Secondary battery and electric device

Abstract

A secondary battery and an electric device. The secondary battery comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator; the positive electrode sheet comprises a positive-electrode active material layer, and the positive-electrode active material layer comprises a positive-electrode active material; the negative electrode sheet comprises a negative-electrode active material layer, and the negative-electrode active material layer comprises a negative-electrode active material; the coating weight of the positive-electrode active material layer is Wz, the coating weight of the negative-electrode active material layer is Wf, and Wz and Wf satisfy: 1.6Wf≤Wz≤2.2Wf, and 3.25 mg / cm2≤Wf≤5.84 mg / cm2; the Dv99 of the positive-electrode active material is 27 μm to 33 μm, and the Dv99 of the negative-electrode active material is 23 μm to 28 μm; and the electrolyte comprises an organic solvent, a lithium salt and a nitrile additive, the organic solvent comprises a chain carboxylic ester, and based on the mass of the electrolyte, the mass percentage content of the chain carboxylic ester is 6% to 56% and the mass percentage content of the nitrile additive is 0.01% to 10%. The secondary battery has good dynamic performance during cycling and good high-temperature stability.

Description

Secondary battery and power-consuming device Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electrical device. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have the characteristics of high specific energy, high operating voltage, low self-discharge rate, small size and light weight, and are widely used in various fields such as electrical energy storage, portable electronic devices and electric vehicles. With the continuous iterative development of consumer lithium-ion batteries in recent years, the market has higher and higher requirements for their charging speed, and the charging rate of lithium-ion batteries has continued to increase. Consumer demand has gradually increased from 1C to more than 5C. However, it is difficult to reconcile the high charging rate (5C≤charging rate≤15C) and high temperature (temperature≥60°C) stability of lithium-ion batteries. Therefore, how to improve the cycle dynamics performance of super-fast charging lithium-ion batteries while taking into account the high temperature stability of lithium-ion batteries has become a technical problem that needs to be solved urgently by those skilled in the art.

[0003] Summary of the Invention

[0004] The purpose of the present application is to provide a secondary battery that improves the cycle dynamics performance of the secondary battery while taking into account the high-temperature stability of the secondary battery, and at the same time provides an electrical device using the secondary battery.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application. However, the secondary batteries of this application are not limited to lithium-ion batteries, and can also be used for secondary batteries such as sodium-ion batteries. The specific technical solution is as follows:

[0006] The first aspect of the present application provides a secondary battery, wherein the secondary battery includes an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material; the coating weight of the positive electrode active material layer is W z The coating weight of the negative electrode active material layer is W f , W z and W f Between: 1.6W f ≤W z ≤2.2W f 、3.25mg / cm 2 ≤W f ≤5.84mg / cm 2; The Dv99 of the positive electrode active material is 27μm to 33μm, and the Dv99 of the negative electrode active material is 23μm to 28μm; the electrolyte includes an organic solvent, a lithium salt and a nitrile additive, the organic solvent includes a chain carboxylic acid ester, and based on the mass of the electrolyte, the mass percentage of the chain carboxylic acid ester is 6% to 56%, and the mass percentage of the nitrile additive is 0.01% to 10%. The positive electrode active material layer and the negative electrode active material layer adopt a lower coating weight, which can reduce the thickness of the positive electrode active material layer and the negative electrode active material layer and increase the porosity of the positive electrode active material layer and the negative electrode active material layer, thereby reducing the ohmic polarization and concentration polarization of the electrode sheet, shortening the transmission distance of lithium ions in the electrode sheet, and thereby improving the charging rate of the secondary battery; the selection of small-particle positive and negative electrode active materials improves the surface activity of the positive and negative electrode active materials, shortens the transmission distance of lithium ions inside the positive and negative electrode active material particles, and reduces the concentration polarization of the secondary battery; at the same time, the addition of chain carboxylic acid esters within the content range of this application to the electrolyte ensures that it has low viscosity to meet the requirements of rapid transmission of lithium ions during super fast charging. The above-mentioned coating weight of the positive and negative active material layers, the selection of positive and negative active material particles and electrolyte components enable the secondary battery to have high dynamics to meet the needs of super fast charging. However, the high dynamics design of the secondary battery brings the risk of high-temperature stability. Small-particle high-activity active materials are prone to side reactions with the chain carboxylates in the electrolyte. Especially at high temperatures, the side reactions will cause violent gas production inside the lithium-ion battery, resulting in deterioration of the high-temperature storage and hot box performance of the secondary battery. To this end, nitrile additives within the content range of this application are added to the electrolyte. While maintaining the high dynamics of the secondary battery, the positive and negative electrode sheets are protected, the side reactions between the electrolyte and the positive and negative electrode sheets are reduced, and the high-temperature stability of the secondary battery is improved. Therefore, the present application combines the coating weight of the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the components and content of the electrolyte, so that there is a good synergistic effect between the coating weight of the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the electrolyte, which can take into account the high temperature stability of the secondary battery on the basis of improving the cycle kinetics performance of the secondary battery.

[0007] In one embodiment of the present application, 6.49 mg / cm 2 ≤W z ≤11.69 mg / cm 2 By regulating the coating weight of the positive electrode active material layer within the scope of the present application, the present invention enables the secondary battery to have good cycle dynamics performance while taking into account high temperature stability.

[0008] In one embodiment of the present application, 3.90 mg / cm 2 ≤W f ≤5.19mg / cm2 , and / or, 7.80 mg / cm 2 ≤W z ≤10.38mg / cm 2 .W z and / or W f By regulating within the above range, the coating weight range of the positive electrode active material layer and / or the negative electrode active material layer is more optimal, which is beneficial to further improve the cycle dynamics performance of the secondary battery while taking into account the high temperature stability.

[0009] In one embodiment of the present application, the Dv99 of the positive electrode active material is 28 μm to 31 μm, and / or the Dv99 of the negative electrode active material is 24 μm to 26 μm. By regulating the Dv99 of the positive electrode active material and / or the Dv99 of the negative electrode active material within the above range, the Dv99 range of the positive electrode active material and / or the Dv99 of the negative electrode active material is more optimal, which is conducive to further improving the cycle dynamics performance and high temperature stability of the secondary battery.

[0010] In one embodiment of the present application, the Dv50 of the positive electrode active material is 10 μm to 15 μm, and the Dv50 of the negative electrode active material is 7 μm to 12 μm. Regulating the Dv50 of the positive and negative electrode active materials within the above ranges is beneficial for achieving a secondary battery with high energy density while maintaining good cycle kinetics and high-temperature stability.

[0011] In one embodiment of the present application, the negative electrode active material includes at least one of a carbon-based material, a silicon-based material, or a tin-based material. The carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesocarbon microbeads. The silicon-based material includes at least one of elemental silicon, a silicon-carbon material, or a silicon-oxygen material. The tin-based material includes at least one of elemental tin, a tin alloy, or a tin oxide. These negative electrode active materials have high surface activity, enabling the secondary battery to have good cycling kinetics while maintaining high-temperature stability.

[0012] In one embodiment of the present application, the carbon-based material is tested by Raman with a peak intensity ratio of d peak to g peak of I d / I g Satisfy: 0.1≤I d / I g ≤1.0. Will satisfy the above I d / I g The application of high-value carbon-based materials in secondary batteries is beneficial to further improve the cycle dynamics performance of secondary batteries on the basis of good high-temperature stability.

[0013] In one embodiment of the present application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, a lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. The above-mentioned positive electrode active materials have high surface activity and can enable the secondary battery to have good cycling kinetics while maintaining high-temperature stability.

[0014] In one embodiment of the present application, the positive electrode active material further includes a non-metallic element, wherein the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. Including the aforementioned non-metallic elements in the positive electrode active material can further improve the stability of the positive electrode active material. The aforementioned non-metallic elements can be added to the positive electrode active material by bulk doping or surface coating.

[0015] In one embodiment of the present application, the chain carboxylate includes at least one of methyl formate, methyl acetate, ethyl formate, ethyl acetate, propyl acetate, ethyl propionate, methyl propionate, n-propyl propionate, isopropyl propionate, methyl propionate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isopentyl propionate, ethyl butyrate, n-propyl butyrate, propyl isobutyrate, n-pentyl butyrate, n-pentyl isobutyrate, n-butyl butyrate, isobutyl isobutyrate, or n-pentyl valerate. The above-mentioned chain carboxylate has high conductivity and low viscosity, and is convenient for lithium ion transport. The use of the above-mentioned chain carboxylate can enable the secondary battery to have good cycle dynamics and high-temperature stability.

