Method for producing carbon-rich material from heat-treated lignin

Abstract

The present invention relates to a process for the production of fully thermally stable agglomerated lignin, comprising the steps of: a) providing agglomerated lignin having an average particle size in the range of 50-500 [mu] m; and b) heating the agglomerated lignin to a temperature in the range of 140-300 DEG C for a period of at least 30 minutes to obtain a fully thermally stable agglomerated lignin. The invention also relates to a fully thermally stable agglomerated lignin and to a method for producing a carbon-rich material obtained by subjecting a fully thermally stable agglomerated lignin to a heat treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to a process for producing a fully thermally stable agglomerated lignin and a fully thermally stable agglomerated lignin. The present application further relates to a process for producing a carbon-rich material from said fully thermally stable agglomerated lignin, a negative electrode for a non-aqueous secondary battery comprising said carbon-rich material as an active material, and the use of said carbon-rich material as an active material in a negative electrode of a non-aqueous secondary battery. BACKGROUND

[0002] Secondary batteries, such as lithium ion batteries, are batteries that can be charged and discharged multiple times, i.e. they are rechargeable batteries. In lithium ion batteries, lithium ions flow from the negative electrode through the electrolyte to the positive electrode during discharge and back upon charging. Today, lithium compounds, in particular lithium metal oxides, such as lithium nickel manganese cobalt oxide (NMC) or, alternatively, lithium iron phosphate (LFP), are commonly used as materials for the positive electrode, and carbon-rich materials are used as materials for the negative electrode.

[0003] Graphite (natural or synthetic graphite) is today used as a material for the negative electrode in most lithium ion batteries due to its high energy density and stable charge / discharge performance over time. Alternatives to graphite are amorphous carbon materials, such as hard carbon (non-graphitizable amorphous carbon) and soft carbon (graphitizable amorphous carbon), which lack long-range graphite order. Graphite and amorphous carbon have in common that the volume change during charge and discharge is small. This leads to good mechanical stability of the electrode material and helps to maintain good cycle stability. Amorphous carbon can be used as the only active electrode material or in combination with graphite. Hard carbon typically has good charge / discharge rate performance, which is desirable for fast charging and high power systems.

[0004] Amorphous carbon can be derived from lignin. Lignin is an aromatic polymer that is the main constituent in, for example, wood and one of the most abundant sources of carbon on earth. In recent years, with the development and commercialization of technologies to extract lignin in highly purified, solid and particularized form from pulp processes, it has attracted great interest as a possible renewable alternative to the current main aromatic chemical precursors from the petrochemical industry. Amorphous carbon derived from lignin is typically non-graphitizable, i.e. hard carbon.

[0005] Today, the most relevant lignin source commercially is Kraft lignin obtained from hardwood or softwood by the Kraft process. Lignin can be separated from the alkaline black liquor using, for example, membrane filtration or ultrafiltration. A common separation method is described in WO2006031175 Al. In this method, lignin is precipitated from the alkaline black liquor by adding acid, which is then filtered off. The lignin filter cake is reslurried under acidic conditions in a next step and washed before drying and comminution.

[0006] One problem with the use of lignin as a precursor for carbon-rich materials is that the direct use of lignin in the form of a fine powder is not suitable because it exhibits an undesirable thermoplastic behavior. During thermal conversion of lignin powder into carbon-rich materials, lignin undergoes plastic deformation / melting, erosive expansion and foaming. In combination with the strong tendency to dust formation during handling, this severely limits the processability of lignin on an industrially relevant scale in terms of equipment size and method production volume as well as the need for intermediate processing.

[0007] WO2021250604 A1 describes a method for producing carbon from lignin, comprising compacting lignin powder, followed by crushing the compacted lignin to obtain agglomerated lignin having a particle size distribution such that at least 80 wt% of the agglomerates have a diameter in the range of 0.2 to 5.0 mm. The agglomerated lignin is subsequently subjected to a heat treatment to obtain heat-stabilized agglomerated lignin, which can be converted into a carbon-rich material having a retained shape and size, avoiding melting / swelling deformation.

[0008] However, there is still a need for an improved method for obtaining carbon-rich materials from lignin, wherein lignin retains its shape and size during conversion into carbon-rich materials, without melting / swelling deformation, and the obtained carbon-rich materials have a high capacity when used as active material in anodes of secondary batteries. SUMMARY

[0009] It is an object of the present invention to provide an improved method for producing carbon-rich materials, which allows the use of a renewable carbon source, and which method eliminates or mitigates at least some of the drawbacks of prior art methods.

[0010] It is a further object of the present invention to provide a method for producing an improved carbon-rich material, which is suitable for use as active material in the negative electrode of a non-aqueous secondary battery, such as a lithium-ion battery or a sodium-ion battery, in particular to improve the capacity of a non-aqueous secondary battery by using said carbon-rich material as active material in the negative electrode.

[0011] It is a further object of the present invention to provide a method for producing carbon-rich materials from lignin, which allows the use of lignin in the form of a powder, while avoiding dust formation problems, and which retains the shape and size of lignin during heat treatment to obtain carbon-rich materials.

[0012] It is a further object of the present invention to provide a method for producing carbon-rich materials, which is scalable, and thus suitable for large-scale manufacturing.

[0013] The above objects, as well as other objects which will be appreciated by persons of ordinary skill in the art upon reading this disclosure, are achieved by the various aspects of the present disclosure.

[0014] According to a first aspect, the present invention relates to a method for producing fully thermally stable agglomerated lignin, the method comprising the following steps:

[0015] a) Provides lignin with aggregates having an average particle size in the range of 50 to 500 µm; and

[0016] b) Heating the aggregated lignin to a temperature in the range of 140 to 300°C for a period of time of at least 30 minutes to obtain fully thermally stable aggregated lignin.

[0017] By heating the agglomerated lignin, it is ensured that no melting / expansion deformation occurs during any subsequent heat treatment. Surprisingly, it was found that fully heat-stable agglomerated lignin can be obtained by heating agglomerated lignin with an average particle size ranging from 50 to 500 μm. During heat stabilization, the agglomerated lignin is cross-linked. The degree of cross-linking within the obtained fully heat-stable agglomerated lignin is uniform or substantially uniform throughout the entire fully heat-stable agglomerated lignin. This uniform degree of cross-linking ensures that carbon-rich materials with uniform properties can be obtained from the heat-stable agglomerated lignin. Due to the relatively small size of the provided agglomerated lignin, the penetration of oxidizing substances is promoted during the heat stabilization step, ensuring that the obtained heat-stable agglomerated lignin is fully cross-linked, both in the core of the agglomerates. In other words, the uniform degree of cross-linking within the fully heat-stable agglomerated lignin means that the material is homogeneous. The carbon-rich material obtained from uniformly heat-stable agglomerated lignin is also structurally homogeneous.

