Battery cell, silicon-carbon composite material and preparation method, battery device, and electric device

Abstract

A battery cell (20), a silicon-carbon composite material and a preparation method, a battery device (100), and an electric device. The battery cell (20) comprises a first electrode sheet, the first electrode sheet comprises a silicon-carbon composite material, 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 satisfies 2-12 nm. By means of the porous carbon, an accommodating space is provided for the silicon particles to alleviate the volume expansion of the silicon particles. By means of the silicon particles having a grain size of 2-12 nm, the reaction duration of a silicon-lithium alloy is regulated, thereby reducing the excessive reaction of the silicon-carbon composite material during lithium intercalation, and reducing the amount of irreversible silicon-lithium byproducts. Due to the rational regulation of the reaction duration of the silicon-lithium alloy, a large expansion stress on the silicon particles within a short period is mitigated, electrode sheet pulverization and detachment are reduced, and the integrity of the silicon particles is improved.

Description

Battery cell, silicon-carbon composite material and preparation method, battery device and electric device

[0001] The present disclosure claims priority to the Chinese patent application No. 2024111244573, filed on August 15, 2024, and entitled "Battery cell, silicon-carbon composite material and preparation method, battery device and electric device", which is incorporated by reference in its entirety into the present disclosure. TECHNICAL FIELD

[0002] The present application relates to the technical field of new energy, and particularly relates to a battery cell, a silicon-carbon composite material and a preparation method, a battery device and an electric device. BACKGROUND

[0003] The part provided in this part is only background information related to the present application, which is not necessarily prior art.

[0004] The battery cell has high energy density and is widely used in various aspects such as wireless communication, transportation, aerospace, etc. The battery cell mainly includes a positive electrode sheet, a separator film, an electrolyte and a negative electrode sheet. The theoretical specific capacity of silicon can be as high as 4200 mAhg, and it has good application prospect as a negative electrode material. Therefore, seeking a battery cell with more excellent performance is one of the directions that the person skilled in the art focuses on.

[0005] To this end, the present application is proposed. SUMMARY

[0006] In view of the technical problems in the background art, the present application provides a battery cell, a silicon-carbon composite material and a preparation method, a battery device and an electric device, aiming to improve the first coulomb efficiency of the battery cell.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a battery cell, comprising: a first electrode sheet, comprising a first current collector and a first film layer arranged on at least one surface of the first current collector; wherein the first film layer contains a first active material, the first active material comprises a silicon-carbon composite material, the silicon-carbon composite material comprises porous carbon and silicon particles located in the pores of the porous carbon; the grain size of the silicon particles satisfies 2nm-12nm.

[0008] Embodiments of the present application provide a silicon-carbon composite material by improving the battery monomer, which provides accommodation space for silicon particles by porous carbon to relieve the volume expansion of silicon particles; the reaction time of silicon-lithium alloy is regulated by silicon particles with a grain size of 2nm-12nm, which reduces the excessive reaction of silicon-carbon composite material during lithium intercalation, reduces the amount of silicon-lithium irreversible byproducts, and slows down the expansion stress of silicon particles in a short time due to the reasonable regulation of the reaction time of silicon-lithium alloy, reduces the powdering and falling of the pole piece, improves the integrity of the silicon particles, and in addition, the reasonable regulation of the reaction time of silicon-lithium alloy also helps to improve the lithium intercalation utilization rate of silicon particles and improve the first coulomb efficiency of the battery monomer.

[0009] In some embodiments, when the first pole piece is a positive electrode and the lithium metal piece is a negative electrode, the dQ / dV-V curve has a silicon particle lithium intercalation phase transition peak in the range of 0.4V-0.5V when discharged to 0.8V at 0.33C.

[0010] Embodiments of the present application regulate the grain size of silicon particles, so that when the first pole piece is a positive electrode and the lithium metal piece is a negative electrode, the capacity increment curve dQ / dV-V has a silicon particle lithium intercalation phase transition peak at the position of 0.4V-0.5V when discharged to 0.8V at 0.33C. The battery monomer using the pole piece has good first coulomb efficiency.

[0011] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles includes 2mAh / V-12mAh / V.

[0012] Embodiments of the present application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles, so that the battery monomer using the pole piece has good first coulomb efficiency.

[0013] In some embodiments, the first pole piece further includes one or more of the following features:

[0014] (1) The areal density of the first film layer satisfies 2.5mg / cm 2 -5mg / cm 2 ; (2) The compaction density of the first film layer satisfies 1.3g / cc-1.7g / cc; (3) The weight proportion of the silicon-carbon composite material in the first film layer satisfies 40%-60%; (4) The first active material further includes graphite, and the weight proportion of the graphite in the first film layer satisfies 40%-60%; (5) The first film layer further includes a first conductive agent, a first binder, and a thickening agent;

[0015] Optionally, the first conductive agent comprises one or more of carbon black, carbon nanotube, graphite, graphene, and carbon nanofiber, and / or the first binder comprises one or more of styrene butadiene rubber, polyacrylic acid, and lithiated polyacrylic acid, and / or the thickening agent comprises sodium hydroxymethyl cellulose; optionally, the mass ratio of the first active material, the first conductive agent, the first binder, and the thickening agent satisfies 94-95: 1-1.5: 2.5-3.5: 1-1.5.

[0016] Embodiments of the present application regulate parameters of the first tab, so that the battery cell comprising the first tab has good first coulombic efficiency.

[0017] In some embodiments, the battery cell further comprises a second tab, the second tab comprising a second current collector and a second film layer disposed on at least one surface of the second current collector, the second film layer comprising a second active material; the battery cell has the second tab as a positive electrode and the first tab as a negative electrode; the second tab comprises one or more of the following features: (1) the areal density of the second tab satisfies 2.5 mg / cm 2 ~ 5 mg / cm 2 ; (2) the tap density of the second tab satisfies 1.3 g / cc-1.6 g / cc; (3) the second active material comprises 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 modified compounds of each of them; (4) the second tab further comprises a second conductive agent and a second binder;

[0018] 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.

[0019] The battery cell further comprises the following feature: the mass energy density of the battery cell satisfies 380 Wh / kg-500 Wh / kg.

[0020] Embodiments of the present application regulate parameters of the second tab, so that the battery cell comprising the first tab and the second tab has good first coulombic efficiency.

[0021] In some embodiments, the battery cell comprises an electrolyte; the electrolyte comprises an electrolyte salt, a solvent; or, the electrolyte comprises an electrolyte salt, a solvent, and an additive.

[0022] Embodiments of the present application regulate the electrolyte of the battery cell, so that the battery cell comprising the first tab and the second tab has good first coulombic efficiency.

[0023] In some embodiments, the silicon-carbon composite material includes one or more of the following features: (1) the silicon-carbon composite material has a silicon element weight percentage of 45wt% to 60wt%; (2) the silicon-carbon composite material further includes a carbon coating layer, which coats the surface of porous carbon.

[0024] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0025] In some embodiments, porous carbon includes one or more of the following features: (1) the volume average particle size Dv50 of the porous carbon is 5 μm to 15 μm; (2) the specific surface area of ​​the porous carbon is 1000 m². 2 / g~2000m 2 / g; (3) The pore volume of porous carbon satisfies 0.6cm³. 3 / g~1.1cm 3 / g; (4) The number of pores with a diameter of 2nm to 10nm in the porous carbon is 80% to 94%; (5) The number of pores with a diameter greater than or equal to 50nm in the porous carbon is 0.1% to 6%.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In some embodiments, the silicon-carbon composite material includes one or more of the following features: (1) the silicon-carbon composite material has a silicon element weight percentage of 45wt% to 60wt%; (2) the silicon-carbon composite material further includes a carbon coating layer, which coats the surface of porous carbon.

[0030] The embodiments of this application achieve good first-run coulombic efficiency in battery cells by adjusting various parameters of silicon-carbon composite materials.

[0031] In some embodiments, the dQ / dV-V curve has a lithium intercalation phase transition peak of the silicon particles in the range of 0.4V-0.5V when the electrode sheet comprising the silicon-carbon composite material is used as the positive electrode, the lithium metal sheet is used as the negative electrode, and discharged at 0.1C to 0.8V.

[0032] Embodiments of the present application control the grain size of the silicon particles, so that the capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of the silicon particles at the position of 0.4V-0.5V when the electrode sheet comprising the silicon-carbon composite material is used as the positive electrode, the lithium metal sheet is used as the negative electrode, and discharged at 0.33C to 0.8V, and the battery cell using the electrode sheet has good first coulombic efficiency.

[0033] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2mAh / V-12mAh / V.

[0034] Embodiments of the present application further control the peak value of the lithium intercalation phase transition peak of the silicon particles, so that the battery cell using the electrode sheet has good first coulombic efficiency.

[0035] In some embodiments, the porous carbon comprises one or more of the following features: (1) the volume average particle size Dv50 of the porous carbon satisfies 5μm-15μm; (2) the specific surface area of the porous carbon satisfies 1000m 2 / g-2000m 2 / g; (3) the pore volume of the porous carbon satisfies 0.6cm 3 / g-1.1cm 3 / g; (4) in the pores of the porous carbon, the number ratio of pores with a pore size of 2nm-10nm satisfies 80%-94%; (5) in the pores of the porous carbon, the number ratio of pores with a pore size greater than or equal to 50nm satisfies 0.1%-6%.

[0036] Embodiments of the present application control the parameters of the porous carbon, so that the battery cell comprising the silicon-carbon composite material has good first coulombic efficiency.

[0037] In a third aspect, embodiments of the present application provide a preparation method of a silicon-carbon composite material, comprising the following steps: providing a porous carbon, the porous carbon having a plurality of pores; depositing silicon particles into the pores of the porous carbon, the grain size of the silicon particles satisfying 2nm-12nm, to form a silicon-carbon composite material.

[0038] Embodiments of the present application provide a preparation method of a silicon-carbon composite material, and the silicon-carbon composite material formed by the preparation method is beneficial to alleviate the volume expansion of the silicon particles, improve the lithium intercalation utilization rate of the silicon particles, slow down the expansion stress of the silicon particles, and improve the integrity of the silicon particles, so as to improve the first coulombic efficiency of the battery cell containing the silicon-carbon composite material.

[0039] In some embodiments, the number of pores with a pore size of 2 nm to 10 nm accounts for 80% to 94% of the total number of pores in the porous carbon.

[0040] Embodiments of the present application regulate the pores of the porous carbon, so that the battery cell including the silicon-carbon composite material has good initial coulomb efficiency.

[0041] In some embodiments, before the step of providing the porous carbon, the method further includes a step of preparing the porous carbon, including: placing an organic carbon source in an inert atmosphere, treating the organic carbon source at a first temperature for a first duration to obtain a first intermediate; placing the first intermediate in an atmosphere of an activating gas stream, treating the first intermediate at a second temperature for a second duration, for one or more times to obtain a second intermediate; and placing the second intermediate in a reducing atmosphere, treating the second intermediate in an atmosphere of a reducing gas stream at a third temperature for a third duration, for a plurality of times to obtain the porous carbon.

[0042] Embodiments of the present application provide a method for preparing the porous carbon in the silicon-carbon composite material. The porous carbon prepared by the method has good surface performance, the lithium consumption groups on the surface of the porous carbon are reduced, and the battery cell including the silicon-carbon composite material has good initial coulomb efficiency.

[0043] In some embodiments, the step of placing the organic carbon source in an inert atmosphere and treating the organic carbon source at a first temperature for a first duration includes one or more of the following features: (1) the organic carbon source includes a polymeric organic carbon source; (2) the polymeric organic carbon source includes phenolic resin; (3) the first temperature satisfies 880°C to 1000°C; and (4) the first duration satisfies 4 h to 8 h.

[0044] Embodiments of the present application provide a method for activating the porous carbon in the silicon-carbon composite material. The first intermediate prepared by the method has fewer defects, and the surface of the first intermediate has fewer lithium consumption groups, so as to reduce the lithium consumption amount of the first intermediate. The battery cell including the silicon-carbon composite material has good initial coulomb efficiency.

