Battery monomer, silicon-carbon composite material, preparation method of silicon-carbon composite material, battery device and power utilization device

Abstract

The invention discloses a battery monomer, a silicon-carbon composite material, a preparation method, a battery device and a power utilization device, the battery monomer comprises a first pole piece, the first pole piece comprises the silicon-carbon composite material, and the silicon-carbon composite material comprises porous carbon and silicon particles located in pores of the porous carbon; and the grain size of the silicon particles is 2-12 nm. According to the embodiment of the invention, a containing space is provided for the silicon particles through the porous carbon so as to relieve volume expansion of the silicon particles; the reaction duration of the silicon-lithium alloy is regulated and controlled through silicon particles with the grain size meeting the requirement of 2-12 nm, the excessive reaction of the silicon-carbon composite material in the lithium intercalation process is reduced, the amount of silicon-lithium irreversible by-products is reduced, due to the reasonable regulation and control of the reaction duration of the silicon-lithium alloy, large expansion stress borne by the silicon particles in a period of time is relieved, pulverization and falling of a pole piece are reduced, and the service life of the pole piece is prolonged. And the integrity of silicon particles is improved.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a battery cell, a silicon-carbon composite material and its preparation method, a battery device and an electrical device. Background Technology

[0002] This section provides only background information relevant to this application and is not necessarily prior art.

[0003] Battery cells possess high energy density and are widely used in wireless communication, transportation, aerospace, and other fields. A battery cell mainly consists of a positive electrode, a separator, an electrolyte, and a negative electrode. Silicon has a theoretical specific capacity as high as 4200 mAh / g, making it a promising anode material. Therefore, seeking battery cells with superior performance is one of the key areas of focus for those skilled in the art.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a battery cell, a silicon-carbon composite material and a preparation method thereof, a battery device and an electrical device, aiming to improve the first coulombic efficiency of the battery cell.

[0006] To achieve the above objectives, a first aspect of this application provides a battery cell, comprising:

[0007] The first electrode includes a first current collector and a first film layer disposed on at least one surface of the first current collector;

[0008] The first film layer includes a first active material, which includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon particles located in the pores of the porous carbon. The grain size of the silicon particles is between 2 nm and 12 nm.

[0009] The embodiments of this application provide a silicon-carbon composite material by improving the battery cell. This silicon-carbon composite material provides space for silicon particles through porous carbon to alleviate the volume expansion of silicon particles. By controlling the reaction time of the silicon-lithium alloy with silicon particles of 2nm to 12nm grain size, the excessive reaction of the silicon-carbon composite material during lithium intercalation is reduced, and the amount of irreversible byproducts of silicon-lithium is reduced. Due to the reasonable control of the reaction time of the silicon-lithium alloy, the large expansion stress on silicon particles in a short time is reduced, the electrode pulverization and shedding are reduced, and the integrity of silicon particles is improved. In addition, the reasonable control of the reaction time of the silicon-lithium alloy is also conducive to improving the lithium intercalation utilization rate of silicon particles and improving the first coulombic efficiency of the battery cell.

[0010] In some embodiments, with the first electrode as the positive electrode and the lithium metal sheet as the negative electrode, when discharged from 0.33C to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of silicon particles in the range of 0.4V to 0.5V.

[0011] The embodiments of this application, by adjusting the grain size of silicon particles, enable a battery cell to discharge at 0.33C to 0.8V with the first electrode as the positive electrode and the lithium metal sheet as the negative electrode. The capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of silicon particles at the position of 0.4V to 0.5V. The battery cell using this electrode has good first coulombic efficiency.

[0012] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles ranges from 2 mAh / V to 12 mAh / V.

[0013] The embodiments of this application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles so that the battery cell using this electrode has good first coulombic efficiency.

[0014] In some embodiments, the first electrode further includes one or more of the following features:

[0015] (1) The areal density of the first film layer satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 ;

[0016] (2) The compaction density of the first membrane layer satisfies 1.3 g / cc to 1.7 g / cc;

[0017] (3) The weight ratio of silicon-carbon composite material in the first film layer is 40% to 60%;

[0018] (4) The first active material also includes graphite, and the weight percentage of graphite in the first film layer is 40% to 60%.

[0019] (5) The first film layer also includes a first conductive agent, a first binder, and a thickener;

[0020] Optionally, the first conductive agent includes one or more of carbon black, carbon nanotubes, graphite, graphene and carbon nanofibers, and / or the first binder includes one or more of styrene-butadiene rubber, polyacrylic acid, lithium-ionized polyacrylic acid, and / or the thickener includes sodium carboxymethyl cellulose.

[0021] Optionally, the mass ratio of the first active material, the first conductive agent, the first binder and the thickener satisfies 94-95:1-1.5:2.5-3.5:1-1.5.

[0022] The embodiments of this application achieve good initial coulombic efficiency in a single battery cell by adjusting various parameters of the first electrode.

[0023] In some embodiments, the battery cell further includes a second electrode, the second electrode including a second current collector and a second film layer disposed on at least one surface of the second current collector, the second film layer containing a second active material; the battery cell uses the second electrode as the positive electrode and the first electrode as the negative electrode;

[0024] The second electrode includes one or more of the following characteristics:

[0025] (1) The areal density of the second electrode satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 ;

[0026] (2) The compaction density of the second electrode sheet satisfies 1.3 g / cc to 1.6 g / cc;

[0027] (3) The second active material includes one or more of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese iron phosphate, and their respective modified compounds.

[0028] (4) The second electrode also includes a second conductive agent and a second binder;

[0029] Optionally, the second conductive agent includes carbon black, and / or the second binder includes polyvinylidene fluoride;

[0030] Optionally, the mass ratio of the second active material, the second conductive agent, and the second binder satisfies 96–98:0.5–1.5:1–3;

[0031] The battery cell also includes the following characteristics: the mass energy density of the battery cell meets the requirements of 380Wh / kg to 500Wh / kg.

[0032] The embodiments of this application achieve good initial coulombic efficiency in a single battery cell by adjusting various parameters of the second electrode.

[0033] In some embodiments, the battery cell includes an electrolyte; the electrolyte includes an electrolyte salt and a solvent; or, the electrolyte includes an electrolyte salt, a solvent, and additives.

[0034] The embodiments of this application achieve good initial coulombic efficiency in battery cells by adjusting the electrolyte of the battery cells, including the first electrode and the second electrode.

[0035] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0036] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%;

[0037] (2) Silicon-carbon composite materials also include a carbon coating layer, which is coated on the surface of porous carbon.

[0038] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0039] In some embodiments, porous carbon includes one or more of the following features:

[0040] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm;

[0041] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g;

[0042] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g;

[0043] (4) In the pores of porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%;

[0044] (5) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%. The embodiments of this application achieve good first coulombic efficiency of battery cells including silicon-carbon composite materials by adjusting various parameters of porous carbon.

[0045] Secondly, embodiments of this application provide a silicon-carbon composite material, which includes porous carbon and silicon particles located within the pores of the porous carbon; the grain size of the silicon particles satisfies 2nm to 12nm.

[0046] The embodiments of this application provide a silicon-carbon composite material, which provides a space for silicon particles through porous carbon to alleviate the volume expansion of silicon particles; by controlling the reaction time of silicon-lithium alloy by silicon particles with a grain size of 2nm to 12nm, the lithium intercalation utilization rate of silicon particles is improved, the expansion stress of silicon particles is reduced, and the integrity of silicon particles is improved, thereby improving the first coulombic efficiency of battery cells.

[0047] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0048] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%;

[0049] (2) Silicon-carbon composite materials also include a carbon coating layer, which is coated on the surface of porous carbon.

[0050] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0051] In some embodiments, when an electrode comprising silicon-carbon composite material is used as the positive electrode and a lithium metal sheet is used as the negative electrode, and the discharge is carried out at 0.1C to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of silicon particles in the range of 0.4V to 0.5V.

[0052] The embodiments of this application, by controlling the grain size of silicon particles, enable the use of an electrode comprising silicon-carbon composite material as the positive electrode and a lithium metal sheet as the negative electrode, to discharge from 0.33C to 0.8V. The capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of silicon particles at the position of 0.4V to 0.5V. The battery cell using this electrode has good first coulombic efficiency.

[0053] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2 mAh / V to 12 mAh / V.

[0054] Embodiments of this application further modulate the peak value of the lithium intercalation phase transition peak of the silicon particles to enable the battery cell using this electrode to have good first-time coulombic efficiency. In some embodiments, the porous carbon includes one or more of the following characteristics:

[0055] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm;

[0056] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g;

[0057] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g;

[0058] (4) In the pores of porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%;

[0059] (5) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%.

[0060] The embodiments of this application achieve good first-run coulombic efficiency in battery cells, including silicon-carbon composite materials, by adjusting various parameters of porous carbon.

[0061] Thirdly, embodiments of this application provide a method for preparing a silicon-carbon composite material, comprising the following steps:

[0062] Porous carbon is provided, which has several pores;

[0063] Silicon particles are deposited into the pores of porous carbon, with the grain size of the silicon particles ranging from 2 nm to 12 nm, to form a silicon-carbon composite material.

[0064] The embodiments of this application provide a method for preparing a silicon-carbon composite material. The silicon-carbon composite material prepared by this method helps to alleviate the volume expansion of silicon particles, improve the lithium intercalation utilization of silicon particles, reduce the expansion stress of silicon particles, and improve the integrity of silicon particles, thereby improving the first coulombic efficiency of the battery cell containing the silicon-carbon composite material.

[0065] In some embodiments, the proportion of pores with a diameter of 2 nm to 10 nm in the porous carbon pores is 80% to 94%. The proportion of pores with a diameter of 2 nm to 10 nm can be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 9... 2.5%, 93%, 93.5%, 94%, etc., or any range of two of the above values, such as 80%–82%, 81%–83%, 82%–84%, 83%–85%, 84%–86%, 85%–87%, 86%–88%, 87%–89%, 88%–90%, 89%–91%, 90%–92%, 91%–93%, 92%–94%, etc.

[0066] The embodiments of this application achieve good first-run coulombic efficiency in battery cells, including silicon-carbon composite materials, by controlling the pore size of porous carbon.

[0067] In some embodiments, prior to the step of providing porous carbon, a step of preparing porous carbon is further included, comprising:

[0068] An organic carbon source is placed in an inert atmosphere and treated at a first temperature for a first duration to obtain a first intermediate.

[0069] The first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more to obtain the second intermediate.

[0070] The second intermediate was placed in a reducing atmosphere, and then treated at a third temperature for a third duration under a reducing gas flow atmosphere. This process was repeated several times to obtain porous carbon.

[0071] The embodiments of this application provide a method for preparing porous carbon in silicon-carbon composite materials. The porous carbon prepared by this method has good surface properties, reduced lithium-consuming groups on the surface of the porous carbon, and the battery cell containing the silicon-carbon composite material has good first coulombic efficiency.

[0072] In some embodiments, placing the organic carbon source in an inert atmosphere and treating it at a first temperature for a first duration includes one or more of the following features:

[0073] (1) Organic carbon sources include polymeric organic carbon sources;

[0074] (2) Polymer organic carbon sources include phenolic resins;

[0075] (3) The first temperature meets the requirement of 880℃~1000℃;

[0076] (4) The first duration is 4h to 8h.

[0077] The embodiments of this application provide a method for activating porous carbon in silicon-carbon composite materials. The first intermediate prepared by this method has fewer defects and fewer lithium-consuming groups on its surface, thereby reducing the lithium consumption of the first intermediate. The battery cell containing this silicon-carbon composite material has good first coulombic efficiency.

[0078] In some embodiments, the first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more, including one or more of the following features:

[0079] (1) The flow rate of the activation gas should be between 0.1 L / min and 0.5 L / min;

[0080] (2) The activated airflow includes water vapor airflow;

[0081] (3) The first intermediate is in the pressure range of 5MPa to 30MPa;

[0082] (4) The second temperature satisfies 600℃~700℃;

[0083] (5) The second duration is between 6h and 16h;

[0084] (6) The number of treatments is any one of 1 to 6.

[0085] The embodiments of this application provide a method for creating porous carbon in silicon-carbon composite materials. The porous carbon prepared by this method has fewer defects and fewer lithium-consuming groups on its surface, thereby reducing the amount of lithium consumed by the porous carbon. In addition, the method can regulate the pore size of the porous carbon so that the pores can have space to accommodate the growth of silicon particles. The battery cell containing this silicon-carbon composite material has good first coulombic efficiency.

[0086] In some embodiments, placing the second intermediate in a reducing atmosphere and treating the second intermediate at a third temperature for a third duration under a reducing gas flow atmosphere includes one or more of the following features:

[0087] (1) Reducing atmospheres include hydrogen;

[0088] (2) The flow rate of the reducing gas stream is 0.1 L / min to 0.5 L / min;

[0089] (3) The third temperature meets the requirement of 450℃~600℃;

[0090] (4) The third duration is 2h to 4h.