[0018] According to a second aspect, the present invention relates to a fully thermally stable agglomerated lignin having an average particle size in the range of 50 to 500 µm. Since the agglomerated lignin is fully thermally stable, the degree of crosslinking of the fully thermally stable agglomerated lignin is uniform throughout the entire fully thermally stable agglomerated lignin.

[0019] According to a third aspect, the present invention relates to a method for producing carbon-rich materials, the method comprising the following steps:

[0020] 1) Provides a fully thermally stable aggregated lignin obtainable by the method according to the first aspect;

[0021] 2) subjecting the thermally stable agglomerated lignin to heat treatment at one or more temperatures in the range of 300 to 1500°C, wherein the heat treatment is carried out for a total time in the range of 30 minutes to 10 hours to obtain a carbon-rich material; and

[0022] 3) Optionally crush the obtained carbon-rich material.

[0023] It has been surprisingly found that when fully thermally stable aggregated lignin is heat-treated, the resulting carbon-rich material exhibits a reduced amount of volatiles compared to carbon-rich materials obtained from aggregated lignin that has only been partially thermally stable. This is significant in terms of yield and process efficiency. When used as an active anode material in non-aqueous secondary batteries, the carbon-rich material obtained according to the method of the invention also possesses a pore size distribution that is beneficial in providing carbon-rich materials with high capacity.

[0024] According to a fourth aspect, the present invention relates to a negative electrode for a non-aqueous secondary battery, comprising a carbon-rich material obtainable by the method according to a third aspect as an active material.

[0025] According to a fifth aspect, the present invention relates to the use of carbon-rich materials obtainable by the method according to the third aspect as active materials in the negative electrode of non-aqueous secondary batteries. Detailed Implementation

[0026] Step a) of the method according to the first aspect of the invention includes providing an average particle size (D v50 Aggregated lignin in the range of 50 to 500 µm, or 100 to 400 µm, or 200 to 500 µm.

[0027] In some embodiments, the average particle size of the aggregated lignin is in the range of 50 to 500 μm, or 50 to 400 μm, or 50 to 300 μm, or 100 to 500 μm, or 100 to 400 μm, or 100 to 300 μm, or 200 to 500 μm, or 200 to 400 μm, or 300 to 500 μm.

[0028] In this application, the average particle size is defined as the volume average particle size (D). v50 This value refers to the presence of 50% of the sample volume below its maximum particle size. In the context of this invention, particle size is considered to be the diameter of the particle. Average particle size can be determined using, for example, laser diffraction. In the context of this invention, if the particle is not spherical, the particle diameter is the equivalent spherical diameter of the particle. The equivalent spherical diameter is the diameter of a sphere of equivalent volume.

[0029] Throughout this disclosure, it is intended that the term "lignin" refer to any kind of lignin that can be used as a carbon source for the preparation of carbon-rich materials. Examples of said lignin are, but are not limited to, lignin obtained from plant raw materials such as wood, such as softwood lignin, hardwood lignin, and lignin from annual plants. Furthermore, lignin can be chemically modified.

[0030] Preferably, the lignin has been purified or separated prior to its use in the method according to the invention. The lignin can be separated from black liquor and optionally further purified prior to its use in the method according to the invention. Based on the dry weight of the lignin material, purification typically results in a lignin purity of at least 90%, preferably at least 95%, more preferably at least 98%. Therefore, based on the dry weight of the lignin material, the lignin material used in the method according to the invention preferably contains less than 10%, preferably less than 5%, more preferably less than 2% impurities, such as cellulose, carbohydrates, and inorganic compounds.

[0031] The lignin used in the method according to the invention can be obtained by various extraction methods (e.g., organic solvent extraction or sulfate extraction). Lignin can also be obtained by methods such as steam explosion or acid pretreatment followed by enzymatic hydrolysis. Preferably, the lignin used in the method according to the invention is sulfate lignin, i.e., lignin obtained by the sulfate extraction method. Sulfate lignin can be obtained from hardwoods or softwoods. Lignin can be obtained by the method disclosed in WO2006031175A1 (commonly referred to as the LignoBoost method). Typically, this method includes the following steps: precipitating lignin from alkaline black liquor by acidification; separating the precipitated lignin; and re-slurrying the lignin at least once under acidic conditions. The obtained lignin can be dried and pulverized, and thus provided as solid particles.

[0032] As used herein, the term "aggregated lignin" refers to macroscopic particles that comprise clusters of smaller lignin particles. By providing lignin in aggregated form, denser and harder materials are achieved. Hard aggregates are advantageous during subsequent processing because they resist physical impacts during processing. Furthermore, the tendency for pulverization is reduced when lignin is provided in aggregated form. The aggregated lignin of the present invention is prepared by a method including a step of compacting the lignin. This means that the aggregated lignin is not in the form of spontaneously aggregated secondary lignin particles formed, for example, during lignin precipitation.

[0033] The aggregated lignin provided in step a) may have a concentration of 0.4 to 0.8 g / cm³. 3 For example, 0.5 to 0.7 g / cm³ 3 The packing density within the range.

[0034] The agglomerated lignin provided in step a) may contain at least one additive, or may not contain any additive. In the context of this invention, an additive is a substance added to improve the function of the method or the resulting material. Therefore, an additive is a substance added but not present in the lignin raw material. Thus, in the context of this invention, moisture (e.g., water) and other components already present in the lignin raw material are not considered additives.

[0035] Based on the total dry weight of the aggregated lignin, the total amount of additives is preferably less than 5 wt%, such as 0 to 5 wt%, or 0.1 to 5 wt%, or less than 2 wt%, such as 0 to 2 wt%, or 0.1 to 2 wt%. Thus, based on the total dry weight of the aggregated lignin, the aggregated lignin contains at least 95 wt%, such as at least 98% lignin.

