Hard carbon preparation method, battery cell, and electrical device

Abstract

The present application discloses a hard carbon preparation method, a battery cell, and an electrical device. The preparation method comprises the following steps: mixing a first starch-based material and an inhibitor to obtain a mixture, wherein the inhibitor comprises a hard carbon precursor capable of being used to prepare hard carbon; and carbonizing the mixture to obtain the hard carbon. In the technical solution of the present application, an inhibitor is added to a starch-based material to facilitate the inhibition of foaming and expansion of the starch-based material, thereby reducing damage to the microstructure of the hard carbon and accordingly improving the specific capacity of the hard carbon.

Description

Preparation methods of hard carbon, battery cells and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202510080246.2, filed on January 17, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, specifically to a method for preparing hard carbon, a battery cell, and an electrical device. Background Technology

[0004] Batteries have the characteristics of high energy density, high operating voltage, and light weight, so they are widely used in products such as mobile phones, laptops, cameras, and vehicles.

[0005] Hard carbon is a type of carbon that is difficult to graphitize, even at high temperatures of 2500℃, it is hard to transform into a graphite structure. Hard carbon typically has a disordered internal crystal arrangement and large interlayer spacing, and is often used in the negative electrode materials of batteries. Starch-based materials are one of the commonly used precursors for preparing hard carbon, but starch-based materials are prone to foaming and expansion, which damages the microstructure of the prepared hard carbon and leads to a decrease in specific capacity. Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to provide a method for preparing hard carbon, a battery cell and an electrical device to improve the specific capacity of hard carbon.

[0007] To achieve the above objectives, in a first aspect, this application provides a method for preparing hard carbon, comprising the following steps: mixing a first starch-based material and an inhibitor to obtain a mixture; wherein the inhibitor includes a hard carbon precursor capable of being used to prepare hard carbon; and carbonizing the mixture to prepare the hard carbon.

[0008] In the technical solution of this application, an inhibitor is added to the starch-based material, which helps to suppress the foaming and expansion of the starch-based material, thereby reducing the damage of expansion to the microstructure of hard carbon and thus helping to improve the specific capacity of hard carbon.

[0009] In any embodiment, the inhibitor includes a first inhibitor, which comprises at least one of a carbohydrate material and a second starch material. Adding the first inhibitor helps to reduce damage to the microstructure of hard carbon, thereby improving the specific capacity of hard carbon.

[0010] In any embodiment, the carbohydrate material includes at least one selected from glucose, fructose, maltose, and sucrose. Using a suitable carbohydrate material as described above helps to suppress the foaming and expansion of the first starch material.

[0011] In any embodiment, the first starch material and the second starch material are selected from two of cereal starch, potato starch, and legume starch; or, the first starch material and the second starch material are selected from two of cereal starch; or, the first starch material and the second starch material are selected from two of potato starch; or, the first starch material and the second starch material are selected from two of legume starch.

[0012] In any embodiment, cereal starch includes wheat starch, corn starch, glutinous corn starch, rice starch, or glutinous rice starch; and / or, tuber starch includes sweet potato starch, potato starch, or cassava starch; and / or, legume starch includes mung bean starch, pea starch, broad bean starch, or red bean starch. Using the aforementioned suitable second starch material helps to suppress the foaming and expansion of the first starch material.

[0013] In any embodiment, the first inhibitor accounts for 20% to 50% of the mass of the mixture. Using an appropriate amount of the first inhibitor helps to suppress the foaming and expansion of starch-based materials and avoids their own foaming and expansion.

[0014] In any embodiment, the inhibitor includes a second inhibitor, which comprises at least one of cellulose-based materials, plant fragments, and polymeric materials. Using a second inhibitor that does not itself exhibit foaming and expansion is beneficial for suppressing the foaming and expansion of starch-based materials, thereby reducing damage to the microstructure of hard carbon and ultimately improving the specific capacity of hard carbon.

[0015] In any embodiment, the cellulosic material includes at least one of cellulose, hemicellulose, and lignin; and / or, the plant crushed powder includes at least one of coconut shell powder, bamboo powder, and walnut shell powder; and / or, the polymeric material includes at least one of polyaniline and polypyrrole. Using the aforementioned suitable second inhibitor is beneficial for suppressing the foaming and expansion of starch-based materials.