[0091] The embodiments of this application provide a method for reducing porous carbon in silicon-carbon composite materials, further reducing the lithium-consuming groups on the surface of porous carbon to reduce the lithium consumption of porous carbon, and the battery cell containing the silicon-carbon composite material has good first coulombic efficiency.

[0092] In some embodiments, the step of depositing silicon particles into the pores of porous carbon includes:

[0093] Porous carbon is placed in an inert atmosphere, and silicon source gas is introduced to perform vapor phase deposition so that silicon particles are located within the pores of the porous carbon.

[0094] The embodiments of this application provide a method for preparing silicon particles in silicon-carbon composite materials. The silicon particles prepared by this method have a large grain size, which allows for control of the reaction time of the silicon-lithium alloy, improves the lithium intercalation utilization rate of the silicon particles, reduces the expansion stress of the silicon particles, and improves the integrity of the silicon particles, thereby improving the first coulombic efficiency of the battery cell.

[0095] In some embodiments, the step of introducing a silicon source gas to perform vapor deposition includes one or more of the following features:

[0096] (1) The silicon source gas includes one or more of the following: silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane;

[0097] (2) The flow rate of the silicon source gas meets the requirement of 0.5L / min~5L / min;

[0098] (3) The deposition temperature of vapor phase deposition meets the requirement of 480℃~600℃;

[0099] (4) The deposition time of vapor phase deposition meets the requirements of 6h to 24h.

[0100] The embodiments of this application provide process parameters for preparing silicon particles in silicon-carbon composite materials. This method can control the grain size of the prepared silicon particles, thereby controlling the reaction time of the silicon-lithium alloy, improving the lithium intercalation utilization rate of the silicon particles, reducing the expansion stress of the silicon particles, and improving the integrity of the silicon particles, so as to improve the first coulombic efficiency of the battery cell.

[0101] In some embodiments, after the step of depositing silicon particles into the pores of porous carbon, the method further includes the step of preparing a carbon coating layer on the surface of the porous carbon or the step of depositing oxygen on the surface of the silicon particles.

[0102] The embodiments of this application improve the stability between the first active material and the electrolyte in a battery cell by either depositing silicon particles into the pores of porous carbon, followed by preparing a carbon coating layer on the surface of the porous carbon, or depositing oxygen on the surface of the silicon particles.

[0103] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0104] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%;

[0105] (2) Silicon-carbon composite materials also include a carbon coating layer, which is coated on the surface of porous carbon.

[0106] The embodiments of this application achieve good first-run coulombic efficiency in battery cells, including silicon-carbon composite materials, by adjusting various parameters of porous carbon.

[0107] In some embodiments, porous carbon includes one or more of the following features:

[0108] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm;

[0109] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g;

[0110] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g;

[0111] (4) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%.

[0112] The embodiments of this application achieve good initial coulombic efficiency in battery cells comprising silicon-carbon composite materials by controlling various parameters of porous carbon. Fourthly, a battery device is provided, characterized in that it comprises any of the battery cells provided in the first aspect.

[0113] The battery device provided by the embodiments of this application has at least the same advantages as a single battery cell, which can improve the battery device's range.

[0114] Fifthly, embodiments of this application provide an electrical device including any of the battery cells provided in the first aspect.

[0115] The electrical device provided in the embodiments of this application has at least the same advantages as a single battery cell, which can improve the battery's range. Attached Figure Description

[0116] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. Other drawings can be obtained based on these drawings without creative effort.

[0117] Figure 1 A schematic diagram of the vehicle structure provided for an embodiment of this application;

[0118] Figure 2 An exploded view of the battery device provided in an embodiment of this application;

[0119] Figure 3 This is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0120] Explanation of icon numbers:

[0121] 1000-Vehicle, 100-Battery unit, 200-Controller, 300-Motor, 10-Box, 20-Battery cell, 11-First part, 12-Second part, 21-End cap, 22-Housing, 23-Electrode assembly, 21a-Electrode terminal. Detailed Implementation

[0122] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0123] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0124] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0125] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0126] Unless otherwise stated, the terms used in this application have their commonly understood meanings in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0127] Silicon undergoes significant volume expansion during charging and discharging, leading to silicon pulverization and shedding, as well as repeated formation of the SEI film on the surface of the silicon anode material. This severely impacts the performance of individual battery cells. Furthermore, silicon has poor conductivity, which also needs improvement. Therefore, while retaining its advantages, it is necessary to address the volume expansion issue of silicon to enhance the initial coulombic efficiency of individual battery cells.

[0128] A current research trend is to improve the initial coulombic efficiency of battery cells using silicon-carbon composite materials. Silicon-carbon composite materials can leverage the ultra-high specific capacity of silicon, while the carbon structure acts as a network scaffold to mitigate the volume expansion of silicon during charging and discharging. Furthermore, carbon's good electrical conductivity helps to address the poor conductivity of silicon in composite materials.

[0129] However, currently, silicon-carbon composite materials generally use silicon with a small average particle size (e.g., an average particle size Dv50 less than or equal to 2nm). The silicon-lithium reaction rate is too fast, and the volume expands rapidly in a short time. The silicon-carbon composite material is subjected to large expansion stress in a short time, which can easily lead to the electrode pulverization and detachment. Moreover, some silicon does not have time to react before the silicon-lithium reaction ends, which can easily lead to insufficient silicon lithium intercalation utilization, resulting in a low initial coulombic efficiency of the battery cell.

[0130] The embodiments of this application provide a silicon-carbon composite material by improving the battery cell. This silicon-carbon composite material provides space for silicon particles through porous carbon to alleviate the volume expansion of silicon particles. By controlling the reaction time of the silicon-lithium alloy with silicon particles of 2nm to 12nm grain size, the excessive reaction of the silicon-carbon composite material during lithium intercalation is reduced, and the amount of irreversible byproducts of silicon-lithium is reduced. Due to the reasonable control of the reaction time of the silicon-lithium alloy, the large expansion stress on silicon particles in a short time is reduced, the electrode pulverization and shedding are reduced, and the integrity of silicon particles is improved. In addition, the reasonable control of the reaction time of the silicon-lithium alloy is also conducive to improving the lithium intercalation utilization rate of silicon particles and improving the first coulombic efficiency of the battery cell.

[0131] battery cell

[0132] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0133] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0134] Battery device

[0135] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0136] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0137] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0138] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0139] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0140] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0141] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0142] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0143] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0144] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0145] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0146] Please see Figure 1 , Figure 1 A schematic diagram of the vehicle structure provided for an embodiment of this application.

[0147] See Figure 1 The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is installed inside the vehicle 1000, and the battery device 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0148] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0149] Please see Figure 2 , Figure 2 This is an exploded view of the battery device provided in an embodiment of this application.

[0150] See Figure 2 The battery device 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, collectively defining a space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the space. Alternatively, both the first portion 11 and the second portion 12 may be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0151] In the battery device 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel connections. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed configuration to form battery modules, and then these battery modules are connected in series, parallel, or in a mixed configuration to form a whole, which is also housed within the housing 10. The battery device 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0152] Among them, the battery cell 20 can be in the form of a cylinder, a flat shape, a cuboid, or other shapes.

[0153] Please see Figure 3 , Figure 3 This is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0154] See Figure 3 The battery cell 20 refers to the smallest unit that makes up the battery device 100. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0155] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 to output or input electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0156] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0157] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0158] The positive electrode includes a current collector and a positive electrode active layer disposed on the current collector. The positive electrode active layer includes a positive electrode active material, which may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNiO2). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 )}, lithium nickel cobalt aluminum oxides (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0159] In one embodiment, the positive electrode active layer further includes a positive electrode conductive agent and a positive electrode binder.

[0160] A positive electrode conductive agent imparts conductivity to the positive electrode. The positive electrode conductive agent can include any conductive material, as long as it does not cause a chemical change. Non-limiting examples of positive electrode conductive agents include carbon-based materials (e.g., natural graphite, conductive graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0161] Positive electrode binders improve the adhesion stability of the positive electrode active layer and reduce the probability of powder shedding. Positive electrode binders may include one or more of the following: styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0162] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer disposed on the negative current collector.

[0163] In some embodiments, the negative electrode active layer may further include a negative electrode binder, a negative electrode conductive agent, and other optional additives. For example, the negative electrode conductive agent may be one or more of superconducting carbon, carbon black {examples may include one or more of acetylene black, Ketjen black, and SuperP (SP)}, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. For example, the negative electrode binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). For example, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0164] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0165] In a first aspect, embodiments of this application provide a battery cell. The battery cell includes a first electrode. The first electrode includes a first current collector and a first film layer disposed on at least one surface of the first current collector. The first film layer comprises a first active material. The first active material includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon particles located within the pores of the porous carbon. The grain size of the silicon particles satisfies 2nm to 12nm. The grain size of the silicon particles can be 2nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm, 2.5nm, 2.6nm, 2.7nm, 2.8nm, 2.9nm, 3nm, 3.1nm, 3.2nm, 3.3nm, 3.4nm, 3.5nm, 3.6nm, 3.7nm, 3.8nm, 3.9nm, 4nm, 4.1nm, 4.2nm, 4.3nm, 4.4nm, 4.5nm, 4.6nm, 4.7nm, 4.8nm, etc. 4.9nm, 5nm, 5.1nm, 5.2nm, 5.3nm, 5.4nm, 5.5nm, 5.6nm, 5.7nm, 5.8nm, 5.9nm, 6nm, 6.1nm, 6.2nm, 6.3nm, 6.4 nm、6.5nm、6.6nm、6.7nm、6.8nm、6.9nm、7nm、7.1nm、7.2nm、7.3nm、7.4nm、7.5nm、7.6nm、7.7nm、7.8nm、7.9nm , 8nm, 8.1nm, 8.2nm, 8.3nm, 8.4nm, 8.5nm, 8.6nm, 8.7nm, 8.8nm, 8.9nm, 9nm, 9.1nm, 9.2nm, 9.3nm, 9.4nm, 9. 5nm, 9.6nm, 9.7nm, 9.8nm, 9.9nm, 10nm, 10.1nm, 10.2nm, 10.3nm, 10.4nm, 10.5nm, 10.6nm, 10.7nm, 10.8nm, 1 0.9nm, 11nm, 11.1nm, 11.2nm, 11.3nm, 11.4nm, 11.5nm, 11.6nm, 11.7nm, 11.8nm, 11.9nm, 12nm, etc., or any range of two of the above values, for example, 2nm~4nm, 3nm~5nm, 4nm~6nm, 5nm~7nm, 6nm~8nm, 7nm~9nm, 8nm~10nm, 9nm~11nm, 10nm~12nm, etc.

[0166] A battery cell, also known as a rechargeable battery or accumulator, is a device that converts electrical energy into chemical energy through an electrochemical reaction, stores it, and then releases the stored chemical energy back into electrical energy when needed. The first electrode is the component in the battery cell responsible for storing or releasing lithium ions, and is one of the core components for battery energy conversion and storage. The first current collector refers to the substrate in the first electrode used to attach the active material. The first current collector can be a metal foil or a composite current collector. Composite current collectors can be formed by forming metal or alloy materials on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The first film layer refers to the film layer formed on the first current collector. The first active material refers to the chemical substance that directly participates in the electrochemical reaction in the first electrode and can reversibly store and release electrical energy. The first film layer of the first electrode can be disposed on only one surface of the first current collector, or on two opposite surfaces of the first current collector. Porous carbon refers to carbon materials with a porous structure containing numerous micropores (pore size less than 2 nm), mesopores (pore size between 2 nm and 50 nm), or macropores (pore size greater than 50 nm). Silicon particles refer to silicon particles with sizes ranging from micrometers to nanometers and sub-nanometers.

[0167] The embodiments of this application provide a silicon-carbon composite material by improving the battery cell. This silicon-carbon composite material provides space for silicon particles through porous carbon to alleviate the volume expansion of silicon particles. By controlling the reaction time of the silicon-lithium alloy with silicon particles of 2nm to 12nm grain size, the excessive reaction of the silicon-carbon composite material during lithium intercalation is reduced, and the amount of irreversible byproducts of silicon-lithium is reduced. Due to the reasonable control of the reaction time of the silicon-lithium alloy, the large expansion stress on silicon particles in a short time is reduced, the electrode pulverization and shedding are reduced, and the integrity of silicon particles is improved. In addition, the reasonable control of the reaction time of the silicon-lithium alloy is also conducive to improving the lithium intercalation utilization rate of silicon particles and improving the first coulombic efficiency of the battery cell.

[0168] In some embodiments, with the first electrode as the positive electrode and the lithium metal sheet as the negative electrode, when discharged from 0.33C to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of silicon particles in the range of 0.4V to 0.5V.