[0016] In one embodiment of the present application, the mass percentage of the chain carboxylate is 18% to 40% based on the mass of the electrolyte. By regulating the mass percentage of the chain carboxylate within this range, lithium ions are transported more rapidly in the electrolyte, thereby further improving the cycling kinetics of the secondary battery while maintaining good high-temperature stability.

[0017] In one embodiment of the present application, the nitrile additive includes at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, sebacononitrile, 3,3'-oxydipropionitrile, hexane-2-enedinitrile, fumaronitrile, 2-pentene dinitrile, methylglutaronitrile, 4-cyanopimetonitrile, (Z)-but-2-enedinitrile, 2,2,3,3-tetrafluorosuccinonitrile, ethylene glycol bis(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,3,6-hexatriconitrile, 1,2,6-hexatriconitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,1,3,3-propanetetracarbonitrile, 2,2'-(1,4-phenylene)dimalononitrile, 1,1,5,5-pentanetetracarbonitrile, 1,1,4,4-butanetetracarbonitrile or 1,1,6,6-hexatriconitrile. The selection of the above-mentioned nitrile additives is beneficial for further improving the high-temperature stability of the secondary battery on the basis of having good cycle dynamics performance.

[0018] In one embodiment of the present application, the weight percentage of the nitrile additive is 5% to 8% based on the weight of the electrolyte. Controlling the weight percentage of the nitrile additive within the above range is beneficial for further improving the high-temperature stability of the secondary battery while maintaining good cycle kinetics.

[0019] In one embodiment of the present application, the organic solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, or tetrahydrofuran; and the weight percentage of the organic solvent is 60% to 80% based on the weight of the electrolyte. Further, selecting the above organic solvents and regulating the weight percentage of the organic solvents within the above ranges is conducive to the secondary battery having good cycling dynamics and high-temperature stability.

[0020] The second aspect of the present application provides an electric device, which includes the secondary battery described in any of the above embodiments. Therefore, the electric device has good performance.

[0021] Beneficial effects of this application:

[0022] The present application provides a secondary battery and an electrical device, wherein the secondary battery regulates the coating weight of the negative electrode active material layer, the coating weight relationship between the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the components and content of the electrolyte within the scope of the present application, so that the coating weight of the negative electrode active material layer, the coating weight relationship between the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the components and content of the electrolyte have good synergistic effects, so that lithium ions have a shorter transmission path inside the positive / negative electrode active material during transmission, and have a smaller transmission tortuosity and a shorter transmission distance inside the positive / negative electrode sheets, so as to reduce the concentration polarization and electrochemical polarization of the secondary battery, and also protect the positive and negative electrode sheets, and reduce the side reactions between the electrolyte and the positive and negative electrode sheets, so as to improve the cycle kinetics performance of the secondary battery while taking into account the high temperature stability of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0024] FIG1 is a Raman spectrum of the negative electrode of Example 3-3. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It is apparent that the described examples are only a portion of the embodiments of this application, rather than all of them. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] It should be noted that in the specific embodiments of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries, and can also be used for secondary batteries such as sodium-ion batteries.

[0027] The first aspect of the present application provides a secondary battery, wherein the secondary battery includes an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material; the coating weight of the positive electrode active material layer is W z The coating weight of the negative electrode active material layer is W f , W z and W f Between: 1.6W f ≤Wz ≤2.2W f 、3.25mg / cm 2 ≤W f ≤5.84mg / cm 2 ; The Dv99 of the positive electrode active material is 27μm to 33μm, and the Dv99 of the negative electrode active material is 23μm to 28μm; the electrolyte includes an organic solvent, a lithium salt and a nitrile additive, the organic solvent includes a chain carboxylic acid ester, and based on the mass of the electrolyte, the mass percentage of the chain carboxylic acid ester is 6% to 56%, and the mass percentage of the nitrile additive is 0.01% to 10%.

[0028] For example, W f 3.25 mg / cm 2 , 3.5mg / cm 2 、3.75mg / cm 2 , 4mg / cm 2 , 4.25mg / cm 2 , 4.5mg / cm 2 , 4.75mg / cm 2 , 5mg / cm 2 , 5.25mg / cm 2 , 5.5mg / cm 2 , 5.84mg / cm 2 Or any value between any two numerical ranges mentioned above. The coating weight of the positive electrode active material layer is less than 1.6W f The coating weight of the negative electrode active material layer is too large relative to the coating weight of the positive electrode active material layer. When the potential of the secondary battery is reached, the lithium removal rate of the positive electrode increases significantly, resulting in a very high actual potential of the positive electrode and easy destruction of the structure. The positive electrode decays rapidly, resulting in the secondary battery being unable to cycle normally. The coating weight of the positive electrode active material layer is greater than 2.2W f If the coating weight of the positive electrode active material layer is too large relative to the coating weight of the negative electrode active material layer, the released lithium ions will be excessive, and the negative electrode will not be able to fully accept the released lithium ions from the positive electrode. The lithium ions cannot be properly embedded in the negative electrode sheet, which will lead to lithium deposition on the negative electrode sheet and affect the cycle dynamics performance of the secondary battery. The coating weight of the negative electrode active material layer is less than 3.25 mg / cm 2 , the energy density of the secondary battery is reduced, the service life is shortened, and it is difficult to meet the process requirements of the secondary battery; the coating weight of the negative electrode active material layer is greater than 5.84 mg / cm 2 , the transmission distance of lithium ions in the positive electrode sheet and / or the negative electrode sheet increases, and the impedance of the secondary battery increases.

[0029] For example, the Dv99 of the positive electrode active material is 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm or any value between any two of the above numerical ranges. The Dv99 of the positive electrode active material is less than 27μm. The Dv99 of the positive electrode active material is too small, indicating that the volume particle size of the positive electrode active material particles is too small. When preparing the positive electrode slurry, the positive electrode active material particles are prone to agglomeration. In this way, the probability of the positive electrode active material being uniformly dispersed in the positive electrode slurry is extremely small, and the positive electrode active material particles in the formed positive electrode active material layer are unevenly distributed, which will affect the processing stability of the positive electrode sheet and cause uneven coating problems during the coating of the positive electrode slurry. In addition, the specific surface area of ​​the positive electrode active material particles will be too large, resulting in the positive electrode active material particles and the positive electrode active material particles being unevenly distributed. As the number of electrolyte contact interfaces increases, side reactions will intensify, especially in the high-kinetic electrolyte system of super-fast charging. The side reactions will be very violent, accelerating the consumption of electrolyte and the generation of side reaction products, and worsening the cycle performance and high-temperature stability of the secondary battery; the Dv99 of the positive electrode active material is greater than 33μm. The Dv99 of the positive electrode active material is too large, the transmission path of lithium ions inside the positive electrode active material particles is too long, and the tortuosity of the transmission inside the positive electrode sheet is too large, which will lead to excessive concentration polarization inside the secondary battery, thereby increasing the internal resistance of the secondary battery and reducing the cycle kinetics performance of the secondary battery.

[0030] For example, the Dv99 of the negative electrode active material is 23μm, 24μm, 25μm, 26μm, 27μm, 28μm or any value between any two of the above numerical ranges. The Dv99 of the negative electrode active material is less than 23μm. The Dv99 of the negative electrode active material is too small, indicating that the volume particle size of the negative electrode active material particles is too small. When preparing the negative electrode slurry, the particles of the negative electrode active material are prone to agglomeration. In this way, the probability of the negative electrode active material being uniformly dispersed in the negative electrode slurry is extremely small, and the negative electrode active material particles in the formed negative electrode active material layer are unevenly distributed, which will affect the processing stability of the negative electrode sheet and cause uneven coating problems during the coating of the negative electrode slurry. In addition, the specific surface area of ​​the negative electrode active material particles will be too large, resulting in the negative electrode active material particles and the agglomeration of the negative electrode active material particles. As the number of electrolyte contact interfaces increases, side reactions will intensify, especially in the high-kinetic electrolyte system of super-fast charging. The side reactions will be very violent, accelerating the consumption of electrolyte and the generation of side reaction products, and worsening the cycle performance and high-temperature stability of the secondary battery; the Dv99 of the negative electrode active material is greater than 28μm. The Dv99 of the negative electrode active material is too large, the transmission path of lithium ions inside the negative electrode active material particles is too long, and the tortuosity of the transmission inside the negative electrode sheet is too large, which will lead to excessive concentration polarization inside the secondary battery, thereby increasing the internal resistance of the secondary battery and reducing the cycle kinetics performance of the secondary battery.

