carbon particles

Abstract

Carbon particles comprising at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.08 wt% boron, based on the total weight of the carbon particle, and at most 0.05 wt% boron carbide, based on the total weight of the carbon particle.

Description

REFERENCE TO RELATED REGISTRATION

[0001] This application claims priority over the preliminary US patent application No. 63 / 406,932, filed on September 15, 2022, the disclosure of which is hereby incorporated in its entirety by reference. BACKGROUND OF THE INVENTION

[0002] The invention relates to a carbon particle, a method for its production and its use as an active material of a negative electrode for a battery.

[0003] Carbon-like materials can electrochemically store and release lithium ions, which is why they have been investigated as active materials for negative electrodes in lithium-ion batteries, with these electrodes often being referred to as anodes according to their function during battery discharge.

[0004] In particular, it has been found that graphite, a crystalline, layered allotropic modification of carbon, offers both a high specific capacity and a low discharge potential, close to those of metallic lithium, enabling batteries with high energy density. Furthermore, these graphitic anode materials have been developed in various forms that make lithium-ion batteries commercially valuable in terms of safety, lifespan, and charge-discharge cycle frequency. Therefore, graphite is currently the most widely used active material for lithium-ion secondary batteries.

[0005] The distance between two adjacent lattice planes in graphite is given by the d 002 -value described, which is obtained from X-ray powder diffraction measurements. The d 002 The -value is often also referred to as the interlayer spacing. A lower d 002-Value is usually associated with a higher specific capacity.

[0006] We use the Bragg equation in the form: 2⋅dhkl⋅sin(θn)=n⋅λ, wherein: • d hkl = Distance between grid planes • λ = wavelength of the X-ray beam, • n = diffraction order, and • θ n = Bragg angle for diffraction of the nth order.

[0007] In graphite, the hexagonal variety is the predominant stacking variant, for which the following applies: 1 / dhkl2=(4 / 3⋅(h2+k2+h⋅k)+l2⋅(a / c)2)⋅1 / a2

[0008] In this context, c = 2 · d 002 and a is the length of a diagonal in the constituent hexagon in the graph layer, for which a = 2 · d 110 .

[0009] Impurities, particularly sulfur and oxygen, in graphite and its respective precursor material often negatively affect the specific capacity that can be obtained from a given graphite sample. The size and shape of the particles can also influence the specific capacity achievable with a given graphite sample, with the primary parameter affected by typical particle size being the anode's performance.

[0010] To meet the requirements for high specific capacity for battery applications, natural graphite must be shaped, cut, and purified. Synthetic graphite, usually produced from coke in a process called graphitization, is also used as the active material for negative electrodes. Graphitization, in which the previously amorphous carbon is at least partially crystallized and some impurities are removed, is typically carried out in the absence of an oxidizing atmosphere at high temperatures exceeding 1700 °C and preferably 2500 °C. These high temperatures are usually achieved by resistance heating, in which a strong electric current is passed through the carbon-like material.Graphitization is considered to occur by means of temperature over a certain period of time, whereas at lower temperatures the period required to achieve a sufficient degree of graphite formation becomes counterproductive for a commercially valuable process.

[0011] Historically, the so-called Acheson process has been used, which requires batch processing and large amounts of energy. The disadvantages of the Acheson process include long cooling times, inconsistent product properties, limited control of the atmosphere, limited purification effectiveness, and large quantities of byproducts. These disadvantages necessitate a very high treatment temperature over a long period.

[0012] The initial charging of a lithium-ion secondary battery is typically referred to as "formation." During the formation of a lithium-ion secondary battery containing a graphite anode as the active material, the non-aqueous solvent or additives in the electrolyte are reduced and decomposed at the graphite surface, forming a solid electrolyte interface (SEI) layer. This process consumes not only organic molecules but also lithium ions, which are irreversibly lost to the formation of various lithium salts within the SEI layer.

[0013] The stability of the SEI layer itself and the surface (and consequently the mass) of the graphite particles themselves over many charge-discharge cycles and during storage is one of the properties that is crucial for the commercial value of the battery system.

[0014] To reduce the extent of lithium loss in the first cycle and stabilize the SEI layer over many cycles, the graphite particles that make up the anode can be modified, for example, by influencing their chemical surface activity. It has proven advantageous to coat the particles with a less reactive layer before exposure to an electrolyte. However, the application of this coating, its subsequent treatment, and final treatment (often involving a second heat treatment at a lower temperature or an additional second coating via CVD or another technology) must be carefully performed to successfully integrate the particles into the overall battery system.

[0015] Several attempts have been made in the search for a material that reliably, simply, and cost-effectively combines solutions for the many requirements of a lithium-ion battery. One very interesting concept involves doping carbon with its natural alloying partners, namely boron and nitrogen. However, the success of the solutions presented in the literature so far has been limited.

[0016] Challenges of this approach include the distribution of the alloying element source, which is often located in the coke precursor. This can lead to impurities affecting the graphitization potential, similar to sulfur, for example, or to the presence of a separate powder that can negatively impact the integrity of the graphite particles. Slow heating and cooling rates can also lead to the formation of undesirable structures, as discussed below.

[0017] An example of coated carbon particles is mentioned in US 6 869 546 B1, which describes a carbon material comprising a first carbon material serving as an inner core particle with an outer surface, and a coating of a second carbon material on this outer surface of the first carbon material, wherein the second carbon material contains at least 1 wt.% up to 15 wt.% boron.

[0018] Boron and nitrogen can partially replace carbon in a graphite structure. Boron and nitrogen can occur in natural graphite (not necessarily in substitutional positions in the graphite layer) and are sometimes intentionally added in the production of synthetic graphite because boron has been shown to accelerate the crystallization of carbon to graphite during high-temperature treatment, thus allowing for a lower treatment temperature.

[0019] Synthetic graphitic carbon materials containing boron and / or nitrogen have been reported.

[0020] For example, US 5 358 805 A describes a secondary battery comprising a positive electrode, an electrolyte and a negative electrode capable of reversibly storing lithium, wherein this negative electrode comprises a carbon compound with a crystal structure like graphite in which carbon (C) is partially replaced by both boron (B) and nitrogen (N), and wherein this carbon compound has the formula BC3N.

[0021] In particular, it has been hypothesized that introducing boron and / or nitrogen into the surface of carbon particles improves their surface chemistry. Adding boron and nitrogen during graphitization can be used to integrate these elements into the carbon surface, thereby improving the formation and stabilization of the SEI layer. However, in addition to boron and nitrogen doping, this can also lead to the formation of a boron nitride surface coating. While a boron nitride coating can increase the chemical stability of the graphite, its insulating properties negatively affect lithium ion diffusion and the interaction between the SEI layer, the electrolyte, and the surface of the anode particles. Therefore, monitoring and adjusting the boron nitride content is of great importance.In this respect, US 2018 / 0337423 A1 describes an active material for a negative electrode comprising boron and nitrogen-containing graphite and an X-ray photoelectron spectroscopy (XPS) technique that can be used to monitor the ratio of peak area of ​​nitrogen-bound boron to peak area of ​​total boron, taking into account the boron-1s spectrum in each case.

