Battery monomer, battery device and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece, a negative pole piece and an isolating membrane, the negative pole piece comprises a negative current collector and a negative membrane layer arranged on at least one side of the negative current collector, the negative membrane layer comprises a negative active material, and the negative active material comprises a carbon matrix and a lithium alloy material located on at least part of the surface of the carbon matrix; the lithium ion diffusion coefficient of the negative electrode active material is 10 <-11 > cm < 2 > s <-1 >-10 <-7 > cm < 2 > s <-1 >; according to the invention, the negative active material of the battery monomer is improved, so that the fast charging performance and the service life of the battery monomer at a low temperature are improved.

Description

Technical Field

[0001] This application relates to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used in electronic devices, energy, and energy storage due to their high capacity and light weight. With the continuous expansion of lithium-ion battery applications and the demands of social development, higher requirements are being placed on their performance, such as fast charging at low temperatures and lifespan. Summary of the Invention

[0003] In view of the above problems, this application provides a battery cell, a battery device, and an electrical device. The battery cell includes a lithium-ion diffusion coefficient of 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1 The negative electrode active material can improve the fast charging performance of battery cells at low temperatures (referred to as fast charging performance) while also extending the service life of battery cells.

[0004] In a first aspect, this application provides a battery cell, including a positive electrode, a negative electrode, and a separator located between the positive and negative electrode, wherein...

[0005] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive active material. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including a negative active material, the negative active material including a carbon matrix and a lithium alloy material located on at least a portion of the surface of the carbon matrix, such that the lithium-ion diffusion coefficient of the negative active material is 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1 .

[0006] This application introduces lithium alloy material into the negative electrode active material, thereby achieving a lithium-ion diffusion coefficient of 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1On the one hand, the lithium-ion diffusion coefficient of the negative electrode active material is within the aforementioned range, which can improve the migration rate of lithium ions in the negative electrode, thereby improving the charging capability of the battery cell at low temperatures. On the other hand, the negative electrode active material with lithium alloy material on its surface has a large interaction force with the organic electrolyte, resulting in a small contact angle between it and the electrolyte. Therefore, the electrolyte can fully wet the electrode, thereby reducing the risk of lithium plating and improving the service life of the battery cell. Therefore, this application can improve the fast charging performance of the battery cell at low temperatures while also considering the service life of the battery cell.

[0007] In some embodiments, the lithium alloy material includes non-lithium elements, including at least one selected from Zn, Mg, Si, Al, Cu, Ag, Sb, Cr, Pt, Zr, Ca, and Ti. This lithium alloy material allows the lithium-ion diffusion coefficient of the negative electrode active material to be within a suitable range, which is beneficial for improving the charging capability of the battery cell at low temperatures.

[0008] In some embodiments, the lithium alloy material includes non-lithium elements, which can be at least one of Zn, Mg, and Al. Using a lithium alloy material containing non-lithium elements can achieve a lithium-ion diffusion coefficient of 10 for the negative electrode active material. -8 cm 2 s -1 ~10 -7 cm 2 s -1 This helps to achieve better dynamic effects, thereby improving the fast charging performance of individual battery cells at low temperatures.

[0009] In some embodiments, based on the mass of the negative electrode active material, the mass content of non-lithium elements in the negative electrode active material is 0.1% to 5%, and the non-lithium elements include at least one selected from Zn, Mg, Si, Al, Cu, Ag, Sb, Cr, Pt, Zr, Ca, and Ti. Controlling the mass content of non-lithium elements in the negative electrode active material within the above range helps the battery cell to achieve optimal kinetic performance at low temperatures.

[0010] In some embodiments, based on the mass of the negative electrode active material, the mass content of lithium alloy material in the negative electrode active material is 0.1% to 15%, and optionally 0.5% to 10%. Controlling the mass content of lithium alloy material in the negative electrode active material within the above range can ensure that the battery cell performs well at low temperatures while reducing the impact on initial efficiency and capacity degradation.

[0011] In some embodiments, the thickness of the lithium alloy material is 1 nm to 100 nm. By controlling the thickness of the lithium alloy material on the carbon matrix surface within the above range, the lithium alloy material has a small impact on the initial efficiency and the capacity of the battery cell. While improving the fast charging performance of the battery cell at low temperatures, it also takes into account the cycle stability of the battery cell and improves the service life of the battery cell.

[0012] In some embodiments, the carbon matrix includes a graphite material, which can be at least one of artificial graphite and natural graphite. Selecting a suitable graphite material can improve the material's conductivity, thereby enhancing the fast-charging performance of the battery cell at low temperatures.

[0013] In some embodiments, the carbon matrix includes amorphous carbon materials, including soft carbon and hard carbon. Selecting a suitable amorphous carbon material facilitates the reversible insertion and extraction of lithium ions, extending the lifespan of individual battery cells.

[0014] In some embodiments, amorphous carbon material is located on at least a portion of the surface of the graphite material. This can improve the conductivity of the graphite material, which helps to improve the fast-charging performance of the battery cell at low temperatures.

[0015] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 1 μm to 35 μm, and can be selected as 4 μm to 15 μm. Controlling the particle size of the negative electrode active material within the above range can shorten the lithium ion transport path in the negative electrode film and improve the fast charging performance of the battery cell at low temperatures.

