Negative electrode material, secondary battery, and electrical device

Abstract

The present application belongs to the field of battery materials, and discloses a negative electrode material, a secondary battery, and an electrical device. The negative electrode material comprises: a base material, having a pore structure; and a filling material, at least distributed in pores of the base material. The base material comprises a carbon material. The filling material comprises titanium lithium oxide. The carbon material and the titanium lithium oxide each comprise fluorine.

Description

Negative electrode materials, secondary batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 21, 2024, with application number 202410330409.3 and entitled “Negative Electrode Materials, Secondary Batteries and Electrical Equipment,” the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of battery materials, and specifically relates to a negative electrode material, a secondary battery and an electrical device. Background Art

[0003] With the development of science and technology, the application of batteries is becoming more and more extensive, and thus more and more attention is paid to the research and development of batteries. Usually, when developing negative electrode materials for batteries, graphite is modified by nano-sizing or carbon coating to form negative electrode materials, namely graphite negative electrodes. However, the low lithium insertion potential of the graphite negative electrode, the consumption of electrolyte due to the formation of SEI film, and the volume expansion of graphite after multiple cycles cause its safety performance and cycle performance to deteriorate rapidly. Lithium titanate has a higher lithium deposition potential, almost no volume change during the charge and discharge process, and no passivation layer or SEI film is formed, making its cycle performance almost 10 times that of the graphite negative electrode. However, due to its poor conductivity, low lithium ion mobility and high electrolyte reaction activity, lithium titanate has poor rate performance and stability. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a negative electrode material, a secondary battery, and an electrical device, which at least solve the problem of poor rate performance and stability of lithium titanate.

[0005] In a first aspect, an embodiment of the present application provides a negative electrode material, comprising:

[0006] a matrix material having a porous structure;

[0007] A filling material, distributed at least in the pores of the matrix material;

[0008] The matrix material includes a carbon material, the filling material includes titanium lithium oxide, and both the carbon material and the titanium lithium oxide contain fluorine element.

[0009] Optionally, the mass content of the fluorine element in the negative electrode material is A, satisfying: 1%≤A≤5%.

[0010] Optionally, the average pore size of the pore structure is Z, satisfying: Z≥5nm.

[0011] Optionally, the negative electrode material satisfies: V1 / V2>0.8; V1 represents the volume of pores with a pore diameter in the range of 5 nm-200 nm in the negative electrode material; and V2 represents the total pore volume of the negative electrode material.

[0012] Optionally, the matrix material is in the shape of nanowires, and the diameter of the matrix material is L1 nm, satisfying: 200≤L1≤320; and / or the average particle size of the titanium lithium oxide is L2 nm, satisfying: 20≤L2≤50.

[0013] Optionally, the mass of the carbon material is M3, and the mass of the titanium lithium oxide is M4, satisfying: 0.7≤M1 / M2≤1.2.

[0014] Optionally, the content of fluorine in the carbon material is C1, and the content of fluorine in the titanium lithium oxide is C2, and C1:C2 satisfies (0.19-0.35):1.

[0015] Optionally, the specific surface area of ​​the negative electrode material is 70 cm 2 / g~90cm 2 / g.

[0016] Optionally, the following is satisfied: 2%≤A≤4%.

[0017] Optionally, it satisfies: 5nm≤Z≤300nm.

[0018] Optionally, the following is satisfied: 0.8≤M1 / M2≤1.0.

[0019] In a second aspect, an embodiment of the present application provides a secondary battery, the secondary battery comprising a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprising the negative electrode material described in any one of the first aspects above, the lithium ion diffusion coefficient of the secondary battery being 5*10 -13 ~8*10 -13 .

[0020] Optionally, the ohmic resistance of the secondary battery is 4.1-4.9Ω.

[0021] Optionally, the charge transfer resistance of the secondary battery is 52-69Ω.

[0022] In a third aspect, an embodiment of the present application provides an electric device, which includes the secondary battery described in the second aspect above, and the secondary battery serves as a power supply for the electric device.