[0036] Step b) of the method according to the first aspect includes heating the aggregated lignin to a temperature in the range of 140 to 300°C for a period of time of at least 30 minutes to obtain fully thermally stable aggregated lignin.

[0037] As used herein, the term "thermal stabilization" refers to the process of heating aggregated lignin at a temperature below that required for carbonization. By performing thermal stabilization, the resulting thermally stable aggregated lignin can be heat-treated while maintaining its shape and size, avoiding melting / expansion and deformation during any subsequent heat treatment. Thermal stabilization is preferably performed in an oxidizing atmosphere. Crosslinking of the lignin will occur during thermal stabilization due to the combined effects of oxidation and heat. Crosslinking is promoted by the combined effects of oxidation and heat. Due to crosslinking, the lignin within the aggregates will harden and will not melt / expand during any subsequent heat treatment. Before thermal stabilization, the lignin aggregates behave as thermoplastic materials, while after thermal stabilization, they behave as thermosetting materials. The terms "thermal stabilization" and "heating" are used throughout the disclosure to define the method for obtaining thermally stable aggregated lignin.

[0038] As used herein in expressions such as “fully thermally stable agglomerated lignin,” the term “fully thermally stable” refers to agglomerated lignin that has been thermally stabilized to achieve the same or substantially the same degree of crosslinking throughout the material. Therefore, the degree of crosslinking is uniform or substantially uniform throughout fully thermally stable agglomerated lignin. This means that material properties, such as structure and hardness, will be the same throughout fully thermally stable agglomerated lignin. For example, the core of fully thermally stable agglomerated lignin will have the same hardness and the same degree of crosslinking as the shell. Fully thermally stable agglomerated lignin is structurally homogeneous. Fully thermally stable agglomerated lignin can also be referred to as fully crosslinked agglomerated lignin.

[0039] The glass transition temperature (Tg) of lignin typically increases after the heating step, resulting in a higher Tg for thermally stable aggregated lignin compared to that before heating. The Tg of fully stable aggregated lignin is generally higher than that of aggregated lignin before heating, and is also generally higher than that of partially thermally stable aggregated lignin.

[0040] Carbon-rich materials obtained from fully thermally stable aggregated lignin will have improved properties, such as pore size distribution.

[0041] The heating in step b) to produce fully thermally stable aggregated lignin is preferably carried out in an oxidizing atmosphere. This oxidizing atmosphere contains oxidizing agents that can react to crosslink the lignin. Heating can be carried out, for example, in the presence of oxygen, iodine, ozone, nitrogen dioxide, nitrobenzene, hydrogen peroxide, and peracetic acid. Preferably, heating is carried out in air. Alternatively, any suitable oxidizing agent can be supplied in a nitrogen atmosphere.

[0042] By providing aggregated lignin with an average particle size in the range of 50 to 500 μm, the penetration of oxidizing substances is promoted, and the aggregated lignin will be completely thermally stable upon heating.

[0043] If, alternatively, lignin aggregates with relatively large particle sizes are provided, for example, at least 80 wt% of the aggregated lignin has a diameter in the range of 0.2 to 5.0 mm (corresponding to an average particle size in the range of 0.8 to 2.0 mm), the aggregated lignin will only be partially thermally stable after heat treatment. Therefore, the degree of crosslinking will be uneven throughout the thermally stable aggregated lignin. The shell of the thermally stable aggregated lignin will be fully crosslinked and hard, while the core remains mostly uncrosslinked and soft. Thus, the obtained thermally stable aggregated lignin is only partially crosslinked, or partially thermally stable. The uncrosslinked core may undergo foaming / expansion during subsequent heat treatment, which will affect the structure of the carbon-rich material obtained from this lignin. The obtained carbon-rich material will have a different structure on the surface than in the core, which is undesirable in terms of performance.

[0044] As used herein in expressions such as “partially thermally stable aggregated lignin,” the term “partially thermally stable” refers to aggregated lignin that has been partially cross-linked during the thermal stabilization process. The degree of cross-linking is non-uniform; some parts (e.g., the shell) are fully cross-linked, while others (e.g., the core) are uncross-linked. In other words, the shell may be fully thermally stable, while the core remains unstabilized and retains thermoplastic behavior. Partially cross-linked, thermally stable aggregated lignin is structurally non-uniform. Partially thermally stable aggregated lignin may also be referred to as partially cross-linked aggregated lignin.

[0045] Depending on the method used to prepare the aggregated lignin, the aggregated lignin provided in step a) may be non-crosslinked (i.e., not subjected to any heat treatment) or partially crosslinked (i.e., partially heat-stable).

[0046] The heating in step b) to produce fully thermally stable agglomerated lignin can be carried out continuously or in batches. Heating can be carried out using methods known in the art, and is preferably carried out in a rotary kiln, moving bed furnace, or rotary hearth furnace.

[0047] Heating is performed to produce fully thermally stable aggregated lignin, such that the aggregated lignin is heated to a temperature in the range of 140 to 300°C, preferably 180 to 260°C. Heating is carried out for at least 30 minutes, meaning the aggregated lignin has a residence time of at least 30 minutes inside the heating apparatus. In one embodiment, heating is carried out for at least 1 hour, or at least 1.5 hours. Preferably, heating is carried out for less than 12 hours. Heating may be carried out at the same temperature throughout the heating phase, or it may be carried out at different temperatures, for example, by gradually increasing the temperature or using a temperature gradient. More preferably, heating is carried out such that the aggregated lignin is first heated to a temperature in the range of 140 to 175°C for at least 15 minutes, and then heated to a temperature in the range of 175 to 300°C for at least 15 minutes.

[0048] Compared to agglomerated lignin prior to heating to obtain a fully thermally stable material, a small weight loss may occur during heating. The total weight loss is typically less than 15 wt%, and is mainly due to moisture evaporation and loss of volatiles due to the decomposition of lignin during heating.

[0049] By controlling and optimizing parameters such as temperature and time during the heating step, fully thermally stable agglomerated lignin can be obtained, which retains its shape and size without melting or expansion during subsequent processing. Due to the mechanical stability and relatively short residence time of the agglomerated lignin, the described method exhibits excellent compatibility with typical methods for continuous production, such as those using rotary kilns. This is particularly important for achieving an economical large-scale industrial method for producing carbon-rich materials. Since the average particle size of the agglomerated lignin is in the range of 50 to 500 μm, the time required for complete thermal stabilization is typically short, which is advantageous from a method efficiency perspective.