[0016] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g~2.5m 2 / g. Controlling the specific surface area of ​​the negative electrode active material within the above range is beneficial to the contact between the electrolyte and the negative electrode active material, and further improves the fast charging performance of the battery cell at low temperatures.

[0017] In some embodiments, the graphitization degree of the negative electrode active material is 90% to 98%. By selecting a material with a graphitization degree within the above range, the conductivity of the negative electrode active material is relatively excellent, thereby improving the fast charging performance of the battery cell at low temperatures.

[0018] In some implementations, the film resistance of the negative electrode is 0.002Ω to 0.006Ω. A lower film resistance in the negative electrode is beneficial for improving the fast-charging performance of the battery cell.

[0019] In some embodiments, the compaction density of the negative electrode film layer is 1.0 g / cm³ when the battery cell is at 100% charge. 3 ~1.4g / cm 3When the compaction density of the negative electrode film is within the above range, the negative electrode active material can be packed more tightly, increasing the energy density of the battery cell; at the same time, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet and also help improve the fast charging performance of the battery cell at low temperatures.

[0020] In some embodiments, the positive electrode active material can be at least one of lithium iron phosphate, lithium manganese phosphate, lithium nickel cobalt manganese oxide, and their modified compounds. Selecting a suitable positive electrode active material can improve the energy density of a single battery cell.

[0021] In some embodiments, the positive electrode film compaction density is 2.4 g / cm³ when the battery cell is 100% charged. 3 ~2.65g / cm 3 When the compaction density of the positive electrode film is within a suitable range, the battery cell has a high energy density.

[0022] Secondly, this application provides a battery device including the battery cell of the first aspect. The battery device has at least the same advantages as the aforementioned battery cell.

[0023] Thirdly, this application provides an electrical device that includes the battery device of the second aspect. The electrical device has at least the same advantages as the battery device described above. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0025] Figure 1 These are scanning electron microscope comparison images of Embodiment 1 and Comparative Example 1 of this application;

[0026] Figure 2 This is a comparison diagram of the X-ray photoelectron energy spectrum of Comparative Example 1 of Embodiment 1 of this application;

[0027] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0028] Figure 4 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0029] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application;

[0030] Figure 6This is a schematic diagram of a battery pack according to one embodiment of this application;

[0031] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown;

[0032] Figure 8 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] The following detailed description, with appropriate reference to the accompanying drawings, discloses the battery, battery filling method, electrolyte, preparation method thereof, and electrical device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] With the continuous expansion of lithium-ion battery applications, higher demands are being placed on their fast-charging performance and lifespan at low temperatures. Currently, improvements in the low-temperature charging capability of individual battery cells mainly focus on reducing the negative electrode interface impedance and enhancing the solid-phase diffusion capability of lithium ions in the negative electrode active material. This is closely related to the surface coating layer of the negative electrode active material. Traditional coating layers consist of soft or hard carbon coated on the surface of the negative electrode active material, resulting in an increase in active sites. While this can improve the fast-charging capability of the battery cell, it also intensifies side reactions, deteriorating the cycle performance or storage life of the battery cell. Therefore, traditional solutions cannot simultaneously address both the fast-charging performance and lifespan of the battery cell.

[0042] In view of the above problems, this application improves the fast-charging performance and lifespan of battery cells by rationally designing the negative electrode active material and fabricating it into battery cells. The battery cells of this application can be widely used in consumer electronics, electric vehicles, energy storage, communications, aerospace, medical devices and other fields.

[0043] battery cell

[0044] The battery cell includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive active material. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative active material. The negative active material includes a carbon matrix and a lithium alloy material located on at least a portion of the surface of the carbon matrix. The lithium-ion diffusion coefficient of the negative active material is 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1 .

[0045] "At least part of the surface" can refer to a portion of the surface of an object or the entire surface of an object.

[0046] The carbon matrix includes graphite materials and amorphous carbon materials, with the amorphous carbon materials located on at least a portion of the surface of the graphite materials.

[0047] Lithium alloy materials refer to alloy materials composed of lithium and non-lithium elements. The non-lithium elements can be either metallic or non-lithium elements.

[0048] In some embodiments, the lithium-ion diffusion coefficient of the negative electrode active material is 10. -11 cm 2 s -1 ~10 -7 cm2 s -1 For example, the lithium-ion diffusion coefficient of the negative electrode active material can be 10. -11 cm 2 s -1 10 -10 cm 2 s -1 10 -9 cm 2 s -1 10 - 8 cm 2 s -1 10 -7 cm 2 s -1 , or a range consisting of any two of the above values.

[0049] In the embodiments of this application, the lithium-ion diffusion coefficient of the negative electrode active material can be detected using equipment and methods known in the art, and can be tested using the galvanostatic intermittent titration (GITT) method described in document DOI: 10.3969 / j.issn.2095-4239.2015.01.010. For example, the negative electrode sheet made of the negative electrode active material is cut into small negative electrode discs with a diameter of 14 mm, and the separator is cut into small separator discs with a diameter of 15 mm. The lithium sheet with a diameter of 13 mm, the above-mentioned separator discs, and the above-mentioned negative electrode discs are stacked to form an electrode assembly, and 0.15 ml of electrolyte (the composition of the electrolyte is as described in Example 1) is added. The above substances are sealed with a shell to prepare a coin cell, which is then connected to an electrochemical workstation (instrument model: Shanghai Chenhua Electrochemical Workstation CHI700E) for measurement.

