Carbon-coated silicon oxide / graphite composite particle and preparation method and application thereof

Abstract

The invention relates to carbon-coated silicon oxide / graphite composite particles and a preparation method and application thereof. Particle composites of the present invention comprise graphite core particles associated with SiOX nanoparticles (0.2 < = X < = 1.8) and coated with a layer of non-graphite carbon, such as pyrolytic carbon deposited by chemical vapor deposition (CVD). The invention also relates to a method for producing such particles as well as to the use and downstream products of the novel composite material, in particular as active material in the negative electrode of Li-ion batteries.

Description

[0001] This application is a divisional application of Chinese patent application No. 201880051726.4, entitled “Carbon-coated silicon oxide / graphite composite particles and preparation methods and applications thereof”, filed on July 20, 2018. Technical Field

[0002] The present disclosure relates to a novel particle composite material comprising SiO X Graphite core particles associated with nanoparticles (0.2≤X≤1.8) and coated with a layer of non-graphite carbon (e.g., pyrolytic carbon deposited by chemical vapor deposition (CVD)). Also included are methods for preparing such particles and uses and downstream products of the new composite material, in particular, its use as an active material in the negative electrode of a Li-ion battery. Background Art

[0003] Silicon (Si) has a theoretical capacity of 3578 mAh / g (based on Li as a fully lithiated phase). 15 Si4), is one of the next generation anode materials for lithium-ion batteries (LIBs). When used for mobile energy applications, one of the main drawbacks involves the large volume changes during electrochemical lithiation and delithiation, which leads to silicon particle fracture and silicon degradation. This in turn leads to limited cycling stability of silicon anodes. Another issue explaining the limited cycling of silicon anodes is related to the reactivity of the silicon surface, which leads to high first cycle charge loss and charge loss during subsequent cycles: due to the volume expansion and fracture of silicon particles during lithium insertion, new reactive surfaces are created, which react with the electrolyte, thereby consuming the electrolyte as well as the lithium in the battery during the cycling process.

[0004] Nanosilicon is formed by reducing the size of silicon powder, chemical vapor deposition of gaseous silicon precursors, nanosilicon composites produced in silicon alloys, or forming silicon in situ in the battery in a replacement reaction of lithium with silicon oxide to form silicon and lithium oxide. Cycling stability can be improved by controlling concentration and electrolyte, but it is still not enough to use silicon-containing graphite electrodes in lithium-ion batteries used in applications that require extended cycle time and durability, such as automotive and energy storage applications. At the same time, as energy density in lithium-ion batteries continues to increase, controlling and maintaining safety is becoming more and more of an issue, as illustrated by some recent incidents involving lithium-ion battery explosions in electronic devices.

[0005] In view of the issues discussed above, it seems that SiO x, silicon metal alloys and nano-Si / carbon composites are considered as alternatives to high-capacity anode materials and may be more suitable candidates. Another solution discussed in the prior art involves reducing the surface reactivity / deposition of a passivation layer of silicon-based materials (and graphite) [Kim et al., Today, Vol. 17, No. 6, July / August 2014; Chevrier et al. Journal of The Electrochemical Society, 161 (5) A783-A791 (2014); or JP 10012241 A]. The layer should be thick but flexible and strong enough not to break during the volume expansion of silicon during lithiation, but at the same time as thin as possible to avoid sacrificing the electrochemical capacity of the LIB cell and limiting the diffusion of lithium through the interface. The protective carbon layer helps to passivate the electrode surface relative to the electrolyte and reduce the amount of passivating electrolyte additives (such as 1-fluoroethylene carbonate).

[0006] A variety of techniques using chemical vapor deposition (CVD) as one of the steps in the preparation of SiO / C composites have been described in the prior art. However, the composite material and its method of manufacture described herein are considered to be unique compared to other Si / carbon composite materials described in the literature.

[0007] The inventors in CN106025220 reported the use of SiO x High reversible capacity and excellent cycling stability of silicon oxide carbon composites as core with carbon shell. The outer shell is made by CVD coating followed by graphite ball milling. In WO 2015 / 186742, the authors propose to combine nanoscale (>100 nm) low crystalline carbon with SiO x Mixed with fibrous carbon and further subjected to chemical vapor deposition treatment to produce a carbon layer. Another disclosure is found in CN105226241, in which nano silicon, nano carbon (graphene, carbon nanotubes and carbon fibers) are mixed with other carbon materials (natural graphite, synthetic graphite, mesophase carbon microspheres, soft carbon or hard carbon) and further coated with silicon or carbon layers.

[0008] CN106025219 describes materials for lithium-ion batteries that provide high specific capacity, processing and cycling performance, again using carbon nanotubes. In this patent application, SiO x / graphite composites are sintered with a carbon source and then carbon nanotubes are grown by chemical vapor deposition. Liu et al. [Journal of Applied Electrochemistry (2009), 39 (9), 1643-1649] prepared nano-SiO particles coated with carbon in a fluidized bed CVD process. It is reported that the particles prepared in this way exhibit less irreversible electrode expansion and enhanced cycle performance. Similarly, the inventors in CN106058228 found that a core-shell structure having a carbon-based core coated with silicon-based nanoparticles showed improved material properties after chemical vapor deposition coating. In the last example, CN106129372 discloses a material for lithium-ion batteries, which comprises a carbon material modified with SiO particles treated at high temperature.

[0009] In view of the above, an object of the present disclosure is to provide an advantageous carbon-coated nano silicon oxide / graphite composite particle material that exhibits favorable electrochemical properties. Summary of the invention

[0010] The present inventors have unexpectedly discovered that spherical natural flake graphite or synthetic graphite (e.g., from petroleum-based raw materials) can be used as a raw material for preparing carbon-coated nano-SiO X The invention relates to a core material of a nanostructured carbon / graphite composite material, wherein the resulting composite particles, when used in lithium-ion batteries, exhibit improved energy performance, particularly compared to composite materials described in the prior art that use microcrystalline graphite, mesocarbon microbeads, or soft carbon or hard carbon as core particles.

[0011] Therefore, in a first aspect of the present invention, there is provided a particle composite material comprising SiO X The nanoparticles are associated with graphite core particles coated with a layer of non-graphitic graphite (eg, pyrolytic carbon), wherein x is from about 0.2 to about 1.8, or from about 0.3 to about 1.2, or from about 0.8 to about 1.2.

[0012] In another related aspect, the present invention provides a method for preparing a particulate composite material comprising SiO2 coated with a non-graphite carbon layer. X Nanoparticle-associated graphite core particles, wherein x is from about 0.2 to about 1.8, or from about 0.3 to about 1.2, or from about 0.8 to about 1.2; comprising:

[0013] a) Graphite carbon particles and SiO X Nanoparticle mixing;

[0014] b) coating the particles from step a) with a non-graphite carbon layer.

[0015] Another aspect of the present invention relates to a particulate composite material as described above, obtainable by the process outlined in the previous paragraph.

[0016] Yet another aspect relates to a composition comprising the particulate composite material described herein, wherein the composition optionally further comprises other materials, such as synthetic or natural graphite.

[0017] In a fourth aspect, the present disclosure relates to a dispersion comprising a particle composite material as described herein above or a composition of the present disclosure in a liquid, optionally wherein the liquid is water, an organic solvent (such as N-methyl-2-pyrrolidone (NMP)) or a mixture thereof.

