A lithium-ion battery

Abstract

The present invention relates to the technical field of lithium-ion batteries and provides a lithium-ion battery. In the lithium-ion battery of the present invention, in the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface that are oppositely arranged. A plurality of first protrusions are arranged at intervals on the first surface, and a plurality of first depressions are correspondingly arranged on the second surface; the height of the first protrusion is denoted as H μm, the diameter of the first protrusion is denoted as R mm, and H and R satisfy 0.2 ≤ H / R ≤ 80; the electrolyte includes carboxylic esters, and the mass percentage of the carboxylic esters in the total mass of the electrolyte is denoted as A; A satisfies 10 ≤ A ≤ 80; the electrolyte includes nitrile compounds, and the mass percentage of the nitrile compounds in the total mass of the electrolyte is denoted as B; B satisfies 3 ≤ B ≤ 30. When the above conditions are met, the fast charging performance of the battery can be improved and the cycle stability of the battery can be enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a lithium-ion battery. Background Art

[0002] Lithium batteries have become an indispensable part of human daily life, providing durable and powerful power for smartphones, laptops, electric vehicles, etc. Whether at work, study or entertainment, the convenience and reliability of lithium batteries have greatly improved the quality of life. With the progress of technology, fast charging technology has emerged, which greatly shortens the charging time and meets the needs of modern people's fast-paced life.

[0003] However, during fast charging, a problem that needs to be solved urgently is the phenomenon of lithium plating. When lithium ions rapidly deintercalate from the positive electrode and attempt to intercalate into the negative electrode, if the intercalation speed of the negative electrode cannot keep up with the charging speed, or the lithium intercalation on the electrode surface is saturated, lithium ions will deposit on the surface of the negative electrode to form metallic lithium. This will not only reduce the service life of the battery, but also may cause safety problems such as battery overheating, swelling and even fire. Therefore, how to effectively control and avoid the phenomenon of lithium plating while increasing the charging speed has become an important topic in the development of lithium battery technology. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art, and provide a lithium-ion battery. A convex part and a concave part are provided on the positive electrode sheet. By controlling the ratio of the height of the convex part to the diameter of the convex part, an uneven texture with appropriate size can be formed on the surface of the positive electrode sheet, which can increase the liquid storage space of the electrode sheet, optimize the lithium ion transmission path, and improve the fast charging performance of the battery; at the same time, the carboxylic acid ester and nitrile compound introduced into the electrolyte have low viscosity, which can improve the conductivity and accelerate the uniform transmission rate of lithium ions, effectively alleviate the problem of uneven local lithium ion transmission rate that may be caused by the convex part and concave part provided on the electrode sheet, reduce lithium plating, and improve the cycle stability of the battery.

[0005] To achieve the above purpose, the present invention provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte;

[0006] In the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface arranged oppositely. A plurality of first convex parts are arranged at intervals on the first surface, and a plurality of first concave parts are arranged correspondingly on the second surface; the height of the first convex part is denoted as H μm, the diameter of the first convex part is denoted as R mm, and H and R satisfy: 0.2 ≤ H / R ≤ 80;

[0007] The electrolyte includes carboxylic acid ester, and the mass percentage of the carboxylic acid ester in the total mass of the electrolyte is denoted as A %; A satisfies: 10 ≤ A ≤ 80;

[0008] The electrolyte includes a nitrile compound. Based on the total mass of the electrolyte, the mass percentage of the nitrile compound is denoted as B%; B satisfies: 3 ≤ B ≤ 30.

[0009] The present invention adopts the above technical solution and has the following beneficial effects:

[0010] For the lithium-ion battery provided by the present invention, by adjusting the ratio of the height of the convex part to the diameter of the convex part, an uneven texture with appropriate size is formed on the surface of the positive electrode sheet, which can increase the liquid storage space of the electrode sheet, optimize the lithium-ion transmission path, and improve the fast charging performance; meanwhile, the carboxylic acid ester and nitrile compound introduced into the electrolyte reduce the viscosity, improve the conductivity, accelerate the uniform transmission rate of lithium ions, effectively alleviate the problem of uneven local lithium-ion transmission rate that may be caused by setting the convex part and the concave part on the electrode sheet, reduce lithium deposition, and improve the battery cycle stability.

[0011] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In this article, unless otherwise specified, the data ranges include the endpoints. Description of the Drawings

[0012] Figure 1 Shown is a schematic structural diagram of a positive electrode sheet in an embodiment of the present invention.

[0013] Reference numerals: 1, positive electrode current collector; 2, positive electrode active material; 3, second surface; 4, first surface; 5, first concave part; 6, first convex part. Detailed Description of the Invention

[0014] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0015] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains.

[0016] In the present invention, the terms "battery", "lithium battery", "lithium-ion battery", and "lithium-ion secondary battery" all have the same meaning, and all refer to lithium-ion secondary batteries, which generally include an electrode assembly (such as a positive electrode sheet, a negative electrode sheet, and a separator), a container (housing) for accommodating the electrode assembly, and an electrolyte.

[0017] In the present invention, the term "C4-C10 carboxylic acid ester" refers to a carboxylic acid ester in which the number of carbon atoms in the hydrocarbon group (i.e., the carbon chain connected to the carboxyl group) in the carboxylic acid ester molecule is between 4 and 10.

[0018] In the present invention, the term "fluorinated carboxylic acid ester" refers to a compound formed by substituting a hydrogen atom in the carboxylic acid ester molecule with a fluorine atom. Among them, when the fluorinated derivative of the C4-C10 carboxylic acid ester is a fluorinated carboxylic acid ester, it refers to a compound formed by substituting a hydrogen atom in the C4-C10 carboxylic acid ester with a fluorine atom.