[0050] In the embodiments of this application, the 100% state of charge and 0% state of charge of a single battery cell are defined as follows: charging the battery cell at a constant current charging rate of 0.33C to the upper limit charging voltage of 3.8V, and then charging it at a constant voltage of 0.05C, corresponds to the 100% state of charge of the battery cell; discharging the battery cell at a constant current discharging rate of 0.33C to the cutoff voltage of 2V, corresponds to the 0% state of charge of the battery cell.

[0051] In the embodiments of this application, the surface morphology of the negative electrode active material in the battery cell can be detected using equipment and instruments known in the art. For example, after discharging the battery cell to 0% state of charge, the negative electrode sheet is disassembled, and the negative electrode active material obtained by cleaning and drying with DMC is used as a sample. A scanning electron microscope (SEM) of model Sigma300, instrument number LEEQ044H, is used to measure the surface morphology of the negative electrode active material in accordance with the standard GB / T0584-2020 to obtain a high-resolution image of the surface morphology of the negative electrode active material.

[0052] In summary, this application achieves a lithium-ion diffusion coefficient of 10 by introducing a lithium alloy material and placing it on the surface of a carbon matrix. -11 cm 2 s -1 ~10 -7 cm 2 s -1 The lithium-ion diffusion coefficient of the negative electrode active material is greater than that of the solid electrolyte interphase (SEI) film on the graphite surface. This indicates a stronger ability to conduct lithium ions. However, an excessively high lithium-ion diffusion coefficient in the negative electrode active material is detrimental to the performance of the battery cell, leading to a rapid increase in internal temperature and further affecting the battery cell's lifespan. Therefore, selecting a negative electrode active material with a lithium-ion diffusion coefficient within the aforementioned range can, on the one hand, improve the migration rate of lithium ions in the negative electrode active material, enhancing the fast-charging performance of the battery cell at low temperatures; on the other hand, the stronger interaction between the negative electrode active material with the organic electrolyte and the lithium alloy material on its surface results in a smaller contact angle, allowing the electrolyte to fully wet the electrode, thereby reducing the risk of lithium plating and improving the battery cell's lifespan. Therefore, lithium-ion batteries can achieve a balance between improving fast-charging performance at low temperatures and extending battery lifespan.

[0053] Negative electrode sheet

[0054] Lithium alloy materials include non-lithium elements, which can be at least one of Zn, Mg, Si, Al, Cu, Ag, Sb, Cr, Pt, Zr, Ca, and Ti.

[0055] In the embodiments of this application, the types of non-lithium elements can be determined using equipment and methods known in the art. For example, the negative electrode can be disassembled after the battery cell is discharged to 0% state of charge, and the negative electrode active material obtained by cleaning and drying with DMC can be used as a sample. Energy scattering spectroscopy is used for testing, and an X-ray photoelectron spectroscopy (XPS) instrument model is Sigma300, instrument number LEEQ00GF, and the types of non-lithium elements are determined in accordance with the standard GB / T 17359-2012.

[0056] In some embodiments, using lithium alloy materials containing the aforementioned non-lithium elements can make the lithium-ion diffusion coefficient of the negative electrode active material within a suitable range. Therefore, lithium-ion migration at the negative electrode becomes easier and faster, thereby improving the fast-charging performance of the battery cell at low temperatures.

[0057] Lithium alloy materials include non-lithium elements, which can be at least one of Zn, Mg and Al.

[0058] In some embodiments, using a lithium alloy material containing the aforementioned non-lithium elements can result in a lithium-ion diffusion coefficient of 10 for the negative electrode active material. -8 cm 2 s -1 ~10 -7 cm 2 s -1 This allows battery cells to exhibit better dynamic performance at low temperatures, thereby improving the fast-charging performance of battery cells.

[0059] Based on the mass of the negative electrode active material, the mass content of non-lithium elements in the negative electrode active material is 0.1% to 5%.

[0060] In this embodiment, the mass content of non-lithium elements in the negative electrode active material can be detected using equipment and methods known in the art. In this embodiment, the negative electrode sheet can be disassembled after the battery cell is discharged to 0% state of charge. The negative electrode active material obtained by cleaning and drying with DMC is used as a sample. Energy dispersive spectroscopy is used for testing, and an X-ray energy dispersive spectroscopy (EDS) instrument model Axis Supra / Supra+, instrument number LEEQ044H is selected. The mass content of non-lithium elements in the negative electrode active material is determined according to the standard GB / T 33502-2017 / ISO.

[0061] In some embodiments, the mass content of non-lithium elements in the negative electrode active material is 0.1% to 5%. For example, the mass content of non-lithium elements in the negative electrode active material is 0.1%, 1%, 2%, 3%, 4%, 5%, or any combination of two of the above values. Controlling the mass content of non-lithium elements in the negative electrode active material within the above range is beneficial for the lithium alloy material to be located on the surface of the carbon matrix, further contributing to better kinetic performance of the battery cell and improving the fast-charging performance of the battery cell at low temperatures.

[0062] Based on the mass of the negative electrode active material, the mass content of lithium alloy material in the negative electrode active material is 0.1% to 15%, and can be selected as 0.5% to 10%.