[0018] Considering that the particle composite material according to the present invention exhibits favorable electrochemical and processing properties, another aspect of the present disclosure includes the use of the particle composite material or the composition described herein as an active material in a negative electrode of a lithium ion battery.

[0019] A negative electrode comprising the particulate composite material or composition of the present invention as active material represents a further related aspect of the present disclosure.

[0020] In another related aspect, the present invention relates to a lithium ion battery comprising the negative electrode of the previous paragraph. Finally, the present invention also provides an electric vehicle, an electric hybrid vehicle or an energy storage battery comprising the lithium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It shows that the SiO X Particle size distribution (PSD) of the pre-dispersion of nanoparticles before and after deagglomeration.

[0022] Figure 2 It shows that the SiO X PSD of nanoparticle pre-dispersion before and after deagglomeration and the nanoparticles containing SiO X PSD of the final dispersion of graphene core particles associated with the nanoparticles.

[0023] Figure 3 It shows that nano-SiO X Different SEM images of graphite / graphite composite A:

[0024] Top left: SEM image of non-carbon-coated powder; Top right: SEM image of an electrode prepared with the non-carbon-coated composite material as the active material; Bottom left: SEM image of carbon-coated Composite A powder; Bottom right: SEM image of an electrode with carbon-coated Composite A.

[0025] Figure 4The CVD carbon-coated nano-SiO X / graphite composite A2.

[0026] Figure 5 The viscosity versus shear rate relationship of active electrode materials comprising various Composite A compositions (ratio of active material (composite) to carboxymethylcellulose binder (WS-C(CMC)) ranging from 97.5 to 2.5, solids content 46%) is shown.

[0027] The uncoated Composite A (diamond curve) shows a higher viscosity than the CVD-coated Composite A with a hydrophilic surface (square curve) or the CVD-coated Composite A with a hydrophobic surface (triangle curve). DETAILED DESCRIPTION

[0028] The present inventors have found that spherical natural flake graphite, flake synthetic graphite or potato-shaped synthetic graphite (ideally with a particle size distribution of D 90 ≤60μm) on non-graphite carbon-coated nano-SiO X The carbon-coated nano-SiO2 / graphite composites can be advantageously used as a matrix (core) in the preparation of composite materials. For example, compared with composite materials using microcrystalline graphite, mesocarbon microspheres, hard carbon or soft carbon particles as cores or compared with uncoated particles, the carbon-coated nano-SiO2 / graphite composites thus formed have a higher carbon content than the composite materials using microcrystalline graphite, mesocarbon microspheres, hard carbon or soft carbon particles as cores. X / graphite composite particles can improve the energy performance of batteries.

[0029] Therefore, in a first aspect, the present invention relates to a particle composite material comprising SiO X Nanoparticles (wherein X is from about 0.2 to about 1.8, or from about 0.3 to about 1.2, or from about 0.8 to about 1.2) are graphite core particles associated with and coated with a non-graphite carbon layer.

[0030] In some embodiments, the non-graphite carbon layer of the composite material of the present invention is pyrolytic carbon, optionally, wherein the pyrolytic carbon has been deposited by chemical vapor deposition (CVD). Suitable CVD techniques include thermal CVD, plasma enhanced CVD, low pressure CVD, atmospheric pressure CVD, chemical vapor infiltration, laser assisted CVD or hot wire CVD. CVD coating can optionally be performed using a carbon-containing gas or vapor (such as toluene, benzene, isopropanol, methane, propane, butane, liquid propane gas, natural gas, acetylene or mixtures thereof).

[0031] In some embodiments, the SiO X Nanoparticles are associated with the surface of graphite core particles. It is generally believed that SiO XNanoparticles (having high surface energy due to their small size) will attach to the surface by physical adsorption to the surface of the graphite core particles. However, of course, other ways of associating with the surface of the graphite particles are also contemplated in the context of the present disclosure.

[0032] In some embodiments, the graphite core particles of the composite material of the present invention are selected from natural graphite or synthetic graphite. In some embodiments, graphite can be flaky natural graphite or flaky synthetic graphite. In other embodiments, the core particles are spherical natural graphite or "potato-shaped" synthetic graphite. In some of these embodiments, the average aspect ratio (length-to-width ratio, aspect ratio) between the shortest axis and the longest axis of the spherical natural graphite core particles is about 0.4 to 1.0, or about 0.5 to 1.0, or about 0.6 to 1.0. The average aspect ratio between the shortest axis and the longest axis of the potato-shaped synthetic graphite core particles can be about 0.1 to about 0.6, or about 0.2 to about 0.5, or about 0.2 to about 0.4, or about 0.2 to 0.3.

[0033] In some embodiments, the non-graphite coating of the composite materials described herein can be characterized by a thickness of about 5 to about 200 nm, or about 10 to about 100 nm, or about 10 to about 50 nm, or about 20 to about 80 nm, or about 40 to 80 nm, or about 50 to 70 nm, or less than 100 nm, or less than 80 nm, or less than 50 nm.

[0034] In some embodiments, the composite material of the present invention can be characterized by a particle size distribution (PSD) D 50 In certain embodiments, the composite material may be characterized in that, alternatively or additionally, D 90 Less than about 60 μm, or less than about 50 μm, or less than about 40 μm, or less than about 30 μm, or about 1 μm to about 40 μm, about 5 μm to about 20 μm, about 30 μm to about 40 μm, or about 10 μm to about 30 μm, or about 10 to about 30 μm.

[0035] In some embodiments, alternatively or additionally, the composite material of the present invention may be characterized in that the BET specific surface area (SSA) is about 1 m 2 / g to about 15m 2 / g, or about 1m 2 / g to about 10m 2 / g, or about 2m 2 / g to about 8m 2 / g; or about 10m 2 / g to about 50m2 / g.

[0036] In certain embodiments, alternatively or additionally, the composite material of the present invention may be further characterized in that the elemental silicon content measured by spark discharge optical emission spectroscopy (SDOES) is from about 1 to about 10 wt %, or from about 1.2 to about 8 wt %, or from about 1.5 to about 5 wt %. In principle, the elemental silicon content of the composite material may also be determined by its SiO X The composite material can be characterized by its silicon content, but given that the oxygen content may vary, it is preferred to define the material by its elemental silicon content.

[0037] In some embodiments, the composite material of the present invention may also be characterized in that the crystallographic L c The value is at least about 30nm, or at least about 40nm, or at least about 50nm, or at least about 60nm. Therefore, in these embodiments, the composite material is characterized in that the highly crystalline graphite core (SiO X Nanoparticles) and pyrolytic (usually amorphous) carbon coatings on crystallographic L c The value has no significant impact.

[0038] In yet other embodiments, the composite material of the present invention may also be characterized in that, alternatively or additionally, when measured with a laser having an excitation wavelength of 632.8 nm, the Raman I D / I G Ratio (R(I D / I G )) is greater than about 0.2, or greater than about 0.3, or about 0.2 to 1.0, or about 0.4 to 1.0, or about 0.5 to 1.0. Relatively high I D / I G The ratio reflects the presence of non-graphitic / amorphous carbon on the surface of the composite particles.

[0039] In certain embodiments, the composite materials of the present disclosure may also be characterized, alternatively or additionally, by electrochemical properties when used as an active material in the negative electrode of a lithium-ion battery. For example, in some embodiments, the composite materials may also be characterized by an initial coulombic efficiency (ICE) of at least 75%, or at least 80%, or at least 85%, or at least 87%, or at least 88%, or at least 89%, or at least 90%. Alternatively or additionally, the composite materials may also be characterized by a rate performance of at least about 65%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 85%, or at least about 87% at 3C when used as an active material in the negative electrode of a lithium-ion battery.

