Composite carbon material, silicon-carbon composite material, electrochemical device and electronic device

Abstract

The invention provides a composite carbon material, a silicon-carbon composite material, an electrochemical device and an electronic device, the composite carbon material comprises metal particles and a porous carbon matrix, and the particle size of the metal particles is 1-8 nm; based on the mass of the composite carbon material, the mass percentage of the metal particles is 0.1-10%. The electrochemical device provided by the invention has good cycle performance, rate capability and safety performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical technologies, and particularly to a composite carbon material, a silicon-carbon composite material, an electrochemical device, and an electronic device. Background Art

[0002] Silicon-carbon materials are a new type of material with broad application prospects. Their application in lithium-ion batteries has many advantages. For example, silicon-carbon materials have a relatively high specific capacity, which can usually reach 2000 mAh / g. In contrast, traditional graphite materials only have a specific capacity of about 370 mAh / g. This shows that silicon-carbon materials can achieve a higher energy storage density, effectively improve the energy storage capacity of lithium-ion batteries, and extend the usage time of lithium-ion batteries.

[0003] However, silicon-carbon materials still have some deficiencies in terms of conductivity. For example, the silicon-carbon materials themselves have poor conductivity, and their electron conduction ability in lithium-ion batteries is inferior to that of traditional graphite materials, which may lead to problems such as increased internal resistance and increased energy loss of lithium-ion batteries, thereby affecting the overall performance of lithium-ion batteries. Currently, the methods for improving the conductivity of silicon-carbon materials mainly include using nanocomposites, adding conductive aids, optimizing structural design, doping, and interfacial modification. However, these methods still have some challenges and defects. Summary of the Invention

[0004] The purpose of this application is to provide a composite carbon material, a silicon-carbon composite material, an electrochemical device, and an electronic device to improve the cycle performance, rate performance, and safety performance of the electrochemical device.

[0005] It should be noted that in the summary of the invention of this application, a lithium-ion battery is used as an example of the electrochemical device to explain this application, but the electrochemical device of this application is not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0006] In the first aspect of this application, a composite carbon material is provided. The composite carbon material includes metal particles and a porous carbon matrix. Among them, the particle size of the metal particles is 1 nm to 8 nm; based on the mass of the composite carbon material, the mass percentage of the metal particles is 0.1% to 10%. By regulating the mass percentage and particle size of the metal particles within the scope of this application, the metal particles can be more evenly distributed inside the porous carbon matrix, and the possibility of the metal particles agglomerating into large particles is small, which can improve the conductivity of the composite carbon material, thereby improving the cycle performance and rate performance of the electrochemical device, and can also improve the kinetic performance of the electrochemical device, improve the lithium deposition phenomenon on the negative electrode, and improve the safety performance of the electrochemical device.

[0007] In one embodiment of the present application, the metal particles include at least one of iron element, cobalt element, manganese element, gold element, silver element, nickel element, copper element, tin element or aluminum element. When the metal particles are selected from the above metal elements, the conductivity of the composite carbon material can be improved, thereby improving the cycle performance and rate performance of the electrochemical device.

[0008] In one embodiment of the present application, based on the mass of the composite carbon material, the mass percentage content of the metal particles is 0.5% to 10%. When the mass percentage content of the metal particles is within the above range, the uniformity of the distribution of the metal particles inside the porous carbon matrix can be further improved, thereby improving the cycle performance and rate performance of the electrochemical device, and can improve the kinetic performance of the electrochemical device, improve the lithium plating phenomenon of the negative electrode, and improve the safety performance of the electrochemical device.

[0009] In one embodiment of the present application, the average particle size of the composite carbon material is 2 μm to 15 μm, and the Dn10 of the composite carbon material is 0.1 μm to 5 μm. When the average particle size and Dn10 of the composite carbon material are within the above ranges, the contact property and conductivity of the composite carbon material can be improved, thereby improving the cycle performance and rate performance of the electrochemical device; on the other hand, it is beneficial to form a relatively dense solid electrolyte interface (SEI) film on the surface of the negative electrode material layer, adjust the contact degree between the electrolyte and the negative electrode material layer, and reduce the irreversible lithium loss during the cycling process of the electrochemical device, thereby improving the cycle performance of the electrochemical device.

[0010] In one embodiment of the present application, the specific surface area of the composite carbon material is 701 m 2 / g to 1999 m 2 / g. When the specific surface area of the composite carbon material is within the above range, the composite carbon material has an appropriate number of deposition sites, enabling the subsequent silicon deposition amount to have an appropriate adjustable range, improving the specific capacity of the electrochemical device; at the same time, it can reduce the possibility of the size of the deposited silicon particles changing from the nanoscale to the microscale due to excessive silicon deposition amount, reduce the volume expansion during cycling, and improve the cycle performance of the electrochemical device. Optionally, the specific surface area of the composite carbon material is 500 m 2 / g to 2201 m 2 / g.

[0011] In one embodiment of the present application, the conductivity of the composite carbon material is 5 S / cm to 200 S / cm. When the conductivity of the composite carbon material is within the above range, the composite carbon material has high conductivity, thereby improving the cycle performance and rate performance of the electrochemical device. Preferably, the conductivity of the composite carbon material is 142 S / cm to 200 S / cm.

[0012] In one embodiment of the present application, the pore volume of the composite carbon material is 0.4 cm3 / g to 1.2 cm 3 / g. When the pore volume of the composite carbon material is within the above range, the subsequent silicon deposition amount has a suitable adjustable range, improving the specific capacity and energy density of the electrochemical device. At the same time, it can improve the conductivity of the composite carbon material and enhance the cycle performance and rate performance of the electrochemical device.

[0013] In one embodiment of the present application, carbon nanotubes are provided on at least part of the metal particles. The length of the carbon nanotubes is 0.1 μm to 5 μm, and the diameter of the carbon nanotubes is 1 nm to 100 nm. When the length and diameter of the carbon nanotubes are within the above range, the conductivity of the carbon nanotubes can be utilized more fully, improving the conductivity of the silicon-carbon composite material, and thus further enhancing the rate performance and cycle performance of the electrochemical device.

[0014] The second aspect of the present application provides a silicon-carbon composite material. The silicon-carbon composite material includes silicon particles and the composite carbon material in any of the foregoing embodiments. The silicon particles are located in the pores of the composite carbon material. The conductivity of the silicon-carbon composite material is 0.1 S / cm to 3 S / cm. When the silicon-carbon composite material includes silicon particles and the composite carbon material and the conductivity of the silicon-carbon composite material is within the above range, the silicon-carbon composite material has high conductivity, improving the specific capacity, cycle performance, and rate performance of the electrochemical device.

[0015] In one embodiment of the present application, the silicon particles contain silicon microcrystals, and the grain size of the silicon microcrystals is 0.5 nm to 2 nm. When the grain size of the silicon microcrystals is within the above range, the silicon-carbon material is not prone to violent expansion during the cycling process, reducing the cycle performance attenuation caused by the pulverization of the silicon-carbon composite material during the cycling process, and thus further improving the cycle performance of the electrochemical device.

[0016] The third aspect of the present application provides an electrochemical device. The electrochemical device includes an electrolyte and a negative electrode plate. The negative electrode plate includes a negative electrode material layer, and the negative electrode material layer includes the silicon-carbon composite material in any of the foregoing embodiments. The electrochemical device of the present application has good cycle performance, rate performance, and safety performance.

[0017] In one embodiment of the present application, the electrolyte includes 1,3-propane sultone. Based on the mass of the electrolyte, the mass percentage content of 1,3-propane sultone is 1.1% to 4.5%, preferably, the mass percentage content of 1,3-propane sultone is 2% to 3.2%. When the mass percentage content of 1,3-propane sultone is within the above range, the contact degree between the electrolyte and the negative electrode material layer can be adjusted, reducing the side reaction between the electrolyte and the negative electrode material layer, and thus improving the cycle performance of the electrochemical device.