[0019] In the present invention, the term "C2-C10 mononitrile compound and its fluorinated derivative" refers to a nitrile compound containing only one cyano group and having 2 to 10 carbon atoms. The "fluorinated derivative of the C2-C10 mononitrile compound" refers to a compound formed by substituting a hydrogen atom in the hydrocarbon group of the mononitrile compound having 2 to 10 carbon atoms with a fluorine atom. Among them, the mononitrile compound and its fluorinated derivative include a saturated mononitrile compound and its fluorinated derivative, and also include an unsaturated mononitrile compound and its fluorinated derivative.

[0020] In the present invention, the term "C2-C10 polynitrile compound and its fluorinated derivative" refers to a nitrile compound containing two or more cyano groups and having 2 to 10 carbon atoms. The "fluorinated derivative of the C2-C10 polynitrile compound" refers to a compound formed by substituting a hydrogen atom in the hydrocarbon group of the polynitrile compound having 2 to 10 carbon atoms with a fluorine atom. Among them, the polynitrile compound and its fluorinated derivative include a saturated polynitrile compound and its fluorinated derivative, and also include an unsaturated polynitrile compound and its fluorinated derivative.

[0021] The present invention provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, and an electrolyte;

[0022] In the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface that are oppositely arranged. A plurality of first protrusions are arranged at intervals on the first surface, and a plurality of first depressions are correspondingly arranged on the second surface; the height of the first protrusion is denoted as H μm, and the diameter of the first protrusion is denoted as R mm. H and R satisfy: 0.2 ≤ H / R ≤ 80;

[0023] The electrolyte includes a carboxylic acid ester. Based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester is denoted as A %; A satisfies: 10 ≤ A ≤ 80;

[0024] The electrolyte includes a nitrile compound. Based on the total mass of the electrolyte, the mass percentage of the nitrile compound is denoted as B %; B satisfies: 3 ≤ B ≤ 30.

[0025] Exemplarily, the value of H / R can be, for example, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or any value within the range formed by any two of the above values.

[0026] Exemplarily, in the electrolyte, the mass percentage A% of the carboxylic acid ester can be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value within the range formed by any two of the above values.

[0027] Exemplarily, in the electrolyte, the mass percentage B% of the nitrile compound can be, for example, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or any value within the range formed by any two of the above values.

[0028] It should be noted that when calculating the value of the formula H / R, H and R are substituted into the formula with their corresponding values, without considering unit conversion. For example, when H = 20 μm and R = 2 mm, H / R = 20 / 2 = 10;

[0029] During the charge and discharge process of the battery, the insertion and extraction of lithium ions in the electrode sheet will cause a large volume change inside the battery. This volume change causes the electrode surface to bear a large extrusion force. The electrode surface at the arc part of the winding structure of the wound battery receives a greater extrusion force, so it is more likely to deform, which easily leads to insufficient electrolyte at the arc part, and the lithium ion transmission channel is restricted, resulting in the inability of lithium ions to reach the negative electrode surface smoothly for insertion, thereby triggering safety problems such as lithium deposition.

[0030] In the present invention, by providing a convex portion and a concave portion on the positive electrode sheet, such uneven texture enables a certain gap structure on the surface of the electrode sheet. Under the condition of bearing extrusion pressure, stress is released, thereby stabilizing the internal structure of the electrode sheet. Moreover, the concave portion formed on the electrode sheet and the space formed by the convex portion and the separator can store the electrolyte, providing a relatively stable storage space for the electrolyte, avoiding the problem of insufficient electrolyte at the stress concentration point of the electrode sheet, facilitating the normal conduction and transportation of lithium ions, and reducing the occurrence of lithium deposition problems. In addition, the uneven texture formed on the surface of the positive electrode sheet increases the specific surface area of the positive electrode sheet, and there are more transmission sites and paths for lithium ions to enter the interior of the electrode sheet, improving the transmission rate of lithium ions inside the electrode sheet, avoiding the accumulation of lithium ions on the surface of the electrode sheet during the fast charging process of the battery, and thus improving the fast charging performance of the battery. When forming the convex portion and the concave portion (such as by rolling), minute cracks will be generated on the surface of the positive electrode sheet. These cracks may cause the bending and rupture of the structure of the active material inside the positive electrode sheet, further resulting in the inability of lithium ions to be smoothly inserted and extracted, leading to a decline in battery performance. In addition, it is also prone to uneven compaction of the positive electrode sheet, which may cause abnormal local transmission rate of lithium ions, resulting in local lithium deposition. By introducing carboxylic esters and nitrile compounds as solvent components into the electrolyte, the electrolyte has a smaller viscosity and a higher dielectric constant, improving the conductivity of the electrolyte, accelerating the transmission rate of lithium ions, avoiding the large accumulation of lithium ions at the same position after lithium ions are extracted, and at the same time accelerating the transmission rate of lithium ions caused by concentration difference, making the distribution of lithium ions in the electrolyte more uniform and the transmission on the electrode sheet more uniform, effectively alleviating the problem of uneven local lithium ion transmission rate that may be caused during the formation of the convex portion or the concave portion, enabling the overall electrode surface to have a good lithium ion transmission rate, reducing local lithium deposition at the embossed part of the electrode surface, and improving the cycle stability of the battery.

[0031] In the present invention, by providing a convex portion and a concave portion on the electrode sheet and cooperating with the introduction of carboxylic esters and nitrile compounds as solvents into the electrolyte, the problem of lithium deposition during the high-rate charge and discharge process of the battery can be solved, reducing lithium deposition on the electrode surface, thereby reducing problems such as battery capacity attenuation and battery volume expansion caused by lithium deposition in the battery, and improving the fast charging cycle stability of the battery.