[0023] In an embodiment of the present application, the base material has a pore structure, and the filling material is at least distributed in the pores of the base material, and the base material includes a carbon material, and the filling material includes titanium lithium oxide, and both the carbon material and the titanium lithium oxide contain fluorine. The pore structure can not only increase the specific surface area of ​​the negative electrode material and increase the reactive sites, but also enable the electrolyte to be fully infiltrated, which is beneficial for the diffusion of lithium ions between the base materials. At the same time, fluorine doping is performed. When the negative electrode material is formed, the fluorine element can not only replace part of the oxygen element in the titanium lithium oxide but also enter the interlayer spacing of the carbon material, thereby promoting the rearrangement of electrons at the interface of the negative electrode material, reducing the resistance to the insertion and extraction of lithium ions, and increasing the migration rate of lithium ions inside the base material, thereby reducing the charge transfer resistance (Rct) of the negative electrode material and improving the rate performance of the negative electrode material. The intervention of the carbon material can reduce the effective contact area between the titanium lithium oxide and the electrolyte, effectively slowing down the chemical reaction rate between the titanium lithium oxide and the electrolyte, thereby improving the stability of the negative electrode material. That is, in the embodiments of the present application, the conductivity of the titanium lithium oxide is improved by introducing a filler material (including titanium lithium oxide) into a base material (including a carbon material). While constructing a porous structure on the base, fluorine is incorporated into the negative electrode material, allowing lithium ions to diffuse and migrate rapidly within the material. Furthermore, the carbon material reduces the contact points between the titanium lithium oxide and the electrolyte, thereby improving the rate performance and stability of the negative electrode material.

[0024] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] FIG1 is a schematic diagram showing a negative electrode material for electrospun lithium titanate without carbonization provided in an embodiment of the present application;

[0027] FIG2 is a schematic diagram of a carbonized and ground negative electrode material provided in an embodiment of the present application;

[0028] FIG3 is a schematic diagram of a carbonized and ground negative electrode material under a high-magnification microscope provided in an embodiment of the present application. Specific embodiments

[0029] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly refer to one or more of the features. Throughout the description of this application, unless otherwise specified, "plurality" means two or more. Furthermore, "and / or" in the specification and claims refers to at least one of the connected entities, and the character " / " generally indicates an "or" relationship between the connected entities.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0031] As shown in Figures 1 to 3, the negative electrode material includes: a base material having a porous structure; a filling material distributed at least in the pores of the base material; the base material includes a carbon material, the filling material includes titanium lithium oxide, and both the carbon material and the titanium lithium oxide contain fluorine.

[0032] In an embodiment of the present application, the base material has a pore structure, and the filling material is at least distributed in the pores of the base material, and the base material includes a carbon material, and the filling material includes titanium lithium oxide, and both the carbon material and the titanium lithium oxide contain fluorine. The pore structure can not only increase the specific surface area of ​​the negative electrode material and increase the reactive sites, but also enable the electrolyte to be fully infiltrated, which is beneficial for the diffusion of lithium ions between the base materials. At the same time, fluorine doping is performed. When the negative electrode material is formed, the fluorine element can not only replace part of the oxygen element in the titanium lithium oxide but also enter the interlayer spacing of the carbon material, thereby promoting the rearrangement of electrons at the interface of the negative electrode material, reducing the resistance to the insertion and extraction of lithium ions, and increasing the migration rate of lithium ions inside the base material, thereby reducing the charge transfer resistance (Rct) of the negative electrode material and improving the rate performance of the negative electrode material. The intervention of the carbon material can reduce the effective contact area between the titanium lithium oxide and the electrolyte, effectively slowing down the chemical reaction rate between the titanium lithium oxide and the electrolyte, thereby improving the stability of the negative electrode material. That is, in the embodiments of the present application, the conductivity of the titanium lithium oxide is improved by introducing a filler material (including titanium lithium oxide) into a base material (including a carbon material). While constructing a porous structure on the base, fluorine is incorporated into the negative electrode material, allowing lithium ions to diffuse and migrate rapidly within the material, thereby improving the rate performance and stability of the negative electrode material.

[0033] It should be noted that in the embodiments of the present application, the pore structure can be located on the surface of the base material, that is, the surface of the base material has a pore structure. In addition, the pore structure can be a hole structure, that is, holes are formed on the surface of the base material, and the holes form the pore structure.

[0034] In addition, in the embodiment of the present application, titanium lithium oxide is distributed in the pores of the matrix material, that is, titanium lithium oxide is distributed in the pores of the carbon material, which is equivalent to the carbon material coating titanium lithium oxide, thereby improving the conductivity of the negative electrode material.