[0022] Furthermore, JP 2000 012020 A describes a material for a negative electrode of a lithium-ion secondary battery, which is graphitized carbon powder containing boron and nitrogen, where the 10% cumulative diameter (d) 10 ) of the carbon-like powder is 5 to 25 µm.

[0023] In JP 2000 12021 A, a material for a negative electrode of a lithium-ion secondary battery is described, comprising graphitized carbon powder containing boron and nitrogen, with a specific surface area calculated by desorption of nitrogen from the carbon powder of 10 m². 2 / g or less.

[0024] US 2001 / 0051300 A1 describes a surface treatment after graphitization that results in a graphite powder containing 0.01 to 5.0 wt% boron and having a closed loop structure at one end of a C-planar graphite layer on the surface of a powder, wherein the density of the planar interstices between adjacent closed structures is not less than 100 / µm and not more than 1500 / µm.

[0025] Similar to boron nitride, boron carbide can form during graphitization, but it is not limited to the particle surface. However, boron carbide is disadvantageous because it can act like an abrasive when boron carbide-containing particles in a coating come into contact with another surface, such as a metal foil. Furthermore, boron carbide is essentially non-reactive, which reduces the gravimetric and volumetric capacity of the particles.

[0026] Referring to the prior art, the present invention is based on the objective of providing carbon particles that can be used for anodes of lithium-ion batteries. In particular, the carbon particles should result in anodes and / or batteries with long shelf life and / or high specific capacity and / or many cycles.

[0027] A further object of the invention is to provide a method for producing such carbon particles. This method should, in particular, allow the production of particles with tailored properties and preferably eliminate or at least limit the disadvantages of doping with boron and nitrogen known from other approaches.

[0028] Other and further tasks, features and advantages of the present invention can be found in more detail in the following description. GENERAL DESCRIPTION OF THE INVENTION

[0029] Some or all of the foregoing problems are solved by the carbon particle according to claim 1, the method according to claim 12, the use according to claim 19 and the battery according to claim 20.

[0030] Without adhering to any scientific theory, it is assumed that impurities in the carbon particles can affect the electrochemical properties and the crystallinity of the graphite, which is why their removal during the graphitization process may be advantageous. Furthermore, impurities of a metallic nature, in particular, increase the risk of promoting side reactions in the battery's chemical system, which poses a risk to battery performance, shelf life, and cycle life.

[0031] In contrast, boron can be advantageous with respect to these properties; however, it is assumed that the formation of boron carbide clusters renders the boron inactive, and it is known that macroscopic crystals are abrasive, which is why boron carbide formation should be prevented. Surprisingly, it has now been found that the granulation of carbon-like particles by an organic binder, subsequent carbonization, and finally graphitization in an electric field, particularly in an electrothermal fluidized bed, with subsequent deagglomeration of the granules, especially by weak mechanical fragmentation, to recover the particles, can allow the use of a wide range of precursor particle sizes and results in particles with a graphitized core and an unstructured carbon shell.In this way, numerous advantages of doping with boron and nitrogen can be combined, while its potential disadvantages, known from other approaches, can be avoided or at least limited.

[0032] The process can allow the controlled introduction of boron and nitrogen as dopants into the particle mass and surface, and likely limit the formation of boron carbide and boron nitride. The carbon particles according to the invention can be used as active negative electrode material for lithium-ion secondary batteries, especially in their anodes. The resulting batteries can, in particular, possess a long storage life and / or high specific capacity and / or a high cycle life. Without being bound to any scientific theory, it is assumed that the carbon particles, which contain boron only in very small clusters, help to obtain anodes and / or batteries with desirable properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In: - Fig.Figure 1 is a diagram illustrating the relationship between boron substitution and the degree of graphite formation. - Fig. 2 is part of an XPS spectrum of a natural flake graphite that was purified and boronized in an electrothermal fluidized bed reactor under a nitrogen atmosphere in the presence of a boron source at a black radiation temperature of about 2300 °C and a residence time as described in Examples 1-6 below; the boron nitride was mechanically removed from the surface using a belt, and - Fig. Figure 3 shows particle size distributions of different particles. SPECIAL DESCRIPTION OF THE INVENTION

[0034] Subsequently, embodiments of the invention are described in detail. However, the present disclosure is not limited to these embodiments.

[0035] According to one embodiment, the carbon particle has a BET surface area of ​​0.5 to 50 m². 2 / g, preferably from 0.5 to 10 m 2 / g, especially preferably from 1 to 3 m 2 / g, and even more preferably from 1 to 2 m 2 The BET surface area is preferably determined by nitrogen adsorption-desorption processes. An optimized specific surface area is important for graphite as an active material in anodes for lithium-ion batteries, since a larger specific surface area can be associated with higher irreversible lithium loss during SEI formation, while a smaller specific surface area can be associated with lower anode conductivity and performance. Carbon particles with a BET surface area such as that described herein can, in particular, exhibit a good balance between lithium loss and conductivity.

[0036] According to another embodiment, the carbon particles possess a d 002 -Spacing from 0.3363 nm to 0.3355 nm and preferably from 0.3359 nm to 0.3355 nm and / or a d 110 -Spacing from 0.120 nm to 0.126 nm, preferably from 0.1229 nm to 0.1236 nm, and particularly preferably from 0.123027 nm to 0.123244 nm. A smaller d 002 associated with a larger specific capacity and a measure of the degree of graphitization and crystallinity of the carbon. The d 110 The distance is influenced by the boron dosage, with a d 110 -The spacing in the specified area may indicate a uniform distribution of boron atoms in the graphite structure, as opposed to the formation of clusters with a higher boron content.

[0037] According to one embodiment, an XPS spectrum of the carbon particle has a first peak at 184.0 eV to 188.0 eV, preferably 185.0 eV to 187.5 eV, particularly preferably 185.5 eV to 187.0 eV, and most preferably at about 186.5 eV and / or a second peak at 188.5 eV to 192.0 eV, preferably 189.0 eV to 191.5 eV, particularly preferably 189.5 eV to 191.0 eV, and most preferably at about 190.3 eV and / or essentially no peak at about 187.7 eV. Preferably, the intensity ratio in the XPS spectrum of the first to the second peak is 0.25 to 6.0, preferably 0.5 to 2, and particularly preferably 0.8 to 1.25. A large intensity ratio of the first to the second peak indicates a strong presence of BN bonds, which are typically associated with the presence of boron nitride. The first peak and / or the second peak is / are preferably significant in the XPS spectrum.The first peak in the XPS spectrum is preferably a B1s peak, indicating the presence of boron-carbon bonds on the surface of the carbon particle. This first peak in the XPS spectrum can also be referred to as the B1s(BC) peak. The second peak in the XPS spectrum is preferably a B1s peak, indicating boron-nitrogen bonds on the surface of the carbon particle. This second peak in the XPS spectrum can also be referred to as the B1s(BN) peak. The peak at 187.7 eV is preferably a B1s peak, indicating boron-boron bonds and / or boron-boron clusters. Preferably, the peak at 187.7 eV is below the detection limit.