[0050] Fully thermally stable aggregated lignin can have a concentration of 0.4 to 0.8 g / cm³. 3 Or 0.5 to 0.7 g / cm³ 3 The bulk density is within a certain range. Heating can cause a slight increase or decrease in bulk density compared to agglomerated lignin before heating. However, the bulk density of fully thermally stable agglomerated lignin will preferably remain within the same range as before the heating step.

[0051] During heating, the structure of lignin changes due to cross-linking. It has been surprisingly recognized that the degree of thermal stabilization of lignin affects the pore size distribution in carbon-rich materials obtained from thermally stabilized lignin. In carbon-rich materials obtained from fully thermally stabilized agglomerated lignin, the pore size distribution results in high capacity when the carbon-rich material is used as an active anode material in secondary batteries. The pore size distribution of carbon-rich materials obtained from fully thermally stabilized agglomerated lignin typically has a wide range of pore sizes, including a large number of relatively small pores. Conversely, in carbon-rich materials obtained from partially thermally stabilized agglomerated lignin, the pore size distribution is less favorable in terms of capacity. The pore size distribution of carbon-rich materials obtained from partially thermally stabilized agglomerated lignin typically has a narrow range of pore sizes, with most pores having relatively large sizes.

[0052] The color of heat-stabilized aggregated lignin differs from the color of aggregated lignin before heat stabilization. The color can be determined, for example, using a spectrophotometer and reported according to the CIELAB color space. In the CIELAB color space, color can be reported as lightness (L*), green-red (a*), and blue-yellow (b*) components. Preferably, the surface lightness (L*) of fully heat-stabilized aggregated lignin is in the range of 34 to 39. Before heat stabilization, the surface lightness of aggregated lignin is above 44, for example, in the range of 44 to 52. Therefore, the lightness of aggregated lignin decreases during heat stabilization.

[0053] Preferably, the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) on the surface of the fully thermally stable agglomerated lignin is less than 5.0, i.e., |a*| + |b*| < 5.0. More preferably, the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) on the surface of the fully thermally stable agglomerated lignin is less than 3.0. The sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) on the surface of the fully thermally stable agglomerated lignin can be in the range of 0.5 to 5.0 or 0.5 to 3.0. The absolute value of the CIELAB green-red component (a*) on the surface of the fully thermally stable agglomerated lignin is preferably less than 3.0 or less than 2.0. The absolute value of the CIELAB blue-yellow component (b*) on the surface of the fully thermally stable agglomerated lignin is preferably less than 3.0 or less than 2.0.

[0054] The color of the core of heat-stable aggregated lignin can be measured by first crushing the aggregate to obtain smaller lignin particles. The smaller lignin particles will represent all parts of the aggregate, i.e., the core and the surface portion, and can therefore be used to give an average color value for heat-stable aggregated lignin.

[0055] For fully thermally stable aggregated lignin, the surface of lignin particles obtained by crushing aggregated lignin has the same or very similar L*, a*, and b* values ​​as those measured on the surface of aggregated lignin.

[0056] For partially thermally stable aggregated lignin, the values ​​of L*, a*, and b* will differ between the surface and core of the aggregate. The surface of partially thermally stable aggregated lignin will be completely thermally stable, and the values ​​of L*, a*, and b* will be within the same range as those for completely thermally stable aggregated lignin. After crushing, the surface of the obtained lignin particles can have a brightness of 40-44, and the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) of the surface of the obtained lignin particles is less than 10, i.e., |a*| + |b*| < 10. The absolute value of the CIELAB green-red component (a*) of the lignin particle surface can be less than 5.0. The absolute value of the CIELAB blue-yellow component (b*) of the lignin particle surface can be less than 5.0.

[0057] Therefore, the values ​​of L*, a*, and b* measured on the surface of crushed, agglomerated lignin can be used to assess and monitor the degree of thermal stability obtained during the heating of agglomerated lignin, and thus also the degree of crosslinking.

[0058] The agglomerated lignin provided in step a) can be obtained by compacting the lignin powder and crushing the resulting lignin powder to obtain agglomerated lignin with an average particle size in the range of 50 to 500 µm. Two embodiments of the method for obtaining agglomerated lignin will now be described in detail.

[0059] In the first embodiment, the aggregated lignin provided in step a) is obtained by a method comprising the following steps:

[0060] - Provides lignin in powder form;

[0061] - Compact the lignin powder to obtain compacted lignin;

[0062] - Crush the compacted lignin to obtain aggregated lignin with an average particle size in the range of 50 to 500 µm.

[0063] The lignin powder is preferably dried prior to compaction. The drying of the lignin powder is carried out using methods and equipment known in the art. The lignin in powder form may have a moisture content of less than 45 wt%. Preferably, the moisture content of the lignin before compaction is less than 25 wt%, more preferably less than 10 wt%, and even more preferably less than 8 wt%. The moisture content of the lignin before compaction may be at least 1 wt%, for example, at least 5 wt%. The temperature during drying is preferably in the range of 80 to 160°C, more preferably in the range of 100 to 120°C.

[0064] The size distribution of the lignin powder is preferably such that 80 wt% of the particles have a diameter of less than 0.2 mm.

[0065] The lignin powder obtained after drying has a wide particle size distribution ranging from 1 μm to 2 mm, with a significant bias towards the micrometer range. This means that the diameter of the majority of particles is in the range of 1 to 200 μm. The lignin powder preferably has a particle size distribution of 0.3–0.4 g / cm³. 3 The packing density.

[0066] Lignin compaction is preferably carried out by roller compaction. Lignin roller compaction can be achieved by agglomerating lignin particles using a roller compactor.

[0067] In the compaction step, an intermediate product is generated. Here, fine lignin powder is typically fed through a hopper and conveyed to the compaction zone by a horizontal or vertical feed screw, where the material is compacted into flakes by compaction rollers with a defined gap. Flakes with a uniform density can be obtained by controlling the feed screw speed and the pressure development in the compaction zone. The pressure development in the compaction zone can preferably be monitored and controlled by the rotational speed of the compaction rollers. As the powder is dragged between the rollers, it enters the so-called roll gap region, where the density of the material increases and the powder is transformed into flakes or strips. The rollers used have cavities. The depth of each cavity used in roller compaction is 0.1 to 10 mm, preferably 1 to 8 mm, more preferably 1 to 5 mm or 1 to 3 mm. The specific pressure applied during compaction can vary depending on the equipment used for compaction, but can be in the range of 1 to 100 kN / cm. Suitable equipment for compaction is known in the art.

