Nanoparticulate silicon carbide and electrodes containing nanoparticulate silicon carbide

Abstract

To provide silicon carbide nanoparticles capable of yielding an electrode and battery improved more than a known SiC, particularly a secondary lithium-ion battery.SOLUTION: There is provided nanoparticle silicon carbide (SiC) in the form of a secondary particle which is stoichiometrically doped or undoped, wherein the secondary particle is constituted of an aggregate of SiC primary particles, a particle size of the primary particle is in a range of 5 to 100 nm, and an average size of the secondary particles is 1 to 10 μm. Further, there are provided an anode of a secondary lithium-ion battery containing SiC relating to the present invention, and a secondary lithium-ion battery having the anode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to nanoparticulate silicon carbide and its uses, as well as electrodes comprising nanoparticulate silicon carbide. and a secondary lithium-ion battery having the electrode. [Background technology]

[0002] Mixed doped or non-doped lithium metal oxides are used in so-called "lithium-ion batteries." For example, lithium-ion batteries use secondary lithium Also known as lithium-ion batteries, they are considered a promising battery for battery-powered automobiles, and currently Currently, lithium-ion batteries are used in many vehicle models. Used in tools, computers and mobile phones. In particular, cathode and electrolyte only In addition, the anode is also composed of a lithium-containing material.

[0003] For example, LiM2O4 and LiCoO2 are used as cathode materials. (US 5,910,382) reported that dodecyl nitrate was used as a cathode material for lithium-ion batteries. Doped or undoped mixed lithium transition metal phosphates, especially LiFePO4, have been proposed. There are.

[0004] In the current market-leading and already very high-performance lithium-ion batteries, the electrolyte is typically a liquid. and is composed of an organic solvent such as a carboxylic acid ester and a lithium-containing conductive salt. Such carboxylic acid esters include, for example, ethylene carbonate (EC) dimethyl carbonate (DMC), and diethyl carbonate (DEC). In practice, lithium hexafluorophosphate (LiPF6) is widely used as a conductive salt. .

[0005] For solid electrolytes in secondary lithium-ion batteries, lithium salts are typically used. For example, in JP-A 1990-2-225310, lithium titanium phosphate is proposed as a solid electrolyte. Lithium titanium phosphate, depending on its structure and doping, can The conductivity increases and the electrical conductivity decreases.

[0006] Anode materials are typically graphite or lithium compounds as described above. For example, lithium titanate is used, especially for large capacity batteries. Recently, SiC Various modifications have also been explored, particularly composites with various carbon allotropes. As such, its structure and properties are similar to those of diamond. One of the special features of SiC is that This is the polytypic nature of SiC, which appears in many different phases, each with a different atomic structure. In all known polytypes of SiC, each silicon atom is covalently bonded. It is connected to four carbon atoms by It has a tetrahedral structure.

[0007] The so-called cubic phase β-SiC (also called 3C because of its abc layer sequence) It crystallizes in the zinc blende structure, which is related to the structure of diamond. Other polytypes (27 in total) include hexagonal and rhombohedral structures (15R-SiC, 21R -SiC, etc.) structure, and the hexagonal type is the most common. The simple hexagonal structure (also called α-SiC) is wurtzite-like and has an ab layer sequence. Therefore, it is also called 2H. The more frequently occurring and most technologically important polytype is Retypes 4H and 6H (layer sequences are abcb and abcacb), which are It represents a mixture of the pure hexagonal 2H polytype and the pure cubic polytype 3C. , often referred to as α-SiC. In these polytypes, there is a layer of hexagonal crystals between the two layers. Cubic phase SiC has one (4H) or two (6H) cubic layers embedded in it. Theoretically, a stable Li intercalation structure and high potential (Li / Li + >0.1V ), and is almost chemically inert and stable. It has been shown that lithium ions cannot be intercalated in bulk SiC. This problem has traditionally been overcome by adding carbon allotropes.

[0008] Zheng et al. (Electrochimica Acta 52 (2007) 5863 - 5867) reported that lithium-ion batteries describes an electrode for a water pond, which is made of a composite material containing elemental silicon and carbon. It has been done.