[0169] Compared to silicon particles with a grain size of less than 2 nm, the silicon particles in this application have a larger grain size. During the lithium intercalation reaction of the battery cell, the lithium intercalation time of the silicon particles is longer, resulting in a more pronounced lithium intercalation plateau in the battery cell. The appearance of this plateau indicates a smoother lithium intercalation rate, which helps reduce lithium loss and thus contributes to a good initial coulombic efficiency. The lithium intercalation phase transition peak is an external manifestation of the lithium intercalation characteristics of silicon particles. A pronounced lithium intercalation plateau is reflected in the dQ / dV-V curve, indicating a significant lithium intercalation phase transition peak. Specifically, with the first electrode as the positive electrode and the lithium metal sheet as the negative electrode, when discharging from 0.33C to 0.8V, a dQ / dV-V curve showing a lithium intercalation phase transition peak in the range of 0.4V to 0.5V indicates that the corresponding battery cell has a good initial coulombic efficiency.

[0170] The embodiments of this application, by adjusting the grain size of silicon particles, enable a battery cell to discharge at 0.33C to 0.8V with the first electrode as the positive electrode and the lithium metal sheet as the negative electrode. The capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of silicon particles at the position of 0.4V to 0.5V. The battery cell using this electrode has good first coulombic efficiency.

[0171] In some embodiments, using the first electrode as the positive electrode and the lithium metal sheet as the negative electrode, when discharged from 0.33C to 0.8V, the dQ / dV-V curve exhibits a lithium intercalation phase transition peak of silicon particles in the range of 0.4V to 0.5V. The lithium-silicon alloy corresponding to this lithium intercalation phase transition peak of silicon particles is Li. 15 Si4.

[0172] In some embodiments, the peak value of the lithium intercalation phase change peak of the silicon particles satisfies 2 mAh / V to 12 mAh / V; the peak value of the lithium intercalation phase change peak of the silicon particles can be 2 mAh / V, 2.1 mAh / V, 2.2 mAh / V, 2.3 mAh / V, 2.4 mAh / V, 2.5 mAh / V, 2.6 mAh / V, 2.7 mAh / V, 2.8 mAh / V, 2.9 mAh / V, 3 mAh / V, 3.1 mAh / V, 3.2 mAh / V, 3.3 mAh / V, 3.4 mAh / V, 3.5 mAh / V, 3.6 mAh / V, 3.7 mAh / V, 3.8 mAh / V, 3.9 mAh / V, 4 mAh / V, 4.1 mAh / V, 4.2 mAh / V, 4.3 mAh / V, 4.4 mAh / V, 4.5 mAh / V, 4.6 mAh / V, 4.7 mAh / V, 4.8 mAh / V, 4.9 mAh / V, 5 mAh / V, 5.1 mAh / V, 5.2 mAh / V, 5.3 mAh / V, 5.4 mAh / V, 5.5 mAh / V, 5.6 mAh / V, 5.7 mAh / V, 5.8 mAh / V, 5.9 mAh / V, 6 mAh / V, 6.1 mAh / V, 6.2 mAh / V, 6.3 mAh / V, 6.4 mAh / V, 6.5 mAh / V, 6.6 mAh / V, 6.7 mAh / V, 6.8 mAh / V, 6.9 mAh / V, 7 mAh / V, 7.1 mAh / V, 7.2 mAh / V, 7.3 mAh / V, 7.4 mAh / V, 7.5 mAh / V, 7.6 mAh / V, 7.7 mAh / V, 7.8 mAh / V, 7.9 mAh / V, 8 mAh / V, 8.1 mAh / V, 8.2 mAh / V, 8.3 mAh / V, 8.4 mAh / V, 8.5 mAh / V, 8.6 mAh / V, 8.7 mAh / V, 8.8 mAh / V, 8.9 mAh / V, 9 mAh / V, 9.1 mAh / V, 9.2 mAh / V, 9.3 mAh / V, 9.4 mAh / V, 9.5 mAh / V, 9.6 mAh / V, 9.7 mAh / V, 9.8 mAh / V, 9.9 mAh / V, 10 mAh / V, 10.1 mAh / V, 10.2 mAh / V, 10.3 mAh / V, 10.4 mAh / V, 10.5 mAh / V, 10.6 mAh / V, 10.7 mAh / V, 10.8 mAh / V, 10.9 mAh / V, 11 mAh / V, 11.1 mAh / V, 11.2 mAh / V, 11.3 mAh / V, 11.4 mAh / V, 11.5 mAh / V, 11.6 mAh / V, 11.7 mAh / V, 11.8 mAh / V, 11.9mAh / V, 12mAh / V, etc., or any range of two of the above values, for example, 2mAh / V~4mAh / V, 3mAh / V~5mAh / V, 4mAh / V~6mAh / V, 5mAh / V~7mAh / V, 6mAh / V~8mAh / V, 7mAh / V~9mAh / V, 8mAh / V~10mAh / V, 9mAh / V~11mAh / V, 10mAh / V~12mAh / V, etc.

[0173] The peak value of the lithium intercalation phase transition peak of silicon particles refers to the dQ / dV value corresponding to the extreme value of the lithium intercalation phase transition peak, and its unit is mAh / V.

[0174] The embodiments of this application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles so that the battery cell using this electrode has good first coulombic efficiency.

[0175] In some embodiments, the first electrode further includes one or more of the following features:

[0176] (1) The areal density of the first film layer satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 The areal density of the first film layer can be 2.5 mg / cm³. 2 2.6 mg / cm 2 2.7 mg / cm 2 2.8 mg / cm 2 2.9 mg / cm 2 3mg / cm 2 3.1 mg / cm 2 3.2 mg / cm 2 3.3 mg / cm 2 3.4 mg / cm 2 3.5 mg / cm 2 3.6 mg / cm 2 3.7 mg / cm 2 3.8 mg / cm 2 3.9 mg / cm 2 4mg / cm 2 4.1 mg / cm 2 4.2 mg / cm 2 4.3 mg / cm 2 4.4 mg / cm 2 4.5 mg / cm 2 4.6 mg / cm 2 4.7 mg / cm 2 4.8 mg / cm 2 4.9 mg / cm2 5mg / cm 2 etc., or a range consisting of any two of the above values, for example, 2.5 mg / cm³. 2 ~3mg / cm 2 2.7 mg / cm 2 ~3.5mg / cm 2 3.3 mg / cm 2 ~4mg / cm 2 3.7 mg / cm 2 ~4.5mg / cm 2 4.1 mg / cm 2 ~5mg / cm 2 wait;

[0177] (2) The compaction density of the first membrane layer satisfies 1.3 g / cc to 1.7 g / cc; the compaction density of the first membrane layer can be 1.3 g / cc, 1.31 g / cc, 1.32 g / cc, 1.33 g / cc, 1.34 g / cc, 1.35 g / cc, 1.36 g / cc, 1.37 g / cc, 1.38 g / cc, 1.39 g / cc, 1.4 g / cc, 1.41 g / cc, 1.42 g / cc, 1.43 g / cc, 1.44 g / cc, 1.45 g / cc, 1.46 g / cc, 1.47 g / cc, 1.48 g / cc, 1.49 g / cc, 1.5 g / cc, 1.51 g / cc, 1.52 g / cc, 1.53 g / cc, 1.54 g / cc, 1.55 g / cc, 1 0.56g / cc, 1.57g / cc, 1.58g / cc, 1.59g / cc, 1.6g / cc, 1.61g / cc, 1.62g / cc, 1.63g / cc, 1.64g / cc, 1.65g / cc, 1.66g / cc, 1.67g / cc, 1.68g / cc, 1.69g / cc, 1.7g / cc, etc., or any range of two of the above values, for example, 1.3g / cc~1.4g / cc, 1.35g / cc~1.45g / cc, 1.4g / cc~1.5g / cc, 1.45g / cc~1.55g / cc, 1.5g / cc~1.6g / cc, 1.55g / cc~1.65g / cc, 1.6g / cc~1.7g / cc, etc.;

[0178] (3) The weight ratio of silicon-carbon composite material in the first film layer is 40% to 60%; the weight ratio of silicon-carbon composite material in the first film layer can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, etc., or a range of any two of the above values, for example, it can be 40% to 50%, 45% to 55%, 50% to 60%, etc.

[0179] (4) The first active material also includes graphite, and the weight percentage of graphite in the first film layer is 40% to 60%; the weight percentage of graphite in the first film layer can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, etc., or a range of any two of the above values, for example, it can be 40% to 50%, 45% to 55%, 50% to 60%, etc.;

[0180] (5) The first film layer also includes a first conductive agent, a first binder, and a thickener;

[0181] Optionally, the first conductive agent includes one or more of carbon black, carbon nanotubes, graphite, graphene and carbon nanofibers, and / or the first binder includes one or more of styrene-butadiene rubber, polyacrylic acid, lithium-ionized polyacrylic acid, and / or the thickener includes sodium carboxymethyl cellulose.

[0182] Optionally, the mass ratio of the first active material, the first conductive agent, the carbon nanotube, the first binder, and the thickener satisfies 94-95:1-1.5:2.5-3.5:1-1.5.

[0183] Wherein, the areal density of the first film layer represents the weight of the first film layer per unit area. The compaction density of the first film layer represents the weight of the first film layer per unit volume, which is equal to the areal density of the first film layer divided by the thickness of the first film layer. The weight ratio of silicon-carbon composite material in the first film layer represents the ratio of the weight of silicon-carbon composite material to the total weight of the first film layer. The first active material may also include graphite and the silicon-carbon composite material provided in this application. The capacity and / or initial coulombic efficiency of the battery cell can be adjusted by controlling the weight ratio of graphite and silicon-carbon composite material in the first active material. The first conductive agent is used to improve the conductivity of the first film layer and reduce the internal resistance of the first film layer. The first binder is used to help the components forming the first film layer to be better dispersed in the solvent, forming a uniform slurry to form a high-quality first film layer and to ensure good bonding between the first film layer and the first current collector. The thickener is used to improve the rheological properties of the slurry forming the first film layer to obtain a uniform and stable coating during the coating process.

[0184] The embodiments of this application achieve good initial coulombic efficiency in a single battery cell by adjusting various parameters of the first electrode.

[0185] In some embodiments, the battery cell further includes a second electrode, the second electrode including a second current collector and a second film layer disposed on at least one surface of the second current collector, the second film layer containing a second active material; the battery cell uses the second electrode as the positive electrode and the first electrode as the negative electrode;

[0186] The second electrode includes one or more of the following characteristics:

[0187] (1) The areal density of the second film layer satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 The areal density of the second film layer can be 2.5 mg / cm³. 2 2.6 mg / cm 2 2.7 mg / cm 2 2.8 mg / cm 2 2.9 mg / cm 2 3mg / cm 2 3.1 mg / cm 2 3.2 mg / cm 2 3.3 mg / cm 2 3.4 mg / cm 2 3.5 mg / cm 2 3.6 mg / cm 2 3.7 mg / cm 2 3.8 mg / cm 2 3.9 mg / cm 2 4mg / cm 24.1 mg / cm 2 4.2 mg / cm 2 4.3 mg / cm 2 4.4 mg / cm 2 4.5 mg / cm 2 4.6 mg / cm 2 4.7 mg / cm 2 4.8 mg / cm 2 4.9 mg / cm 2 5mg / cm 2 etc., or a range consisting of any two of the above values, for example, 2.5 mg / cm³. 2 ~3mg / cm 2 2.7 mg / cm 2 ~3.5mg / cm 2 3.3 mg / cm 2 ~4mg / cm 2 3.7 mg / cm 2 ~4.5mg / cm 2 4.1 mg / cm 2 ~5mg / cm 2 wait;

[0188] (2) The compaction density of the second membrane layer satisfies 1.3 g / cc to 1.6 g / cc; the compaction density of the second membrane layer can be 1.3 g / cc, 1.31 g / cc, 1.32 g / cc, 1.33 g / cc, 1.34 g / cc, 1.35 g / cc, 1.36 g / cc, 1.37 g / cc, 1.38 g / cc, 1.39 g / cc, 1.4 g / cc, 1.41 g / cc, 1.42 g / cc, 1.43 g / cc, 1.44 g / cc, 1.45 g / cc, 1.46 g / cc, 1.47 g / cc, 1.48 g / cc, 1 0.49g / cc, 1.5g / cc, 1.51g / cc, 1.52g / cc, 1.53g / cc, 1.54g / cc, 1.55g / cc, 1.56g / cc, 1.57g / cc, 1.58g / cc, 1.59g / cc, 1.6g / cc, etc., or any range of two of the above values, for example, 1.3g / cc~1.4g / cc, 1.35g / cc~1.45g / cc, 1.4g / cc~1.5g / cc, 1.45g / cc~1.55g / cc, 1.5g / cc~1.6g / cc, etc.;

[0189] (3) The second active material includes one or more of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese iron phosphate, and their respective modified compounds.