[0031] For example, based on the mass of the electrolyte, the mass percentage of the chain carboxylate is 6%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 56%, or any value between any two of the above numerical ranges. Chain carboxylate has high conductivity, low viscosity, and facilitates lithium ion transport, which gives the electrolyte high kinetic properties. If the mass percentage of the chain carboxylate is less than 6%, the content of the chain carboxylate in the electrolyte is too low to fully exert its own properties. If the mass percentage of the chain carboxylate is greater than 56%, the content of the chain carboxylate in the electrolyte is too high, and the content of lithium salt and additives in the electrolyte is reduced. Insufficient lithium salt content will affect the charge and discharge performance of the secondary battery. Insufficient additive content will make it difficult for the additive to fully exert its own function, which will affect the corresponding performance of the secondary battery and the additive.

[0032] For example, based on the mass of the electrolyte, the mass percentage of the nitrile additive is 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between any two of the above numerical ranges. The nitrile additive can complex with the transition metal ions in the positive electrode active material to form a protective positive electrode electrolyte interface film (CEI) on the surface of the positive electrode plate, thereby improving the structural stability of the positive electrode plate and reducing the side reaction between the positive electrode active material and the electrolyte to improve the high temperature stability of the secondary battery. The mass percentage of the nitrile additive in the electrolyte is less than 0.01%. The mass percentage of the nitrile additive is too little to play its role and the improvement of the high temperature stability of the secondary battery is not obvious; the mass percentage of the nitrile additive in the electrolyte is greater than 10%. The mass percentage of the nitrile additive is too much, which will reduce the mass percentage of other components in the electrolyte, such as organic solvents, lithium salts, and other additives, affecting the performance of the secondary battery.

[0033] In general, the present application improves the surface activity of the positive and negative active materials by regulating the Dv99 of the positive and negative active materials within the above range, shortens the transmission path of lithium ions in the positive / negative active materials during transmission, and has a smaller transmission tortuosity within the positive / negative electrode sheets, so as to reduce the concentration polarization of the secondary battery, thereby making the secondary battery have good cycle dynamics. The present application regulates the coating weight of the negative active material layer and the coating weight relationship between the positive active material layer and the negative active material layer within the above range. The positive active material layer and the negative active material layer adopt a lower coating weight, which can reduce the thickness of the positive active material layer and the negative active material layer and increase the porosity of the positive active material layer and the negative active material layer, thereby reducing the ohmic polarization and concentration polarization of the positive and negative electrode sheets, shortening the transmission distance of lithium ions and electrons in the positive and negative electrode sheets, and thereby improving the charging rate of the secondary battery. The present application controls the mass percentage of chain carboxylic acid esters and nitrile additives in the electrolyte within the above-mentioned range, so that the electrolyte has a lower viscosity, so that lithium ions have a faster transmission speed in the electrolyte, thereby reducing the electrochemical polarization and concentration polarization of the secondary battery, reducing the impedance of the secondary battery, and reducing the charging temperature rise and charging time during super-fast charging of the secondary battery, thereby making the secondary battery have good cycle kinetics. In addition, the nitrile additive has an appropriate content, which protects the positive and negative electrode sheets while maintaining the high kinetics of the secondary battery, reduces the side reactions between the electrolyte and the positive and negative electrode sheets, and improves the high-temperature stability of the secondary battery. The present application combines the coating weight of the negative electrode active material layer, the coating weight relationship between the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the components and content of the electrolyte, so that the coating weight of the negative electrode active material layer, the coating weight relationship between the positive electrode active material layer and the negative electrode active material layer, the Dv99 of the positive electrode active material and the negative electrode active material, and the electrolyte have good synergistic effects, which can take into account the high temperature stability of the secondary battery on the basis of improving the cycle kinetics performance of the secondary battery.

[0034] In this application, Dv99 means the particle size at which 99% of the volume accumulation is achieved, starting from the small particle size side, in the volume-based particle size distribution. The above-mentioned "particles" in this application can be particles of positive electrode active materials or particles of negative electrode active materials. This application does not particularly limit the method for regulating the Dv99 of positive electrode active materials and negative electrode active materials, as long as the purpose of this application can be achieved. For example, this can be achieved by directly purchasing positive electrode active materials and negative electrode active materials whose Dv99 is within the scope of this application, or by crushing, grinding, ball milling, etc.

[0035] In one embodiment of the present application, 6.49 mg / cm 2 ≤Wz ≤11.69 mg / cm 2 For example, W z 6.49 mg / cm 2 , 7mg / cm 2 , 7.5mg / cm 2 , 8mg / cm 2 、8.5mg / cm 2 , 9mg / cm 2 , 9.5mg / cm 2 、10mg / cm 2 、10.5mg / cm 2 , 11mg / cm 2 、11.69mg / cm 2 Or any value between any two of the above numerical ranges. By regulating the coating weight of the positive electrode active material layer within the range of this application, the present application can shorten the transmission distance of lithium ions and electrons on the positive electrode sheet, which is beneficial for reducing the ohmic polarization and concentration polarization of the secondary battery, thereby reducing the impedance of the secondary battery, and enabling the secondary battery to have good cycle kinetics while taking into account high temperature stability.

[0036] In one embodiment of the present application, 3.90 mg / cm 2 ≤W f ≤5.19mg / cm 2 For example, W f 3.90 mg / cm 2 , 4.00mg / cm 2 , 4.25mg / cm 2 , 4.50mg / cm 2 , 4.75mg / cm 2 , 5.00mg / cm 2 , 5.19mg / cm 2 Or any value between any two numerical ranges mentioned above. f By regulating within the above range, the coating weight range of the negative electrode active material layer is more optimal, which is beneficial to further improve the cycle dynamics performance of the secondary battery while taking into account the high temperature stability.

[0037] In one embodiment of the present application, 7.80 mg / cm 2 ≤W z ≤10.38mg / cm 2 For example, W z 7.80 mg / cm 2 、8.20mg / cm 2 、8.50mg / cm 2 、8.80mg / cm 2, 9.00mg / cm 2 , 9.25mg / cm 2 , 9.50mg / cm 2 , 9.70mg / cm 2 、10.00mg / cm 2 、10.38mg / cm 2 Or any value between any two numerical ranges mentioned above. z By regulating within the above range, the coating weight range of the positive electrode active material layer is more optimal, which is beneficial to further improve the cycle dynamics performance of the secondary battery while taking into account the high temperature stability.

[0038] In one embodiment of the present application, 3.90 mg / cm 2 ≤W f ≤5.19mg / cm 2 , 7.80mg / cm 2 ≤W z ≤10.38mg / cm 2 For example, W f 3.90 mg / cm 2 , 4.00mg / cm 2 , 4.25mg / cm 2 , 4.50mg / cm 2 , 4.75mg / cm 2 , 5.00mg / cm 2 , 5.19mg / cm 2 Or any value between any two numerical ranges mentioned above. For example, W z 7.80 mg / cm 2 、8.20mg / cm 2 、8.50mg / cm 2 、8.80mg / cm 2 , 9.00mg / cm 2 , 9.25mg / cm 2 , 9.50mg / cm 2 , 9.70mg / cm 2 、10.00mg / cm 2 、10.38mg / cm 2 Or any value between any two numerical ranges mentioned above. z and W f By regulating within the above range, the coating weight ranges of the positive electrode active material layer and the negative electrode active material layer are both better, which is beneficial for further improving the cycle dynamics performance of the secondary battery while taking into account the high temperature stability.

[0039] In one embodiment of the present application, the Dv99 of the positive electrode active material is 28 μm to 31 μm. For example, the Dv99 of the positive electrode active material is 28 μm, 29 μm, 30 μm, 31 μm, or any value between any two of the above ranges. By regulating the Dv99 of the positive electrode active material within the above range, the Dv99 range of the positive electrode active material is more optimal, which is conducive to further improving the cycle dynamics performance and high-temperature stability of the secondary battery.