[0045] In some embodiments, the step of placing the first intermediate in an atmosphere of an activating gas stream and treating the first intermediate at a second temperature for a second duration, for one or more times includes one or more of the following features: (1) the flow rate of the activating gas stream satisfies 0.1 L / min to 0.5 L / min; (2) the activating gas stream includes a water vapor gas stream; (3) the first intermediate is in a pressure range of 5 MPa to 30 MPa; (4) the second temperature satisfies 600°C to 700°C; (5) the second duration satisfies 6 h to 16 h; and (6) the number of times is any one of 1 to 6.

[0046] Embodiments of the present application provide a method for forming pores in porous carbon in a silicon-carbon composite material. The porous carbon formed by the method has fewer defects and fewer lithium-consuming groups on the surface of the porous carbon to reduce the amount of lithium consumed by the porous carbon. In addition, the method controls the pores of the porous carbon to have space to accommodate the growth of silicon particles. A battery cell including the silicon-carbon composite material has good initial coulombic efficiency.

[0047] In some embodiments, placing the second intermediate in a reducing atmosphere and treating the second intermediate at a third temperature for a third duration in the atmosphere of the reducing gas flow includes one or more of the following features: (1) the reducing atmosphere includes hydrogen; (2) a flow rate of the reducing gas flow satisfies 0.1 L / min to 0.5 L / min; (3) the third temperature satisfies 450°C to 600°C; and (4) the third duration satisfies 2 h to 4 h.

[0048] Embodiments of the present application provide a method for reducing porous carbon in a silicon-carbon composite material. The method further reduces lithium-consuming groups on the surface of the porous carbon to reduce the amount of lithium consumed by the porous carbon. A battery cell including the silicon-carbon composite material has good initial coulombic efficiency.

[0049] In some embodiments, the step of depositing silicon particles into the pores of the porous carbon includes: placing the porous carbon in an inert atmosphere, introducing a silicon source gas, and performing vapor deposition to allow the silicon particles to be located in the pores of the porous carbon.

[0050] Embodiments of the present application provide a method for preparing silicon particles in a silicon-carbon composite material. The silicon particles formed by the method have a larger grain size, which can control the reaction duration of silicon-lithium alloy, improve the lithium intercalation utilization rate of silicon particles, slow down the expansion stress of silicon particles, improve the integrity of silicon particles, and improve the initial coulombic efficiency of a battery cell.

[0051] In some embodiments, the step of introducing a 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 monosilane, disilane, dichlorosilane, trichlorosilane, and tetrachlorosilane; (2) a flow rate of the silicon source gas satisfies 0.5 L / min to 5 L / min; (3) a deposition temperature of the vapor deposition satisfies 480°C to 600°C; and (4) a deposition duration of the vapor deposition satisfies 6 h to 24 h.

[0052] Embodiments of the present application provide process parameters for a method for preparing silicon particles in a silicon-carbon composite material. The method can control the grain size of the silicon particles formed, which can control the reaction duration of silicon-lithium alloy, improve the lithium intercalation utilization rate of silicon particles, slow down the expansion stress of silicon particles, improve the integrity of silicon particles, and improve the initial coulombic efficiency of a battery cell.

[0053] In some embodiments, after the step of depositing silicon particles into the pores of the porous carbon, the method further comprises a step of preparing a carbon coating layer on the surface of the porous carbon or a step of depositing oxygen onto the surface of the silicon particles.

[0054] Embodiments of the present application improve the stability between the first active material and the electrolyte in the battery cell by, after the step of depositing silicon particles into the pores of the porous carbon, a step of preparing a carbon coating layer on the surface of the porous carbon or a step of depositing oxygen onto the surface of the silicon particles.

[0055] In some embodiments, the silicon-carbon composite material comprises one or more of the following features: (1) in the silicon-carbon composite material, the weight percentage of silicon is 45wt%-60wt%; (2) the silicon-carbon composite material further comprises a carbon coating layer, and the carbon coating layer is coated on the surface of the porous carbon.

[0056] Embodiments of the present application improve the first coulombic efficiency of the battery cell comprising the silicon-carbon composite material by regulating the parameters of the porous carbon.

[0057] In some embodiments, the porous carbon comprises one or more of the following features: (1) the volume average particle size Dv50 of the porous carbon satisfies 5-15 μm; (2) the specific surface area of the porous carbon satisfies 1000 m 2 / g-2000 m 2 / g; (3) the pore volume of the porous carbon satisfies 0.6 cm 3 / g-1.1 cm 3 / g; (4) in the pores of the porous carbon, the number percentage of pores with a pore size greater than or equal to 50 nm satisfies 0.1%-6%.

[0058] Embodiments of the present application improve the first coulombic efficiency of the battery cell comprising the silicon-carbon composite material by regulating the parameters of the porous carbon.

[0059] In a fourth aspect, embodiments of the present application provide a battery device comprising any battery cell provided in the first aspect.

[0060] The battery device provided by embodiments of the present application at least has the same advantages as the battery cell, and can improve the endurance of the battery device.

[0061] In a fifth aspect, embodiments of the present application provide an electric device comprising any battery cell provided in the first aspect.

[0062] The electric device provided by embodiments of the present application at least has the same advantages as the battery cell, and can improve the endurance of the electric device. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description only some of the embodiments of the present application, and other drawings can be obtained without creative labor.

[0064] Fig. 1 is a structural schematic diagram of a vehicle provided by an embodiment of the present application;

[0065] Fig. 2 is an exploded structural schematic diagram of a battery device provided by an embodiment of the present application;

[0066] Fig. 3 is an exploded structural schematic diagram of a battery cell provided by an embodiment of the present application.

[0067] Explanation of reference numerals:

[0068] 1000-vehicle, 100-battery device, 200-controller, 300-motor, 10-box, 20-battery cell, 11-first part, 12-second part, 21-end cover, 22-housing, 23-electrode assembly, 21a-electrode terminal. DETAILED DESCRIPTION

[0069] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0070] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. Further, each individual disclosed point or single numerical value can itself serve as a lower limit or upper limit to combine with any other point or single numerical value or to combine with other lower limits or upper limits to form a range not explicitly recited.

[0071] In the description herein, the term "or" is inclusive, unless otherwise indicated. That is, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions fulfill the condition "A or B": 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).

[0072] In the description herein, it is to be noted that, unless otherwise specified, "above", "below" are inclusive of the number itself, and "several" means two or more.

[0073] The terms used in the present application have the commonly understood meanings known in the art, unless otherwise specified. The values of each parameter mentioned in the present application can be measured by various measurement methods commonly used in the art (for example, can be tested according to the methods given in the examples of the present application), unless otherwise specified.

[0074] Silicon will undergo a large volume expansion during charging and discharging, causing the silicon to be pulverized and fall off and the repeated formation of the SEI film on the surface of the silicon negative electrode material, which seriously affects the performance of the battery cell. In addition, the conductivity of the silicon material is very poor and needs to be improved. Therefore, under the premise of retaining the advantages, the problem of volume expansion of silicon needs to be improved to improve the initial coulomb efficiency of the battery cell.

[0075] A current research trend is to improve the initial coulomb efficiency of the battery cell by using silicon-carbon composite materials. The silicon-carbon composite material can utilize the ultra-high specific capacity of silicon on the one hand, and utilize the structure of the carbon material to serve as a network support to alleviate the volume expansion of the silicon material during charging and discharging on the other hand. In addition, the carbon material has good conductivity, and forming a composite material can improve the poor conductivity of the silicon material.

[0076] However, at present, the silicon-carbon composite material generally uses silicon with a small average particle size (for example, the average particle size Dv50 is less than or equal to 2 nm), and the rate of silicon-lithium reaction is too fast, the volume expands rapidly in a short time, the silicon-carbon composite material is easily pulverized and falls off due to the large expansion stress in a short time, and a part of the silicon does not have time to react, which easily causes the insufficient utilization rate of lithium intercalation of silicon, thereby causing the problem of low initial coulomb efficiency of the battery cell.

[0077] The embodiments of the present application improve the battery cell and provide a silicon-carbon composite material. The silicon-carbon composite material provides accommodation space for silicon particles by using porous carbon to alleviate the volume expansion of the silicon particles. The silicon particles with a grain size of 2 nm to 12 nm are used to control the reaction time of silicon-lithium alloy, reduce the over-reaction of the silicon-carbon composite material during lithium intercalation, and reduce the amount of silicon-lithium irreversible by-products. Due to the reasonable control of the reaction time of the silicon-lithium alloy, the silicon particles are less likely to be subjected to a large expansion stress in a short time, the pulverization and falling off of the electrode sheet are reduced, the integrity of the silicon particles is improved, and in addition, the reasonable control of the reaction time of the silicon-lithium alloy is also beneficial to improving the lithium intercalation utilization rate of the silicon particles and improving the initial coulomb efficiency of the battery cell.

[0078] Battery cell

[0079] In the embodiments of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging to continue to be used.

[0080] The battery cell can be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid battery, etc. The embodiments of the present application are not limited thereto.

[0081] Battery apparatus

[0082] The battery apparatus mentioned in the embodiments of the present application can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, in parallel, or in a mixed connection through a busbar component.

[0083] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0084] As an example, the battery cell assembly can be a battery module formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0085] In some embodiments, the battery apparatus can be a battery pack including a case and one or more battery cell assemblies accommodated in the case.

[0086] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the case by fixing the battery module in the case.

[0087] As an example, the battery cell assembly can also be accommodated in the case by directly fixing a plurality of battery cells in the case.

[0088] As an example, the case can include a first case and a second case. The first case and the second case are coupled so that an enclosed space is formed inside the case to accommodate the battery cell assembly. Here, the enclosed means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0089] As an example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that an enclosed space is formed inside the case to accommodate the battery cell assembly.

[0090] In some embodiments, the case can be a part of a chassis structure of a vehicle. For example, a part of the case can be at least a part of a floor of the vehicle, or a part of the case can be at least a part of a cross beam and a longitudinal beam of the vehicle.

[0091] The technical solutions described in the embodiments of the present application are applicable to various electric devices using battery cells, for example, mobile phones, portable devices, notebook computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, for example, spacecraft including airplanes, rockets, space shuttles and spaceships.

[0092] The following embodiments are described for convenience with a vehicle 1000 as an example of an electric device in an embodiment of the present application.

[0093] Please refer to FIG. 1, which is a structural schematic diagram of a vehicle provided by an embodiment of the present application.

[0094] Referring to FIG. 1, the vehicle 1000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc. The vehicle 1000 is internally provided with a battery device 100, which can be arranged at the bottom, the head or the tail of the vehicle 1000. The battery device 100 can be used for power supply of the vehicle 1000, for example, the battery device 100 can be used as an operating power source of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0095] In some embodiments of the present application, the battery device 100 can not only be used as an operating power source of the vehicle 1000, but also be used as a driving power source of the vehicle 1000, instead of or partially instead of fuel or natural gas to provide driving power for the vehicle 1000.

[0096] Please refer to FIG. 2, which is an exploded structural schematic diagram of a battery device provided by an embodiment of the present application.

[0097] Referring to FIG. 2, the battery device 100 includes a case 10 and a battery cell 20 accommodated in the case 10. The case 10 is configured to provide an accommodation space for the battery cell 20, and can have various configurations. In some embodiments, the case 10 can include a first part 11 and a second part 12, which are coupled to each other to define the accommodation space for the battery cell 20. The second part 12 can have a hollow structure with an open end, and the first part 11 can have a plate structure, which is coupled to the open end of the second part 12 to define the accommodation space together with the second part 12. Alternatively, the first part 11 and the second part 12 can each have a hollow structure with an open end, and the open end of the first part 11 is coupled to the open end of the second part 12. Of course, the case 10 defined by the first part 11 and the second part 12 can have various shapes, such as a cylindrical shape, a cuboid shape, etc.

[0098] In the battery device 100, the battery cell 20 can be multiple, and the multiple battery cells 20 can be connected in series, in parallel, or in a mixed manner. The mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and the whole of the multiple battery cells 20 is accommodated in the case 10. Of course, the battery device 100 can be configured such that the multiple battery cells 20 are connected in series, in parallel, or in a mixed manner to form a battery module, and the multiple battery modules are connected in series, in parallel, or in a mixed manner to form a whole, which is accommodated in the case 10. The battery device 100 can further include other structures, for example, the battery device 100 can further include a busbar member for electrically connecting the multiple battery cells 20.

[0099] The battery cell 20 can have a cylindrical shape, a flat shape, a cuboid shape, or other shapes.