[0190] (4) The second electrode also includes a second conductive agent and a second binder;

[0191] Optionally, the second conductive agent includes carbon black, and / or the second binder includes polyvinylidene fluoride;

[0192] Optionally, the mass ratio of the second active material, the second conductive agent, and the second binder satisfies 96–98:0.5–1.5:1–3;

[0193] The battery cell also includes the following features:

[0194] The energy density of the battery cells ranges from 380Wh / kg to 500Wh / kg. The energy densities of the battery cells can be 380Wh / kg, 381Wh / kg, 382Wh / kg, 383Wh / kg, 384Wh / kg, 385Wh / kg, 386Wh / kg, 387Wh / kg, 388Wh / kg, 389Wh / kg, 390Wh / kg, 391Wh / kg, 392Wh / kg, 393Wh / kg, 394Wh / kg, 395Wh / kg, 396Wh / kg, 397Wh / kg, 398Wh / kg, 399Wh / kg, 400Wh / kg, 401Wh / kg, 402Wh / kg, and 403Wh / kg. kg, 404Wh / kg, 405Wh / kg, 406Wh / kg, 407Wh / kg, 408Wh / kg, 409Wh / kg, 410Wh / kg, 411Wh / kg, 412Wh / kg, 413Wh / kg, 414Wh / kg, 415Wh / kg, 416 Wh / kg, 417Wh / kg, 418Wh / kg, 419Wh / kg, 420Wh / kg, 421Wh / kg, 422Wh / kg, 423Wh / kg, 424Wh / kg, 425Wh / kg, 426Wh / kg, 427Wh / kg, 428Wh / kg, 429Wh / kg, 430Wh / kg, 431Wh / kg, 432Wh / kg, 433Wh / kg, 434Wh / kg, 435Wh / kg, 436Wh / kg, 437Wh / kg, 438Wh / kg, 439Wh / kg, 440Wh / kg, 441Wh / kg, 442Wh / kg, 443Wh / kg, 444Wh / kg, 445Wh / kg, 446Wh / kg, 447Wh / kg, 448Wh / kg, 449Wh / kg, 450Wh / kg, etc., or a range of any two of the above values, for example, 380Wh / kg. g~390Wh / kg, 385Wh / kg~395Wh / kg, 390Wh / kg~400Wh / kg, 395Wh / kg~405Wh / kg, 400Wh / kg~410Wh / kg, 405Wh / kg~415Wh / kg, 410Wh / kg~420W h / kg, 415Wh / kg~425Wh / kg, 420Wh / kg~430Wh / kg, 425Wh / kg~435Wh / kg, 430Wh / kg~440Wh / kg, 435Wh / kg~445Wh / kg, 440Wh / kg~450Wh / kg, etc.

[0195] In a battery cell, the positive and negative electrode materials interact through ions (such as lithium ions) in the electrolyte, achieving the mutual conversion of electrical energy and chemical energy during charging and discharging. The second electrode is the component in the battery cell responsible for storing or releasing lithium ions, and is one of the core components for electrical energy conversion and storage. The second current collector refers to the substrate in the second electrode used to attach the active material. The second current collector can be a metal foil or a composite current collector. Composite current collectors can be formed by forming metal or alloy materials on a polymer substrate (such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE, etc.). The second film layer refers to the film layer formed on the second current collector. The second active material refers to the chemical substance that directly participates in the electrochemical reaction in the second electrode, capable of reversibly storing and releasing electrical energy. The second film layer of the second electrode can be disposed on only one surface of the second current collector, or on two opposite surfaces of the second current collector. The second conductive agent is used to improve the conductivity of the second film layer and reduce its internal resistance. The second binder helps the components forming the second film layer to disperse better in the solvent, forming a uniform slurry to create a high-quality second film layer and ensure good bonding between the second film layer and the second current collector. The mass energy density of a battery cell refers to the total energy stored per unit mass of battery cell. It is an important indicator for evaluating the energy storage efficiency of a battery cell, directly affecting its weight, volume, and range. Its unit is typically watt-hours per kilogram (Wh / kg).

[0196] The embodiments of this application achieve good initial coulombic efficiency in a single battery cell by adjusting various parameters of the second electrode.

[0197] In some embodiments, the battery cell includes an electrolyte; the electrolyte includes an electrolyte salt and a solvent; or, the electrolyte includes an electrolyte salt, a solvent, and additives.

[0198] The electrolyte salt may be selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0199] Solvents include one or more of carbonate solvents and ether solvents.

[0200] Carbonate solvents are typically small-molecule cyclic or chain carbonates; including but not limited to one or more of ethylene carbonate, propylene carbonate, butene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluorocarbonate, and fluoroethylene carbonate; they can also be one or more ester solvents selected from γ-butyrolactone, dimethyl sulfite, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl acetate, and fluorocarboxylic acid esters.

[0201] Ether solvents include, but are not limited to, one or more of dimethyl ether, diethyl ether, tetrahydrofuran, methyltetrahydrofuran, ethylene oxide, 1,3-dioxolane, fluoroethers, DME (ethylene glycol dimethyl ether), DEE (ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), TRGDME (triethylene glycol dimethyl ether), TEGDME (tetraethylene glycol dimethyl ether), dipropyl ether, and dibutyl ether.

[0202] In other embodiments, the electrolyte may further include one or more of amine solvents, sulfone solvents, and nitrile solvents. In some embodiments, the amine solvent includes one or more of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide. The sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, diphenyl sulfoxide, thionyl chloride, and dipropyl sulfone. The nitrile solvent includes one or more of acetonitrile, butadiene nitrile, adiponitrile, and glutaronitrile. The electrolyte is preferably a high-voltage resistant electrolyte, which exhibits weak acidity at high voltages, facilitating the transport of active ions, reducing side reactions on the electrode surface, and improving the stability of the battery cell.

[0203] Additives may include one or two of negative electrode film-forming additives and positive electrode film-forming additives, and may also include additives that can improve certain properties of battery cells, such as one or two of additives that improve the overcharge performance of battery cells and additives that improve the high temperature or low temperature performance of battery cells.

[0204] The embodiments of this application achieve good initial coulombic efficiency in battery cells by controlling the electrolyte in the battery cells, including the first electrode and the second electrode. In some embodiments, the silicon-carbon composite material includes one or more of the following characteristics:

[0205] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%; the weight percentage of silicon in silicon-carbon composite materials can be 45wt%, 45.2wt%, 45.4wt%, 45.6wt%, 45.8wt%, 46wt%, 46.2wt%, 46.4wt%, 46.6wt%, 46.8wt%, 47wt%, 47.2wt%, 47.4wt%, 47.6wt%, 47.8wt%, 48wt%, 48.2wt%, 48.4wt%, 48.6wt%, 48.8wt%, 4 9wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6w t%, 51.8wt%, 52wt%, 52.2wt%, 52.4wt%, 52.6wt%, 52.8wt%, 53wt%, 53.2wt%, 53.4wt%, 53.6wt%, 53.8wt%, 54wt%, 54.2wt%, 54 .4wt%, 54.6wt%, 54.8wt%, 55wt%, 55.2wt%, 55.4wt%, 55.6wt%, 55.8wt%, 56wt%, 56.2wt%, 56.4wt%, 56.6wt%, 56.8wt%, 57wt %, 57.2wt%, 57.4wt%, 57.6wt%, 57.8wt%, 58wt%, 58.2wt%, 58.4wt%, 58.6wt%, 58.8wt%, 59wt%, 59.2wt%, 59.4wt%, 59.6wt%, 5 9.8wt%, 60wt%, etc., or any range of two of the above values, for example, 45wt%~47wt%, 46wt%~48wt%, 47wt%~49wt%, 48wt%~50wt%, 49wt%~51wt%, 50wt%~52wt%, 51wt%~53wt%, 52wt%~54wt%, 53wt%~55wt%, 54wt%~56wt%, 55wt%~57wt%, 56wt%~58wt%, 57wt%~59wt%, 58wt%~60wt%, etc.

[0206] In silicon-carbon composite materials, the weight percentage of silicon is determined according to EPA 6010D-2014 standard. Specifically, ICP-OES (Inductively Coupled Plasma Emission Spectrometry) can be used for testing. First, the sample to be tested is dissolved into a liquid with a strong acid. Then, the liquid is introduced into the ICP light source by atomization. The gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then recover from the excited state to the ground state. During the above process, energy is released and recorded as different characteristic spectral lines for elemental quantitative analysis.

[0207] (2) The silicon-carbon composite material further includes a carbon coating layer, which coats the surface of porous carbon to improve the conductivity of the first active material and mitigate the negative effects of volume expansion of silicon particles. In some embodiments, the surface of the silicon particles includes oxygen to passivate the reactivity of the silicon particles and mitigate the negative effects of volume expansion of silicon particles.

[0208] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0209] In some embodiments, porous carbon includes one or more of the following features:

[0210] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm; the volume average particle size Dv50 of porous carbon can be 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7 ... .6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9μm, 9.1μm, 9.2μm, 9 .3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, 10.1μm, 10.2μm, 10.3μm, 10.4μm, 10.5μm, 10.6μm, 10.7μm, 10.8 μm, 10.9μm, 11μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm, 12μm, 12.1μm, 12.2μm, 1 2.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7μm, 12.8μm, 12.9μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13. 7μm, 13.8μm, 13.9μm, 14μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15μm, etc., or any range of two of the above values, for example, 5μm~7μm, 6μm~8μm, 7μm~9μm, 8μm~10μm, 9μm~11μm, 10μm~12μm, 11μm~13μm, 12μm~14μm, 13μm~15μm, etc.

[0211] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g; the specific surface area of ​​porous carbon can be 1000m². 2 / g, 1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g, 1350m 2 / g, 1400m 2 / g, 1450m 2 / g, 1500m 2 / g, 1550m 2 / g, 1600m 2 / g、1650m 2 / g, 1700m 2 / g、1750m 2 / g、1800m 2 / g、1850m 2 / g、1900m 2 / g、1950m 2 / g、2000m 2 / g, or a range consisting of any two of the above values, for example, 1000m. 2 / g~1200m 2 / g、1100m 2 / g~1300m 2 / g、1200m 2 / g~1400m 2 / g、1300m 2 / g~1500m 2 / g, 1400m 2 / g~1600m 2 / g, 1500m 2 / g~1700m 2 / g, 1600m 2 / g~1800m 2 / g, 1700m 2 / g~1900m 2 / g、1800m 2 / g~2000m 2 / g etc.

[0212] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; the pore volume of porous carbon can be 0.6cm³. 3 / g, 0.65cm 3 / g, 0.7cm 3 / g, 0.75cm 3 / g, 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 0.95cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.1cm 3 / g, or a range consisting of any two of the above values, for example, 0.6cm. 3 / g~0.7cm 3 / g, 0.65cm 3 / g~0.75cm 3 / g, 0.7cm 3 / g~0.8cm 3 / g, 0.75cm 3 / g~0.85cm 3 / g, 0.8cm 3 / g~0.9cm 3 / g, 0.85cm 3 / g~0.95cm 3 / g, 0.9cm 3 / g~1cm 3 / g, 0.95cm 3 / g~1.05cm 3 / g, 1cm 3 / g~1.1cm 3 / g etc.

[0213] (4) In the pores of porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%; the proportion of pores with a diameter of 2 nm to 10 nm can be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90 ... 0.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, etc., or any range of two of the above values, such as 80%–82%, 81%–83%, 82%–84%, 83%–85%, 84%–86%, 85%–87%, 86%–88%, 87%–89%, 88%–90%, 89%–91%, 90%–92%, 91%–93%, 92%–94%, etc.

[0214] (5) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is between 0.1% and 6%; the proportion of pores with a diameter greater than or equal to 50 nm can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%. %, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, etc., or a range consisting of any two of the above values, for example, 0.1%–0.5%, 0.3%–0.7%, 0.5%–1%, 0.7%–1.3%, 1%–1.5%, 1.3%–1.7%, 1.5%–2%, 1.7%–2.3%, 2%–2.5%, 2.2%–2.7%, 2.5%–3%, 3%–5%, 4%–6%, etc.

[0215] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0216] Secondly, embodiments of this application provide a silicon-carbon composite material, which includes porous carbon and silicon particles located within the pores of the porous carbon; the grain size of the silicon particles satisfies 2nm to 12nm.

[0217] The embodiments of this application provide a silicon-carbon composite material, which provides a space for silicon particles through porous carbon to alleviate the volume expansion of silicon particles; by controlling the reaction time of silicon-lithium alloy by silicon particles with a grain size of 2nm to 12nm, the lithium intercalation utilization rate of silicon particles is improved, the expansion stress of silicon particles is reduced, and the integrity of silicon particles is improved, thereby improving the first coulombic efficiency of battery cells.

[0218] In some embodiments, when an electrode comprising silicon-carbon composite material is used as the positive electrode and a lithium metal sheet is used as the negative electrode, and the discharge is carried out at 0.1C to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of silicon particles in the range of 0.4V to 0.5V.