[0032] In some embodiments, the height (H) of the first protrusion and the diameter (R) of the first protrusion satisfy 0.2 ≤ H / R ≤ 80. When H / R > 80, the protrusion structure (or embossed structure) of the positive electrode sheet is relatively fragile and is easily affected by mechanical stress, resulting in the breakage of the embossed structure. On the one hand, the structure of the active material inside the electrode sheet may be damaged and deformed accordingly, affecting the normal insertion and extraction of lithium ions. On the other hand, during the battery cycling process, the SEI film on the surface of the electrode sheet may also be damaged as the surface structure of the electrode sheet deforms, leading to a decline in battery performance and possible safety issues. When H / R < 0.2, the embossing degree is relatively shallow, the formed embossed texture is not obvious, and there is no obvious difference between the embossed part and the non-embossed part, so the problems of unstable electrode sheet structure caused by stress extrusion and insufficient electrolyte cannot be effectively solved. At the same time, the embossing does not significantly increase the specific surface area of the electrode sheet, and the transmission rate of lithium ions between the electrolyte and the electrode sheet cannot be improved, so it cannot play a role. Preferably, when 0.75 ≤ H / R ≤ 20, the mechanical strength of the protrusion and the depression can be taken into account, and the fast charging performance and safety of the battery can be better improved.

[0033] In some embodiments, as Figure 1 shown, the entire surface of the positive electrode sheet is embossed. In the thickness direction of the positive electrode sheet, the positive electrode sheet includes a second surface 3 and a first surface 4 arranged opposite to each other. After the second surface 3 is embossed, a plurality of first depressions 5 evenly distributed at intervals are formed on the positive electrode sheet, and a plurality of first protrusions 6 evenly distributed at intervals corresponding to the first depressions 5 are formed on the first surface 4. Similarly, a plurality of first depressions 5 evenly distributed at intervals can also be formed after the first surface 4 is embossed, and a plurality of first protrusions 6 evenly distributed at intervals corresponding to the first depressions 5 are formed on the second surface 3, that is, the positions where the first protrusions 6 and the first depressions 5 are formed on the second surface 3 and the first surface 4 can be interchanged. The first protrusions or the first depressions can be evenly distributed at intervals or unevenly distributed at intervals, and preferably evenly distributed at intervals.

[0034] In some other embodiments, the embossing treatment can be performed only on a local area of the positive electrode sheet, such as the edge area, the arc area, etc.

[0035] In some embodiments, the first protrusion or the first depression (embossed pattern) is in a regular or irregular shape, such as a circle, a square, a hexagon, other regular shapes or irregular shapes, and preferably a regular shape, such as preferably a circle.

[0036] In some embodiments, the arrangement of the first protrusions and the first depressions can be evenly spaced, or the arrangement can be adjusted according to actual needs, such as partially evenly spaced and partially unevenly spaced.

[0037] In some embodiments, the first protrusion and / or the first recess satisfy at least one of the following conditions:

[0038] (a) The average spacing between adjacent first protrusions or adjacent first recesses is denoted as D. The average spacing between adjacent first protrusions (two adjacent first protrusions) is 0.5 mm - 8 mm. For example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, or any point value within the range formed by any two of the above values. Preferably, it is 1 mm - 4 mm; and / or, the average spacing between adjacent first recesses (two adjacent first recesses) is 0.5 mm - 8 mm. For example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, or any point value within the range formed by any two of the above values. Preferably, it is 1 mm - 4 mm. The average spacing between adjacent first protrusions and the average spacing between adjacent first recesses can be the same or different, preferably the same. The "average spacing between adjacent first protrusions" can be interpreted as the shortest straight-line distance on the surface of the positive electrode sheet between the edges of two adjacent and closest first protrusions in the length direction of the positive electrode sheet, as shown by D in Figure 1 ; the "average spacing between adjacent first recesses" can be interpreted as the shortest straight-line distance on the surface of the positive electrode sheet between the edges of two adjacent and closest first recesses in the length direction of the positive electrode sheet, as shown by D in Figure 1 .

[0039] When the average spacing of the first protrusions and / or the average spacing of the first recesses satisfy the above range, the arrangement density of the first protrusions and / or the first recesses is within a suitable range, and the number of the first protrusions and / or the first recesses is controlled within a certain area, which can not only effectively improve the fast charging performance of the battery, but also avoid the problem of unstable structure of the positive electrode sheet caused by too small average spacing.

[0040] (b)The height of the first protrusion is denoted as H. The height of the first protrusion can be 3 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any value within the range formed by any two of the above values; and / or, the depth of the first recess is 3 μm - 100 μm, for example, it can be 3 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any value within the range formed by any two of the above values. "The height of the first protrusion" can be interpreted as the maximum distance from the top end of the first protrusion away from the positive current collector to the first surface of the positive electrode sheet; "the depth of the first recess" can be interpreted as the maximum distance from the bottom end of the first recess close to the positive current collector to the second surface of the positive electrode sheet, as shown by H in Figure 1 When the height of the first protrusion and / or the depth of the first recess meet the above ranges, it is possible to avoid the situation where the height of the first protrusion is too high or the depth of the first recess is too deep, resulting in a fragile protrusion structure that is prone to structural fragmentation caused by mechanical extrusion wear; it is also possible to avoid the situation where the height of the first protrusion is too low or the depth of the first recess is too shallow, where the electrolyte cannot well infiltrate the inside of the positive electrode sheet, and the improvement of the battery fast charging performance is not obvious.