[0040] In one embodiment of the present application, the Dv99 of the negative electrode active material is 24 μm to 26 μm. For example, the Dv99 of the negative electrode active material is 24 μm, 25 μm, 26 μm, or any value between any two of the above ranges. By regulating the Dv99 of the negative electrode active material within the above range, the Dv99 range of the negative electrode active material is more optimal, which is conducive to further improving the cycle dynamics performance and high-temperature stability of the secondary battery.

[0041] In one embodiment of the present application, the Dv99 of the positive electrode active material is 28μm to 31μm, and the Dv99 of the negative electrode active material is 24μm to 26μm. For example, the Dv99 of the positive electrode active material is 28μm, 29μm, 30μm, 31μm or any value between any two of the above numerical ranges. The Dv99 of the negative electrode active material is 24μm, 25μm, 26μm or any value between any two of the above numerical ranges. By regulating the Dv99 of the positive electrode active material and the negative electrode active material within the above range, the Dv99 range of the positive electrode active material and the negative electrode active material is better, which is conducive to further improving the cycle dynamics performance and high temperature stability of the secondary battery.

[0042] In one embodiment of the present application, the Dv50 of the positive electrode active material is 10 μm to 15 μm, and the Dv50 of the negative electrode active material is 7 μm to 12 μm. For example, the Dv50 of the positive electrode active material is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value between any two of the above numerical ranges. The Dv50 of the negative electrode active material is 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any value between any two of the above numerical ranges. By regulating the Dv50 of the positive electrode active material and the negative electrode active material within the above range, the risk of agglomeration of the positive electrode active material in the positive electrode slurry is low, and the risk of agglomeration of the negative electrode active material in the negative electrode slurry is low. On the basis of enabling the positive electrode active material and the negative electrode active material to play their own roles, the thickness of the positive electrode active material layer and the negative electrode active material is regulated within a suitable range to reduce the risk of energy density loss due to increased thickness, thereby helping the secondary battery to have a higher energy density on the basis of good cycle dynamics and high temperature stability.

[0043] In this application, Dv50 refers to the particle size at which 50% of the volume is accumulated, starting from the small particle size side, in the volume-based particle size distribution. The above-mentioned "particles" in this application can be positive electrode active materials or negative electrode active materials. This application does not particularly limit the method for regulating the Dv50 of positive electrode active materials and negative electrode active materials, as long as the purpose of this application can be achieved. For example, this can be achieved by directly purchasing positive electrode active materials and negative electrode active materials whose Dv50 is within the range of this application, or by crushing, grinding, ball milling, etc.

[0044] In one embodiment of the present application, the negative electrode active material includes at least one of a carbon-based material, a silicon-based material, or a tin-based material. The carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesocarbon microbeads. The silicon-based material includes at least one of elemental silicon, a silicon-carbon material, or a silicon-oxygen material. The tin-based material includes at least one of elemental tin, a tin alloy, or a tin oxide. The above-mentioned negative electrode active materials have high surface activity and, when applied to secondary batteries, can increase active sites for lithium ion insertion and extraction, reduce the electrochemical polarization of the secondary battery, and thus reduce the impedance of the secondary battery, so that the secondary battery has good cycle kinetics while maintaining high temperature stability.

[0045] In one embodiment of the present application, the carbon-based material is tested by Raman with a peak intensity ratio of d peak to g peak of I d / I g Satisfy: 0.1≤I d / I g ≤1.0. For example, I d / I g is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any value between any two of the above numerical ranges. This indicates that the surface of the carbon-based material contains amorphous carbon. The presence of amorphous carbon on the surface of the carbon-based material can enhance the electrochemical activity of the carbon-based material, making the embedding of lithium ions smoother during the cycle of the secondary battery, thereby reducing the electrochemical polarization of the secondary battery, thereby reducing the internal impedance of the secondary battery and improving its cycle kinetics. The above I d / I g The application of high-value carbon-based materials in secondary batteries is beneficial to further improve the cycle dynamics performance of secondary batteries on the basis of good high-temperature stability.

[0046] In this application, the d peak is the shift range of 1300 cm in the Raman spectrum of carbon-based material particles. -1 to 1400cm -1 The peak of g is the shift range of 1530cm in the Raman spectrum of carbon-based material particles. -1 to 1630cm-1 Peak.

[0047] This application is for d / I g There is no particular limitation on the method for controlling the value of , as long as the purpose of this application can be achieved. For example, commercially available carbon-based materials with different amounts of amorphous carbon coated on their surfaces can be selected, and the I value of the carbon-based materials can be determined by combining the Raman test method in this application. d / I g , select the desired d / I g of carbon-based materials.

[0048] The present application does not particularly limit the preparation method of the carbon-based material, as long as the purpose of the present application can be achieved. For example, the preparation method of the carbon-based material may include but is not limited to: mixing the carbon-based material and amorphous carbon uniformly, heating to 500°C to 1500°C, and then maintaining the temperature for 10 hours to 20 hours to obtain a carbon-based material with amorphous carbon coated on the surface.

[0049] In one embodiment of the present application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. The chemical formula of the above-mentioned "lithium-rich manganese-based materials" is LiMnO·LiMO, where M may include Ni, Co, or Mn. The above-mentioned types of positive electrode active materials have high surface activity and are applied to secondary batteries to increase the active sites for lithium ion insertion and extraction, reduce the electrochemical polarization of the secondary battery, and thus reduce the impedance of the secondary battery, so that the secondary battery has good cycle dynamics performance on the basis of high temperature stability.

[0050] In one embodiment of the present application, the positive electrode active material further includes a non-metallic element, and the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur. The present application has no particular restriction on the content of the non-metallic element in the positive electrode active material, as long as the purpose of the present application can be achieved. In one embodiment, based on the mass of the positive electrode active material, the mass percentage of the non-metallic element is 0.1% to 10%. For example, the mass percentage of the non-metallic element is 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between any two of the above numerical ranges. Including the above-mentioned types of non-metallic elements in the positive electrode active material can further improve the stability of the positive electrode active material.

[0051] In one embodiment of the present application, the chain carboxylate includes at least one of methyl formate, methyl acetate, ethyl formate, ethyl acetate, propyl acetate, ethyl propionate, methyl propionate, n-propyl propionate, isopropyl propionate, methyl propionate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isopentyl propionate, ethyl butyrate, n-propyl butyrate, propyl isobutyrate, n-pentyl butyrate, n-pentyl isobutyrate, n-butyl butyrate, isobutyl isobutyrate, or n-pentyl valerate. The above-mentioned chain carboxylate has high conductivity and low viscosity, and is convenient for lithium ion transport. The use of the above-mentioned chain carboxylate can enable the secondary battery to have good cycle dynamics and high-temperature stability.

[0052] In one embodiment of the present application, the weight percentage of the chain carboxylate is 18% to 40% based on the weight of the electrolyte. For example, the weight percentage of the chain carboxylate is 18%, 20%, 25%, 30%, 35%, 40%, or any value between any two of the above ranges. By regulating the weight percentage of the chain carboxylate within the above range, lithium ions can be transported faster in the electrolyte, thereby further improving the cycling kinetics of the secondary battery while maintaining good high-temperature stability.

[0053] In one embodiment of the present application, the nitrile additive includes at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, sebacononitrile, 3,3'-oxydipropionitrile, hexane-2-enedinitrile, fumaronitrile, 2-pentene dinitrile, methylglutaronitrile, 4-cyanopimetonitrile, (Z)-but-2-enedinitrile, 2,2,3,3-tetrafluorosuccinonitrile, ethylene glycol bis(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,3,6-hexatriconitrile, 1,2,6-hexatriconitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,1,3,3-propanetetracarbonitrile, 2,2'-(1,4-phenylene)dimalononitrile, 1,1,5,5-pentanetetracarbonitrile, 1,1,4,4-butanetetracarbonitrile or 1,1,6,6-hexatriconitrile. The selection of the above-mentioned nitrile additives is beneficial for further improving the high-temperature stability of the secondary battery on the basis of having good cycle dynamics performance.

[0054] In one embodiment of the present application, the weight percentage of the nitrile additive is 5% to 8% based on the weight of the electrolyte. For example, the weight percentage of the nitrile additive is 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any value between any two of the above ranges, based on the weight of the electrolyte. Controlling the weight percentage of the nitrile additive within the above ranges is beneficial for further improving the high-temperature stability of the secondary battery while maintaining good cycling kinetics.