[0040] The coated composite particles typically have a hydrophobic surface due to the amorphous carbon layer attached to the surface of the composite particles by CVD. However, in some alternative embodiments, the surface can be more hydrophilic, characterized by having good wettability, which can be expressed, for example, as a surface energy of at least 59 mJ / m 2 , or at least 62, or at least 67, or at least 70 mJ / m 2 , and / or expressed as an oxygen content greater than about 200 ppm, greater than about 400 ppm, greater than about 600 ppm, greater than about 700 ppm, or greater than about 800 ppm.

[0041] Such hydrophilic composite particles can be obtained by subjecting the coated particles to an oxidative treatment, wherein the composite particles are contacted with an oxidant in a gas phase / solid phase process with air, carbon dioxide, water vapor, oxygen, ozone or any combination thereof, or alternatively, in a liquid / solid phase process with aqueous hydrogen peroxide or other oxidant present in the liquid phase.

[0042] Further information on the properties of such hydrophilic particles and ways of preparing hydrophilic coatings is described in WO 2016 / 008951 (Imerys Graphite & Carbon Switzerland Ltd.), which is incorporated herein by reference in its entirety.

[0043] In any case, the conditions for controlled oxidation should be chosen to avoid the formation of SiO X The particles oxidize to SiO2 (no longer electrochemically active).

[0044] Method for producing surface-coated silicon oxide / graphite composite particles

[0045] In another aspect, the present invention also includes a method for producing silicon oxide / graphite composite particles (such as those described in the previous section) whose surfaces are coated with non-graphite carbon.

[0046] Therefore, the present invention also relates to a method for producing a particle composite material comprising SiO2 coated with a non-graphite carbon layer. X The method comprises: reacting the graphite carbon particles with SiO X The nanoparticles are mixed (step (a)) and the particles from the mixing step are subsequently coated with a non-graphitic carbon layer (step (b)). In this context, the term "mixing" should be understood in the broadest way, i.e. it includes not only the mixing of liquids or liquid dispersions, but also "dry mixing", sometimes also called "blending".

[0047] In some embodiments of the present invention, the mixing step (a) comprises mechanically mixing the graphite carbon particles and SiO in a suitable mixer or blender. X In other embodiments, step a) comprises mixing graphite carbon particles and SiO in a so-called "hybridization system" (e.g., the Nara Hybridization System (NHS) from Nara Machinery Co. Ltd). X Nanoparticles. Hybrid systems can achieve better particle dispersion because the particles are exposed to high airflow compared to mechanical blending systems. Typically, the above hybridization is performed with dry materials, i.e. no solvent or dispersant is used in this process (although the process can in principle be performed with a dispersion).

[0048] Alternatively, step (a) may comprise preparing a mixture comprising graphitic carbon particles and SiO X A liquid dispersion of nanoparticles is prepared and then the dispersion is dried. The liquid is typically selected from water, an organic solvent or a mixture thereof. When an organic solvent is used, the solvent should be environmentally friendly. Alcohols (e.g., ethanol, isopropanol) or acetone or other non-toxic / harmless organic solvents are preferred.

[0049] The preparation of the liquid dispersion can be carried out in a suitable mill, such as a bead mill or a planetary mill. Another possibility is to prepare a slurry followed by a drying step to remove the solvent / liquid.

[0050] In certain embodiments, the drying step is advantageously performed by spray drying, which can optionally be performed in a spray dryer, a spouted bed, or a fluidized bed reactor. Spray drying has been found to be particularly suitable for obtaining SiO X Composite particles with nanoparticles evenly distributed on graphite core particles.

[0051] Then the nano-SiO X The non-graphite carbon coating is performed on the graphite / graphite composite particles. In some embodiments, the coating is performed by chemical vapor deposition (CVD) of pyrolytic carbon. This pyrolytic carbon deposition layer passivates the surface and reduces the BET SSA by about 30% to 90%.

[0052] Typically, the amorphous carbon layer should be thick enough to evenly cover the composite, but at the same time less than a thickness that would cause cracking during pressing, which would expose more reactive surfaces to the electrolyte. CVD methods are particularly well suited to achieving this goal because CVD produces very uniform coatings and does not contain polycyclic aromatic hydrocarbons (which are often a result of bitumen coating).

[0053] In some of these embodiments, coating is accomplished by thermal CVD, but other CVD variants such as plasma enhanced CVD, low pressure CVD, atmospheric pressure CVD, chemical vapor infiltration, laser assisted CVD, or hot wire CVD may also be used for the coating step. CVD coating is typically performed using a carbon-containing gas or vapor, such as toluene, benzene, isopropanol, methane, propane, butane, liquid propane gas, natural gas, acetylene, or mixtures thereof.

[0054] One advantage of using a CVD process as a preparation method for the carbon passivation layer is its good process control, e.g. with regard to the possibility of controlling the thickness of the deposited layer and its uniform structure. Three basic types of nanotextures can be obtained by different CVD process conditions. Their density, coherence length along the graphene plane and isotropy can vary. Compared to bitumen coating, CVD is environmentally friendly and does not involve toxic precursors. In addition, CVD using gaseous precursors or organic compound vapors forms thinner layers and uses pyrolytic carbon to fill smaller pores, i.e. gaseous precursors can enter certain pores, but liquid bitumen cannot.

[0055] CVD coating may be suitably carried out in a fluidized bed reactor, a rotary furnace, a tumbling bed reactor or a fixed bed reactor, optionally wherein the temperature during CVD coating is maintained at 600 to 1200° C. or 800 to 1100° C. The CVD process is typically carried out at or near atmospheric pressure.

[0056] As is known to those skilled in the art, once the coated material is discharged from the reactor, it should ideally be cooled, subjected to controlled sieving and optionally purified, for example by using magnetic methods to remove impurities.

[0057] When using a CVD process, the amount of layer can be well controlled using one or more parameters such as temperature, treatment time, carbon yield and amount of material to be treated. In some cases, the layer of non-graphite (amorphous) carbon can be 1 to 40 wt%, or 2 to 20 wt%. Alternatively or additionally, the thickness of the non-graphite continuous coating obtained in step b) can be from about 5 to about 200 nm, or from about 10 to about 100 nm, or from about 10 to about 50 nm, or from about 20 to about 80 nm, or from about 40 to 80 nm, or from about 50 to 70 nm, or less than 100 nm, or less than 80 nm, or less than 50 nm.

[0058] In order to illustrate the above, an example is provided. In one embodiment, 10 kg of the above-mentioned nano-SiO obtained from step a) is XThe composite material of graphite (5%:95% w / w) is loaded into a high temperature fluidized bed reactor and heated to 900°C with a continuous flow of nitrogen or other inert gas. Once the desired temperature is reached, a carbon-containing gas or vapor is used as a carbon source. Such a carbon source can be, for example, toluene, benzene, isopropanol, methane, propane, butane, liquid propane gas, natural gas, acetylene, etc.

[0059] In the case of toluene vapor, in order to achieve a coating of about 4 wt % corresponding to a uniform coating thickness of 30-70 nm, about 600 g of toluene was delivered to the reactor over a total time of 120 minutes.