[0016] In any embodiment, the second inhibitor accounts for 10% to 50% of the mass of the mixture. Using an appropriate amount of the second inhibitor helps to suppress the foaming and expansion of the first starch material while preserving the structural characteristics of the first starch material itself.

[0017] In any embodiment, the volumetric particle size distribution of the inhibitor satisfies 10 μm ≤ Dv50 ≤ 50 μm; the volumetric particle size distribution of the first starch-based material satisfies 10 μm ≤ Dv50 ≤ 50 μm. Controlling the median particle size Dv50 of the inhibitor to a range similar to that of the median particle size Dv50 of the first starch-based material is beneficial for exerting the inhibitor's anti-foaming effect on the first starch-based material.

[0018] In any embodiment, the step of carbonizing the mixture to prepare the hard carbon includes:

[0019] The mixture is pre-carbonized under a protective gas atmosphere;

[0020] The pre-carbonized mixture is carbonized under a protective gas atmosphere to prepare the hard carbon; wherein the carbonization temperature is higher than the pre-carbonization temperature.

[0021] Secondly, this application provides a battery cell including a negative electrode sheet, said negative electrode sheet comprising hard carbon prepared according to the preparation method of the first aspect of this application.

[0022] Thirdly, this application provides an electrical device including a battery cell as described in the second aspect of this application. Attached Figure Description

[0023] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0024] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0025] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0026] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0027] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4;

[0028] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0029] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0030] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the hard carbon preparation method, battery cell, and power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0036] Starch-based materials are commonly used precursors in the preparation of hard carbon, but they are prone to foaming and expansion, which damages the microstructure of the resulting hard carbon and leads to a decrease in specific capacity. Currently, several methods exist to prevent this foaming and expansion. One method involves slowing down the heating rate, extending the holding time, and enhancing the degree of starch crosslinking. However, this method requires high precision equipment and significantly reduces production efficiency; for example, commonly used roller kilns cannot meet the requirements of slow heating and extended holding time in their low-temperature sections. Another method involves adding crosslinking agents such as ammonium chloride, phosphoric acid, or epichlorohydrin to accelerate starch crosslinking. This method can shorten the pyrolysis time, but the addition of crosslinking agents introduces impurity ions and causes severe corrosion to the equipment.

[0037] In view of this, in a first aspect, this application provides a method for preparing hard carbon, comprising the following steps: mixing a first starch-based material and an inhibitor to obtain a mixture; wherein the inhibitor comprises a hard carbon precursor capable of being used to prepare hard carbon; and carbonizing the mixture to prepare the hard carbon.

[0038] In this article, "hard carbon precursor" can refer to a raw material that can be used to prepare hard carbon, which can form hard carbon after carbonization treatment.

[0039] In the technical solution of this application, an inhibitor is added to the starch-based material, which helps to suppress the foaming and expansion of the starch-based material, thereby reducing the damage to the microstructure of hard carbon and thus helping to improve the specific capacity of hard carbon.

[0040] The inventors discovered that, due to the low melting point of starch-based materials, they melt in the early stages of pyrolysis. As the temperature continues to rise, pyrolysis produces a large amount of volatiles, causing the melt to foam and expand. The fundamental reason for this foaming expansion is that the raw materials first melt and then undergo thermal decomposition during pyrolysis. Due to surface tension, a dense liquid film forms on the surface of the melt. Subsequently, as the temperature increases and the pyrolysis process continues, a large amount of volatiles escape, encountering resistance from the liquid film and causing foaming and expansion.

[0041] In the technical solution of this application, a hard carbon precursor that can be used to prepare hard carbon is added to starch-based materials. The mixing of different raw materials affects the thermal decomposition process of starch. The thermal decomposition temperature may be lower than the melting temperature of the mixture, or thermal decomposition and melting may occur simultaneously. This helps to avoid foaming caused by the liquid film formed by melting encapsulating volatiles, thereby helping to suppress the foaming and expansion of starch-based materials.