[0100] Referring to FIG. 3, FIG. 3 is an exploded structural view of a battery cell according to an embodiment of the present application.

[0101] Referring to FIG. 3, the battery cell 20 refers to the smallest unit constituting the battery device 100. The battery cell 20 includes an end cap 21, a case 22, an electrode assembly 23, and other functional components.

[0102] The end cover 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cover 21 can be adapted to the shape of the shell 22 to fit the shell 22. Optionally, the end cover 21 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 21 is less likely to deform when subjected to extrusion collision, allowing the battery cell 20 to have higher structural strength and improved safety performance. The end cover 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect with the electrode assembly 23 for outputting or inputting the electrical energy of the battery cell 20. In some embodiments, the end cover 21 can also be provided with a pressure relief mechanism for relieving the internal pressure of the battery cell 20 when the internal pressure or temperature reaches a threshold value. The material of the end cover 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereon. In some embodiments, an insulating member can also be provided on the inner side of the end cover 21, which can be used to isolate the electrical connection components in the shell 22 from the end cover 21 to reduce the risk of short circuit. Exemplarily, the insulating member can be plastic, rubber, etc.

[0103] The shell 22 is a component for fitting the end cover 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be provided on the shell 22, and the end cover 21 is covered on the opening to form the internal environment of the battery cell 20. Without limitation, the end cover 21 and the shell 22 can also be integrated, specifically, the end cover 21 and the shell 22 can form a common connecting surface before other components enter the shell, and when it is necessary to seal the internal environment of the shell 22, the end cover 21 is covered on the shell 22. The shell 22 can be various shapes and various sizes, such as cuboid, cylinder, hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereon.

[0104] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 23 can be contained within the case 22. The electrode assembly 23 is mainly formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is generally provided between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and the negative electrode sheet have portions with active materials that constitute a main body of the electrode assembly, and portions without active materials that each constitute a tab. The positive electrode tab and the negative electrode tab can be located together at one end of the main body or at opposite ends of the main body. During charging and discharging of the battery cell 20, the positive active material and the negative active material react with the electrolyte, and the tabs connect the electrode terminals to form a current loop.

[0105] The positive electrode sheet includes a current collector and a positive active layer provided on the current collector. The positive active layer includes a positive active material, which can include one or more of: lithium-containing phosphate of olivine structure, lithium transition metal oxide, and modified compounds of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive active material for a battery can also be used. These positive active materials can be used alone or in combination with two or more. Examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be referred to simply as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to simply as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be referred to simply as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be referred to simply as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to simply as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05O2) and modified compounds thereof, etc. Examples of lithium-containing phosphate with olivine structure can include, but are not limited to, one or more of lithium iron phosphate (such as LiFeP04(also can be referred to as LFP), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnP04), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0106] In an embodiment, the positive active layer further includes a positive conductive agent and a positive binder. The positive conductive agent imparts electrical conductivity to the positive active layer. The positive conductive agent can include any electrically conductive material, as long as it does not cause chemical changes. Non-limiting examples of the positive conductive agent 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 powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. The positive binder improves the adhesion stability of the positive active layer, reducing the probability of occurrence of the powder dropping. The positive binder can include 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), lithiumated polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0107] In some embodiments, the negative electrode tab includes a negative current collector and a negative active layer disposed on the negative current collector. In some embodiments, the negative active layer can further include a negative binder, a negative conductive agent, and other optional additives. As an example, the negative conductive agent can be one or more of super P (SP), carbon black {examples can include one or more of acetylene black, ketjen black, Super P (SP)}, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the negative binder can 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), lithiumated polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). As an example, the other optional additives can be thickening and dispersing agents (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.

[0108] In some embodiments, the material of the separator includes 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.

[0109] 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.

[0110] The battery cell is also referred to as a rechargeable battery or a storage battery, which is a device capable of storing chemical energy converted from electrical energy through an electrochemical reaction and releasing the stored chemical energy as electrical energy when needed. The first pole piece is a component responsible for storing or releasing lithium ions in the battery cell and is one of the core components of the energy conversion and storage of the battery. The first current collector refers to a substrate for attaching active materials in the first pole piece. The first current collector can be a metal foil or a composite current collector, which can be formed by forming a metal material or an alloy material on a high polymer material substrate such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc. The first film layer refers to a film layer formed on the first current collector. The first active material refers to a chemical substance that directly participates in an electrochemical reaction and can reversibly store and release electrical energy in the first pole piece. The first film layer of the first pole piece can be provided only on one surface of the first current collector or on opposite surfaces of the first current collector. The porous carbon refers to a carbon material having a plurality of pore structures, which contains a large number of micropores (pore diameter less than 2 nm), mesopores (pore diameter between 2 nm and 50 nm), or macropores (pore diameter greater than 50 nm) inside. The silicon particles refer to silicon particles with a size in one or several levels of microns, nanometers, and sub-nanometers.

[0111] The embodiments of the present application provide a silicon-carbon composite material by improving the battery cell. The silicon-carbon composite material provides accommodation space for the silicon particles by the porous carbon to relieve the volume expansion of the silicon particles. The silicon particles with a grain size of 2 nm to 12 nm are used to regulate the reaction duration of the silicon-lithium alloy, reduce the over-reaction of the silicon-carbon composite material during lithium intercalation, and reduce the amount of silicon-lithium irreversible by-products. Due to the reasonable regulation of the reaction duration of the silicon-lithium alloy, the silicon particles are less subjected to a large expansion stress in a short time, the pole piece is less prone to powdering and falling off, and the integrity of the silicon particles is improved. In addition, the reasonable regulation of the reaction duration of the silicon-lithium alloy is also conducive to improving the lithium intercalation utilization rate of the silicon particles and improving the initial coulombic efficiency of the battery cell.

[0112] In some embodiments, when the first pole piece is a positive electrode, the lithium metal sheet is a negative electrode, and the discharge is performed at 0.33C to 0.8V, the dQ / dV-V curve has a silicon particle lithium intercalation phase transition peak in the range of 0.4V to 0.5V.

[0113] Compared with silicon particles with a grain size less than 2 nm, the silicon particles in the application have a larger grain size, and in the lithium intercalation reaction of the battery monomer, the lithium intercalation time of the silicon particles is longer, so that the battery monomer has a more obvious lithium intercalation platform. The appearance of the lithium intercalation platform indicates that the lithium intercalation rate of the battery monomer is relatively flat, which is beneficial to reducing the lithium intercalation loss of the battery monomer, and thus beneficial to the battery monomer having a good first coulomb efficiency. The lithium intercalation phase transition peak is an external manifestation of the lithium intercalation characteristics of the silicon particles. The more obvious lithium intercalation platform is reflected in the dQ / dV-V curve, that is, the more obvious lithium intercalation phase transition peak appears. That is, when the first electrode sheet is used as the positive electrode, the lithium metal sheet is used as the negative electrode, and the discharge is carried out at 0.33C to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of the silicon particles in the range of 0.4V-0.5V, indicating that the corresponding battery monomer has a good first coulomb efficiency.

[0114] The embodiments of the application control the grain size of the silicon particles, so that when the first electrode sheet is used as the positive electrode and the lithium metal sheet is used as the negative electrode, the capacity increment curve dQ / dV-V has a lithium intercalation phase transition peak of the silicon particles at the position of 0.4V-0.5V when discharged at 0.33C to 0.8V. The battery monomer using the electrode sheet has a good first coulomb efficiency.

[0115] In some embodiments, when the first electrode sheet is used as the positive electrode and the lithium metal sheet is used as the negative electrode, the dQ / dV-V curve has a lithium intercalation phase transition peak of the silicon particles in the range of 0.4V-0.5V when discharged at 0.33C to 0.8V. The lithium intercalation phase transition peak of the silicon particles corresponds to a silicon-lithium alloy Li 15 Si4.

[0116] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2 mAh / V~12 mAh / V; the peak value of the lithium intercalation phase transition 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, 11.9 mAh / V, 12 mAh / V, or 12.1 mAh / V.9 mAh / V, 12 mAh / V, or a range between any two of the above values, for example, 2 mAh / V-4 mAh / V, 3 mAh / V-5 mAh / V, 4 mAh / V-6 mAh / V, 5 mAh / V-7 mAh / V, 6 mAh / V-8 mAh / V, 7 mAh / V-9 mAh / V, 8 mAh / V-10 mAh / V, 9 mAh / V-11 mAh / V, 10 mAh / V-12 mAh / V, etc. The peak value of the lithium intercalation phase transition peak of the silicon particles refers to the dQ / dV value corresponding to the extreme value of the lithium intercalation phase transition peak, and the unit is mAh / V.

[0117] Embodiments of the present application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles, so that the battery cell using the electrode plate has good first coulomb efficiency.

[0118] In some embodiments, the first electrode plate further comprises one or more of the following features:

[0119] (1) the areal density of the first film layer satisfies 2.5 mg / cm 2 -5 mg / cm 2 ; the areal density of the first film layer can be 2.5 mg / cm 2 , 2.6 mg / cm 2 , 2.7 mg / cm 2 , 2.8 mg / cm 2 , 2.9 mg / cm 2 , 3 mg / 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 , 4 mg / 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 / cm 2 , 5 mg / cm 2etc., or a range between any two of the above values, for example, can be 2.5 mg / cm 2 ~ 3 mg / cm 2 , 2.7 mg / cm 2 ~ 3.5 mg / cm 2 , 3.3 mg / cm 2 ~ 4 mg / cm 2 , 3.7 mg / cm 2 ~ 4.5 mg / cm 2 , 4.1 mg / cm 2 ~ 5 mg / cm 2 , etc.

[0120] (2) the first film layer has a compaction density of 1.3 g / cc to 1.7 g / cc; the compaction density of the first film 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, 1.56 g / cc, 1.57 g / cc, 1.58 g / cc, 1.59 g / cc, 1.6 g / cc, 1.61 g / cc, 1.62 g / cc, 1.63 g / cc, 1.64 g / cc, 1.65 g / cc, 1.66 g / cc, 1.67 g / cc, 1.68 g / cc, 1.69 g / cc, 1.7 g / cc, etc., or a range between any two of the above values, for example, can be 1.3 g / cc to 1.4 g / cc, 1.35 g / cc to 1.45 g / cc, 1.4 g / cc to 1.5 g / cc, 1.45 g / cc to 1.55 g / cc, 1.5 g / cc to 1.6 g / cc, 1.55 g / cc to 1.65 g / cc, 1.6 g / cc to 1.7 g / cc, etc.

[0121] (3) The weight percentage of the silicon-carbon composite material in the first film layer is 40% to 60%; the weight percentage of the 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%, or a range formed by any two of the above values, for example, 40% to 50%, 45% to 55%, 50% to 60%, etc.

[0122] (4) The first active material further includes graphite, and the weight percentage of the graphite in the first film layer is 40% to 60%; the weight percentage of the 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%, or a range formed by any two of the above values, for example, 40% to 50%, 45% to 55%, 50% to 60%, etc.

[0123] (5) The first film layer further includes a first conductive agent, a first binder, and a thickening agent; in some embodiments, 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 lithiated polyacrylic acid, and / or the thickening agent includes sodium hydroxymethyl cellulose.

[0124] In some embodiments, the mass ratio of the first active material, the first conductive agent, the carbon nanotubes, the first binder, and the thickening agent is 94 to 95: 1 to 1.5: 2.5 to 3.5: 1 to 1.5.

[0125] The area density of the first film layer represents the weight per unit area of the first film layer. The compacted density of the first film layer represents the weight per unit volume of the first film layer, which is equal to the area density of the first film layer divided by the thickness of the first film layer. The weight percentage of the silicon-carbon composite material in the first film layer represents the ratio of the weight of the silicon-carbon composite material to the total weight of the first film layer. The first active material can further include graphite and the silicon-carbon composite material provided in the present application. The capacity and / or the first coulombic efficiency of the battery cell can be adjusted by adjusting the weight percentage of the graphite and the 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 of the first film layer disperse better in the solvent, form a uniform slurry, and form a good quality first film layer, and make the first film layer and the first current collector well combined together. The thickening agent is used to improve the rheological properties of the slurry for forming the first film layer, so as to obtain a uniform and stable coating layer in the coating process.

[0126] Embodiments of the present application can regulate the parameters of the first tab, so that the battery cell including the first tab has good first coulomb efficiency.

