Negative electrode material, secondary battery, and electronic device

Abstract

According to the present invention, the negative electrode material is provided, the negative electrode material comprises the carbon-based material, the X-ray diffraction pattern of the negative electrode material has the diffraction peak a in the 2 [theta] 43-44 degree range and the diffraction peak b in the 2 [theta] 45-47 degree range through the X-ray diffraction method test, the peak intensity of the diffraction peak a is Ia, the peak intensity of the diffraction peak b is Ib, and Ia / Ib > 1. The negative electrode material disclosed by the invention has excellent dynamic performance, so that the internal resistance of the secondary battery containing the negative electrode material can be effectively reduced, and the comprehensive performance of the secondary battery is improved. The invention also provides a secondary battery comprising the negative electrode material.

Description

[0001] This application is a divisional application of the patent application No. 202280058225.5, with the title of "Cathode material, secondary battery and electronic device", filed on September 30, 2022. TECHNICAL FIELD

[0002] The present application relates to the field of energy storage, in particular to a cathode material, a secondary battery and an electronic device. BACKGROUND

[0003] With electrochemical devices such as lithium ion batteries becoming widely used energy systems, there are more and more sub-directions, one of which is fast charging and discharging application. Therefore, the development of energy systems with superior charging and discharging performance is crucial for their large-scale application in transportation, power grid, wind and solar systems.

[0004] However, fast charging and discharging can cause some problems. For example, when lithium ion batteries are charged and discharged at a large rate, the temperature rises rapidly during the charging and discharging process due to the existence of the internal resistance of the battery itself. This causes the battery to be in a high temperature environment, which greatly damages its cycle and safety performance. Therefore, there is a great demand for batteries with small internal resistance in the consumer market, and the development of batteries with small internal resistance is needed. The existing technology improves the battery impedance mainly by reducing the coating thickness of the electrode sheet and reducing the particle size of the negative active material, but this method will significantly reduce the energy density of the battery, reduce the endurance of the battery, and the cost is high. Therefore, it is necessary to develop a negative electrode material with low internal resistance and other moderate performance. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application provides a cathode material and a secondary battery comprising the same to improve the kinetic performance of the cathode material, thereby reducing the internal resistance of the secondary battery and improving the comprehensive performance of the secondary battery.

[0006] In a first aspect, the present application provides a cathode material comprising a carbon-based material, wherein the X-ray diffraction spectrum of the cathode material has a diffraction peak a in the range of 43° to 44° and a diffraction peak b in the range of 45° to 47° by X-ray diffraction method, wherein the peak intensity of the diffraction peak a is I a , and the peak intensity of the diffraction peak b is I b , I a / I b>1. The diffraction peak a and the diffraction peak b of the negative electrode material are related to the rhombohedral (3R) graphene layer stacking sequence in graphite. The diffraction peak a and the diffraction peak b appear in the negative electrode material of the application, and the peak intensity of the diffraction peak a is higher than that of the diffraction peak b, which represents the formation of unstable orthorhombic structure in the graphite, which can more easily deintercalate lithium, thereby reducing the internal resistance of the battery. In some embodiments, 2≤I a / I b ≤6.

[0007] In some embodiments, 400≤I a ≤2500. In some embodiments, 0≤I b ≤600.

[0008] In some embodiments, the ratio of the 004 crystal face diffraction peak area C004 to the 110 crystal face diffraction peak area C110 of the negative electrode material satisfies 1≤C004 / C110≤4 by X-ray diffraction method test. The ratio of C004 / C110 is a parameter reflecting the degree of crystal orientation of the negative electrode material. The larger the value of C004 / C110, the higher the degree of crystal orientation, and the more limited the deintercalation of active ions in the negative electrode material. The smaller the value of C004 / C110, the lower the degree of crystal orientation, and the more deintercalation of active ions in multiple directions of the negative electrode material. The C004 / C110 of the negative electrode material of the application is within the above range, and the active ions can be quickly deintercalated in the negative electrode material, thereby further improving the kinetic performance of the secondary battery. In some embodiments, 1≤C004 / C110≤3.

[0009] In some embodiments, the average stacking thickness of the negative electrode material along the a-axis direction is La, and 100nm≤La≤160nm by X-ray diffraction method test. In some embodiments, the average stacking thickness of the negative electrode material along the c-axis direction is Lc, and 18nm≤Lc≤30nm by X-ray diffraction method test. La represents the average size of the negative electrode material crystal along the a-axis direction, and Lc represents the thickness of the microcrystalline sheet of the negative electrode material along the c-axis direction perpendicular to it. The values of La and Lc can represent the degree of graphitization of the negative electrode material. The larger the values of La and Lc, the higher the gravimetric capacity of the negative electrode material. However, when the values of Lc and La are too high, although the gravimetric capacity of the negative electrode material increases, its cycle performance decreases. The values of Lc and La of the negative electrode material of the application are within the above range, and the negative electrode material has high gravimetric capacity while the cycle performance does not decrease significantly. In some embodiments, 110nm≤La≤160nm. In some embodiments, 20nm≤Lc≤30nm.

[0010] In some embodiments, the Dn10 of the negative electrode material is ≥ 0.4 μm. The Dn10 can characterize the content of fine powder in the negative electrode material, and the smaller the value, the more fine powder in the negative electrode material. When the content of fine powder is too high, the negative electrode material will consume more lithium ions during the first lithium intercalation process, thereby reducing the initial efficiency. In some embodiments, the Dn10 of the negative electrode material is ≥ 0.5 μm.