[0219] The embodiments of this application, by controlling the grain size of silicon particles, enable the use of an electrode comprising silicon-carbon composite material as the positive electrode and a lithium metal sheet as the negative electrode, to discharge from 0.33C to 0.8V. The capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of silicon particles at the position of 0.4V to 0.5V. The battery cell using this electrode has good first coulombic efficiency.

[0220] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2 mAh / V to 12 mAh / V.

[0221] The embodiments of this application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles so that the battery cell using this electrode has good first coulombic efficiency.

[0222] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0223] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%; the weight percentage of silicon in silicon-carbon composite materials can be 45wt%, 45.2wt%, 45.4wt%, 45.6wt%, 45.8wt%, 46wt%, 46.2wt%, 46.4wt%, 46.6wt%, 46.8wt%, 47wt%, 47.2wt%, 47.4wt%, 47.6wt%, 47.8wt%, 48wt%, 48.2wt%, 48.4wt%, 48.6wt%, 48.8wt%, 4 9wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6w t%, 51.8wt%, 52wt%, 52.2wt%, 52.4wt%, 52.6wt%, 52.8wt%, 53wt%, 53.2wt%, 53.4wt%, 53.6wt%, 53.8wt%, 54wt%, 54.2wt%, 54 .4wt%, 54.6wt%, 54.8wt%, 55wt%, 55.2wt%, 55.4wt%, 55.6wt%, 55.8wt%, 56wt%, 56.2wt%, 56.4wt%, 56.6wt%, 56.8wt%, 57wt %, 57.2wt%, 57.4wt%, 57.6wt%, 57.8wt%, 58wt%, 58.2wt%, 58.4wt%, 58.6wt%, 58.8wt%, 59wt%, 59.2wt%, 59.4wt%, 59.6wt%, 5 9.8wt%, 60wt%, etc., or any range of two of the above values, for example, 45wt%~47wt%, 46wt%~48wt%, 47wt%~49wt%, 48wt%~50wt%, 49wt%~51wt%, 50wt%~52wt%, 51wt%~53wt%, 52wt%~54wt%, 53wt%~55wt%, 54wt%~56wt%, 55wt%~57wt%, 56wt%~58wt%, 57wt%~59wt%, 58wt%~60wt%, etc.

[0224] (2) The silicon-carbon composite material also includes a carbon coating layer, which coats the surface of porous carbon to improve the conductivity of the first active material and the negative impact of the volume expansion of silicon particles.

[0225] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0226] In some embodiments, porous carbon includes one or more of the following features:

[0227] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm; the volume average particle size Dv50 of porous carbon can be 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7 ... .6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9μm, 9.1μm, 9.2μm, 9 .3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, 10.1μm, 10.2μm, 10.3μm, 10.4μm, 10.5μm, 10.6μm, 10.7μm, 10.8 μm, 10.9μm, 11μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm, 12μm, 12.1μm, 12.2μm, 1 2.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7μm, 12.8μm, 12.9μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13. 7μm, 13.8μm, 13.9μm, 14μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15μm, etc., or any range of two of the above values, for example, 5μm~7μm, 6μm~8μm, 7μm~9μm, 8μm~10μm, 9μm~11μm, 10μm~12μm, 11μm~13μm, 12μm~14μm, 13μm~15μm, etc.

[0228] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g; the specific surface area of ​​porous carbon can be 1000m². 2 / g, 1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g, 1350m 2 / g, 1400m 2 / g, 1450m 2 / g, 1500m 2 / g, 1550m 2 / g, 1600m 2 / g、1650m 2 / g, 1700m 2 / g、1750m 2 / g、1800m 2 / g、1850m 2 / g、1900m 2 / g、1950m 2 / g、2000m 2 / g, or a range consisting of any two of the above values, for example, 1000m. 2 / g~1200m 2 / g、1100m 2 / g~1300m 2 / g、1200m 2 / g~1400m 2 / g、1300m 2 / g~1500m 2 / g, 1400m 2 / g~1600m 2 / g, 1500m 2 / g~1700m 2 / g, 1600m 2 / g~1800m 2 / g, 1700m 2 / g~1900m 2 / g、1800m 2 / g~2000m 2 / g etc.

[0229] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; the pore volume of porous carbon can be 0.6cm³. 3 / g, 0.65cm 3 / g, 0.7cm 3 / g, 0.75cm 3 / g, 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 0.95cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.1cm 3 / g, or a range consisting of any two of the above values, for example, 0.6cm. 3 / g~0.7cm 3 / g, 0.65cm 3 / g~0.75cm 3 / g, 0.7cm 3 / g~0.8cm 3 / g, 0.75cm 3 / g~0.85cm 3 / g, 0.8cm 3 / g~0.9cm 3 / g, 0.85cm 3 / g~0.95cm 3 / g, 0.9cm 3 / g~1cm 3 / g, 0.95cm 3 / g~1.05cm 3 / g, 1cm 3 / g~1.1cm 3 / g etc.

[0230] (4) In the pores of porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%; the proportion of pores with a diameter of 2 nm to 10 nm can be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90 ... 0.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, etc., or any range of two of the above values, such as 80%–82%, 81%–83%, 82%–84%, 83%–85%, 84%–86%, 85%–87%, 86%–88%, 87%–89%, 88%–90%, 89%–91%, 90%–92%, 91%–93%, 92%–94%, etc.

[0231] (5) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is between 0.1% and 6%; the proportion of pores with a diameter greater than or equal to 50 nm can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%. %, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, etc., or a range consisting of any two of the above values, for example, 0.1%–0.5%, 0.3%–0.7%, 0.5%–1%, 0.7%–1.3%, 1%–1.5%, 1.3%–1.7%, 1.5%–2%, 1.7%–2.3%, 2%–2.5%, 2.2%–2.7%, 2.5%–3%, 3%–5%, 4%–6%, etc.

[0232] The embodiments of this application achieve good first-run coulombic efficiency in battery cells, including silicon-carbon composite materials, by adjusting various parameters of porous carbon.

[0233] Thirdly, embodiments of this application provide a method for preparing a silicon-carbon composite material, comprising the following steps:

[0234] Porous carbon is provided, which has several pores;

[0235] Silicon particles are deposited into the pores of porous carbon, with the grain size of the silicon particles ranging from 2 nm to 12 nm, to form a silicon-carbon composite material.

[0236] The embodiments of this application provide a method for preparing a silicon-carbon composite material. The silicon-carbon composite material prepared by this method helps to alleviate the volume expansion of silicon particles, improve the lithium intercalation utilization of silicon particles, reduce the expansion stress of silicon particles, and improve the integrity of silicon particles, thereby improving the first coulombic efficiency of the battery cell containing the silicon-carbon composite material.

[0237] In some embodiments, the proportion of pores with a diameter of 2 nm to 10 nm in the porous carbon pores is 80% to 94%. The proportion of pores with a diameter of 2 nm to 10 nm can be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 9... 2.5%, 93%, 93.5%, 94%, etc., or any range of two of the above values, such as 80%–82%, 81%–83%, 82%–84%, 83%–85%, 84%–86%, 85%–87%, 86%–88%, 87%–89%, 88%–90%, 89%–91%, 90%–92%, 91%–93%, 92%–94%, etc.

[0238] The embodiments of this application achieve good first-run coulombic efficiency in battery cells, including silicon-carbon composite materials, by controlling the pore size of porous carbon.

[0239] In some embodiments, prior to the step of providing porous carbon, a step of preparing porous carbon is further included, comprising:

[0240] An organic carbon source is placed in an inert atmosphere and treated at a first temperature for a first duration to obtain a first intermediate.

[0241] The first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more to obtain the second intermediate.

[0242] The second intermediate was placed in a reducing atmosphere, and then treated at a third temperature for a third duration under a reducing gas flow atmosphere. This process was repeated several times to obtain porous carbon.

[0243] In this context, the organic carbon source refers to a carbon-containing organic compound. The organic carbon source is placed in an inert atmosphere to minimize the influence of the reaction environment on the products. The activating gas flow is a specially introduced gas flow with a specific function, designed to promote the formation and growth of pores in the organic carbon source. The first temperature provides the energy for the formation and growth of pores in the organic carbon source, while the first time interval controls the pore size and number. The first intermediate refers to the initial product generated by the pore-forming process of the organic carbon source. It should be noted that the surface of the first intermediate may contain several oxygen-containing acidic groups. The reducing atmosphere provides an environment conducive to the reduction reaction, allowing the oxygen-containing acidic groups on the surface of the first intermediate to be reduced, thereby reducing lithium consumption of the porous carbon and improving the initial coulombic efficiency of the battery cell. The second temperature provides the energy for the reduction reaction, and the second time interval controls the degree of reduction. Repeating the process several times refers to repeating the process of treating the first intermediate at the second temperature for the second duration under a reducing gas flow atmosphere once or several times to reduce surface defects in the porous carbon, reduce lithium consumption of the porous carbon, and improve the initial coulombic efficiency of the battery cell.

[0244] The embodiments of this application provide a method for preparing porous carbon in silicon-carbon composite materials. The porous carbon prepared by this method has good surface properties, reduced lithium-consuming groups on the surface of the porous carbon, and the battery cell containing the silicon-carbon composite material has good first coulombic efficiency.

[0245] In some embodiments, placing the organic carbon source in an inert atmosphere and treating it at a first temperature for a first duration includes one or more of the following features:

[0246] (1) Organic carbon sources include polymeric organic carbon sources;

[0247] (2) Polymer organic carbon sources include phenolic resins;

[0248] (3) The first temperature satisfies 880℃~1000℃; the first temperature can be 880℃, 885℃, 890℃, 895℃, 900℃, 905℃, 910℃, 915℃, 920℃, 925℃, 930℃, 935℃, 940℃, 945℃, 950℃, 955℃, 960℃, 965℃, 970℃, 975℃, 980℃, 985℃, 990℃, 995℃, 1000℃, etc., or a range consisting of any two of the above values, for example, it can be 880℃~890℃, 885℃~895℃, 890℃~900℃, etc. Temperatures range from 895℃ to 905℃, 900℃ to 910℃, 905℃ to 915℃, 910℃ to 920℃, 915℃ to 925℃, 920℃ to 930℃, 925℃ to 935℃, 930℃ to 940℃, 935℃ to 945℃, 940℃ to 950℃, 945℃ to 955℃, 950℃ to 960℃, 955℃ to 965℃, 960℃ to 970℃, 965℃ to 975℃, 970℃ to 980℃, 975℃ to 985℃, 980℃ to 990℃, 985℃ to 995℃, 990℃ to 1000℃, etc.

[0249] (4) The first duration satisfies 4h to 8h. The first duration can be 4h, 4.25h, 4.5h, 4.75h, 5h, 5.25h, 5.5h, 5.75h, 6h, 6.25h, 6.5h, 6.75h, 7h, 7.25h, 7.5h, 7.75h, 8h, etc., or a range consisting of any two of the above values. For example, it can be 4h to 5h, 4.5h to 5.5h, 5h to 6h, 5.5h to 6.5h, 6h to 7h, 6.5h to 7.5h, 7h to 8h, etc.

[0250] Among them, polymeric organic carbon sources refer to organic polymeric carbon sources. Phenolic resin is a synthetic resin produced by the condensation reaction of phenolic compounds (such as phenol) and aldehyde compounds (mainly formaldehyde) under the action of a catalyst.

[0251] The embodiments of this application provide a method for activating porous carbon in silicon-carbon composite materials. The first intermediate prepared by this method has fewer defects and fewer lithium-consuming groups on its surface, thereby reducing the lithium consumption of the first intermediate. The battery cell containing this silicon-carbon composite material has good first coulombic efficiency.