[0041] (c)The diameter of the first protrusion is denoted as R. The diameter of the first protrusion is 0.5 mm - 4 mm, for example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or any value within the range formed by any two of the above values, preferably 1 mm - 3 mm; and / or, the diameter of the first recess is 0.5 mm - 4 mm, for example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or any value within the range formed by any two of the above values, preferably 1 mm - 3 mm. "The diameter of the first protrusion" or "the diameter of the first recess" can be interpreted as the maximum straight-line distance between the two edges of the first protrusion or the first recess in the direction parallel to the positive electrode sheet, as shown by R in Figure 1 When the diameter of the first protrusion and / or the diameter of the first recess meet the above ranges, it is possible to control the area size of the first protrusion and / or the first recess, avoid the weakening of the strength of the positive electrode sheet due to too large a diameter, which is prone to physical structure damage resulting in the fragmentation of the surface structure of the positive electrode sheet and the deterioration of battery performance, and also avoid too small a diameter, where the electrolyte cannot well infiltrate the inside of the positive electrode sheet, and the improvement of the battery fast charging performance is not obvious.

[0042] In some embodiments, the carboxylic acid ester includes at least one of C4-C10 carboxylic acid esters and their fluorinated derivatives. Preferably, the carboxylic acid ester includes at least one of ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and difluoroethyl acetate.

[0043] In some embodiments, the nitrile compound includes at least one of C2-C10 mononitrile compounds and their fluorinated derivatives, and C2-C10 polynitrile compounds and their fluorinated derivatives. Preferably, the nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, isobutyronitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, benzonitrile, acrylonitrile, crotononitrile, trans-butenedinitrile, trans-hexenedinitrile, 1,2-bis(cyanoethoxy)ethane, and fluorinated derivatives of the nitrile compounds.

[0044] C4-C10 carboxylic acid esters have a relatively low viscosity and a relatively high dielectric constant (viscosity ≤ 1 mPa·s; dielectric constant ≥ 10); C2-C10 nitrile compounds have a moderate viscosity and a high dielectric constant (viscosity ≤ 2 mPa·s; dielectric constant ≥ 20). When the above-mentioned carboxylic acid esters and nitrile compounds are selected as the solvents of the electrolyte, the electrolyte can maintain a relatively low viscosity, further improve the conductivity of the electrolyte, obtain better kinetic performance, increase the transport rate of lithium ions in the electrolyte, and when infiltrating the electrode sheet, it can more effectively reduce the problem of the difference in the local transport rate of lithium ions in the electrode sheet, make the transport of lithium ions more uniform, reduce local lithium deposition in the battery, and further improve the fast charging performance and cycle safety of the battery.

[0045] In some embodiments, the carboxylic acid ester includes propyl propionate (PP) and difluoroethyl acetate (DFEA); in the electrolyte, the mass ratio of propyl propionate to difluoroethyl acetate is denoted as C, C satisfies: 1≤C≤10, and the value of C can be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any point value in the range consisting of any two of the above point values. The fluorine atoms in DFEA have a high oxidation potential. When used as a solvent for the electrolyte, it can significantly improve the antioxidant properties of the electrolyte, allowing the electrolyte to exist stably during high-voltage cycling, thereby improving the battery's cycling performance under high voltage. However, DFEA has poorer solubility in lithium salts than other carboxylates. When the DFEA content is too high, it often leads to the precipitation of lithium salts, the electrolyte cannot maintain a uniform state, and the battery performance (such as cycling performance and safety) is significantly reduced. PP is a carboxylate, and the carboxyl group (-COOH) or ester group (-COO-) in its molecular structure can form a strong interaction with the lithium ions in the lithium salt, and has good solubility for the lithium salt. When PP is used in combination with DFEA, the solubility of the lithium salt can be improved, reducing problems such as lithium salt precipitation when DFEA is used alone, while improving the high-voltage cycling performance of the battery. When PP and DFEA are added to the electrolyte and recessed and raised portions are set on the pole piece, the uneven texture on the pole piece surface not only helps the electrolyte to be evenly distributed and quickly penetrate the pole piece, but also further optimizes the transmission performance of the electrolyte, helps the dissolution and transmission of lithium salts in the electrolyte, and to a certain extent alleviates the risk of lithium salt precipitation caused by high DFEA content, while enhancing the cycle stability and safety of the battery at high voltage. Therefore, the combination of PP and DFEA with recessed and raised portions set on the pole piece can jointly solve the problems of electrolyte inhomogeneity and lithium salt precipitation, while improving the high-voltage cycle performance of the battery.

[0046] In some embodiments, the fluorinated derivative of the C4-C10 carboxylic acid ester is a fluorinated carboxylic acid ester; the nitrile compound includes an unsaturated nitrile; the unsaturated nitrile includes at least one of an unsaturated mononitrile compound and a fluorinated derivative thereof, an unsaturated polynitrile compound and a fluorinated derivative thereof; based on the total mass of the electrolyte, the total mass proportion of the fluorinated carboxylic acid ester and the unsaturated nitrile is recorded as D%, and D satisfies: 0≤D≤30, for example, it can be 0, 1%, 2%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30% or any point value in the range of the above two point values. The fluorinated carboxylic acid ester includes at least one of difluoroethyl acetate, trifluoroethyl acetate, ethyl 3-fluoropropionate, and ethyl 3,3,3-trifluoropropionate; and / or, the unsaturated nitrile includes at least one of acrylonitrile, crotononitrile, trans-butenedinitrile, and trans-hexenedinitrile.