[0011] In some embodiments, the Dv10 and Dv90 of the negative electrode material satisfy: 5 ≤ Dv90 / Dv10 ≤ 25. Dv90 / Dv10 represents the concentration of the particle size distribution of the negative electrode material, and the larger the value, the more dispersed the particle size distribution of the material, and vice versa. When the volume fraction of the negative electrode material is the same, the larger the particle size, the wider the distribution, and the smaller the viscosity of the negative electrode slurry, thereby increasing the solid content and reducing the coating difficulty. At the same time, when the particle size distribution is wide, small particles can fill the voids of large particles, which helps to increase the compaction density of the electrode sheet and improve the volume energy density of the secondary battery. In addition, the particle morphology also has a great influence on the rate performance and low temperature performance of the secondary battery. The Dv90 / Dv10 of the negative electrode material of the present application is within the above range, and the secondary battery including the negative electrode material has high energy density, and the electrical properties such as rate performance and low temperature performance are not reduced. In some embodiments, 5 ≤ Dv90 / Dv10 ≤ 15.

[0012] In some embodiments, the Dv90 of the negative electrode material is 30 μm to 65 μm. In some embodiments, the Dv10 of the negative electrode material is 2 μm to 8 μm. The particle size of the negative electrode material is too large, which will make the slurry processing performance worse, and too small will reduce the initial efficiency. In some embodiments, the Dv90 is 30 μm to 60 μm. In some embodiments, the Dv10 is 3 μm to 7 μm.

[0013] In some embodiments, the 5t powder compaction density of the negative electrode material is C, and 1.5 g / cm 3 ≤ C ≤ 2.5 g / cm 3 The powder compaction density represents the degree to which the negative electrode material can be compressed during pressing, and the larger the value, the more it can be compressed during pressing, and the higher the volume energy density of the secondary battery. The powder compaction density of the negative electrode material of the present application is within the above range, and the secondary battery including the negative electrode material has high energy density. In some embodiments, 1.8 g / cm 3 ≤ C ≤ 2.1 g / cm 3 .

[0014] In some embodiments, the carbon-based material includes graphite, and the graphite includes one or more of natural graphite and artificial graphite. In some embodiments, the method for preparing the carbon-based material includes: performing graphite composite preparation, spheroidization treatment, coating treatment, and carbonization treatment on one or more of the natural graphite and the artificial graphite.

[0015] In some embodiments, the method for preparing the graphite composite includes: simultaneously dissolving one or more of the natural graphite and the artificial graphite in N-N dimethylformamide (DMF) with polymethyl methacrylate (PMMA), stirring at a temperature of 50-80°C for 10-14 hours, collecting the precipitate by filtration, washing with deionized water and ethanol for 2-4 times, and completely drying at a temperature of 60-90°C to obtain a graphite composite precursor; heating the graphite composite precursor in a tube furnace at a heating rate of 8-16°C / min to 1000-1200°C, then introducing CH4 / C2H2 / H2 mixed gas (proportions of 5-10:5-10:80-85, respectively) into the tube furnace, maintaining for 8-12 hours, and then naturally cooling to room temperature, thereby obtaining the graphite composite.

[0016] In some embodiments, the spheroidization treatment process includes: applying continuous impact force, compression force, and shearing force from the rotating disc, the inner wall, and the particles to the mixture containing the graphite composite and the dispersant solution, so that the graphite composite is spheroidized. In some embodiments, the spheroidization time is 10-20 minutes. In some embodiments, the impact force, compression force, and shearing force are applied to the mixture by using a spheroidization device, so that the mixture is subjected to collision, friction, shearing, and bending folding, thereby removing the corners of the graphite composite while achieving the effect of fixing the fine powder to the large particles. In some embodiments, the spheroidization device is a mixer granulator. In some embodiments, the rotational speed of the spheroidization device is 30-50 Hz. In some embodiments, the dispersant solution is an aqueous solution of carboxymethyl cellulose (CMC). In some embodiments, the mass content of carboxymethyl cellulose in the dispersant solution is 0.5-2%. In some embodiments, the mass content of the dispersant solution based on the mass of the graphite composite is 5-20%.

[0017] In some embodiments, the coating treatment process includes: using pitch to coat the spheroidized graphite composite. In some embodiments, the mass content of the pitch based on the mass of the spheroidized graphite composite is 2-15%. In some embodiments, the carbonization treatment temperature is 900-1500°C.

[0018] In a second aspect, the present application provides a secondary battery, comprising a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises the negative electrode material of the first aspect.

[0019] In some embodiments, the negative electrode further comprises an electrically conductive coating layer between the negative electrode active material layer and the negative electrode current collector. In some embodiments, the electrically conductive coating layer comprises at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotube and graphene. The electrically conductive coating layer can play a role in conducting electrons, and the charge transfer impedance is significantly reduced, thereby further improving the kinetic performance of the secondary battery. In some embodiments, the thickness of the electrically conductive coating layer is 0.5 μm to 1.2 μm.

[0020] In a third aspect, the present application provides an electronic device comprising the secondary battery of the second aspect.

