Negative active material, electrochemical device, and electronic device

Abstract

The application discloses a negative electrode active material, an electrochemical device and an electronic device. The negative electrode active material comprises amorphous carbon, and the amorphous carbon satisfies the following conditions: 10% <= A <= 30%, wherein A is the percentage of the total volume of pores with a diameter less than 100 nm in the total volume of pores with a diameter less than 2 nm in the amorphous carbon; 10% <= B <= 30%, wherein B is the percentage of the total volume of pores with a diameter less than 100 nm in the total volume of pores with a diameter of 2-10 nm in the amorphous carbon; 50% <= C <= 70%, wherein C is the percentage of the total volume of pores with a diameter less than 100 nm in the total volume of pores with a diameter of 10-100 nm in the amorphous carbon; A+B+C = 100%; and the amorphous carbon comprises hard carbon. The electrochemical device prepared by using the negative electrode active material can simultaneously have excellent kinetic performance, energy density and cycle performance.

Description

Technical Field

[0001] This invention relates to a negative electrode active material, an electrochemical device, and an electronic device. Background Technology

[0002] 2023 was hailed as the commercialization year of sodium-ion batteries. Due to their abundant raw material resources and low cost, sodium-ion batteries have become a potential alternative to lithium-ion or lead-acid batteries in some areas. Compared to lithium-ion batteries, sodium-ion batteries currently primarily use soft carbon and hard carbon as anode materials, but their specific capacity is only 200-320 mAh / g, and their compaction density is only 0.9-1.0 g / cc, significantly lower than the specific capacity and compaction density of graphite, the anode material for lithium-ion batteries. Although some modification methods can achieve a specific capacity of 350 mAh / g or even higher for hard carbon, its compaction density also decreases accordingly, accompanied by difficulties in processing and reduced cycle life.

[0003] Current improvements to negative electrode active materials for batteries mainly focus on the selection of components, the ratio of their amounts, and the sphericity and regularity of certain component particles. However, these improvements have not yielded ideal results in simultaneously increasing the energy density and cycle life of batteries, especially sodium-ion batteries. Therefore, there is an urgent need to develop a negative electrode active material that can balance energy density and cycle life. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of existing batteries that cannot simultaneously meet the requirements of high energy density and high cycle life, and to provide a negative electrode active material, an electrochemical device, and an electronic device. The electrochemical device prepared using this negative electrode active material can simultaneously possess excellent kinetic performance, energy density, and cycle performance.

[0005] In a first aspect, the present invention provides a negative electrode active material, the negative electrode active material comprising amorphous carbon, wherein the amorphous carbon satisfies the following conditions:

[0006] 10%≤A≤30%, where A is the percentage of the total volume of pores with a diameter less than 2nm in the amorphous carbon to the total volume of pores with a diameter less than 100nm;

[0007] 10%≤B≤30%, where B is the percentage of the total volume of pores with an inner diameter of 2-10 nm in the amorphous carbon to the total volume of pores with a diameter of less than 100 nm;

[0008] 50%≤C≤70%, where C is the percentage of the total volume of pores with an inner diameter of 10-100nm in the amorphous carbon to the total volume of pores with a diameter of less than 100nm;

[0009] A+B+C=100%;

[0010] The amorphous carbon includes hard carbon.

[0011] Secondly, the present invention provides an electrochemical device comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode material layer located on the current collector, the negative electrode material layer comprising a negative electrode active material and a conductive agent as described above, wherein the amorphous carbon and the conductive agent satisfy the following conditions:

[0012] 1≤D1 / D2≤10, where D1 is the average pore diameter of the pores with a diameter of 10-100nm in the amorphous carbon, and D2 is the particle size of the conductive agent.

[0013] Thirdly, the present invention provides an electronic device comprising the electrochemical device as described above.