[0018] In one embodiment of the present application, the electrolyte includes vinylene sulfate. Based on the mass of the electrolyte, the mass percentage content of vinylene sulfate is from 0.01% to 1.8%, preferably from 0.1% to 0.8%. When the mass percentage content of vinylene sulfate is within the above range, a stable interface can be formed on the positive electrode, the proportion of sulfide in the cathode electrolyte interface film (CEI film) can be increased, and the oxidation resistance of the positive electrode interface can be enhanced, thereby improving the cycling performance of the electrochemical device.

[0019] The fourth aspect of the present application provides an electronic device, which includes the electrochemical device in any of the foregoing embodiments. The electronic device of the present application has good performance in use.

[0020] Advantages of the present application:

[0021] The present application provides a composite carbon material, a silicon-carbon composite material, an electrochemical device and an electronic device. The composite carbon material includes metal particles and a porous carbon matrix. Among them, the particle size of the metal particles is from 1 nm to 8 nm; based on the mass of the composite carbon material, the mass percentage content of the metal particles is from 0.1% to 10%. By controlling the mass percentage content and particle size of the metal particles within the scope of the present application, the metal particles can be more evenly distributed inside the porous carbon matrix, and the possibility of the metal particles aggregating into large particles is small, which can improve the conductivity of the composite carbon material, thereby improving the cycling performance and rate performance of the electrochemical device, and can also improve the kinetic performance of the electrochemical device, improve the lithium deposition phenomenon at the negative electrode, and improve the safety performance of the electrochemical device.

[0022] Of course, it is not necessary for any product or method implementing the present application to achieve all the above-mentioned advantages simultaneously. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and those of ordinary skill in the art can also obtain other embodiments according to these drawings.

[0024] Figure 1 It is a scanning electron microscope image of the composite carbon material in one embodiment of the present application. Detailed Embodiments

[0025] The following will clearly and completely describe the technical solutions in the present application in conjunction with the embodiments of the present application and the drawings. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0026] It should be noted that in the specific embodiments of the present application, a lithium-ion battery is taken as an example of the electrochemical device to explain the present application. However, the electrochemical device of the present application is not limited to lithium-ion batteries.

[0027] The first aspect of the present application provides a composite carbon material, which includes metal particles and a porous carbon matrix. Among them, the particle size of the metal particles is 1 nm to 8 nm; based on the mass of the composite carbon material, the mass percentage of the metal particles is 0.1% to 10%. For example, the particle size of the metal particles can be 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm or a range composed of any two of these values; the mass percentage of the metal particles can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of these values. In an embodiment of the present application, the mass percentage of the metal particles is 0.5% to 10%.

[0028] The inventors of the present application have found through research that when the composite carbon material includes metal particles and a porous carbon matrix, and the metal particles are uniformly loaded in the porous carbon matrix, the conductivity of the composite carbon material can be improved, thereby improving the cycle performance and rate performance of the electrochemical device, and can also improve the kinetic performance of the electrochemical device, improve the lithium deposition phenomenon at the negative electrode, and improve the safety performance of the electrochemical device. When the mass percentage of the metal particles is too low, for example, lower than 0.1%, the improvement of the conductivity of the composite carbon material is relatively low, and the improvement of the cycle performance and rate performance of the electrochemical device is not obvious. When the mass percentage of the metal particles is too high, for example, higher than 10%, larger-sized metal particles will be formed, resulting in silicon-rich surfaces during the subsequent silicon deposition process of the composite carbon material, thereby reducing the rate performance of the electrochemical device; and it will also cause self-discharge phenomena during the cycling of the electrochemical device, affecting the safety performance of the electrochemical device. When the particle size of the metal particles is too large, for example, larger than 8 nm, it will result in silicon-rich surfaces during the subsequent silicon deposition process of the composite carbon material, thereby reducing the rate performance of the electrochemical device; when the particle size of the metal particles is too small, for example, smaller than 1 nm, the improvement of the conductivity of the composite carbon material is relatively low, and the influence on the cycle performance and rate performance of the electrochemical device is not significant. Therefore, by controlling the mass percentage and particle size of the metal particles within the scope of the present application, the metal particles can be more evenly distributed inside the porous carbon matrix, and the possibility of the metal particles aggregating into large particles is small, which can improve the conductivity of the composite carbon material, thereby improving the cycle performance and rate performance of the electrochemical device, and can also improve the kinetic performance of the electrochemical device, improve the lithium deposition phenomenon at the negative electrode, and improve the safety performance of the electrochemical device.

[0029] In an embodiment of the present application, the metal particles include at least one of iron, cobalt, manganese, gold, silver, nickel, copper, tin, or aluminum. Preferably, the metal particles include at least one of copper, iron, cobalt, or nickel. When the metal particles are selected from the above metal elements, the conductivity of the composite carbon material can be improved, thereby improving the cycle performance and rate performance of the electrochemical device.

[0030] In an embodiment of the present application, the average particle size of the composite carbon material is 2 μm to 15 μm, and the Dn10 of the composite carbon material is 0.1 μm to 5 μm. For example, the average particle size of the composite carbon material can be 2 μm, 4 μm, 6 μm, 7 μm, 10 μm, 12 μm, 14 μm, 15 μm, or a range composed of any two of these values; the Dn10 of the composite carbon material can be 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range composed of any two of these values. The average particle size reflects the average particle size of the material, and Dn10 mainly reflects the particle size range of the ultrafine powder in the material. When the average particle size and Dn10 of the composite carbon material are within the above ranges, the composite carbon material has a high fineness, increasing the contact area between particles. The smaller powder particles have a shorter electron conduction distance, which will reduce the resistance of the material, making it easier for current to pass through. Moreover, the smaller particle size allows the powder to be more easily filled into small voids, improving the contact and conductivity of the composite carbon material, thereby improving the cycle performance and rate performance of the electrochemical device; on the other hand, a suitable particle size is conducive to forming a relatively dense solid electrolyte interface (SEI) film on the surface of the negative electrode material layer, regulating the contact degree between the electrolyte and the negative electrode material layer, reducing the irreversible lithium loss during the cycling of the electrochemical device, and thus improving the cycle performance of the electrochemical device.

[0031] In the present application, Dn10 refers to the particle size that reaches 10% cumulative quantity when measured from the smaller particle size in the particle size distribution based on the quantity of the material.

[0032] In an embodiment of the present application, the specific surface area of the composite carbon material is 500 m 2 / g to 2201 m 2 / g. For example, the specific surface area of the composite carbon material can be 500 m 2 / g, 701 m 2 / g, 900 m 2 / g, 1100 m 2 / g, 1300 m 2 / g, 1399 m 2 / g, 1400 m 2 / g, 1401 m 2 / g, 1500 m 2 / g, 1700 m2 / g, 1900 m 2 / g, 1999 m 2 / g, 2000 m 2 / g, 2201 m 2 / g or a range composed of any two of these values. In one embodiment of the present application, the specific surface area of the composite carbon material is 701 m 2 / g to 1999 m 2 / g. The reserved pore structure of the composite carbon material is mainly to provide silicon deposition sites. The number of deposition sites is positively correlated with the specific surface area of the composite carbon material and also affects the amount of silicon deposition. When the specific surface area of the composite carbon material is within the above range, the composite carbon material has an appropriate number of deposition sites, so that the subsequent amount of silicon deposition has an appropriate adjustable range, improving the specific capacity of the electrochemical device; at the same time, it can reduce the possibility that the size of the deposited silicon particles changes from the nanoscale to the micron scale due to excessive silicon deposition amount, reduce the volume expansion during the cycling process, and improve the cycling performance of the electrochemical device.

[0033] In one embodiment of the present application, the conductivity of the composite carbon material is 5 S / cm to 200 S / cm. For example, the conductivity of the composite carbon material can be 5 S / cm, 10 S / cm, 50 S / cm, 100 S / cm, 142 S / cm, 150 S / cm, 200 S / cm or a range composed of any two of these values. Preferably, the conductivity of the composite carbon material is 142 S / cm to 200 S / cm. In the present application, the conductivity of the composite carbon material is also the powder conductivity of the composite carbon material. When the conductivity of the composite carbon material is within the above range, the composite carbon material has high conductivity, thereby improving the cycling performance and rate performance of the electrochemical device.