[0038] In the XPS spectrum, to demonstrate the presence of nitrogen in the hard carbon shell, the boron nitride is treated mildly with NaOH. aq(10% NaOH, 20 min at 250 °C in an Anton Paar Multiwave 7000 microwave digestion unit using a PTFE probe tube, followed by neutralization with nitric acid). The remaining BN peak at approximately 190.3 eV indicates doped nitrogen in the shell of the carbon particles, which improves the surface properties of the particles.

[0039] According to another embodiment, the carbon particle contains at least 97.5 wt.%, preferably at least 98 wt.%, and particularly preferably at least 98.5 wt.% carbon, based on the total weight of the particle. A higher carbon content may indicate a greater proportion of active material capable of incorporating lithium into anodes manufactured from it, which can result in a higher specific capacity. Furthermore, a higher carbon content may indicate a lower content of impurities, which can have various adverse effects.

[0040] According to a preferred embodiment, at least 85 wt.%, particularly preferably at least 90 wt.%, and most preferably at least 95 wt.% of the carbon contained in the carbon particle is graphitic carbon.

[0041] Herein, “impurities” preferably mean constituent components in the particle that are not carbon, boron, and nitrogen. Impurities can affect graphite properties, particularly with regard to crystallinity and layering of the graphite. Furthermore, impurities of a metallic nature can, in particular, promote side reactions in the chemical battery system, which poses a risk to battery control, its shelf life, and its number of cycles. The impurities initially found may depend on the source and prior processing of the precursor of the carbon-like material. Preferably, the carbon particles disclosed herein contain a small proportion of impurities. According to one embodiment, the carbon particle contains at most 0.1 wt.%, preferably at most 0.05 wt.%, particularly preferably at most 0.04 wt.%, and even more preferably at most 0.03 wt.%.-%, and most preferably not more than 0.025 wt% impurities, based on the total weight of the carbon particle.

[0042] According to yet another embodiment, the impurities are at least one metallic impurity such as transition metals, in particular vanadium and / or iron, oxygen, and sulfur, preferably at least one of the transition metals, in particular vanadium and / or iron, oxygen, and sulfur. Preferably, the carbon particles contain at most 100 ppm oxygen and 100 ppm sulfur. The oxygen content and the total nitrogen content were determined using a Leco ONH836 elemental analyzer, the sulfur content using a Leco SC 432 sulfur analyzer, and vanadium, iron, and other elements, in particular metals, using a Jobin Yvon Horiba Ultima 2 ICP-OES after a nitric-sulfuric acid digestion (for vanadium and other metals) or a hydrochloric acid digestion (for iron).

[0043] According to yet another embodiment, the carbon particle contains at most 0.03 wt.%, preferably at most 0.02 wt.%, particularly preferably at most 0.01 wt.%, and most preferably at most 0.005 wt.% boron carbide, based on the total weight of the carbon particle, and / or the carbon particle contains at most 0.5 wt.% boron nitride, preferably at most 0.3 wt.% boron nitride, and particularly preferably at most 0.1 wt.% boron nitride, based on the total weight of the carbon particle. The carbon particle may also contain boron nitride, in particular in a content of 0.05 wt.% to 1 wt.%, and preferably in a content of 0.1 wt.% to 0.8 wt.%, based on the total weight of the carbon particle. If present, boron nitride is preferably located on the surface of the carbon particle.It has been found that boron and / or nitrogen present in carbon particles with concentrations within the aforementioned ranges can reduce the formation of dopant-rich clusters, phases, particles, and / or surfaces. Dopant-rich clusters, phases, particles, and / or surfaces can reduce the carbon particle's ability to absorb and release lithium, or may even contribute to irreversible lithium loss through side reactions. Furthermore, boron carbide can act as an abrasive when a suspension containing carbon particles is applied to a copper foil to create a negative electrode for a battery. Additionally, boron carbide is essentially unreactive, thus reducing the gravimetric and volumetric capacity of a negative electrode.

[0044] Boron can be present in carbon particles in different forms. For example, boron can exist as boron nitride. Boron nitride is preferentially located on the surface of the carbon particles. Boron can also exist as boron carbide.

[0045] Boron nitride can be produced by treating the carbon particles with NaOH to dissolve them. aq The boron nitride can be extracted at temperatures up to 250 °C in an Anton Paar Multiwave 7000 microwave digestion unit. The residue from the alkaline treatment can be used to quantify the boron nitride by performing ICP / OES on the boron.

[0046] The upper limit of the boron carbide content can be determined as follows: During the XRD measurement of the degree of graphite formation, the diffractogram can be examined for boron carbide reflections. The ash of the carbon particle samples (3 g sample, 8 hours at 780–800 °C in a muffle furnace under air) can then be visually examined for boron carbide particles. The ash has a white color; boron nitride stands out as white particles, and boron carbide stands out as gray to black speckles in the ash. The upper limit of the boron carbide in the carbon particles can then be determined by comparing the proportion of gray to black boron carbide speckles in the ash with the proportion of white boron nitride particles, with the boron nitride proportion being determined by performing ICP-OES as described herein. XRD analysis of the ash can also be performed as an additional control.

[0047] Furthermore, boron can also exist in place of a carbon atom. For example, if the carbon particle contains a graphene layer, a graphite crystallite, or amorphous carbon structures, a boron atom can occupy a lattice position within the graphene layer or graphite crystallite and replace the carbon atom in that lattice position, or the boron atom can replace a carbon atom in the amorphous carbon structure. In this case, the boron is also said to be in a substitutive position.The proportion of boron in a substituting position in the carbon particles can be determined in particular by the following steps: First, 3 g of sample are ashed for eight hours at 780-800 °C in a muffle furnace under air; second, the boron oxide is dissolved from the ash in hot 2% nitric acid; then, the boron nitride is filtered from the ash to obtain a nitric acid filtrate; and third, the boron content in the nitric acid filtrate is determined by performing an ICP-OES.

[0048] The carbon particle contains at least 0.08 wt% boron, based on the total weight of the carbon particle. According to one embodiment, the carbon particle contains at least 0.1 wt%, preferably at least 0.15 wt%, particularly preferably at least 0.2 wt%, and even more preferably at least 0.3 wt% boron, based on the total weight of the carbon particle, and / or at most 2.3 wt%, preferably at most 2 wt%, particularly preferably at most 1.5 wt%, and most preferably at most 1.3 wt%, based on the total weight of the carbon particle. According to a preferred embodiment, the carbon particle contains 0.1 wt% to 2 wt%, and particularly preferably 0.3 wt% to 1.5 wt% boron. The aforementioned boron contents of the carbon particle preferably apply to boron in a substitutive position within the carbon particle.By using a carbon particle with a boron content within the ranges described herein, especially with such a boron content in a substituting position, the formation of by-products not involved in the incorporation or release of lithium ions can be suppressed and a high specific discharge capacity can be maintained.