[0127] In some embodiments, the battery cell further includes a second tab, the second tab 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 has the second tab as the positive electrode and the first tab as the negative electrode; the second tab includes one or more of the following features:

[0128] (1) The areal density of the second film layer satisfies 2.5 mg / cm 2 ~ 5 mg / cm 2 ; the areal density of the second film layer can be 2.5 mg / cm 2 , 2.6 mg / cm 2 , 2.7 mg / cm 2 , 2.8 mg / cm 2 , 2.9 mg / cm 2 , 3 mg / 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 , 4 mg / 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 / cm 2 , 5 mg / cm 2 , or a range between any two of the above values, for example, 2.5 mg / cm 2 ~ 3 mg / cm 2 , 2.7 mg / cm 2 ~ 3.5 mg / cm 2 , 3.3 mg / cm 2 ~ 4 mg / cm 2, 3.7 mg / cm 2 ~ 4.5 mg / cm 2 , 4.1 mg / cm 2 ~ 5 mg / cm 2 and the like.

[0129] (2) The second film layer has a compacted density of 1.3 g / cc to 1.6 g / cc. The compacted density of the second film 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, 1.56 g / cc, 1.57 g / cc, 1.58 g / cc, 1.59 g / cc, 1.6 g / cc, or the like, or a range defined by any two of the above values, for example, 1.3 g / cc to 1.4 g / cc, 1.35 g / cc to 1.45 g / cc, 1.4 g / cc to 1.5 g / cc, 1.45 g / cc to 1.55 g / cc, 1.5 g / cc to 1.6 g / cc, or the like.

[0130] (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 modified compounds of each thereof.

[0131] (4) The second electrode tab further includes a second conductive agent and a second binder. In some embodiments, the second conductive agent includes carbon black, and / or the second binder includes polyvinylidene fluoride. In some embodiments, the mass ratio of the second active material, the second conductive agent, and the second binder satisfies 96 to 98: 0.5 to 1.5: 1 to 3.

[0132] The battery cell further comprises the following features: the mass energy density of the battery cell satisfies 380Wh / kg-500Wh / kg. The mass energy density of the battery cell 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, 403Wh / 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, 416Wh / 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, or a range between any two of the above values, for example, 380Wh / kg-390Wh / kg, 385Wh / kg-395Wh / kg, 390Wh / kg-400Wh / kg, 395Wh / kg-405Wh / kg, 400Wh / kg-410Wh / kg, 405Wh / kg-415Wh / kg, 410Wh / kg-420Wh / 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.

[0133] In the battery cell, the positive and negative materials interact through ions (such as lithium ions) in the electrolyte to realize the mutual conversion of electrical energy and chemical energy during charging and discharging. The second electrode tab is a component responsible for storing or releasing lithium ions in the battery cell and is one of the core components of electrical energy conversion and storage. The second current collector refers to the substrate for attaching active materials in the second electrode tab. The second current collector can be a metal foil or a composite current collector, which can be formed by forming a metal material or an alloy material on a polymer material substrate (such as a substrate of 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 a chemical substance that directly participates in electrochemical reactions in the second electrode tab and can reversibly store and release electrical energy. The second film layer of the second electrode tab can be provided only on one surface of the second current collector, or can be provided on the opposite two surfaces of the second current collector. The second conductive agent is used to improve the conductivity of the second film layer and reduce the internal resistance of the second film layer. The second binder is used to help the components forming the second film layer to be better dispersed in the solvent, to form a uniform slurry, to form a second film layer with good quality, and to make the second film layer and the second current collector well combined together. The mass energy density of the battery cell refers to the total amount of energy stored in a unit mass of the battery cell, which is an important indicator for evaluating the efficiency of the battery cell in storing electrical energy, directly affects the weight, volume and endurance of the battery cell, and its unit is usually watt-hour per kilogram (Wh / kg).

[0134] Embodiments of the present application can regulate various parameters of the second electrode tab, so that the battery cell including the first electrode tab and the second electrode tab has a good first coulomb efficiency.

[0135] In some embodiments, the battery cell includes an electrolyte; the electrolyte includes an electrolyte salt, a solvent; or, the electrolyte includes an electrolyte salt, a solvent, and an additive. The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate. The solvent includes one or more of carbonate solvents, ether solvents. The carbonate solvents are typically small molecular cyclic or chain carbonates; including but not limited to one or more of vinyl carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluorinated carbonate, fluorinated vinyl carbonate; and can also be one or more of ester solvents such as gamma-butyrolactone, dimethyl sulfite, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl acetate, fluorinated carboxylic acid ester. The ether solvents include but are not limited to one or more of dimethyl ether, diethyl ether, tetrahydrofuran, methyl tetrahydrofuran, oxirane, 1,3-dioxolane, fluorinated ether, 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. In other embodiments, the electrolyte can also include one or more of amine solvents, sulfone solvents, and nitrile solvents. In some embodiments, the amine solvents include one or more of N-methyl acetamide, N-methyl formamide, dimethyl formamide, diethyl formamide. The sulfone solvents include one or more of dimethyl sulfoxide, cyclobutyl sulfone, diphenyl sulfoxide, chlorosulfoxide, dipropyl sulfone. The nitrile solvents include one or more of acetonitrile, butanedinitrile, hexanedinitrile, pentanedinitrile. The electrolyte is preferably a high-voltage-resistant electrolyte, which has a weak acidity at high voltage, can facilitate the transport of active ions, reduce the side reactions on the electrode surface, and improve the stability of the battery cell. The additive can include one or both of a negative electrode film-forming additive and a positive electrode film-forming additive, and can also include one or both of an additive that can improve certain properties of the battery cell, such as an additive that improves the overcharge performance of the battery cell, an additive that improves the high-temperature or low-temperature performance of the battery cell.

[0136] Embodiments of the present application regulate the electrolyte of the battery cell, so that the battery cell including the first electrode plate and the second electrode plate has good first coulomb efficiency. In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0137] (1) In the silicon-carbon composite material, the weight percentage of silicon element is 45wt%-60wt%; the weight percentage of silicon element in the silicon-carbon composite material 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%, 49wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6wt%, 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%, 59.8wt%, 60wt%, or a range formed by any two of the above values, for example, it can be 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.

[0138] In the silicon-carbon composite material, the weight percentage of silicon is determined according to the EPA 6010D-2014 standard; specifically, ICP-OES (elemental analysis-inductively coupled plasma atomic emission spectrometry) testing can be used, the sample to be tested is first dissolved into a liquid with a strong acid, then the liquid is introduced into the ICP light source by atomization, and further the gaseous atoms to be tested are ionized and excited in a strong magnetic field, and then return to the ground state from the excited state; the energy released in the above process is recorded as different characteristic spectral lines for element quantitative analysis.

[0139] (2) The silicon-carbon composite material further includes a carbon coating layer, which is coated on the surface of the porous carbon to improve the electrical conductivity of the first active material and the negative effects caused by the volume expansion of the silicon particles. In some embodiments, the surface of the silicon particles includes oxygen elements to passivate the reactivity of the silicon particles and improve the negative effects caused by the volume expansion of the silicon particles.

[0140] Embodiments of the present application adjust various parameters of the silicon-carbon composite material, so that the battery cell including the silicon-carbon composite material has good initial coulomb efficiency.

[0141] In some embodiments, the porous carbon includes one or more of the following characteristics:

[0142] (1) The volume average particle size Dv50 of the porous carbon satisfies 5 μm-15 μm; the volume average particle size Dv50 of the porous carbon can be 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, 12 μm, 12.1 μm, 12.2 μm, 12.3 μm, 12.4 μm, 12.5 μm, 12.6 μm, 12.7 μm, 12.8 μm, 12.9 μm, 13 μm, 13.1 μm, 13.2 μm, 13.3 μm, 13.4 μm, 13.5 μm, 13.6 μm, 13.7 μm, 13.8 μm, 13.9 μm, 14 μm, 14.1 μm, 14.2 μm, 14.3 μm, 14.4 μm, 14.5 μm, 14.6 μm, 14.7 μm, 14.8 μm, 14.9 μm, 15 μm, or the like, or a range formed by any two of the above values, for example, 5 μm-7 μm, 6 μm-8 μm, 7 μm-9 μm, 8 μm-10 μm, 9 μm-11 μm, 10 μm-12 μm, 11 μm-13 μm, 12 μm-14 μm, 13 μm-15 μm, or the like.

[0143] (2) The specific surface area of the porous carbon satisfies 1000 m 2 / g-2000 m 2 / g; the specific surface area of the porous carbon can be 1000 m 2 / g, 1050 m 2 / g, 1100 m 2 / g, 1150 m 2 / g, 1200 m 2 / g, 1250 m 2 / g, 1300 m 2 / g, 1350 m 2 / g, 1400 m 2 / g, 1450 m 2 / g, 1500 m 2 / g, 1550 m 2 / g, 1600 m 2 / g, 1650 m 2 / g, 1700 m 2 / g, 1750 m 2 / g, 1800 m 2 / g, 1850 m 2 / g, 1900 m 2 / g, 1950 m 2 / g, 2000 m 2 / g, or a range between any two of the above values, for example, can be 1000 m 2 / g to 1200 m 2 / g, 1100 m 2 / g to 1300 m 2 / g, 1200 m 2 / g to 1400 m 2 / g, 1300 m 2 / g to 1500 m 2 / g, 1400 m 2 / g to 1600 m 2 / g, 1500 m 2 / g to 1700 m 2 / g, 1600 m 2 / g to 1800 m 2 / g, 1700 m 2 / g to 1900 m 2 / g, 1800 m 2 / g to 2000 m 2 / g, etc.

[0144] (3) the pore volume of the porous carbon satisfies 0.6 cm 3 / g to 1.1 cm 3 / g; the pore volume of the porous carbon can be 0.6 cm 3 / g, 0.65 cm 3 / g, 0.7 cm 3 / g, 0.75 cm 3 / g, 0.8 cm 3 / g, 0.85 cm 3 / g, 0.9 cm 3 / g, 0.95 cm 3 / g, 1 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm, etc., or a range formed by any two of the above values, for example, 0.6 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, 0.9 cm 3 / g, etc.

[0145] (4) The number of pores with a pore size of 2 nm to 10 nm accounts for 80% to 94% of the total number of pores in the porous carbon; the number of pores with a pore size 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%, 92.5%, 93%, 93.5%, 94%, etc., or a range formed by any two of the above values, for example, 80% to 82%, 81% to 83%, 82% to 84%, 83% to 85%, 84% to 86%, 85% to 87%, 86% to 88%, 87% to 89%, 88% to 90%, 89% to 91%, 90% to 92%, 91% to 93%, 92% to 94%, etc.

[0146] (5) The number of pores with a pore size greater than or equal to 50 nm accounts for 0.1% to 6% of the total number of pores in the porous carbon; the number of pores with a pore size 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%, or a range between any two of the above values, for example, 0.1% to 0.5%, 0.3% to 0.7%, 0.5% to 1%, 0.7% to 1.3%, 1% to 1.5%, 1.3% to 1.7%, 1.5% to 2%, 1.7% to 2.3%, 2% to 2.5%, 2.2% to 2.7%, 2.5% to 3%, 3% to 5%, 4% to 6%, and the like.

[0147] Embodiments of the present application can regulate various parameters of the silicon-carbon composite material, so that the battery cell including the silicon-carbon composite material has a good first coulomb efficiency.

[0148] In a second aspect, embodiments of the present application provide a silicon-carbon composite material, which includes porous carbon and silicon particles in the pores of the porous carbon; the grain size of the silicon particles satisfies 2 nm to 12 nm.

[0149] Embodiments of the present application provide a silicon-carbon composite material, which provides accommodation space for silicon particles by porous carbon to relieve the volume expansion of the silicon particles; regulates the reaction time of silicon-lithium alloy by silicon particles with a grain size of 2 nm to 12 nm, improves the lithium intercalation utilization rate of the silicon particles, slows down the expansion stress of the silicon particles, improves the integrity of the silicon particles, and improves the first coulomb efficiency of the battery cell.

[0150] In some embodiments, the electrode sheet including the silicon-carbon composite material is a positive electrode, the lithium metal sheet is a negative electrode, and when discharged at 0.1C to 0.8V, the dQ / dV-V curve has a silicon particle lithium intercalation phase transition peak in the range of 0.4V to 0.5V.