[0055] In one embodiment of the present application, the organic solvent further includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone or tetrahydrofuran; based on the mass of the electrolyte, the mass percentage of the organic solvent is 60% to 80%. For example, based on the mass of the electrolyte, the mass percentage of the organic solvent is 60%, 64%, 67%, 70%, 73%, 78%, 80% or any value between any two of the above numerical ranges. The above-mentioned types of organic solvents have the characteristics of good stability at high temperatures and fast lithium ion transmission speed at room temperature. The addition of the above-mentioned types of organic solvents to the electrolyte can further improve the high-temperature stability and cycle dynamics of the secondary battery, reduce the charging speed and reduce the temperature rise. Regulating the mass percentage of the organic solvent within the above range is beneficial to improving the solubility of additives and lithium salts, so that the electrolyte has a lower viscosity and higher conductivity, which is beneficial to the migration of lithium ions in the electrolyte, so that the secondary battery has good cycle dynamics and high-temperature stability.

[0056] In one embodiment of the present application, the mass percentage of the lithium salt is 10% to 20% based on the mass of the electrolyte. For example, the mass percentage of the lithium salt is 10%, 12%, 14%, 16%, 18%, 20% or any value between any two of the above numerical ranges. By regulating the mass percentage of the lithium salt within the above range, the lithium salt has a higher solubility in the electrolyte, so that the electrolyte has a higher electrical conductivity, thereby improving the cycle dynamics performance and high temperature stability of the secondary battery. The present application does not particularly limit the type of lithium salt, as long as it can achieve the purpose of the present application. For example, the lithium salt includes but is not limited to at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), lithium bis(oxalatoborate) or lithium difluorooxalatoborate.

[0057] In one embodiment of the present application, the electrolyte includes a lithium salt, an organic solvent and an additive, and the additive includes a nitrile additive and other additives, and the mass percentage of the additive is 10% to 20% based on the mass of the electrolyte. The present application has no particular restrictions on the types of other additives, as long as the purpose of the present application can be achieved. For example, other additives include solid electrolyte interface (SEI) film-forming additives, flame retardant additives, anti-overcharge additives, and conductive additives. Exemplarily, other additives include but are not limited to at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC) or diethylene sulfate (DTD).

[0058] The positive electrode sheet of the present application includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In some embodiments, the positive electrode active material layer is disposed on one surface of the positive electrode current collector. In other embodiments, the positive electrode active material layer is disposed on both surfaces of the positive electrode current collector. The above-mentioned "surface" can be part of the surface or the entire surface of the positive electrode current collector. The present application does not particularly limit the type of positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector can include but is not limited to aluminum foil or aluminum alloy foil. The positive electrode active material layer of the present application includes the positive electrode active material described in the above embodiments. In the present application, there is no particular limitation on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, and further, the thickness of the positive electrode current collector can be 6μm to 18μm. The thickness of the positive electrode active material layer is 30μm to 120μm.

[0059] Optionally, the positive electrode active material layer may further include a positive electrode conductor and a positive electrode binder. The present application has no particular restrictions on the types of positive electrode conductors and positive electrode binders in the positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode active material layer is (95-98): (0.5-3.5): (1.5-3.4).

[0060] The negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In some embodiments, the negative electrode active material layer is disposed on one surface of the negative electrode current collector. In other embodiments, the negative electrode active material layer is disposed on both surfaces of the negative electrode current collector. The above-mentioned "surface" can be part of the surface or the entire surface of the negative electrode current collector. The present application does not particularly limit the type of negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the negative electrode current collector includes but is not limited to copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam or copper foam. The negative electrode active material layer of the present application includes the negative electrode active material described in the above embodiments. In the present application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 6μm to 10μm, and the thickness of the negative electrode active material layer is 30μm to 130μm.

[0061] Optionally, the negative electrode active material layer may further include at least one of a negative electrode conductor, a stabilizer or a negative electrode binder. The present application does not particularly limit the types of negative electrode conductors, stabilizers and negative electrode binders in the negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductor, the stabilizer and the negative electrode binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the mass ratio of the negative electrode active material, the negative electrode conductor, the stabilizer and the negative electrode binder in the negative electrode active material layer is (96-98):(0.5-2):(0-1.5):(1.0-1.9).

[0062] The diaphragm in the secondary battery of the present application is not particularly limited, as long as the purpose of the present application can be achieved. For example, the diaphragm includes at least one of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI) or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene and ultra-high molecular weight polyethylene. The diaphragm of the present application may have a porous structure, and the present application does not particularly limit the size of the pore size of the porous structure of the diaphragm, as long as the purpose of the present application can be achieved. For example, the size of the pore size can be 0.01μm to 1μm. The present application does not particularly limit the thickness of the diaphragm, as long as the purpose of the present application can be achieved, for example, the thickness of the diaphragm can be 5μm to 500μm.

[0063] In one embodiment of the present application, the secondary battery further comprises a housing, in which the electrode assembly and electrolyte are housed. The present application does not particularly limit the housing and may be any known housing in the art, as long as it can achieve the objectives of the present application. For example, the housing includes, but is not limited to, an aluminum-plastic film or a steel shell.

[0064] The present application does not particularly limit the type of secondary battery, which may include any device that undergoes an electrochemical reaction. For example, secondary batteries may include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries (lithium ion batteries), sodium ion secondary batteries (sodium ion batteries), lithium polymer secondary batteries, and lithium ion polymer secondary batteries.

[0065] The secondary battery of the present application can be used under super-fast charging conditions, specifically, can be used under conditions of a charging rate of 5C to 15C. For example, the charging rate of the secondary battery can be 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C, 14C, 15C or any rate between any two of the above rate ranges.

[0066] The present application does not impose any particular restrictions on the preparation method of the secondary battery, and any preparation method known in the art may be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the secondary battery includes but is not limited to the following steps: stacking the separator, the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and winding, folding, and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery. Alternatively, stacking the separator, the positive electrode sheet, the separator, and the negative electrode sheet in sequence, fixing the four corners of the entire stacked structure to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery.

[0067] The second aspect of the present application provides an electric device, which includes the secondary battery described in any of the above embodiments. Therefore, the electric device has good performance.

[0068] The electrical device of the present application is not particularly limited and may be any electrical device known in the art. For example, the electrical device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, 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 power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0069] Example

[0070] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0071] Test methods and equipment:

[0072] Dv50 and Dv99 tests:

[0073] The Dv50 and Dv99 of the positive and negative active materials were measured using a laser particle size analyzer.

[0074] Coat Weight Test:

[0075] (1) Coating weight W of the positive electrode active material layer z test:

[0076] The lithium-ion battery was discharged at 0.5C to 3.0V and then disassembled to obtain the positive electrode sheet. The positive electrode sheet was immersed in dimethyl carbonate (DMC) solution for 4 hours and then dried. The area of ​​the sheet was cut into pieces with an area of ​​Amm. 2 The positive electrode sheet sample is placed on a balance and weighed, which is recorded as p1. The positive electrode active material layer on the positive electrode sheet is then washed clean, and the positive electrode current collector is placed on a balance and weighed, which is recorded as p2.

[0077] If the positive electrode sheet is coated with a positive electrode active material layer on one side, W z =(p1-p2) / A.

[0078] If it is a positive electrode sheet coated with a positive electrode active material layer on both sides, W z =(p1-p2) / 2A.

[0079] (2) Coating weight W of negative electrode active material layer f test:

[0080] The lithium-ion battery was discharged at 0.5C to 3.0V and then disassembled to obtain the negative electrode sheet. The negative electrode sheet was soaked in DMC solution for 4 hours and then dried. The area of ​​the sheet was cut to B mm. 2 The negative electrode sheet sample is placed on a balance and weighed, which is recorded as q1. Then the negative electrode active material layer on the negative electrode sheet is washed clean, and the negative electrode current collector is placed on a balance and weighed, which is recorded as q2.

[0081] If the negative electrode sheet is coated with a negative electrode active material layer on one side, W f =(q1-q2) / B.

[0082] If it is a negative electrode sheet with negative electrode active material layer coated on both sides, W f =(q1-q2) / 2B.

[0083] Raman test:

[0084] The lithium-ion battery was discharged at 0.5C to 3.0V and then disassembled to obtain the negative electrode sheet. The negative electrode sheet was immersed in DMC solution for 4 hours and then dried. An area of ​​100 μm × 100 μm was selected on the negative electrode active material layer. A laser microconfocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instrument Division) was used to scan the negative electrode active material particles within the area to obtain the d peak and g peak of all the negative electrode active material particles within the area. The data was processed using LabSpec software to obtain the peak intensities of the d peak and g peak of each negative electrode active material particle, which were I d and I g The laser wavelength of the Raman spectrometer is in the range of 532nm to 785nm. d / I g The value of I of all negative electrode active material particles measured within this range d and I g The average of the ratios.