[0014] The positive and progressive effects of this invention are as follows:

[0015] This invention provides an amorphous carbon with a specific pore volume distribution. By adjusting the distribution ratio of amorphous carbon with different pore sizes in the negative electrode active material, specifically the proportion of amorphous carbon with pore sizes less than 100 nm in different diameter ranges, ions, electrolyte molecules and conductive agents can work synergistically in a suitable ratio, thereby improving the energy density and cycle performance of the battery. Detailed Implementation

[0016] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0017] Negative electrode active material

[0018] In the negative electrode active material according to the first aspect of the present invention, the negative electrode active material comprises amorphous carbon, and the amorphous carbon satisfies the following conditions:

[0019] 10%≤A≤30%, where A is the percentage of the total volume of pores with a diameter less than 2nm in the amorphous carbon to the total volume of pores with a diameter less than 100nm;

[0020] 10%≤B≤30%, where B is the percentage of the total volume of pores with an inner diameter of 2-10 nm in the amorphous carbon to the total volume of pores with a diameter of less than 100 nm;

[0021] 50%≤C≤70%, where C is the percentage of the total volume of pores with an inner diameter of 10-100nm in the amorphous carbon to the total volume of pores with a diameter of less than 100nm;

[0022] A+B+C=100%;

[0023] The amorphous carbon includes hard carbon.

[0024] Those skilled in the art generally understand that amorphous carbon includes hard carbon and soft carbon. In the embodiments of the present invention, hard carbon accounts for more than 90% of the weight of amorphous carbon.

[0025] The inventors believe that the volume ratio of pores with a diameter of less than 2 nm within amorphous carbon directly contributes to the sodium ion storage capacity of amorphous carbon, where sodium exists as metallic clusters within these pores. Increasing the proportion of amorphous carbon (A) helps increase its capacity, thereby improving energy density; however, excessively high A proportion leads to a decrease in compaction density due to the pore structure, resulting in a decrease in the battery's energy density.

[0026] The volume fraction of pores with an inner diameter of 2-10 nm in amorphous carbon affects the entry of electrolyte molecules, thus influencing the electrolyte absorption and retention capacity of amorphous carbon and improving ion transport. Increasing the proportion of boron (B) contributes to improved battery kinetics and cycle performance; however, excessively high B proportions can impair the ion storage capacity of amorphous carbon micropores, leading to a decrease in the capacity of amorphous carbon and consequently a decrease in the energy density of the battery.

[0027] The volume fraction of pores with an inner diameter of 10-100 nm in amorphous carbon affects the entry of conductive agents. The electronic conductivity of amorphous carbon is generally lower than that of conductive agents. When conductive agents enter the pores of amorphous carbon with an inner diameter of 10-100 nm, the electron transport of amorphous carbon can be significantly improved. Increasing the carbon ratio helps improve the kinetics and cycle performance of the battery; however, if the carbon ratio is too high, it will affect the ability of the micropores of amorphous carbon to store ions, leading to a decrease in the capacity of amorphous carbon and thus a decrease in the energy density of the battery.

[0028] In some alternative embodiments, the amorphous carbon satisfies: 17% ≤ A ≤ 27%.

[0029] In some alternative embodiments, the amorphous carbon satisfies: 16% ≤ B ≤ 24%.

[0030] In some alternative embodiments, the amorphous carbon satisfies: 59% ≤ C ≤ 66%.

[0031] In one specific embodiment, the amorphous carbon satisfies: A = 17.2%, B = 23.5%, and C = 59.3%.

[0032] In one specific embodiment, the amorphous carbon satisfies: A = 10%, B = 23.5%, and C = 66.5%.

[0033] In one specific embodiment, the amorphous carbon satisfies: A = 30%, B = 23.5%, and C = 46.5%.

[0034] In one specific embodiment, the amorphous carbon satisfies: A = 17.2%, B = 10%, and C = 72.8%.

[0035] In one specific embodiment, the amorphous carbon satisfies: A = 17.2%, B = 30%, and C = 52.8%.

[0036] In one specific embodiment, the amorphous carbon satisfies: A = 17.2%, B = 32.8%, and C = 50%.

[0037] In one specific embodiment, the amorphous carbon satisfies: A = 17.2%, B = 12.8%, and C = 70%.

[0038] In one specific embodiment, the amorphous carbon satisfies: A = 26.2%, B = 19.2%, and C = 54.6%.

[0039] In one specific embodiment, the amorphous carbon satisfies: A = 18%, B = 16.9%, and C = 65.1%.

[0040] In one specific embodiment, the amorphous carbon satisfies: A = 23.4%, B = 16.2%, and C = 60.4%.

[0041] In one specific embodiment, the amorphous carbon satisfies: A = 10%, B = 24.3%, and C = 65.7%.