[0049] According to one embodiment, the carbon particle contains both boron nitride and boron, preferably with a weight ratio of at least 0.0005 weight percentage points boron nitride per weight percentage point boron up to a maximum of 2.5 weight percentage points boron nitride per weight percentage point boron, particularly preferably with a weight ratio of at least 0.001 weight percentage point boron nitride per weight percentage point boron up to a maximum of 1 weight percentage point boron nitride per weight percentage point boron, and even more preferably with a weight ratio of at least 0.002 weight percentage points boron nitride per weight percentage point boron up to a maximum of 0.1 weight percentage point boron nitride per weight percentage point boron.

[0050] According to one embodiment, the carbon particle contains both boron nitride and boron, preferably with a weight ratio of at least 0.02 (wt% boron nitride / wt% boron) to at most 12.5 (wt% boron nitride / wt% boron), particularly preferably with a weight ratio of at least 0.05 (wt% boron nitride / wt% boron) to at most 1 (wt% boron nitride / wt% boron), and even more preferably with a weight ratio of at least 0.07 (wt% boron nitride / wt% boron) to at most 0.3 (wt% boron nitride / wt% boron).

[0051] According to another embodiment, the carbon particle contains nitrogen. Advantageously, the carbon particle contains nitrogen, particularly in a proportion of at least 0.005 wt.%, preferably 0.01 to 0.05 wt.%, more preferably 0.015 to 0.04 wt.%, and most preferably 0.02 to 0.03 wt.%, based on the total weight of the carbon particle. The aforementioned nitrogen content of the carbon particle is preferably determined after the boron nitride has been removed from the surface of the carbon particle. Nitrogen doping within the ranges mentioned herein can help to reduce the formation of byproducts that are not involved in the incorporation or release of lithium ions and in maintaining a high specific discharge capacity. The nitrogen content after removal of the boron nitride from the carbon particle can be determined by XPS after removal of the boron nitride.

[0052] According to a preferred embodiment, the carbon particle contains boron and nitrogen. Advantageously, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.08 wt% boron, based on the total weight of the carbon particle, at most 0.05 wt% boron carbide, based on the total weight of the carbon particle, and nitrogen. The boron is preferably in a substitutive position within the carbon particle.

[0053] According to a further preferred embodiment, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.15 wt% boron, based on the total weight of the carbon particle, and at most 0.05 wt% boron carbide, based on the total weight of the carbon particle. The boron is preferably in a substitutive position within the carbon particle.

[0054] According to another preferred embodiment, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.15 wt% boron, based on the total weight of the carbon particle, at most 0.05 wt% boron carbide, based on the total weight of the carbon particle, and nitrogen.

[0055] According to yet another preferred embodiment, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.15 wt% boron, based on the total weight of the carbon particle, at most 0.05 wt% boron carbide, based on the total weight of the carbon particle, and at least 0.0003% nitrogen and at most 1% nitrogen.

[0056] According to yet another preferred embodiment, the carbon particle contains at least 97 wt.% carbon, based on the total weight of the carbon particle, at most 0.2 wt.% impurities, based on the total weight of the carbon particle, at least 0.15 wt.% boron, based on the total weight of the carbon particle, at least 0.0001 and at most 0.05 wt.% boron carbide, based on the total weight of the carbon particle, and nitrogen, and the carbon particle is preferably a core-shell particle, in particular with a shell made of hard carbon.

[0057] According to a further preferred embodiment, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, and at least 0.08 wt% boron, based on the total weight of the carbon particle. at most 0.05 wt% boron carbide, based on the total weight of the carbon particle, nitrogen and Boron nitride wherein boron nitride and boron are present in a weight ratio of at least 0.0005 weight percentage points boron nitride per weight percentage point boron to 2.5 weight percentage points boron nitride per weight percentage point boron.

[0058] According to another preferred embodiment, the carbon particle contains at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.08 wt% boron, based on the total weight of the carbon particle, and at most 0.05 wt% boron carbide, based on the total weight of the carbon particle. nitrogen and Boron nitride and has a boron nitride / boron weight ratio of at least 0.02 (wt% boron nitride / wt% boron) to at most 12.5 (wt% boron nitride / wt% boron).

[0059] According to yet another embodiment, the carbon particles have a particle size distribution d 50 from 3 to 30 µm, preferably from 4 to 25 µm, and particularly preferably from 5 to 20 µm. Advantageously, the carbon particles have a particle size distribution d 10 from 1 to 25 µm, preferably from 1.5 to 20 µm, and particularly preferably from 2 to 15 µm. Advantageously, the carbon particles have a particle size distribution d 90from 6 to 50 µm, preferably from 8 to 45 µm, and particularly preferably from 10 to 35 µm. While particles smaller than specified may irreversibly consume excess lithium due to SEI formation and exhibit reduced specific capacity, particles larger than specified may suffer from slow lithium incorporation and release, resulting in low anode performance. Particles outside the specified size distribution may also negatively affect anode production, leading to anodes of poor manufacturing quality.

[0060] All particle size distributions described herein are preferably volumetric and were determined by moist dispersed laser diffraction using a Microtrac S3500 after dispersion by ultrasound in a Branson 3510 ultrasonic bath using a Branson Sonifier 250-Ultrasonic probe with the surfactant Triton X100.

[0061] According to yet another embodiment, the carbon particle is a core-shell particle comprising a substantially non-graphitizable, particularly hard, carbon shell and a carbon core that is at least partially graphitized and may still contain graphitizable, particularly soft, carbon components. Without being bound to any scientific theory, it is assumed that a hard carbon shell reduces the irreversible lithium loss through SEI formation and / or side reactions and / or protects the inner surface of the particle core from similar side reactions, particularly co-incorporation of an electrolyte, which would result in particle degradation. Simultaneously, it is assumed that the shell is sufficiently conductive to lithium ions that the lithium incorporation properties of the core are not impaired.

[0062] In the core-shell particles, the core advantageously contains 91 wt.% to 99 wt.%, preferably 92 wt.% to 99 wt.%, and particularly preferably 94 wt.% to 98.5 wt.% of the total weight of the carbon particle, and the shell contains 1 wt.% to 9 wt.%, preferably 1 wt.% to 8 wt.%, and particularly preferably 1.5 wt.% to 6 wt.% of the total weight of the carbon particle.

[0063] The shell is preferably formed from a carbonized binder.

