Method for forming hard carbon

Abstract

Method (100) for forming hard carbon, comprising: Liquefaction (102) of lignin in at least one of glycerol or glycerol / ethylene glycol with an acid catalyst to form a first monomer of liquefied lignin; Providing (104) a second monomer comprising a cross-linking reagent for the first monomer from liquefied lignin to enable controlled polymerization, resulting in a resin with controlled size and morphology; and Pyrolysis (106) of the resin to form the hard carbon with a controlled morphology, wherein the first monomer and the second monomer are provided in a ratio of 10 wt.% to 90 wt.%.

Description

[0001] The present description refers to a hard carbon material and in particular to a hard carbon formed from liquefied lignin and exhibiting a controlled morphology.

[0002] Hard carbon is a form of carbon that cannot be converted to graphite by heat treatment. It can be produced by heating carbon-containing precursors in the absence of oxygen. Some precursors used to form hard carbon include lignin, polyvinylidene chloride (PVDC), and sucrose. Hard carbon is a low-density, highly microporous material and can be used for the fabrication of anode materials. However, the morphology of hard carbon cannot be adjusted using most organic precursors.

[0003] US 2014 / 0227325A1 describes a process for producing a porous carbon composition, wherein the process comprises subjecting a precursor composition to a thermal annealing step followed by a carbonization step, wherein the precursor composition comprises a template component consisting of a block copolymer and a lignin component, wherein the carbonization step comprises heating the precursor composition to a carbonization temperature for a sufficient time to convert the precursor composition into a carbon material comprising a carbon structure containing mesopores with a diameter within a range of 2 to 50 nm, wherein the porous carbon composition has a mesopore volume of at least 50% with respect to a total of mesopore and micropore volumes.

[0004] CN 1 18 405 686 A describes a process for producing a carbon material for a battery, comprising the following steps: separation of lignin from the black liquor of papermaking and drying of the lignin; dissolution of the dried lignin in an alkaline solution; subsequent addition of a crosslinking agent and carrying out a crosslinking curing reaction to obtain a lignin polymer solid; pre-oxidation of the lignin polymer solid to obtain a lignin-based resin; the process comprises the following steps: pre-carbonization of the lignin-based resin in a protective atmosphere to obtain a carbon material precursor;Performing a gas-phase descaling of the carbon material precursor under the influence of a halogen compound and / or a simple halogen substance in a protective atmosphere to obtain a carbon material precursor, and grinding the carbon material precursor and calcining it in a protective atmosphere to obtain the carbon material for the battery.

[0005] While prior art methods and systems attempt to minimize the disadvantages of using hard carbon for anode materials and achieve their specific purpose, the object of the invention is to provide a new and improved hard carbon and an improved hard carbon anode. Accordingly, a stable and efficient hard carbon is required.

[0006] The problem is solved by a process for forming hard carbon. The process comprises liquefying lignin in at least one glycerol and / or glycerol / ethylene glycol solution with an acid catalyst to form a first monomer from the liquefied lignin. The process includes providing a second monomer comprising a cross-linking agent for the first monomer from the liquefied lignin to enable controlled polymerization, resulting in a resin with controlled size and morphology. Additionally, the process includes pyrolysis of the resin to form the hard carbon with controlled morphology. The first and second monomers are provided in a ratio of 10 wt% to 90 wt%.

[0007] According to one embodiment, the method comprises a lignin comprising at least one of kraft lignin, enzymatic lignin, sulfonated lignin or alkyl lignin.

[0008] According to another embodiment, the process comprises lignin between 10 wt.% and 90 wt.% of the liquefied lignin.

[0009] According to another embodiment, the process comprises liquefying the lignin using glycerin in an amount between 10 wt.% and 90 wt.% of the liquefied lignin.

[0010] According to another embodiment, the process comprises liquefying the lignin using glycerin / ethylene glycol in an amount between 10 wt.% and 90 wt.% of the liquefied lignin.

[0011] According to another embodiment, the process comprises an acid catalyst between 0.1 wt.% and 50 wt.% of the liquefied lignin.

[0012] According to a further embodiment, the process includes an acid catalyst comprising at least one of phosphoric acid or hydrochloric acid.