[0009] JP 2008066128 describes a method for producing an electrode for a lithium ion battery, The method includes starting with a polysilane and a carbon source to produce a composite having silicon carbide on a carbon material. US 8,734,674 B1 shows that the lithium ion capacity of silicon carbide is increased by adding graphite The present invention discloses a method for improving the

[0010] Furthermore, Kumar et al. (RSC Adv., 2013, 3, 15028 - 15034) reported that lithium-ion batteries describes the use of silicon carbide as the anode material for C-SiC is produced by chemical vapor deposition. Lipson et al. (J. Phys. Chem. C2012, 1 16, 20949 -20957) demonstrated that the electrochemical lithiation ability of silicon carbide is due to surface graphitization. The improvement is described.

[0011] Early proposals have focused on nanocrystalline SiC, particularly in whisker or fiber form. In some cases, lithium ion insertion was possible.

[0012] Therefore, WO2016 / 078955 discloses particles or discloses a relatively poorly characterized SiC in fiber form, as well as CN1031 No. 37973A discloses non-stoichiometric 4H and 6H-SiC for this purpose. Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide an electrode and battery, particularly a secondary battery, that is improved over known SiC. The present invention provides nanoparticle silicon carbide that can be used to manufacture lithium-ion batteries. [Means for solving the problem]

[0014] The object of the present invention is to provide stoichiometric nanoparticulate silicon carbide SiC in the form of secondary particles, The secondary particles are composed of aggregates of SiC primary particles (primary crystals), and the particle size of the primary particles is The average size of the secondary particles is in the range of 5 to 100 nm, and the average size of the secondary particles is 1 to 10 μm. This is achieved by using nano-grain silicon carbide (SiC).

[0015] The size range of the primary particles is preferably in the range of 10 to 100 nm, more preferably These range from 40 to 100 nm, depending on the sol-gel method of choice (see below). This is the range typically obtained without additional screening or grinding steps. Within these ranges, economic advantages are obtained in production. It offers benefits in later processing but is only accessible through an additional grinding step. and for the reasons stated above, represent desirable but not particularly preferred embodiments. If the particles are larger than 100 nm, the secondary particles will also be too large and will not form in the suspension. This makes it impossible to apply the electrode film uniformly without damaging it. From the size of the particles, the capacity of the particles for lithium ion intercalation is 50%. is significantly reduced in size.

[0016] The aggregates are typically 1200-1600 g / l (1.2-1.6 g / cm 3 ) umbrella Density and 1500-3000g / l (1.5-3g / cm 3 ) compressed density. These unexpectedly high values ​​allow for improved processing of the materials according to the present invention, especially in automated processes. This allows for more efficient processing than materials with lower bulk and compressed densities. The latter value indicates that many materials can be introduced into the device and that the electrodes The amount of active material in the electrode (active mass density of the electrode) can be increased, thereby increasing the energy The advantages of this method include increasing the battery density and therefore the capacity of the battery. D 90 The value depends on the batch, but is usually 8 to 10 μm. For efficient electrode production when used as a secondary particle, the size of the secondary particles should be 2 μm or less. However, it is necessary that the thickness be less than 15 μm.

[0017] Advantageously, the silicon carbide according to the invention has a powder resistivity of less than 28 Ω cm; It is particularly preferred to have a powder resistivity of less than 10 Ω·cm.

[0018] In a preferred refinement of the invention, the nanoparticulate silicon carbide SiC according to the invention has a 3C crystal structure This results in a slightly higher thermal conductivity than other construction types, May offer advantages in thermal management, as well as slightly higher chemical and thermal durability for long-term stability However, other embodiments of the present invention may be advantageous in terms of high cycle stability and high cyclic stability. In some cases, further crystal structures such as 6H-SiC or 4H-SiC or 15R-SiC may also be used. , which may exist as a single phase or mixtures thereof, as well as polymorphic or polycrystalline SiC variants. may also exist.

[0019] In a further embodiment, the silicon carbide of the present invention may contain at least one of the following: Mg, Nb, Zr, B, Cr, V , Sc, Y, Al, N, P, La, Er and Ga, and mixtures thereof. The element is preferably doped with at least one element selected from the group consisting of the so-called from N and / or P for n-doping or B for so-called p-doping and / or Al. This doping reduces the carbon content in the anode during use. The stability and cycling resistance of the silicon dioxide can be further improved. In particular, this is Individual or multiple (e.g., SiC:Al / B) dopant metal ions are present within the lattice structure. The dopant metal ions are preferably incorporated into silicon. 0.05 to 6 at% or 3.5 to 5.5 at%, typically 5 at%, other In an embodiment, the dopant metal cation is contained in an amount of 3.5 to 4.5 atomic %. The amount is selected depending on the dopant element, but the reason is The reason is that the amount affects the crystal structure after being incorporated into the lattice. This is especially true for atoms of elements larger than Si. Therefore, basically, Si Elements with atomic radii smaller than While elements having an atomic radius larger than Al may be incorporated, they are preferably incorporated in relatively small amounts. % or less, for example, 3.5 to 4.5 at % as already mentioned above. It can be said that it is beneficial.