[0047] Among carboxylic acid esters, fluorinated carboxylic acid esters have strong antioxidant properties due to the substitution of fluorine atoms, which can significantly improve the overall antioxidant performance of the electrolyte and reduce the oxidation and deterioration of the electrolyte; unsaturated nitriles in nitrile compounds not only have good antioxidant properties but also can participate in the formation of the SEI film on the surface of the electrode sheet, avoiding direct contact between the electrolyte and the electrode active material and reducing the occurrence of side reactions. However, fluorinated carboxylic acid esters and unsaturated nitriles usually have high viscosities. When their contents in the electrolyte are too high, the overall viscosity of the electrolyte will increase significantly, thereby reducing the conductivity of the electrolyte. Lithium ions cannot be normally transported in the electrolyte and are prone to lithium deposition on the electrode surface, resulting in a decline in battery performance. Since the surface of the electrode sheet is provided with protrusions and depressions, forming an uneven texture on the surface of the electrode sheet, it not only provides more penetration channels for the electrolyte, optimizes the transport performance of the electrolyte, alleviates to a certain extent the problems of increased electrolyte viscosity and decreased conductivity caused by high contents of fluorinated carboxylic acid esters and unsaturated nitriles, but also helps to guide the uniform distribution and transport of lithium ions on the surface of the electrode sheet, reducing the risk of lithium deposition. Therefore, further adjusting the total mass ratio of the fluorinated carboxylic acid ester and the unsaturated nitrile to meet the above range, in combination with the setting of the depressions and protrusions on the surface of the electrode sheet, can improve the high-voltage cycling performance of the battery while taking into account the fast charging performance of the battery.

[0048] In some embodiments, the electrolyte includes fluorobenzene compounds; based on the total mass of the electrolyte, the mass ratio of the fluorobenzene compounds is denoted as E %; E satisfies: 2 ≤ E ≤ 20, for example, it can be 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20% or any value in the range composed of any two of the above values. Preferably, the fluorobenzene compounds include at least one of fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, perfluorobenzene, and fluorinated aromatic compounds of the fluorobenzenes listed above.

[0049] By providing raised and recessed portions on the surface of the electrode sheet, although the specific surface area of the electrode sheet is improved and the rate of lithium ion insertion and extraction from the electrode sheet is increased, the tap density of the electrode sheet will also be relatively high, and the pores between materials will be relatively reduced, which is not conducive to the infiltration of the electrolyte and limits the further improvement of the fast charging performance of the battery. Fluorobenzene compounds, as aromatic fluoroalkanes, have strong aromaticity. The aromatic structure in fluorobenzene compounds can form π-π stacking interactions with the electrode structure, making it easier to enter the electrode sheet. When fluorobenzene compounds are introduced as one of the solvents in the electrolyte, the wettability of the electrolyte to the electrode sheet can be significantly improved, the insertion and extraction of lithium ions in the electrode sheet can be accelerated, lithium deposition on the electrode surface can be reduced, and the fast charging performance of the battery can be further optimized. However, fluorobenzene compounds have low polarity and low solubility for lithium salts. If the content is too high, precipitation of lithium salts will occur. When the content of fluorobenzene compounds is adjusted within the above range in the present invention, the problem of lithium salt precipitation caused by too high content of fluorobenzene compounds can be avoided, ensuring that fluorobenzene compounds can play a role and do not deteriorate other battery performance (such as cycle performance and safety, etc.).

[0050] In some embodiments, the electrolyte includes a lithium salt; based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% - 20%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 19%, 20% or any value within the range composed of any two of the above values.

[0051] In some embodiments, the lithium inorganic salt includes LiPF 6 、LiBF 4 、LiPO 2 F 2 at least one of them.

[0052] In some embodiments, the lithium organic salt includes at least one of LiBOB, LiODFP, LiODFB, LiTFSI, LiFSI, LiDTI.

[0053] Lithium ions, as the main medium for transmission between the positive and negative electrodes of a lithium battery, its content is directly related to battery performance. Especially in a battery system that requires fast charging and discharging, adjusting the content ratio of the lithium salt to meet the above range can avoid the increase in electrolyte viscosity that may occur when the lithium salt content is too high, which affects the transmission of lithium ions in the electrolyte and even leads to lithium deposition problems; avoid the reduction of the fast charging performance of the battery and the decrease in energy density when the lithium salt content is too low, which affects the cycle life of the battery.

[0054] It should be noted that the mass percentage (A) of the carboxylic acid ester, the mass percentage (B) of the nitrile compound, the mass percentage of propyl propionate, the mass percentage of difluoroethyl acetate, the mass percentage of fluorinated carboxylic acid ester, the mass percentage of unsaturated nitrile, and the mass percentage (E) of the fluorobenzene compound in the present invention can all be obtained by gas chromatography-mass spectrometry (GCMS).

[0055] In some embodiments, the electrolyte includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl propyl carbonate (MPC).

[0056] In some embodiments, the positive electrode active material layer further includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0057] In some embodiments, the mass percentage content of each component in the positive electrode active material layer is: 90 wt%-99.2 wt% of the positive electrode active material, 0.4 wt%-5 wt% of the positive electrode conductive agent, and 0.4 wt%-5 wt% of the positive electrode binder.

[0058] In some embodiments, the positive electrode active material is selected from one or more of transition metal lithium oxides, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, and lithium-rich manganese manganate; the chemical formula of the transition metal lithium oxide is Li （1+x） Ni y Co z M （1-y-z） O 2 , where -0.1 ≤ x ≤ 1; 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and 0 ≤ y + z ≤ 1; where M is one or several of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr. The positive electrode conductive agent is not specifically limited. For example, conventional conductive agents in the art can be selected, including but not limited to one or more of acetylene black, conductive carbon black, Ketjen black, conductive graphite, carbon nanotubes, conductive carbon fibers, and graphene. The positive electrode binder is not specifically limited. For example, conventional binders in the art can be selected, including but not limited to one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyethylene oxide.

[0059] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0060] In some embodiments, the mass percentage of each component in the negative electrode active material layer is as follows: 90 wt% - 99.2 wt% of negative electrode active material, 0.3 wt% - 5 wt% of negative electrode conductive agent, and 0.5 wt% - 5 wt% of negative electrode binder.