[0021] The present application helps to reduce the particle size of the graphite material by spheroidizing, coating and carbonizing the graphite material, converting the irregular morphology into a regular spherical morphology, thereby significantly improving the kinetic performance of the negative electrode material, further reducing the internal resistance of the secondary battery, and improving the comprehensive performance of the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD pattern of the negative electrode material of Example 1 and Comparative Example 1 of the present application.

[0023] Figure 2 DCR curve of the lithium ion battery of Example 1 and Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION

[0024] For the sake of brevity, the present application has only specifically disclosed some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit be combined with any other upper limit to form a range not explicitly recited. In addition, each individual point or single numerical value disclosed by itself can be combined with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0025] In the description of the present application, "above", "below" include the number itself, unless otherwise specified.

[0026] Unless otherwise specified, the terms used in the present application have the commonly understood meanings understood by those skilled in the art. Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various measurement methods commonly used in the art (for example, can be tested according to the methods given in the examples of the present application).

[0027] The list of items connected by “at least one of,” “at least one,” “at least one of the,” or other similar phrases can mean any combination of the listed items. For example, if A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if A, B, and C are listed, the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0028] The present application is further illustrated by the following specific embodiments. It is to be understood that these embodiments are merely illustrative of the present application and do not limit the scope of the application.

[0029] I. Negative electrode material

[0030] The negative electrode material provided by the present application comprises a carbon-based material. The X-ray diffraction spectrum of the negative electrode material has a diffraction peak a in the range of 43° to 44° and a diffraction peak b in the range of 45° to 47°, as tested by X-ray diffraction method, wherein the peak intensity of the diffraction peak a is I a , and the peak intensity of the diffraction peak b is I b , and I a / I b > 1. The diffraction peak a and the diffraction peak b of the negative electrode material are related to the rhombohedral (3R) graphene layer stacking sequence in graphite. The appearance of the diffraction peak a and the diffraction peak b in the negative electrode material of the present application, and the peak intensity of the diffraction peak a being higher than the peak intensity of the diffraction peak b, represent that there is a rhombohedron structure in the formed graphite, which can more easily perform lithium deintercalation and has a higher gravimetric capacity. In some embodiments, I a / I b is 1.2, 1.4, 1.6, 1.8, 2.3, 2.5, 2.7, 3.0, 3.3, 3.5, 3.7, 4.0, 4.3, 4.5, 4.7, 5.0, 5.3, 5.5, 5.7, 5.9, or a range consisting of any two of these values. In some embodiments, 2 ≤ I a / I b ≤ 6.

[0031] In some embodiments, 400 ≤ I a ≤ 2500. In some embodiments, I aI is 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, or a range between any two of these values. In some embodiments, 0 < I b I is 600. In some embodiments, I b I is 50, 100, 150, 200, 300, 350, 400, 450, 500, 550, or a range between any two of these values. In some embodiments, I a I is the highest intensity value of the diffraction peak a belonging to the range of 43° to 44°. I b I is the highest intensity value of the diffraction peak b belonging to the range of 45° to 47°.

[0032] In some embodiments, the ratio of the 004 crystal plane diffraction peak area C004 to the 110 crystal plane diffraction peak area C110 of the negative electrode material satisfies 1 < C004 / C110 < 4, as tested by X-ray diffraction. The ratio of C004 / C110 is a parameter reflecting the degree of crystal orientation of the negative electrode material. The larger the value of C004 / C110, the higher the degree of crystal orientation, and the more limited the surface of active ions deintercalation in the negative electrode material. The smaller the value of C004 / C110, the lower the degree of crystal orientation, and the more directions of active ions deintercalation in the negative electrode material. The C004 / C110 of the negative electrode material of the present application is within the above range, and the active ions can be quickly deintercalated in the negative electrode material, thereby further improving the kinetic performance of the secondary battery. In some embodiments, C004 / C110 is 1.2, 1.4, 1.6, 1.8, 2.3, 2.5, 2.7, 3.0, 3.3, 3.5, 3.7, or a range between any two of these values. In some embodiments, 1 < C004 / C110 < 3.

[0033] In some embodiments, the average packing thickness of the negative electrode material along the a-axis direction is La, 100 nm≤La≤160 nm, as tested by X-ray diffraction method. In some embodiments, La is 100 nm, 103 nm, 105 nm, 107 nm, 110 nm, 113 nm, 115 nm, 117 nm, 120 nm, 123 nm, 125 nm, 127 nm, 130 nm, 143 nm, 145 nm, 147 nm, 150 nm, 153 nm, 155 nm, 157 nm, or a range consisting of any two of these values. In some embodiments, the average packing thickness of the negative electrode material along the c-axis direction is Lc, 18 nm≤Lc≤30 nm, as tested by X-ray diffraction method. In some embodiments, Lc is 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, or a range consisting of any two of these values. La represents the average size of the negative electrode material crystals along the a-axis direction, and Lc represents the thickness of the microcrystal sheets of the negative electrode material packed along the c-axis direction perpendicular thereto. The values of La and Lc can characterize the degree of graphitization of the negative electrode material, and the larger the values of La and Lc, the higher the gravimetric capacity of the negative electrode material. However, when the values of Lc and La are too high, although the gravimetric capacity of the negative electrode material becomes larger, the cycle performance thereof decreases. The values of Lc and La of the negative electrode material of the present application are within the above ranges, and the negative electrode material has a high gravimetric capacity while the cycle performance thereof does not decrease significantly. In some embodiments, 110 nm≤La≤160 nm. In some embodiments, 20 nm≤Lc≤30 nm.