[0034] In one embodiment of the present application, the pore volume of the composite carbon material is 0.4 cm 3 / g to 1.2 cm 3 / g. For example, the pore volume of the composite carbon material can be 0.4 cm 3 / g, 0.6 cm 3 / g, 0.8 cm 3 / g, 1.0 cm 3 / g, 1.2 cm 3 / g or a range composed of any two of these values. Under certain conditions, the pore volume of the composite carbon material is inversely proportional to its conductivity and directly proportional to the amount of silicon deposition. When the pore volume of the composite carbon material is within the above range, the subsequent amount of silicon deposition has an appropriate adjustable range, improving the specific capacity and energy density of the electrochemical device, and at the same time being able to improve the conductivity of the composite carbon material and the cycling performance and rate performance of the electrochemical device.

[0035] In an embodiment of the present application, carbon nanotubes are provided on at least part of the metal particles. The length of the carbon nanotubes is 0.1 μm to 5 μm, and the diameter of the carbon nanotubes is 1 nm to 100 nm. For example, the length of the carbon nanotubes can be 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range composed of any two of these values; the diameter of the carbon nanotubes can be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or a range composed of any two of these values. When the length and diameter of the carbon nanotubes are within the above ranges, the conductivity of the carbon nanotubes can be more fully utilized, improving the conductivity of the silicon-carbon composite material, thereby further improving the rate performance and cycling performance of the electrochemical device.

[0036] The present application does not particularly limit the preparation method of the composite carbon material, as long as the object of the present application can be achieved. For example, the preparation method of the composite carbon material may include, but is not limited to, the following steps: (1) Take a metal precursor and a carbon precursor with a mass ratio of 1:999 to 1:9, and dissolve the metal precursor in a solvent to obtain a metal precursor solution with a concentration of 0.01 mol / L to 2 mol / L; (2) Immerse the carbon precursor in the above metal precursor solution and stir for 1 h to 72 h to obtain a metal precursor / carbon precursor mixed solution; (3) Dehydrate the metal precursor / carbon precursor mixed solution to obtain a metal salt / carbon precursor material; (4) Place the metal salt / carbon precursor material in a rotary furnace, introduce an inert gas and heat-treat it at 40°C to 1200°C for 1 h to 12 h, then replace the inert gas with an active gas and heat-treat it at 700°C to 1000°C for 6 h to 36 h, and then replace the active gas with a carbon-containing gas and heat-treat it at 800°C to 1000°C for 1 h to 6 h. After crushing and grading, a composite carbon material is obtained.

[0037] In the preparation process of the above composite carbon material, the metal precursor may include, but is not limited to, at least one of nickel nitrate, iron nitrate, cobalt chloride, manganese chloride, gold chloride, silver chloride, copper chloride, aluminum chloride, and tin chloride. The metal precursor mainly provides a metal source for metal particles and a pore-forming agent for the carbon precursor. The solvent may include, but is not limited to, at least one of water, ethanol, or propanol. The carbon precursor may include, but is not limited to, at least one of water-soluble thermosetting phenolic resin, asphalt, coal, coconut shell, glucose, sucrose, starch, or cellulose. The main function of the carbon precursor is to provide a carbon source, and a composite carbon material is formed after carbonization treatment. The dehydration treatment method may include, but is not limited to, at least one of spray drying, rotary evaporation dehydration, freeze dehydration, heating dehydration, or vacuum dehydration. When spray drying is selected as the dehydration treatment method, the inlet air temperature of the spray drying is 160°C to 240°C, the outlet air temperature is 65°C to 120°C, and the feeding rate is 0.01 mL / s to 5 mL / s. The inert gas may include, but is not limited to, at least one of nitrogen or argon; the active gas may include, but is not limited to, at least one of carbon dioxide or water vapor; the carbon-containing gas may include, but is not limited to, at least one of methane, acetylene, or propylene.

[0038] The present application does not particularly limit the method for regulating the mass percentage content of metal particles, as long as the purpose of the present application can be achieved. For example, the mass percentage content of metal particles can be regulated by regulating the mass ratio of the metal precursor and the carbon precursor. Exemplarily, when the mass ratio of the metal precursor and the carbon precursor increases, the mass percentage content of metal particles increases; when the mass ratio of the metal precursor and the carbon precursor decreases, the mass percentage content of metal particles decreases.

[0039] The present application does not particularly limit the method for regulating the particle size of metal particles, as long as the purpose of the present application can be achieved. For example, the particle size of metal particles can be regulated by regulating the concentration of the metal precursor solution. Exemplarily, when the concentration of the metal precursor solution increases, the particle size of metal particles increases; when the concentration of the metal precursor solution decreases, the particle size of metal particles decreases.

[0040] The present application does not particularly limit the method for regulating Dn10 of the composite carbon material, as long as the purpose of the present application can be achieved. For example, composite carbon materials with different Dn10 can be obtained by classification, and the Dn10 of the composite carbon material can be tested by combining the test method of "testing Dn10 of the composite carbon material" in the present application, and the composite carbon material with the required Dn10 can be selected.

[0041] The present application does not particularly limit the method for regulating the average particle size of the composite carbon material, as long as the purpose of the present application can be achieved. For example, composite carbon materials with different average particle sizes can be obtained by classification.

[0042] The method for regulating the specific surface area of the composite carbon material in this application is not particularly limited as long as the purpose of this application can be achieved. For example, composite carbon materials with different specific surface areas can be obtained through classification, and the specific surface area of the composite carbon material can be measured by combining the "specific surface area and pore volume measurement" method in this application, and the composite carbon material with the required specific surface area can be selected.

[0043] The method for regulating the electrical conductivity of the composite carbon material in this application is not particularly limited as long as the purpose of this application can be achieved. For example, the electrical conductivity of the composite carbon material can be regulated by controlling the mass percentage content of metal particles. Exemplarily, when the mass percentage content of metal particles increases, the electrical conductivity of the composite carbon material increases; when the mass percentage content of metal particles decreases, the electrical conductivity of the composite carbon material decreases.

[0044] The method for regulating the pore volume of the composite carbon material in this application is not particularly limited as long as the purpose of this application can be achieved. For example, the pore volume of the composite carbon material can be regulated by controlling the heating time and / or temperature of the metal salt / carbon precursor material in a box furnace. Exemplarily, when the heating time and / or temperature increases, the pore volume of the composite carbon material increases; when the heating time and / or temperature decreases, the pore volume of the composite carbon material decreases.

[0045] The method for regulating the length of carbon nanotubes on metal particles in this application is not particularly limited as long as the purpose of this application can be achieved. For example, the length of carbon nanotubes on metal particles can be regulated by controlling the time of introducing carbon-containing gas. Exemplarily, when the time of introducing carbon-containing gas increases, the length of carbon nanotubes increases; when the time of introducing carbon-containing gas shortens, the length of carbon nanotubes decreases.

[0046] The method for regulating the diameter of carbon nanotubes on metal particles in this application is not particularly limited as long as the purpose of this application can be achieved. For example, the diameter of carbon nanotubes on metal particles can be regulated by controlling the particle size of metal particles. Exemplarily, when the particle size of metal particles increases, the diameter of carbon nanotubes increases; when the particle size of metal particles decreases, the diameter of carbon nanotubes decreases.

[0047] The second aspect of the present application provides a silicon-carbon composite material, which includes silicon particles and the composite carbon material in any of the foregoing embodiments. The silicon particles are located in the pores of the composite carbon material, and the conductivity of the silicon-carbon composite material is from 0.1 S / cm to 3 S / cm. For example, the conductivity of the silicon-carbon composite material can be 0.1 S / cm, 0.5 S / cm, 1 S / cm, 2 S / cm, 3 S / cm, or a range composed of any two of these values. In the present application, the conductivity of the silicon-carbon composite material is the powder conductivity of the silicon-carbon composite material. When the silicon-carbon composite material includes silicon particles and the composite carbon material and the conductivity of the silicon-carbon composite material is within the above range, the silicon-carbon composite material has high conductivity, improving the specific capacity, cycle performance, and rate performance of the electrochemical device.