[0061] In some embodiments, the negative electrode active material includes a composite material of one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon carbon, silicon oxide, nano-silicon, and silicon alloy. The types of the negative electrode conductive agent and the negative electrode binder are not specifically limited, and conventional conductive agents and binders in the art can be selected. The types of the negative electrode conductive agent include but are not limited to at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, and metal powder. The negative electrode binder includes, for example, but is not limited to at least one of styrene-butadiene rubber latex, polytetrafluoroethylene latex, sodium carboxymethyl cellulose, sodium alginate, polyvinyl alcohol, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, and carboxylated chitosan.

[0062] In the present invention, the type of the separator is not specifically limited. For example, conventional lithium-ion battery separators in the art can be selected, including but not limited to woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, separator papers, rolled membranes, polyethylene microporous membranes, polypropylene microporous membranes, etc.

[0063] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the protection scope of the present invention.

[0064] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0065] The present invention will be described in detail below with reference to specific embodiments, and these embodiments are for understanding rather than limiting the present invention.

[0066] Example 1-1:

[0067] 1. Preparation of the positive electrode sheet

[0068] Lithium cobaltate, a conductive agent (a mixture of conductive carbon black and carbon nanotube), and PVDF were placed in NMP according to a mass ratio of 97.60:1.35:1.05, and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on both sides of a 9-μm aluminum foil, and the coating surface density was 0.01704 g / cm 2 ; and then dried and roll-pressed (the roll-pressed compaction was 4.2 g / cm 2)Treatment was carried out to obtain a positive electrode sheet with a single-sided thickness of the positive electrode active material layer of 90 μm; the cut positive electrode sheet was processed with a special roller with protrusions, and the height of the protrusions was 20 μm, the diameter was 2 mm, and the average spacing of the protrusions was 3 mm.

[0069] 2. Preparation of negative electrode sheet

[0070] Silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were placed in deionized water according to a mass ratio of 97.2:0.5:1.3:1. Among them, in the silicon-containing artificial graphite, the silicon content was 10%; after the above slurry was stirred evenly, a negative electrode slurry was obtained; the negative electrode slurry was evenly coated on a negative electrode current collector, and after drying, rolling, and slitting treatments in sequence, a negative electrode sheet was obtained.

[0071] 3. Preparation of electrolyte

[0072] In a glove box filled with argon (moisture < 1 ppm, oxygen content < 1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and propyl propionate (PP) were mixed into a uniform solvent, and LiPF with a mass fraction of 14% based on the total mass of the electrolyte was slowly added. 6 , 15% of fluoroacetonitrile. After stirring evenly, the required lithium-ion battery electrolyte was obtained. Based on the total mass of the electrolyte, the mass fraction of PP was 45%. The total amount of EC and DEC can be calculated, and the mass ratio of the two was 1:1.

[0073] 4. Preparation of lithium-ion battery

[0074] After the cut positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, they were wound into a wound-type structure battery core. After the battery core was encapsulated, injected with electrolyte, formed, and secondarily sealed, etc., a lithium-ion battery was obtained. Among them, the separator used a 9-μm-thick base material + alumina ceramic + PVDF adhesive separator.

[0075] Performance test

[0076] (1) 25°C cycle performance test

[0077] The batteries prepared in the examples and comparative examples were charged and discharged in a cycle of 500 weeks at a rate of 1C within the charge and discharge cut-off voltage range (3.0V - 4.5V) at 25°C. The discharge capacity measured in the first week was recorded as x1 mAh, and the thickness of the tested battery was y1; the discharge capacity measured in the 500th week was recorded as x2 mAh, and the thickness of the battery after the 500th week was y2; the cycle capacity retention rate R1 in the 500th week = x2 / x1; the battery thickness expansion rate H1 in the 500th week = (y2 - y1) / y1.

[0078] (2) 45°C cycle performance test

[0079] The batteries prepared in the examples and comparative examples were subjected to charge-discharge cycling 500 times at a rate of 1C at 45°C within the charge-discharge cut-off voltage range (3.0V - 4.5V). The discharge capacity measured in the first week was denoted as x3 mAh, and the thickness of the tested battery was y3; the discharge capacity measured in the 500th week was denoted as x4 mAh, and the thickness of the battery after the 500th week was y4; the cycle capacity retention rate R2 in the 500th week = x4 / x3; the battery thickness expansion rate H2 in the 500th week = (y4 - y3) / y3.

[0080] (3)25°C 4.7V Cycle Performance Test

[0081] The batteries prepared in the examples and comparative examples were subjected to charge-discharge cycling 300 times at a rate of 1C at 25°C within the charge-discharge cut-off voltage range (3.0V - 4.7V). The discharge capacity measured in the first week was denoted as x1 mAh, and the thickness of the tested battery was y1; the discharge capacity measured in the 300th week was denoted as x2 mAh, and the thickness of the battery after the 300th week was y2; the cycle capacity retention rate R in the 300th week = x2 / x1; the battery thickness expansion rate H in the 300th week = (y2 - y1) / y1.

[0082] (4)Lithium Deposition Analysis Test

[0083] The batteries prepared in the examples and comparative examples were charged at a constant current of 3C and a constant voltage to 4.5V at 25°C, with a cut-off current of 0.05C, and then discharged at a constant current of 0.5C to 3.0V. After cycling 20 times in this way, the battery was fully charged and then dissected to observe the lithium deposition situation, where the degree of lithium deposition from light to heavy was no lithium deposition, slight lithium deposition, lithium deposition, and severe lithium deposition in turn.