[0034] In some embodiments, the negative electrode material has a Dn10≥0.4 μm. Dn10 can characterize the content of fine powder in the negative electrode material, and the smaller the value, the more fine powder in the negative electrode material. When the content of fine powder is too high, the negative electrode material consumes more lithium ions during the first lithium intercalation process, thereby causing the initial efficiency to decrease. In some embodiments, Dn10 is 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 1.95 μm, 2.0 μm, or a range consisting of any two of these values. In some embodiments, the negative electrode material has a Dn10≥0.5 μm. In the present application, Dn10 represents the particle size at which 10% of the particles of the negative electrode material are smaller than the value in the particle size distribution on a number basis.

[0035] In some embodiments, the Dv10 and Dv90 of the negative electrode material satisfy: 5≤Dv90 / Dv10≤25. Dv90 / Dv10 represents the concentration of the particle size distribution in the negative electrode material, and the greater the value, the more dispersed the particle size distribution of the material, and vice versa. With the same volume fraction of the negative electrode material, the greater the particle size, the wider the distribution, and the smaller the viscosity of the negative electrode slurry, which in turn can increase the solid content and reduce the coating difficulty. At the same time, when the particle size distribution is wide, small particles can fill the voids of large particles, which helps to increase the compaction density of the electrode sheet and improve the volume energy density of the secondary battery. In addition, the particle morphology also has a great influence on the rate performance and low temperature performance of the secondary battery. The Dv90 / Dv10 of the negative electrode material in the present application is within the above range, and the secondary battery including the negative electrode material has high energy density, and the electrical properties such as rate performance and low temperature performance are not reduced. In some embodiments, Dv90 / Dv10 is 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 20, 22, 24, or a range consisting of any two of these values. In some embodiments, 5≤Dv90 / Dv10≤15.

[0036] In some embodiments, the Dv90 of the negative electrode material is 30 pm to 65 pm. In some embodiments, the Dv10 of the negative electrode material is 2 pm to 8 pm. If the particle size of the negative electrode material is too large, the slurry processing performance will be poor, and if it is too small, the initial efficiency will be reduced. In some embodiments, Dv90 is 32 pm, 34 pm, 36 pm, 38 pm, 40 pm, 43 pm, 45 pm, 47 pm, 50 pm, 52 pm, 55 pm, 57 pm, 59 pm, 62 pm, 64 pm, or a range consisting of any two of these values. In some embodiments, Dv90 is 30 pm to 60 pm. In some embodiments, Dv10 is 3.5 pm, 4 pm, 4.5 pm, 5 pm, 5.5 pm, 6 pm, 6.5 pm, or a range consisting of any two of these values. In some embodiments, Dv10 is 3 pm to 7 pm. In the present application, Dv10 represents that 10% of the particles in the negative electrode material have a particle size less than this value on a volume basis. Dv90 represents that 90% of the particles in the negative electrode material have a particle size less than this value on a volume basis.

[0037] In some embodiments, the 5t powder compaction density of the negative electrode material is C, and the 1.5g / cm 3 ≤C≤2.5g / cm 3The powder compaction density represents the degree to which the negative material can be compressed when pressed, and the greater this value, the more it can be compressed when pressed, and the higher the volumetric energy density of the secondary battery. The powder compaction density of the negative material of the present application is within the above range, and the secondary battery including the negative material has a high energy density. In some embodiments, C is 1.6 g / cm 3 , 1.7 g / cm 3 , 1.85 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 , 2.05 g / cm 3 , 2.15 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , or a range consisting of any two of these values. In some embodiments, 1.8 g / cm 3 / ≤ C ≤ 2.1 g / cm 3 .

[0038] In some embodiments, the carbon-based material includes graphite, and the graphite includes one or more of natural graphite and artificial graphite. In some embodiments, the method of preparing the carbon-based material includes: performing graphite composite material preparation, spheroidization treatment, coating treatment, and carbonization treatment on one or more of the natural graphite and the artificial graphite.

[0039] In some embodiments, the process of preparing the graphite composite material includes simultaneously dissolving one or more of the natural graphite and the artificial graphite in N-N dimethylformamide (DMF) with polymethyl methacrylate (PMMA), stirring at a temperature of 50-80 °C for 10-14 h, collecting the precipitate by filtration, washing with deionized water and ethanol for 2-4 times, and completely drying at a temperature of 60-90 °C to obtain a graphite composite material precursor. The graphite composite material precursor is heated to 1000-1200 °C in a tube furnace at a heating rate of 8-16 °C / min, then a CH4 / C2H2 / H2 mixed gas (proportions of 5-10:5-10:80-85, respectively) is introduced into the tube furnace, and maintained for 8-12 h before naturally cooling to room temperature, thereby obtaining the final graphite composite material.

[0040] In some embodiments, the spheroidization process comprises applying continuous impact force, compression force and shearing force from the rotating disc, the inner wall and the particles to the mixture comprising the graphite composite and the dispersant solution, so that the graphite composite is spheroidized. In some embodiments, the spheroidization time is 10 min to 20 min, for example, 12 min, 14 min, 16 min or 18 min. In some embodiments, the mixture is subjected to collision, friction, shearing and bending folding by using the spheroidization device to apply impact force, compression force and shearing force to the mixture, thereby removing the corners of the graphite composite while achieving the effect of fixing the fine powder to the large particles. In some embodiments, the spheroidization device is a mixing granulator. In some embodiments, the rotating speed of the spheroidization device is 30 Hz to 50 Hz, for example, 35 Hz, 40 Hz or 45 Hz.