[0048] In one embodiment of the present application, based on the mass of the silicon-carbon composite material, the mass percentage of the silicon particles is from 6% to 55%. For example, the mass percentage of the silicon particles can be 6%, 10%, 20%, 30%, 40%, 50%, 55%, or a range composed of any two of these values. When the mass percentage of the silicon particles is within the above range, the specific capacity of the electrochemical device can be improved.

[0049] In one embodiment of the present application, based on the mass of the silicon-carbon composite material, the mass percentage of the composite carbon material is from 45% to 94%. For example, the mass percentage of the composite carbon material can be 45%, 50%, 60%, 70%, 80%, 90%, 94%, or a range composed of any two of these values.

[0050] In one embodiment of the present application, the silicon particles contain silicon microcrystals, and the grain size of the silicon microcrystals is from 0.5 nm to 2 nm. For example, the grain size of the silicon microcrystals can be 0.5 nm, 0.7 nm, 0.9 nm, 1.1 nm, 1.3 nm, 1.5 nm, 1.7 nm, 1.9 nm, 2 nm, or a range composed of any two of these values. When the grain size of the silicon microcrystals is within the above range, the silicon-carbon composite material is not prone to severe expansion during cycling, reducing the attenuation of the cycle performance caused by the pulverization of the silicon-carbon composite material during cycling, thereby further improving the cycle performance of the electrochemical device.

[0051] The present application does not particularly limit the preparation method of the silicon-carbon composite material, as long as the object of the present application can be achieved. For example, the preparation method of the silicon-carbon composite material may include, but is not limited to, the following steps: placing the composite carbon material in a deposition furnace, introducing a first gas at 400°C to 600°C for 0.5 h to 24 h, then introducing nitrogen for gas washing for 0.1 h to 2 h, and then introducing a second gas. After repeating gas phase deposition and gas washing 2 to 4 times, a silicon-carbon composite material is obtained. Among them, the first gas includes a silicon source gas and an inert gas. Based on the volume of the first gas, the volume percentage of the silicon source gas is 5 vt% to 10 vt%; the second gas includes a silicon source gas and an inert gas. Based on the volume of the second gas, the volume percentage of the silicon source gas is 0.5 vt% to 1 vt%; the above-mentioned silicon source gas may include, but is not limited to, at least one of silane, dichlorosilane, trichlorosilane, or silicon tetrachloride, and the above-mentioned inert gas may include, but is not limited to, at least one of argon, helium, or nitrogen.

[0052] The present application does not particularly limit the method for regulating the conductivity of the silicon-carbon composite material, as long as the object of the present application can be achieved. For example, the conductivity of the silicon-carbon composite material can be regulated by regulating the mass percentage of silicon particles. Exemplarily, when the mass percentage of silicon particles increases, the conductivity of the silicon-carbon composite material decreases; when the mass percentage of silicon particles decreases, the conductivity of the silicon-carbon composite material increases.

[0053] The present application does not particularly limit the method for regulating the grain size of silicon microcrystals, as long as the object of the present application can be achieved. For example, the grain size of silicon microcrystals can be regulated by regulating the pore volume of the composite carbon material. When the pore volume of the composite carbon material increases, the grain size of silicon microcrystals increases; when the pore volume of the composite carbon material decreases, the grain size of silicon microcrystals decreases.

[0054] The third aspect of the present application provides an electrochemical device, which includes an electrolyte and a negative electrode sheet. The negative electrode sheet includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes the silicon-carbon composite material in any of the foregoing embodiments. The electrochemical device of the present application has good cycle performance, rate performance, and safety performance.

[0055] In an embodiment of the present application, the electrolyte includes 1,3 - propane sultone. Based on the mass of the electrolyte, the mass percentage of 1,3 - propane sultone is 1.1% to 4.5%, preferably, the mass percentage of 1,3 - propane sultone is 2% to 3.2%. For example, the mass percentage of 1,3 - propane sultone can be 1.1%, 1.5%, 2%, 2.5%, 3%, 3.2%, 3.5%, 4%, 4.5% or a range composed of any two of these values. When the mass percentage of 1,3 - propane sultone is within the above range, a relatively stable SEI film can be formed on the surface of the negative electrode material layer; and the SEI film contains an organic polymer component, which adjusts the contact degree between the electrolyte and the negative electrode material layer, reduces the side reactions between the electrolyte and the negative electrode material layer, thereby improving the cycling performance of the electrochemical device.

[0056] In an embodiment of the present application, the electrolyte includes vinylene sulfate. Based on the mass of the electrolyte, the mass percentage of vinylene sulfate is 0.01% to 1.8%, preferably, the mass percentage of vinylene sulfate is 0.1% to 0.8%. For example, the mass percentage of vinylene sulfate can be 0.01%, 0.1%, 0.3%, 0.5%, 0.7%, 0.8%, 0.9%, 1.1%, 1.3%, 1.5%, 1.8% or a range composed of any two of these values. When the mass percentage of vinylene sulfate is within the above range, vinylene sulfate can form a stable interface on the positive electrode, increase the proportion of sulfides in the cathode electrolyte interface film (CEI film), enhance the oxidation resistance of the positive electrode interface, thereby improving the cycling performance of the electrochemical device.

[0057] In the present application, the electrolyte includes a lithium salt and a non - aqueous solvent. The present application places no particular limitation on the lithium salt, as long as the object of the present application can be achieved. For example, the lithium salt can include but is not limited to at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB) or lithium difluoroborate. The present application places no particular limitation on the mass percentage of the lithium salt in the electrolyte, as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage of the lithium salt can be 8% to 20%.

[0058] The non-aqueous solvent of the present application is not particularly limited as long as the object of the present application can be achieved. For example, the non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents. The above carbonate compounds may include, but are not limited to, at least one of linear carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The above linear carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The above cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene ethylene carbonate (VEC). The above fluorinated carbonate compounds may include, but are not limited to, at least one of 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. The above carboxylate compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, or caprolactone. The above ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, methylcyclobutanesulfone, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application has no particular limitation on the mass percentage content of the non-aqueous solvent in the electrolyte as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage content of the non-aqueous solvent may be 73.7% to 92%.

[0059] In one embodiment of the present application, the electrolyte may include a lithium salt and a non-aqueous solvent. The mass percentage content of the lithium salt is as described above, and the mass percentage content of the non-aqueous solvent is 80% to 92%. The electrochemical device including the above electrolyte has good kinetic performance, cycling performance, and rate performance.

[0060] In an embodiment of the present application, the electrolyte may include 1,3 - propane sultone, a lithium salt, and a non - aqueous solvent. The mass percentage contents of 1,3 - propane sultone and the lithium salt are as described above, and the mass percentage content of the non - aqueous solvent is 75.5% to 90.9%. The electrochemical device including the above - mentioned electrolyte has good kinetic performance, cycling performance, and rate performance.

[0061] In an embodiment of the present application, the electrolyte may include vinylene sulfate, a lithium salt, and a non - aqueous solvent. The mass percentage contents of vinylene sulfate and the lithium salt are as described above, and the mass percentage content of the non - aqueous solvent is 78.2% to 91.9%. The electrochemical device including the above - mentioned electrolyte has good kinetic performance, cycling performance, and rate performance.

[0062] In an embodiment of the present application, the electrolyte may include 1,3 - propane sultone, vinylene sulfate, a lithium salt, and a non - aqueous solvent. The mass percentage contents of vinylene sulfate, 1,3 - propane sultone, and the lithium salt are as described above, and the mass percentage content of the non - aqueous solvent is 73.7% to 90.8%. The electrochemical device including the above - mentioned electrolyte has good kinetic performance, cycling performance, and rate performance.