[0035] In addition, in the embodiments of the present application, both the carbon material and the titanium lithium oxide contain fluorine, and the fluorine is evenly distributed in the negative electrode material. Fluorine doping can effectively reduce the resistance to the insertion and extraction of lithium ions and increase the migration rate of lithium ions.

[0036] In addition, in the embodiment of the present application, the titanium lithium oxide can be lithium titanate. Of course, the titanium lithium oxide can also be other types, which is not limited in the embodiment of the present application. Among them, when the titanium lithium oxide is lithium titanate, lithium titanate belongs to a face-centered cubic spinel structure, Fd-3m space lattice group, and the unit cell parameter is 0.863nm, which can provide a three-dimensional ion transmission channel. At the same time, lithium titanate has a high lithium deposition potential, almost no volume change during the charge and discharge process, and does not form a passivation layer, SEI film and other characteristics. This can further improve the rate performance and stability of the negative electrode material.

[0037] In addition, in some embodiments, the mass content of the fluorine element in the negative electrode material is A, satisfying the following: 1% ≤ A ≤ 5%. When the mass content of the fluorine element in the negative electrode material is within the above range, it is equivalent to a mass content of 1%-5% of the doped fluorine element. This can ensure that the fluorine content in the formed negative electrode material is moderate, ensuring that the introduction of fluorine element can effectively reduce the resistance to lithium insertion and extraction, increase the migration rate of lithium ions, reduce the charge transfer resistance, and improve the rate performance.

[0038] It should be noted that the mass content of fluorine element in the negative electrode material can be any value between 1% and 5%. For example, the mass content of fluorine element in the negative electrode material can be any one of 1%, 2%, 3%, 4%, 5% or any two of the range values.

[0039] In addition, in the embodiments of the present application, the fluorine content in the carbon material is C1, and the fluorine content in the titanium lithium oxide is C2, and the C1:C2 ratio satisfies (0.19-0.35):1. When the fluorine content in the carbon material and the fluorine content in the titanium lithium oxide are within the above ranges, the ratio of fluorine in the filler material to the fluorine in the matrix material can be optimized, achieving better electrical performance.

[0040] It should be noted that the ratio of the fluorine content in the carbon material to the fluorine content in the titanium lithium oxide can be any value in the range of (0.19 to 0.35):1. For example, the ratio of the fluorine content in the carbon material to the fluorine content in the titanium lithium oxide can be any value in the range of 0.19:1, 0.20:1, 0.22:1, 0.25:1, 0.27:1, 0.29:1, 0.31:1, 0.33:1, or 0.35:1. This is not limited in the present embodiment.

[0041] In addition, in the embodiment of the present application, the specific surface area of ​​the negative electrode material is 70 cm 2 / g~90cm 2 When the specific surface area of ​​the negative electrode material is within the above range, the specific surface area of ​​the negative electrode material can be sufficiently large, so that when the negative electrode material is applied to a battery, the negative electrode material has a larger contact area with the electrolyte.

[0042] It should be noted that the specific surface area of ​​the negative electrode material can be 70 cm 2 / g~90cm 2 / g. For example, the specific surface area of ​​the negative electrode material is 70cm 2 / g、75cm 2 / g、78cm 2 / g、80cm 2 / g、82cm 2 / g、85cm 2 / g, 87cm 2 / g、90cm 2 / g or both.

[0043] In addition, in some embodiments, the average pore size of the negative electrode material is Z, satisfying: Z ≥ 5 nm. In this embodiment, the average pore size is greater than 5 nm, so that these pores can serve as ion reaction channels, facilitating the insertion and extraction of lithium ions. In some embodiments, the average pore size of the negative electrode material can be 5 to 300 nm, for example, it can be in the range of one or any two of 5 nm, 50 nm, 100 nm, 180 nm, 200 nm, 260 nm, and 300 nm.

[0044] In the examples of this application, the negative electrode material satisfies the following ratio: V1 / V2 > 0.8, where V1 represents the volume of pores in the negative electrode material with a pore diameter range of 5nm-200nm, and V2 represents the total pore volume of the negative electrode material. When V1 / V2 is within this range, it indicates that the negative electrode material has a relatively large pore volume with pores in the 5nm-200nm range. The pores in the 5nm-200nm range represent mesoporous structures. These abundant mesoporous structures can serve as ion channels for the reaction, shortening ion transport distances and accelerating reaction kinetics.

