physicochemical properties of the powder E4 obtained are reported in Table 2.

[0198] Comparative Example 6 (CE6) not in accordance with the present invention

[0199] To produce the powder of Comparative Example 6 (CE6), 20 g of the intermediate powder obtained in Comparative Example 2 is mixed with 20 g of graphite on a roller bench for 3 hours, and then the resulting mixture is passed through a mill to break up agglomerations. Under these conditions, good mixing is obtained, but the graphite particles are not embedded in the pitch.

[0200] The obtained mixture is further subjected to thermal post-treatment as follows: the product is placed in a quartz crucible of a tube furnace and heated to 1000°C at a heating rate of 3°C / min, maintained at that temperature for 2 hours, and then cooled. All of these operations are performed under an argon atmosphere.

[0201] The calcined product is finally manually ground in a mortar and pestle and sieved through a 325-mesh sieve to form the final composite powder. The main physicochemical properties of the resulting powder CE6 are reported in Table 2.

[0202] The specific surface area (BET value) of all powders is 3.2 to 4.8 m² 2 It consists of / g.

[0203] Physicochemical properties of powders E1-E4 and CE1-CE6 Table 2 Example # Si content (wt%) O content (wt%) S content (wt%) In the Matrix Carbonaceous materials (wt%) Not in the Matrix black smoke (wt%) Carbonaceous materials within the S / Matrix Ratio (%) E1 40.1 3.4 0.109 56.4 0.0 0.193 E2 40.0 3.4 0.195 56.4 0.0 0.346 E3 40.1 3.4 0.303 56.3 0.0 0.538 CE1 40.1 3.4 0.0 56.5 0.0 0.0 CE2 40.1 3.4 0.043 56.5 0.0 0.076 CE3 39.8 3.4 0.734 56.1 0.0 1.308 CE4 40.0 3.5 0.295 56.2 0.0 0.525 CE5 40.1 3.4 0.305 56.2 0.0 0.543 E4 20.0 1.7 0.098 28.2 50.0 0.348 CE6 20.1 1.7 0.022 28.2 50.0 0.078

[0204] Electrochemical evaluation of powder

[0205] Powders E1-E3 and CE1-CE5 are tested in coin cells according to the procedure specified above. After the first cycle is completed, the battery is stopped and the primary lithiation and primary delithiation capacities are calculated.

[0206] Powders E1-E3 and CE1-CE5 are further diluted with graphite by blending graphite in a 1:1 mass ratio.

[0207] Then, the diluted powders from the E1-E3 and CE1-CE5 powders obtained accordingly, and powders E4 and CE6, are tested in a coin cell according to the procedure specified above.

[0208] The results are reported in Table 3. To compare cells containing cathode materials with similar capacities, the values ​​of Coulomb efficiency and average Coulomb efficiency in the first cycle reported here are for the diluted powders of E1-E3 and CE1-CE5 and the pure powders of E4 and CE6.

[0209] Performance of coin cells containing powders E1-E4 and CE1-CE6 Table 3 Example # 1st Delithiation Capacity pure powder (mAh / g) 1st Delithiation Capacity Diluted powder (mAh / g) Coulomb efficiency First cycle (%) Average Coulomb efficiency Cycle 5-50 (%) E1 1342 846 90.30 99.75 E2 1343 847 90.73 99.79 E3 1341 845 90.81 99.80 CE1 1342 846 89.31 99.64 CE2 1343 847 89.67 99.68 CE3 1332 839 89.98 99.72 CE4 1336 842 89.79 99.70 CE5 1326 835 88.16 99.69 E4 845 / 90.72 99.78 CE6 846 / 89.65 99.67

[0210] When comparing the results, it is evident that cells containing powders E1-E4 according to the present invention as cathode materials have a higher Coulomb efficiency at cycle 1 and a higher average Coulomb efficiency at cycles 5-50 compared to cells containing powders CE1-CE6 not according to the present invention.

Claims

Claim 1 A powder used for the negative electrode of a battery, wherein the powder comprises particles, the particles comprise a matrix material and silicon-based sub-particles embedded in the matrix material, the matrix material comprises a carbonaceous material, the powder further comprises sulfur, and the content of sulfur in the powder by weight is at least 0.1% of the content of the carbonaceous material by weight and at most 1% of the content of the carbonaceous material by weight. Claim 2 In claim 1, the carbonaceous material comprises a graphitic domain, wherein the graphitic domain has an average size of less than 10 nm, determined by the Scherrer equation applied to the X-ray diffraction peak of the powder assigned to C(002), and a 2θ between 26° and 27°. Cu Maximum intensity I C Powder having Claim 3 In claim 1 or 2, the total specific volume of porosity determined by nitrogen adsorption / desorption measurement is 0.005 cm 3 Powder, less than / g. Claim 4 In claim 1 or 2, the carbonaceous material is a powder that is soft carbon. Claim 5 A powder according to claim 1 or 2, wherein at least 80 weight percent of the sulfur contained in the powder is present in the matrix material. Claim 6 In claim 1 or 2, the silicon-based sub-particle is d NS Having a number-based size distribution with 50, and the above d NS 50 is a powder with a diameter of 40 nm or more and 150 nm or less. Claim 7 In claim 1 or 2, the silicon-based sub-particle is a powder having a silicon content of at least 80 weight% on a weight basis. Claim 8 The powder according to claim 1 or 2, wherein the powder has a silicon content A and an oxygen content C, both expressed in weight percentage (wt%), where 10 wt% ≤ A ≤ 60 wt% and C ≤ 0.3 × A. Claim 9 In claim 1 or 2, up to 10 m 2 Powder having a BET surface area of ​​ / g. Claim 10 A powder comprising graphite particles, in addition to the powder according to claim 1 or 2. Claim 11 A method for manufacturing a powder according to claim 1 or 2, comprising: Step A: providing a powder containing a carbon precursor, providing a powder containing silicon-based particles, and providing a powder containing sulfur; Step B: mixing the powder containing the carbon precursor and the powder containing sulfur, and while continuing to mix, heating the mixture to a temperature higher than the softening point of the powder containing the carbon precursor; Step C: adding and mixing the powder containing silicon-based particles to the mixture obtained in Step B; Step D: cooling the mixture obtained in Step C to room temperature and then milling it; Step E: heat treating the powder obtained in Step D at a temperature equal to at least 1000°C under an oxygen-free atmosphere. Claim 12 A method for producing a powder according to claim 11, wherein the sulfur content in the mixture of step B is equal to at least 0.06 weight% and at most 0.65 weight% on a weight basis. Claim 13 A method for producing a powder according to claim 11, wherein the carbon precursor is converted into soft carbon during heat treatment in step E. Claim 14 A method for producing a powder according to claim 11, wherein the carbon precursor is petroleum pitch. Claim 15 A battery comprising powder according to claim 1 or 2.