[0063] In the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above - mentioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer may be disposed on one surface of the negative electrode current collector along its thickness direction, or may be disposed on both surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here may be the entire area of the surface of the negative electrode current collector or a partial area of the surface of the negative electrode current collector. There is no special limitation in the present application as long as the purpose of the present application can be achieved.

[0064] The present application has no special limitation on the negative electrode current collector as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, lithium - copper composite current collector, carbon - copper composite current collector, nickel - copper composite current collector, or titanium - copper composite current collector, etc.

[0065] In some embodiments of the present application, the negative electrode material layer may further include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the objectives of the present application can be achieved. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials, or conductive polymers. The above-mentioned conductive carbon black may include, but is not limited to, at least one of Super P, acetylene black, or Ketjen black. The above-mentioned carbon nanotubes may include, but is not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include, but is not limited to, vapor-grown carbon fibers (VGCF) and / or nanofibers. The above-mentioned metal materials may include, but is not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above-mentioned conductive polymers may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylic acid, methyl polyacrylate, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamideimide, polyvinylidene fluoride, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0066] The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer. Those skilled in the art can select according to actual needs as long as the objectives of the present application can be achieved.

[0067] In some embodiments of the present application, the negative electrode material layer may further include a conductive agent, a binder, and a thickening agent. The present application does not particularly limit the types of the conductive agent, the binder, and the thickening agent, as long as the objectives of the present application can be achieved. For example, the conductive agent and the binder may be at least one of the aforementioned conductive agents and the aforementioned binders. The thickening agent may include, but is not limited to, at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, or lithium carboxymethyl cellulose. The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, the binder, and the thickening agent in the negative electrode material layer. Those skilled in the art can select according to actual needs as long as the objectives of the present application can be achieved.

[0068] The present application does not particularly limit the thickness of the negative electrode material layer, as long as the objectives of the present application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 120 μm.

[0069] The present application does not particularly limit the thickness of the negative electrode current collector, as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0070] Optionally, the negative electrode sheet may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application does not particularly limit the composition of the conductive layer, and it may be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and the binder in the conductive layer. For example, it may be at least one of the aforementioned conductive agents and the aforementioned binders.

[0071] In the present application, the electrochemical device includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer may be provided on one surface of the positive electrode current collector along its own thickness direction, or may be provided on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the positive electrode current collector surface or a partial area of the positive electrode current collector surface. The present application does not particularly limit it, as long as the object of the present application can be achieved.

[0072] The present application does not particularly limit the positive electrode current collector, as long as the object of the present application can be achieved. For example, a metal foil or a composite current collector may be used. For example, the metal foil may include, but is not limited to, aluminum foil; the composite current collector may be obtained by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0073] In the present application, the positive electrode material layer includes a positive electrode active material. The present application does not particularly limit the positive electrode active material, as long as the object of the present application can be achieved. For example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, lithium titanate, lithium nickel manganese aluminate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, or at least one of spinel-type lithium nickel manganese oxide.

[0074] In the present application, the positive electrode material layer may further include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the object of the present application can be achieved. For example, it may be at least one of the aforementioned conductive agents and the aforementioned binders. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the object of the present application can be achieved.

[0075] There is no particular limitation on the thickness of the positive current collector and the positive electrode material layer in this application, as long as the object of this application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer is 30 μm to 150 μm.

[0076] Optionally, the positive electrode sheet may further include a conductive layer, and the conductive layer is located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. There is no particular limitation on the conductive agent and the binder in the conductive layer of this application. For example, it may be at least one of the aforementioned conductive agents and the aforementioned binders.

[0077] In this application, the electrochemical device further includes a separator. There is no particular limitation on the separator in this application, as long as the object of this application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of the separator may include at least one of a woven film, a non-woven film, a microporous film, a composite film, a calendared film or a spun film.

[0078] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, 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 may be used.

[0079] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. In some embodiments of this application, the inorganic layer includes inorganic particles and a binder. There is no particular limitation on the inorganic particles in this application. For example, the inorganic particles may include at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. There is no particular limitation on the binder in this application. For example, the binder may be at least one of the aforementioned binders. In some embodiments of this application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0080] In the present application, the thickness of the separator film is not particularly limited, as long as the object of the present application can be achieved. For example, the thickness of the separator film can be 3 μm to 30 μm.

[0081] In the present application, the electrochemical device further includes a housing for accommodating the positive electrode plate, the separator film, the negative electrode plate, and the electrolyte, as well as other components known in the field of electrochemistry. The present application does not limit the above-mentioned other components. The present application has no particular limitation on the housing, and it can be a housing well-known in the art, as long as the object of the present application can be achieved. For example, the housing can be a hard shell housing or a flexible housing. The material of the hard shell housing can be metal, and the present application does not limit the type of metal, and a metal hard shell housing known in the art can be used, as long as the object of the present application can be achieved. The flexible housing can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0082] The present application has no particular limitation on the type of the electrochemical device, and it can include any device that undergoes an electrochemical reaction. In the present application, the electrochemical device can include, but is not limited to: a lithium metal electrochemical device, a lithium ion electrochemical device (lithium ion battery), a lithium polymer electrochemical device, or a lithium ion polymer electrochemical device (lithium ion polymer battery), etc.

[0083] The preparation process of the electrochemical device of the present application is well-known to those skilled in the art, and the present application has no particular limitation. For example, the preparation process of the electrochemical device can include, but is not limited to, the following steps: stacking the positive electrode plate, the separator film, and the negative electrode plate in sequence, and performing operations such as winding and folding according to needs to obtain a wound electrode assembly, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing it to obtain the electrochemical device. Or, stacking the positive electrode plate, the separator film, and the negative electrode plate in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated electrode assembly, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing it to obtain the electrochemical device. In addition, an overcurrent protection element, a guide plate, etc. can also be placed in the housing according to needs to prevent the pressure inside the electrochemical device from rising and overcharging and overdischarging.

[0084] The fourth aspect of the present application provides an electronic device, and the electronic device includes the electrochemical device in any of the foregoing embodiments. The electronic device of the present application has good use performance.

[0085] The type of the electronic device in this application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments of this application, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset stereo, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a minidisc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0086] Examples

[0087] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of this application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0088] Testing method and device:

[0089] Test for mass percentage content of metal particles:

[0090] Cut the negative electrode plate into 10 small round pieces with a diameter of 16 mm, and scrape off the negative electrode material layer from the negative electrode current collector of a single small round piece to obtain a powder. Weigh 0.2 g of the powder, first digest the metal elements in the powder with 20 mL of 11.6 mol / L hydrochloric acid to obtain a first sample; then digest the silicon particles in the powder with 10 mL of 20 wt% hydrofluoric acid to obtain a second sample; the undigested part is the third sample. After diluting the first sample to a constant volume in a 100 mL volumetric flask with deionized water, use an inductively coupled plasma analyzer (ICP, model AVIO-200), set the radio frequency generator (RF) frequency to 40.68 MHz, the secondary argon pressure to 0.6 MPa, the radio frequency power to 1400 W, and the pump speed to 1.0 mL / min, and test the content of metal elements in the negative electrode material layer. Take the average value of the metal element contents obtained from the above 10 small round pieces to obtain the content W1 of metal elements in the negative electrode material layer. Then analyze and test the above-mentioned undigested third sample by a thermogravimetric-mass spectrometer to obtain the mass percentage content W2 of carbon elements in the composite carbon material. The mass percentage content W of metal particles based on the composite carbon material M = W1 / (W1 + W2) × 100%.

[0091] Test for length and diameter of carbon nanotubes:

[0092] Scrape the negative electrode material layer from the negative electrode current collector with a knife to obtain the negative electrode material layer powder. Bake the negative electrode material layer powder in air at 650 °C, then dissolve it in 11.6 mol / L hydrochloric acid, filter to obtain carbon nanotubes, coat the carbon nanotubes on the conductive adhesive, blow it clean, and observe using a scanning electron microscope (model: OXFORD·EDS). Randomly measure the diameters and lengths of 10 carbon nanotubes, and obtain the diameters and lengths of the carbon nanotubes after taking the average value.