[0020] These elements can be present in their pure elemental form (e.g., aluminum) or in the form of acetic acid. acid salts, acetylacetonates, chlorides, nitrates, sulfates or phosphates (phosphorines) or mixed doping with phosphorus as the dopant element) and borate ( Form of uranium doping or mixed doping with boron as a dopant element It may be used in

[0021] Very particularly preferably, the silicon carbide according to the invention contains B and / or Al (and therefore , SiC:Al, SiC:B, SiC:Al / B), or N and / or P (but doped with SiC:N, SiC:P, SiC:N / P), i.e. The silicon carbide according to the present invention is n-doped or p-doped.

[0022] n-doping is performed using nitrogen, for example, in nitric acid, ammonium chloride, potassium nitrate, or This can be done by adding melamine to the starting sol, or by using phosphorus Adding phosphoric acid, potassium dihydrogen phosphate, or disodium hydrogen phosphate to the starting sol p-doping can be performed with boron, for example, by disodium tetraborate This can be achieved by adding sodium or boron acetylacetonate, Aluminum is used to produce aluminum powder, aluminum chloride, or aluminum This can be done by adding acetylacetonate.

[0023] The nanoparticulate silicon carbide according to the present invention is preferably used in electrodes of secondary lithium ion batteries. Other possible applications include, for example, photovoltaic devices and Examples include solar cells, light emitting diodes and semiconductor components.

[0024] Silicon carbide according to the present invention can, in one embodiment, be used as the active material in an electrode of a secondary lithium ion battery. The electrode can be both a cathode and an anode. In this case, the electrode is the anode.

[0025] In a further preferred refinement of the invention, the SiC of the anode is doped with N or Al. will be done.

[0026] The electrode doped with Al is 0.4V + / - 0.1V vs. Li on the voltage diagram. The presence of a so-called plateau is more pronounced than the presence of a strong voltage drop. This is advantageous because the latter can also be used, for example, in anodes comprising the material according to the invention. and typical cathodes such as NMC (lithium-nickel-manganese-cobalt oxide) This is because an excessively large potential window occurs in the cell composed of the The difference in chemical potential, typically measured relative to a Li reference. Since electronic devices need to compensate for small voltage changes, a small voltage drop across the cell This has practical advantages. The low potentials obtained in this case with the material according to the invention This results in a higher cell voltage and therefore a higher energy density.

[0027] The electrode according to the present invention further comprises a binder, which may be any binder known per se to those skilled in the art. Any binder known in the art can be used, such as, for example, poly(ethylene glycol) copolymers. Tetrafluoroethylene (PTFE), Polyvinylidene difluoride (PVDF), Difluoride Polyvinylidene-hexafluoropropylene copolymer (PVDF-HFP), ethylene -Propylene-diene terpolymer (EPDM), tetrafluoroethylene-hexafluoro Polypropylene copolymer, polyethylene oxide (PEO), polyacrylonitrile ( PAN), polyacrylomethacrylate (PMMA), carboxymethyl cellulose (C MC), and derivatives and mixtures thereof.

[0028] Preferably, the electrode has an active material content of at least 50% by weight, more preferably The electrode according to the present invention has an active material content of 90% by weight or more. Even if the active material is contained in the amount specified, the functionality is not limited.

[0029] Furthermore, the present invention relates to an anode according to the above embodiments, and in particular to a further embodiment A secondary lithium ion battery comprising an anode comprising doped silicon carbide according to the present invention. Regarding.