[0064] The carbon particles disclosed herein are obtainable by a process in which In a granulation step, carbon-like particles are granulated using a binder to produce carbon-like granules. In a carbonization step, the carbon-like granules are heated to a temperature of at least 1000 °C to produce carbonized granules. In a graphitization step, the carbonized granules are introduced into an electric field to carry out the graphitization of the carbonized granules, resulting in graphitized granules, and In a deagglomeration step, the graphitized granules are deagglomerated, resulting in the carbon particles. wherein at least one of the granulation step, carbonization step and graphitization step is carried out in the presence of a boron source.

[0065] After the graphitization step, the graphitized granules preferably contain the carbon particles in an adhering form. In the deagglomeration step, the particle-particle contacts of the carbon particles in the graphitized granules are preferably broken up in order to deagglomerate the graphitized granules. Advantageously, the carbon particles themselves are not substantially broken down into smaller carbon particles. The deagglomeration of the graphitized granules is preferably carried out mainly by shear forces. The deagglomeration step can thus be described as a mechanical comminution step.

[0066] The carbon-like particles can exhibit a particle size distribution d 50 The particles have a particle size distribution of 3 to 30 µm, preferably 4 to 25 µm, and particularly preferably 5 to 20 µm. Advantageously, the carbon-like particles have a particle size distribution d 10from 1 to 25 µm, preferably from 1.5 to 20 µm, and particularly preferably from 2 to 15 µm. Advantageously, the carbon-like particles have a particle size distribution d 90 from 6 to 50 µm, preferably from 8 to 45 µm, and particularly preferably from 10 to 35 µm.

[0067] Preferably, the carbon-like particles are selected from unprocessed petroleum coke particles, calcined petroleum coke particles, spherical flake graphite particles, spherical natural graphite particles, recycled anode powder particles, petroleum coke, pitch coke, charred wood, needle coke, sponge coke, shot coke, metallurgical coke, coal tar-based carbon, mesocarbons, anthracite, synthetic graphite, natural graphite, expanded graphite, carbonized polymers, soot and mixtures thereof, and preferably from unprocessed petroleum coke particles, calcined petroleum coke particles, spherical flake graphite particles, spherical natural graphite particles, recycled anode powder particles and mixtures thereof.The process can accommodate a wide range of precursor particle sizes when granules are formed from particles and binder in the granulation step, resulting in particles with the appropriate size distribution for processing in subsequent steps and later use, particularly as active material in lithium-ion battery anodes. Similarly, the process can allow for a wide range of precursor materials because impurities can be removed during the process.

[0068] According to another embodiment, the binder comprises at least one of the following: starch, modified starch, phenolic resins, modified kraft lignin, styrene-butadiene rubber (SBR), and latex. Preferably, the binder contains or consists of starch and / or modified starch. These materials are readily available, inexpensive, and, due to their composition, can be carbonized in the carbonization step described above. Simultaneously, the granulation step can be carried out with these binders, preferably using water as a solvent, under advantageous conditions. However, the invention is not dependent on a specific choice of such a binder. The binder preferably facilitates the agglomeration of the fine carbon-like powder, particularly into carbon-like granules. Advantageously, each carbon-like particle receives a coating of binder.Preferably, the particles are bonded together by the binder to form granules. In this way, the carbon-like granules can yield carbonized granules after the carbonization step, which are preferably strong enough to pass through the electrothermal fluidized bed reactor essentially without mechanical disintegration, but still allow for deagglomeration by mild mechanical treatment. Furthermore, in this way, the individual carbon particles preferably retain an intact carbonized coating, in particular a hard carbon shell. Suitable binders for this purpose include, but are not limited to, binders containing starch, modified starch, phenolic resin, modified kraft lignin, styrene-butadiene rubber (SBR), or latex.

[0069] Preferably, the binder is used in a proportion of 3 to 25 wt.% and particularly preferably of 5 to 20 wt.%, based on the total weight of carbon-like particles and binder.

[0070] If a solvent, for example water, is used, the solvent is used in a proportion of 10 to 30 wt.% and particularly preferably 15 to 25 wt.%, based on the total weight of binder and carbon-like particles.

[0071] In the carbonization step, the carbon-like granules can be heated in a first heating step to a temperature of 30 °C to 700 °C, preferably 30 °C to 300 °C, and subsequently in a second heating step to a temperature of 300 °C to 1400 °C, preferably 300 °C to 1300 °C, and particularly preferably 300 °C to 1100 °C. This step may require careful calcination within the production line using prior art procedures to produce graphitizable carbon and to achieve optimal process results and properties. Both heating steps can be carried out batchwise or continuously and in one furnace or in separate furnaces, with or without pretreatment of the granules.

[0072] The carbon-like granules can be heated to the first temperature for a period of 0.1 to 20 hours, and preferably 0.25 to 12 hours, and / or to the second temperature for a period of 0.1 to 20 hours, and preferably 0.25 to 12 hours. The carbonization time can depend on the furnace used for heating. If a rotary kiln is used, the carbon-like granules are advantageously heated to the first and / or second temperature for a period of 0.1 to 2 hours, and preferably 0.5 to 1.5 hours. If a furnace such as a binder removal furnace or a sintering furnace is used, the carbon-like granules are advantageously heated to the first and / or second temperature for a period of 5 to 20 hours, preferably 10 to 15 hours, and particularly preferably 10 to 12 hours.Under these carbonization conditions, the resulting carbonized granules can exhibit advantageous properties, particularly with regard to graphitizability in the subsequent step. The carbonization steps can be carried out in a directly or indirectly heated rotary kiln under a reducing atmosphere with less than 2 vol% oxygen, or in a directly or indirectly heated furnace chamber under a reducing atmosphere with less than 2 vol% oxygen, or in another suitable apparatus.

[0073] The graphitization step can be carried out batchwise or continuously, preferably continuously.

[0074] The carbonized granules can be introduced into an electrothermal fluidized bed reactor during the graphitization step. A suitable electrothermal fluidized bed reactor is described, for example, in US 3,684,446 or US 3,807,961. In such a reactor, the particles can be heated rapidly and directly under local plasma conditions. Compared to other reactor types, and especially the Acheson process, an electrothermal fluidized bed reactor can offer advantages in one or more aspects, including energy consumption per unit of product, product homogeneity due to mixing in the fluidized bed (even when considering boron content), continuous operation as opposed to batch operation, throughput, and / or controllability of residence time.

[0075] The graphitization step can be carried out at a temperature of at least 2000 °C, preferably at least 2300 °C, particularly preferably at least 2400 °C, and most preferably at least 2550 °C. These temperatures are, in particular, black radiation temperatures. The graphitization step is preferably carried out at a temperature of at most 3500 °C, particularly preferably at most 3200 °C, and most preferably at most 3000 °C. If the graphitization step is carried out within these temperature ranges, the formation of boron nitride can be reduced.

[0076] The mean residence time of the carbonized granules in the electric field during graphitization can be 5 to 120 minutes, preferably 10 to 90 minutes, particularly preferably 15 to 60 minutes, and most preferably 20 to 45 minutes. These specified mean residence times ensure high graphitization, purification, and boron diffusion, as well as uniform particle properties, while still allowing for a high throughput through the reactor.