[0045] In some embodiments, the matrix material is linear in shape, and the diameter of the matrix material is L1 nm, satisfying the following: 200 ≤ L1 ≤ 320. When L1 is within the above range, both electrolyte wetting and compaction density of the negative electrode sheet are achieved. In the embodiments of the present application, the titanium lithium oxide is located within the nanowire structure, which is equivalent to the titanium lithium oxide being confined within the nanowire structure of 200 nm to 320 nm.

[0046] It should be noted that the diameter of the base material can be any value between 200 nm and 320 nm, for example, the diameter of the base material can be any value between 200 nm, 230 nm, 260 nm, 280 nm, 300 nm, and 320 nm. This embodiment of the present application does not limit this.

[0047] In another embodiment of the present application, the average particle size of the titanium lithium oxide is L2 nm, satisfying: 20≤L2≤50. When L2 is within the above range, the particle size of the titanium lithium oxide is moderate, which is conducive to uniform distribution of the titanium lithium oxide in the substrate material.

[0048] It should be noted that the average particle size of the titanium lithium oxide can be any one of 20 nm to 50 nm, for example, the average particle size of the titanium lithium oxide can be any one of 20 nm, 30 nm, 40 nm, and 50 nm. This embodiment of the present application does not limit this.

[0049] In addition, in some embodiments, in the negative electrode material, the mass of the carbon material is M1, and the mass of the titanium lithium oxide is M2, satisfying the following: 0.7≤M1 / M2≤1.2. When the value of M1 / M2 is within the above range, the ratio of the carbon material to the titanium lithium oxide can be moderate, which is beneficial for improving the cycle stability of the negative electrode material while taking into account the mass-to-energy ratio of the material.

[0050] It should be noted that M1 / M2 can be any value between 0.7 and 1.2. For example, M1 / M2 can be any one or any two of 0.7, 0.8, 0.9, 1.0, 1.1, and 1.2. This is not limited in the present embodiment.

[0051] The present application also provides a secondary battery comprising a positive electrode plate and a negative electrode plate, wherein the negative electrode plate comprises the negative electrode material of any of the above embodiments, and the lithium ion diffusion coefficient of the secondary battery is 5*10 -13 ~8*10 -13 The lithium ion diffusion coefficient indicates the rate of lithium ion insertion and extraction in a battery. The lithium ion diffusion coefficient of the secondary battery of this embodiment is within the above range, indicating that the lithium ions in the secondary battery have excellent diffusion performance, which is beneficial to improving the rate performance of the secondary battery.

[0052] In some embodiments, the ohmic resistance of the secondary battery is 4.1 to 4.9 Ω, for example, it can be a range of one or any two of 4.1 Ω, 4.3 Ω, 4.5 Ω, 4.7 Ω, and 4.9 Ω. In some embodiments, the charge transfer resistance of the secondary battery is 52 to 69 Ω, for example, it can be a range of one or any two of 52 Ω, 55 Ω, 58 Ω, 65 Ω, and 69 Ω. The secondary battery of the present application adopts the above-mentioned negative electrode material. Since the above-mentioned negative electrode material has excellent electrical conductivity, the impedance of the secondary battery is reduced, which is conducive to improving the rate performance of the secondary battery.

[0053] The present application also provides an electrical device, which includes the above-mentioned secondary battery. The following is a detailed description of the method for making the negative electrode material provided in the present application. The specific steps can be as follows:

[0054] Step 101: Add a fluorine-containing organic polymer into an organic solvent to form a fluorine-containing organic solution.

[0055] The organic solvent may include at least one of N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, and acetone. For example, the organic solvent may be N-methylpyrrolidone. For another example, the organic solvent may be dimethylformamide. For another example, the organic solvent may be a mixture of dimethylformamide and dimethyl sulfoxide.

[0056] In addition, the fluorine-containing organic polymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, and polychlorotrifluoroethylene-vinylidene fluoride copolymer. For example, the fluorine-containing organic polymer may be polyvinylidene fluoride, or for another example, the fluorine-containing organic polymer may be polyvinyl fluoride, or the fluorine-containing organic polymer may be a mixture of polytetrafluoroethylene and polyvinyl fluoride.