[0042] In one specific embodiment, the amorphous carbon satisfies: A = 30%, B = 18.4%, and C = 51.6%.

[0043] In one specific embodiment, the amorphous carbon satisfies: A = 26.4%, B = 10%, and C = 63.6%.

[0044] In one specific embodiment, the amorphous carbon satisfies: A = 18.4%, B = 30%, and C = 51.6%.

[0045] In one specific embodiment, the amorphous carbon satisfies: A = 25.3%, B = 24.7%, and C = 50%.

[0046] In one specific embodiment, the amorphous carbon satisfies: A = 13.2%, B = 16.8%, and C = 70%.

[0047] In this invention, the testing methods for A, B, and C can be carried out using the following steps: Take an appropriate amount of amorphous carbon sample and place it in a 9mm sample tube with a ball, degas at 300℃ for 2 hours, use nitrogen as the adsorbate (P / P0 range is 0 to 1, where 0 to 0.05 means selecting one point every 0.002, and 0.05 to 1 means selecting one point every 0.05), determine the adsorption amount of the sample, obtain the pore volume of different pore size ranges by using the NLDFT (Nonlocal Density Functional Theory) method, calculate the pore volume ratios A, B, and C, and at the same time obtain the average pore diameter D1 of pores with pore sizes of 10-100nm.

[0048] Electrochemical device

[0049] In the electrochemical device according to the second aspect of the present invention, it includes a negative electrode sheet, the negative electrode sheet including a current collector and a negative electrode material layer located on the current collector, the negative electrode material layer including the negative electrode active material and the conductive agent as described above, wherein the amorphous carbon and the conductive agent satisfy the following conditions:

[0050] 1≤D1 / D2≤10, where D1 is the average pore diameter of the pores with a diameter of 10-100nm in the amorphous carbon, and D2 is the particle size of the conductive agent.

[0051] In this invention, the average pore size refers to the average pore size formed by pores with a diameter of 10-100 nm formed by all amorphous carbon as a whole.

[0052] The inventors believe that when D1 / D2 is too small, most of the conductive agent is distributed on the surface and between particles of amorphous carbon, making it difficult to enter the pores with a diameter of 10-100 nm inside the amorphous carbon. This affects the kinetics of the amorphous carbon and consequently the cycle performance of the battery. When D1 / D2 is too large, the average pore size of the pores with a diameter of 10-100 nm in the amorphous carbon is too large, and the conductive agent is prone to agglomerate inside the pores, resulting in poor dispersion and thus affecting the conductivity and causing a decrease in the cycle performance of the battery.

[0053] In this invention, the D2 test method can be carried out by the following steps: prepare a conductive agent sample, observe it under a transmission electron microscope, select more than 100 particles in any area, count the diameter of each particle, and calculate the average diameter, which is the particle size of the conductive agent (the counted particles are single particles, and agglomerated particles need to be counted as monomers).

[0054] In some alternative embodiments, the amorphous carbon and the conductive agent satisfy 1 ≤ D1 / D2 ≤ 3.

[0055] In some alternative implementations, D1 is 20-98nm and D2 is 5-75nm.

[0056] In some alternative embodiments, the weight ratio of the amorphous carbon to the conductive agent is (10-200):1.

[0057] In some optional embodiments, the negative electrode material layer comprises: the negative electrode active material having a content of 85.0 wt%-99.8 wt%; and the conductive agent having a content of 0.1 wt%-10 wt%. Alternatively, the negative electrode material layer further comprises a binder having a content of 0.1 wt%-5 wt%. Wherein, the content in the negative electrode material layer refers to the weight percentage of each component in the negative electrode material layer.

[0058] In this embodiment of the invention, the conductive agent can be a conductive agent conventionally used in the art to prepare a negative electrode. Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes and graphene, and more preferably conductive carbon black.

[0059] In this embodiment of the invention, the binder may be a binder conventionally used in the art for preparing negative electrodes. For example, one or more of the following materials may be used as binders: SBR, PAA, CMC and PVDF.

[0060] Alternatively, the negative electrode material layer may further include a thickener.

[0061] There are no particular restrictions on the thickener. The addition of the thickener can increase the viscosity of the system of each component in the negative electrode active material layer. Generally, sodium carboxymethyl cellulose (CMC) solution can be selected.