[0077] The graphitized granules can be cooled to a temperature of 500 °C or lower after the graphitization step for a period of 5 to 90 minutes, preferably 10 to 60 minutes, particularly preferably 15 to 45 minutes, and most preferably 20 to 30 minutes. It is assumed that rapid cooling prevents the formation of boron clusters, such as those from boron carbide, as well as the loss of boron from the graphite lattice.

[0078] In the deagglomeration step, the particle-particle contacts of the carbon particles in the graphitized granules can be broken, advantageously by shear forces. Preferably, in the deagglomeration step, the graphitized granules are deagglomerated using a mill, in particular a mill selected from a ball mill, jet mill, hammer mill, or cone mill, preferably a jet mill. The deagglomeration of the granules yields particles in the preferred particle size distribution range for subsequent use, especially as active material in anodes for lithium-ion batteries. The length of the cutting process and the choice of mill can be adjusted depending on the particle properties and the application specifications. The aforementioned mills, especially jet mills, are very suitable for breaking the particle-particle contacts of the carbon particles.

[0079] The boron source can be selected from boron oxide, boric acid, elemental boron, and mixtures thereof, preferably boron oxide. Advantageously, the boron source is added in the granulation step or the graphitization step, preferably in the graphitization step, particularly as a separate powder for mixing and evaporation. By selecting the boron source and the boron addition step, the resulting boron content of the particle and / or shell can be influenced, especially when comparing the boron addition to the binder formulation with the addition to the fluidized bed. Furthermore, the reaction time required to achieve the desired boron distribution can be influenced.

[0080] The graphitization step can be carried out in the presence of a nitrogen source, preferably nitrogen. Gaseous nitrogen can serve as the process gas for turbulence and to prevent oxidation, as well as for doping. Argon can be used instead of nitrogen if doping with nitrogen via the fluidizing gas is undesirable. In such a case, the nitrogen source can be added during the graphitization step, for example, in the form of a urea powder.

[0081] Another aspect of the present disclosure relates to the use of a carbon particle as described herein as the active material of a negative electrode in a battery, in particular for a lithium-ion secondary battery. The anode can be produced from the active material or a mixture of active materials by coating a current collector with a mixture of active material, binder, additives and, if necessary, solvent.

[0082] Another aspect of the present disclosure relates to a battery, in particular a lithium-ion secondary battery, which contains the carbon particles described herein, in particular as the active material of a negative electrode.

[0083] The battery can be assembled with the described negative electrode and can also include a cathode containing, among other things, an active material capable of storing lithium, including but not limited to lithium iron phosphate LiFePO4, lithium cobalt oxide LiCoO2, lithium nickel oxide LiNiO2, lithium manganese oxide LiMn2O4, and related materials such as the so-called NCM materials, LiNi x Mn y Co z O2, where x + y + z = 1, or spinel structures such as LiNi 0,5 Mn 1,5The battery can reversibly store and release O4. Furthermore, it can contain a polymer or glass fiber separator and an electrolyte consisting of one or more organic solvents and a lithium salt, including but not limited to lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), or lithium tetrafluoroborate (LiBF4). The electrolyte can also contain additives, including but not limited to organic molecules such as vinylene carbonate or fluoroethylene carbonate and / or salts such as lithium difluorophosphate. The use and combination of electrolyte and additives can be selected based on the properties of the active material of the anode and cathode. Examples

[0084] Various carbon-like particles were granulated in a drum granulator using an aqueous starch solution as a binder. The starch content was 7 wt%, based on the total weight of carbon-like particles and starch binder.

[0085] The particle size distributions were determined by laser scattering with Microtrac S3500 after dispersion under sonication with ultrasound in a Branson 3510 ultrasonic bath using a Branson Sonifier 250-Ultrasonic probe with the surfactant Triton X100.

[0086] The following carbon-like particles were used: Carbon-like particle 1: Sponge coke I, d 10 : 1.7 µm, d 50 : 8.7 µm, d 90 : 23.2 µm, sulfur content 3.55 wt.%; Carbon-like particle 2: Sponge coke II, d 10 : 2.5 µm, d 50 : 10.0 µm, d 90 : 21.8 µm, sulfur content: 0.85 wt.%; Carbon-like particle 3: Needle coke I, d 10 : 6.5 µm, d 50 : 19.0 µm, d 90 : 40.7 µm, sulfur content: 0.47 wt.%; carbonaceous particle 4: needle coke II, d 10 : 2.9 µm, d 50 : 9.1 µm, d 90 : 18.7 µm, sulfur content 0.6 wt.%.

[0087] The resulting carbonaceous granules from sponge coke I + II were subsequently heated to a temperature of 1100 °C in a rotary kiln for a total residence time of 45 min, following a heat treatment at 300 °C in a rotary kiln for a total residence time of 45 min. Needle coke I + II was heat-treated to a peak temperature of 1100 °C in a batch kiln for a total batch time of 12 hours, after having been treated to a peak temperature of 650 °C for 12 hours in another batch kiln.

[0088] The resulting carbonized granules were cooled to room temperature, and 150 kg of the carbonized granules were then introduced into an electrothermal fluidized bed (EFB) reactor as described in US 3,684,446. The EFB reactor, containing nitrogen as an inert gas, was operated at a temperature of 2400 °C to 2700 °C. The carbonized granules had a mean residence time in the EFB reactor of approximately 60 minutes and were converted to graphitized granules. Between 4.5 kg and 8.5 kg of dry boron oxide were added to the EFB reactor during graphitization, depending on the desired boron doping. After exiting the EFB reactor, the graphitized granules were cooled to below 500 °C for approximately 60 minutes. The cooled graphitized granules were then passed through a jet mill, where they were deagglomerated to yield the carbon particles.

[0089] The carbon particles had the following properties. Table 1: Properties of carbon particles Example No. Coke type Degree of graphitization [%] Substituting boron content [wt.%] Boron nitride [wt.%] d 10 [µm] d 50 [µm] d 90 [µm] 1 Sponge coke I 90,6 0,59 0,33 3,8 14,5 42,9 2 Sponge coke I 90,1 0,53 0,21 3,9 15,1 32,5 3 Sponge coke I 88,6 0,34 0,12 4,1 15,8 33,0 4 Sponge coke I 88,5 0,38 0,07 3,5 14,7 32,8 5 Sponge coke II 93,7 0,54 0,19 5,8 14,7 32,2 6 Needle coke I 94,8 0,61 and 9,7 22,5 40,4 7 Needle coke II 96,0 0,34 0, 04 6,3 13,2 23,0 Example No. = example number, nd = not specified

[0090] The degree of graphitization was determined using the following formula: Degree of graphitization = (0.344 nm − d002) / (0.344 nm − 0.3354 nm)