[0063] In the embodiments of this application, the mass content of lithium alloy material in the negative electrode active material can be detected using equipment and methods known in the art. The detection method is the same as that for determining the mass content of non-lithium elements described above.

[0064] In some embodiments, the mass content of lithium alloy material in the negative electrode active material is 0.1% to 15%, optionally 0.5% to 10%. Exemplarily, the mass content of lithium alloy material elements in the negative electrode active material can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination of two of the above values.

[0065] A low lithium alloy content in the negative electrode active material prevents the formation of a suitable thickness of lithium alloy material on the carbon matrix surface, resulting in insufficient kinetic performance of the battery cell. Conversely, a high lithium alloy content in the negative electrode active material reduces the initial efficiency and capacity of the battery cell.

[0066] The thickness of lithium alloy materials ranges from 1 nm to 100 nm.

[0067] In some embodiments, the thickness of the lithium alloy material on the carbon substrate surface is controlled to be 1 nm to 100 nm. For example, it can be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any combination of two of these values. Vapor phase deposition coating, liquid phase deposition coating, solid phase deposition coating, atomic deposition techniques, etc., can be used to control the thickness of the lithium alloy material within the above range and to position it on the carbon substrate surface. The thickness of the lithium alloy material refers to the longest straight-line distance along the carbon substrate surface to the opposite surface of the lithium alloy material located on the carbon substrate surface.

[0068] The thickness of lithium alloy materials within the above range is beneficial to the dynamic performance of battery cells, while having little impact on initial efficiency and battery capacity. It improves the fast charging performance of battery cells at low temperatures, while also taking into account the cycle stability of battery cells and extending the service life of battery cells.

[0069] The carbon matrix includes graphite materials, which can be at least one of artificial graphite and natural graphite.

[0070] In some embodiments, the graphite material can be secondary particles. Due to its rich pore structure, the graphite of secondary particles increases the number of channels for lithium ions to be inserted and extracted within the lattice, and has excellent ion transport performance, which is beneficial for the insertion and extraction of lithium ions and further improves the rate performance of the battery cell; it can also improve the ion conductivity of the material, which is beneficial for improving the fast charging performance of the battery cell at low temperatures.

[0071] Carbon matrix includes amorphous carbon materials, which can be soft carbon or hard carbon.

[0072] In some embodiments, amorphous carbon refers to transitional carbon materials with a low degree of graphitization and crystallization, exhibiting an approximately amorphous morphology or lacking a fixed shape and periodic structural regularity. In this application, amorphous carbon refers to the product of carbonization treatment with an organic carbon source, which has numerous end faces and defects, and a large number of lithium ion sites. The organic carbon source can be one or more of coal tar pitch and petroleum pitch.

[0073] In the embodiments of this application, amorphous carbon materials are beneficial to the reversible insertion and extraction of lithium ions and to the fast charging performance of battery cells at low temperatures.

[0074] Amorphous carbon material is located on at least part of the surface of graphite material.

[0075] In some implementations, at least a portion of the surface of the amorphous carbon material, which is the only graphite material, can improve the conductivity of the graphite material, thereby helping to improve the fast charging performance of the battery cell at low temperatures.

[0076] The volume average particle size Dv50 of the negative electrode active material is 1μm to 35μm, and can be selected as 4μm to 15μm.

[0077] In the embodiments of this application, the volume average particle size Dv50 of the negative electrode active material refers to the particle size corresponding to 50% of the volume distribution. It can be detected using equipment and methods known in the art. For example, the negative electrode active material can be used as a sample, and the Dv50 of the sample can be tested using a Mastersizer2000E laser particle size analyzer according to the test standard GB / T19077-2016.

[0078] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 1 μm to 35 μm, and optionally 4 μm to 15 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 1 μm, 4 μm, 7 μm, 10 μm, 13 μm, 16 μm, 19 μm, 22 μm, 25 μm, 28 μm, 31 μm, 35 μm, or a range consisting of any two of the above values.

[0079] Controlling the particle size of the negative electrode active material within the above range can shorten the lithium ion transport path in the negative electrode film and improve the fast charging performance of the battery cell at low temperatures.

[0080] The specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g~2.5m 2 / g.

[0081] In the embodiments of this application, the specific surface area of ​​the negative electrode active material can be detected using equipment and methods known in the art, and can be detected according to the test standard GB / T 19587-2004. For example, the negative electrode active material can be used as a sample and tested according to the static nitrogen adsorption method using a Tristarll 3020 specific surface area analyzer.

[0082] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g~2.5m 2 / g. For example, the specific surface area of ​​the negative electrode active material can be 0.5m². 2 / g, 0.8m 2 / g, 1.1m 2 / g, 1.4m 2 / g, 1.7m 2 / g, 2.0m 2 / g, 2.3m 2 / g, 2.5m 2 / g or a range consisting of any two of the above values.

[0083] The fact that the specific surface area of ​​the negative electrode active material is within the above range means that when in contact with the electrolyte, more of the active material surface is exposed in the electrolyte, thus providing more reaction sites for electrochemical reactions. This makes it easier and faster for active ions to insert and extract at the electrode and electrolyte interface, thereby improving the fast charging performance of the battery cell at low temperatures.

[0084] The graphitization degree of the negative electrode active material is 90%–98%.