[0085] Cyclic dynamics performance test:

[0086] The lithium-ion batteries of the embodiments and comparative examples were subjected to a cycle dynamics performance test at a charge rate of 10C, and the specific steps are as follows:

[0087] (1) Adjust the test temperature to a constant temperature of 25°C, place the temperature sensing line of the multi-channel thermometer at the center of the lithium-ion battery surface, and perform the following steps: 1) 10C constant current charge to 4.2V; 2) 7C constant current charge to 4.3V; 3) 5C constant current charge to 4.45V; 4) 4.45V constant voltage charge to 0.05C; 5) stand for 30 minutes; 6) 1C constant current discharge to 3.0V; 7) stand for 30 minutes; end;

[0088] Charging speed: the time from step 1) to step 4) in step (1);

[0089] Charging temperature rise: The difference between the maximum temperature of the lithium-ion battery surface temperature sensor line during the process of step (1) from step 1) to step 4) and the room temperature.

[0090] (2) Adjust the test temperature to 25°C and start the test: 1) 10C constant current charge to 4.2V; 2) 7C constant current charge to 4.3V; 3) 5C constant current charge to 4.45V; 4) 4.45V constant voltage charge to 0.05C; 5) stand for 5 minutes; 6) 1C constant current discharge to 3.0V; 7) stand for 5 minutes; 8) cycle steps 1) to 7) for 1000 cycles (cls); end;

[0091] Capacity retention (%) = discharge capacity after 1000 cls / first cycle discharge capacity × 100%.

[0092] The cycle kinetic performance is characterized by charging speed, charging temperature rise and capacity retention rate. Among them, the shorter the charging time and the smaller the charging temperature rise, the better the initial kinetic performance of the lithium-ion battery, and the higher the capacity retention rate, the better the cycle performance of the lithium-ion battery.

[0093] High temperature stability test:

[0094] Test the thickness of the lithium-ion battery after it is manufactured, referred to as the initial thickness of the lithium-ion battery;

[0095] The lithium-ion battery is fully charged according to the following steps: charge at a constant current of 0.7C to 4.45V, and charge at a constant voltage of 4.45V to 0.02C;

[0096] After the lithium-ion battery is placed in a high and low temperature box at 90°C for 8 hours, the thickness of the lithium-ion battery after storage is tested, and the test is completed.

[0097] The expansion rate of the lithium-ion battery = (thickness of the lithium-ion battery after high-temperature storage - initial thickness of the lithium-ion battery) / initial thickness of the lithium-ion battery × 100%. The expansion rate is used to characterize high-temperature stability. The smaller the expansion rate, the better the high-temperature stability.

[0098] Example 1-1

[0099] <Preparation of positive electrode sheet>

[0100] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is carbon nanotubes, and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw = 7×10 6 ) are mixed in a mass ratio of 95:3:2, N-methylpyrrolidone (NMP) is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 75wt% and the system is uniform. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm and dried at 95°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. Then, it is cold pressed, cut into pieces, and slit. After slit, it is dried at 85°C under vacuum for 4h to obtain a positive electrode sheet with a specification of 55mm×1400mm for use. Among them, the single layer thickness of the positive electrode active material layer is 37.3μm, and the thickness of the positive electrode sheet is 84.6μm. The tab area of ​​the positive electrode current collector is formed into 18 positive tabs by die-cutting, and the compaction density of the positive electrode sheet is 37g / cm 3 The Dv99 of lithium cobalt oxide is 30 μm and Dv50 is 13 μm. The coating weight of the positive electrode active material layer is W. z 10.38 mg / cm 2 .

[0101] <Preparation of negative electrode sheet>

[0102] The negative electrode active material artificial graphite, negative electrode conductive agent Super P, stabilizer sodium carboxymethyl cellulose (CMC-Na, Mw = 7 × 10 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10 6) are mixed in a mass ratio of 97:1:1:1, and then deionized water is added as a solvent. The mixture is stirred in a vacuum mixer until the solid content is 51wt% and the system is uniform. The negative electrode slurry is evenly coated on one surface of a 7μm thick negative electrode current collector copper foil and dried at 85°C to obtain a negative electrode sheet with a single-sided negative electrode active material layer. Thereafter, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode active material layer. The negative electrode sheet is then cold pressed, cut, and slit. After slit, it is dried at 110°C under vacuum for 4 hours to obtain a negative electrode sheet with a specification of 58mm×1500mm for use. Among them, the single layer thickness of the negative electrode active material layer is 58.5μm, and the thickness of the negative electrode sheet is 124μm. The tab area of ​​the negative electrode current collector is formed into 18 negative electrode tabs by die-cutting. The compaction density of the negative electrode sheet is 1.7g / cm 3 The Dv99 of artificial graphite is 25 μm and Dv50 is 9 μm. The coating weight of the negative electrode active material layer is W. f 5.19 mg / cm 2 .

[0103] <Preparation of Electrolyte>

[0104] Under an environment with a water content of less than 10 ppm, an organic solvent, a lithium salt, and an additive are prepared in a mass ratio of 80:10:10 to obtain an electrolyte. The lithium salt is lithium hexafluorophosphate, the additive is a nitrile additive succinonitrile, and other additives are fluoroethylene carbonate (FEC). The organic solvent is n-propyl orthophosphate, ethylene carbonate, and diethyl carbonate, and the mass ratio of n-propyl orthophosphate, ethylene carbonate, and diethyl carbonate is 40:30:30. Based on the mass of the electrolyte, the mass percentage of the chain carboxylic acid ester is W1 = 40% × 80% = 32%, the mass percentage of ethylene carbonate is W2 = 30% × 80% = 24%, the mass percentage of diethyl carbonate is W3 = 30% × 80% = 24%, the mass percentage of the nitrile additive is 2%, and the balance is the lithium salt and other additives (FEC).

[0105] <Preparation of Separator>

[0106] A porous polyethylene membrane with a thickness of 15 μm was selected as the separator.

[0107] <Preparation of lithium-ion batteries>

[0108] The separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrode assembly is then wound to form a complete package. The assembly is then placed in an aluminum-plastic film casing, dried, and then filled with electrolyte. The lithium-ion battery is then produced through vacuum packaging, resting, formation, capacity measurement, degassing, and trimming.

[0109] Example 1-2 to Example 1-33

[0110] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0111] When the mass percentage of the linear carboxylate changes, the mass percentages of ethylene carbonate and diethyl carbonate also change. When the mass percentage of the nitrile additive changes, the mass percentages of the other additives also change. The mass ratio of the lithium salt, organic solvent, and additives remains unchanged. The sum of the mass percentages of the linear carboxylate, ethylene carbonate, and diethyl carbonate is W1 + W2 + W3 = 80%, with W2 = W3. The sum of the mass percentages of the lithium salt, organic solvent, and additives is 100%.

[0112] Example 2-1 to Example 2-5

[0113] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0114] Examples 2-6

[0115] Except that the mass ratio of lithium salt, organic solvent and additive was adjusted to 20:60:20 in <Preparation of Electrolyte>, the rest was the same as Example 1-1.

[0116] Examples 2-7

[0117] Except that the mass ratio of lithium salt, organic solvent and additive was adjusted to 15:70:15 in <Preparation of Electrolyte>, the rest was the same as Example 1-1.

[0118] Examples 2-8

[0119] Except that the mass ratio of lithium salt, organic solvent and additive was adjusted to 22.5:55:22.5 in <Preparation of Electrolyte>, the rest was the same as Example 1-1.

[0120] Examples 2-9

[0121] Except that the mass ratio of lithium salt, organic solvent and additive was adjusted to 7.5:85:7.5 in <Preparation of Electrolyte>, the rest was the same as Example 1-1.

[0122] Example 3-1

[0123] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.

[0124] Example 3-2 to Example 3-4

[0125] The process was the same as Example 1-1, except that artificial graphite coated with amorphous carbon was used as the negative electrode active material in the preparation of the negative electrode sheet. The mass ratio of artificial graphite to amorphous carbon was adjusted according to Table 3.

[0126] Example 3-5 and Example 3-6

[0127] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.