[0091] This involves d 002 The distance between two adjacent layers in graphite, determined by X-ray radiation. Fig. Figure 1 shows the relationship between boron substitution and degree of graphitization. Fig.Figure 2 shows the XPS peaks for the BC (186.5 eV) and BN (190.3 eV) bonds and the absence of BB bonds in a carbon particle sample prepared from natural flake graphite. This sample was treated in the EFB furnace under a nitrogen atmosphere with boron oxide dosing at a black radiation temperature of 2300 °C, after removal of the boron nitride from the surface by belt sanding. The residence time and cooling time of this flake graphite sample, as well as the deagglomeration conditions, were the same as in previously described Examples 1 to 6. The peak ratio of 190.3 eV to 186.5 eV was approximately 1.1. According to the XPS measurements, the carbon particles contained boron nitride. Furthermore, the absence of a boron-boron bond peak indicated that there was essentially no boron present in the boron clusters. Fig.Figure 3 shows volumetric particle size distributions of a reference sample and the deagglomerated carbon particles of a spherical natural flake graphite powder that had been agglomerated and treated by the carbonization and EFB heat treatment process described above, followed by deagglomeration, thus demonstrating the preservation of the particle size distributions in the deagglomeration step. Deagglomeration was carried out using an air jet mill.

[0092] Table 2 shows the levels of metallic impurities, oxygen and sulfur in the deagglomerated samples. Table 2: Purity of carbon particles Needle coke I Needle coke II Sponge coke II Example No. 6 7 5 Oxygen % 0,008 0,006 0,007 Sulfur % <0,005 <0,005 <0,005 element ppm ppm ppm Co <0,6 <0,6 <0,6 Ni <0,6 <0,6 <0,6 Si 1,1 1,0 1,8 Mn <0,6 <0,6 <0,6 Fe 0,66 3,1 2,2 Mon <0,6 <0,6 <0,6 Cr <0,6 <0,6 <0,6 V 2,9 9,3 24,9 Cu <0,6 0,7 <0,6 Al <0, 6 <0,6 0, 9

[0093] Furthermore, in all examples, the carbon particles contained less than 0.2 wt% impurities, including the aforementioned metals, as well as oxygen and sulfur, based on the total weight of the carbon particles.

[0094] Furthermore, in all examples, the carbon particles contained less than 0.05 wt% boron carbide, based on the total weight of the carbon particles.

[0095] The carbon particles also contained at least 97 wt% carbon, based on the total weight of the carbon particles.

[0096] The levels of impurities (oxygen) were determined using a Leco ONH836 elemental analyzer.

[0097] The levels of impurities (sulfur) were determined using a LECO SC 432 sulfur analyzer.

[0098] The levels of impurities (of a metallic nature, see above) were determined using a Jobin Yvon Horiba Ultima 2 ICP-OES.

[0099] The boron nitride content was determined by treating the carbon particles with NaOH. aq The boron content was determined at temperatures up to 250 °C in an Anton Paar Multiwave 7000 microwave digestion device and by analyzing the residue of the alkali treatment using ICP-OES.

[0100] The boron content was determined by the following steps: First: eight-hour ashing of 3 g sample at 780-800 °C in air in a muffle furnace, Secondly: Dissolving the boron oxide from the ash in hot 2% nitric acid followed by filtration of the boron nitride from the ash to obtain a nitric acid filtrate, and thirdly: Determining the boron content of the nitric acid filtrate by performing an ICP-OES.

[0101] The boron carbide content was determined by a visual examination as described above.

[0102] To illustrate the applicability of the particles described herein, initial results from electrochemical experiments are then presented. The capacity and the first cycle loss were obtained using the powder by preparing the anode suspension: PVDF 9300 Kureha: 5-7%, Carbon black: Super C65 Imerys: 2%, NMP: Alpha, Graphite: 91-93%. The anode was installed in 2032 button cell half-cells. Testing of the half-cells was performed in a 24-channel Arbin cycler using the following sequence: 2 cycles C / 20, 2 cycles C / 5, followed by a constant voltage of 5 mV until <10% of the initial current was applied. Capacity and first cycle loss represent an average of five cells. Example No. Coke type BET[m 2 / g] Capacity mAh / g 1. Cycle loss [%] 6 Needle coke I 1,5 342 8,5 6 Needle coke I (retest) 1,5 347 8,3 7 Needle coke II 2,1 351 8,8 5 Sponge coke II 2,1 342 8,4 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 406,932

[0001] US 6 869 546 B1

[0017] US 5 358 805 A

[0020] US 2018 / 0337423 A1

[0021] JP 2000 012020 A

[0022] JP 2000 12021 A

[0023] US 2001 / 0051300 A1

[0024] US 3 684 446 [0074, 0088] US 3 807 961

[0074]

Claims

[1] Carbon particles comprising at least 97 wt% carbon, based on the total weight of the carbon particle, at most 0.2 wt% impurities, based on the total weight of the carbon particle, at least 0.08 wt% boron, based on the total weight of the carbon particle, and at most 0.05 wt% boron carbide, based on the total weight of the carbon particle. [2] Carbon particles according to claim 1, wherein the carbon particle has a BET surface area of ​​0.5 to 50 m² 2 / g, preferably from 0.5 to 10 m 2 / g, especially preferably from 1 to 3 m 2 / g, and even more preferably from 1 to 2 m 2 / g possesses, and / or wherein the carbon particle has a d 002 -Spacing from 0.3363 nm to 0.3355 nm, preferably from 0.3359 nm to 0.3355 nm, and / or a d 110-spacing of 0.120 nm to 0.126 nm, preferably of 0.1229 nm to 0.1236 nm, and particularly preferably of 0.123027 nm to 0.123244 nm. [3] Carbon particles according to claim 1 or 2, wherein an XPS spectrum of the carbon particle has a first peak from 184.0 eV to 188.0 eV, preferably from 185.0 eV to 187.5 eV, particularly preferably from 185.5 eV to 187.0 eV, and most preferably at about 186.5 eV, and / or wherein an XPS spectrum of the carbon particle has a second peak from 188.5 eV to 192.0 eV, preferably from 189.0 eV to 191.5 eV, particularly preferably from 189.5 eV to 191.0 eV, and most preferably at about 190.3 eV, and / or wherein an XPS spectrum of the carbon particle has essentially no peak at about 187.7 eV, wherein in particular the intensity ratio in the XPS spectrum from first to second peak is 0.25 to 6.0, preferably 0.5 to 2, and particularly preferably 0.8 to 1.