[0084] Groups 1 - 3 of the examples and Comparative Examples 1 - 5 were carried out with reference to Example 1 - 1, and the main differences are shown in Table 1. Among them, in Group 1 of the examples, the height (H) and / or the diameter (R) of the first convex part were changed, and the ratio of H / R was changed. In Group 2 of the examples, the mass percentage (A) of carboxylic ester in the electrolyte was changed. In Group 3 of the examples, the mass percentage (B) of nitrile compound in the electrolyte was changed. In Comparative Example 1, the ratio of H / R was too small and not within the protection scope of the present invention. In Comparative Example 2, the ratio of H / R was too large and not within the protection scope of the present invention. In Comparative Example 3, the mass percentage of carboxylic ester in the electrolyte was too small and not within the protection scope of the present invention. In Comparative Example 4, the mass percentage of nitrile compound in the electrolyte was too large and not within the protection scope of the present invention. In Comparative Example 5, the electrode sheet was not subjected to embossing treatment.

[0085] Table 1

[0086]

[0087] Note: "*" indicates that the corresponding parameters in this example or comparative example are the same as those in Example 1-1. " / " indicates that the corresponding parameters are not tested.

[0088] The larger the ratio of H / R, the sharper the shape of the electrode tab embossing. During the charge and discharge process of the battery, the deformation of the electrode tab is more likely to cause damage and rupture of the electrode tab structure. The smaller the ratio of H / R, the flatter the shape of the electrode tab embossing, and the embossing trace is relatively shallow, unable to exert the advantages and functions of embossing. When the content of carboxylic ester in the electrolyte is too high, it will reduce the antioxidant property of the electrolyte. When the content of nitrile compound is too high, the stability of the battery negative electrode interface is poor. When the contents of carboxylic ester and nitrile compound are too low, they cannot play the role of improving the conductivity of the electrolyte and reducing the viscosity of the electrolyte, resulting in a decline in battery performance. As can be seen from Table 1, by adjusting H and R to satisfy: 0.2 ≤ H / R ≤ 80; A to satisfy: 10 ≤ A ≤ 80; B to satisfy: 3 ≤ B ≤ 30, the present invention can reduce lithium plating, improve the fast charging performance of the battery, and enhance the cycle stability of the battery.

[0089] Four groups of Examples were carried out with reference to Example 1-1, and the main differences are shown in Table 2. Among them, in the four groups of Examples, the types of carboxylic esters were changed.

[0090] Table 2

[0091]

[0092] As can be seen from Table 2, selecting different types of carboxylic esters in the present invention can achieve similar effects, all of which can improve the fast charging performance of the battery, enhance the cycle stability of the battery, and reduce lithium plating.

[0093] Five groups of Examples were carried out with reference to Example 1-1, and the main differences are shown in Table 3. Among them, in the five groups of Examples, the types of nitrile compounds were changed.

[0094] Table 3

[0095]

[0096] As can be seen from Table 3, selecting different nitrile compounds can achieve similar effects, all of which can improve the fast charging performance of the battery, enhance the cycle stability of the battery, and reduce lithium plating.

[0097] Six groups of Examples were carried out with reference to Example 1-1, and the main differences are shown in Table 4. Among them, in the six groups of Examples, the convex part processing was carried out using special rollers with different parameters having convex parts, so that the average spacing of the first convex parts was changed.

[0098] Table 4

[0099]

[0100] As can be seen from Table 4, when the average spacing is too small, the electrode sheet is more likely to deform during the charge and discharge process of the battery, which easily leads to the damage and rupture of the electrode sheet structure and the decline of battery performance; when the average spacing is too large, the embossing density on the surface of the electrode sheet is too small, and the effect after embossing cannot be fully exerted. When the average spacing of the first convex part and the average spacing of the first concave part satisfy the range of 0.5 mm - 8 mm, the fast charging performance of the battery can be improved, the cycle stability of the battery can be enhanced, and lithium deposition can be reduced.

[0101] Seven groups of Examples were carried out with reference to Example 1-1, and the main differences are shown in Table 5. Among them, in the seven groups of Examples, difluoroethyl acetate (DFEA) was further added to the electrolyte, and the mass ratio C of propyl propionate (PP) to difluoroethyl acetate (DFEA) was changed.

[0102] Table 5

[0103]

[0104] Note: " / " indicates that the corresponding parameter was not tested.

[0105] As can be seen from Table 5, when the value of the mass ratio C of PP to DFEA is too large, it means that the mass proportion of DFEA in the electrolyte is too low, the antioxidant property of the electrolyte is worse, and the battery performance is worse. At the same time, when the value of C is too small, the viscosity of the electrolyte is too high, the solubility of the lithium salt is too low, lithium deposition is serious, and the battery performance declines more. When C satisfies 1 ≤ C ≤ 10, the cycle performance of the battery at high voltage can be further improved, and the fast charging performance of the battery can be taken into account.

[0106] Eight groups of Examples were carried out with reference to Example 7-1, and the main differences are shown in Table 6. Among them, in the eight groups of Examples, the nitrile compound type in the original electrolyte, fluoroacetonitrile, was replaced with trans-hexenedinitrile, and the total mass proportion D% of fluoroalkyl carboxylate (DFEA) and unsaturated nitrile (trans-hexenedinitrile) was changed.

[0107] Table 6

[0108]

[0109] As can be seen from Table 6, when the nitrile compound in the electrolyte is unsaturated nitrile (trans-hexenedinitrile), when used in combination with fluoroalkyl carboxylate (DFEA), the antioxidant property of the electrolyte will be further enhanced. Combining with the electrode sheet embossing process, the high-voltage cycle performance of the battery can be further improved while taking into account the fast charging performance of the battery. However, if too much unsaturated nitrile and fluoroalkyl carboxylate are added to the electrolyte, the viscosity of the electrolyte will become too large, deteriorating the battery performance.