[0068] After compaction, crushing is preferred. In the crushing step, the intermediate product from the compaction step is crushed or ground, for example by a rotary granulator, cage mill, beater mill, hammer mill, or crusher mill and / or a combination thereof.

[0069] After crushing, the crushed material can undergo a screening step to remove additional fine material. In addition, large materials can be removed and / or recycled back to the crushing step.

[0070] In the sieving step, the intermediate product from the crushing step is screened by physical grading (e.g., sieving, also known as screening) to obtain a product of agglomerated lignin having a particle size distribution defined by the aperture of the sieve or screen in this step. The sieve or screen is selected such that small-sized particles (e.g., fine particles) pass through the sieve and are rejected and preferably returned to the compaction step. In other embodiments, the sieve may be selected such that most particles with diameters less than 50 μm or less than 100 μm pass through the sieve and are rejected and preferably returned to the compaction step. Particles with sufficiently large diameters that cannot pass through the sieve are retained and undergo subsequent method steps according to the invention. The sieve may be selected such that most particles with diameters greater than 50 μm or greater than 100 μm are retained. Sieving may be performed in more than one step, i.e., sieving may be performed such that the crushed material from the crushing step sequentially passes through more than one sieve or screen.

[0071] In one embodiment of roll compaction, the roll is configured such that the first roll has an annular edge, which seals the powder in the roll gap region along the roll surface in the axial direction.

[0072] In one embodiment, the roll configuration is such that the roll gap region is sealed along the roll surface in the axial direction with a static plate. By ensuring that the roll gap region is sealed, powder loss at the axial ends of the roll is minimized compared to a fully cylindrical roll.

[0073] Due to the compaction of lignin powder during the preparation of agglomerated lignin, the bulk density of lignin increases with the pressure applied to the lignin powder. This means that agglomerated lignin will have a higher bulk density than lignin powder. Denser lignin particles can be beneficial during subsequent processing into carbon-rich materials, as dense lignin particles have been found to retain their shape and size without melting or expanding. Agglomerated, compacted lignin particles will also have relatively high hardness after compaction. Hard agglomerates are advantageous during subsequent processing because they resist physical impacts during processing. Furthermore, when using hard, compacted particles, processing problems that could arise due to the presence of lignin dust on the particle surface are avoided. This is particularly important in large-scale methods, as dust can form explosive mixtures with air and also cause blockages inside processing equipment.

[0074] In the second embodiment, the aggregated lignin provided in step a) is obtained by a method comprising the following steps:

[0075] - Provides lignin in powder form;

[0076] - Compact the lignin powder to obtain compacted lignin;

[0077] - Crush the compacted lignin to obtain aggregated lignin with an average particle size in the range of 0.8 to 2.0 mm.

[0078] - The obtained aggregated lignin is heated to a temperature in the range of 140 to 250°C for a period of time of at least 1.5 hours to obtain partially thermally stable aggregated lignin;

[0079] - Crush the partially thermally stable agglomerated lignin to obtain agglomerated lignin with an average particle size in the range of 50 to 500 µm.

[0080] Compared to the method of the first embodiment, the method of the second embodiment includes first preparing lignin aggregates having an average particle size of 0.8 to 2.0 mm, which is heated in a first heating step to obtain partially heat-stable aggregated lignin. The obtained partially heat-stable aggregated lignin is then crushed into aggregates having an average particle size in the range of 50 to 500 µm.

[0081] The steps of providing lignin powder and compacting lignin powder are defined as detailed above for the first embodiment. The first crushing step is performed as detailed above for the first embodiment, except that lignin agglomerates with an average particle size in the range of 0.8 to 2.0 mm are obtained. In an optional sieving step, a sieve or screen is selected such that most particles with a diameter less than 100 μm (or 500 μm) pass through the screen, and most particles with a diameter greater than 100 μm (or 500 μm) are retained. Additionally, it is preferable to remove large particles.

[0082] The equipment used in the compaction and crushing steps is the same, regardless of the particle size of the resulting agglomerates. Instead, a suitable sieve or screen is selected based on the desired agglomerate size.

[0083] Following the first crushing step, the resulting lignin agglomerates with an average particle size in the range of 0.8 to 2.0 mm are subjected to heating. Heating is performed as described above for the heat stabilization step. Due to the relatively large particle size, partially heat-stable agglomerates are obtained. In the second crushing step, the partially heat-stable agglomerates are crushed to obtain lignin agglomerates with a size in the range of 50 to 500 µm. The second crushing step is performed as described above for the first embodiment. After heating the lignin agglomerates with an average particle size in the range of 0.8-2.0 mm, a partially heat-stable material is obtained. Therefore, the lignin agglomerates with a particle size in the range of 50 μm to 500 μm obtained after the second crushing step will be heat-stable to varying degrees depending on their position within the agglomerates before the second crushing step. After the second crushing step, this agglomerate will also be collectively referred to as "partially heat-stable".

[0084] Compared to the second embodiment, the first embodiment has the advantage of reducing the number of process steps. From a cost perspective, fewer process steps are beneficial. However, the first embodiment involves processing small-sized lignin agglomerates. Small size can lead to clogging of process equipment and also increases the risk of dust explosions during processing. Furthermore, smaller-sized lignin agglomerates tend to melt during thermal stabilization prior to crosslinking.

[0085] However, these problems can be overcome by carefully selecting process equipment. If melting is severe during stabilization, an additional crushing step can be performed on the fully thermally stabilized agglomerated lignin to obtain the desired particle size.

[0086] The method according to the second embodiment avoids the disadvantages of the first embodiment. Blockage and dust explosions are avoided because relatively large agglomerates are processed. Subsequent processing is facilitated once the agglomerated lignin has been partially heat-stabilized, including after crushing to further reduce particle size, thereby obtaining agglomerated lignin with an average particle size in the range of 50 to 500 μm. Melting during the heat stabilization of small-sized agglomerated lignin is not a problem when the agglomerated lignin has been partially heat-stabilized before being crushed to smaller sizes.