[0042] In some embodiments, the inhibitor includes a first inhibitor, which comprises at least one of a carbohydrate material and a second starch material. Adding the first inhibitor prevents foaming and expansion, thereby reducing damage to the microstructure of hard carbon and thus improving its specific capacity.

[0043] In some embodiments, the sugar material includes at least one selected from glucose, fructose, maltose, and sucrose. In any embodiment, the sugar material includes at least one selected from glucose, fructose, maltose, and sucrose. Using the above-mentioned suitable sugar material is beneficial for suppressing the foaming and expansion of the first starch material.

[0044] In some embodiments, the first starch material and the second starch material are selected from two of cereal starch, potato starch, and legume starch; or, the first starch material and the second starch material are selected from two of cereal starch; or, the first starch material and the second starch material are selected from two of potato starch; or, the first starch material and the second starch material are selected from two of legume starch. The first starch material and the second starch material can be used in various combinations described above. Adding other starch materials different from the first starch material to the first starch material helps to suppress the foaming and expansion of the first starch material.

[0045] In some embodiments, cereal starch includes wheat starch, corn starch, glutinous corn starch, rice starch, or glutinous rice starch; and / or, tuber starch includes sweet potato starch, potato starch, or cassava starch; and / or, legume starch includes mung bean starch, pea starch, broad bean starch, or red bean starch. Using the aforementioned suitable second starch material helps to suppress the foaming and swelling of the first starch material.

[0046] In some embodiments, the first inhibitor comprises 20% to 50% of the mixture by mass. Using an appropriate amount of the first inhibitor helps to suppress the foaming and swelling of starch-based materials and avoids its own foaming and swelling. The mass percentage of the first inhibitor in the mixture can be any range of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or more.

[0047] In some embodiments, the inhibitor includes a second inhibitor, which comprises at least one of cellulosic materials, plant fragments, and polymeric materials. Using a second inhibitor that does not itself exhibit foaming and expansion is beneficial for suppressing the foaming and expansion of starch-based materials, thereby reducing damage to the microstructure of hard carbon and ultimately improving the specific capacity of hard carbon.

[0048] In some embodiments, the cellulosic material includes at least one of cellulose, hemicellulose, and lignin; and / or, the plant crushed powder includes at least one of coconut shell powder, bamboo powder, and walnut shell powder; and / or, the polymeric material includes at least one of polyaniline and polypyrrole. Using the aforementioned suitable second inhibitor is beneficial for suppressing the foaming and swelling of starch-based materials.

[0049] In some embodiments, the second inhibitor comprises 10% to 50% by mass in the mixture. Using an appropriate amount of the second inhibitor helps to suppress the foaming and expansion of the first starch-based material while preserving its structural characteristics. The mass percentage of the second inhibitor in the mixture can be any range of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or more.

[0050] In some embodiments, the volumetric particle size distribution of the inhibitor satisfies 10 μm ≤ Dv50 ≤ 50 μm; the volumetric particle size distribution of the first starch-based material satisfies 10 μm ≤ Dv50 ≤ 50 μm. Controlling the median particle size Dv50 of the inhibitor to a range similar to the median particle size Dv50 of the first starch-based material is beneficial for exerting the inhibitor's anti-foaming effect on the first starch-based material. The volumetric particle size distribution Dv50 of the inhibitor can be any range consisting of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or more. The volumetric particle size distribution Dv50 of the first starch-based material can be any range consisting of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or more.

[0051] The Dv50 of a material has a well-known meaning in the art and can be determined using instruments and methods known in the art. For example, it can be determined using a laser particle size analyzer (such as the Malvern Mastersizer 3000) according to GB / T 19077-2016. The physical definition of Dv50 is the particle size corresponding to a cumulative volume distribution percentage of 50% for the material.

[0052] In some embodiments, the step of carbonizing the mixture to prepare the hard carbon includes:

[0053] The mixture is pre-carbonized under a protective gas atmosphere;

[0054] The pre-carbonized mixture is carbonized under a protective gas atmosphere to prepare the hard carbon; wherein the carbonization temperature is higher than the pre-carbonization temperature.