[0128] Comparative Examples 1 to 18

[0129] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0130] When the mass percentage of the linear carboxylate changes, the mass percentages of ethylene carbonate and diethyl carbonate also change. When the mass percentage of the nitrile additive changes, the mass percentages of the other additives also change. The mass ratio of the lithium salt, organic solvent, and additives remains unchanged. The sum of the mass percentages of the linear carboxylate, ethylene carbonate, and diethyl carbonate is W1 + W2 + W3 = 80%, with W2 = W3. The sum of the mass percentages of the lithium salt, organic solvent, and additives is 100%.

[0131] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1 to Table 3. Table 1 Note: “\” in Table 1 indicates no corresponding parameter.

[0132] It can be seen from Examples 1-1 to 1-29 and Comparative Examples 1 to 18 that the secondary battery of the present invention can be obtained by setting the coating weight W of the positive electrode active material layer. z The coating weight W of the negative electrode active material layer f The ratio W z / W f and W fThe value of is within the scope of this application, and the Dv99 of the positive electrode active material and the Dv99 of the negative electrode active material are within the scope of this application, and the content of the chain carboxylic acid ester and the nitrile additive in the electrolyte is within the scope of this application, so that the secondary battery has a shorter charging time (that is, a higher charging speed), a lower charging temperature rise, and a higher capacity retention rate at a charging rate of 10C, and the thickness of the secondary battery has a lower expansion rate after being stored at 90°C for 8h, that is, the secondary battery of the embodiment of the present application can simultaneously have a shorter charging time, a lower charging temperature rise, a higher capacity retention rate and a lower expansion rate. This shows that the secondary battery of the embodiment of the present application can take into account high temperature stability on the basis of good cycle dynamics under super-fast charging conditions, that is, the secondary battery of the embodiment of the present application has better comprehensive performance under super-fast charging conditions. The secondary batteries of Comparative Examples 1 and 2 have a coating weight W of the negative electrode active material layer. f Not within the scope of this application; the secondary batteries of Comparative Examples 3 and 4, the coating weight W of the positive electrode active material layer z The coating weight W of the negative electrode active material layer f The ratio W z / W f is not within the scope of the present application; the Dv99 of the negative electrode active material of the secondary batteries of Comparative Examples 5 and 6 is not within the scope of the present application; the Dv99 of the positive electrode active material of the secondary batteries of Comparative Examples 7 and 8 is not within the scope of the present application; the content of the chain carboxylic ester in the electrolyte of the secondary batteries of Comparative Examples 9 and 10 is not within the scope of the present application; the content of the nitrile additive in the electrolyte of the secondary batteries of Comparative Examples 11 and 12 is not within the scope of the present application; the Dv99 of the negative electrode active material, the Dv99 of the positive electrode active material, and the coating weight W of the negative electrode active material layer of the secondary batteries of Comparative Examples 13 and 14 are not within the scope of the present application; f Not within the scope of this application; the secondary batteries of Comparative Examples 15 and 16, the Dv99 of the positive electrode active material, the Dv99 of the negative electrode active material, the content of the chain carboxylate in the electrolyte, the coating weight W of the positive electrode active material layer z The coating weight W of the negative electrode active material layer f The ratio W z / W f and W f The values ​​of are not within the scope of this application; the secondary batteries of Comparative Examples 17 and 18, the Dv99 of the positive electrode active material, the Dv99 of the negative electrode active material, the content of the chain carboxylate in the electrolyte, the coating weight W of the positive electrode active material layer z The coating weight W of the negative electrode active material layer f The ratio W z / W f 、Wf The value of and the content of nitrile additives in the electrolyte are not within the scope of this application; the coating weight W of the positive electrode active material layer of Comparative Example 1 z The coating weight W of the negative electrode active material layer f The resulting secondary batteries have a fast charging speed and low impedance. However, due to the low coating weights of the positive and negative active material layers, the cost of precisely controlling the coating weights in actual industrial production is prohibitive. Consequently, the qualified rate of lithium-ion batteries obtained in large-scale production is too low, and the energy density of the resulting secondary batteries is too low to meet actual production needs and is unsuitable for industrial production applications. The secondary batteries of Comparative Examples 2 to 18 cannot simultaneously meet the requirements of short charging time, low charging temperature rise, long cycle life, and low expansion rate.

[0133] The coating weight W of the negative electrode active material layer f It usually affects the cycle dynamics performance and high temperature stability of the secondary battery. From Examples 1-1 to 1-7, Comparative Examples 1 and 2, it can be seen that the coating weight W of the negative electrode active material layer is selected. f The secondary battery within the scope of this application has a shorter charging time (i.e., a higher charging speed), a lower charging temperature rise, and a higher capacity retention rate at a charging rate of 10C, and a lower thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary battery can have good cycle dynamics performance under super-fast charging conditions while taking into account high temperature stability. As mentioned above, the coating weight W of the positive electrode active material layer of Comparative Example 1 is z The coating weight W of the negative electrode active material layer f The obtained lithium-ion battery has a faster charging speed and lower impedance. However, since the coating weight of the positive electrode active material layer and the negative electrode active material layer is too low, the cost of accurately controlling the coating weight in actual industrial production is too high. The qualified rate of the lithium-ion battery obtained in large-scale production is too low and the energy density of the obtained lithium-ion battery is too low, which cannot meet the needs of actual production and is not suitable for industrial production applications.

[0134] The coating weight W of the positive electrode active material layer z The coating weight W of the negative electrode active material layer f The ratio W z / W f It usually affects the cycle dynamics and high temperature stability of the secondary battery. From Example 1-1, Example 1-8 and Example 1-9, Comparative Example 3 and Comparative Example 4, it can be seen that the coating weight W of the positive electrode active material layer is selected. z The coating weight W of the negative electrode active material layer f The ratio W z / W fThe secondary batteries within the scope of this application can simultaneously achieve a short charging time, a low charging temperature rise, and a high capacity retention rate at a charge rate of 10C, and have a low thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary batteries can achieve good cycle dynamics under super-fast charging conditions while also maintaining high-temperature stability.

[0135] The Dv99 negative electrode active material typically affects the cycle dynamics and high-temperature stability of secondary batteries. As can be seen from Examples 1-1, 1-10, 1-13, Comparative Examples 5, and 6, secondary batteries using Dv99 negative electrode active materials within the scope of this application achieve a short charging time, a low charging temperature rise, and a high capacity retention rate at a 10C charge rate. They also exhibit a low thickness expansion rate after storage at 90°C for 8 hours. This allows secondary batteries to maintain both good cycle dynamics and high-temperature stability under super-fast charging conditions.

[0136] The Dv99 content of the positive electrode active material generally affects the cycle dynamics and high-temperature stability of the secondary battery. As can be seen from Examples 1-1, 1-14, 1-17, Comparative Examples 7, and 8, secondary batteries using Dv99 as the positive electrode active material within the scope of this application can simultaneously achieve a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate at a 10C charge rate, and a lower thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary battery can achieve both good cycle dynamics and high-temperature stability under super-fast charging conditions.

[0137] The content of chain carboxylic acid ester in the electrolyte usually affects the cycle dynamics and high-temperature stability of the secondary battery. From Examples 1-1, 1-18 to 1-22, Comparative Examples 9 and 10, it can be seen that the secondary battery with the content of chain carboxylic acid ester in the electrolyte within the range of this application has a short charging time, a low charging temperature rise and a high capacity retention rate at a charging rate of 10C, and a low thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary battery can have good cycle dynamics performance under super-fast charging conditions while taking into account high-temperature stability.

[0138] The content of nitrile additives in the electrolyte usually affects the cycle dynamics and high-temperature stability of the secondary battery. From Examples 1-1, 1-23 to 1-29, Comparative Examples 11 and 12, it can be seen that the secondary battery with the content of nitrile additives in the electrolyte within the range of this application can simultaneously take into account a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate at a charge rate of 10C, and has a lower thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary battery can have good cycle dynamics under super-fast charging conditions while taking into account high-temperature stability.