[0013] According to another embodiment, the process includes an acid catalyst comprising at least one of nitric acid or sulfuric acid.

[0014] According to another embodiment, the method comprises a cross-linking reagent comprising at least one of epoxy or isocyanate.

[0015] According to another embodiment, the method comprises a cross-linking reagent comprising at least one formaldehyde or an ester.

[0016] According to a further embodiment, the method comprises a cross-linking reagent comprising at least one of an acid or an acid chloride.

[0017] According to another embodiment, the method includes providing a controlled polymerization, further comprising the use of bulk polymerization.

[0018] According to another embodiment, the method includes providing a controlled polymerization, further comprising the use of spray polymerization.

[0019] According to another embodiment, the method includes providing a controlled polymerization, further comprising the use of emulsion polymerization.

[0020] According to another embodiment, the method includes providing a controlled polymerization, further comprising the use of extrusion polymerization.

[0021] According to another embodiment, the method comprises pyrolysis of the resin, further comprising pyrolysis of the resin at a temperature between 700°C and 1600°C.

[0022] According to another embodiment, the process comprises hard carbon with a spherical morphology.

[0023] In one application, a hard carbon provided according to the invention and its embodiments is used to form a hard carbon anode. The hard carbon comprises a lignin-derived hard carbon with a spherical morphology. The lignin-derived hard carbon is formed by liquefying lignin in at least one glycerol or glycerol / ethylene glycol solution with an acid catalyst to form liquefied lignin, wherein controlled polymerization is provided by adding a cross-linking agent to the liquefied lignin, resulting in a resin with a controlled size and morphology, and pyrolysis of the resin to form the hard carbon with a controlled morphology.

[0024] In one application, a hard carbon anode is provided. The hard carbon anode provided according to the invention and embodiments comprises an anode consisting of lignin-derived hard carbon with a spherical morphology. The lignin-derived hard carbon is formed by liquefying lignin in at least one glycerol or glycerol / ethylene glycol solution with an acid catalyst to form liquefied lignin, providing controlled polymerization by adding a cross-linking agent to the liquefied lignin, resulting in a resin with a controlled size and morphology, and pyrolyzing the resin to form the hard carbon with a controlled morphology.

[0025] Further areas of application of the present description will become apparent from the detailed description below.

[0026] The above features and advantages, as well as other features and advantages of the system and method described here, are readily apparent from the detailed description, including the claims and examples, when considered in conjunction with the accompanying drawings.

[0027] The present description will be better understood with the help of the detailed description and the attached drawings, whereby: Fig. 1 is a perspective view showing an example of a vehicle including a battery pack with a large number of battery cells. Fig. 2 is a perspective view showing a battery cell located inside the Fig. 1 battery packs shown, wherein the battery cell comprises at least one electrode stack with a hard carbon anode derived from lignin raw material. Fig. Figure 3 is a flowchart illustrating a process for forming hard carbon, suitable for use in the Fig. 2 hard carbon anode shown.

[0028] The following section refers in detail to several examples of the description illustrated in the accompanying drawings. Wherever possible, the same or similar reference numerals are used in the drawings and the description to indicate identical or similar parts or steps. The following description is merely exemplary and is not intended to limit the present description, application, or uses.

[0029] Hard carbon materials can be produced by the pyrolysis of organic materials. Conventional hard carbon is manufactured from a variety of starting materials, including resins (e.g., resin, Bakelite), coal tar, biopolymers (e.g., cellulose, chitin, lignin), and so on. When used as anode material, hard carbon anodes have a fast charging capability but a low temperature capability. Hard carbon anodes exhibit significant performance variations depending on the starting material. The best hard carbons are formed from resins but are also the most expensive. The cheapest hard carbons are bio-based or made from coal tar but also have the poorest performance and lack morphology control.The hard carbon and hard carbon anode described here comprise a hard carbon derived from the pyrolysis of a thermoset material using starting materials including lignin, glycerol, and / or ethylene glycol with an acid catalyst and crosslinking reagents. This hard carbon enables a more cost-effective production of hard carbon anodes because much of the biomass used as starting material includes biowaste, including lignin and crude glycerol, which can facilitate morphological tunability. Furthermore, the use of biowaste as a starting material for the production of thermoset polymers allows for morphological control and tunability of the polymers prior to pyrolysis, which in turn allows for control over the properties (e.g., morphology) of the final hard carbon product.