[0055] Thus, impurities and volatile substances are removed through pre-carbonization, and the mixture is converted into hard carbon through carbonization treatment. As an example, the protective gas can be nitrogen.

[0056] Secondly, this application provides a battery cell including a negative electrode sheet, said negative electrode sheet comprising hard carbon prepared according to the preparation method of the first aspect of this application.

[0057] A single battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0058] [Positive electrode plate]

[0059] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0060] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0061] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] In some embodiments, when the battery cell is a sodium-ion battery cell, the positive electrode active material may further include positive electrode active materials known in the art for use in sodium-ion batteries. For example, the positive electrode active material is selected from one or more of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0063] In layered transition metal oxides, the transition metal can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, Na is a layered transition metal oxide. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0064] Polyanionic compounds can be those containing sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0065] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0066] Polyanionic compounds can also be sodium ion-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0067] In some embodiments, the polyanionic compound is, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' being one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0068] In some embodiments, the Prussian blue analogue may be a compound containing sodium ions, transition metal ions, and cyanide ions (CN). -A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue analogues include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0069] In some embodiments, the specific positive electrode active material is, for example, NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, NaMnFe(CN)6, but there are no particular restrictions, so conventional positive electrode active materials used in sodium-ion batteries can be selected.

[0070] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0071] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0072] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0073] [Negative electrode plate]

[0074] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0075] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0076] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0078] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0079] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0080] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0081] [Electrolytes]

[0082] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0083] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes the electrolyte provided in the first aspect of this application. In some embodiments, the electrolyte salt is selected from the sodium salt electrolyte, which is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium difluorooxalate borate (NaDFOB), sodium tetrafluoroborate (NaBF4), sodium bis(fluoromethyl sulfonate) borate (NaBOB), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0084] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0085] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0086] In some embodiments, the material of the separator base film can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0087] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0088] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0089] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0090] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0091] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0092] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0093] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0094] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0095] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0096] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0097] Thirdly, this application proposes an electrical device comprising the battery cell provided in the second aspect.

[0098] The electrical device includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0099] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0100] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0101] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0102] Example

[0103] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0104] Example 1

[0105] Preparation of hard carbon: 500g of corn starch and 500g of cellulose were thoroughly mixed by mechanical ball milling for 8 hours, then transferred to a box furnace and calcined at 400℃ for 2 hours under nitrogen protection at a heating rate of 5℃ / min, followed by cooling. The powder was then transferred to a nitrogen-protected furnace for a second calcination at 1200℃ for 2 hours. After cooling to room temperature, the final product, hard carbon, was obtained. The Dv50 of the corn starch was 15μm, and the Dv50 of the cellulose was 35μm.

[0106] Preparation of negative electrode sheet: The negative electrode material (hard carbon obtained above), conductive agent (SP-Li), binder (SD-3), thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water at a ratio of 95:1.74:2.3:0.96 and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil in one step, and then dried and cold pressed.

[0107] The counter electrode is a sodium metal sheet.

[0108] Electrolyte preparation:

[0109] The electrolyte solvent was prepared by mixing ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1. Sodium hexafluorophosphate was then mixed with the mixed solvent to prepare an electrolyte with a sodium salt concentration of 1 mol / L.

[0110] Separator membrane: Polypropylene membrane is used as the separator membrane.

[0111] The above-mentioned positive electrode, separator, and negative electrode are assembled into a button cell.

[0112] Examples 2-9 and Comparative Example 1 of this application use a preparation method similar to that of Example 1. The differences are shown in Table 1.

[0113] Performance testing:

[0114] (1) The button cells prepared in Examples 1 to 9 and Comparative Example 1 were tested as follows. The test results are shown in Table 1:

[0115] 1. Determination of specific capacity of hard carbon:

[0116] The prepared coin cells were tested using a Xinwei 5V 10mA test cabinet. The testing process involved constant current discharge at 0.1C for 2 hours, followed by constant current discharge at 0.05C to the lower limit voltage of 0.05V. After resting for 5 minutes, the cells were charged at 0.1C to the upper limit voltage of 2.0V. The actual charging capacity of the coin cells was recorded. Hard carbon specific capacity = actual charging capacity of coin cells / [hard carbon mass percentage × (electrode mass - current collector mass)] × 100%.