[0041] In some embodiments, the dispersant solution is an aqueous solution of carboxymethyl cellulose (CMC). In some embodiments, the mass content of carboxymethyl cellulose in the dispersant solution is 0.5% to 2%, for example, 0.7%, 1.0%, 1.3%, 1.5% or 1.7%. In some embodiments, the mass content of the dispersant solution is 5% to 20%, for example, 7%, 10%, 13%, 15%, 17% or 19%, based on the mass of the graphite composite.

[0042] In some embodiments, the coating process comprises coating the spheroidized graphite composite with pitch. In some embodiments, the mass content of pitch is 2% to 15%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or 14%, based on the mass of the spheroidized graphite composite. In some embodiments, the carbonization temperature is 900°C to 1500°C, for example, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C or 1450°C. In some embodiments, the carbonization time is 3 h to 10 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h or 9 h.

[0043] Secondary battery

[0044] The secondary battery provided herein comprises a negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises the negative electrode material of the first aspect.

[0045] In some embodiments, the negative electrode further comprises an electrically conductive coating layer between the negative electrode active material layer and the negative electrode current collector. In some embodiments, the electrically conductive coating layer comprises at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotube, and graphene. The electrically conductive coating layer can function to conduct electrons, and the charge transfer impedance is significantly reduced, thereby further improving the kinetic performance of the secondary battery. In some embodiments, the thickness of the electrically conductive coating layer is 0.5 μm to 1.2 μm. In some embodiments, the thickness of the electrically conductive coating layer is 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, or a range between any two of these values.

[0046] In some embodiments, the negative electrode current collector comprises a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with an electrically conductive metal, or any combination thereof.

[0047] In some embodiments, the negative electrode active material layer further comprises a binder and an electrically conductive agent. In some embodiments, the binder comprises, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, butadiene-styrene rubber, acrylated butadiene-styrene rubber, epoxy resin, or nylon, etc.

[0048] In some embodiments, the electrically conductive agent comprises, but is not limited to, carbon-based materials, metal-based materials, electrically conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials are selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the electrically conductive polymer is a polyphenylene derivative.

[0049] The secondary battery of the present application further comprises a positive electrode, which comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material, a binder, and an electrically conductive agent.

[0050] According to some embodiments of the present application, the positive electrode current collector can be a metal foil or a composite current collector. For example, an aluminum foil can be used. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0051] According to some embodiments of the present application, the positive active material includes at least one of lithium cobaltate, lithium nickel-manganese cobaltate, lithium nickel-manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganate, spinel lithium nickel-manganese, and lithium titanate. In some embodiments, the binder includes a binder polymer, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane. In some embodiments, the polyolefin binder includes at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol, or polyacrylic acid. In some embodiments, the conductive agent includes a carbon-based material, such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, or carbon fiber; a metal-based material, such as metal powder or metal fiber of copper, nickel, aluminum, silver, or the like; a conductive polymer, such as polyphenylene derivative; or a mixture thereof.

[0052] The secondary battery of the present application further includes a separator film, and the material and shape of the separator film used in the secondary battery of the present application are not particularly limited and can be any of the techniques disclosed in the prior art. In some embodiments, the separator film includes a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, and the like.

[0053] For example, the separator film can include a base layer and a surface treatment layer. The base layer is a non-woven fabric, a film, or a composite film having a porous structure, and the material of the base layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0054] The surface treatment layer is provided on at least one surface of the base layer and can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0055] The secondary battery of the present application further includes an electrolyte. The electrolyte usable in the present application can be any electrolyte known in the art.

[0056] According to some embodiments of the present application, the electrolyte includes an organic solvent, a lithium salt, and an optional additive. The organic solvent in the electrolyte of the present application can be any organic solvent known in the art that can be used as a solvent for an electrolyte. The electrolyte used in the electrolyte of the present application is not limited and can be any electrolyte known in the art. The additive of the electrolyte of the present application can be any additive known in the art that can be used as an additive for an electrolyte. In some embodiments, the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some embodiments, the organic solvent includes an ether-based solvent, such as including at least one of 1,3-dioxolane (DOL) and dimethoxyethane (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB), or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0057] According to some embodiments of the present application, the secondary battery of the present application includes, but is not limited to, a lithium-ion battery or a sodium-ion battery. In some embodiments, the secondary battery includes a lithium-ion battery.

[0058] III. Electronic device

[0059] The present application further provides an electronic device including the secondary battery of the second aspect of the present application.

[0060] The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, a notebook computer, a pen input type computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a timepiece, an electric power tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0061] In the following examples and comparative examples, the reagents, materials and apparatus used are commercially available unless otherwise stated.