[0030] Further features and advantages of the present invention can be seen from the following examples of specific embodiments of the invention. However, these examples are not to be construed as limiting the scope of the invention. [Brief explanation of the drawings]

[0031] [Figure 1] 1 shows an SEM photograph of SiC doped with aluminum (3C-SiC:Al). [Figure 2] 1 shows the EDX spectrum of 3C-SiC:Al. [Figure 3] 1 shows an SEM photograph of SiC doped with nitrogen (3C-SiC:N). [Figure 4] 3 shows a voltage diagram of 3C—SiC:Al vs. Li for an electrode according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Measurement method The determination of the BET surface area was carried out according to DIN 66131 (DIN-ISO 9277). For this purpose, Micromeritics Gemini V or Micromeritics Gemini VII were used as measurement devices. Used as a chair.

[0033] X-ray powder diffraction (XRD) measurements were performed using a Siemens XPERTSYSTEM PW3040 / 00 and software. This was performed using DY784.

[0034] SEM images were taken using a LEO 1530 VP microscope connected to a Gemini TFE column at 4 kV. The experiment was carried out at an accelerating voltage of .

[0035] The measurements of pressed density and powder resistivity were carried out simultaneously using a Loresta-GP MCP-T610 resistance measuring device. The experiment was carried out on an ITSUBISHI MCP-PD51 tablet press. This press was nitrogen-operated. It is installed in a glove box, thereby eliminating the potential interfering effects of oxygen and moisture. The hydraulic operation of the tablet press is performed by the manual hydraulic press Enerpac PN80-APJ (maximum The test was carried out at a pressure of 10,000 psi / 700 bar.

[0036] These measurements were carried out under the following settings: Sample size: 4g Applied pressure 7.5kN Resistance Meter Loresta GP Loresta GP Measurement sensor settings ESP ESP Extremely linear Linear Pole spacing 3mm 3mm Pole size 1.4mm 1.4mm Sample shape: Circle Circle Sample size diameter = 20mm 20mm Sample thickness: Depends on sample 5mm Measurement position X:10mm;Y:10mm (10,10) RCF automatic calculation 2.758

[0037] The powder resistivity was then calculated according to the following formula: Powder resistance [Ω cm] = resistance [Ω] x thickness [cm] x RCF

[0038] The compressed density was calculated according to the following formula: Compressed density (g / cm 3 ) = mass of sample (g) / Π×r 2 (cm 2 ) x sample thickness (cm) Typical manufacturing tolerances are up to 3%.

[0039] Determining the density of the active material in the electrode To determine the material density of the active material, 50% active material and 30 wt Super-P carbon were used. % and binder (NMP, N-methyl-2-pyrrolidone) 20 wt % ( A thickness of approximately 60 μm was created.

[0040] For this purpose, the appropriate amount is weighed into a 50 ml screw-top jar and Mix for 5 minutes at 600 rpm on a magnetic stirrer using a Rossbar stirring element. After 1 minute of dispersion using the ultrasonic finger Hielscher UP200S, a glass with a diameter of 4 mm The glass was closed by adding 20 beads and rotated at least 100°C on a rotating table at a speed of 10 rpm. The electrode coating was carried out using the homogeneous suspension obtained in this way. The suspension was applied to a doctor blade with a gap width of 200 μm and a feed rate of 20 mm / s. A laboratory squeegee was used to apply the coating onto an aluminum carrier foil.

[0041] After drying at 80°C in a vacuum drying cabinet, electrodes with a diameter of 13 mm were cut out from the film. The specimens were punched out and mechanically tested in a Specac uniaxial hydraulic laboratory press at room temperature for 60 seconds under a load of 10 tons. To determine the density, the net electrode weight was calculated as The net electrode thickness is determined from the total weight and known weight of the electrode. This was determined using the known thickness of the rear foil minus the thickness.

[0042] g / cm in electrode 3 The effective mass density of the unit is calculated as follows: (Percentage of active material in electrode formula (50%) × Net weight of electrode (g) / (π(0.65cm ) 2 × Net electrode thickness (cm) The value of the active material density in the electrode is 1.7 g / cm for the material according to the present invention. 3 Found It was.

[0043] Determination of particle size distribution: Particle size distributions for mixtures or suspensions and resulting materials are measured using commercially available equipment. The determination is based on a light scattering method, which is known per se to those skilled in the art and In particular, reference is made to the disclosures of JP2002-151082 and WO02 / 083555. In this case, the particle size distribution was measured using a laser diffractometer (Mastersizer S, Herrenberg, Germany). Malvern Instruments) and the manufacturer's software (version 2.19) were used. The Malvern Small Volume Sample Dispersion Unit, DIF2002, was used as the measurement unit. The following measurement conditions were selected: compression range, Active beam length: 2.4 mm, measurement range: 300 RF, 0.05~900 μm. The preparation and measurements of the samples were carried out according to the manufacturer's specifications.