[0117] 2. Battery energy density measurement:

[0118] At 25°C, the prepared coin cell was fully charged and fully discharged at a rate of 0.5C, and the actual discharge energy was recorded. At 25°C, the coin cell was weighed using an electronic balance. The ratio of the actual discharge energy of the coin cell at 0.5C to the weight of the coin cell is the energy density of the coin cell.

[0119] Table 1. Hard carbon and battery performance parameters of Examples 1-9 and Comparative Example 1

[0120] As can be seen from the test results in Table 1, compared with Comparative Example 1, Examples 1-9 of this application use inhibitors added to starch-based materials, which can suppress the foaming and expansion of starch-based materials, improve the specific capacity of hard carbon, and result in higher battery energy density. Comparative Example 1, however, did not add inhibitors during the preparation of hard carbon, resulting in lower specific capacity of its hard carbon and lower battery energy density.

[0121] As can be seen from Examples 1-9, by adding different inhibitors and adjusting the amount of inhibitors added, the specific capacity of hard carbon and the energy density of the battery can be further optimized.

[0122] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing hard carbon, characterized in that, Includes the following steps: A mixture is prepared by mixing a first starch-based material with an inhibitor; wherein the inhibitor includes a hard carbon precursor that can be used to prepare hard carbon. The mixture is subjected to carbonization treatment to obtain the hard carbon.

2. The preparation method according to claim 1, characterized in that, The inhibitor includes a first inhibitor, which includes at least one of a carbohydrate material and a second starch material.

3. The preparation method according to claim 2, characterized in that, The sugar material includes at least one of glucose, fructose, maltose, and sucrose.

4. The preparation method according to claim 2, characterized in that, The first starch material and the second starch material are selected from two of cereal starch, potato starch, and legume starch; or, the first starch material and the second starch material are selected from two of cereal starch; or, the first starch material and the second starch material are selected from two of potato starch; or, the first starch material and the second starch material are selected from two of legume starch.

5. The preparation method according to claim 4, characterized in that, The cereal starches include wheat starch, corn starch, glutinous corn starch, rice starch, or glutinous rice starch; and / or, the tuber starches include sweet potato starch, potato starch, or cassava starch; and / or, the legume starches include mung bean starch, pea starch, broad bean starch, or red bean starch.

6. The preparation method according to claim 2, characterized in that, The first inhibitor accounts for 20% to 50% of the mass of the mixture.

7. The preparation method according to claim 1, characterized in that, The inhibitor includes a second inhibitor, which includes at least one of cellulosic materials, plant fragments, and polymer materials.

8. The preparation method according to claim 7, characterized in that, The cellulosic materials include at least one of cellulose, hemicellulose, and lignin; and / or, The plant-based crushed powder includes at least one of coconut shell powder, bamboo powder, and walnut shell powder; and / or The polymer material includes at least one of polyaniline and polypyrrole.

9. The preparation method according to claim 7, characterized in that, The second inhibitor constitutes 10% to 50% of the mass of the mixture.

10. The preparation method according to any one of claims 1 to 9, characterized in that, The volume distribution particle size of the inhibitor satisfies 10μm≤Dv50≤50μm; the volume distribution particle size of the first starch-based material satisfies 10μm≤Dv50≤50μm.

11. The preparation method according to any one of claims 1 to 9, characterized in that, The step of carbonizing the mixture to prepare the hard carbon includes: The mixture is pre-carbonized under a protective gas atmosphere; The pre-carbonized mixture is carbonized under a protective gas atmosphere to prepare the hard carbon; wherein the carbonization temperature is higher than the pre-carbonization temperature.

12. A single battery cell, characterized in that, Includes a negative electrode sheet, said negative electrode sheet comprising hard carbon prepared by the preparation method according to any one of claims 1 to 11.

13. An electrical appliance, characterized in that, Includes the battery cell as described in claim 12.

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