[0062] In one specific embodiment of the present invention, the negative electrode material layer comprises: amorphous hard carbon, conductive carbon black, thickener sodium carboxymethyl cellulose, and binder styrene-butadiene rubber.

[0063] In one specific embodiment of the present invention, the negative electrode material layer comprises: 96 wt% hard carbon, 0.5 wt% carbon black, 1.17 wt% sodium carboxymethyl cellulose, and 2.33 wt% styrene-butadiene rubber.

[0064] In one specific embodiment of the present invention, the negative electrode material layer comprises: 80 wt% hard carbon, 15 wt% carbon black, 1.67 wt% sodium carboxymethyl cellulose, and 3.33 wt% styrene-butadiene rubber.

[0065] In one specific embodiment of the present invention, the negative electrode material layer comprises: 99.95 wt% hard carbon and 0.05 wt% carbon black.

[0066] In this invention, the current collector can be a conventional current collector used for negative electrodes, and can be a common current collector or a composite current collector. The current collector can be made of a non-chemically reactive and conductive material, without restriction, according to the actual needs of the electrochemical device. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum-cadmium alloys can be used, or copper, stainless steel, or aluminum-cadmium alloys surface-treated with carbon, nickel, titanium, or silver. Furthermore, to enhance the adhesion of the negative electrode active material, micro-embossing can be formed on the surface of the negative electrode current collector. The negative electrode current collector can be used in various forms, such as membranes, sheets, foils, meshes, or porous bodies.

[0067] The thickness of the current collector is, for example, 16 μm.

[0068] In this invention, the negative electrode sheet can be prepared using conventional methods in the art. For example, the following method can be used: amorphous carbon, conductive agent, thickener and binder are mixed in a certain weight ratio, and then a solvent is added and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on a current collector; and then the negative electrode sheet is prepared by processes such as drying, rolling, and cutting.

[0069] In this invention, the electrochemical device can generally be a conventional device in the art containing the negative electrode as described above, such as a secondary battery or a capacitor.

[0070] Optionally, in one specific embodiment of the present invention, the electrochemical device is a sodium-ion battery, which includes the aforementioned negative electrode, positive electrode, separator, and electrolyte.

[0071] In some implementations, the positive electrode sheet is prepared by coating a positive electrode active material, including a positive electrode active material, onto a positive electrode current collector. If necessary, binders, conductive agents, and thickeners may be further added.

[0072] The positive electrode current collector can be any current collector conventionally used for positive electrodes in this field, and can be a common current collector or a composite current collector. The positive electrode current collector can be made of a material that does not cause chemical changes and has high conductivity, without restriction, according to the actual needs of the electrochemical device. For example, commonly used materials include stainless steel, aluminum, nickel, titanium, or calcined carbon, or aluminum or stainless steel materials surface-treated with carbon, nickel, titanium, silver, etc. To enhance the adhesion of the positive electrode active material, micro-embossing can be formed on the surface of the positive electrode current collector. The positive electrode current collector can be used in various forms, such as membranes, sheets, foils, meshes, or porous bodies.

[0073] In some implementations, the separator may be a polypropylene separator or a polyethylene separator.

[0074] The thickness of the isolation membrane can be 9 μm.

[0075] In a preferred embodiment, the separator is a 9μm polyethylene separator with a 2μm thick ceramic coating on both sides.

[0076] In some embodiments, the electrolyte may be a conventional electrolyte used in batteries in the art, generally including non-aqueous solvents, sodium salts, and additives.

[0077] The non-aqueous solvent may be a conventional non-aqueous solvent in the art, preferably an ester solvent, and more preferably a carbonate solvent. The carbonate solvent may be one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0078] The additive may be selected from one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene ethylene carbonate (VEC), vinyl sulfate (DTD), vinylene sulfate, 1,3-propane sulfonyl lactone (PS), propylene sulfonyl lactone, and 1,4-butane sulfonyl lactone.

[0079] The sodium salt may be a conventional sodium salt in the art, such as NaPF6.

[0080] In this invention, the method for preparing the sodium-ion battery can be a conventional method in the art, which can be to wind the positive electrode, the negative electrode and the separator to obtain a battery cell, then package it in a packaging shell and inject the electrolyte; or it can be to stack the negative electrode, the separator, the positive electrode and the separator in sequence to obtain a battery cell, then package it in a packaging shell and inject the electrolyte.