[0087] Both the first and second embodiments may include the following additional steps:

[0088] - Provide at least one additive; and

[0089] - Mix the lignin powder with the at least one additive.

[0090] Any suitable additive may be provided. For example, the at least one additive may be selected from any suitable type of binder or lubricant, which can facilitate the subsequent compaction process and improve the density and mechanical properties of the obtained aggregated lignin. The at least one additive may be a functional reinforcing additive that has an effect on the carbon-rich material obtained from the aggregated lignin. Examples of such functional reinforcing additives include carbon additives and silicon-containing additives. Carbon additives may be selected from at least one of graphite, graphene, carbon nanotubes, charcoal, biochar, hard carbon, soft carbon, carbon black, and conductive carbon. Silicon-containing additives may be selected from at least one of elemental silicon, silicon suboxide, silicon-metal alloy, or silicon-metal-carbon alloy. The silicon suboxide may be SiOx in which 0 ≤ x ≤ 2. The silicon-metal alloy may be any suitable silicon-metal alloy, such as SiFex or SiFexAly. The silicon-metal-carbon alloy may be, for example, SiFexCy.

[0091] Based on the total dry weight of the lignin-additive powder mixture, the total amount of additives is preferably less than 5 wt%, for example 0 to 5 wt%, or 0.1 to 5 wt%, or less than 2 wt%, for example 0 to 2 wt%, or 0.1 to 2 wt%.

[0092] The mixing of lignin powder and the at least one additive is carried out using methods and equipment known in the art. An example of a suitable method is a vertical mixer, such as a paddle, helical, or belt-helical mixer in batch or continuous mode. The mixing process can be carried out in low, medium, or high shear impact modes.

[0093] In embodiments containing at least one additive, the compaction step is also performed as described above. The at least one additive is compacted together with the lignin powder. The at least one additive will be dispersed within the resulting aggregated lignin.

[0094] A second aspect of the invention relates to a fully thermally stable aggregated lignin having an average particle size in the range of 50 to 500 µm. The degree of crosslinking is uniform throughout the thermally stable aggregated lignin. The fully thermally stable aggregated lignin according to the second aspect can be prepared by the method according to the first aspect. The fully thermally stable aggregated lignin may be further defined as described above with reference to the first aspect.

[0095] Specifically, fully thermally stable aggregated lignin is cross-linked throughout the material. Thermally stable aggregated lignin is hard, dark in color, and retains its shape and size without melting / expansion deformation during any subsequent heat treatment. The structure of fully thermally stable aggregated lignin is suitable for use as a starting material to obtain carbon-rich materials with a pore size distribution suitable for use as high-capacity anode materials.

[0096] A third aspect of the invention relates to a method for producing a carbon-rich material by heat-treating fully thermally stable agglomerated lignin according to the first aspect. Therefore, the method according to the third aspect may include performing the method according to the first aspect.

[0097] As used herein, the term "heat treatment" refers to the process of heating fully thermally stable agglomerated lignin at one or more temperatures for a sufficient time to convert the lignin into a carbon-rich material. This process may also be referred to as "carbonization" or "calcination." After heat treatment, the carbon content is greater than 80 wt%, or greater than 90 wt%, or greater than 95 wt%, or greater than 98 wt%. Depending on the temperature during heat treatment, different types of carbon, such as charcoal or hard carbon, can be obtained from the thermally stable agglomerated lignin.

[0098] As used herein, the term "carbon-rich material" refers to a carbon material obtained by heat treatment of fully thermally stable agglomerated lignin. The carbon-rich material has a carbon content greater than 80 wt%, or greater than 90 wt%, or greater than 95 wt%, or greater than 98 wt%. The carbon-rich material may also contain, for example, heteroatoms such as oxygen, hydrogen, nitrogen, or sulfur atoms, inorganic impurities, and functional additives. The carbon-rich material of the present invention is amorphous (i.e., non-crystalline) carbon, preferably hard carbon.

[0099] Step 1) of the method according to the third aspect includes providing a fully thermally stable agglomerated lignin that is obtainable by the method according to the first aspect. As outlined above, the fully thermally stable agglomerated lignin is fully cross-linked. Due to cross-linking, the lignin will retain its shape and size without melting / expansion deformation during the heat treatment that transforms it into a carbon-rich material. Therefore, the resulting carbon-rich material will have the same shape as the fully thermally stable agglomerated lignin.

[0100] Step 2 of the method according to the third aspect includes subjecting fully thermally stable agglomerated lignin to heat treatment at one or more temperatures in the range of 300 to 1500°C, wherein the heat treatment is carried out for a total time in the range of 30 minutes to 10 hours in order to obtain a carbon-rich material.

[0101] Heat treatment can be carried out at the same temperature throughout the entire process, or it can be carried out at different temperatures, for example, by gradually increasing the temperature or using a temperature gradient. Heat treatment may include a temperature ramp from the initial temperature to the target temperature. The heating rate can be 1-100°C / min. For example, heat treatment may include several intermediate temperatures with temperature ramps between them before reaching the target temperature required for the carbonization of fully thermally stable agglomerated lignin. Heat treatment can be carried out as a batch process or a continuous process. Any suitable reactor can be used, such as a rotary kiln, moving bed furnace, pusher furnace, or rotary hearth furnace. Heat treatment is preferably carried out under an inert atmosphere, preferably a nitrogen atmosphere.

[0102] Preferably, the heat treatment includes a preliminary heating step, preferably followed by a final heating step. The preliminary heating step is preferably carried out at one or more temperatures in the range of 300 to 800°C, for example, 500 to 700°C. The preliminary heating step is preferably carried out under an inert atmosphere, preferably under a nitrogen atmosphere. The duration of the preliminary heating step is at least 30 minutes, and preferably less than 10 hours. The surface area of ​​the carbon-rich material obtained after the preliminary heating step is typically 300 m². 2 / g to 700m 2 BET measurements were performed using nitrogen gas within the range of / g.

[0103] The final heating step is preferably carried out at one or more temperatures in the range of 800 to 3000°C. The final heating step is preferably carried out under an inert atmosphere, more preferably under a nitrogen atmosphere. The duration of the final heating step is at least 30 minutes, and preferably less than 10 hours. After a final heating step at 1000°C or higher, the surface area of ​​the obtained carbon-rich material is typically 50 m². 2 / g or less.