[0060] When coating was carried out in a rotary furnace, it was found that a temperature of 1000°C, a continuous feed of 2 kg / h of composite material and 3 L / min of propane were required to obtain similar deposition properties.

[0061] The graphitic carbon particles used as raw material in the process are typically selected from natural graphite and synthetic graphite, which may be spherical natural graphite, potato-shaped synthetic graphite or even flake (natural or synthetic) graphite. Synthetic graphite is typically made from petroleum-based raw materials.

[0062] In certain embodiments, in the case of spherical natural graphite core particles, the graphite carbon particles used as the raw material may be characterized by an average aspect ratio (ratio between the shortest axis and the longest axis) of about 0.4 to about 1.0. Alternatively, in certain cases, the average aspect ratio of the synthetic graphite is about 0.1 to about 0.6, or about 0.2 to about 0.5, or about 0.2 to about 0.4, or about 0.2 to 0.3.

[0063] In many cases, graphite particles are characterized by a particle size distribution (PSD) D 50 From about 5 to about 50 μm, or from about 7 to about 50 μm, or from about 10 to about 50 μm, or from about 10 to about 30 μm, or from about 10 μm to about 20 nm. Alternatively or additionally, the graphite particles may be characterized by D 90 Less than about 50 μm, or less than about 40 nm, or less than about 30 nm, or about 10 to about 30 μm.

[0064] Alternatively or additionally, the graphite particles may be characterized by a BET SSA of about 1 m 2 / g to about 40m 2 / g, or about 3m 2 / g to about 20m 2 / g, or about 4m 2 / g to about 20m 2 / g; or about 5m 2 / g to about 10m 2 / g.

[0065] In order to ensure excellent electrochemical performance of the composite material, ideally, the graphite particles should have a high degree of crystallinity. Therefore, in certain embodiments, the graphite particles used as the starting material in the method may also be characterized by a crystallographic L c The value is at least about 30 nm, or at least about 40 nm, or at least about 50 nm, or at least about 60 nm.

[0066] Suitable SiO X Nanoparticles are commercially available, for example from US Research Nanomaterials Inc. (USA). Typically, nanoparticles are characterized by a particle size distribution (PSD) D 50 From about 10 to about 1000 nm, or from about 10 to about 300 nm, or from about 15 nm to about 100 nm. Alternatively or additionally, they may be characterized in that D 90 Less than about 1000 nm, or less than about 500 nm, or less than about 300 nm, or less than about 200 nm.

[0067] In some embodiments, SiO X The nanoparticles are also characterized by a BET SSA of about 50 m 2 / g to about 500m 2 / g, or about 80m 2 / g to about 400m 2 / g, or about 100m 2 / g to about 300m 2 / g, or about 150m 2 / g to about 250m 2 / g.

[0068] In some embodiments, the graphite carbon particles used in step a) of the method are X The weight ratio of the nanoparticles is 99:1 to 85:15, or 98:2 to 90:10, or 98:2 to 92:8.

[0069] In some embodiments, the graphite carbon particles are X The average particle size between nanoparticles (expressed as D 50 ) is 5000:1 to 5:1, or 3000:1 to 10:1, or 1000:1 to 30:1, or 200:1 to 40:1, or 100:1 to 5:1.

[0070] In some cases, process step a) may require the preparation of SiO X A liquid pre-dispersion of nanoparticles in a suitable solvent (such as water) and a liquid pre-dispersion of graphitic carbon particles are prepared, and the two pre-dispersions are then combined to prepare a liquid dispersion.X Nanoparticles tend to aggregate (agglomerate) due to their high surface energy, thus, in some cases, making nano-SiO X It is useful to subject the predispersion to a deagglomeration step, as described in more detail below in the working examples, which can suitably be carried out in a ball mill (see also Figure 1 and Figure 2 ).

[0071] In some embodiments, a dispersant may be added in step a) to prevent SiO X Nanoparticles agglomerate. Suitable dispersants include, but are not limited to, nonionic dispersants, for example, selected from the group consisting of secondary alcohols, ethoxylates, alkyl polyglycol ethers, block copolymers, polyethylene, polypropylene, polybutene, and mixtures thereof. Alternatively, the dispersant may also be an anionic dispersant selected from the group consisting of calcium lignin sulfonate or ammonium lignin sulfonate and mixtures thereof.

[0072] In other embodiments, a binder may also be added in step a). Suitable binders are generally selected from the group consisting of lignin-based polymers, polystyrene or its derivatives, styrene-butadiene copolymers, molten phenol resins, polyvinyl alcohol, polyfurfuryl alcohol, furfural, polyurethane, polystyrene acrylates, polyacrylates, polymethyl methacrylate, polymethacrylonitrile, polyoxymethylene, poly(2-phenyl-methyl acrylate), polyisobutylene, polyethylene oxide, polypropylene oxide, polyethylene, polypropylene, polymethyl acrylate, polybutadiene, polyisoprene, polyacrylonitrile, polyaniline, tannic acid, starch, gum arabic, maltodextrin, formaldehydephenol resins, formaldehydetetrahydrofuran resins, nitrile rubber, sucrose, glucose or other sugars, polyethyl ether ketone, polyphenylene sulfide, polyvinyl chloride, carboxymethyl cellulose, methyl cellulose, gelatin, polyvinyl pyrrolidone, polylactic acid, latex and mixtures thereof.

[0073] In these embodiments, the binder may be added to the mixture prior to (spray) drying, or it may be added to the mixture prior to (spray) drying. X The dispersion was added to the SiO before combining with the graphite pre-dispersion. X dispersion or graphite pre-dispersion.

[0074] In some embodiments, the method may include an additional step c) in which the coated composite particles obtained from step b) are subjected to a controlled oxidation treatment. More specifically, this optional step c) comprises exposing the composite particles to an oxidizing agent in a gas phase / solid phase process with air, carbon dioxide, water vapor, oxygen, ozone, or any combination thereof, or alternatively, in a liquid phase / solid phase process with aqueous hydrogen peroxide or other oxidizing agent present in the liquid phase. Further details on this step may be obtained from WO 2016 / 008951 (Imerys Graphite & Carbon Switzerland Ltd.), which is incorporated herein by reference.

[0075] The combined use of a carbon coating process followed by an oxidation treatment enables the production of composite particles with low BET SSA values ​​while achieving the goal of obtaining a surface functionalized with hydrophilic oxygen-containing groups and a favorable surface morphology. As a result, the particle composites with a hydrophilic carbon coating exhibit excellent properties and performance characteristics in lithium-ion battery anodes.

[0076] A method for obtaining new carbon-coated SiO X / graphite composite material, it is obvious that the present disclosure also comprises a particulate composite material as defined herein obtainable by the method described above.

[0077] New SiO particles X / Graphite composite compositions and dispersions

[0078] A SiO2-coated particulate carbon-coated SiO2- X The composition of the carbon / graphite composite material represents another aspect of the present disclosure. In some embodiments, the composition may further include other materials, such as (unmodified or modified) synthetic graphite, natural graphite and / or graphitized mesocarbon spheres. The composition may also include various types of carbon-coated SiO X / graphite composite materials.

[0079] In yet another aspect, the present disclosure relates to a dispersion comprising particulate carbon-coated SiO in a liquid. X The liquid used for the dispersion may be water or an organic solvent (such as N-methyl-2-pyrrolidone (NMP)) or a mixture thereof.