[0085] In the embodiments of this application, the degree of graphitization of the negative electrode active material can be detected using equipment and methods known in the art, and the detection can be performed in accordance with the standard GB / T 40219-2021. For example, after discharging the battery cell to 0% state of charge, the negative electrode sheet is disassembled and Raman spectroscopy analysis is performed using a laser microconfocal Raman spectrometer, specifically an InViaQontor Reflex instrument.

[0086] Graphitization degree is a physical quantity that measures the extent to which carbon atoms form a close-packed hexagonal graphite crystal structure. In the embodiments of this application, the graphitization degree of the negative electrode active material is within the above-mentioned range, resulting in a more ordered crystal structure, which is beneficial for lithium ion insertion and extraction and improves the fast-charging performance of the battery cell at low temperatures.

[0087] The film resistance of the negative electrode is 0.002Ω to 0.006Ω.

[0088] In this embodiment, the film resistance of the negative electrode refers to the ability of current to flow through the negative electrode (the cross-section of the current-carrying current collector and the film layer containing electrode material located on both sides of the current-carrying current collector along the thickness direction). It can be tested using the following method: After discharging the battery to 0% SOC, disassemble the negative electrode and clean it more than three times with a solvent such as dimethyl carbonate (DMC). Cut the dried negative electrode slurry (film layer) into small round pieces with a diameter of 3mm from a flat area of ​​the negative electrode. Place the small round pieces into an electrode resistance meter (model: Yuaneng Technology, BER2500) for testing. After the reading stabilizes, take the reading. Test two locations for each small round piece, and finally calculate the average of six measurements, which is the film resistance of the negative electrode.

[0089] In some embodiments, the film resistance of the negative electrode is 0.002Ω to 0.006Ω, and can be 0.002Ω, 0.003Ω, 0.004Ω, 0.005Ω, 0.006Ω, or any combination of two of the above values. A lower film resistance and better conductivity of the negative electrode are beneficial for improving the fast-charging performance of the battery cell at low temperatures.

[0090] When the battery cell is 100% charged, the compaction density of the negative electrode film is 1.0 g / cm³. 3 ~1.4g / cm 3 .

[0091] In this embodiment, the compaction density can be tested using equipment and methods known in the art, referring to standard GB / T 24533-2019. For example: after charging a battery cell to 100% state of charge, disassemble the negative electrode sheet. Take a single-sided coated negative electrode sheet (if it is a double-sided coated electrode sheet, wipe the negative electrode coating on one side first), cut it into a small circular piece with an area of ​​S, weigh it as M1, and measure its thickness as H1. Then wipe off the above-mentioned negative electrode film coating, leaving the substrate circular piece, weigh it as M0, and measure its thickness as H0. The coating weight of the negative electrode film is: (M1 - M0) / S, and the thickness of the negative electrode film is: H1 - H0. The compaction density of the negative electrode film is: negative electrode film coating weight / negative electrode film thickness.

[0092] In some embodiments, the compaction density of the negative electrode film layer is 1.0 g / cm³ when the battery cell is at 100% charge. 3 ~1.4g / cm 3 For example, when the battery cell is at 100% charge, the compaction density of the negative electrode film is 1.0 g / cm³. 3 1.05g / cm 3 1.10 g / cm 3 1.15g / cm 3 1.20g / cm3 1.25g / cm 3 1.30g / cm 3 1.35g / cm 3 1.4g / cm 3 Or a range consisting of any two of the above values.

[0093] In some embodiments, when the negative electrode film layer is compacted within the above-mentioned range at 100% charge, the negative electrode active material can be stacked more densely, thereby increasing the energy density of the battery cell. At the same time, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet and also help improve the fast charging performance of the battery cell at low temperatures.

[0094] In some embodiments, the negative electrode current collector in a battery cell refers to a material capable of collecting the negative electrode current of the battery cell, and can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0095] In some embodiments, the negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode film layer also includes a conductive agent and / or a binder. Exemplarily, the conductive agent may be any one or a combination of at least two of carbon black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers. The binder includes any one or a combination of at least two of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), or polymethyl methacrylate (PMMA).

[0096] Positive electrode sheet

[0097] The positive electrode active material can be at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt manganese manganese oxide, and their modified compounds.

[0098] In the embodiments of this application, selecting a suitable positive electrode active material can improve the energy density of a single battery cell.

[0099] In some embodiments, the positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode film layer also includes a positive electrode binder and a positive electrode conductive agent. This application does not impose particular limitations on the types of positive electrode binders and conductive agents. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a terpolymer of tetrafluoroethylene-hexafluoropropylene, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%; the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material layer may include at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0101] When the battery cell is 100% charged, the compaction density of the positive electrode film is 2.4 g / cm³. 3 ~2.65g / cm 3 .

[0102] In the embodiments of this application, the compaction density of the positive electrode film layer of a single battery cell under 100% charge state has a well-known meaning in the art and can be detected using well-known equipment and methods in the art. The detection method is as described above for the compaction density test method of the negative electrode film layer.

[0103] In some embodiments, the compaction density of the positive electrode film layer of a single battery cell at 100% charge is 2.4 g / cm³. 3 ~2.65g / cm 3 For example, when the battery cell is at 100% charge, the compaction density of the positive electrode film is 2.4 g / cm³. 3 2.45g / cm 3 2.5g / cm 3 2.55g / cm 3 2.60g / cm 3 2.65g / cm3 Or, a range consisting of any two of the above values.