[0062] Examples and Comparative Examples

[0063] Example 1

[0064] Preparation of the negative electrode material

[0065] 95 g of artificial graphite was dissolved in 5 g of polymethyl methacrylate (PMMA) in 100 mL of N-N dimethylformamide (DMF) at 70°C for 12 h; the precipitate was collected by filtration, and the precipitate was washed with deionized water and ethanol for 2 times, and completely dried at 80°C to obtain a graphite composite precursor; the graphite composite precursor was heated to 1100°C at a heating rate of 10°C / min in a tube furnace, then CH4 / C2H2 / H2 mixed gas (the ratio is 5:10:85 respectively) was introduced into the tube furnace, and maintained for 10 h, and then naturally cooled to room temperature to obtain a graphite composite material; the graphite composite material was mixed with a 10% proportion of a 1% solid content CMC aqueous solution, and spheroidized in a spheroidizing device at a rotation speed of 40 Hz for 15 minutes; after spheroidization, 5% pitch was used for coating treatment; finally, the coating mixture was heated to 1000°C at a rate of 5°C / min, and maintained for 5 h, and then naturally cooled to room temperature to obtain a carbon-based material, i.e. a negative electrode material.

[0066] Preparation of the negative electrode

[0067] The above-prepared negative electrode material, a binder styrene butadiene rubber (abbreviated as SBR), and a thickening agent sodium carboxymethyl cellulose (abbreviated as CMC) were mixed in a weight ratio of 97:1.5:1.5, and then fully stirred in a proper amount of deionized water solvent to form a uniform negative electrode slurry; the slurry was coated on a current collector Cu foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0068] Preparation of the positive electrode

[0069] Lithium cobalt oxide (chemical formula: LiCoO2) is selected as the positive active material, which is mixed with conductive agent acetylene black and binder polyvinylidene fluoride (abbreviated as PVDF) in a weight ratio of 96.3:2.2:1.5 in an appropriate amount of N-methyl pyrrolidone (abbreviated as NMP) solvent, and is fully stirred to form a uniform positive electrode slurry. The slurry is coated on the current collector Al foil, dried, and cold-pressed to obtain a positive electrode sheet.

[0070] Preparation of electrolyte

[0071] In a dry argon atmosphere glove box, ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC: EMC: DEC = 1:3:2:4, then vinyl fluoride carbonate and vinylene carbonate are added, and after dissolution and sufficient stirring, lithium salt LiPF6 is added, and the mixture is uniformly mixed to obtain an electrolyte. The mass percentage of LiPF6 is 12.5%, the mass percentage of vinyl fluoride carbonate is 3%, and the mass percentage of vinylene carbonate is 1%. The mass percentages of the substances are calculated based on the mass of the electrolyte.

[0072] Preparation of lithium ion battery

[0073] The positive electrode, the separator film (polyethylene porous polymer film), and the negative electrode are stacked in order, with the separator film between the positive electrode and the negative electrode to play a separating role, and then wound to obtain an electrode assembly. After welding the tab, the electrode assembly is placed in an outer packaging foil aluminum plastic film, the electrolyte prepared above is injected into the dried electrode assembly, and after vacuum packaging, standing, formation, shaping, capacity testing, and other processes, a soft package lithium ion battery is obtained.

[0074] Examples 2 to 10 and Comparative Example 1

[0075] Preparation of negative electrode material

[0076] The preparation process of the negative electrode material is similar to that of Example 1, except that the ratio of carbon-based material to PMMA, the speed of the spheroidizing equipment, the proportion of residual carbon in the coated pitch, and the carbonization temperature are adjusted to prepare the corresponding negative electrode material. The specific preparation parameters are shown in Table a:

[0077] Table a

[0078]

[0079] The preparation of the positive electrode, the electrolyte, and the lithium ion battery is the same as in Example 1.

[0080] Examples 11 to 20

[0081] Preparation of negative electrode material

[0082] The negative material was prepared similarly to Example 5, except that the C004 / C110 value of the negative material was adjusted by adjusting the solid content of the CMC solution. In the preparation of Examples 11-20, the solid content of the CMC solution was distributed as 0.8%, 0.6%, 1.2%, 1.0%, 1.6%, 0.4%, 0.2%, 1.8%, 2.0%, 1.4%.

[0083] The positive electrode, electrolyte, and lithium ion battery were prepared similarly to Example 5.

[0084] Examples 21-30

[0085] Negative material preparation

[0086] The negative material was prepared similarly to Example 14, except that the La and Lc values of the negative material were adjusted by adjusting the heating rate of the carbonization process. In the preparation of Examples 21-30, the heating rate of the carbonization process was distributed as 2.5°C / min, 6.5°C / min, 9.5°C / min, 10°C / min, 1.5°C / min, 4.5°C / min, 5°C / min, 8°C / min, 8.5°C / min, 9°C / min.

[0087] The positive electrode, electrolyte, and lithium ion battery were prepared similarly to Example 14.

[0088] Examples 31-40

[0089] The negative material was prepared similarly to Example 25, except that the particle size of the negative material was adjusted by adjusting the spheroidization time. In the preparation of Examples 31-40, the spheroidization time was distributed as 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min.

[0090] The positive electrode, electrolyte, and lithium ion battery were prepared similarly to Example 25.

[0091] Examples 41-45

[0092] Negative material preparation

[0093] The negative material was prepared similarly to Example 35.

[0094] Negative preparation

[0095] The negative was prepared similarly to Example 35, except that a conductive coating was added.

[0096] The positive electrode, electrolyte, and lithium ion battery were prepared similarly to Example 35.