[0151] Embodiments of the present application make the capacity increment curve dQ / dV-V of the battery cell using the electrode sheet have a lithium intercalation phase transition peak of the silicon particles at a position of 0.4V-0.5V by regulating the grain size of the silicon particles, so that the electrode sheet including the silicon-carbon composite material is used as a positive electrode, and the lithium metal sheet is used as a negative electrode, and discharged at 0.33C to 0.8V.

[0152] In some embodiments, the peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2mAh / V-12mAh / V.

[0153] Embodiments of the present application further regulate the peak value of the lithium intercalation phase transition peak of the silicon particles, so that the battery cell using the electrode sheet has good first coulomb efficiency.

[0154] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0155] (1) In the silicon-carbon composite material, the weight percentage of silicon element is 45wt%-60wt%. The weight percentage of silicon element in the silicon-carbon composite material 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%, 49wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6wt%, 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%, 59.8wt%, 60wt%, or a range formed by any 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%, and the like.

[0156] (2) The silicon-carbon composite material further comprises a carbon coating layer, which is coated on the surface of the porous carbon to improve the conductivity of the first active material and the negative effects caused by the volume expansion of the silicon particles.

[0157] The embodiments of the present application can regulate various parameters of the silicon-carbon composite material, so that the battery cell comprising the silicon-carbon composite material has good initial coulomb efficiency.

[0158] In some embodiments, the porous carbon comprises one or more of the following features:

[0159] (1) The volume average particle size Dv50 of the porous carbon satisfies 5 μm-15 μm; the volume average particle size Dv50 of the porous carbon can be 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, 12 μm, 12.1 μm, 12.2 μm, 12.3 μm, 12.4 μm, 12.5 μm, 12.6 μm, 12.7 μm, 12.8 μm, 12.9 μm, 13 μm, 13.1 μm, 13.2 μm, 13.3 μm, 13.4 μm, 13.5 μm, 13.6 μm, 13.7 μm, 13.8 μm, 13.9 μm, 14 μm, 14.1 μm, 14.2 μm, 14.3 μm, 14.4 μm, 14.5 μm, 14.6 μm, 14.7 μm, 14.8 μm, 14.9 μm, 15 μm, or the like, or a range between any two of the above values, for example, 5 μm-7 μm, 6 μm-8 μm, 7 μm-9 μm, 8 μm-10 μm, 9 μm-11 μm, 10 μm-12 μm, 11 μm-13 μm, 12 μm-14 μm, 13 μm-15 μm, or the like.

[0160] (2) The specific surface area of the porous carbon satisfies 1000 m 2 / g-2000 m 2 / g; the specific surface area of the porous carbon can be 1000 m 2 / g, 1050 m 2 / g, 1100 m 2 / g, 1150 m 2 / g, 1200 m 2 / g, 1250 m 2 / g, 1300 m 2 / g, 1350 m 2 / g, 1400 m 2 / g, 1450 m 2 / g, 1500 m 2 / g, 1550 m 2 / g, 1600 m 2 / g, 1650 m 2 / g, 1700 m 2 / g, 1750 m 2 / g, 1800 m 2 / g, 1850 m 2 / g, 1900 m 2 / g, 1950 m 2 / g, 2000 m 2 / g, or a range between any two of the above values, for example, can be 1000 m 2 / g to 1200 m 2 / g, 1100 m 2 / g to 1300 m 2 / g, 1200 m 2 / g to 1400 m 2 / g, 1300 m 2 / g to 1500 m 2 / g, 1400 m 2 / g to 1600 m 2 / g, 1500 m 2 / g to 1700 m 2 / g, 1600 m 2 / g to 1800 m 2 / g, 1700 m 2 / g to 1900 m 2 / g, 1800 m 2 / g to 2000 m 2 / g, etc.

[0161] (3) the pore volume of the porous carbon satisfies 0.6 cm 3 / g to 1.1 cm 3 / g; the pore volume of the porous carbon can be 0.6 cm 3 / g, 0.65 cm 3 / g, 0.7 cm 3 / g, 0.75 cm 3 / g, 0.8 cm 3 / g, 0.85 cm 3 / g, 0.9 cm 3 / g, 0.95 cm 3 / g, 1 cm 3 / g, 1.05 cm 3 / g, 1.1 cm 3 / g, etc., or a range formed by any two of the above values, for example, 0.6 cm 3 / g~0.7 cm 3 / g, 0.65 cm 3 / g~0.75 cm 3 / g, 0.7 cm 3 / g~0.8 cm 3 / g, 0.75 cm 3 / g~0.85 cm 3 / g, 0.8 cm 3 / g~0.9 cm 3 / g, 0.85 cm 3 / g~0.95 cm 3 / g, 0.9 cm 3 / g~1 cm 3 / g, 0.95 cm 3 / g~1.05 cm 3 / g, 1 cm 3 / g~1.1 cm 3 / g, etc.

[0162] (4) The number of pores with a pore size of 2 nm to 10 nm accounts for 80% to 94% of the total number of pores in the porous carbon; the number of pores with a pore size 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%, 92.5%, 93%, 93.5%, 94%, etc., or a range formed by any two of the above values, for example, 80% to 82%, 81% to 83%, 82% to 84%, 83% to 85%, 84% to 86%, 85% to 87%, 86% to 88%, 87% to 89%, 88% to 90%, 89% to 91%, 90% to 92%, 91% to 93%, 92% to 94%, etc.

[0163] (5) The number of pores with a pore size greater than or equal to 50 nm accounts for 0.1% to 6% of the total number of pores in the porous carbon; the number of pores with a pore size 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%, or a range between any two of the above values, for example, 0.1% to 0.5%, 0.3% to 0.7%, 0.5% to 1%, 0.7% to 1.3%, 1% to 1.5%, 1.3% to 1.7%, 1.5% to 2%, 1.7% to 2.3%, 2% to 2.5%, 2.2% to 2.7%, 2.5% to 3%, 3% to 5%, 4% to 6%, and the like.

[0164] Embodiments of the present application can regulate various parameters of the porous carbon, so that the battery cell including the silicon-carbon composite material has a good first coulomb efficiency.

[0165] In a third aspect, embodiments of the present application provide a method for preparing a silicon-carbon composite material, including the following steps:

[0166] Providing a porous carbon, the porous carbon having a plurality of pores;

[0167] Depositing silicon particles into the pores of the porous carbon, the grain size of the silicon particles being 2 nm to 12 nm, to form a silicon-carbon composite material.

[0168] Embodiments of the present application provide a method for preparing a silicon-carbon composite material, and the silicon-carbon composite material prepared by the method can alleviate the volume expansion of the silicon particles, improve the lithium intercalation utilization rate of the silicon particles, slow down the expansion stress of the silicon particles, and improve the integrity of the silicon particles, so as to improve the first coulomb efficiency of the battery cell containing the silicon-carbon composite material.

[0169] In some embodiments, the number of pores with a pore size of 2-10 nm accounts for 80-94% of the total number of pores in the porous carbon. The number of pores with a pore size of 2-10 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%, 92.5%, 93%, 93.5%, 94%, or the like, or a range defined by any two of the above values, for example, 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%, and the like.

[0170] Embodiments of the present application can regulate the pores of the porous carbon, so that the battery cell comprising the silicon-carbon composite material has a good initial coulomb efficiency.

[0171] In some embodiments, before the step of providing the porous carbon, a step of preparing the porous carbon is further included, comprising:

[0172] The organic carbon source is placed in an inert atmosphere and treated at a first temperature for a first duration to obtain a first intermediate;

[0173] The first intermediate is treated in an atmosphere of an activating gas stream at a second temperature for a second duration, and the treatment is repeated one or more times to obtain a second intermediate;

[0174] The second intermediate is placed in a reducing atmosphere, and the second intermediate is treated in an atmosphere of a reducing gas stream at a third temperature for a third duration, and the treatment is repeated several times to obtain the porous carbon.

[0175] The organic carbon source refers to an organic compound containing carbon. The organic carbon source is placed in an inert atmosphere to reduce the influence of the reaction environment on the product. The activating gas flow refers to a gas flow with specific functions introduced on purpose, and the purpose is to promote the generation and growth of pores of the organic carbon source. The first temperature provides energy for the generation and growth of pores of the organic carbon source, and the first time regulates the pore size and quantity of the pores. The first intermediate refers to the initial product of the organic carbon source after poration. It should be noted that the surface of the first intermediate can contain several oxygen-containing acidic groups. The reducing atmosphere provides an environment conducive to the occurrence of reduction reactions, so that the oxygen-containing acidic groups on the surface of the first intermediate are reduced to reduce the lithium consumption of the porous carbon and improve the initial coulombic efficiency of the battery cell. The second temperature provides energy for the reduction reaction, and the second time regulates the degree of reduction reaction. The repetition of several times refers to the process of treating the first intermediate in the atmosphere of the reducing gas flow at the second temperature for the second time length for one or several times, so as to reduce the surface defects of the porous carbon, reduce the lithium consumption of the porous carbon, and improve the initial coulombic efficiency of the battery cell.

[0176] Embodiments of the present application provide a method for preparing porous carbon in a silicon-carbon composite material. The porous carbon prepared by the method has good surface performance, the lithium consumption groups on the surface of the porous carbon are reduced, and the battery cell containing the silicon-carbon composite material has good initial coulombic efficiency.

[0177] In some embodiments, placing the organic carbon source in an inert atmosphere and treating it at a first temperature for a first time length includes one or more of the following features:

[0178] (1) The organic carbon source includes a polymeric organic carbon source;

[0179] (2) The polymeric organic carbon source includes a phenolic resin;

[0180] (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℃, or a range formed by any two of the above values, for example, it can be 880℃-890℃, 885℃-895℃, 890℃-900℃, 895℃-905℃, 900℃-910℃, 905℃-915℃, 910℃-920℃, 915℃-925℃, 920℃-930℃, 925℃-935℃, 930℃-940℃, 935℃-945℃, 940℃-950℃, 945℃-955℃, 950℃-960℃, 955℃-965℃, 960℃-970℃, 965℃-975℃, 970℃-980℃, 975℃-985℃, 980℃-990℃, 985℃-995℃, 990℃-1000℃, etc.

[0181] (4) the first duration satisfies 4h-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, or a range formed by any two of the above values, for example, it can be 4h-5h, 4.5h-5.5h, 5h-6h, 5.5h-6.5h, 6h-7h, 6.5h-7.5h, 7h-8h, etc.

[0182] The polymeric organic carbon source refers to an organic high-molecular carbon source. The phenolic resin is a synthetic resin, which is generated by polycondensation reaction of phenolic compounds (such as phenol) and aldehyde compounds (mainly formaldehyde) under the action of a catalyst.

[0183] The embodiments of the present application provide a method for activating porous carbon in a silicon-carbon composite material. The first intermediate formed by the method has fewer defects, and the surface of the first intermediate has fewer lithium-consuming groups, so as to reduce the lithium consumption of the first intermediate, and the battery cell containing the silicon-carbon composite material has good initial coulombic efficiency.

[0184] In some embodiments, the first intermediate is treated at a second temperature for a second duration under an atmosphere of an activation gas stream, and the treatment is performed one or more times, including one or more of the following features:

[0185] (1) the flow rate of the activating gas flow satisfies 0.1 L / min-0.5 L / min; the flow rate of the activating gas flow 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, 0.36 L / min, 0.37 L / min, 0.38 L / min, 0.39 L / min, 0.4 L / min, 0.41 L / min, 0.42 L / min, 0.43 L / min, 0.44 L / min, 0.45 L / min, 0.46 L / min, 0.47 L / min, 0.48 L / min, 0.49 L / min, 0.5 L / min, or the like, or a range between any two of the above values, for example, 0.1 L / min-0.2 L / min, 0.15 L / min-0.25 L / min, 0.2 L / min-0.3 L / min, 0.25 L / min-0.35 L / min, 0.3 L / min-0.4 L / min, 0.35 L / min-0.45 L / min, 0.4 L / min-0.5 L / min, or the like;

[0186] (2) the activating gas flow comprises a water vapor gas flow;

[0187] (3) the first intermediate is at a pressure in the range of 5-30 MPa; the pressure of the first intermediate 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, or a range defined by any two of the above values, for example, 5-7 MPa, 6-8 MPa, 7-9 MPa, 8-10 MPa, 9-11 MPa, 10-12 MPa, 11-13 MPa, 12-14 MPa, 13-15 MPa, 14-16 MPa, 15-17 MPa, 16-18 MPa, 17-19 MPa, 18-20 MPa, 19-21 MPa, 20-22 MPa, 21-23 MPa, 22-24 MPa, 23-25 MPa, 24-26 MPa, 25-27 MPa, 26-28 MPa, 27-29 MPa, 28-30 MPa, etc.;

[0188] (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 defined by any two of the above values, for example, 600-610℃, 605-615℃, 610-620℃, 615-625℃, 620-630℃, 625-635℃, 630-640℃, 635-645℃, 640-650℃, 645-655℃, 650-660℃, 655-665℃, 660-670℃, 665-675℃, 670-680℃, 675-685℃, 680-690℃, 685-695℃, 690-700℃, etc.;

[0189] (5) The second time length satisfies 6h-16h. The second time length 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, 15.5h, 15.75h, 16h, or the like, or a range formed by 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, or the like.