[0104] In the embodiments of this application, the compaction density of the positive electrode film is within the above-mentioned range, and the battery cell has a high energy density.

[0105] electrolyte

[0106] In some embodiments, the electrolyte includes a lithium salt, which may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The concentration of the lithium salt is 0.8 M to 1.2 M.

[0107] Separating membrane

[0108] In some embodiments, the battery cell includes a separator disposed between the positive and negative electrodes.

[0109] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0110] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. 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. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0111] Battery device

[0112] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0113] A battery cell is the basic unit that can form a battery module or battery pack; it is an energy storage or release unit. Battery cells can be combined in series, parallel, or mixed connections to form battery modules or battery packs. A battery cell can be cylindrical, square, or any other shape. For example, Figure 3 This is a rigid structure battery cell 5, used as an example.

[0114] A battery cell includes an outer packaging that encapsulates the electrode assembly and non-aqueous electrolyte. The outer packaging can be a rigid shell, such as an aluminum or steel shell. It can also be a flexible package, such as a pouch. The electrode assembly includes the positive electrode, the negative electrode, and a separator.

[0115] Reference Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0116] This application provides a battery device, including a battery cell of the first aspect. The battery device may be at least one of a battery module, a battery pack, and an energy storage device.

[0117] A battery module can be assembled from individual battery cells. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0118] Figure 5 This is battery module 4 as an example. (See reference...) Figure 5 In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0119] A battery pack can be assembled from battery modules. The number of battery modules contained in a battery pack can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0120] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0121] Electrical devices, including battery devices in the second aspect.

[0122] Electrical appliances refer to equipment or appliances that rely on electricity to perform specific functions. They can be household electrical appliances, industrial electrical appliances, commercial electrical appliances, public facility electrical appliances, etc. Specifically, electrical appliances can be mobile phones, laptops, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0123] Figure 8 This is an example of an electrical device. The electrical device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0124] Example

[0125] The following embodiments describe the contents of the embodiments disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosures of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0126] Example 1

[0127] 1) Preparation of negative electrode active materials containing lithium alloy materials

[0128] Lithium oxide and dimethyl zinc were used as lithium and zinc sources, respectively, by atomic deposition technology. The lithium oxide:dimethyl zinc:carbon matrix was prepared in a mass ratio of 1:1:10. The preparation process was as follows: Dimethyl zinc was vaporized at 400℃ in a vacuum reaction chamber, and lithium oxide was vaporized at 400℃. The vaporized dimethyl zinc was introduced into an adsorption reaction chamber at 300℃ at a flow rate of 100 sccm, and the adsorption reaction time was controlled to be 1 min, so that it was adsorbed on the carbon matrix surface. After removing reaction byproducts by purging with N2 at a flow rate of 200 sccm, the vaporized lithium oxide was then introduced into the adsorption reaction chamber at 300℃ at a flow rate of 100 sccm to react with dimethyl zinc, and the adsorption reaction time was controlled to be 1 min. This process was repeated alternately to form a negative electrode active material with a zinc-lithium alloy loaded on the carbon matrix surface.

[0129] The carbon matrix includes artificial graphite and soft carbon. Based on the mass of the carbon matrix, the mass content of soft carbon is 3.5% and the mass content of artificial graphite is 96.5%.

[0130] A zinc-lithium alloy with a thickness of approximately 10 nm was formed on the surface of a carbon matrix to obtain a zinc-lithium alloy-containing anode active material. Based on the mass calculation of the anode active material, the Zn content is 1.50% wt, and the zinc-lithium alloy content is 4.3% wt.

[0131] 2) Preparation of the first negative electrode slurry

[0132] 95 wt% of the above-mentioned negative electrode active material and 2 wt% of the conductive agent superconducting carbon were placed in a stirrer and premixed. Then, 2 wt% of the dispersant sodium carboxymethyl cellulose and 1 wt% of the binder styrene-butadiene rubber were added and mixed. The mixture was dissolved in deionized water and then uniformly mixed with deionized water to prepare the first negative electrode slurry.

[0133] 3) Preparation of the second negative electrode slurry

[0134] 95 wt% of the above-mentioned negative electrode active material and 2 wt% of the conductive agent superconducting carbon were placed in a stirrer and premixed. Then, 1 wt% of the dispersant sodium carboxymethyl cellulose and 2 wt% of the binder styrene-butadiene rubber were added and mixed. The mixture was dissolved in deionized water and then uniformly mixed with deionized water to prepare the second negative electrode slurry.

[0135] 4) Preparation of negative electrode sheet

[0136] Then, the first and second negative electrode slurries were coated onto a 6μm Cu foil using a double-sided, double-cavity coating device. After double-sided coating, the foil was dried, cold-pressed, and slit to obtain a double-sided coated material with a weight of 0.060 mg / 1540.25 cm⁻¹. 2 and 0.900mg / 1540.25cm 2 The negative electrode has a diameter of 140 μm. The specific surface area of ​​the negative electrode active material is 1.35 m². 2 / g, the graphitization degree of the negative electrode active material is 92%, the film resistivity of the negative electrode sheet is 0.2Ω, and the compaction density of the negative electrode film layer under 100% charge is 1.63g / cm³. 3 .