[0097] Test method

[0098] 1. XRD test of negative electrode material

[0099] The XRD test curve of the negative electrode material is tested by using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE), wherein the target is Cu Kα, the voltage / current is 40KV / 40mA, the scanning angle range is 5° to 80°, the scanning step is 0.00836°, and the time for each step is 0.3s.

[0100] wherein the a peak is located at a diffraction angle 2θ in the range of 43°-44°, the b peak is located at a diffraction angle 2θ in the range of 45°-47°, Ia is the highest intensity value of the diffraction peak a, and Ib is the highest intensity value of the diffraction peak b. a and Ib are the highest intensity values of the diffraction peak a and the diffraction peak b, respectively. b

[0101] The diffraction peak of the (004) plane (the 004 peak in the XRD pattern of the negative electrode material) is located at a diffraction angle 2θ in the range of 52°-57°, and the diffraction peak of the (110) plane (the 110 peak in the XRD pattern of the negative electrode material) is located at a diffraction angle 2θ in the range of 75°-80°. The peak area value of the 004 peak calculated by integration is denoted as C004, and the peak area value of the 110 peak calculated by integration is denoted as C110, so as to calculate the ratio of C004 / C110 of the negative electrode material.

[0102] 2. Test of powder compaction density

[0103] The test standard of the powder compaction density refers to GB / T 24533-2009 “Graphite-based negative electrode material for lithium ion battery”. The specific test method is as follows:

[0104] 1.0000±0.0500g of the negative electrode material sample is weighed and placed in a test mold (CARVER #3619(13mm)), and then the sample is placed in a test equipment, wherein the test equipment is a Sansi Zongheng UTM7305 test tonnage of 0.3t, 0.5t, 0.75t, 1.0t, 1.5t, 2.0t, 2.5t, 3.0t, 4.0t, 5.0t, the pressure increasing rate is 10mm / min, the pressure increasing holding time is 30s, the pressure releasing rate is 30mm / min, and the pressure releasing holding time is 10s.

[0105] In this application, the powder compaction density is the compaction density measured at a test tonnage of 5t. The calculation formula of the compaction density is: compaction density = material mass / (material force area × sample thickness).

[0106] 3. Test of particle size (Dv10, Dv90 and Dn10)

[0107] ​The particle size test method refers to GB / T 19077-2016. The specific process is to weigh 1 g of the negative electrode material sample, mix it uniformly with 20 mL of deionized water and a small amount of dispersant, place it in an ultrasonic device for ultrasonic treatment for 5 min, then pour the solution into the sample injection system Hydro2000SM for testing. The testing equipment used is Mastersizer 3000 produced by Malvern Company. During the test, when the laser beam passes through the dispersed particle sample, the particle size measurement is completed by measuring the intensity of scattered light. Then the data is used to analyze and calculate the particle size distribution of the particles forming the scattering spectrum. In the volume-based particle size distribution of the negative electrode material, the particle size reaching 10% of the volume accumulation from the small particle size side is the Dv10 of the negative electrode material. At the same time, in the volume-based particle size distribution of the negative electrode material, the particle size reaching 99% of the volume accumulation from the small particle size side is the Dv99 of the negative electrode material. In the number-based particle size distribution of the negative electrode material, 10% of the particle size is less than the value, which is the Dn10 of the negative electrode material. The refractive index of the particles used for testing is 1.8. One sample is tested three times, and the final particle size is the average of the three tests.

[0108] 4. Gravimetric capacity test

[0109] (1) Preparation of button cell: the negative electrode prepared in the above examples, lithium sheet, separator, electrolyte, steel sheet, foamed nickel and button cell shell are assembled together to obtain a button cell, which is statically placed for 6 h before testing.

[0110] (2) The button cell is placed on a blue power tester for testing. The test process is as follows: discharged to 5 mV at 0.05C, statically placed for 5 min, discharged to 5 mV at 0.05 mA, discharged to 5 mV at 0.01 mA, charged to 2.0 V at 0.1C to obtain the charge capacity, and finally divided by the weight of the active material to obtain the gravimetric capacity of the negative electrode material.

[0111] 5. Lithium ion battery DCR direct current impedance test

[0112] 1) The test temperature is 25°C;

[0113] 2) Static for 60 min;

[0114] 3) 0.5C CC (constant current) to 4.43V, CV (constant voltage) to 0.025C;

[0115] 4) Static for 10 min;

[0116] Discharge, temperature 25°C

[0117] 5) 0.1C DC (direct current) to 3V;

[0118] 6) Static for 10 min;

[0119] 7) 0.5C CC to 4.43V, CV to 0.025C;

[0120] 8) rest for 1h;

[0121] 9) 0.1C DC to 10s;

[0122] 10) 1C DC to 1s;

[0123] 11) rest for 1h;

[0124] 12) 0.5C DC to 6min;

[0125] 13) if voltage ≤ 2.5V, go to step 15;

[0126] 14) repeat step 8 to step 13 for 26 times;

[0127] 15) rest for 10min;

[0128] 16) 0.5C CC to 3.95V, CV to 0.025C;

[0129] 17) rest for 10min;

[0130] Take the impedance DCR of the battery at 70% SOC, and the test is completed.

[0131] Test results

[0132] Table 1 shows the effect of the ratio of the peak intensity Ia of the diffraction peak at 2θ of 43° to 44° to the peak intensity I b of the diffraction peak at 2θ of 45° to 47° in the XRD pattern of the negative electrode material on the performance of the lithium ion battery. In Table 1, the Lc of the examples and the comparative examples is 10.7 nm, the La is 102 nm, and the C004 / C110 is 4.71.