[0104] The preliminary and final heating steps can be performed as discrete steps or as a single step in a direct sequence. The preliminary and final heating steps may include heating at one or more temperatures, as discussed above with respect to heat treatment. For example, preliminary heating may begin at about 300°C, followed by a temperature increase to about 500°C. The final heating step is preferably performed between 900 and 1300°C, for example at about 1000°C.

[0105] The preliminary and final heating steps can be performed as batch processes or as continuous processes. Any suitable reactor can be used. The preliminary and final heating steps can be performed in the same reactor or in separate reactors.

[0106] The color of the carbon-rich material may differ slightly from, or be slightly different from, the color of fully thermally stable aggregated lignin. The color can be determined, for example, using a spectrophotometer and reported according to the CIELAB color space. In the CIELAB color space, the color can be reported as lightness (L*), green-red (a*), and blue-yellow (b*) components. Preferably, the lightness (L*) of the carbon-rich material surface is in the range of 34 to 39.

[0107] Preferably, the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) of the carbon-rich material surface is less than 2.0 or less than 1.0, i.e., |a*| + |b*| < 2.0 or |a*| + |b*| < 1.0. The absolute value of the CIELAB green-red component (a*) of the carbon-rich material surface is preferably less than 1.5 or less than 1.0. The absolute value of the CIELAB blue-yellow component (b*) of the carbon-rich material surface is preferably less than 1.5 or less than 1.0. In some embodiments, the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) of the carbon-rich material surface is zero. In some embodiments, the sum of the absolute values ​​of the CIELAB green-red component (a*) and CIELAB blue-yellow component (b*) of the carbon-rich material surface is in the range of 0 to 2.0 or 0 to 1.0.

[0108] The absolute values ​​of a* and b* on the surface of carbon-rich materials can be lower than those on the surface of fully thermally stable agglomerated lignin before carbonization. The values ​​of a* and b* can also be approximately the same on the surface of carbon-rich materials and on the surface of fully thermally stable agglomerated lignin.

[0109] The preferred carbon-rich material has a carbon content of 0.2-0.4 g / cm³. 3 The bulk density is lower than that of aggregated lignin and fully thermally stable lignin, mainly due to mass loss during heat treatment.

[0110] The preferred helium true density of carbon-rich materials is 1.4-2.1 g / cm³. 3 For example, 1.7-2.0 g / cm³ 3 The true density of helium can be determined using a pycnometer, as is known to those skilled in the art. It is important that the true density of helium be within the range of 1.4 to 2.1 g / cm³. 3 Within a certain range, because otherwise, when used as an active material in the negative electrode of a non-aqueous secondary battery, the doping and dedoping capacity of carbon-rich materials can be reduced, and the irreversible capacity of the battery can be increased. If the density of the carbon-rich material is too low, the energy density of the electrode can also be reduced.

[0111] The carbon-rich material of this invention is suitable for use as an active material in the anode of a secondary battery because it has high capacity, which is achieved through a favorable pore size distribution. This pore size distribution is a result of the carbon-rich material obtained from fully thermally stable aggregated lignin, as it is related to the degree of crosslinking of lignin. Crosslinking leads to a structure in lignin that favors the production of a suitable pore size distribution during the conversion into a carbon-rich material.

[0112] The carbon obtained as a product of step 2) can be used, for example, as biochar, or as a precursor to activated carbon.

[0113] Step 3) of the method according to the third aspect includes optionally pulverizing the obtained carbon-rich material. In many applications, the particle size of the carbon-rich material obtained in step 2) must be reduced to obtain carbon powder before use. For example, when the carbon-rich material of the present invention is used as an active material in the anode of a secondary battery, particle size reduction is preferred.

[0114] Grinding can be carried out by any suitable method, using, for example, a cutting mill, a blade mixer, a ball mill, an impact mill, a hammer mill, and / or a jet mill. Optionally, fine / coarse particle selection can be performed after grinding by grading and / or sieving.

[0115] It can pulverize carbon-rich materials and optionally select fine / coarse particles to obtain carbon powder containing powder particles with an average particle size in the range of 1 to 25 μm.

[0116] More than one crushing or grinding step can be performed. In addition, the carbon powder can undergo treatments such as coating or further heat treatment.

[0117] The fourth aspect of the invention relates to a negative electrode for a non-aqueous secondary battery, comprising a carbon-rich material obtainable by the method according to the third aspect as an active material.

[0118] The carbon-rich material of the present invention (preferably in powder form) is preferably used as an active material in the negative electrode of a non-aqueous secondary battery (e.g., a lithium-ion battery or a sodium-ion battery). When used to manufacture such a negative electrode, any suitable method for forming such a negative electrode can be used. In the formation of the negative electrode, the carbon-rich material may be processed together with other components. Such other components may include, for example, one or more binders to form the carbon-rich material into an electrode, a conductive material such as carbon black, carbon nanotubes, or metal powder, and / or other Li storage materials such as graphite or lithium. For example, the binder may be selected from, but is not limited to, poly(vinylidene fluoride), poly(tetrafluoroethylene), carboxymethyl cellulose, natural butadiene rubber, synthetic butadiene rubber, polyacrylate, poly(acrylic acid), alginate, etc., or combinations thereof. Optionally, a solvent, such as 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, water, or acetone, is used during processing.

[0119] The fifth aspect of the invention relates to the use of a carbon-rich material obtainable by the method according to the third aspect as an active material in the negative electrode of a non-aqueous secondary battery.

[0120] Example

[0121] Example 1 - Comparison

[0122] Lignin aggregates with an average particle size of 1.25 mm were subjected to thermal stabilization in air at 250°C for 2 hours. After thermal stabilization, a partially thermally stable material was obtained. The resulting lignin aggregates had a black, infusible shell. After thermal stabilization, the Tg of the lignin increased from 148°C (compared to the thermally unstable lignin) to 158°C. The color of the thermally stabilized aggregated lignin was measured using a spectrophotometer, and values ​​of L* = 38, |a*| = 0.5, and |b*| = 0.1 were given. After crushing the aggregated lignin to reduce the particle size, the obtained material was dark brown, indicating incomplete thermal stability of the lignin aggregate core. Conversely, the core remained largely unstable and soft. The color of the crushed material was measured, and values ​​of L* = 43, |a*| = 3.7, and |b*| = 6.2 were given.