[0093] Particle size test of metal particles:

[0094] Scrape the negative electrode material layer from the negative electrode current collector with a knife to obtain the negative electrode material layer powder. Thicken the particle size of the negative electrode material layer powder to 50 nm to 100 nm by focused ion beam (FIB) to prepare a thin slice suitable for transmission electron microscope (TEM) observation; then use a transmission electron microscope (model: JEM-120i) to test and obtain the TEM image, and the crystalline region can be observed from the TEM image. Then measure the interplanar spacing of the lattice fringes in the crystalline region, and obtain the metal element corresponding to the interplanar spacing by comparing with the PDF card of the metal. Then measure the diameter of the crystalline region, which is the particle size of the metal particles.

[0095] Conductivity test:

[0096] Use a conductivity tester (instrument model: Suzhou Crystal Electronics ST-2255A) to test the powder conductivity of the composite carbon material or silicon-carbon composite material. Take 5 g of the composite carbon material or silicon-carbon composite material powder sample, press and sample it with an electronic press, apply pressure up to 5000 kg ± 2 kg, and maintain it for 20 s to obtain the test sample. Place the above test sample between the electrodes of the conductivity tester, and obtain the resistance R (unit: Ω) through the voltage U and current I at both ends. The height of the test sample is h (unit: cm), and the area of the test sample S = 3.14 cm 2 , and calculate the powder conductivity of the composite carbon material or silicon-carbon composite material according to the formula powder conductivity δ = h / (S×R), and the unit is S / cm.

[0097] Specific surface area and pore volume test:

[0098] Use a fully automatic specific surface area and porosity analyzer (model: ASAP2020 HD88) to test the specific surface area and pore volume of the composite carbon material by nitrogen adsorption method.

[0099] Average particle size test of composite carbon material:

[0100] The negative electrode plate is longitudinally cut by plasma in the thickness direction and polished using argon ion polishing technology to obtain a flat cross-section. Then, a scanning electron microscope (SEM, model: OXFORD·EDS) is used to take SEM photos at a magnification of 50,000 times to observe the silicon-carbon composite material particles. Then, using image analysis software, 30 particles are randomly selected from the SEM photos, and the area of each of these particles is obtained. Next, assuming the particles are spherical, the particle size D (diameter) of each is calculated using the following formula: D = 2×(S1 / π). 1 / 2 ; where S1 is the area of the particle; and the average value of the particle sizes of the obtained 30 particles is taken as the average particle size of the silicon-carbon composite material. It can be understood that since the particle size of the composite carbon material basically does not change after depositing silicon particles, the average particle size of the silicon-carbon composite material can be regarded as the average particle size of the composite carbon material at this time.

[0101] Dn10 test of the composite carbon material:

[0102] Use a Malvern particle size analyzer (model: MasterSizer 2000) to test the Dn10 of the composite carbon material. Add 0.02 g of the composite carbon material to a 50 mL clean beaker, add 20 mL of the dispersant ethanol, and ultrasonicate in a 120 W ultrasonic cleaner for 30 min to completely disperse the composite carbon material in ethanol to obtain a sample dispersion. Use the Malvern particle size analyzer to test the above sample dispersion to obtain the Dn10 of the composite carbon material.

[0103] Test for the mass percentage of silicon particles:

[0104] Take M g of the silicon-carbon composite material, melt the silicon-carbon composite material with potassium hydroxide to convert the silicon particles into soluble silicate, and quantitatively generate potassium fluorosilicate (K2SiF6) precipitate by reacting with an excessive hydrofluoric acid solution in a nitric acid medium. After filtering and washing the potassium fluorosilicate precipitate, hydrolyze the potassium fluorosilicate precipitate in hot water to form an equal amount of hydrofluoric acid, and then titrate with a sodium hydroxide standard solution. The mass of hydrofluoric acid is obtained from the amount of the sodium hydroxide standard solution used, the mass of potassium fluorosilicate is obtained from the mass of hydrofluoric acid, the mass of silicon particles M1 is obtained from the mass of potassium fluorosilicate, and the mass percentage of silicon particles = M1 / M×100%.

[0105] Test for the grain size of silicon microcrystals:

[0106] Perform X-ray diffraction analysis test (Cu target Kα ray) on the silicon-carbon composite material using an X-ray powder diffractometer (model: POWDIX600 / 300), and calculate using the Scherrer formula for the peak at 28.5°, then the grain size of the silicon microcrystals can be obtained.

[0107] Lithium deposition analysis:

[0108] Take the lithium-ion battery under test, let it stand still for 5 minutes at a test temperature of 0°C, charge it at a constant current of 0.8C until 4.53V, then charge it at a constant voltage of 4.53V until 0.05C. At this time, the lithium-ion battery reaches a fully charged state; let it stand still for 5 minutes, and then discharge it at a constant current of 0.8C until 3.0V, and let it stand still for 5 minutes. After repeating the above charge and discharge process 10 times, fully charge the lithium-ion battery, disassemble it in a drying room, and take pictures to record the state of the negative electrode plate.

[0109] Determination of lithium plating degree: It is determined according to the state of the fully charged and disassembled negative electrode plate. When the area showing gray on the negative electrode plate < 2%, it is determined that there is no lithium plating; when the gray area on the negative electrode plate ≥ 2% and < 20%, it is determined that there is mild lithium plating; when the gray area on the negative electrode plate ≥ 20% and < 60%, it is determined that there is moderate lithium plating; when the gray area on the negative electrode plate ≥ 60%, it is determined that there is severe lithium plating.

[0110] Use the lithium plating degree to characterize the safety performance of the lithium-ion battery. The lower the lithium plating degree of the negative electrode plate, the better the safety performance of the lithium-ion battery.

[0111] Cycle performance test:

[0112] The test temperature is 25°C. Charge the lithium-ion battery at a constant current of 0.8C to 4.53V, charge it at a constant voltage of 4.53V to 0.05C. After standing still for 5 minutes, discharge it at a constant current of 0.8C to 3.0V. The discharge capacity obtained by this step is the initial capacity. Conduct charge and discharge cycle tests according to the above steps. Record the discharge capacity every 10 cycles. Take the ratio of the discharge capacity to the initial capacity to obtain the discharge capacity retention rate. Record the number of cycles when the discharge capacity retention rate of the lithium-ion battery reaches 80% at 25°C. Use the number of cycles when the discharge capacity retention rate of the lithium-ion battery reaches 80% at 25°C to characterize the cycle performance of the lithium-ion battery. The higher the number of cycles when the discharge capacity retention rate of the lithium-ion battery reaches 80% at 25°C, the better the cycle performance of the lithium-ion battery.

[0113] Rate performance test:

[0114] Under the condition of 25°C, charge the lithium-ion battery at a constant current of 0.2C to 4.53V, record the charging capacity C1 at this time, after standing still for 5 minutes, discharge it at a constant current of 0.8C to 3.0V; charge it at a constant current of 0.5C to 4.53V, record the charging capacity C2 at this time, after standing still for 5 minutes, discharge it at a constant current of 0.8C to 3.0V; charge it at a constant current of 1C to 4.53V, record the charging capacity C3 at this time, after standing still for 5 minutes, discharge it at a constant current of 0.8C to 3.0V; charge it at a constant current of 2C to 4.53V, record the charging capacity C4 at this time, after standing still for 5 minutes, discharge it at a constant current of 0.8C to 3.0V.

[0115] Capacity retention rate at 0.5C (%) = C2 / C1 × 100%.

[0116] Capacity retention rate at 1C (%) = C3 / C1 × 100%.

[0117] Capacity retention rate at 2C (%) = C4 / C1 × 100%.

[0118] The rate performance of the lithium-ion battery is characterized by the ratio of the charging capacity at different rates to the charging capacity at 0.2C. The larger the ratio of the charging capacity at different rates to the charging capacity at 0.2C, the better the rate performance of the lithium-ion battery.