[0139] The Dv50 of the negative electrode active material usually affects the cycle dynamics and high temperature stability of the secondary battery. It can be seen from Example 1-1, Example 1-10 to Example 1-13, Example 1-30 and Example 1-31 that the secondary battery whose Dv50 of the negative electrode active material is within the scope of this application has a short charging time, a low charging temperature rise and a high capacity retention rate at a charging rate of 10C, and has a low expansion rate of thickness after storage at 90°C for 8h. As a result, the secondary battery can have good cycle dynamics under super fast charging conditions while taking into account high temperature stability. Moreover, it can also be seen from Example 1-11 and Example 1-30 that when the negative electrode active material of the same Dv99 has different Dv50, the cycle dynamics and high temperature stability of the secondary battery will also be affected.

[0140] The Dv50 of the positive electrode active material usually affects the cycle dynamics and high temperature stability of the secondary battery. It can be seen from Example 1-1, Example 1-14 to Example 1-17, Example 1-32 and Example 1-33 that the secondary battery whose Dv50 of the positive electrode active material is within the scope of this application has a shorter charging time, a lower charging temperature rise and a higher capacity retention rate at a charging rate of 10C, and has a lower thickness expansion rate after storage at 90°C for 8h. As a result, the secondary battery can have good cycle dynamics under super fast charging conditions while taking into account high temperature stability. Moreover, it can also be seen from Example 1-14 and Example 1-32 that when the positive electrode active material of the same Dv99 has different Dv50, the cycle dynamics and high temperature stability of the secondary battery will also be affected.

[0141] Table 2

[0142] The type of chain carboxylate generally affects the cycle dynamics and high-temperature stability of secondary batteries. As can be seen from Examples 1-1, 2-1, and 2-3, secondary batteries using chain carboxylate types within the scope of this application achieve a short charging time, low charging temperature rise, and high capacity retention at a 10C charge rate, and exhibit a low thickness expansion rate after storage at 90°C for 8 hours. This allows the secondary battery to achieve both good cycle dynamics and high-temperature stability under super-fast charging conditions.

[0143] The type of nitrile additive generally affects the cyclic kinetics and high-temperature stability of secondary batteries. As can be seen from Examples 1-1, 2-4, and 2-5, secondary batteries using nitrile additives within the scope of this application achieve a short charging time, a low charging temperature rise, and a high capacity retention rate at a 10C charge rate, and exhibit a low thickness expansion rate after storage at 90°C for 8 hours. This allows the secondary battery to achieve both good cyclic kinetics and high-temperature stability under super-fast charging conditions.

[0144] The content of organic solvents in the electrolyte generally affects the cycle dynamics and high-temperature stability of secondary batteries. As can be seen from Examples 1-1, 2-6, and 2-9, secondary batteries with an organic solvent content in the electrolyte within the range of this application achieve a shorter charging time, lower charging temperature rise, and higher capacity retention at a 10C charge rate, and exhibit a lower thickness expansion rate after storage at 90°C for 8 hours. As a result, secondary batteries can achieve both good cycle dynamics and high-temperature stability under super-fast charging conditions.

[0145] Table 3 Note: “\” in Table 3 indicates no corresponding parameter; “Mr” in Table 3 indicates the mass ratio of artificial graphite to amorphous carbon.

[0146] Types of negative electrode active materials, carbon-based materials d / I g The value usually affects the cycle dynamics performance and high temperature stability of the secondary battery. From Example 1-1, Example 3-1 to Example 3-4, it can be seen that the type of negative electrode active material, the I of the carbon-based material d / I gThe secondary battery with a value within the scope of this application has a short charging time, a low charging temperature rise and a high capacity retention rate at a charging rate of 10C, and a low expansion rate of thickness after storage at 90°C for 8 hours. As a result, the secondary battery can have good cycle dynamics performance under super fast charging conditions while taking into account high temperature stability. Among them, Figure 1 shows the Raman spectrum of Example 3-3. It can be seen from Figure 1 that in the Raman spectrum of the high-kinetic negative electrode material, its I d / I g A higher value indicates that it has good surface activity.

[0147] The type of positive electrode active material usually affects the cycle dynamics performance and high temperature stability of the secondary battery. It can be seen from Examples 1-1, 3-5 and 3-6 that the type of positive electrode active material, the carbon-based material d / I g Secondary batteries with values ​​within the range of this application simultaneously achieve a short charging time, a low charging temperature rise, and a high capacity retention rate at a charging rate of 10C, and have a low thickness expansion rate after storage at 90°C for 8 hours. As a result, the secondary batteries can achieve both good cycle dynamics performance and high-temperature stability under super-fast charging conditions.

[0148] It should be noted that, in this document, relational terms such as first and second, etc., are used only 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 terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0149] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0150] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery, wherein, It includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The positive electrode sheet includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material. The negative electrode sheet includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material; The coating weight of the positive electrode active material layer is W z , and the coating weight of the negative electrode active material layer is W f , W z and W f satisfy the following conditions: 1.6W f ≤W z ≤2.2W f 、3.25mg / cm 2 ≤W f ≤5.84mg / cm 2 ; The Dv99 of the positive electrode active material is 27 μm to 33 μm, and the Dv99 of the negative electrode active material is 23 μm to 28 μm; The electrolyte includes an organic solvent, a lithium salt and a nitrile additive. The organic solvent includes a chain carboxylic acid ester. Based on the mass of the electrolyte, the mass percentage content of the chain carboxylic acid ester is 6% to 56%, and the mass percentage content of the nitrile additive is 0.01% to 10%.

2. The secondary battery according to claim 1, wherein, 6.49 mg / cm 2 ≤W z ≤11.69 mg / cm 2 。 3. The secondary battery according to claim 1, wherein, 3.90 mg / cm 2 ≤W f ≤5.19 mg / cm 2 , and / or, 7.80 mg / cm 2 ≤W z ≤10.38 mg / cm 2 .

4. The secondary battery according to claim 1, wherein, The Dv99 of the positive electrode active material is 28 μm to 31 μm, and / or the Dv99 of the negative electrode active material is 24 μm to 26 μm.

5. The secondary battery according to claim 1, wherein, The Dv50 of the positive electrode active material is 10 μm to 15 μm, and the Dv50 of the negative electrode active material is 7 μm to 12 μm.

6. The secondary battery according to claim 1, wherein, The negative electrode active material includes at least one of a carbon-based material, a silicon-based material or a tin-based material. The carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon or mesocarbon microbeads. The silicon-based material includes at least one of elemental silicon, silicon-carbon material or silicon-oxygen material. The tin-based material includes at least one of elemental tin, tin alloy or tin oxide.

7. The secondary battery according to claim 6, wherein, The intensity ratio I of the D peak to the G peak of the carbon-based material through Raman testing d / I g satisfies: 0.1 ≤ I d / I g ≤ 1.

0.

8. The secondary battery according to claim 1, wherein The positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate or lithium titanate.

9. The secondary battery according to claim 8, wherein, The positive electrode active material further includes a non-metallic element, and the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur.

10. The secondary battery according to claim 1, wherein, The chain carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, ethyl acetate, propyl acetate, ethyl propionate, methyl propionate, n-propyl propionate, isopropyl propionate, methyl propionate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isopentyl propionate, ethyl n-butyrate, n-propyl n-butyrate, isopropyl butyrate, n-pentyl n-butyrate, isopentyl n-butyrate, n-butyl n-butyrate, isobutyl isobutyrate or n-pentyl n-pentanoate.

11. The secondary battery according to claim 1, wherein, Based on the mass of the electrolyte, the mass percentage content of the chain carboxylic acid ester is 18% to 40%.

12. The secondary battery according to claim 1, wherein, The nitrile additive includes at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, sebaconitrile, 3,3'-oxydipropionitrile, hex-2-enedinitrile, fumarodinitrile, 2-pentenedinitrile, methylglutaronitrile, 4-cyanoheptanedinitrile, (Z)-but-2-enedinitrile, 2,2,3,3-tetrafluorobutanedinitrile, ethylene glycol bis(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,1,3,3-propanetetracarbonitrile, 2,2'-(1,4-phenylene)dimalononitrile, 1,1,5,5-pentanetetracarbonitrile, 1,1,4,4-butanetetracarbonitrile or 1,1,6,6-hexanetetracarbonitrile.

13. The secondary battery according to claim 1, wherein, Based on the mass of the electrolyte, the mass percentage content of the nitrile additive is 5% to 8%.

14. The secondary battery according to claim 1, wherein, The organic solvent further includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone or tetrahydrofuran; Based on the mass of the electrolyte, the mass percentage content of the organic solvent is 60% to 80%.

15. An electrical device, which includes the secondary battery according to any one of claims 1 to 14.

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