[0252] In some embodiments, the first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more, including one or more of the following features:

[0253] (1) The activation gas flow rate satisfies 0.1 L / min to 0.5 L / min; the activation gas flow rate can be 0.1 L / min, 0.11 L / min, 0.12 L / min, 0.13 L / min, 0.14 L / min, 0.15 L / min, 0.16 L / min, 0.17 L / min, 0.18 L / min, 0.19 L / min, 0.2 L / min, 0.21 L / min, 0.22 L / min, 0.23 L / min, 0.24 L / min, 0.25 L / min, 0.26 L / min, 0.27 L / min, 0.28 L / min, 0.29 L / min, 0.3 L / min, 0.31 L / min, 0.32 L / min, 0.33 L / min, 0.34 L / min, 0.35 L / min, 0.3 6L / min, 0.37L / min, 0.38L / min, 0.39L / min, 0.4L / min, 0.41L / min, 0.42L / min, 0.43L / min, 0.44L / min, 0.45L / min, 0.46L / min, 0.47L / min, 0.48L / min, 0.49L / min, 0.5L / min, etc., or any range of two of the above values, for example, 0.1L / min~0.2L / min, 0.15L / min~0.25L / min, 0.2L / min~0.3L / min, 0.25L / min~0.35L / min, 0.3L / min~0.4L / min, 0.35L / min~0.45L / min, 0.4L / min~0.5L / min, etc.;

[0254] (2) The activated airflow includes water vapor airflow;

[0255] (3) The first intermediate material is within a pressure range of 5 MPa to 30 MPa; the pressure of the first intermediate material can be 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa, 25 MPa, 26 MPa, 27 MPa, 28 MPa, 29 MPa, 30 MPa, etc., or a range consisting of any two of the above values, for example, it can be 5 MPa to 7 MPa, 6 MPa to 8 MPa, 7 MPa to 9 MPa, 8 MPa to 30 MPa, etc. 10MPa, 9MPa~11MPa, 10MPa~12MPa, 11MPa~13MPa, 12MPa~14MPa, 13MPa~15MPa, 14MPa~16MPa, 15MPa~17MPa, 16MPa~18MPa, 17MPa~19MPa, 18MPa~20MPa, 19MPa~21MPa, 20MPa~22MPa, 21MPa~23MPa, 22MPa~24MPa, 23MPa~25MPa, 24MPa~26MPa, 25MPa~27MPa, 26MPa~28MPa, 27MPa~29MPa, 28MPa~30MPa, etc.;

[0256] (4) The second temperature satisfies 600℃~700℃; the second temperature can be 600℃, 605℃, 610℃, 615℃, 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, 685℃, 690℃, 695℃, 700℃, etc., or a range consisting of any two of the above values, for example, it can be 600℃~610℃, 605℃~615℃, etc. Temperatures range from 610℃ to 620℃, 615℃ to 625℃, 620℃ to 630℃, 625℃ to 635℃, 630℃ to 640℃, 635℃ to 645℃, 640℃ to 650℃, 645℃ to 655℃, 650℃ to 660℃, 655℃ to 665℃, 660℃ to 670℃, 665℃ to 675℃, 670℃ to 680℃, 675℃ to 685℃, 680℃ to 690℃, 685℃ to 695℃, 690℃ to 700℃, etc.

[0257] (5) The second duration must be between 6h and 16h. The second duration can be 6h, 6.25h, 6.5h, 6.75h, 7h, 7.25h, 7.5h, 7.75h, 8h, 8.25h, 8.5h, 8.75h, 9h, 9.25h, 9.5h, 9.75h, 10h, 10.25h, 10.5h, 10.75h, 11h, 11.25h, 11.5h, 11.75h, 12h, 12.25h, 12.5h, 12.75h, 13h, 13.25h, 13.5h, 13.75h, 14h, 14.25h, 14.5h, 14.75h, 15h, 15.25h. h, 15.5h, 15.75h, 16h, etc., or any range consisting of any two of the above values, for example, 6h~7h, 6.5h~7.5h, 7h~8h, 7.5h~8.5h, 8h~9h, 8.5h~9.5h, 9h~10h, 9.5h~10.5h, 10h~11h, 10.5h~11.5h, 11h~12h, 11.5h~12.5h, 12h~13h, 12.5h~13.5h, 13h~14h, 13.5h~14.5h, 14h~15h, 14.5h~15.5h, 15h~16h, etc.

[0258] (6) The number of treatments is any one of 1 to 6.

[0259] The embodiments of this application provide a method for creating porous carbon in silicon-carbon composite materials. The porous carbon prepared by this method has fewer defects and fewer lithium-consuming groups on its surface, thereby reducing the amount of lithium consumed by the porous carbon. In addition, the method can regulate the pore size of the porous carbon so that the pores can have space to accommodate the growth of silicon particles. The battery cell containing this silicon-carbon composite material has good first coulombic efficiency.

[0260] In some embodiments, placing the second intermediate in a reducing atmosphere and treating the second intermediate at a third temperature for a third duration under a reducing gas flow atmosphere includes one or more of the following features:

[0261] (1) Reducing atmospheres include hydrogen;

[0262] (2) The flow rate of the reducing gaseous stream is 0.1 L / min to 0.5 L / min; the flow rate of the reducing gaseous stream can be 0.1 L / min, 0.11 L / min, 0.12 L / min, 0.13 L / min, 0.14 L / min, 0.15 L / min, 0.16 L / min, 0.17 L / min, 0.18 L / min, 0.19 L / min, 0.2 L / min, 0.21 L / min, 0.22 L / min, 0.23 L / min, 0.24 L / min, 0.25 L / min, 0.26 L / min, 0.27 L / min, 0.28 L / min, 0.29 L / min, 0.3 L / min, 0.31 L / min, 0.32 L / min, 0.33 L / min, 0.34 L / min, 0.35 L / min, 0. 36L / min, 0.37L / min, 0.38L / min, 0.39L / min, 0.4L / min, 0.41L / min, 0.42L / min, 0.43L / min, 0.44L / min, 0.45L / min, 0.46L / min, 0.47L / min, 0.48L / min, 0.49L / min, 0.5L / min, etc., or any range of two of the above values, for example, 0.1L / min~0.2L / min, 0.15L / min~0.25L / min, 0.2L / min~0.3L / min, 0.25L / min~0.35L / min, 0.3L / min~0.4L / min, 0.35L / min~0.45L / min, 0.4L / min~0.5L / min, etc.;

[0263] (3) The third temperature satisfies 450℃~600℃; the third temperature can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, etc., or a range composed of any two of the above values, for example, it can be 450℃~550℃, 500℃~600℃, etc.

[0264] (4) The third duration is 2h to 4h. The third duration can be 2h, 2.25h, 2.5h, 2.75h, 3h, 3.25h, 3.5h, 3.75h, 4h, etc., or a range of any two of the above values, for example, it can be 2h to 3h, 2.5h to 3.5h, 3h to 4h, etc.

[0265] The embodiments of this application provide a method for reducing porous carbon in silicon-carbon composite materials, further reducing the lithium-consuming groups on the surface of porous carbon to reduce the lithium consumption of porous carbon, and the battery cell containing the silicon-carbon composite material has good first coulombic efficiency.

[0266] In some embodiments, the step of depositing silicon particles into the pores of porous carbon includes:

[0267] Porous carbon is placed in an inert atmosphere, and silicon source gas is introduced to perform vapor phase deposition so that silicon particles are located within the pores of the porous carbon.

[0268] In this process, silicon source gas is a gaseous compound that serves as the source of silicon in the vapor deposition process. During vapor deposition, the silicon source decomposes to form silicon particles, which are then deposited within the pores of porous carbon.

[0269] The embodiments of this application provide a method for preparing silicon particles in silicon-carbon composite materials. The silicon particles prepared by this method have a large grain size, which allows for control of the reaction time of the silicon-lithium alloy, improves the lithium intercalation utilization rate of the silicon particles, reduces the expansion stress of the silicon particles, and improves the integrity of the silicon particles, thereby improving the first coulombic efficiency of the battery cell.

[0270] In some embodiments, the step of introducing a silicon source gas to perform vapor deposition includes one or more of the following features:

[0271] (1) The silicon source gas includes one or more of the following: silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane;

[0272] (2) The flow rate of the silicon source gas meets the requirement of 0.5L / min to 5L / min; the flow rate of the silicon source gas can be 0.5L / min, 0.6L / min, 0.7L / min, 0.8L / min, 0.9L / min, 1L / min, 1.1L / min, 1.2L / min, 1.3L / min, 1.4L / min, 1.5L / min, 1.6L / min, 1.7L / min, 1.8L / min, 1.9L / min, 2L / min, 2.1L / min, 2.2L / min, 2.3L / min, 2.4L / min, 2.5L / min, 2.6L / min, 2.7L / min, 2.8L / min, 2.9L / min, 3L / min, 3.1L / min, 3.2L / min, 3.3L / min, 3.4L / min. / min, 3.5L / min, 3.6L / min, 3.7L / min, 3.8L / min, 3.9L / min, 4L / min, 4.1L / min, 4.2L / min, 4.3L / min, 4.4L / min, 4.5L / min, 4.6L / min, 4.7L / min, 4.8L / min, 4.9L / min, 5L / min, etc., or any range of any two of the above values, for example, 0.5L / min~1.5L / min, 1L / min~2L / min, 1.5L / min~2.5L / min, 2L / min~3L / min, 2.5L / min~3.5L / min, 3L / min~4L / min, 3.5L / min~4.5L / min, 4L / min~5L / min, etc.;

[0273] (3) The deposition temperature of vapor deposition satisfies 480℃~600℃; the deposition temperature of vapor deposition can be 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, etc., or any range of any two of the above values, for example, it can be 480℃~530℃, 500℃~550℃, 520℃~570℃, 550℃~600℃, etc.

[0274] (4) The deposition time of the vapor phase deposition meets the requirement of 6h to 24h. The deposition time of the vapor phase deposition can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc., or a range of any two of the above values. For example, it can be 6h to 8h, 7h to 9h, 8h to 10h, 9h to 11h, 10h to 12h, 11h to 13h, 12h to 14h, 13h to 15h, 14h to 16h, 15h to 17h, 16h to 18h, 17h to 19h, 18h to 20h, 19h to 21h, 20h to 22h, 21h to 23h, 22h to 24h, etc.

[0275] The embodiments of this application provide process parameters for preparing silicon particles in silicon-carbon composite materials. This method can control the grain size of the prepared silicon particles, thereby controlling the reaction time of the silicon-lithium alloy, improving the lithium intercalation utilization rate of the silicon particles, reducing the expansion stress of the silicon particles, and improving the integrity of the silicon particles, so as to improve the first coulombic efficiency of the battery cell.

[0276] In some embodiments, after the step of depositing silicon particles into the pores of porous carbon, the method further includes the step of preparing a carbon coating layer on the surface of the porous carbon or the step of depositing oxygen on the surface of the silicon particles.

[0277] The embodiments of this application improve the stability between the first active material and the electrolyte in a battery cell by either depositing silicon particles into the pores of porous carbon, followed by preparing a carbon coating layer on the surface of the porous carbon, or depositing oxygen on the surface of the silicon particles.

[0278] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0279] (1) In silicon-carbon composite materials, the weight percentage of silicon is 45wt% to 60wt%; the weight percentage of silicon in silicon-carbon composite materials can be 45wt%, 45.2wt%, 45.4wt%, 45.6wt%, 45.8wt%, 46wt%, 46.2wt%, 46.4wt%, 46.6wt%, 46.8wt%, 47wt%, 47.2wt%, 47.4wt%, 47.6wt%, 47.8wt%, 48wt%, 48.2wt%, 48.4wt%, 48.6wt%, 48.8wt%, 4 9wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6w t%, 51.8wt%, 52wt%, 52.2wt%, 52.4wt%, 52.6wt%, 52.8wt%, 53wt%, 53.2wt%, 53.4wt%, 53.6wt%, 53.8wt%, 54wt%, 54.2wt%, 54 .4wt%, 54.6wt%, 54.8wt%, 55wt%, 55.2wt%, 55.4wt%, 55.6wt%, 55.8wt%, 56wt%, 56.2wt%, 56.4wt%, 56.6wt%, 56.8wt%, 57wt %, 57.2wt%, 57.4wt%, 57.6wt%, 57.8wt%, 58wt%, 58.2wt%, 58.4wt%, 58.6wt%, 58.8wt%, 59wt%, 59.2wt%, 59.4wt%, 59.6wt%, 5 9.8wt%, 60wt%, etc., or any range of two of the above values, for example, 45wt%~47wt%, 46wt%~48wt%, 47wt%~49wt%, 48wt%~50wt%, 49wt%~51wt%, 50wt%~52wt%, 51wt%~53wt%, 52wt%~54wt%, 53wt%~55wt%, 54wt%~56wt%, 55wt%~57wt%, 56wt%~58wt%, 57wt%~59wt%, 58wt%~60wt%, etc.

[0280] (2) Silicon-carbon composite materials also include a carbon coating layer, which is coated on the surface of porous carbon.

[0281] In some embodiments, porous carbon includes one or more of the following features:

[0282] (1) The volume average particle size Dv50 of porous carbon satisfies 5μm~15μm; the volume average particle size Dv50 of porous carbon can be 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7 ... .6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9μm, 9.1μm, 9.2μm, 9 .3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, 10.1μm, 10.2μm, 10.3μm, 10.4μm, 10.5μm, 10.6μm, 10.7μm, 10.8 μm, 10.9μm, 11μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm, 12μm, 12.1μm, 12.2μm, 1 2.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7μm, 12.8μm, 12.9μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13. 7μm, 13.8μm, 13.9μm, 14μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15μm, etc., or any range of two of the above values, for example, 5μm~7μm, 6μm~8μm, 7μm~9μm, 8μm~10μm, 9μm~11μm, 10μm~12μm, 11μm~13μm, 12μm~14μm, 13μm~15μm, etc.