[0080] For example, these dispersions can be used as a basis for electrically conductive coatings or as a basis for the preparation of electrodes for lithium-ion batteries.

[0081] Electrodes and batteries containing new particle composites

[0082] Another aspect of the present invention comprises a particulate carbon-coated SiOX Use of a graphite composite material or a composition comprising the composite material described herein as an active material in a negative electrode of a lithium ion battery.

[0083] In another related aspect, the present disclosure relates to a negative electrode (anode) comprising a particulate carbon-coated SiO X / graphite composite material or a composition comprising the composite material as an active material. In certain embodiments, the negative electrode is suitable for use in a lithium ion battery.

[0084] Therefore, another aspect relates to a lithium ion battery comprising the negative electrode, the negative electrode comprising the particulate carbon-coated SiO as described herein. X / graphite composite material. The main application of such lithium-ion batteries is in portable devices, electric vehicles, hybrid electric vehicles or plug-in hybrid electric vehicles. Another application of lithium-ion batteries containing such materials in the negative electrode is to store energy in the battery for grid stabilization and auxiliary services. Therefore, an electric vehicle, electric hybrid vehicle or energy storage battery containing the above lithium-ion battery represents another aspect of the present invention.

[0085] Measurement method

[0086] Unless otherwise stated, percentage values ​​(%) specified herein are by weight.

[0087] Particle size distribution by laser diffraction

[0088] The presence of particles in a coherent light beam causes diffraction. The size of the diffraction pattern is related to the particle size. A parallel beam of light from a low-power laser illuminates a cell containing a sample suspended in water. The beam leaving the cell is focused by an optical system. The distribution of the light energy in the focal plane of the system is then analyzed. The electrical signal provided by the optical detector is converted into a particle size distribution by a calculator. This method yields the ratio of the total volume of particles to the discrete number of size categories, thereby forming a volume particle size distribution (PSD). The particle size distribution is usually defined by the values ​​D10, D50 and D90, where 10% (by volume) of the particle population has a size less than the D10 value, 50% (by volume) of the particle population has a size less than the D50 value, and 90% (by volume) of the particle population has a size less than the D90 value.

[0089] The particle size distribution of the particles was measured using a Sympatec HELOS BR laser diffractometer equipped with a RODOS / L dry dispersion unit and a VIBRI / L dosing system. A small amount of sample was placed on the dosing system and transported through the beam using 3 bar compressed air. The particle size distribution was calculated for three quantiles and reported in μm: 10%, 50% and 90%.

[0090] refer to:

[0091] ISO 13320-1

[0092] BET specific surface area (BET SSA)

[0093] The method is based on the registration of the absorption isotherm of liquid nitrogen in the range of p / p0=0.04-0.26 at 77K. Nitrogen adsorption is performed on Quantachrome Autosorb-1. Following the procedure proposed by Brunauer, Emmet and Teller (Adsorption of Gases in Multimolecular Layers, J.Am.Chem.Soc., 1938, 60, 309-319), the monolayer capacity can be determined. Based on the cross-sectional area of ​​the nitrogen molecule, the monolayer capacity and the weight of the sample, the specific surface area can be calculated. The isotherms at 77K in the pressure range p / p0 0.01-1 are measured and processed by DFT calculations to evaluate the pore size distribution, the volume and area of ​​micropores and mesopores.

[0094] refer to:

[0095] Ravikovitch,P.,Vishnyakov,A.,Russo,R.,Neimark,A.,Langmuir 16(2000)2311-2320;

[0096] Jagiello,J.,Thommes,M.,Carbon 42(2004)1227-1232.

[0097] Spark Discharge Optical Emission Spectroscopy (SD OES)

[0098] The analysis is carried out by means of a SDAR OES simultaneous emission spectrometer (optical emission spectrometer (OES) with spark discharge in argon: ARL Spectrometer 3460). If necessary, the carbonaceous powder is ground to a maximum particle size of 80 μm by means of a vibrating mill, for example a NAEF grinder with a tungsten carbide container. (Optional) After grinding, the sample is passed through a sieve (for example 0.5 mm) to remove any agglomerates or particles that have not been ground to the desired fineness. The powder is subsequently pressed into pressed pellets, for example by means of a Herzog press.

[0099] Preparation of pressed pellets (using Herzog press):

[0100] After placing a clean cardboard sheet at the bottom of the pressing tool, fill a circular pressing mold with a diameter of at least 20 mm with about 6 g of the sample to be analyzed; carefully place a second clean cardboard sheet on the sample. Lower the upper cylinder and apply pressure until the pressure gauge reads 20 tons. Apply pressure for at least 30 seconds; then release the pressure and remove the sample, while it is still protected on both sides by the cardboard sheet. The sample (now in the form of pellets) can then be analyzed.

[0101] Spectral analysis

[0102] The sample is placed on the excitation stage of the spectrometer under an argon atmosphere. Subsequently, the fully automatic analysis is started (spectrometer manufacturer's software). The analysis is repeated (spinning the sample pellet each time) until reproducible analytical results are obtained. The instrument has been calibrated with internal standards that have been analyzed by an external accredited laboratory.

[0103] refer to:

[0104] K. Slickers, Automatic Emission Spectroscopy, Brühl, Druck und Presshaus Giessen (D) (1992)

[0105] Ash content

[0106] Ash content was assessed by weight loss. A low-wall ceramic crucible was ignited at 800°C in a muffle furnace and cooled to room temperature in a desiccator. A sample of 10 g of dry powder (accuracy 0.1 mg) was placed in a low-wall ceramic crucible. The powder was burned at a temperature of 815°C (at least 8 h) until constant weight. The residue corresponds to the ash content and is reported as a percentage of the initial weight of the sample.

[0107] refer to

[0108] ISO 1171 Solid mineral fuels - Determination of ash content

[0109] ISO 6245 Petroleum products - Determination of ash content

[0110] ISO 8005 Carbonaceous materials used in aluminium production - Billets and calcined coke - Determination of ash content

[0111] DIN 51903 Testing of carbonaceous materials - Determination of ash content - Solids

[0112] ·ASTM C561 Standard Test Method for Ash in Graphite Samples

[0113] ratio I D / I G (R(I D / I G ))

[0114] The ratio I was calculated from Raman measurements using a laser with a wavelength of 632.8 nm. D / I G (R(I D / I G )). G and I D At 1580cm -1 and 1320cm -1 The intensities of the G- and D-band Raman absorption peaks at 100 nm and 100 nm were measured using a LabRAM-ARAMIS Raman microscope from HORIBA Scientific with a 632.8 nm HeNe laser.

[0115] Crystallite size L c

[0116] The crystallite size L was determined by analyzing the (002) and (004) X-ray diffraction patterns. c . For the present invention, the method proposed by Iwashita (N. Iwashita, C. Rae Park, H. Fujimoto, M. Shiraishi and M. Inagaki, Carbon 42, 701-714 (2004)) is used. The algorithm proposed by Iwashita was developed specifically for carbon materials. The line profile width at half maximum of the sample and the reference sample is measured. By means of a correction function, the width of the pure diffraction profile can be determined. The crystallite size is then calculated by applying the Scherrer equation (P. Scherrer, -Nachrichten 2 (1918) p.98).