[0057] In addition, the mass ratio of the fluorinated organic polymer to the organic solvent is 0.05 to 0.3. That is, when adding the fluorinated organic polymer to the organic solvent, the mass of the organic solvent can be first determined, and then the mass of the fluorinated organic polymer can be determined so that the mass ratio of the fluorinated organic polymer to the organic solvent satisfies 0.05 to 0.3. The fluorinated organic polymer is then added to the organic solvent to form a fluorinated organic solution. That is, in step 101, the fluorinated organic polymer is directly added to the organic solvent, so that the fluorinated organic polymer dissolves in the organic solvent to form a fluorinated organic solution, and the mass ratio of the fluorinated organic polymer to the organic solvent satisfies 0.05 to 0.3.

[0058] Step 102: Add a lithium-containing compound and a titanium-containing compound to the fluorine-containing organic solution and stir evenly to form a slurry.

[0059] The lithium-containing compound may include at least one of LiOH·H2O, LiNO3, and Li2CO3. For example, the lithium-containing compound is LiNO3, another example, the lithium-containing compound is Li2CO3, and another example, the lithium-containing compound is a mixture of LiNO3 and LiOH·H2O. The titanium-containing compound may include at least one of tetrabutyl titanate, titanium isopropoxide, and titanium dioxide. For example, the titanium-containing compound may include tetrabutyl titanate, another example, the titanium-containing compound may include titanium isopropoxide, and another example, the titanium-containing compound may include a mixture of titanium isopropoxide and titanium dioxide.

[0060] In addition, the mass ratio of the lithium-containing compound to the titanium-containing compound is 0.89 to 1.8. That is, when adding the lithium-containing compound and the titanium-containing compound to the fluorine-containing organic solution, the mass of the lithium-containing compound can be determined first, and then the mass of the titanium-containing compound can be determined, so that the mass ratio of the lithium-containing compound to the titanium-containing compound meets 0.89 to 1.8, and then the lithium-containing compound and the titanium-containing compound are added to the fluorine-containing organic solution to form a mixed solution.

[0061] It should be noted that after adding the lithium-containing compound and the titanium-containing compound to the fluorine-containing organic solution, they can be ultrasonically dispersed and then stirred to form a slurry. That is, after adding the lithium-containing compound and the titanium-containing compound to the fluorine-containing organic solution, the lithium-containing compound and the titanium-containing compound are fully dispersed in the fluorine-containing organic solution through an ultrasonic dispersion process, and then stirred to ensure that the lithium-containing compound and the titanium-containing compound are evenly dispersed in the fluorine-containing organic solution.

[0062] Step 103: placing the mixed solution into an injector, and spraying the mixed solution onto a metal foil receiver through the injector under an electric field of a preset voltage, so that the mixed slurry forms a nanowire structure on the surface of the metal foil to obtain a negative electrode material precursor.

[0063] Among them, the preset voltage can be any value between 13KV and 20KV, which is equivalent to placing the mixed slurry into the injector, placing the injector under an electric field between 13KV and 20KV, and spraying the mixed slurry onto the metal foil through the injector, that is, the mixed solution is electrostatically spun under an electric field between 13KV and 20KV, so that the mixed solution forms a nanowire structure on the surface of the metal foil, and the nanowire structure is the precursor of the negative electrode material.

[0064] It should be noted that the material of the metal foil can be a material that does not react with the mixed solution, for example, the material of the metal foil is aluminum. The specific material of the metal foil is not limited in this embodiment of the application.

[0065] Step 104: peeling the negative electrode material precursor from the surface of the metal foil, carbonizing it at a high temperature, and grinding it to obtain the negative electrode material.

[0066] Among them, the negative electrode material precursor is carbonized. During carbonization, the escape of gas and water molecules causes a pore structure to be formed in the nanowire structure, that is, the matrix material has a pore structure. In addition, the fluorine element in the fluorine-containing polymer can be doped into the negative electrode material during the carbonization process, thereby increasing the migration rate of lithium ions in the matrix material, thereby reducing the charge transfer resistance of the negative electrode material.

[0067] In addition, before carbonizing the negative electrode material precursor, the negative electrode material precursor is first dried to remove the solvent; then the dried negative electrode material precursor is placed in a tube furnace and a protective gas is introduced to perform carbonization.

[0068] The protective gas may be one or both of nitrogen and argon. In addition, after the dried negative electrode material precursor is placed in the tube furnace, the tube furnace is heated at a constant heating rate and carbonized at a predetermined temperature.

[0069] In the embodiment of the present application, the constant heating rate can be any value in the range of 2°C / min to 5°C / min, for example, the constant heating rate can be any value in the range of 2°C / min, 3°C / min, 4°C / min, or 5°C / min. In addition, the temperature in the tube furnace ranges from 700°C to 900°C.