25. [4] Carbon particles according to any of the preceding claims, wherein the carbon particle contains at least 97.5 wt.%, preferably at least 98 wt.%, and particularly preferably at least 98.5 wt.% carbon, based on the total weight of the particle, and / or at most 0.1 wt.%, preferably at most 0.05 wt.%, particularly preferably at most 0.04 wt.%, more preferably at most 0.03 wt.%, and most preferably at most 0.025 wt.% impurities, based on the total weight of the carbon particle. [5] Carbon particles according to any of the preceding claims, wherein the impurities are at least one of the impurities of a metallic character such as transition metals, in particular vanadium and / or iron, oxygen and sulfur, in particular oxygen and sulfur, preferably with at most 100 ppm oxygen and 100 ppm sulfur. [6] Carbon particles according to any of the preceding claims, wherein the carbon particle contains at least 0.1 wt.%, preferably at least 0.15 wt.%, particularly preferably at least 0.2 wt.%, more preferably at least 0.3 wt.% boron, preferably boron in a substituting position, based on the total weight of the carbon particle, and / or at most 2.3 wt.%, preferably at most 2 wt.%, particularly preferably at most 1.5 wt.%, and most preferably at most 1.3 wt.% boron, preferably boron in a substituting position, based on the total weight of the carbon particle. [7] Carbon particles according to one of the preceding claims, wherein the carbon particle contains nitrogen, in particular with a proportion of at least 0.005 wt.%, preferably of 0.01 to 0.05 wt.%, particularly preferably of 0.015 to 0.04 wt.%, and most preferably of 0.02 to 0.03 wt.%, based on the total weight of the carbon particle, preferably determined after removal of the boron nitride from the surface of the carbon particle. [8] Carbon particles according to any of the preceding claims, wherein the carbon particle contains at most 0.03 wt.%, preferably at most 0.02 wt.%, particularly preferably at most 0.01 wt.%, and most preferably at most 0.005 wt.% boron carbide, based on the total weight of the carbon particle, and / or wherein the carbon particle contains at most 0.5 wt.% boron nitride, preferably at most 0.3 wt.% boron nitride, and particularly preferably at most 0.1 wt.% boron nitride, based on the total weight of the carbon particle. [9] Carbon particles according to any of the preceding claims, wherein the carbon particle has a particle size distribution d 50 from 3 to 30 µm, preferably from 4 to 25 µm, and particularly preferably from 5 to 20 µm and / or a particle size distribution d 10 from 1 to 25 µm, preferably from 1.5 to 20 µm, and particularly preferably from 2 to 15 µm and / or a particle size distribution d 90has a thickness of 6 to 50 µm, preferably 8 to 45 µm, and particularly preferably 10 to 35 µm. [10] Carbon particles according to one of the preceding claims, wherein the carbon particle is a core-shell particle comprising a substantially non-graphitizable, in particular hard, carbon shell and a carbon core which is at least partially graphitized and may still contain graphitizable, in particular soft, carbon parts. [11] Carbon particles according to claim 10, wherein the core comprises 91 wt.% to 99 wt.%, preferably 92 wt.% to 99 wt.%, and particularly preferably 94 wt.% to 98.5 wt.% of the total weight of the carbon particle, and the shell comprises 1 wt.% to 9 wt.%, preferably 1 wt.% to 8 wt.%, and particularly preferably 1.5 wt.% to 6 wt.% of the total weight of the carbon particle. [12] Carbon particles according to any one of claims 1 to 11, wherein the carbon particles are produced by granulation to form carbon-like particles using a Binder to produce carbon-like granules, Heating the carbon-like granules to a temperature of at least 1000 °C to produce carbonized granules, The process involves introducing the carbonized granules into an electric field to graphitize them, resulting in graphitized granules, and deagglomerating the graphitized granules to yield carbon particles. wherein at least one of granulation, heating to produce carbonized granules, and insertion to produce graphitized granules is carried out in the presence of a boron source [13] Carbon particles according to claim 12, wherein the carbon-like particles have a particle size distribution d50 from 3 to 30 µm, preferably from 4 to 25 µm, and particularly preferably from 5 to 20 µm and / or a particle size distribution d 10 from 1 to 25 µm, preferably from 1.5 to 20 µm, and particularly preferably from 2 to 15 µm and / or a particle size distribution d 90 of 6 to 50 µm, preferably of 8 to 45 µm, and particularly preferably of 10 to 35 µm and / or wherein the carbon-like particles are selected from unprocessed petroleum coke particles, calcined petroleum coke particles, spherical flake graphite particles, spherical natural graphite particles, recycled anode powder particles, petroleum coke, pitch coke, charred wood, needle coke, sponge coke, metallurgical coke, coal tar-based carbon, mesocarbons, anthracite, synthetic graphite, natural graphite, expanded graphite, carbonized polymers, soot and mixtures thereof, and preferably from unprocessed petroleum coke particles, calcined petroleum coke particles, spherical flake graphite particles, spherical natural graphite particles, recycled anode powder particles and mixtures thereof. [14] Carbon particles according to claim 12 or 13, wherein the binder contains at least one of starch, modified starch, phenolic resin, modified kraft lignin, styrene-butadiene rubber (SBR) and latex, and preferably contains or consists of starch and / or modified starch. [15] Carbon particles according to any one of claims 12 to 14, wherein the carbon-like granules are heated to a first temperature of 30 °C to 700 °C, preferably from 30 °C to 300 °C, and subsequently to a second temperature of 300 °C to 1400 °C, preferably from 300 to 1300 °C, and particularly preferably from 300 °C to 1100 °C. [16] Carbon particles according to claim 15, wherein the carbon-like granules are heated to the first temperature for a period of 0.1 to 20 hours and preferably 0.25 to 12 hours and / or to the second temperature for a period of 0.1 to 20 hours and preferably 0.25 to 12 hours. [17] Carbon particles according to any one of claims 12 to 16, wherein the carbonized granules are introduced into an electrothermal fluidized bed reactor to carry out the graphitization of the carbonized granules, and / or wherein the mean residence time of the carbonized granules in the electric field during graphitization is 5 to 120 minutes, preferably 10 to 90 minutes, particularly preferably 15 to 60 minutes, and most preferably 20 to 45 minutes and / or wherein the graphitized granules are cooled to a temperature of 500 °C or lower after graphitization over a period of 5 to 90 minutes, preferably 10 to 60 minutes, particularly preferably 15 to 45 minutes, and most preferably 20 to 30 minutes and / or wherein the graphitized granules are deagglomerated using a mill, in particular a mill selected from a ball mill, jet mill, hammer mill and a conical mill, preferably a jet mill. [18] Carbon particles according to any one of claims 12 to 17, wherein the boron source is selected from boron oxide, boric acid, elemental boron and mixtures thereof, preferably boron oxide, and / or wherein the boron source is added during granulation or when the carbonized particles are introduced into an electric field, preferably when the carbonized particles are introduced into an electric field, particularly as a separate powder for mixing and evaporation, and / or wherein a nitrogen source, in particular nitrogen, is present when the carbonized particles are introduced into an electric field. [19] Use of a carbon particle according to any one of claims 1 to 18 as the active material of a negative electrode for a battery, in particular a lithium-ion secondary battery. [20] Battery, in particular a lithium-ion secondary battery, which contains the carbon particle according to any one of claims 1 to 18, in particular as an active material of a negative electrode.

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