[0030] In Fig. Figure 1 shows a perspective view of a vehicle 10 with a battery pack 12 as described herein. The battery pack 12 is shown with an exemplary vehicle 10. The vehicle 10 is an electric or hybrid vehicle with wheels 11 driven by electric motors / inverters 13. The electric motors / inverters 13 are supplied with power by the battery pack 12. Although the vehicle 10 is shown as a passenger car, the battery pack 12 can also be used for various other types of vehicles. For example, the battery pack 12 can be used in watercraft, such as boats, or in aircraft, such as drones or passenger aircraft. In addition, the battery pack 12 can be used separately and independently of a vehicle as a stationary power source. The battery pack 12 includes a housing 14 for accommodating a plurality of battery cells 18.In one example, the battery pack can contain 12 fifty or more battery cells 18.

[0031] Fig. Figure 2 shows a perspective view of a battery 20, which, according to one aspect of the present description, is located within the in Fig. The battery packs 12 shown in Figure 1 are arranged in a housing 22. Each battery 20 has a housing 22 or compartment and at least one electrode stack 24 comprising a cathode 26, a lignin-derived hard carbon anode 28, an electrolyte 30, and a separator 31. Each battery 20 can have dozens or hundreds of electrode stacks 24 with the hard carbon anodes 28. The electrode stacks 24 are inserted into the housing 22, which is filled with a suitable electrolyte 30, and the electrode stacks 24 conduct electrical current to an external circuit (not shown). The separator 31 is generally a thin porous membrane or layer of material arranged between the anode 28 and the cathode 26, preventing the anode 28 and the cathode 26 from touching and causing a short circuit. The ions (for example, lithium ions) can pass through the separator 31 and complete the circuit.

[0032] Referring to Fig. 2. The lignin-derived hard carbon anode 28 is formed from hard carbon, as described above. A positive charge / current flows into the battery 20 from an external circuit through the hard carbon anode 28. Hard carbon is a low-density material with extremely high microporosity and is commonly used as an anode material in lithium-ion and sodium-ion batteries. A hard carbon anode 28 offers a relatively higher reversible capacity and cycle stability than a graphite anode due to the larger interlayer spacing. Furthermore, hard carbon has an enriched microcrystalline structure that allows for the uptake of more Li + Ions are favored, and the storage and removal of Li + Ions facilitated.

[0033] With reference to Fig.Section 3 presents a process 100 for the formation of hard carbon according to the present description. The process begins in block 102.

[0034] Block 102 shows the liquefaction of lignin in at least one of glycerol or glycerol / ethylene glycol solutions with an acid catalyst to form a first monomer of liquefied lignin. Lignin is a class of complex organic polymers that form key structures in the supporting tissue of plants and are obtained as a byproduct of the pulp and paper industry and biorefineries. Suitable types of lignin for liquefaction include kraft lignin, enzymatic lignin, sulfonated lignin, lignocellulose, and / or alkyl lignin. Suitable acid catalysts include sulfuric acid, phosphoric acid, nitric acid, and / or hydrochloric acid. The liquefaction of lignin may involve liquefaction of the lignin in a solvent, for example, glycerol (e.g., purified, crude), glycerol / ethylene glycol, polyethylene glycol, and / or diethylene glycol.Crude glycerin is a low-value byproduct produced in large quantities by the biodiesel industry; it is inexpensive and a potential renewable feedstock. In one example, the lignin liquefaction process involves between 10 wt% and 90 wt% lignin, between 10 wt% and 90 wt% crude glycerin, and between 0.1 wt% and 50 wt% acid catalyst. The process then proceeds to Block 104.

[0035] Block 104 shows the provision of a second monomer, comprising a cross-linking agent, to the first monomer of the liquefied lignin. Adding the second monomer to the first facilitates the controlled polymerization of the liquefied lignin, producing a thermoset or resin, which contributes to the controlled size and morphology of the resulting resin or thermoset. The first monomer comprises the liquefied lignin, including the lignin itself, the solvent (for example, glycerin, glycerin / ethylene glycol), and / or the acid catalyst. The second monomer, or cross-linking agent, may comprise, for example, an epoxide, isocyanate, formaldehyde, an acid, an acid chloride, and / or an ester. In one example, the first and second monomers are added and mixed in a ratio of 10 wt% / 90 wt%.It goes without saying that other ratios of first monomer and second monomer are also possible (for example, 15 wt% / 85 wt%, 20 wt% / 80 wt% and so on).