[0137] 5) Preparation of positive electrode sheet

[0138] A positive electrode slurry was prepared by adding 96 wt% lithium iron phosphate (the positive electrode active material), 2 wt% superconducting carbon (the conductive agent), and 2 wt% polyvinylidene fluoride (PVDF) (the positive electrode binder) to N-methylpyrrolidone and stirring. The slurry was then coated onto a 15 μm Al foil. After coating both sides, the foil was dried, cold-pressed, slit, and sheeted to obtain a 170 μm positive electrode sheet. Under 100% charge, the compaction density of the positive electrode film was 2.53 g / cm³. 3 .

[0139] 6) Electrolyte

[0140] The electrolyte contains ethylene carbonate, diethyl carbonate, and dimethyl carbonate mixed in a mass ratio of 1:1:1, and the LiPF6 concentration is 1M.

[0141] 7) Separating membrane

[0142] The separator includes a base membrane, which is a 7μm polyethylene film layer, and the porosity of the separator is 42%.

[0143] 8) Preparation of battery cells

[0144] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell. The bare cell is placed in an outer packaging, injected with prepared electrolyte, and undergoes processes such as sealing, electrolyte injection, formation, and venting to obtain a single battery cell.

[0145] Example 2-3

[0146] The difference between Examples 2-3 and Example 1 lies in the thickness of the lithium alloy material and the mass content of non-lithium elements in the negative electrode active material. See Table 1 for specific parameters.

[0147] Examples 4-6

[0148] Examples 4-6 differ from Example 1 in the lithium alloy material used, the lithium-ion diffusion coefficient of the negative electrode active material, and the mass content of non-lithium elements in the negative electrode active material. Specific parameters are shown in Table 1.

[0149] Comparative Examples 1-3

[0150] The difference between Comparative Example 1 and Example 1 is that there is no lithium alloy material in the negative electrode active material. See Table 1 for specific parameters. The difference between Comparative Examples 2 and 3 and Example 1 is that the lithium alloy materials used are different.

[0151] Except for the parameters in Table 1, the battery cells were obtained according to the method described in Example 1.

[0152] Table 1

[0153]

[0154]

[0155] In the table, "—" represents data that is not included.

[0156] The scanning electron microscope (SEM) images of the negative electrode active materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown, the results indicate that the surface of the negative electrode active material in Comparative Example 1 is rougher than that in Example 1, with obvious adhered substances. Figure 2 According to XPS test results, the material adhering to the surface of the negative electrode active material described in this application is a lithium alloy material with zinc as the non-lithium element.

[0157] Performance testing

[0158] 1. Charging time test of individual battery cells at -10℃ from 20% SOC to 40% SOC

[0159] Voltage calibration:

[0160] 1) In the examples or comparative examples, the positive electrode, negative electrode, separator, and electrolyte are used to prepare a stacked three-electrode battery, which is then left to stand at 25°C for 30 minutes.

[0161] 2) At 25℃, charge the battery cell to the upper limit of the charging voltage of 3.8V at 0.33C, and then continue to charge at the upper limit of the charging voltage until the current is 0.05C, and then charge to stop (where C represents the rated capacity of the battery cell). Let it stand at 25℃ for 1 hour.

[0162] 3) Discharge the battery cell to the cutoff voltage of 2.0V at 0.33C at 25℃, record the total discharge capacity C0 of the battery cell, and let it stand at 25℃ for 1 hour.

[0163] -10℃ charging test:

[0164] 1) Prepare a stacked three-electrode battery using the positive electrode, negative electrode, separator, and electrolyte from the examples or comparative examples, and let it stand for 30 minutes;

[0165] 2) At 25℃, discharge with 0.33C0 DC to the cutoff voltage of 2.0V, at which point the state of charge (SOC) is 0%.

[0166] 3) Let it stand at -10℃ for 1 hour, then charge it with a constant current of 1.5C0 until the negative electrode potential is 0mV. Read the capacity C1 at this time, which corresponds to (C1 / C0)SOC.

[0167] 4) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 1.0C0 until the negative electrode potential is 0mV. Read the capacity C2 at this time, which corresponds to (C2 / C0)SOC.

[0168] 5) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.8C0 until the negative electrode potential is 0mV. Read the capacity C3 at this time, which corresponds to (C3 / C0)SOC.

[0169] 6) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.6C0 until the negative electrode potential is 0mV. Read the capacity C4 at this time, which corresponds to (C4 / C0)SOC.

[0170] 7) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.5C0 until the negative electrode potential is 0mV. Read the capacity C5 at this time, which corresponds to (C5 / C0)SOC.

[0171] 8) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.4C0 until the negative electrode potential is 0mV. Read the capacity C6 at this time, which corresponds to (C6 / C0)SOC.

[0172] 9) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.35C0 until the negative electrode potential is 0mV. Read the capacity C7 at this time, which corresponds to (C7 / C0)SOC.

[0173] 10) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.30C0 until the negative electrode potential is 0mV. Read the capacity C8 at this time, which corresponds to (C8 / C0)SOC.

[0174] 11) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.25C0 until the negative electrode potential is 0mV. Read the capacity C9 at this time, which corresponds to (C9 / C0)SOC.