[0119] Example 1-1

[0120] <Preparation of composite carbon material>

[0121] (1) Take 20 g of metal precursor nickel nitrate and 300 g of carbon precursor water-soluble thermosetting phenolic resin. Dissolve nickel nitrate in 2 L of water to form a nickel nitrate solution with a concentration of 0.034 mol / L; (2) Immerse the water-soluble thermosetting phenolic resin in the above nickel nitrate solution and stir for 5 h to obtain a nickel nitrate / water-soluble thermosetting phenolic resin mixed solution; (3) Perform dehydration treatment on the nickel nitrate / water-soluble thermosetting phenolic resin mixed solution by spray drying at an inlet air temperature of 170 °C, an outlet air temperature of 85 °C, and a feeding rate of 2 mL / s to obtain a nickel nitrate / water-soluble thermosetting phenolic resin material; (4) Put the nickel nitrate / water-soluble thermosetting phenolic resin material into a box furnace, introduce nitrogen and heat-treat at 900 °C for 6 h, replace nitrogen with carbon dioxide and heat-treat at 850 °C for 12 h, and then replace carbon dioxide with methane and heat-treat at 900 °C for 3 h. After crushing and grading, a composite carbon material is obtained.

[0122] <Preparation of silicon-carbon composite material>

[0123] Place the composite carbon material in a deposition furnace. At 500 °C, introduce the first gas for 0.5 h, then introduce nitrogen for 0.2 h for gas washing, and then introduce the second gas. Repeat gas phase deposition and gas washing 3 times to obtain a silicon-carbon composite material. Among them, the first gas includes the silicon source gas silane and the inert gas argon. Based on the volume of the first gas, the volume percentage content of the silicon source gas is 10 vt%; the second gas includes the silicon source gas silane and the inert gas argon. Based on the volume of the second gas, the volume percentage content of the silicon source gas is 0.7 vt%.

[0124] <Preparation of negative electrode plate>

[0125] The silicon-carbon composite material prepared above, conductive agent acetylene black, binder polymethyl acrylate, and thickener sodium carboxymethyl cellulose (CMC-Na) were mixed in a mass ratio of 95.7:1.5:1.8:1, and then dissolved in deionized water, the negative electrode solvent. After mixing evenly, a negative electrode slurry with a solid content of 45 wt% was prepared. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 μm, and dried at 85 °C for 4 h to obtain a negative electrode sheet with a single-sided coated negative electrode material layer. The coating weight of the negative electrode material layer was 142 mg / 1540 mm 2 。Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode material layer. After cold pressing, cutting, and slitting, it was dried under vacuum at 120 °C for 12 h to obtain a negative electrode sheet with a specification of 76.6 mm × 875 mm for use. Among them, the compaction density of the negative electrode material layer was 1.7 g / cm 3 。

[0126] <Preparation of the positive electrode sheet>

[0127] The positive electrode active material lithium cobaltate, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96.3:2.2:1.5, and then N-methylpyrrolidone, the positive electrode solvent, was added and stirred evenly to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 13 μm and dried at 85 °C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. The coating weight of the positive electrode material layer was 267.8 mg / 1540 mm 2 。Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. After cold pressing, cutting, and slitting, it was dried under vacuum at 85 °C for 4 h to obtain a positive electrode sheet with a specification of 74 mm × 867 mm for use. Among them, the compaction density of the positive electrode material layer was 4.23 g / cm 3 。

[0128] <Preparation of the electrolyte>

[0129] In a glove box under an argon atmosphere with a water content < 10 ppm, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed evenly in a volume ratio of 1:1 to obtain a basic solvent. 1,3-Propane sultone, vinylene sulfate, and lithium salt LiPF6 were added to the basic solvent and stirred evenly to obtain an electrolyte. Among them, based on the total mass of the electrolyte, the mass percentage content of 1,3-propane sultone was 3.2%, the mass percentage content of vinylene sulfate was 0.8%, the mass percentage content of the lithium salt was 12.5%, and the mass percentage content of the basic solvent was 83.5%.

[0130] <Separator membrane>

[0131] A polyethylene (PE) porous separator with a thickness of 12 μm is used.

[0132] <Preparation of Lithium-Ion Batteries>

[0133] The positive electrode plate after welding the tab, the separator, the negative electrode plate after welding the tab, and the separator are stacked in sequence, with the separator placed in the middle of the positive electrode plate and the negative electrode plate to play a role in isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film, dried in a vacuum oven at 80 °C for 12 hours to remove moisture, injected with the above-prepared electrolyte, and subjected to vacuum packaging, standing, formation (constant current charging at 0.02C to 3.5V, and then constant current charging at 0.1C to 3.9V), degassing, and trimming processes to obtain a lithium-ion battery.

[0134] Examples 1-2 to 1-3

[0135] Except that in <Preparation of Composite Carbon Materials>, the concentration of the metal precursor solution is adjusted so that the particle size of the metal particles is as shown in Table 1, and the diameter of the carbon nanotubes changes accordingly, the rest is the same as in Example 1-1.

[0136] Examples 1-4 to 1-5

[0137] Except that in <Preparation of Composite Carbon Materials>, the mass ratio of the metal precursor to the carbon precursor is adjusted so that the mass percentage of the metal particles is as shown in Table 1, and the conductivity of the composite carbon material changes accordingly, the rest is the same as in Example 1-1.

[0138] Examples 1-6 to 1-17

[0139] Except that in <Preparation of Composite Carbon Materials>, the average particle size and Dn10 of the composite carbon material are regulated by grading as shown in Table 1, the rest is the same as in Example 1-1.

[0140] Examples 1-18 to 1-21

[0141] Except that in <Preparation of Composite Carbon Materials>, the pore volume of the composite carbon material is regulated by controlling the heating time and / or temperature so that it is as shown in Table 1, and the grain size of the silicon microcrystals changes accordingly, the rest is the same as in Example 1-1.

[0142] Examples 1-22 to 1-25

[0143] Except that in <Preparation of Composite Carbon Materials>, the time for introducing the carbon-containing gas is regulated so that the length of the carbon nanotubes is as shown in Table 1, the rest is the same as in Example 1-1.

[0144] Examples 1-26 to 1-27

[0145] Except that in the <Preparation of silicon-carbon composite material>, the conductivity of the silicon-carbon composite material is shown in Table 2 by adjusting the mass percentage of silicon particles, the rest is the same as in Example 1-1.

[0146] Example 1-28

[0147] Except that in the <Preparation of composite carbon material>, manganese chloride is used as the metal precursor, the rest is the same as in Example 1-1.

[0148] Example 1-29

[0149] Except that in the <Preparation of composite carbon material>, copper chloride is used as the metal precursor, the rest is the same as in Example 1-1.

[0150] Example 1-30

[0151] Except that in the <Preparation of composite carbon material>, iron nitrate is used as the metal precursor, the rest is the same as in Example 1-1.

[0152] Example 1-31

[0153] Except that in the <Preparation of composite carbon material>, cobalt chloride is used as the metal precursor, the rest is the same as in Example 1-1.

[0154] Example 1-32

[0155] Except that in the <Preparation of composite carbon material>, iron nitrate and nickel nitrate with a mass ratio of 1:1 are used as the metal precursor, the rest is the same as in Example 1-1.

[0156] Examples 2-1 to 2-6

[0157] Except that in the <Preparation of electrolyte>, the relevant preparation parameters are adjusted according to Table 3, the rest is the same as in Example 1-1. Among them, when the mass percentage of at least one of 1,3-propane sultone or ethylene sulfate changes, the mass percentage of the base solvent changes accordingly, while the volume ratio of each component of the base solvent and the mass percentage of the lithium salt remain unchanged.

[0158] Comparative Examples 1 to 2

[0159] Except that in the <Preparation of composite carbon material>, the concentration of the metal precursor solution is adjusted so that the particle size of the metal particles is shown in Table 1, the rest is the same as in Example 1-1.