[0036] Since the first and second monomers are mixed, the polymerization of the monomers can involve a variety of processes. For example, polymerization can include bulk polymerization, spray polymerization, emulsion polymerization, and / or extrusion polymerization. A bulk polymerization reaction can be initiated by applying heat or irradiating the first and second monomers. As the polymerization reaction progresses, the mixture becomes more viscous and eventually forms the resin or thermoset. Spray polymerization involves forming the polymer using tiny droplets. Some examples of spray polymerization include thermal spraying, electrospraying, spray drying, ultrasonic spraying, and / or electrically assisted subsonic and supersonic blowing. In emulsion polymerization, the monomers and the colloidal particles containing the polymer form are mixed.Extrusion polymerization occurs when the polymer material, including the first and second monomers, is fed into an extruder that conveys the polymer material. As the polymer material moves through the extruder, heat softens and melts the polymer material, which is forced through a die, resulting in the formation of the polymer and / or resin. Process 100 then proceeds to Block 106.

[0037] Block 106 shows the pyrolysis of the resin to form the hard carbon with a controlled morphology. The pyrolysis of the resin involves the thermal decomposition of the resin in an inert or oxygen-free environment. The pyrolysis of the resin may include heating the resin to a temperature between 700°C and 1600°C in an inert and / or oxygen-free environment to form hard carbon with a spherical morphology, which may be particularly suitable for use in a hard carbon anode 28. The process 100 then terminates.

[0038] The hard carbon, process, and hard carbon anode described herein are advantageous and beneficial compared to the prior art. The hard carbon described here is derived from the pyrolysis of thermoset material (resin) using starting materials comprising lignin, glycerol, and / or ethylene glycol, with an acid catalyst and crosslinking reagents. This hard carbon enables a more cost-effective production of hard carbon anodes, as much of the biomass used as starting material comprises biowaste, including, for example, lignin and crude glycerol. Furthermore, the use of biowaste as a starting material for the production of thermoset polymers allows for control of the polymer morphology and adjustability prior to pyrolysis, which in turn allows for control over the properties of the hard carbon.

Claims

[1] Method (100) for forming hard carbon, comprising: Liquefaction (102) of lignin in at least one of glycerol or glycerol / ethylene glycol with an acid catalyst to form a first monomer of liquefied lignin; Providing (104) a second monomer comprising a cross-linking reagent for the first monomer from liquefied lignin to enable controlled polymerization, resulting in a resin with controlled size and morphology; and Pyrolysis (106) of the resin to form the hard carbon with a controlled morphology, wherein the first monomer and the second monomer are provided in a ratio of 10 wt.% to 90 wt.%. [2] Method (100) according to claim 1, wherein the lignin comprises at least one of kraft lignin, enzymatic lignin, sulfonated lignin or alkyl lignin. [3] Method (100) according to claim 1, wherein the lignin constitutes between 10 wt.% and 90 wt.% of the liquefied lignin. [4] Method (100) according to claim 1, wherein the liquefaction of the lignin comprises the use of glycerin in an amount between 10 wt.% and 90 wt.% of the liquefied lignin. [5] Method (100) according to claim 1, wherein the liquefaction of the lignin comprises the use of glycerin / ethylene glycol in an amount between 10 wt.% and 90 wt.% of the liquefied lignin. [6] Method (100) according to claim 1, wherein the acid catalyst comprises between 0.1 wt.% and 50 wt.% of the liquefied lignin. [7] Method (100) according to claim 1, wherein the acid catalyst comprises at least one of phosphoric acid or hydrochloric acid. [8] Method (100) according to claim 1, wherein the acid catalyst comprises at least one of nitric acid or sulfuric acid. [9] Method (100) according to claim 1, wherein the cross-linking reagent comprises at least one of epoxide or isocyanate. [10] Method (100) according to claim 1, wherein the cross-linking reagent comprises at least one of formaldehyde or an ester.

Images