[0190] (6) The processing times are any one of 1-6 times.

[0191] Embodiments of the present application provide a method for forming pores in porous carbon in a silicon-carbon composite material. The porous carbon formed by the method has fewer defects, and the surface of the porous carbon has fewer lithium-consuming groups to reduce the amount of lithium consumed by the porous carbon. In addition, the method controls the pores of the porous carbon to have space to accommodate the growth of silicon particles, and the battery cell containing the silicon-carbon composite material has good first coulombic efficiency.

[0192] In some embodiments, placing the second intermediate in a reducing atmosphere and treating the second intermediate at a third temperature for a third time length in an atmosphere of a reducing gas includes one or more of the following features:

[0193] (1) The reducing atmosphere includes hydrogen;

[0194] (2) the flow rate of the reducing gas flow satisfies 0.1 L / min-0.5 L / min; the flow rate of the reducing gas flow 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, 0.36 L / min, 0.37 L / min, 0.38 L / min, 0.39 L / min, 0.4 L / min, 0.41 L / min, 0.42 L / min, 0.43 L / min, 0.44 L / min, 0.45 L / min, 0.46 L / min, 0.47 L / min, 0.48 L / min, 0.49 L / min, 0.5 L / min, or a range formed by any two of the above values, for example, 0.1 L / min-0.2 L / min, 0.15 L / min-0.25 L / min, 0.2 L / min-0.3 L / min, 0.25 L / min-0.35 L / min, 0.3 L / min-0.4 L / min, 0.35 L / min-0.45 L / min, 0.4 L / min-0.5 L / min, etc.;

[0195] (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 formed by any two of the above values, for example, 450℃-550℃, 500℃-600℃, etc.;

[0196] (4) the third time length satisfies 2h-4h. The third time length can be 2h, 2.25h, 2.5h, 2.75h, 3h, 3.25h, 3.5h, 3.75h, 4h, etc., or a range formed by any two of the above values, for example, 2h-3h, 2.5h-3.5h, 3h-4h, etc.

[0197] Embodiments of the present application provide a method for reducing porous carbon in a silicon-carbon composite material, further reducing lithium-consuming groups on the surface of the porous carbon to reduce the amount of lithium consumed by the porous carbon, and a battery cell comprising the silicon-carbon composite material has good initial coulombic efficiency.

[0198] In some embodiments, the step of depositing silicon particles into the pores of the porous carbon includes:

[0199] The porous carbon is placed in an inert atmosphere, and a silicon source gas is introduced to perform vapor deposition so that the silicon particles are located in the pores of the porous carbon. The silicon source gas is a gaseous compound that serves as a source of silicon elements in the vapor deposition process. During the vapor deposition process, the silicon source is decomposed to form silicon particles that are deposited in the pores of the porous carbon.

[0200] Embodiments of the present application provide a method for preparing silicon particles in a silicon-carbon composite material. The silicon particles prepared by this method have a large grain size, which can control the reaction time of silicon-lithium alloy, improve the utilization rate of lithium intercalation of silicon particles, reduce the expansion stress of silicon particles, improve the integrity of silicon particles, and improve the initial coulombic efficiency of the battery cell.

[0201] In some embodiments, the step of introducing the silicon source gas to perform vapor deposition includes one or more of the following features:

[0202] (1) The silicon source gas includes one or more of monosilane, disilane, dichlorosilane, trichlorosilane, and tetrachlorosilane;

[0203] (2) the flow rate of the silicon source gas satisfies 0.5 L / min to 5 L / min; the flow rate of the silicon source gas can be 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1 L / min, 1.1 L / min, 1.2 L / min, 1.3 L / min, 1.4 L / min, 1.5 L / min, 1.6 L / min, 1.7 L / min, 1.8 L / min, 1.9 L / min, 2 L / min, 2.1 L / min, 2.2 L / min, 2.3 L / min, 2.4 L / min, 2.5 L / min, 2.6 L / min, 2.7 L / min, 2.8 L / min, 2.9 L / min, 3 L / min, 3.1 L / min, 3.2 L / min, 3.3 L / min, 3.4 L / min, 3.5 L / min, 3.6 L / min, 3.7 L / min, 3.8 L / min, 3.9 L / min, 4 L / min, 4.1 L / min, 4.2 L / min, 4.3 L / min, 4.4 L / min, 4.5 L / min, 4.6 L / min, 4.7 L / min, 4.8 L / min, 4.9 L / min, 5 L / min, or a range formed by any two of the above values, for example, 0.5 L / min to 1.5 L / min, 1 L / min to 2 L / min, 1.5 L / min to 2.5 L / min, 2 L / min to 3 L / min, 2.5 L / min to 3.5 L / min, 3 L / min to 4 L / min, 3.5 L / min to 4.5 L / min, 4 L / min to 5 L / min, etc.;

[0204] (3) the deposition temperature of the vapor deposition satisfies 480°C to 600°C; the deposition temperature of the vapor deposition can be 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or a range formed by any two of the above values, for example, 480°C to 530°C, 500°C to 550°C, 520°C to 570°C, 550°C to 600°C, etc.;

[0205] (4) The deposition time of the vapor deposition satisfies 6h-24h. The deposition time of the vapor deposition can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, or a range formed by any two of the above values, for example, 6h-8h, 7h-9h, 8h-10h, 9h-11h, 10h-12h, 11h-13h, 12h-14h, 13h-15h, 14h-16h, 15h-17h, 16h-18h, 17h-19h, 18h-20h, 19h-21h, 20h-22h, 21h-23h, 22h-24h, and the like.

[0206] Embodiments of the present application provide process parameters of a method for preparing silicon particles in a silicon-carbon composite material. The method can control the grain size of the prepared silicon particles, control the reaction time of the silicon-lithium alloy, improve the lithium intercalation utilization rate of the silicon particles, slow down the expansion stress of the silicon particles, improve the integrity of the silicon particles, and improve the first coulombic efficiency of the battery cell.

[0207] In some embodiments, after the step of depositing silicon particles into the pores of the porous carbon, the method further includes a step of preparing a carbon coating layer on the surface of the porous carbon or a step of depositing oxygen onto the surface of the silicon particles.

[0208] Embodiments of the present application improve the stability between the first active material and the electrolyte in the battery cell by preparing a carbon coating layer on the surface of the porous carbon or depositing oxygen onto the surface of the silicon particles after the step of depositing silicon particles into the pores of the porous carbon.

[0209] In some embodiments, the silicon-carbon composite material includes one or more of the following features:

[0210] (1) In the silicon-carbon composite material, the weight percentage of silicon element is 45wt% to 60wt%. The weight percentage of silicon element in the silicon-carbon composite material 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%, 49wt%, 49.2wt%, 49.4wt%, 49.6wt%, 49.8wt%, 50wt%, 50.2wt%, 50.4wt%, 50.6wt%, 50.8wt%, 51wt%, 51.2wt%, 51.4wt%, 51.6wt%, 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%, 59.8wt%, 60wt%, or a range between any two of the above values, for example, 45wt% to 47wt%, 46wt% to 48wt%, 47wt% to 49wt%, 48wt% to 50wt%, 49wt% to 51wt%, 50wt% to 52wt%, 51wt% to 53wt%, 52wt% to 54wt%, 53wt% to 55wt%, 54wt% to 56wt%, 55wt% to 57wt%, 56wt% to 58wt%, 57wt% to 59wt%, 58wt% to 60wt%, and the like.

[0211] (2) The silicon-carbon composite material further comprises a carbon coating layer, which is coated on the surface of the porous carbon.

[0212] In some embodiments, the porous carbon comprises one or more of the following features:

[0213] (1) The volume average particle size Dv50 of the porous carbon satisfies 5 μm-15 μm; the volume average particle size Dv50 of the porous carbon can be 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, 12 μm, 12.1 μm, 12.2 μm, 12.3 μm, 12.4 μm, 12.5 μm, 12.6 μm, 12.7 μm, 12.8 μm, 12.9 μm, 13 μm, 13.1 μm, 13.2 μm, 13.3 μm, 13.4 μm, 13.5 μm, 13.6 μm, 13.7 μm, 13.8 μm, 13.9 μm, 14 μm, 14.1 μm, 14.2 μm, 14.3 μm, 14.4 μm, 14.5 μm, 14.6 μm, 14.7 μm, 14.8 μm, 14.9 μm, 15 μm, or the like, or a range formed by any two of the above values, for example, 5 μm-7 μm, 6 μm-8 μm, 7 μm-9 μm, 8 μm-10 μm, 9 μm-11 μm, 10 μm-12 μm, 11 μm-13 μm, 12 μm-14 μm, 13 μm-15 μm, or the like.

[0214] (2) The specific surface area of the porous carbon satisfies 1000 m 2 / g-2000 m 2 / g; the specific surface area of the porous carbon can be 1000 m 2 / g, 1050 m 2 / g, 1100 m 2 / g, 1150 m 2 / g, 1200 m 2 / g, 1250 m 2 / g, 1300 m 2 / g, 1350 m 2 / g, 1400 m 2 / g, 1450 m 2 / g, 1500 m 2 / g, 1550 m 2 / g, 1600 m 2 / g, 1650 m 2 / g, 1700 m 2 / g, 1750 m 2 / g, 1800 m 2 / g, 1850 m 2 / g, 1900 m 2 / g, 1950 m 2 / g, 2000 m 2 / g, or a range between any two of the above values, for example, can be 1000 m 2 / g to 1200 m 2 / g, 1100 m 2 / g to 1300 m 2 / g, 1200 m 2 / g to 1400 m 2 / g, 1300 m 2 / g to 1500 m 2 / g, 1400 m 2 / g to 1600 m 2 / g, 1500 m 2 / g to 1700 m 2 / g, 1600 m 2 / g to 1800 m 2 / g, 1700 m 2 / g to 1900 m 2 / g, 1800 m 2 / g to 2000 m 2 / g, etc.

[0215] (3) the pore volume of the porous carbon satisfies 0.6 cm 3 / g to 1.1 cm 3 / g; the pore volume of the porous carbon can be 0.6 cm 3 / g, 0.65 cm 3 / g, 0.7 cm 3 / g, 0.75 cm 3 / g, 0.8 cm 3 / g, 0.85 cm 3 / g, 0.9 cm 3 / g, 0.95 cm 3 / g, 1 cm 3 / g, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.8 cm, or a range between any two of the above values, for example, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.65 cm 3 / g, 0.75 cm 3 / g, 0.7 cm 3 / g, 0.8 cm 3 / g, 0.75 cm 3 / g, 0.85 cm 3 / g, 0.8 cm 3 / g, 0.9 cm 3 / g, 0.85 cm 3 / g, 0.95 cm 3 / g, 0.9 cm 3 / g, 1 cm 3 / g, 0.95 cm 3 / g, 1.05 cm 3 / g, 1 cm 3 / g, 1.1 cm 3 / g, etc.

[0216] (4) The number of pores with a pore size greater than or equal to 50 nm accounts for 0.1% to 6% of the total number of pores in the porous carbon; the number of pores with a pore size 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 between any two of the above values, for example, 0.1% to 0.5%, 0.3% to 0.7%, 0.5% to 1%, 0.7% to 1.3%, 1% to 1.5%, 1.3% to 1.7%, 1.5% to 2%, 1.7% to 2.3%, 2% to 2.5%, 2.2% to 2.7%, 2.5% to 3%, 3% to 5%, 4% to 6%, etc.