[0283] (2) The specific surface area of ​​porous carbon satisfies 1000 m². 2 / g~2000m 2 / g; the specific surface area of ​​porous carbon can be 1000m². 2 / g, 1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g, 1350m 2 / g, 1400m 2 / g, 1450m 2 / g, 1500m 2 / g, 1550m 2 / g, 1600m 2 / g、1650m 2 / g, 1700m 2 / g、1750m 2 / g、1800m 2 / g、1850m 2 / g、1900m 2 / g、1950m 2 / g、2000m 2 / g, or a range consisting of any two of the above values, for example, 1000m. 2 / g~1200m 2 / g、1100m 2 / g~1300m 2 / g、1200m 2 / g~1400m 2 / g、1300m 2 / g~1500m 2 / g, 1400m 2 / g~1600m 2 / g, 1500m 2 / g~1700m 2 / g, 1600m 2 / g~1800m 2 / g, 1700m 2 / g~1900m 2 / g、1800m 2 / g~2000m 2 / g etc.

[0284] (3) The pore volume of porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; the pore volume of porous carbon can be 0.6cm³. 3 / g, 0.65cm 3 / g, 0.7cm 3 / g, 0.75cm 3 / g, 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 0.95cm 3 / g, 1cm 3 / g, 1.05cm 3 / g, 1.1cm 3 / g, or a range consisting of any two of the above values, for example, 0.6cm. 3 / g~0.7cm 3 / g, 0.65cm 3 / g~0.75cm 3 / g, 0.7cm 3 / g~0.8cm 3 / g, 0.75cm 3 / g~0.85cm 3 / g, 0.8cm 3 / g~0.9cm 3 / g, 0.85cm 3 / g~0.95cm 3 / g, 0.9cm 3 / g~1cm 3 / g, 0.95cm 3 / g~1.05cm 3 / g, 1cm 3 / g~1.1cm 3 / g etc.

[0285] (4) In the pores of porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is between 0.1% and 6%; the proportion of pores with a diameter greater than or equal to 50 nm can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%. %, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, etc., or a range consisting of any two of the above values, for example, 0.1%–0.5%, 0.3%–0.7%, 0.5%–1%, 0.7%–1.3%, 1%–1.5%, 1.3%–1.7%, 1.5%–2%, 1.7%–2.3%, 2%–2.5%, 2.2%–2.7%, 2.5%–3%, 3%–5%, 4%–6%, etc.

[0286] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0287] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. All other embodiments obtained based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0288] Preparation of silicon-carbon composite material 1:

[0289] (1) Phenolic resin {chemical formula (C7H6O2)} n The material with a weight-average molecular weight of 26,800 was ground and then transferred to a muffle furnace. Under a nitrogen atmosphere, it was reacted at 900°C for 6 hours to obtain the first intermediate.

[0290] (2) The first intermediate was subjected to a pressure of 20 MPa and an atmosphere of water vapor with a flow rate of 0.2 L / min, and treated at 650 °C for 10 h. This process was repeated 3 times to obtain the second intermediate.

[0291] (3) Switch the gas source to hydrogen and place the second intermediate in a hydrogen atmosphere. The second intermediate is treated at 500°C for 3 hours in an atmosphere of hydrogen gas flow rate of 0.3 L / min to obtain porous carbon.

[0292] (4) The porous carbon is transferred to a rotary kiln and silane gas with a flow rate of 2L / min is introduced under an argon atmosphere with a flow rate of 10L / min. The carbon is then vapor-deposited at 500℃ for 18h so that the silicon source is located in the pores of the porous carbon.

[0293] The methods for preparing silicon-carbon composite materials 2-13 are similar to those for preparing silicon-carbon composite material 1, except that some parameters in the preparation process are different, as shown in Table 1. Among them, the method for preparing silicon-carbon composite material 13 adds step (5), specifically: acetylene gas is introduced, and the product obtained in step (4) is vapor-deposited at 550°C for 8 hours. The gas source is then turned off to cool down, and silicon-carbon composite material 13 with a carbon coating layer is obtained.

[0294] Table 1. Parameters of various silicon-carbon composite materials

[0295]

[0296]

[0297] Material characterization of silicon-carbon composite materials:

[0298] 1. Characterization of specific surface area and pore volume:

[0299] Nitrogen adsorption-desorption tests were performed on samples in a liquid environment (77 K) using an ASAP2020 physical adsorption analyzer manufactured by Micron Instruments, Inc. First, an appropriate amount of sample was weighed and placed in a dedicated sample tube of the instrument. After weighing both the sample tube and the sample, the tube was mounted on the instrument and degassed at a constant temperature of 200℃ for 5 hours to remove impurities from the sample channels. After degassed, the sample was weighed to obtain an accurate mass, and then remounted on the instrument for nitrogen adsorption and desorption tests. In a liquid nitrogen environment, a vacuum pump was used to adjust the actual pressure of nitrogen in the sample to achieve a relative pressure balance (actual nitrogen pressure / saturated ammonia vapor pressure), thereby obtaining the adsorption isotherm of the sample. Based on the theoretical model...

[0300] The Brunauer-Emmett-Teller (BET) algorithm can be used to obtain the specific surface area of ​​a sample.

[0301] The pore volume of the silicon-carbon composite material was calculated by fitting the specific surface area of ​​the obtained sample.

[0302] 2. Volume average particle size Dv50:

[0303] The volume average particle size Dv50 is determined by laser diffraction of particle size distribution according to GB / T 19077-2016, and can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from the UK.

[0304] 3. Characterization of pore distribution:

[0305] The true density ρ of the silicon-carbon composite material was obtained by testing with a true density meter (e.g., AccuPycⅡ1340). r The specific steps include: weighing a sample of a certain mass (denoted as m), placing it in a true density tester, sealing the test system, and introducing helium gas according to the procedure; detecting the gas pressure in the sample chamber and expansion chamber, and then applying Bohr's Law (PV = nRT, where P is the pressure in Pa and V is the gas volume in m³). 3 (T is temperature in K, n is the amount of substance of the gas in mol, and R is the molar gas constant in J / (mol·K)) The true volume V of the carbon matrix is ​​calculated. r Then the true density ρ of the silicon-carbon composite material r =m / V rThe apparent density of silicon-carbon composite materials can be determined by loading a sample of a certain mass (denoted as m) into a cylindrical mold with an inner diameter of 10 mm and applying a pressure of 200 MPa to obtain the apparent volume V0 of the carbon matrix. Therefore, the apparent density of the carbon matrix ρ0 = m / V0. The porosity of the silicon-carbon composite material is denoted as N, and then N = (1 - ρ0 / ρ r )×100%.

[0306] The porosity of silicon-carbon composite materials was statistically analyzed to obtain a characterization of the pore distribution of silicon-carbon composite materials.

[0307] The characterization data of the silicon-carbon composite materials used in each embodiment and comparative example are shown in Table 2.

[0308] 4. Grain size characterization of silicon grains:

[0309] The Bruker D8 Discover X-ray diffractometer was used for testing in accordance with JIS K0131-1996. The test conditions were as follows: the silicon-carbon composite material sample was prepared using the plate sample preparation method, CuKα rays were used as the radiation source, a copper target was used as the anode target, the voltage was 40 kV, the current was 40 mA, the anti-scattering slit was 1 mm, the scanning 2θ angle range was 20° to 80°, the step size was 0.01671°, the step time was 0.24 s, and the scanning rate was 4° / min.

[0310] Table 2 Characterization data of various silicon-carbon composite materials

[0311]

[0312]

[0313] Battery cell 1

[0314] (1) Silicon-carbon composite material 1, conductive agent (carbon black), carbon nanotubes (CNT), binder (styrene-butadiene rubber SBR), and thickener (sodium carboxymethyl cellulose CMC) were added to a deionized water solvent system in a weight ratio of 94.5%:1%:0.375%:2.8%:1.325% to obtain a first slurry. The first slurry was coated onto a first current collector using extrusion coating, and after drying, cold pressing, and slitting, a first electrode sheet was obtained.

[0315] (2) Using a polypropylene membrane as the base membrane with a thickness of 7 μm, 1 μm of alumina and 1 μm of polycarbosilane PCS are sequentially coated on the base membrane to form an isolation membrane.

[0316] (3) LiPF6 (lithium hexafluorophosphate) and LIFSI (lithium difluorosulfonyl imide) were dissolved in a solvent containing ethylene carbonate, methyl ethyl carbonate, diethyl carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1:1 to prepare an electrolyte with a concentration of 1 mol / L.

[0317] (4) Using a lithium metal sheet as the counter electrode. The first electrode, lithium metal sheet, separator and electrolyte are assembled into a CR2430 coin cell 1 in an argon-protected glove box.

[0318] The preparation of battery cells 2 to 13 is similar to that of battery cell 1, except that in step (1), silicon-carbon composite material 1 is replaced by silicon-carbon composite material 2 to 13.

[0319] Battery cell 14 is similar to battery cell 1, except that in step (1), silicon-carbon composite material 1 is replaced with SCC55 material from Group 14.

[0320] Battery cell 15 is similar to battery cell 1, except that the grain size of silicon particles in the silicon-carbon composite material in step (1) is 1.5 nm.

[0321] Battery cell 16 is similar to battery cell 1, except that the grain size of silicon particles in the silicon-carbon composite material in step (1) is 20 nm.

[0322] Performance characterization of battery cells 1 to 16:

[0323] 1. dQ / dV-V curve test of individual battery cells:

[0324] The battery cells were left to stand at 25℃ for 2 hours. Then, the cells were discharged to 0.8V at 0.33C at 25℃, and the voltage V and capacity Q of each cell were collected. The capacity increment dQ / dV corresponding to a unit voltage change (dV) was calculated, and the capacity increment curve dQ / dV-V was plotted. dQ / dV can be calculated in Excel using the SLOPE function based on the collected voltage V and capacity Q data.

[0325] 2. Initial coulombic efficiency test of individual battery cells:

[0326] At 25°C, the battery cells of the above embodiments and comparative examples were charged at a constant current rate of 0.1C to a voltage of 4.3V. The charging capacity at this time is recorded as the first charge capacity of the battery cell. After resting for 5 minutes, the cells were discharged at a constant current rate of 0.1C to a voltage of 2.0V and then rested for 5 minutes. This is one charge-discharge cycle. The discharge capacity of this cycle is recorded as the first discharge capacity of the battery cell, which is the initial capacity of the battery cell.

[0327] The first-cycle coulombic efficiency (%) of a single battery cell = first-cycle discharge capacity of the single battery cell / first-cycle charge capacity of the single battery cell × 100%.

[0328] Table 3 Performance characterization data of each battery cell

[0329]

[0330] Based on battery cells 1 to 13 and battery cells 14 to 16, it can be seen that the initial coulombic efficiency of battery cells 1 to 13 is significantly improved compared to battery cells 14 to 16. This indicates that the scheme of regulating silicon-carbon composite material in this application can effectively improve the initial coulombic efficiency of battery cells.

[0331] Example 1:

[0332] (1) Silicon-carbon composite material 1, conductive agent (carbon black), carbon nanotubes (CNT), binder (styrene-butadiene rubber SBR), and thickener (sodium carboxymethyl cellulose CMC) were added to a deionized water solvent system in a weight ratio of 94.5%:1%:0.375%:2.8%:1.325% to obtain a first slurry. The first slurry was coated onto a first current collector using extrusion coating, and after drying, cold pressing, and slitting, a first electrode sheet was obtained.

[0333] (2) The second active material (Ni) 0.96 Co 0.03 Mn 0.01 O2, conductive agent (carbon black), and binder (polyvinylidene fluoride PVDF) are added to an N-methylpyrrolidone solvent system in a weight ratio of 97:1:2 and mixed and stirred for 0.5h to 6h to obtain a second slurry. The second slurry is coated onto the second current collector using extrusion coating, and after drying, cold pressing, and slitting, the second electrode is obtained.

[0334] (3) Using a polypropylene film as the base film with a thickness of 7 μm, 1 μm of alumina and 1 μm of polycarbosilane PCS are sequentially coated on the base film to form an isolation film.

[0335] (4) Dissolve LiPF6 (lithium hexafluorophosphate) and LIFSI (lithium difluorosulfonyl imide) in a molar ratio of 4:6 in a solvent of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate and fluoroethylene carbonate FEC in a volume ratio of 1:1:1:1 to prepare an electrolyte with a concentration of 1 mol / L.

[0336] (5) The second electrode is the positive electrode, the separator and the first electrode are the negative electrode, and the bare cell is obtained by winding them in sequence and size. The bare cell is placed in the packaging shell, dried and injected with electrolyte. After vacuum sealing, standing, formation and shaping, the battery cell is obtained.

[0337] Examples 2 to 13 are similar to Example 1, except that in step (1), silicon-carbon composite material 1 is replaced with silicon-carbon composite material 2 to silicon-carbon composite material 13.

[0338] Comparative Example 1 is similar to Example 1, except that in step (1), the silicon-carbon composite material 1 is replaced with SCC55 from Group 14.