[0081] Based on common knowledge in the field, the above optional conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0082] electronic devices

[0083] The electronic device described in the third aspect of the present invention includes the above-described electrochemical device.

[0084] In this invention, the electronic device may be, but is not limited to, mobile devices (such as mobile phones, tablets, laptops, video recorders, portable printers / copiers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems and backup power supplies, etc.

[0085] Examples 1-20 and Comparative Examples 1-11

[0086] Preparation of amorphous carbon

[0087] The amorphous carbon in Examples 1-20 and Comparative Examples 1-11 is hard carbon, and its preparation method adopts the following steps:

[0088] Coconut shells were washed three times with a mixture of water and ethanol (volume ratio 1:1), then filtered, dried, and ground to obtain a coconut shell precursor. The coconut shell precursor was placed in a crucible and heated to 200-600℃ at 1-10℃ / min under a nitrogen atmosphere, and held for 2-10 h to obtain a carbon precursor. The carbon precursor was washed three times with nitric acid / hydrochloric acid / hydrofluoric acid (volume ratio 1:1:1), then washed more than five times with deionized water, and dried to obtain a hard carbon precursor. The hard carbon precursor was heated to 1000-1500℃ at 1-10℃ / min under a nitrogen atmosphere and held for 2-10 h. Then it was ball-milled to the desired particle size to obtain amorphous carbon, which is hard carbon.

[0089] Amorphous carbon with different pore volume distributions in Examples 1-20 and Comparative Examples 1-11 was obtained by adjusting the specific parameters of the above process. The relevant parameters of the amorphous carbon in Examples 1-20 and Comparative Examples 1-11 are listed in Table 1 below.

[0090] The method for testing the pore volume and pore size of amorphous carbon is as follows: A suitable amount of amorphous carbon sample is placed in a 9 mm sample tube with a ball, degassed at 300℃ for 2 h, and nitrogen is used as the adsorbate (P / P0 range is 0 to 1, where 0 to 0.05 is a point selected every 0.002, and 0.05 to 1 is a point selected every 0.05). The adsorption amount of the sample is measured, and the pore volume in different pore size ranges is obtained by NLDFT method. The pore volume ratios A, B, and C are calculated, and the average pore size D1 of pores with a pore size of 10 to 100 nm is obtained.

[0091] Test method for conductive agent particle size: Prepare a sample of conductive agent and observe it under a scanning electron microscope. Select any area with more than 100 particles, count the diameter of each particle, and calculate the average diameter, which is the particle size of the conductive agent (the counted particles are single particles; aggregated particles need to be counted as monomers).

[0092] The conductive agent used in Examples 1-20 and Comparative Examples 1-10 is TIMICAL SUPER P Li.

[0093] Preparation of negative electrode

[0094] The preparation methods of the negative electrode sheets in Examples 1-20 and Comparative Examples 1-11 (the relevant parameters of amorphous carbon and conductive agent in Examples 1-20 and Comparative Examples 1-11, as well as the quantitative relationship between them, are listed in Table 1) adopt the following steps:

[0095] According to the dosages in Table 1, amorphous carbon, conductive agent, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of (90-100):(1-5):1:2. Deionized water was added as a solvent, and the mixture was stirred until homogeneous to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a 16μm aluminum foil current collector. After drying, rolling, and cutting processes, negative electrode sheets of Examples 1-20 and Comparative Examples 1-11 were prepared.

[0096] Table 1

[0097]

[0098]

[0099]

[0100] Example 1

[0101] (1) Preparation of sodium-ion batteries:

[0102] Preparation of the positive electrode: O3-type layered positive electrode material NaNi 0.34 Fe 0.33 Mn 0.33 O2, conductive carbon black (Super P), carbon nanotubes (CNTs), and binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of (90-100):2:1:3. N-methylpyrrolidone (NMP) solvent is added, and the mixture is stirred until homogeneous to obtain the positive electrode slurry. The positive electrode slurry is then uniformly coated onto a 16μm aluminum foil current collector. After drying, rolling, and cutting, the positive electrode sheet is prepared.