[0217] The beneficial effects of the present application will be further illustrated in the following examples.

[0218] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with the embodiments and the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature, and in no way is to be considered as limiting of the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained without creative labor are within the scope of protection of the present application.

[0219] Preparation of silicon-carbon composite material 1:

[0220] (1) The phenolic resin {chemical formula (C7H6O2) n with a weight average molecular weight of 26800} was ground, and then transferred to a muffle furnace, reacted at a temperature of 900℃ for 6h under a nitrogen atmosphere, to obtain a first intermediate.

[0221] (2) The first intermediate was placed under a pressure of 20MPa, and treated at 650℃ for 10h under a steam flow with a flow rate of 0.2L / min, repeated for 3 times, to obtain a second intermediate;

[0222] (3) The gas source was switched to hydrogen, and the second intermediate was placed in a hydrogen atmosphere, and the second intermediate was treated at 500℃ for 3h under a hydrogen flow with a flow rate of 0.3L / min, to obtain a porous carbon.

[0223] (4) The porous carbon was transferred to a rotary furnace, and argon gas with a flow rate of 10L / min was introduced, and silane gas with a flow rate of 2L / min was introduced, and vapor deposition was carried out at a temperature of 500℃ for 18h, so that the silicon source was located in the pores of the porous carbon.

[0224] The methods for preparing silicon-carbon composite materials 2-13 are similar to the method for preparing silicon-carbon composite material 1, except that some parameters in the preparation process are different, and the specific parameters are shown in Table 1. Among them, the method for preparing silicon-carbon composite material 13 increases step (5), specifically: acetylene gas is introduced, and the product obtained in step (4) is subjected to vapor deposition at 550℃ for 8h, and the gas source is closed for cooling, to obtain a silicon-carbon composite material 13 with a carbon coating layer.

[0225] Table 1: Parameter table of each silicon-carbon composite material

[0226] Material characterization of silicon-carbon composite materials:

[0227] 1. Specific surface area and pore volume characterization: The ASAP2020 physical adsorption analyzer produced by American Micromeritics Company was used to test the nitrogen adsorption and desorption of the sample in a liquid environment (77K). First, an appropriate amount of sample was weighed and placed in a special sample tube of the instrument. After weighing the sample tube and the sample, they were installed on the instrument for 5h degassing treatment at 200℃ constant temperature to remove impurity gases in the sample pores. After degassing, the sample was weighed to obtain the accurate sample mass, and then reinstalled on the instrument for nitrogen adsorption and desorption test. In a liquid nitrogen environment, the actual pressure of nitrogen in the sample was adjusted by a vacuum pump to achieve the balance of the relative pressure (actual pressure of nitrogen / ammonia saturated vapor pressure), so as to obtain the adsorption isotherm of the sample. According to the theoretical model, the specific surface area of the sample can be obtained by Brunauer-Emmett-Teller (BET) algorithm. The pore volume of the silicon-carbon composite material is calculated by the obtained specific surface area.

[0228] 2. Volume average particle size Dv50: The volume average particle size Dv50 is conveniently determined by a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of the United Kingdom, according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0229] 3. Pore distribution characterization: The true density of the silicon-carbon composite material ρ r is obtained by a true density tester (such as AccuPyc II 1340 type). The specific steps include: weighing a certain mass (denoted as m) of sample and placing it in the true density tester, closing the test system, and introducing helium gas according to the program; the gas pressure in the sample chamber and the expansion chamber is detected, and then the true volume V r of the carbon matrix is calculated according to the Boyle's law (PV=nRT, where: P is the pressure Pa, V is the gas volume m3, T is the temperature K, n is the amount of substance of gas mol, and R is the molar gas constant J / (mol.K)). r Then the true density ρ r of the silicon-carbon composite material is m / V r . The apparent density of the silicon-carbon composite material can be obtained by loading a certain mass (denoted as m) of sample into a cylindrical mold with an inner diameter of 10mm, and applying a pressure of 200MPa to obtain the apparent volume V0 of the carbon matrix. The apparent density of the carbon matrix is ρ0=m / V0. The porosity of the silicon-carbon composite material is denoted as N, then N=(1-ρ0 / ρ r )×100%. The porosity of the silicon-carbon composite material is counted to obtain the pore distribution characterization of the silicon-carbon composite material. The characterization data of the silicon-carbon composite material used in each example and comparative example are shown in Table 2.

[0230] 4. Grain size characterization of silicon grains: a Bruker D8 Discover X-ray diffractometer was used to test the silicon-carbon composite material according to JIS K0131-1996, with the following test conditions: the sample of the silicon-carbon composite material was prepared by the flat plate method, CuKa radiation was 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 2 theta angle range was 20°-80°, the step size was 0.01671°, the time for each step was 0.24 s, and the scanning rate was 4° / min.

[0231] Table 2 Characterization data of each silicon-carbon composite material

[0232] Battery cell 1

[0233] (1) The silicon-carbon composite material 1, conductive agent (carbon black), carbon nanotube (CNT), binder (styrene-butadiene rubber SBR), thickening agent (sodium hydroxymethyl cellulose CMC) were added to the deionized water solvent system in a weight ratio of 94.5%:1%:0.375%:2.8%:1.325%, mixed and stirred for 3 h to obtain a first slurry. The first slurry was coated on the first current collector using extrusion coating, and then dried, cold-pressed, and cut to obtain a first electrode sheet.

[0234] (2) A polypropylene film was used as the base film, the thickness of the base film was 7 μm, and 1 μm of aluminum oxide and 1 μm of polycarbosilane PCS were coated on the base film in sequence to form a separator film.

[0235] (3) LiPF6 (lithium hexafluorophosphate) and LIFSI (lithium bisfluorosulfonylimide) were dissolved in a solvent mixed at a volume ratio of 1:1:1:1 of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate in a molar ratio of 4:6 to prepare an electrolyte with a concentration of 1 mol / L.

[0236] (4) A lithium metal sheet was used as the counter electrode. The first electrode sheet, lithium metal sheet, separator film, and electrolyte were assembled into a CR2430 type button cell 1 in an argon glove box.

[0237] The preparation of battery cell 2 to battery cell 13 was similar to that of battery cell 1, except that the silicon-carbon composite material 1 in step (1) was replaced by silicon-carbon composite material 2 to silicon-carbon composite material 13.

[0238] Battery cell 14 was similar to battery cell 1, except that the silicon-carbon composite material 1 in step (1) was replaced by SCC55 material from Group 14.

[0239] The battery cell 15 is similar to the battery cell 1, except that the grain size of the silicon particles in the silicon-carbon composite material in step (1) is 1.5 nm.

[0240] The battery cell 16 is similar to the battery cell 1, except that the grain size of the silicon particles in the silicon-carbon composite material in step (1) is 20 nm.

[0241] Performance characterization of the battery cell 1 to the battery cell 16:

[0242] 1. dQ / dV-V curve test of the battery cell: The battery cell is placed at 25℃ for 2h. The battery cell is discharged at 0.33C to 0.8V at 25℃, and the voltage V and capacity Q of the battery cell are collected; the capacity increment dQ / dV corresponding to a unit voltage change (dV) is calculated; and then the capacity increment curve dQ / dV-V is plotted. The dQ / dV can be calculated by using the SLOPE function in EXCEL based on the collected voltage V and capacity Q data.

[0243] 2. First coulombic efficiency test of the battery cell: At 25℃, the battery cell of the above examples and comparative examples is charged at 0.1C rate to a voltage of 4.3V, and the charging capacity at this time is recorded as the first charging capacity of the battery cell; then it is placed for 5min, and then discharged at 0.1C rate to a voltage of 2.0V, and placed for 5min, which is one charge-discharge cycle. The discharge capacity at this time is recorded as the first discharge capacity of the battery cell, which is the initial capacity of the battery cell. The first coulombic efficiency of the battery cell (%) = the first discharge capacity of the battery cell / the first charging capacity of the battery cell x 100%.

[0244] Table 3: Performance characterization data of each battery cell

[0245] According to the battery cell 1 to the battery cell 13 and the battery cell 14 to the battery cell 16, it can be seen that the first coulombic efficiency of the battery cell 1 to the battery cell 13 is obviously improved compared with the battery cell 14 to the battery cell 16, which indicates that the scheme for regulating the silicon-carbon composite material in the present application can effectively improve the first coulombic efficiency of the battery cell.

[0246] Example 1:

[0247] (1) The silicon-carbon composite material 1, conductive agent (carbon black), carbon nanotube (CNT), binder (styrene-butadiene rubber SBR), thickening agent (sodium hydroxymethyl cellulose CMC) are added to the deionized water solvent system in a weight ratio of 94.5%:1%:0.375%:2.8%:1.325%, and mixed and stirred for 3h to obtain a first slurry. The first slurry is coated on the first current collector by extrusion coating, and then dried, cold-pressed, and cut to obtain a first electrode sheet.

[0248] (2) The second active material (Ni 0.96 Co 0.03 Mn 0.01 O2), a conductive agent (carbon black), and a binder (polyvinylidene fluoride PVDF) were added to an N-methylpyrrolidone solvent system in a ratio of 97:1:2 by weight, mixed and stirred for 0.5-6 h to obtain a second slurry. The second slurry was coated on the second current collector using extrusion coating, and then dried, cold-pressed, and cut to obtain a second electrode sheet.

[0249] (3) A polypropylene film was used as a base film, and the thickness of the base film was 7 μm. An aluminum oxide layer with a thickness of 1 μm and a polycarbosilane PCS layer with a thickness of 1 μm were sequentially coated on the base film to form a separator film.

[0250] (4) LiPF6 (lithium hexafluorophosphate) and LIFSI (lithium bisfluorosulfonylimide) were dissolved in a solvent mixture of ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate FEC in a volume ratio of 1:1:1:1 in a molar ratio of 4:6 to prepare an electrolyte with a concentration of 1 mol / L.

[0251] (5) The second electrode sheet was a positive electrode, the separator film, and the first electrode sheet was a negative electrode, which were sequentially and dimensionally wound to obtain a bare battery cell. The bare battery cell was placed in a packaging shell, and after drying, the electrolyte was injected. The battery cell was obtained after the processes of vacuum packaging, standing, formation, shaping, and the like.

[0252] Examples 2-13 were similar to Example 1, except that in step (1), the silicon-carbon composite material 1 was replaced by silicon-carbon composite materials 2-13.

[0253] Comparative Example 1 was similar to Example 1, except that in step (1), the silicon-carbon composite material 1 was replaced by SCC55 from Group 14. Comparative Example 2 was similar to Example 1, except that in step (1), the grain size of the silicon particles in the silicon-carbon composite material was 1.5 nm. Comparative Example 3 was similar to Example 1, except that in step (1), the grain size of the silicon particles in the silicon-carbon composite material was 20 nm.

[0254] Characterization of the battery cells of the examples and comparative examples:

[0255] 1. The areal density of the film layer: the weight of the film layer was measured, the area of the film layer was measured, and the ratio of the weight to the area of the film layer was calculated to obtain the areal density of the film layer.

[0256] 2. Characterization of the compacted density of the film layer: the areal density of the film layer was divided by the thickness of the film layer to obtain the compacted density of the film layer.

[0257] 3. Characterization of the mass energy density of the battery cell:

[0258] Step 1: The battery cell was placed at 25 °C for 2 h. The battery cell was charged at 0.1C (wherein C represents the rated capacity of the battery cell) to 4.25 V at 25 °C, and constant voltage charging was continued at the charging cut-off voltage until the current was 0.05C, and the charging cut-off (wherein C represents the rated capacity of the battery cell). The battery cell was placed at 25 °C for 1 h. The battery cell was discharged at 0.1C to the discharge cut-off voltage at 25 °C, and the total discharge capacity C0 and the total discharge energy E0 discharged by the battery cell were recorded;

[0259] Step 2: The battery cell was placed on an electronic balance until the weight was stable, and the weight M0 of the battery cell was read;

[0260] Step 3: The ratio of the total discharge energy E0 of the battery cell to the weight M0 of the battery cell was calculated, and was recorded as the mass energy density of the battery cell.