[0110] Nine groups of Examples were carried out with reference to Example 8-1, and the main differences are shown in Table 7. Among them, in the nine groups of Examples, fluorobenzene (fluorobenzene compound) was further added to the electrolyte, and the mass proportion E% of fluorobenzene in the electrolyte was adjusted.

[0111] Table 7

[0112]

[0113] As can be seen from Table 7, when a fluorobenzene compound is further added to the electrolyte and E satisfies 2 ≤ E ≤ 10, the lithium deposition on the electrode surface can be further reduced, the fast charging performance of the battery can be optimized, and the cycle stability of the battery can be improved; it is necessary to avoid too large E, which may lead to poor solubility of the lithium salt and reduced battery performance.

[0114] It should be noted that in this text, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such a process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, the features described with reference to certain examples may be combined in other examples.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lithium ion battery, characterized in that: The battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte; In the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface arranged opposite to each other, the first surface is provided with a plurality of first protrusions at intervals, and the second surface is provided with a plurality of first recessed portions correspondingly; the height of the first protrusion is recorded as H μm, the diameter of the first protrusion is recorded as R mm, H and R satisfy: 0.75≤H / R≤20; the average spacing between adjacent first protrusions is 0.5 mm-8 mm, and the average spacing between adjacent first recessed portions is 0.5 mm-8 mm; The electrolyte includes carboxylic acid ester, and the mass ratio of the carboxylic acid ester is recorded as A% based on the total mass of the electrolyte; A satisfies: 10≤A≤80; the carboxylic acid ester includes propyl propionate and difluoroethyl acetate; in the electrolyte, the mass ratio of propyl propionate to difluoroethyl acetate is recorded as C, and C satisfies: 1≤C≤10; The electrolyte includes nitrile compounds, and the mass proportion of the nitrile compounds based on the total mass of the electrolyte is recorded as B%; B satisfies: 3≤B≤30; the nitrile compounds include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,3,6-hexanetrinitrile, benzonitrile, acrylonitrile, crotononitrile, trans-butenedinitrile, trans-hexenedinitrile, 1,2-bis(cyanoethoxy)ethane, and at least one of the fluorinated derivatives of the nitrile compounds.

2. The battery according to claim 1, characterized in that The carboxylic acid esters further include at least one of other C4-C10 carboxylic acid esters and fluorinated derivatives thereof except propyl propionate and difluoroethyl acetate.

3. The battery according to claim 2, characterized in that The carboxylic acid ester further comprises at least one of ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, and propyl butyrate.

4. The battery according to claim 1, characterized in that The electrolyte includes a fluorocarboxylic acid ester and an unsaturated nitrile, wherein the fluorocarboxylic acid ester includes difluoroethyl acetate; the unsaturated nitrile includes at least one of acrylonitrile, crotononitrile, trans-butenedinitrile, and trans-hexenedinitrile; based on the total mass of the electrolyte, the total mass proportion of the fluorocarboxylic acid ester and the unsaturated nitrile is denoted as D%, and D satisfies: 0≤D≤30.

5. The battery according to claim 2, characterized in that The electrolyte includes a fluorocarboxylic acid ester and an unsaturated nitrile, wherein the fluorocarboxylic acid ester includes difluoroethyl acetate and a fluorinated derivative of other C4-C10 carboxylic acid esters; based on the total mass of the electrolyte, the total mass proportion of the fluorocarboxylic acid ester and the unsaturated nitrile is denoted as D%, and D satisfies: 0≤D≤30.

6. The battery according to claim 5, characterized in that The other fluorinated derivatives of C4-C10 carboxylates include at least one of trifluoroethyl acetate, ethyl 3-fluoropropionate, and ethyl 3,3,3-trifluoropropionate; And / or, the unsaturated nitrile includes at least one of acrylonitrile, crotononitrile, trans-butenedinitrile and trans-hexenedinitrile.

7. The battery according to any one of claims 1 to 6, characterized in that: The first protrusion and / or the first depression satisfies at least one of the following conditions: (b) the height of the first protrusion is 3 μm-100 μm; and / or the depth of the first depression is 3 μm-100 μm; (c) the diameter of the first protrusion is 0.5 mm to 4 mm; and / or the diameter of the first depression is 0.5 mm to 4 mm.

8. The battery according to claim 7, characterized in that The first protrusion and / or the first depression satisfies at least one of the following conditions: (a) the average spacing between adjacent first protrusions is 1 mm to 4 mm; and / or the average spacing between adjacent first depressions is 1 mm to 4 mm; (b) the height of the first protrusion is 5 μm-80 μm; and / or the depth of the first depression is 5 μm-80 μm; (c) the diameter of the first protrusion is 1 mm to 3 mm; and / or the diameter of the first depression is 1 mm to 3 mm.

9. The battery according to any one of claims 1 to 6, characterized in that: The electrolyte includes a fluorobenzene compound; Based on the total mass of the electrolyte, the mass proportion of the fluorobenzene compound is denoted as E%; and E satisfies: 2≤E≤20.

10. The battery according to claim 9, characterized in that The fluorobenzene compounds include fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, perfluorobenzene, and at least one of the fluorinated aromatic compounds of the fluorobenzenes.

11. The battery according to any one of claims 1 to 6, characterized in that: The electrolyte includes a lithium salt; the mass of the lithium salt accounts for 5%-20% of the total mass of the electrolyte; The lithium salt includes a lithium-containing inorganic salt and / or a lithium-containing organic salt.

12. The battery according to claim 11, characterized in that The lithium-containing inorganic salt includes at least one of LiPF6, LiBF4, and LiPO2F2; And / or, the lithium-containing organic salt includes at least one of LiBOB, LiODFP, LiODFB, LiTFSI, LiFSI, and LiDTI.

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