[0339] Comparative Example 2 is similar to Example 1, except that the grain size of silicon particles in the silicon-carbon composite material in step (1) is 1.5 nm.

[0340] Comparative Example 3 is similar to Example 1, except that the grain size of silicon particles in the silicon-carbon composite material in step (1) is 20 nm.

[0341] Characterization of the individual cells in each embodiment and comparative example:

[0342] 1. Surface density of the membrane: Weigh the membrane, measure its area, and calculate the ratio of weight to area to obtain the surface density of the membrane.

[0343] 2. Characterization of the compaction density of the membrane layer: The compaction density of the membrane layer is obtained by dividing the areal density of the membrane layer by the thickness of the membrane layer.

[0344] 3. Characterization of the gravimetric energy density of a single battery cell:

[0345] Step 1: Let the battery cells stand at 25℃ for 2 hours. Charge the battery cells at 0.1C at 25℃ to the charging cutoff voltage of 4.25V, and continue constant voltage charging at this charging cutoff voltage until the current is 0.05C, at which point charging stops (where C represents the rated capacity of the battery cell). Let the battery cells stand at 25℃ for 1 hour. Discharge the battery cells at 0.1C at 25℃ to the discharge cutoff voltage, and record the total discharge capacity C0 and total discharge energy E0 of the battery cells.

[0346] Step 2: Place the battery cell on the electronic balance until the weight stabilizes, and read the weight M0 of the battery cell;

[0347] Step 3: Calculate the ratio of the total discharge energy E0 of the battery cell to the weight M0 of the battery cell, and denot it as the mass energy density of the battery cell.

[0348] 4. Characterization of the capacity retention rate of individual battery cells:

[0349] Step 1: Let the battery cell stand at 25℃ for 2 hours. Charge the battery cell to 4.25V at 25℃ using 0.1C1 (where C1 represents the nominal capacity of the battery cell), then charge it at a constant voltage of 4.25V until the current reaches 0.05C1; let it stand for 1 hour; discharge it at 25℃ using 0.1C1 to 0.95C1, and record the voltage V1 at this point. Let it stand for 5 minutes. Discharge it to 2.0V at 25℃ using 0.1C1. Let it stand for 5 minutes. Charge the battery cell to 0.97C1 at 25℃ using 0.1C1, and record the voltage V2 at this point. Let it stand for 2 hours.

[0350] Step 2: Let the battery cell stand at 25℃ for 2 hours. Charge the battery cell at 0.1C1 at 25℃ to voltage V2. Let it stand for 0.5 hours. Discharge the battery cell at 0.1C1 at 25℃ to voltage V1, and record the capacity at this point as C. n Let stand for 0.5 hours. Repeat step 2 until the number of cycles n is 100 cls. Then, the capacity retention rate of the battery cell after each cycle is: P n =C n / C1×100%.

[0351] 5. Full charge expansion performance test:

[0352] The battery cell is placed at a temperature of 25°C, and its initial thickness is measured. Then, the battery cell is charged to C1 at a rate of 0.1C1, and its full-charge thickness is measured. The difference between the full-charge thickness and the initial thickness is calculated, and the percentage of the difference to the initial thickness is calculated.

[0353] Table 4 Performance characterization data of the battery cells prepared in each embodiment and comparative example.

[0354]

[0355]

[0356] According to Examples 1-13 and Comparative Examples 1-3, compared with the comparative examples, the cycle number and full charge expansion performance of the battery cells provided in each example fluctuate, while the mass energy density is improved. This indicates that the scheme of regulating silicon-carbon composite materials is beneficial to improving the battery performance of battery cells.

[0357] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0358] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0359] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A battery cell, characterized in that, include: The first electrode includes a first current collector and a first film layer disposed on at least one surface of the first current collector; The first film layer comprises a first active material, which includes a silicon-carbon composite material. The silicon-carbon composite material includes porous carbon and silicon particles located within the pores of the porous carbon. The grain size of the silicon particles is between 2 nm and 12 nm.

2. The battery cell according to claim 1, characterized in that, Using the first electrode as the positive electrode and the lithium metal sheet as the negative electrode, when discharged at 0.1C to 0.8V, the dQ / dV-V curve has the lithium intercalation phase transition peak of the silicon particles in the range of 0.4V to 0.5V.

3. The battery cell according to claim 2, characterized in that, The peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2mAh / V to 12mAh / V.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The first electrode also includes one or more of the following features: (1) The areal density of the first film layer satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 ; (2) The compaction density of the first membrane layer satisfies 1.3 g / cc to 1.7 g / cc; (3) The weight ratio of the silicon-carbon composite material in the first film layer is 40% to 60%; (4) The first active material further includes graphite, wherein the weight percentage of graphite in the first film layer is 40% to 60%; (5) The first film layer further includes a first conductive agent, a first binder and a thickener; Optionally, the first conductive agent includes one or more of carbon black, carbon nanotubes, graphite, graphene and carbon nanofibers, and / or the first binder includes one or more of styrene-butadiene rubber, polyacrylic acid, and lithium-ionized polyacrylic acid, and / or the thickener includes sodium hydroxymethyl cellulose. Optionally, the mass ratio of the first active material, the first conductive agent, the first binder and the thickener satisfies 94-95:1-1.5:2.5-3.5:1-1.

5.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The battery cell further includes a second electrode, the second electrode including a second current collector and a second film layer disposed on at least one surface of the second current collector, the second film layer containing a second active material; the battery cell uses the second electrode as the positive electrode and the first electrode as the negative electrode; The second electrode includes one or more of the following features: (1) The areal density of the second film layer satisfies 2.5 mg / cm³. 2 ~5mg / cm 2 ; (2) The compaction density of the second membrane layer satisfies 1.3 g / cc to 1.6 g / cc; (3) The second active material includes one or more of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese iron phosphate, and their respective modified compounds. (4) The second electrode also includes a second conductive agent and a second binder; Optionally, the second conductive agent comprises carbon black, and / or the second binder comprises polyvinylidene fluoride; Optionally, the mass ratio of the second active material, the second conductive agent, and the second binder satisfies 96-98:0.5-1.5:1-3; The battery cell also includes the following feature: the mass energy density of the battery cell meets the requirement of 380Wh / kg to 500Wh / kg.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The battery cell includes an electrolyte; the electrolyte includes an electrolyte salt and a solvent; or, the electrolyte includes an electrolyte salt, a solvent, and additives.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The silicon-carbon composite material includes one or more of the following characteristics: (1) In the silicon-carbon composite material, the weight percentage of silicon is 45wt% to 60wt%; (2) The silicon-carbon composite material further includes a carbon coating layer, which coats the surface of the porous carbon.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The porous carbon includes one or more of the following characteristics: (1) The volume average particle size Dv50 of the porous carbon satisfies 5μm~15μm; (2) The specific surface area of ​​the porous carbon satisfies 1000 m² / m². 2 / g~2000m 2 / g; (3) The pore volume of the porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; (4) In the porous carbon, the proportion of pores with a diameter of 2nm to 10nm is 80% to 94%; (5) In the porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%.

9. A silicon-carbon composite material, characterized in that, The silicon-carbon composite material includes porous carbon and silicon particles located within the pores of the porous carbon; the grain size of the silicon particles is between 2 nm and 12 nm.

10. The silicon-carbon composite material according to claim 9, characterized in that, Using an electrode comprising the silicon-carbon composite material as the positive electrode and a lithium metal sheet as the negative electrode, when discharged at 0.1C to 0.8V, the dQ / dV-V curve exhibits the lithium intercalation phase transition peak of the silicon particles in the range of 0.4V to 0.5V.

11. The silicon-carbon composite material according to claim 10, characterized in that, The peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2mAh / V to 12mAh / V.

12. The silicon-carbon composite material according to any one of claims 9 to 11, characterized in that, The silicon-carbon composite material includes one or more of the following characteristics: (1) In the silicon-carbon composite material, the weight percentage of silicon is 45wt% to 60wt%; (2) The silicon-carbon composite material further includes a carbon coating layer, which coats the surface of the porous carbon.

13. The silicon-carbon composite material according to any one of claims 9 to 12, characterized in that, The porous carbon includes one or more of the following characteristics: (1) The volume average particle size Dv50 of the porous carbon satisfies 5μm~15μm; (2) The specific surface area of ​​the porous carbon satisfies 1000 m² / m². 2 / g~2000m 2 / g; (3) The pore volume of the porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; (4) In the porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%; (5) In the pores of the porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%.

14. A method for preparing a silicon-carbon composite material, characterized in that, Includes the following steps: Porous carbon is provided, the porous carbon having a plurality of pores; Silicon particles are deposited into the pores of the porous carbon, wherein the grain size of the silicon particles is 2 nm to 12 nm, to form the silicon-carbon composite material.

15. The method for preparing the silicon-carbon composite material according to claim 14, characterized in that, In the porous carbon, the proportion of pores with a diameter of 2 nm to 10 nm is 80% to 94%.

16. The method for preparing the silicon-carbon composite material according to claim 15, characterized in that, Prior to the step of providing porous carbon, a step of preparing porous carbon is also included, comprising: An organic carbon source is placed in an inert atmosphere and treated at a first temperature for a first duration to obtain a first intermediate. The first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more to obtain the second intermediate. The second intermediate is placed in a reducing atmosphere, and then treated at a third temperature for a third time under a reducing gas flow atmosphere to obtain porous carbon.

17. The method for preparing the silicon-carbon composite material according to claim 16, characterized in that, The step of placing the organic carbon source in an inert atmosphere and treating it at a first temperature for a first duration includes one or more of the following features: (1) The organic carbon source includes polymeric organic carbon source; (2) The polymeric organic carbon source includes phenolic resin; (3) The first temperature satisfies 880℃~1000℃; (4) The first duration satisfies 4h to 8h.

18. The method for preparing the silicon-carbon composite material according to claim 16 or 17, characterized in that, The first intermediate is treated at a second temperature for a second duration in an atmosphere of activating gas flow, and the treatment is performed once or more, including one or more of the following characteristics: (1) The flow rate of the activated gas stream is 0.1 L / min to 0.5 L / min; (2) The activated airflow includes a water vapor airflow; (3) The first intermediate is in a pressure range of 5MPa to 30MPa; (4) The second temperature satisfies 600℃~700℃; (5) The second duration satisfies 6h to 16h; (6) The number of processing times is any one of 1 to 6 times.

19. The method for preparing the silicon-carbon composite material according to any one of claims 16 to 18, characterized in that, The step of placing the second intermediate in a reducing atmosphere and treating the second intermediate at a third temperature for a third duration under a reducing gas flow atmosphere includes one or more of the following features: (1) The reducing atmosphere includes hydrogen; (2) The flow rate of the reducing gas stream is 0.1 L / min to 0.5 L / min; (3) The third temperature satisfies 450℃~600℃; (4) The third duration satisfies 2h to 4h.

20. The method for preparing the silicon-carbon composite material according to any one of claims 14 to 19, characterized in that, The step of depositing silicon particles into the pores of the porous carbon includes: The porous carbon is placed in an inert atmosphere, and a silicon source gas is introduced for vapor deposition, so that the silicon source is located in the pores of the porous carbon.

21. The method for preparing the silicon-carbon composite material according to claim 20, characterized in that, The step of introducing silicon source gas and performing vapor deposition includes one or more of the following features: (1) The silicon source gas includes one or more of silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane; (2) The flow rate of the silicon source gas is 0.5 L / min to 5 L / min; (3) The deposition temperature of the vapor deposition satisfies 480℃~600℃; (4) The deposition time of the vapor phase deposition is 6h to 24h.

22. The method for preparing the silicon-carbon composite material according to any one of claims 14 to 21, characterized in that, After the step of depositing silicon particles into the pores of the porous carbon, the method further includes the step of preparing a carbon coating layer on the surface of the porous carbon or the step of depositing oxygen on the surface of the silicon particles.

23. The method for preparing the silicon-carbon composite material according to any one of claims 14 to 22, characterized in that, The silicon-carbon composite material includes one or more of the following characteristics: (1) In the silicon-carbon composite material, the weight percentage of silicon is 45wt% to 60wt%; (2) The silicon-carbon composite material further includes a carbon coating layer, which coats the surface of the porous carbon.

24. The method for preparing the silicon-carbon composite material according to any one of claims 14 to 23, characterized in that, The porous carbon includes one or more of the following characteristics: (1) The volume average particle size Dv50 of the porous carbon satisfies 5μm~15μm; (2) The specific surface area of ​​the porous carbon satisfies 1000 m² / m². 2 / g~2000m 2 / g; (3) The pore volume of the porous carbon satisfies 0.6 cm³. 3 / g~1.1cm 3 / g; (4) In the pores of the porous carbon, the proportion of pores with a diameter greater than or equal to 50 nm is 0.1% to 6%.

25. A battery device, characterized in that, Includes the battery cell according to any one of claims 1 to 8.

26. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1 to 8.

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