[0117] Scanning electron microscopy (SEM)

[0118] The particle surface of the carbonaceous material was imaged using a scanning electron microscope (Zeiss Leo 1530SEM) equipped with a stub specimen holder, in which the carbonaceous material was fixed by a conductive glue. -3 Pa) focuses the incident electron beam on the sample and provides space for secondary electron emission, backscattered electrons and emitted X-rays. The secondary electron signal displayed by the detector allows topographic mapping of the sample surface with a maximum magnification of about 100kx and a maximum resolution of about 1nm.

[0119] Wettability / Surface Energy Measurements

[0120] At 20°C, use a spatula to remove 1 cm 3The graphite or graphite composite powder was sprinkled on a microscope slide and pressed at a pressure of 1 bar to make the surface as flat as possible. An aqueous solution with 2.7 wt% 2-propanol was prepared using distilled deionized water. The surface tension of this solution was 59 mN m -1 or 59mJ / m 2 (Calculated from Vazquez et al., J. Chem. Eng. Data, 1995, 40, 611-614). Then, use Easy Drop ( A drop of the solution with a total volume of 10 μL was placed on the powder surface.

[0121] The drop shape analysis software DSA1 was used ( GmbH, Hamburg, Germany) using the tangent method with system water1 ( et al., J. Colloid Interface Sci., 1987, 119, 352), determine the contact angle between a solution droplet and a powder. When the contact angle in this test is less than 90°, the material is considered hydrophilic. If the contact angle is greater than 90°, the material is considered hydrophobic.

[0122] Electrochemical analysis

[0123] Electrode preparation:

[0124] Using a revolution-rotation mixer (THINKY, ARE-310), the electrode components, active materials, CMC solution (2.5 wt% aqueous solution) and SBR dispersion (48.5 wt% aqueous dispersion) were mixed at 2000 rpm for 10 minutes using the weight ratios shown in Table 1. The slurry was coated on a copper foil (t = 18 μm) with a loading of 6 mg / cm 2 , and dried at 80°C for 10 minutes. The coated electrode was then vacuum dried at 120°C for 6 hours. The electrode thus prepared was then pressed to obtain a 1.3 g / cm 3 density.

[0125] Table 1:

[0126]

[0127] Battery preparation:

[0128] Electrochemical measurements were performed in 2032 coin cells at 25 °C in an Ar-filled glove box using a lithium electrode (14 cm Thickness 0.1mm), glass fiber partition (16cm The battery was assembled with 200 μL of electrolyte (1 M LiPF6 in EC:EMC:FEC 18:71:11 w / w).

[0129] The measurement protocol is described in Table 2. The charge capacity is defined as the discharge at cycle 1, the discharge capacity is defined as the charge capacity at cycle 1, and the initial coulombic efficiency (ICE) is calculated by dividing the discharge capacity by the charge capacity. The 3C rate performance is calculated by dividing the capacity obtained at constant current during 3C discharge by the capacity obtained under CC and CV charging during cycle 2.

[0130] Table 2:

[0131]

[0132] Having now generally described various aspects of the invention, it will be apparent to those skilled in the art that many modifications and subtle variations may be made without departing from the spirit and scope of the invention.Some embodiments will now be described by way of illustration with reference to the following working examples.

[0133] Example

[0134] Example 1: Nano-SiO X Preparation of graphite / graphite composite materials

[0135] Silicon oxide nanopowder (SiO2) from US Research Nanomaterials Inc. in water was prepared using a Dispermill at 1000 rpm (mixing for about 1 h). X , 99.5% having a size of 15-20 nm) (pre-dispersion No. 1). X Dispersions of nanoparticles can be prepared with solid contents ranging from 4 to 16%. In the examples described further below, the solid contents were 9.5% and 15%, respectively.

[0136] This dispersion was then treated in a Buhler bead mill MMP1-EX (FDCP) in order to deagglomerate the nanoparticles in the dispersion.

[0137] Table 3 describes the parameters used for this process step.

[0138] Table 3:

[0139] Flow rate dispersion 42％ Corresponds to 2.5kg / min Bead size 0.3-0.4 mm filter 0.15 mm Torque 1000 rpm Cooling temperature 20 ℃ Applied energy 150 KWh / t Estimated processing time 10 Minutes (for the volume tested)

[0140] After this treatment, the dispersion weight and solid content were measured. X The nanoparticles are accurately dispersed in water, e.g. Figure 1 shown.

[0141] A second water-based pre-dispersion (pre-dispersion No. 2) was prepared using graphite particles and (optionally) other additives such as ammonium lignin sulfonate. Second dispersions of different compositions were prepared to provide the final compositions shown in Table 4, each with a mixing time of 1 hour. Afterwards, the two pre-dispersions were thoroughly mixed together to obtain the final dispersion. For this step, mixing was performed in a Dispermill at 1000 rpm for 2 hours. The product of the second pre-dispersion can also be added directly to the first (nano-SiO 2) treated in a bead mill as described above. X ) in a pre-dispersion.

[0142] Table 4 below shows the composition of the final combined dispersions

[0143] Table 4:

[0144] Final composition of the dispersion Recipe 1 Recipe 2 Recipe 3 <![CDATA[Nano - SiO X > 1.52％ 1.80％ 3.33％ Ammonium lignin sulfonate 0.00％ 0.43％ 0.00％ Graphite A 15.15％ 14.43％ 16.67％ water 83.33％ 83.33％ 80.00％ Solid content 16.7％ 16.7％ 20.0％ total 100.0％ 100.0％ 100.0％ <![CDATA[SiO X / Graphite Ratio]]> 10.0％ 12.5％ 20.0％ Ammonium lignin sulfonate / graphite ratio 0.0％ 3.0％ 0.0％

[0145] The final dispersions listed in Table 4 have an acidic pH (5 to 6.5) and a low viscosity (10 s -1 3 to 30 mPa.s at shear rate). Figure 2 The particle size distribution obtained for the final dispersion is shown.

[0146] Finally, in the Mobile Minor of GEANiro Company TM These dispersions were spray dried in a spray dryer to obtain a matrix containing SiO X Composite materials of graphite particles and nanoparticles.

[0147] Table 5 lists the standard conditions for the spray drying process steps.

[0148] Table 5:

[0149] Nozzle pressure (bar) 3 T inlet (C°) 200 T outlet (C°) 80 Intake air flow (%) 70 Hammer(s) 60 Nozzle Type 2-Fluid Nozzle

[0150] In Table 6, the detailed conditions achieved in the spray drying process are shown:

[0151] Table 6:

[0152]

[0153]

[0154] Then, the nano-SiO X The carbon / graphite composite material is used as a raw material in a carbon CVD coating process, as described in more detail below.

[0155] Example 2: Carbon-coated nano-SiO XPreparation of a graphite / graphite composite ("coated composite A")

[0156] Prepare the first nano-SiO using “Formula 1” in Table 4 X / graphite composite material ("Compound A"). Composite A with a silicon content (based on total ash) of 2.8 wt% was loaded into a rotary furnace and CVD-coated with propane gas as a carbon source. The rotary furnace was heated to 1050°C, and the composite was then continuously fed into a rotary kiln still at a temperature of 1050°C. A mixture of propane gas ((C3H8, 3L / min) as an amorphous carbon precursor and nitrogen (N2, 1L / min) as a carrier gas was fed into the reactor to maintain the pressure in the reactor at about 0-20 mbar above atmospheric pressure. A residence time of about 20 minutes was triggered by setting the rotary furnace to an inclination of 4° and a rotation speed of 6rpm. Then, the CVD-coated nano-SiO2 was precipitated in a nitrogen or air atmosphere, respectively, depending on whether a hydrophobic or hydrophilic surface was required. X In the case of using a fluidized bed reactor, such post-treatment is not necessary because the reactor is usually operated in a batch mode and purged with nitrogen or another inert gas before unloading the material from the reactor.