[0044] D 90 The value is the value at which 90% of the particles in the measured sample have a smaller or equal particle diameter. Similarly, D 50 Value and D 10 The value is 50% or 1% of the particles in the measured sample. 0% indicates values ​​with smaller or equal particle diameters, respectively.

[0045] According to one particularly preferred embodiment of the invention, the values ​​mentioned in the preceding description is the volume fraction of each particle in the total volume. 10 Value, D 50 Value, D 90value, and D 90 Value and D 10 Therefore, this embodiment of the present invention is applied to the difference between the values. D mentioned in the Ming 10 Value, D 50 Value and D 90 The value is 10% by volume of particles in the measured sample. Or 50% or 90% by volume of the particle has a smaller or equal particle size. If these values ​​are maintained, the present invention provides a particularly advantageous material, Relatively coarse particles (with a relatively large volume fraction) improve throughput and electrochemical production. Negative impacts on properties are avoided. D 10 Value, D 50 Value, D 90 value, and D 90 Value and D 10 Value and The values ​​mentioned in this description for the difference between the percentage of particles and the volume percentage It is particularly preferably applied to both of the above.

[0046] In the case of compositions (e.g., electrode materials) containing additional components in addition to the silicon carbide of the present invention However, especially in the case of carbonaceous compositions, the light scattering methods described above can produce misleading results. The silicon carbide particles are bonded together by additional (e.g., carbonaceous) material to form larger particles. However, the present invention is not applicable to such compositions because they may form aggregates. The particle size distribution of the material can be determined based on SEM recordings such as: The powder sample is suspended in acetone and dispersed using ultrasound for 10 minutes. Then, a few drops of the suspension are placed on the sample plate of a scanning electron microscope (SEM). The solid concentration and number of droplets in the pull are such that a substantially monolayer of powder particles forms on the carrier. The particles are then separated by settling, thereby preventing the powder particles from hiding each other. The dropping must be done quickly before it can separate according to size. After drying in air, The sample is transferred to the measurement chamber of the SEM. In this example, this is a LEO 1530. This device was excited using a field emission electrode at an excitation voltage of 1.5 kV and a The sample distance is 4 mm. Details of at least 20 randomly placed samples are Magnifications are recorded at 20,000x magnification. These are the overlaid magnifications, respectively. Printed on DIN A4 sheets, preferably at least 20 sheets, together with the rate scale. Each of the sheets contains at least 10 free particles of the material according to the invention that constitute the powder particles. The grain boundaries of the material according to the present invention are fixed and the visible grains are randomly selected. It is defined by the absence of a direct bonded bridge. The bridges due to the carbon material are included in the grain boundaries. The longest and shortest axes of the projection are A ruler is used to measure each selected particle to determine the actual particle size based on the scale ratio. For each measured SiC particle, the arithmetic mean value of the longest and shortest axes is calculated. The measured SiC particles were then analyzed by size classification in the same way as in the light scattering measurement. Plotting the number of particles associated with each size class across the particle size classes reveals that The particle size distribution is obtained by dividing the particle count from small particle classes to large particle classes. Summing down through the child classes gives the cumulative particle size distribution, from which D 10 , D 50 and D 90 can be read directly on the size axis.

[0047] The described method also applies to battery electrodes comprising the material according to the invention. In this case, a fresh cut or crushed surface of the electrode should be placed in the sample container instead of the powder sample. It is fixed to the rear and examined with an SEM.

[0048] Exemplary Embodiments The SiC according to the present invention can be prepared by the method described in, for example, Yajima et al. Chem. Lett. 1975, 931 or B. Friedel, Dissertation Paderborn, 2007, B. Kettner et al. In Adv. Eng. Mater. 2018, 17010 Produced by a modified sol-gel method broadly similar to that described by

[67] . Ta.