[0175] 12) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.20C0 until the negative electrode potential is 0mV. Read the capacity C10 at this time, which corresponds to (C10 / C0)SOC.

[0176] 13) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.15C0 until the negative electrode potential is 0mV. Read the capacity C11 at this time, which corresponds to (C11 / C0)SOC.

[0177] 14) Let it stand at -10℃ for 5 minutes, then charge it with a constant current of 0.10C0 until the negative electrode potential is 0mV. Read the capacity C12 (C12=C0) at this time, which corresponds to 100% SOC.

[0178] The required charging time is obtained by summing the total charging time from 20% SOC to 40% SOC at -10℃. A shorter charging time indicates better fast-charging performance of the battery cells at low temperatures.

[0179] 2. 60℃ Cyclic Performance Test:

[0180] At 60℃, the battery cell is charged to 3.8V with a constant current of 1C, then charged to 0.05C with a constant voltage of 3.8V, left to rest for 30 minutes, and then discharged to 2V with 1C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated, and the discharge capacity Cn of the battery cell after the nth cycle is recorded. The capacity retention rate of the battery cell after each cycle is: Pn = (Cn / C0) × 100%. In this test, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2, ..., the 400th cycle corresponds to n = 400. The higher the capacity retention rate, the better the cycle performance of the battery cell.

[0181] Analysis of test results for each embodiment and comparative example

[0182] Each example and comparative example was prepared according to the above method, and various performance parameters were measured. The analysis results are shown in Table 1.

[0183] Analysis of Examples 1-6 and Comparative Examples 1-3 shows that Examples 1-6 of this application improve the negative electrode active material by introducing a suitable lithium alloy material on the surface of the carbon matrix, resulting in a lithium-ion diffusion coefficient of 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1 The negative electrode active material can improve the fast charging performance of battery cells at low temperatures, as well as the cycle performance and lifespan of battery cells.

[0184] Analysis of Examples 1 and 4-6 shows that selecting a suitable lithium alloy material can improve the fast charging performance of battery cells at low temperatures, as well as improve the cycle performance of battery cells, thereby extending the service life of battery cells.

[0185] Analysis of Examples 1-3 shows that controlling the thickness of lithium alloy materials between 1nm and 100nm can improve the fast charging performance of battery cells at low temperatures, while also taking into account the cycle performance of battery cells and improving their service life.

Claims

1. A battery cell, characterized in that, It includes a positive electrode, a negative electrode, and a separator membrane located between the positive electrode and the negative electrode, wherein, The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material; The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes a carbon matrix and a lithium alloy material located on at least a portion of the surface of the carbon matrix. The lithium-ion diffusion coefficient of the negative electrode active material is 10. -11 cm 2 s -1 ~10 -7 cm 2 s -1 .

2. The battery cell according to any one of claims 1, characterized in that, The lithium alloy material includes non-lithium elements, which include at least one of Zn, Mg, Si, Al, Cu, Ag, Sb, Cr, Pt, Zr, Ca, and Ti.

3. The battery cell according to any one of claims 1-2, characterized in that, The non-lithium element includes at least one of Zn, Mg and Al.

4. The battery cell according to claim 2 or 3, characterized in that, Based on the mass of the negative electrode active material, the mass content of the non-lithium element is 0.1% to 5%.

5. The battery cell according to any one of claims 1-4, characterized in that, Based on the mass of the negative electrode active material, the mass content of lithium alloy material in the negative electrode active material is 0.1% to 15%, and can be selected as 0.5% to 10%.

6. The battery cell according to any one of claims 1-5, characterized in that, The thickness of the lithium alloy material on the carbon matrix surface is 1 nm to 100 nm.

7. The battery cell according to any one of claims 1-6, characterized in that, The carbon matrix includes graphite materials, which include at least one of artificial graphite and natural graphite.

8. The battery cell according to any one of claims 1-7, characterized in that, The carbon matrix includes amorphous carbon materials, which include soft carbon and / or hard carbon.

9. The battery cell according to claim 8, characterized in that, The amorphous carbon material is located on at least a portion of the surface of the graphite material.

10. The battery cell according to any one of claims 1-9, characterized in that, The volume average particle size Dv50 of the negative electrode active material is 1μm to 35μm, and can be selected as 4μm to 15μm.

11. The battery cell according to any one of claims 1-10, characterized in that, The specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g~2.5m 2 / g.

12. The battery cell according to any one of claims 1-11, characterized in that, The graphitization degree of the negative electrode active material is 90% to 98%.

13. The battery cell according to any one of claims 1-12, characterized in that, The film resistance of the negative electrode is 0.002Ω to 0.006Ω.

14. The battery cell according to any one of claims 1-13, characterized in that, When the battery cell is 100% charged, the compaction density of the negative electrode film is 1.0 g / cm³. 3 ~1.4g / cm 3 .

15. The battery cell according to any one of claims 1-14, characterized in that, The positive electrode active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and their modified compounds.

16. The battery cell according to any one of claims 1-15, characterized in that, When the battery cell is 100% charged, the compaction density of the positive electrode film is 2.4 g / cm³. 3 ~2.65g / cm 3 .

17. A battery device comprising a battery cell according to any one of claims 1-16.

18. An electrical device comprising the battery device of claim 17.

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