[0133] Table 1

[0134]

[0135] From the data in Table 1, it can be seen that when the negative electrode material meets the conditions that the XRD pattern has diffraction peaks at 2θ of 43° to 44° and 45° to 47° respectively, and the ratio of the diffraction peak intensity I a at 2θ of 43° to 44° to the diffraction peak intensity I b at 2θ of 45° to 47° is 2 to 6, the lithium ion battery has a lower DCR impedance.

[0136] Table 2 further studies the effect of the C004 / C110 value of the negative electrode material on the performance of the lithium ion battery based on Example 5.

[0137] Table 2

[0138]

[0139] From the data in Table 2, it can be seen that when the C004 / C110 of the negative electrode material powder is in the range of 1-3, the active material is isotropic, and the lithium ion battery can exhibit good kinetic performance.

[0140] Table 3 further studies the influence of the La and Lc values of the negative electrode material on the performance of the lithium ion battery based on Example 14.

[0141] Table 3

[0142]

[0143] From the data in Table 3, it can be seen that when the La is 110 nm to 160 nm and the Lc is 20 nm to 30 nm, the specific capacity Cap of the negative electrode material is ≥350 mAh / g, and the impedance DCR of the lithium ion battery can also be further improved.

[0144] Table 4 further studies the influence of the particle size and distribution of the negative electrode material on the performance of the lithium ion battery based on Example 25.

[0145] Table 4

[0146]

[0147] From the data in Table 4, it can be seen that when the Dn10 of the negative electrode material is ≥0.5 μm, the initial efficiency of the lithium ion battery can be improved to a certain extent, and the DCR is correspondingly reduced. When the negative electrode material satisfies 5≤Dv90 / Dv10≤15, the Dv90 is 30 μm to 60 μm, and the Dv10 is 2 μm to 8 μm, the impedance DCR of the lithium ion battery is also improved to a certain extent.

[0148] Table 5 further studies the influence of the thickness and type of the conductive coating in the negative electrode on the performance of the lithium ion battery based on Example 35.

[0149] Table 5

[0150]

[0151] From the data in Table 5, it can be seen that when the thickness of the conductive coating is in the range of 0.5 μm to 1.2 μm, the DCR impedance of the lithium ion battery is low.

[0152] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A negative electrode material comprising a carbon-based material, wherein, as measured by X-ray diffraction, the X-ray diffraction pattern of the negative electrode material exhibits diffraction peak a in the range of 2θ from 43° to 44° and diffraction peak b in the range of 2θ from 45° to 47°, wherein... The peak intensity of the diffraction peak a is I a The peak intensity of the diffraction peak b is I. b I a / I b >1; by X-ray diffraction, the average stacking thickness of the negative electrode material along the a-axis is La, 102nm≤La≤160nm, and the average stacking thickness of the negative electrode material along the c-axis is Lc, 20nm≤Lc≤30nm.

2. The negative electrode material according to claim 1, wherein, 2≤I a / I b ≤6。 3. The negative electrode material according to claim 1 or 2, wherein, 400≤I a ≤2500; and / or 0≤I b ≤600.

4. The negative electrode material according to claim 1 or 2, wherein, The negative electrode material satisfies at least one of the following conditions (i), (iii) to (vi): (i) The ratio of the peak area C004 of the 004 crystal plane to the peak area C004 of the 110 crystal plane of the negative electrode material is satisfied by X-ray diffraction method, which satisfies 1≤C004 / C110≤4. (iii) The Dn10 of the negative electrode material is ≥0.4 μm; (iv) The negative electrode material's Dv10 and Dv90 satisfy: 5≤Dv90 / Dv10≤25; (v) The Dv90 of the negative electrode material is 30 μm to 65 μm, and the Dv10 of the negative electrode material is 2 μm to 8 μm; (vi) The compacted density of the 5t powder of the negative electrode material is C, 1.5 g / cm³. 3 / ≤C≤2.5g / cm 3 .

5. The negative electrode material according to claim 4, wherein, The negative electrode material satisfies at least one of the following conditions (vii) to (xii): (vii)1≤C004 / C110≤3; (viii)110nm≤La≤151.9nm, 22.1nm≤Lc≤27.7nm; (ix)Dn10≥0.5μm; (x)5≤Dv90 / Dv10≤15; (xi)Dv90 is 30μm to 60μm, and Dv10 is 3μm to 7μm; (xii)1.8 g / cm 3 / ≤C≤2.1g / cm 3 。 6. The negative electrode material according to claim 1 or 2, wherein, The carbon-based material includes graphite.

7. The negative electrode material according to claim 1 or 2, wherein, The method for preparing the carbon-based material includes: preparing graphite composite materials, spheroidizing, coating and carbonizing graphite materials.

8. A secondary battery comprising a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises the negative electrode material according to any one of claims 1-7.

9. The secondary battery according to claim 8, wherein, The negative electrode also includes a conductive coating located between the negative electrode active material layer and the negative electrode current collector.

10. The secondary battery according to claim 9, wherein, The conductive coating comprises at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotubes, and graphene; and / or The thickness of the conductive coating is from 0.5 μm to 1.2 μm.

11. An electronic device comprising the secondary battery according to any one of claims 8-10.

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