[0123] Example 2 - Fully heat stable

[0124] The partially heat-stabilized lignin particles from Example 1 were crushed to obtain a powder with an average particle size of less than 500 μm. The powder was then subjected to heat stabilization in air at 250°C for 2 hours. After heat stabilization, a fully heat-stabilized material was obtained. The resulting lignin aggregates were black, indicating complete heat stabilization. After the second heat stabilization step, the Tg increased from 158°C to 173°C. The color of the heat-stabilized aggregated lignin was measured using a spectrophotometer, and values ​​of L* = 37.5, |a*| = 0.5, and |b*| = 0.2 were given. The lignin aggregates were also hard and had closed porosity.

[0125] Example 3 - Carbonization

[0126] The fully thermally stable agglomerated lignin of Example 2 and the partially thermally stable agglomerated lignin of Example 1 were further carbonized in a nitrogen atmosphere at 1050°C for a residence time of 2 hours. The resulting carbon-rich material was ground to an average particle size of 10 μm. The color of the resulting carbon-rich material was very similar to that of the fully thermally stable agglomerated lignin obtained in Example 2.

[0127] Example 4 - Capacity measurement

[0128] Electrodes were prepared by combining the carbon-rich material of Example 3 with PVDF (6 wt%), wherein the loading density of the carbon-rich material was approximately 6 mg / cm³. 2Half-cells were assembled in a glove box into PAT (EL) cells, with lithium metal as the counter electrode, glass fiber as the separator, and 1 M LiPF6 in an ethylene carbonate:diethyl carbonate (1:1, volume:volume) ratio as the electrolyte. Constant current charge-discharge tests were performed on an Arbin cyclic system. Discharge tests were first conducted at 0 and 1.5V (relative to Li / Li). + The charging process is performed between 0 and 1.5V (relative to Li / Li) with a constant current of C / 5, followed by a constant voltage of 0V and a cutoff current of C / 20. + The reversible capacity of carbon-rich materials obtained from fully thermally stable aggregated lignin is 30-50 mAh / g higher than that obtained from partially stable aggregated lignin.

[0129] Example 5 - Pore size distribution

[0130] The pore size distribution of the carbon-rich material of Example 3 was evaluated using a DFT model via CO2 isotherms obtained by porosimetry. It was found that the carbon-rich material obtained from partially thermally stable agglomerated lignin had a narrow pore size distribution and relatively large pores, while the carbon-rich material obtained from fully thermally stable agglomerated lignin had a wide pore size distribution and numerous small pores.

[0131] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it will be apparent that such other modifications and variations can be made without departing from the spirit and scope of the present invention.

Claims

1. A method for producing fully heat-stable agglomerated lignin, the method comprising the following steps: a) Provides lignin with aggregates having an average particle size in the range of 50 to 500 µm; and b) Heating the aggregated lignin to a temperature in the range of 140 to 300°C for a period of time of at least 30 minutes to obtain fully thermally stable aggregated lignin.

2. The method of claim 1, wherein the aggregated lignin provided in step a) is produced by a method comprising the following steps: - Provides lignin in powder form; - Compact the lignin powder to obtain compacted lignin; - Crush the compacted lignin to obtain aggregated lignin with an average particle size in the range of 50 to 500 µm.

3. The method of claim 1, wherein the aggregated lignin provided in step a) is produced by a method comprising the following steps: - Provides lignin in powder form; - Compact the lignin powder to obtain compacted lignin; - Crush the compacted lignin to obtain aggregated lignin with an average particle size in the range of 0.8 to 2.0 mm; - The obtained aggregated lignin is heated to a temperature in the range of 140 to 300°C for a period of time of at least 30 minutes to obtain partially thermally stable aggregated lignin; - Crush the partially thermally stable agglomerated lignin to obtain agglomerated lignin with an average particle size in the range of 50 to 500 µm.

4. The method according to any one of claims 2 or 3, wherein the method for producing aggregated lignin comprises the following additional steps: - Provide at least one additive; and - Mix the lignin powder with the at least one additive.

5. The method according to any one of the preceding claims, wherein the aggregated lignin provided in step a) has a concentration of 0.5 to 0.7 g / cm³. 3 The packing density within the range.

6. The method according to any one of the preceding claims, wherein the lignin is sulfate lignin.

7. The method according to any one of the preceding claims, wherein the heating of the aggregated lignin in step b) is performed by first heating the aggregated lignin to a temperature in the range of 140 to 175°C for a period of at least 15 minutes, and then heating the aggregated lignin to a temperature in the range of 175 to 300°C for at least 15 minutes.

8. The method according to any one of the preceding claims, wherein heating the agglomerated lignin in step b) is carried out in an oxidizing atmosphere.

9. Fully thermally stable aggregated lignin with an average particle size in the range of 50 to 500 µm.

10. The fully thermally stable agglomerated lignin according to claim 9, wherein the lignin is sulfate lignin.

11. A method for producing carbon-rich materials, the method comprising the following steps: 1) Providing a fully thermally stable agglomerated lignin obtainable by the method according to any one of claims 1-8; 2) subjecting the fully thermally stable agglomerated lignin to heat treatment at one or more temperatures in the range of 300 to 1500°C, wherein the heat treatment is carried out for a total time in the range of 30 minutes to 10 hours to obtain a carbon-rich material; and 3) Optionally crush the obtained carbon-rich material.

12. The method of claim 11, wherein step 2) comprises a preliminary heating step followed by a final heating step.

13. The method of claim 12, wherein the preliminary heating step is performed at a temperature between 400°C and 800°C for at least 30 minutes.

14. The method according to any one of claims 12 or 13, wherein the preliminary heating step is carried out in an inert atmosphere.

15. The method according to any one of claims 12-14, wherein the final heating step is performed at a temperature between 800 and 1500°C for at least 30 minutes.

16. The method according to any one of claims 12-15, wherein the final heating step is performed in an inert atmosphere.

17. The method according to any one of claims 11-16, wherein the carbon-rich material obtained in step 2) has a content of 1.7 to 2.0 g / cm³. 3 True density within a certain range.

18. A negative electrode for a non-aqueous secondary battery, comprising a carbon-rich material obtainable by any one of claims 11-17 as an active material.

19. Use of carbon-rich materials obtainable by any one of claims 11-17 as active materials in the negative electrode of non-aqueous secondary batteries.