[0160] Comparative Example 3

[0161] Except that in <Preparation of Silicon-Carbon Composite Material>, a porous carbon matrix is directly used as the composite carbon material, the rest is the same as in Example 1-1. Among them, the average particle size of the porous carbon matrix is 7 μm, the Dn10 of the porous carbon matrix is 2 μm, the specific surface area of the porous carbon matrix is 1400 m 2 g, the conductivity of the porous carbon matrix is 2 S / cm, and the pore volume of the porous carbon matrix is 0.71 cm 3 / g.

[0162] Comparative Example 4

[0163] Except that in <Preparation of Composite Carbon Material>, the mass ratio of the metal precursor and the carbon precursor is adjusted so that the mass percentage content of the metal particles is as shown in Table 1, the rest is the same as in Example 1-1.

[0164]

[0165]

[0166]

[0167] It can be seen from Example 1-1 to Example 1-32 and Comparative Example 1 to Comparative Example 4 that when the particle size of the metal particles and the mass percentage content of the metal particles based on the composite carbon material are within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rate at different rates are relatively high, and there is no case of lithium deposition, indicating that the cycle performance, rate performance and safety performance of the lithium-ion battery of the present application are improved. In Comparative Example 1, Comparative Example 2 and Comparative Example 4, the particle size of the metal particles or the mass percentage content of the metal particles based on the composite carbon material is not within the scope of the present application. In Comparative Example 3, the composite carbon material of the present application is not used, and the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rate at different rates are relatively low and / or there is a case of lithium deposition on the negative electrode.

[0168] From Figure 1 It can be seen that the composite carbon material prepared by the preparation method of the present application has metal particles distributed on its surface, and carbon nanotubes are provided on the metal particles.

[0169] It can be seen from Example 1-1, Example 1-4 to Example 1-5 that when the conductivity of the composite carbon material is within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rate at different rates are relatively high, and there is no case of lithium deposition, indicating that the cycle performance, rate performance and safety performance of the lithium-ion battery of the present application are improved.

[0170] It can be seen from Examples 1-1, 1-6 to 1-13 that when the average particle size and Dn10 of the composite carbon material are within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rates at different rates are relatively high, and no lithium deposition occurs in Examples 1-1, 1-6 to 1-9, 1-11 to 1-12. Slight lithium deposition occurs in Examples 1-10 and 1-13, indicating that the cycle performance and rate performance of the lithium-ion battery of the present application are improved, and at the same time, it has good safety performance.

[0171] It can be seen from Examples 1-1, 1-14 to 1-17 that when the specific surface area of the composite carbon material is within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rates at different rates are relatively high, and no lithium deposition occurs, indicating that the cycle performance of the lithium-ion battery of the present application is improved, and at the same time, it has good rate performance and safety performance.

[0172] It can be seen from Examples 1-1, 1-18 to 1-21 that when the pore volume of the composite carbon material and the grain size of the silicon microcrystals are within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rates at different rates are relatively high, and no lithium deposition occurs in Examples 1-1, 1-19 and 1-20. Slight lithium deposition occurs in Examples 18 and 21, indicating that the cycle performance and rate performance of the lithium-ion battery of the present application are improved, and at the same time, it has good safety performance.

[0173] It can be seen from Examples 1-1 to 1-3, 1-22 to 1-25 that when the length and diameter of the carbon nanotubes are within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rates at different rates are relatively high, and no lithium deposition occurs, indicating that the cycle performance and rate performance of the lithium-ion battery of the present application are improved, and at the same time, it has good safety performance.

[0174] It can be seen from Examples 1-1, 1-28 to 1-32 that when the type of metal particles is within the scope of the present application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery at 25 °C reaches 80% and the capacity retention rates at different rates are relatively high, and no lithium deposition occurs, indicating that the cycle performance and rate performance of the lithium-ion battery of the present application are improved, and at the same time, it has good safety performance.

[0175] It can be seen from Examples 1-1, 1-4 to 1-5, 1-26 to 1-27, Comparative Example 3 and Comparative Example 4 that when the conductivity of the silicon-carbon composite material is within the scope of this application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery reaches 80% at 25°C and the capacity retention rate at different rates are relatively high, and there is no case of lithium deposition, indicating that the cycle performance, rate performance, and safety performance of the lithium-ion battery of this application have been improved. In Comparative Example 3 and Comparative Example 4, the conductivity of the silicon-carbon composite material is not within the scope of this application, and the number of cycles until the cycle capacity retention rate of the obtained lithium-ion battery reaches 80% at 25°C and the capacity retention rate at different rates are relatively low, and there is a case of moderate lithium deposition.

[0176] Table 3

[0177]

[0178] It can be seen from Examples 1-1, 2-1 to 2-3 that when the mass percentage content of 1,3-propanesultone is within the scope of this application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery reaches 80% at 25°C and the capacity retention rate at different rates are relatively high, and there is no case of lithium deposition on the negative electrode, indicating that the cycle performance, rate performance, and safety performance of the lithium-ion battery of this application have been improved.

[0179] It can be seen from Examples 1-1, 2-4 to 2-6 that when the mass percentage content of vinylene sulfate is within the scope of this application, the number of cycles until the cycle capacity retention rate of the lithium-ion battery reaches 80% at 25°C and the capacity retention rate at different rates are relatively high, and there is no case of lithium deposition, indicating that the cycle performance, rate performance, and safety performance of the lithium-ion battery of this application have been improved.

[0180] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application.

[0181] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method or article.

[0182] Each embodiment in this specification is described in a relevant manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments.

Claims

1. A composite carbon material, comprising metal particles and a porous carbon matrix, wherein: The particle size of the metal particles is 1 nm to 8 nm; based on the mass of the composite carbon material, the mass percentage of the metal particles is 0.1% to 10%.

2. The composite carbon material according to claim 1, wherein The metal particles include at least one of iron, cobalt, manganese, gold, silver, nickel, copper, tin or aluminum; and / or, The mass percentage of the metal particles is 0.5% to 10%.

3. The composite carbon material according to claim 1, wherein The average particle size of the composite carbon material is 2 μm to 15 μm, and the Dn10 of the composite carbon material is 0.1 μm to 5 μm.

4. The composite carbon material according to any one of claims 1 to 3, wherein The composite carbon material satisfies at least one of the following conditions: (1) The specific surface area of ​​the composite carbon material is 500 m 2 / g to 2201m 2 / g; (2) The electrical conductivity of the composite carbon material is 5 S / cm to 200 S / cm, preferably, the electrical conductivity of the composite carbon material is 142 S / cm to 200 S / cm; (3) The pore volume of the composite carbon material is 0.4 cm 3 / g to 1.2cm 3 / g.

5. The composite carbon material according to any one of claims 1 to 3, wherein At least a portion of the metal particles are provided with carbon nanotubes, the length of the carbon nanotubes is 0.1 μm to 5 μm, and the diameter of the carbon nanotubes is 1 nm to 100 nm.

6. A silicon-carbon composite material, comprising silicon particles and the composite carbon material according to any one of claims 1 to 5, wherein: The silicon particles are located in the pores of the composite carbon material, and the electrical conductivity of the silicon-carbon composite material is 0.1 S / cm to 3 S / cm.

7. The silicon-carbon composite material according to claim 6, wherein: The silicon particles include silicon microcrystals, and the grain size of the silicon microcrystals is 0.5 nm to 2 nm.

8. An electrochemical device, comprising an electrolyte and a negative electrode plate, wherein the negative electrode plate comprises a negative electrode material layer, and the negative electrode material layer comprises the silicon-carbon composite material according to claim 6 or 7.

9. The electrochemical device according to claim 8, wherein: The electrolyte satisfies at least one of the following conditions: (1) The electrolyte comprises 1,3-propane sultone, and the mass percentage of 1,3-propane sultone is 1.1% to 4.5% based on the mass of the electrolyte, and preferably, the mass percentage of 1,3-propane sultone is 2% to 3.2%; (2) The electrolyte includes vinyl sulfate, and the mass percentage of vinyl sulfate is 0.01% to 1.8% based on the mass of the electrolyte. Preferably, the mass percentage of vinyl sulfate is 0.1% to 0.8%.

10. An electronic device comprising the electrochemical device according to claim 8 or 9.

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