[0049] Example 1 Production of nanoparticle silicon carbide (3C-SiC) 1.1 Preparation of sol-gel Si-C precursor: Dissolve 135g of tetraethyl orthosilicate (TEOS) in 170ml of ethanol. Furthermore, a solution of 60 g of sucrose was prepared in 75 mL of distilled water at 60 °C and diluted with HCl (1 M). 37.15 ml was added dropwise as a catalyst to form invert sugar. The mixture was mixed together under stirring and allowed to cool. The ratios 1 / 6.5 / 0.3 / 0.06 have proven to be advantageous. The range of these (individually or all together) may vary by + / - 10% and still be within the scope of the present invention. Alternatively, instead of a sucrose solution, a liquid Sugar (invert sugar, 122g 70%) can also be used directly. No water is then added. Although the addition of HCl (5.2 mL 1M) was also very small, these additions were not sufficient to induce gelation. This is only necessary to start the process.

[0050] The obtained sol is dried for 48 hours at 60°C, and then heated at 100 to 160°C, preferably The dried black coarse granules ("Ki") were then dried at 150°C for 24 hours. The cellogel was then sintered at 1100°C for 15 hours under argon, and if necessary The molar ratio of C / Si in the granules was 3.6. This ratio is particularly preferred. However, pure phase 3C-SiC according to the present invention can also be obtained in the range of 3.2 to 4.0 C / Si. Outside this range, various heterogeneous phases such as molten SiO2, carbon residues, and other SiC are formed in the final product. Graphene residues may also be formed on the surface of the material according to the invention. Kettner et al. (supra) used varying amounts of starting materials relative to the method described therein. The reaction conditions were also varied to obtain a mixed phase (see supra, Chapter 3.1 and and Chapter 3.2).

[0051] 1.2. SiC production from precursors The granules were then sintered at 1800 °C for 5 h, with the heating rate from 1000 °C to 1800 °C being The temperature gradient was 100°C / min, followed by cooling to room temperature (25°C) within 30 minutes. The grain size of the nanoparticle pure phase and stoichiometric 3C-SiC thus obtained is Particles: 40-100 nm, D 90 The value is 63 nm (+ / - 1 nm), and for secondary particles it is 1 ~10μm, D 90 The value was 8 μm.

[0052] The size of the primary particles varies depending on the heating rate (heating rate of change) and the duration of the temperature treatment at 1800°C. Particularly large primary crystallites with a size of 80 to 100 μm may be advantageously controlled by can be obtained by heating the granules more slowly, e.g., sintering at 10°C / min for 8 hours. If the heating rate is fast and the temperature treatment at 1800°C is short, the resulting primary crystallites will be small. It was found that, in principle,

[0053] Example 2 Fabrication of doped nanoparticulate silicon carbide (3C-SiC) The fabrication is carried out in the same way as for undoped SiC. However, the addition of sucrose Before this, the compound corresponding to the dopant element(s) or pure element(s) is heated to 60°C. The procedure is otherwise the same as in Example 1. The applied sol is partially colored depending on the dopant element / compound.

[0054] The amount of dopant compound / element was 5% in each case relative to 1M Si.

[0055] The doped SiC thus obtained exhibits in both cases EPR (electron paramagnetic) The results were investigated by resonance spectroscopy and XRD.

[0056] In this case, the following doped 3C-SiC nanoparticles were obtained:

[0057] 2.1 3C-SiC:Al (5at%Al relative to Si) Aluminum acetylacetonate By adding setonate or elemental aluminum, a deep blue 3C-SiC:Al was obtained. Obtained.

[0058] Figure 1 shows an SEM image of 3C-SiC:Al. Aggregates consisting of are clearly recognizable.

[0059] FIG. 2 shows an EDX trace of 3C-SiC:Al according to the present invention. The Si and Al reflections are It is clearly recognizable.

[0060] 2.2 3C-SiC:P (5at%P relative to Si) potassium dihydrogen phosphate added This was obtained by

[0061] 2.3 3C-SiC-N (5at%Al relative to Si) by adding nitric acid A deep blue 3C-SiC:N was obtained.

[0062] Figure 3 shows an SEM image of 3C-SiC:N. The primary particles (primary crystallites) and their Aggregates consisting of these are clearly recognizable.

[0063] 2.4 3C-SiC-B Obtained by adding boron acetylacetonate It was.

[0064] 2.5 3C-SiC-Er By adding erbium acetylacetonate This was obtained.