[0070] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0071] Example 1:

[0072] a. Add 1 g of polyvinylidene fluoride to 10 g of dimethylformamide and mix well to obtain a fluorine-containing organic solution.

[0073] b. 200mg LiOH, 200mgLi2CO3 and 300mgTiO2 were added to the fluorine-containing organic solution and ultrasonically dispersed, and stirred for 12h to obtain a uniformly mixed slurry.

[0074] c. The mixed solution was transferred to an ejector and electrospun at a voltage of 13 kV to obtain a negative electrode material precursor.

[0075] d. After drying the negative electrode material precursor at 60°C, the precursor was placed in a tubular furnace with N2 as the protective gas and carbonized at 700°C for 2 hours at a heating rate of 2°C / min. After cooling, the negative electrode material was obtained. The fluorine content of the negative electrode material was 3.5% by mass, the average pore size was 20 nm, the V1 / V2 was 0.85, the L1 was 245 nm, the M1 / M2 was 0.9, the C1:C2 was 0.25:1, the L2 was 30 nm, and the specific surface area of ​​the negative electrode material was 73 cm 2 / g.

[0076] Preparation of secondary batteries, wherein during preparation, the negative electrode material, acetylene black, polyvinylidene fluoride prepared above can be mixed with NMP to form a uniform slurry, and aluminum foil is used as the current collector and the negative electrode sheet is obtained by single-sided coating and roller pressing. The mass ratio of active material, acetylene black, and polyvinylidene fluoride is 8:1:1. The positive electrode slurry includes three parts: active material, binder, and conductive agent. The active material is lithium manganese oxide, the binder is polyvinylidene fluoride, and the conductive agent is SUPER-P. The active material, conductive agent, and binder are mixed in a mass ratio of 8:1:1 and added to NMP for homogenization to form a slurry. Aluminum foil is used as the current collector and the positive electrode sheet is obtained by single-sided coating and roller pressing. The positive and negative electrode sheets were cut into discs with a diameter of about 12 mm and assembled in the order of positive electrode sheet-diaphragm-negative electrode sheet. LiPF6 was added as the electrolyte to a mixture of ethylene ester (EC) and dimethyl carbonate (DMC) with a volume ratio of 1:1. The concentration of LiPF6 in the electrolyte was 1 mol / L. Then, the cells were assembled into CR2032 batteries in a glove box filled with inert gas. The separator was glass fiber. After assembly, the cells were left to stand at room temperature for 24 hours to obtain a secondary battery.

[0077] Examples 2-23 and Comparative Example 1 are different from Example 1 in that the preparation parameters of the negative electrode material are adjusted to obtain negative electrode materials with different characteristics, as shown in Table 1.

[0078] In Examples 2-9, negative electrode materials with different specific surface areas BET, average pore diameters Z, and pore volume ratios V1 / V2 can be obtained by adjusting the carbonization temperature.

[0079] In Examples 10-12, negative electrode materials with different base material diameters L1 can be obtained by adjusting the voltage of the injector.

[0080] In Examples 13-18, by adjusting the amount of polyvinylidene fluoride added in step a, negative electrode materials with different fluorine content A and negative electrode materials with different ratios of fluorine content in the carbon material to fluorine content in the lithium titanium oxide (C1 / C2) can be obtained;

[0081] In Examples 19-21, negative electrode materials with different ratios of the mass of the carbon material to the mass of the titanium lithium oxide (M1 / M2) can be obtained by adjusting the amounts of the titanium source and the lithium source.

[0082] In Examples 22-23, the negative electrode material of titanium lithium oxide (L2) with different particle sizes can be obtained by adjusting the heating rate.

[0083] Comparative Example 1 is different from Example 1 in that Comparative Example 1 does not include step a, and 200 mg of LiOH, 200 mg of Li2CO3 and 300 mg of TiO2 are directly mixed and sintered in a tube furnace to obtain a negative electrode material.