[0103] Preparation of electrolyte: Ethyl carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and propylene carbonate (PC) are mixed uniformly in a volume ratio of 1:1:1:1. Then, dry high-purity sodium salt NaPF6 is dissolved in the above mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0104] Preparation of the diaphragm: The diaphragm is a 9μm polyethylene diaphragm with a ceramic coating of 2μm thickness on both sides.

[0105] Preparation of sodium-ion batteries: The prepared positive electrode, separator, negative electrode of Examples 1-20 and Comparative Examples 1-11 and electrolyte are assembled in sequence, and the positive electrode, separator, negative electrode of Examples 1-20 and Comparative Examples 1-11 and separator are alternately combined, and a soft pack battery with a capacity of 1Ah is obtained after formation.

[0106] (2) The sodium-ion batteries prepared according to the above method in Examples 1-20 and Comparative Examples 1-11 were tested as follows:

[0107] Test method for sodium-ion battery 2C rate retention: Under constant temperature of 25℃, charge at a constant current and constant voltage of 0.33C to 4.0V (constant voltage cutoff current is 0.05C), then discharge at a constant current of 0.33C to 1.5V, obtaining the 0.33C capacity. Then charge at a constant current and constant voltage of 0.33C to 4.0V (constant voltage cutoff current is 0.05C), then discharge at a constant current of 2C to 1.5V, obtaining the 2C capacity. The ratio of the 2C capacity to the 0.33C capacity is recorded as the 2C rate retention rate.

[0108] The test method for the energy density of sodium-ion batteries is as follows: Under a constant temperature environment of 25℃, the battery is charged to 4.0V at a constant current and constant voltage rate of 0.33C (with a constant voltage cutoff current of 0.05C), and then discharged to 1.5V at a constant current rate of 0.33C, yielding 0.33C energy. The weight of the battery cell is measured using a balance. The ratio of 0.33C energy to the cell weight is the energy density.

[0109] Test method for 1000cls cycle retention of sodium-ion batteries: Under constant temperature of 25℃, charge at a constant current and constant voltage of 0.5C to 4.0V (constant voltage cutoff current is 0.05C), then discharge at a constant current of 1C to 1.5V. This constitutes one cycle, and this process is repeated 1000 times. The ratio of the discharge capacity of the 1000th cycle to the discharge capacity of the 1st cycle is recorded as the 1000cls cycle retention.

[0110] The test results are listed in Table 2.

[0111] Table 2

[0112]

[0113]

[0114] According to the data in Table 1, the sodium-ion batteries prepared from amorphous carbon and negative electrode sheets in Examples 1-20 have a 2C rate retention rate of not less than 86.9%, an energy density of not less than 131.3 Wh / kg, and a 1000cls cycle retention rate of not less than 87.6%, indicating that they have excellent kinetic performance, energy density and cycle performance.

[0115] Based on the results of Examples 1, 10, and 11, it is evident that a weight ratio of amorphous carbon to conductive agent between (10-200):1 is more beneficial to the battery's electrical performance. For example, the weight ratios of amorphous carbon to conductive agent in Examples 10 and 11 are 5:1 and 1999:1, respectively, while the weight ratio of amorphous carbon to conductive agent in Example 1 is 192:1. Compared to Examples 10 and 11, Example 1 exhibits superior 2C rate retention, energy density, and 1000cls cycle retention.

[0116] Comparative Example 1 did not add conductive carbon black, and A, B, and C did not meet the limiting conditions. 2C had the worst rate retention, energy density, and 1000cls cycle retention.

[0117] The difference between Comparative Examples 2 and 3 and the Examples is that D1 / D2 is not within the scope of this invention. As can be seen from the data in Table 2, both excessively large and excessively small D1 / D2 are detrimental to the 2C rate retention rate and the 1000cls cycle retention rate. For example, the D1 / D2 of Comparative Example 2 is 0.7, and the conductive agent is mostly distributed on the surface and between particles of amorphous carbon. The D1 / D2 of Comparative Example 3 is 10.6, and the average pore size of the pores with a diameter of 10-100nm in amorphous carbon is too large, making it easy for the conductive agent to agglomerate inside the pores. Compared with the Examples, the 2C rate retention rate and the 1000cls cycle retention rate of Comparative Examples 2 and 3 are significantly reduced.