[0157] Table 7:

[0158]

[0159]

[0160] As shown in Table 7, the comparison between the uncoated and carbon-coated composite A shows that the initial coulombic efficiency and rate performance at 3C of the CVD-coated composite are significantly improved. It is worth noting that the carbon coating of the composite particles acts as a thin carbon layer, which closes the open pores on the particles and provides a nano-SiO2 layer attached to the surface of the graphite core particles. X The particles create a protective layer, so the specific surface area (BET SSA) is reduced from 14 to 4.3 m 2 / g.

[0161] Without wishing to be bound by any theory, it is believed that the (CVD) carbon coating converts SiO X The nanoparticles are chemically bonded to the surface of the graphite core particles, thereby ensuring that the SiO X The nanoparticles are uniformly and stably distributed on the core particles. During electrode operation accompanied by significant size changes (breathing) of the particles due to electrochemical lithium insertion and deinsertion, SiO x Chemical attachment to the graphite surface ensures that the particles remain electrically connected. The coating also increases the SiO x The conductivity of the particles and improve the SiOx and the particle / particle contact between the graphite cores because SiO X and the first charging cycle of lithium-ion batteries x The Li2O formed by the electrochemical reaction is an insulator. X In an embodiment of the present invention, the coating of the present invention improves the passivation of the electrode particles during the electrochemical lithium insertion process. This improved passivation prevents the electrolyte from reacting at the electrode surface, thereby reducing the associated charging losses and improving the coulombic efficiency of the electrochemical lithium insertion / deintercalation process.

[0162] Another improvement was observed in the slurry preparation process during the preparation of electrodes for lithium-ion batteries. The material without the carbon coating was found to be difficult to handle during the electrode preparation process. In particular, free SiO was observed during the drying process. X Nanoparticles, resulting in color gradients and electrode inhomogeneity (see Figure 3 SEM photograph in Figure 2, upper right).

[0163] Discovery of Nano-SiO X CVD carbon coating of the nano-SiO / graphite composite particles also improves material processing during electrode preparation. Electrode preparation involves preparing a slurry containing the active material, which is then coated on a metal foil current collector in a wet coating process, followed by drying and rolling to the desired electrode density. X In the coating process of carbon / graphite composite particles, various obstacles were observed, such as agglomeration of undispersed carbon particles, resulting in defects, sedimentation and binder separation, which in turn produced inhomogeneities on the electrode surface. In addition, rather high viscosities were observed, especially at higher solid contents, causing difficulties in slurrying and mixing (see Figure 5 ).

[0164] Example 3: Preparation of Nano-SiO X / Method of Graphite Composite A2

[0165] Prepare nano-SiO using “Recipe 3” in Table 4 X / graphite composite material ("Compound A2"). Composite A2 with a Si content of about 6% (measured using the total ash method) was charged into a rotary furnace and carbon CVD coating was performed using propane gas. The conditions for CVD coating were the same as those in Example 2. The rotary furnace was heated to 1050°C and the composite material was then continuously fed into the rotary kiln. A mixture of propane gas (C3H8, 3 L / min) as an amorphous carbon precursor and nitrogen (N2, 1 L / min) as a carrier gas was fed into the reactor to maintain the pressure in the reactor at about 0-20 mbar above atmospheric pressure. A residence time of approximately 20 minutes was triggered by setting the rotary furnace to a 4° inclination and a 6 rpm rotation speed.

[0166] Table 8:

[0167]

[0168] Given the high nano-SiO X The material “composite A2” exhibited a higher BETSSA than “composite A”. Compared with CVD carbon-coated composite A, CVD carbon-coated composite A2 showed further improved 3C rate performance, while the initial coulombic efficiency was slightly reduced to about 88%.

Claims

1. A particle composite material comprising SiO2 coated with a non-graphite carbon layer X Nanoparticles associated with graphite core particles, wherein the graphite core particles are spherical natural graphite or synthetic graphite, x is 0.2 to 1.8, wherein the non-graphite carbon layer is pyrolytic carbon deposited by chemical vapor deposition, wherein the composite material is characterized by a particle size distribution D 90 1μm to 40μm, the SiO X Nanoparticles are characterized by a particle size distribution D 50 15 nm to 100 nm, and wherein the SiO X The nanoparticles are associated with the surface of the graphite core particles by being physically adsorbed to the surface of the graphite core particles.

2. The composite material according to claim 1, wherein the composite material is further characterized by any one of the following parameters: i) the non-graphite continuous coating has a thickness of 5 to 200 nm; ii) Particle size distribution (PSD) 50 5 to 50 μm, and / or D 90 Less than 60μm; iii) BET SSA is 1m 2 / g to 15m 2 / g; and / or iv) an elemental silicon content of 1 to 10 wt% as measured by spark discharge optical emission spectroscopy (SDOES); and / or v) Crystallography c A value of at least 30 nm; and / or vi) When measured with a laser of 632.8 nm excitation wavelength, Raman I D / I G Ratio (R(I D / I G )) is greater than 0.

2.

3. The composite material according to claim 1, wherein the composite material is further characterized by: i) when used as an active material in a negative electrode of a lithium ion battery, has an initial coulombic efficiency of at least 75%; and / or ii) when used as an active material in a negative electrode of a lithium ion battery, the rate capability at 3C is at least 65%.

4. The composite material according to claim 1, wherein the average aspect ratio between the shortest axis and the longest axis of the spherical natural graphite core particles is from 0.4 to 1.0, or wherein the average aspect ratio of the synthetic graphite is from 0.1 to 0.

6.

5. The composite material according to claim 1, wherein the average aspect ratio between the shortest axis and the longest axis of the spherical natural graphite core particles is from 0.4 to 1.0, or wherein the average aspect ratio of the synthetic graphite is from 0.2 to 0.

3.

6. The composite material of claim 1, wherein the composite material is further characterized by any one of the following parameters: i) the thickness of the non-graphite continuous coating is 50 to 70 nm; ii) Particle size distribution (PSD) 50 10 to 20 μm, and / or D 90 5μm to 20μm; iii) BET SSA is 2m 2 / g to 8m 2 / g; and / or iv) an elemental silicon content of 1.5 to 5 wt% as measured by spark discharge optical emission spectroscopy (SDOES); and / or v) Crystallography c A value of at least 60 nm; and / or vi) When measured with a laser of 632.8 nm excitation wavelength, Raman I D / I G Ratio (R(I D / I G )) is 0.5 to 1.

0.

7. The composite material according to claim 1, wherein the composite material is further characterized by: i) when used as an active material in a negative electrode of a lithium ion battery, has an initial coulombic efficiency of at least 90%; and / or ii) when used as an active material in a negative electrode of a lithium ion battery, the rate capability at 3C is at least 87%.