[0084] Table 1

[0085] The secondary batteries prepared in Examples 1-23 and Comparative Example 1 were subjected to electrochemical tests. The test results are shown in Table 2. The test results for each item are as follows:

[0086] 1) Cyclic capacity retention rate test method: use 0.1A g -1 The battery was fully charged to 2.9 V at a constant current and constant voltage of 0.1 A g -1 、1A g -1 The battery is discharged to 2V at a current density of 0.1A g -1 、1A g -1 The charge and discharge cycle test was carried out at a current density of 1000, and the discharge capacity at the 500th cycle was recorded as C n The capacity retention process of the battery after 500 cycles is calculated, and the capacity retention rate = C n / C0*100%

[0087] 2) The reversible specific capacity test method is: use 0.1A g -1 The battery was fully charged to 2.9 V at a constant current and constant voltage of 0.1 A g -1 、1A g -1 The battery is discharged to 2V at a current density of 1000 nm, and the initial capacity is recorded as C1. Reversible specific capacity = C1 / m, where m represents the mass of the active material in the negative electrode.

[0088] 3) R s (ohmic resistance), R ct The charge transfer resistance (CTR) was measured by performing an electrochemical impedance spectroscopy (EIS) test on an electrochemical workstation using the following parameters: an excitation voltage of 10 mV and a frequency range of 100 to 0.0 Hz.

[0089] 4) Lithium ion diffusion coefficient The testing method is: using an electrochemical workstation to test and obtain the lithium ion diffusion coefficient.

[0090] Table 2

[0091] It can be seen from Table 1 and Table 2 above that the solution of the embodiment of the present application can effectively improve the rate performance and cycle performance.

[0092] Among them, the excellent rate performance of the negative electrode material is attributed to its large specific surface area, which can provide more active sites and a rich pore structure, which is conducive to the diffusion of lithium ions. At the same time, the carbon nanowire structure avoids direct contact between lithium titanate and the electrolyte, and fluorine doping promotes the discharge of interface electrons, improves the lithium ion insertion and extraction power, and enhances the cycle stability and rate performance.

[0093] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0094] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A negative electrode material, wherein include: a matrix material having a porous structure; A filling material, distributed at least in the pores of the matrix material; The matrix material includes a carbon material, the filling material includes titanium lithium oxide, and both the carbon material and the titanium lithium oxide contain fluorine element.

2. The negative electrode material according to claim 2, wherein The mass content of the fluorine element in the negative electrode material is A, and satisfies the following: 1%≤A≤5%.

3. The negative electrode material according to claim 1, wherein The average pore size of the negative electrode material is Z, which satisfies: Z≥5nm.

4. The negative electrode material according to claim 3, wherein V1 / V2>0.8 is satisfied; V1 represents the pore volume in the negative electrode material with a pore diameter in the range of 5 nm to 200 nm; V2 represents the total pore volume of the negative electrode material.

5. The negative electrode material according to claim 1, wherein The shape of the matrix material is nanowire-shaped, and the diameter of the matrix material is L1 nm, satisfying: 200≤L1≤320.

6. The negative electrode material according to any one of claims 1 to 5, wherein The average particle size of the titanium lithium oxide is L2 nm, satisfying the following: 20≤L2≤50.

7. The negative electrode material according to claim 1, wherein The mass of the carbon material is M1, and the mass of the titanium lithium oxide is M2, which satisfies the following: 0.7≤M1 / M2≤1.

2.

8. The negative electrode material according to claim 1, wherein The content of fluorine in the carbon material is C1, and the content of fluorine in the titanium lithium oxide is C2, and C1:C2 satisfies (0.19-0.35):

1.

9. The negative electrode material according to claim 1, wherein The specific surface area of ​​the negative electrode material is 70 cm 2 / g~90cm 2 / g.

10. The negative electrode material according to claim 2, wherein Meet: 2%≤A≤4%.

11. The negative electrode material according to claim 3, wherein Satisfies: 5nm≤Z≤300nm.

12. The negative electrode material according to claim 7, wherein Satisfies: 0.8≤M1 / M2≤1.

0.

13. A secondary battery, wherein: The secondary battery comprises a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet comprises the negative electrode material according to any one of claims 1 to 12, and the lithium ion diffusion coefficient of the secondary battery is 5*10 -13 ~8*10 -13 .

14. The secondary battery according to claim 13, wherein The ohmic resistance of the secondary battery is 4.1-4.9Ω.

15. The secondary battery according to claim 13 or 14, wherein The charge transfer resistance of the secondary battery is 52-69Ω.

16. An electrical device, wherein: The electric device comprises the secondary battery according to any one of claims 13 to 15, and the secondary battery serves as a power supply for the electric device.

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