[0261] 4, Characterization of the capacity retention rate of the battery cell:

[0262] Step 1: The battery cell was placed at 25 °C for 2 h. The battery cell was charged at 0.1C1 (wherein C1 represents the nominal capacity of the battery cell) to 4.25 V at 25 °C, and constant voltage charging was continued at 4.25 V until the current was 0.05C1; it was placed for 1 h; it was discharged at 0.1C1 to 0.95C1 at 25 °C, and the voltage V1 at this time was recorded. It was placed for 5 min. It was discharged at 0.1C1 to 2.0 V at 25 °C. It was placed for 5 min. The battery cell was charged at 0.1C1 to 0.97C1 at 25 °C, and the voltage V2 at this time was recorded. It was placed for 2 h.

[0263] Step 2: The battery cell was placed at 25 °C for 2 h. The battery cell was charged at 0.1C1 to the voltage V2 at 25 °C. It was placed for 0.5 h. The battery cell was discharged at 0.1C1 to the voltage V1 at 25 °C, and the capacity C at this time was recorded. n It was placed for 0.5 h. Step 2 was repeated to the cycle number n of 100 cls. Then the capacity retention rate of the battery cell after each cycle was: P n = C n / C1x 100%.

[0264] 5, Full charge expansion performance test: The battery cell was placed at a temperature of 25 °C, the initial thickness of the battery cell at this time was measured, then the battery cell was charged to C1 at 0.1C1, the full charge thickness of the battery cell at this time was measured, the difference between the full charge thickness and the initial thickness was calculated, and the percentage of the difference to the initial thickness was calculated.

[0265] Table 4 Performance characterization data of the battery cells prepared in each example and the comparative example

[0266] According to the embodiments 1-13 and the comparative examples 1-3, it can be seen that, compared with the comparative examples, the cycle number and the full charge expansion performance of the battery cells provided in the embodiments fluctuate, and the mass energy density is improved, which indicates that the scheme for regulating and controlling the silicon-carbon composite material is beneficial to improving the battery performance of the battery cell.

[0267] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the embodiments of the device described above are merely schematic; for example, the division of the units is only a logical function division; there can be another division manner in actual implementation; for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, or the among different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0268] In addition, each of the functional units in the embodiments of the present application can be integrated in a processing unit, or each unit can exist alone physically, or two or more units can be integrated in a unit. The above integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0269] The above descriptions are merely some embodiments of the present application, but not to limit the patent scope of the present application; any equivalent structure or equivalent flow transformation made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A battery cell, wherein, The battery cell comprises: a first electrode sheet comprising a first current collector and a first film layer disposed on at least one surface of the first current collector; wherein the first film layer comprises a first active material, the first active material comprising a silicon-carbon composite material, the silicon-carbon composite material comprising porous carbon and silicon particles located in pores of the porous carbon; the silicon particles having a grain size of 2-12 nm.

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

3. The battery cell of claim 2, wherein, The peak value of the lithium intercalation phase transition peak of the silicon particles is 2-12 mAh / V.

4. The battery cell according to any one of claims 1 to 3, wherein, The first electrode sheet further comprises one or more of the following features: (1) the areal density of the first film layer satisfies 2.5 mg / cm 2 ~ 5 mg / cm 2 ; (2) the first film layer has a compaction density of 1.3-1.7 g / cc; (3) the weight percentage of the silicon-carbon composite material in the first film layer is 40-60%; (4) the first active material further comprises graphite, and the weight percentage of the graphite in the first film layer is 40-60%; (5) the first film layer further comprises a first conductive agent, a first binder, and a thickening agent.

5. The battery cell of claim 4, wherein, The first conductive agent comprises one or more of carbon black, carbon nanotubes, graphite, graphene, and carbon nanofibers, and / or the first binder comprises one or more of styrene-butadiene rubber, polyacrylic acid, and lithiated polyacrylic acid, and / or the thickening agent comprises sodium hydroxymethyl cellulose.

6. The battery cell of claim 4, wherein, The mass ratio of the first active material, the first conductive agent, the first binder, and the thickening agent is 94-95:1-1.5:2.5-3.5:1-1.

5.

7. The battery cell according to any one of claims 1 to 6, wherein, The battery cell further comprises a second electrode sheet comprising a second current collector and a second film layer disposed on at least one surface of the second current collector, the second film layer comprising a second active material; the battery cell uses the second electrode sheet as a positive electrode and the first electrode sheet as a negative electrode. The second electrode sheet comprises one or more of the following features: (1) the areal density of the second film layer satisfies 2.5 mg / cm 2 ~ 5 mg / cm 2 ; (2) the second film layer has a compaction density of 1.3-1.6 g / cc; (3) the second active material comprises 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 modified compounds of each of them; (4) the second electrode sheet further comprises a second conductive agent and a second binder; The battery cell further comprises the following feature: the mass energy density of the battery cell is 380-500 Wh / kg.

8. The battery cell of claim 7, wherein, The second conductive agent comprises carbon black, and / or the second binder comprises polyvinylidene fluoride.

9. The battery cell of claim 7, wherein, The mass ratio of the second active material, the second conductive agent, and the second binder is 96-98:0.5-1.5:1-3.

10. The battery cell of any one of claims 1-9, wherein, The battery cell comprises an electrolyte; the electrolyte comprises an electrolyte salt, a solvent; or the electrolyte comprises an electrolyte salt, a solvent, and an additive.

11. The battery cell of any one of claims 1-10, wherein, The silicon-carbon composite material comprises one or more of the following features: (1) the silicon element in the silicon-carbon composite material accounts for 45wt%-60wt% by weight; (2) the silicon-carbon composite material further comprises a carbon coating layer, and the carbon coating layer is coated on the surface of the porous carbon.

12. The battery cell of any one of claims 1-11, wherein, The porous carbon comprises one or more of the following characteristics: (1) the Dv50 of the porous carbon satisfies 5μm-15μm; (2) the specific surface area of the porous carbon satisfies 1000 m 2 / g ~ 2000 m 2 / g; (3) the porous carbon has a pore volume of 0.6 cm3 / g to 1.1 cm3 / g 3 / g to 1.1 cm3 / g 3 / g to 1.1 cm3 / g (4) in the pores of the porous carbon, the number ratio of pores with a pore size of 2nm-10nm satisfies 80%-94%; (5) in the pores of the porous carbon, the number ratio of pores with a pore size greater than or equal to 50nm satisfies 0.1%-6%.

13. A silicon-carbon composite material, wherein, The silicon-carbon composite material comprises porous carbon and silicon particles in the pores of the porous carbon; the grain size of the silicon particles satisfies 2nm-12nm.

14. The silicon-carbon composite of claim 13, wherein, When the electrode sheet comprising the silicon-carbon composite material is used as a positive electrode, a lithium metal sheet is used as a negative electrode, and 0.1C is discharged to 0.8V, the dQ / dV-V curve has a lithium intercalation phase transition peak of the silicon particles in the range of 0.4V-0.5V.

15. The silicon-carbon composite of claim 14, wherein, The peak value of the lithium intercalation phase transition peak of the silicon particles satisfies 2mAh / V-12mAh / V.

16. The silicon-carbon composite material of any one of claims 13-15, wherein, The silicon-carbon composite material comprises one or more of the following characteristics: (1) the silicon element in the silicon-carbon composite material accounts for 45wt%-60wt% by weight; (2) the silicon-carbon composite material further comprises a carbon coating layer, and the carbon coating layer is coated on the surface of the porous carbon.

17. The silicon-carbon composite material of any one of claims 13-16, wherein, The porous carbon comprises one or more of the following characteristics: (1) the Dv50 of the porous carbon satisfies 5μm-15μm; (2) the specific surface area of the porous carbon satisfies 1000 m 2 / g ~ 2000 m 2 / g; (3) the porous carbon has a pore volume of 0.6 cm3 / g to 1.1 cm3 / g 3 / g to 1.1 cm3 / g 3 / g; (4) in the pores of the porous carbon, the number ratio of pores with a pore size of 2nm-10nm satisfies 80%-94%; (5) in the pores of the porous carbon, the number ratio of pores with a pore size greater than or equal to 50nm satisfies 0.1%-6%.

18. A method of making a silicon-carbon composite material, wherein, The method comprises the following steps: providing porous carbon, wherein the porous carbon has a plurality of pores; depositing silicon particles into the pores of the porous carbon, wherein the grain size of the silicon particles satisfies 2nm-12nm, and the silicon-carbon composite material is formed.

19. The method of making a silicon-carbon composite of claim 18, wherein, In the pores of the porous carbon, the number ratio of pores with a pore size of 2nm-10nm satisfies 80%-94%.

20. The method of making a silicon-carbon composite of claim 19, wherein, Before the step of providing porous carbon, the method further comprises a step of preparing porous carbon, comprising: placing an organic carbon source in an inert atmosphere, treating the organic carbon source at a first temperature for a first time length, to obtain a first intermediate; treating the first intermediate in an atmosphere of an activating gas stream at a second temperature for a second time length, wherein the treatment is performed one or more times, to obtain a second intermediate; placing the second intermediate in a reducing atmosphere, and treating the second intermediate in an atmosphere of a reducing gas stream at a third temperature for a third time length, to obtain the porous carbon.

21. The method of making a silicon-carbon composite of claim 20, wherein, The step of placing the organic carbon source in an inert atmosphere, treating the organic carbon source at a first temperature for a first time length comprises one or more of the following characteristics: (1) the organic carbon source comprises a polymeric organic carbon source; (2) the polymeric organic carbon source comprises a phenolic resin; (3) the first temperature satisfies 880℃-1000℃; (4) the first time length satisfies 4h-8h.

22. The method of making a silicon-carbon composite material of claim 20 or 21, wherein, The first intermediate is treated at a second temperature for a second duration under an atmosphere of an activating gas stream, the treatment being performed one or more times, including one or more of the following features: (1) the flow rate of the activating gas stream is 0.1 L / min to 0.5 L / min; (2) the activating gas stream includes a water vapor stream; (3) the first intermediate is at a pressure of 5 MPa to 30 MPa; (4) the second temperature is 600 °C to 700 °C; (5) the second duration is 6 h to 16 h; (6) the treatment is performed one to six times.

23. The method of making a silicon-carbon composite material according to any one of claims 20-22, wherein, The second intermediate is placed in a reducing atmosphere, and the second intermediate is treated at a third temperature for a third duration under an atmosphere of a reducing gas stream, including 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 is 450 °C to 600 °C; (4) the third duration is 2 h to 4 h.

24. The method of making a silicon-carbon composite material according to any one of claims 18-23, wherein, 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 to perform vapor deposition so that the silicon source is located in the pores of the porous carbon.

25. The method of making a silicon-carbon composite of claim 24, wherein, The step of introducing the silicon source gas to perform vapor deposition includes one or more of the following features: (1) the silicon source gas includes one or more of monosilane, disilane, 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 is 480 °C to 600 °C; (4) the deposition duration of the vapor deposition is 6 h to 24 h.

26. The method of making a silicon-carbon composite of any one of claims 18-25, wherein, After the step of depositing silicon particles into the pores of the porous carbon, a step of preparing a carbon coating layer on the surface of the porous carbon or a step of depositing oxygen on the surface of the silicon particles is further included.

27. The method of making a silicon-carbon composite of any one of claims 18-26, wherein, The silicon-carbon composite material includes one or more of the following features: (1) in the silicon-carbon composite material, the weight percentage of silicon is 45 wt% to 60 wt%; (2) the silicon-carbon composite material further includes a carbon coating layer, and the carbon coating layer is coated on the surface of the porous carbon.

28. The method of making a silicon-carbon composite of any one of claims 18-27, wherein, The porous carbon includes one or more of the following features: (1) the Dv50 of the porous carbon is 5 μm to 15 μm; (2) the specific surface area of the porous carbon satisfies 1000 m 2 / g ~ 2000 m 2 / g; (3) the porous carbon has a pore volume of 0.6 cm3 / g to 1.1 cm3 / g 3 / g to 1.1 cm3 / g 3 / g to 1.1 cm3 / g (4) in the pores of the porous carbon, the number percentage of pores with a pore size greater than or equal to 50 nm is 0.1% to 6%.

29. A battery device, wherein, The battery cell includes any one of claims 1 to 12.

30. An electrical device, comprising: The battery cell includes any one of claims 1 to 12.

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