[0118] The difference between Comparative Examples 4 and 5 and the Examples is that the value of A is not within the range of the present invention. According to the data in Tables 1 and 2, the value of A in Comparative Example 4 is 8.5%, and its energy density is reduced from at least 131.3 Wh / kg in the Examples to 119.3 Wh / kg. Compared with the Examples, the energy density of Comparative Example 4 is significantly reduced. The value of A in Comparative Example 5 is 34.2%, and its energy density is reduced from at least 131.3 Wh / kg in the Examples to 122.7 Wh / kg. Compared with the Examples, the energy density of Comparative Example 5 is significantly reduced.

[0119] The difference between Comparative Examples 6 and 7 and the Examples is that the value of B is not within the range of the present invention. According to the data in Tables 1 and 2, the B value of Comparative Example 6 is 5.6%, and its 2C ratio retention rate and 1000cls cycle retention rate are only 82.1% and 78.4%, respectively. The B value of Comparative Example 7 is 31.8%, and its 2C ratio retention rate and 1000cls cycle retention rate are only 79.5% and 83.4%, respectively. The 2C ratio retention rate and 1000cls cycle retention rate of Comparative Examples 6 and 7 are significantly worse than those of the Examples.

[0120] The difference between Comparative Examples 8 and 9 and the Examples is that the value of C is not within the range of the present invention. According to the data in Tables 1 and 2, the C of Comparative Example 8 is 44.7%, and its 2C ratio retention rate and 1000cls cycle retention rate are only 80.2% and 79.3%, respectively. The C of Comparative Example 9 is 75.2%, and its 2C ratio retention rate and 1000cls cycle retention rate are only 81.7% and 81.3%, respectively. The 2C ratio retention rate and 1000cls cycle retention rate of Comparative Examples 8 and 9 are significantly worse than those of the Examples.

[0121] Comparative Example 10's A, B, and C are not within the scope of this invention. Their A and B are too low, and C is too high, resulting in Comparative Example 10 having poor 2C rate retention, energy density, and 1000cls cycle retention compared to the examples, at 75.3%, 118.5Wh / kg, and 76.4%, respectively.

[0122] A, B, C, and D1 / D2 of Comparative Example 11 are not within the scope of this invention. A and B are too high, C is too low, and D1 / D2 is too low. As a result, compared with the embodiment, Comparative Example 11 has poor 2C rate retention, energy density, and 1000cls cycle retention, which are 79.5%, 124.1Wh / kg, and 74.2%, respectively.

[0123] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. An electrochemical device comprising a negative electrode sheet including a current collector and a negative electrode material layer on the current collector, characterized by, The negative electrode material layer includes a negative electrode active material and a conductive agent, the negative electrode active material includes amorphous carbon, and the amorphous carbon satisfies the following conditions: 17%≤A≤27%, wherein A is the percentage of the total volume of pores with an inner diameter less than 2 nm in the total volume of pores with a diameter less than 100 nm in the amorphous carbon; 16%≤B≤24%, wherein B is the percentage of the total volume of pores with an inner diameter of 2-10 nm in the total volume of pores with a diameter less than 100 nm in the amorphous carbon; 50%≤C≤70%, wherein C is the percentage of the total volume of pores with an inner diameter of 10-100 nm in the total volume of pores with a diameter less than 100 nm in the amorphous carbon; A+B+C=100%; The amorphous carbon includes hard carbon; The amorphous carbon and the conductive agent satisfy the following conditions: 1<D1 / D2≤3, wherein D1 is the average pore diameter of pores with a diameter of 10-100 nm in the amorphous carbon, and D2 is the particle size of the conductive agent; D1 is 20-98 nm, and D2 is 5-75 nm; The content of the negative electrode active material is 85.0 wt%-99.8 wt%, and the content of the conductive agent is 0.1 wt%-10 wt%, wherein the content is the weight percentage of each component in the negative electrode material layer; The conductive agent is carbon black.

2. The electrochemical device of claim 1, wherein 59%≤C≤66%。 3. The electrochemical device of claim 1, wherein The weight ratio of the amorphous carbon to the conductive agent is (10-200):

1.

4. The electrochemical device of any one of claims 1-3, wherein, The electrochemical device is a sodium ion battery.

5. An electronic device, comprising: It includes the electrochemical device according to any one of claims 1-4. It includes the electrochemical device according to any one of claims 1-4.

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