[0065] Example 3 Thin film electrodes having 3C-SiC:Al and 3C-SiC:N as active materials are used, for example, Anderson et al., Electrochem. and Solid State Letters 3 (2) 2000, pages 66-68 The electrode composition was typically prepared as described. 30 parts by weight of per P carbon and 2 parts by weight of polyvinylidene fluoride (Solvay 21216) as a binder From this electrode composition, the suspension was dissolved in N-methyl-2-pyrrolidone. The solid content of the slurry was 11.5%.

[0066] The electrode suspension is dispensed to a height of approximately 200 μm using a doctor blade (squeegee). Then, N-methylpyrrolidone was evaporated under vacuum at 105°C. A thickness of 20 to 25 μm was obtained. The dried electrodes were wrapped around several times or compressed with appropriate pressure until they were completely covered. (diameter 13 mm) and press it at 5 tons (3.9 tons / cm 2 ) pressure of 20 The mixture was compressed at room temperature for 2 seconds.

[0067] The electrodes were then dried overnight at 120°C under vacuum and placed in an argon-filled glow plug. The electrode was attached to lithium metal in a half-cell in a box and electrochemical measurements were performed. The electrode charge was 0.7 mg / cm for SiC:N. 2 Regarding SiC:Al 4.6mg / cm 2 It was.

[0068] Electrochemical measurements were performed using an electrolytic solution against lithium metal (lithium counter and reference electrodes). The assay was carried out using LP30 (Merck, Darmstadt) as a substrate (EC (Ethylene Carbonate: DMC (dimethyl carbonate) = 1:1, 1M LiPF6). The method is CC mode, i.e., Li / Li + Voltage limit 0.05V~2.0V The active material was 3C-Si. Electrodes with C:Al obtained reversible capacitances between 400 and 500 mAh / g. Upon delithiation, a so-called plateau was observed at 0.4 V vs. Li (Fig. 4). The electrode contained 2.6 mg of 3C-SiC:Al as the active material. The total measurement time was 19 It was 0 hours.

[0069] The following two cycles were measured: [Table 1]

Claims

1. Nanoparticle silicon carbide SiC in the form of secondary particles, the secondary particles being composed of aggregates of SiC primary particles, the primary particles having an average particle size in the range of 5 to 100 nm, the secondary particles having an average particle size of 1 to 10 μm, and the SiC existing as a single phase or a mixture thereof in a crystalline structure comprising 6H—SiC, 4H—SiC, or 15R—SiC.

2. 2. The nanoparticulate silicon carbide SiC of claim 1, wherein the primary particles have an average particle size in the range of 40 to 100 nm.

3. Nanoparticulate silicon carbide SiC according to claim 1 or 2, wherein the agglomerates have a bulk density of 1200 to 1600 g / l.

4. The aggregates have a density of 1500 to 3000 g / l (1.5 to 3 g / cm ３ 4. Nanoparticulate silicon carbide SiC according to any one of claims 1 to 3, having a pressed density of

5. 5. Nanoparticle silicon carbide SiC according to any one of claims 1 to 4, wherein the nanoparticle silicon carbide SiC has a powder resistivity of less than 28 Ω cm.

6. 6. Nanoparticulate silicon carbide SiC according to any one of claims 1 to 5, wherein the SiC is doped with an element selected from Mg, Nb, Zr, B, Cr, V, Sc, Y, Al, N, P, La, Er and Ga, and mixtures thereof.

7. 7. Nanoparticulate silicon carbide SiC according to claim 6, wherein the elements are B and / or Al, or N and / or P.

8. Nanoparticulate silicon carbide SiC according to any one of claims 1 to 7, wherein the SiC is further present in a 3C crystal structure.

9. Use of nanoparticulate silicon carbide SiC according to any one of claims 1 to 8 as an electrode in a secondary lithium ion battery.

10. An electrode for a secondary lithium ion battery containing the nanoparticle silicon carbide SiC according to any one of claims 1 to 9 as an active material.

11. The density of the active material of the electrode is 1.5 to 3 g / cm ３ 11. The electrode of claim 10, wherein:

12. 12. The electrode according to claim 10 or 11, wherein the electrode is an anode.

13. The electrode of claim 12 wherein the SiC is doped using N or Al.

14. 14. The electrode of claim 13, wherein the electrode doped with Al has a plateau at 0.4V + / - 0.05V vs. Li.

15. A secondary lithium ion battery comprising the anode of claim 13 or 14.

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