8. A method for preparing a particle composite material comprising SiO2 coated with a non-graphite carbon layer. X Nanoparticles associated with graphite core particles, wherein the graphite core particles are spherical natural graphite or synthetic graphite, x is 0.2 to 1.8, wherein the non-graphite carbon layer is pyrolytic carbon deposited by chemical vapor deposition, wherein the composite material is characterized by a particle size distribution D 90 1μm to 40μm, the SiO X Nanoparticles are characterized by a particle size distribution D 50 15 nm to 100 nm, and wherein the SiO X The nanoparticles are associated with the surface of the graphite core particles by physical adsorption to the surface of the graphite core particles; the method comprising: a) Graphite carbon particles and SiO X Nanoparticle mixing; b) coating the particles from step a) with a non-graphite carbon layer.

9. The method according to claim 8, wherein step a) comprises: i) mechanically mixing the graphite carbon particles and the SiO X Nanoparticles; or ii) mixing the graphite carbon particles and the SiO X Nanoparticles; or iii) preparing a method comprising the graphite carbon particles and the SiO X A liquid dispersion of nanoparticles followed by drying of the dispersion.

10. The process according to claim 9, wherein the preparation of the liquid dispersion is carried out in a mill.

11. A method according to claim 9 or claim 10, wherein the drying step is performed by spray drying.

12. The method according to any one of claims 8 to 10, wherein the coating step b) comprises chemical vapor deposition (CVD) to deposit a pyrolytic carbon layer on the graphite / SiO obtained in step a). X On composite particles.

13. The method according to claim 12, wherein: CVD coating is carried out in fluidized bed reactors, fixed bed furnaces or rotary furnaces.

14. The method according to any one of claims 8 to 10, wherein the graphitic carbon particles are selected from spherical natural or synthetic graphites.

15. The method according to any one of claims 8 to 10, wherein the SiO X Nanoparticles are characterized by: i) Particle size distribution (PSD) 50 10 to 1000 nm, and / or D 90 Less than 1000nm; ii) BET SSA is 50m 2 / g to 500m 2 / g.

16. The method according to any one of claims 8 to 10, wherein: i) the graphite carbon particles and the SiO X The weight ratio between the nanoparticles is 99:1 to 85:15; and / or ii) the graphite carbon particles and the SiO X The ratio of average particle diameter (D50) between the nanoparticles is 5000:1 to 5:

1.

17. The method according to any one of claims 8 to 10, wherein: i) Step a) comprises preparing the SiO X a liquid pre-dispersion of nanoparticles in a solvent, and a liquid pre-dispersion of said graphitic carbon particles, followed by combining the two pre-dispersions to prepare a liquid dispersion; and / or ii) adding a dispersant in step a) to prevent the SiO X Nanoparticle agglomeration; and / or iii) Adding a binder.

18. The method of claim 8, wherein X is from 0.8 to 1.

2.

19. The method according to claim 9, wherein the liquid is selected from water, an organic solvent or a mixture thereof.

20. The method according to claim 10, wherein the mill is a bead mill or a planetary mill.

21. The method of claim 11, wherein the spray drying is carried out in a spray dryer, a spouted bed or a fluidized bed reactor.

22. The method of claim 12, wherein the coating is plasma enhanced CVD, low pressure CVD, atmospheric pressure CVD, chemical vapor infiltration, laser assisted CVD, or hot wire CVD.

23. The method of claim 22, wherein the CVD coating is performed using a carbon-containing gas or vapor.

24. The method according to claim 23, wherein the carbon-containing gas is toluene, benzene, isopropanol, methane, propane, butane, liquid propane gas, natural gas, acetylene or a mixture thereof.

25. The method of claim 13, wherein the temperature during the CVD coating is maintained at 600°C to 1200°C.

26. The method of claim 13, wherein the temperature during the CVD coating is maintained at 800°C to 1100°C.

27. The method of claim 14, wherein the graphite particles are characterized by: i) Particle size distribution (PSD) 50 5 to 50 μm, and / or D 90 Less than 50 μm; ii) BET SSA is 1m 2 / g to 40m 2 / g; iii) Crystallography c The value is at least 30 nm.

28. The method of claim 14, wherein the graphite particles are characterized by: i) Particle size distribution (PSD) 50 10μm to 20nm, and / or D 90 10 to 30 μm; ii) BET SSA is 5m 2 / g to 10m 2 / g; iii) Crystallography c The value is at least 60 nm.

29. The method according to any one of claims 8 to 10, wherein the SiO X Nanoparticles are characterized by: i) Particle size distribution (PSD) 50 15nm to 100nm, and / or D 90 Less than 200nm; ii) BET SSA is 150m 2 / g to 250m 2 / g.

30. The method according to any one of claims 8 to 10, wherein: i) the graphite carbon particles and the SiO X The weight ratio between the nanoparticles is 98:2 to 92:8; and / or ii) the graphite carbon particles and the SiO X The ratio of average particle diameter (D50) between the nanoparticles is 100:1 to 5:

1.

31. The method according to claim 17, wherein the dispersant is selected from nonionic dispersants; or anionic dispersants; and mixtures thereof.

32. The method according to claim 31, wherein the nonionic dispersant is selected from secondary alcohols, ethoxylates, alkyl polyglycol ethers, block copolymers, polyethylene, polypropylene, polybutene and mixtures thereof, and the anionic dispersant is calcium lignin sulfonate or ammonium lignin sulfonate.

33. The method of claim 17, wherein the binder is selected from the group consisting of lignin-based polymers, polystyrene or its derivatives, styrene-butadiene copolymers, molten phenol resins, polyvinyl alcohol, polyfurfuryl alcohol, furfural, polyurethane, polystyrene acrylate, polyacrylate, polymethyl methacrylate, polymethacrylonitrile, polyoxymethylene, poly(2-phenylmethyl acrylate), polyisobutylene, polyethylene oxide, polypropylene oxide, polyethylene, polypropylene, polymethyl acrylate, polybutadiene, polyisoprene, polyacrylonitrile, polyaniline, tannic acid, starch, gum arabic, maltodextrin, formaldehyde phenol resin, formaldehyde tetrahydrofuran resin, nitrile rubber, sucrose, glucose or other sugars, polyethyl ether ketone, polyphenylene sulfide, polyvinyl chloride, carboxymethyl cellulose, methyl cellulose, gelatin, polyvinyl pyrrolidone, polylactic acid, and latex.

34. The method of claim 12, wherein the coating is thermal CVD.

35. A particulate composite material according to claim 1, obtainable by a method according to any one of claims 8 to 34.

36. A composition comprising the particulate composite material according to any one of claims 1 to 7 or 35.

37. The composition of claim 36, wherein the composition further comprises natural graphite, synthetic graphite and / or graphitized mesocarbon spheres.

38. A dispersion comprising the particulate composite material of any one of claims 1 to 7 or 35 or the composition of claim 36 in a liquid.

39. The dispersion of claim 38, wherein the liquid is water, an organic solvent, or a mixture thereof.

40. The dispersion of claim 39, wherein the organic solvent is N-methyl-2-pyrrolidone (NMP).

41. Use of a particulate composite material according to any one of claims 1 to 7 or 35 or a composition according to any one of claims 36 to 37 as an active material in a negative electrode of a lithium ion battery.

42. A negative electrode comprising the particulate composite material according to any one of claims 1 to 7 or 35 or the composition according to any one of claims 36 to 37 as an active material.

43. The negative electrode of claim 42, wherein the negative electrode is suitable for use in a lithium ion battery.

44. A lithium ion battery comprising the negative electrode defined in claim 42 or 43.

45. An electric vehicle, an electric hybrid vehicle or an energy storage battery comprising the lithium ion battery according to claim 44.

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