An electrochemical device and an electronic device

Abstract

The application provides an electrochemical device and an electronic device, which comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the electrolyte comprises a compound of formula I, the mass percentage of the compound of formula I is x%, 0.01≤x≤5, based on the mass of the electrolyte; the positive electrode sheet comprises a positive electrode current collector and a first positive electrode material layer and a second positive electrode material layer on at least one surface of the positive electrode current collector, the first positive electrode material layer is between the positive electrode current collector and the second positive electrode material layer, the first positive electrode material layer comprises Mn elements and the thickness is h1μm, the thickness of the second positive electrode material layer is h2μm, x and h1 satisfy the relationship: 0.00033≤x / h1≤0.1. By adjusting the compound of formula I and the thickness h1 of the first positive electrode material layer, the value of x / h1 is controlled within the range of the application, the film forming stability of the positive and negative electrode surfaces, the structural stability of the positive electrode sheet and the dissolution of Mn 2+ are effectively improved, so that the cycle performance, storage performance and safety performance of the electrochemical device are effectively improved.

Description

Technical Field

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

[0002] With the widespread adoption and application of smart products, demand for electronic products such as mobile phones, laptops, and cameras is increasing year by year. As the power source for these electronic products, lithium-ion batteries, with their high energy density, lack of memory effect, and high operating voltage, are gradually replacing traditional Ni-Cd and MH-Ni batteries. However, as electronic products become thinner and more portable, the demand for lithium-ion batteries continues to increase. The development of highly safe and long-life lithium-ion batteries is a key market demand. Summary of the Invention

[0003] The purpose of this application is to provide an electrochemical device and an electronic device to improve the cycling performance, storage performance, and safety performance of the electrochemical device. The specific technical solution is as follows:

[0004] A first aspect of the present application provides an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the electrolyte comprises at least one compound of formula I:

[0005]

[0006] In the compound of formula I, R 11 and R 12 are independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkynyl, substituted or unsubstituted C1 to C 10 Alkoxy or substituted or unsubstituted C1 to C 10 Acyloxy; when substituted, the substituent is selected from a halogen atom, a C2 to C5 cycloalkyl group or a C6 to C 12 Aromatic group.

[0007] In the compound of formula I, X 11 ¯Anionic group is selected from PF6¯, F¯, NO3¯, PO2F2¯, BF4¯, (FSO2)2N¯, CF3SO2O¯,

[0008] 、 、 、 、 、 or Any of;

[0009] The mass percentage content of the compound of Formula I is x%, 0.01≤x≤5 based on the mass of the electrolyte; the positive electrode plate comprises a positive electrode current collector and a first positive electrode material layer and a second positive electrode material layer located on at least one surface of the positive electrode current collector, the first positive electrode material layer is located between the positive electrode current collector and the second positive electrode material layer, the first positive electrode material layer comprises Mn element and has a thickness of h1 μm, the second positive electrode material layer has a thickness of h2 μm, wherein the ratio of the thickness h1 of the first positive electrode material layer to the thickness h2 of the second positive electrode material layer is k; x and h1 satisfy the relationship: 0.00033≤x / h1≤0.1. By adjusting the type and mass percentage content of the compound of Formula I and the ratio x / h1 of the content of the compound of Formula I to the thickness of the first positive electrode material layer, the surface film stability of the positive and negative electrodes, the structural stability of the positive electrode plate, and the dissolution of Mn 2+ can be effectively improved within the scope of the present application, thereby effectively improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0010] In an embodiment of the present application, the electrochemical device satisfies at least one of the following characteristics: (1) 30≤h1≤200; (2) 0.5≤k≤150; (3) 0.005≤x / h1≤0.1. By adjusting the thickness of the first positive electrode material layer, k or x / h1 to satisfy at least one of the above characteristics, the cycle performance, storage performance and safety performance of the electrochemical device can be improved.

[0011] In an embodiment of the present application, the compound of Formula I comprises at least one of the following compounds:

[0012] .

[0013] By selecting the compound of Formula I, the compound of Formula I can combine with Lewis acid, effectively eliminate Lewis acid such as HF or PF5, inhibit the dissolution of transition metal from the positive electrode caused by Lewis acid; and form a better SEI film on the negative electrode, prevent the decomposition of electrolyte due to the destruction of the film, effectively improve the surface film stability of the positive and negative electrodes, the structural stability of the positive electrode plate, so that the electrochemical device has good cycle performance, storage performance and safety performance at the same time.

[0014] In an embodiment of the present application, the electrolyte further comprises a silane compound containing unsaturated bond, and the silane compound containing unsaturated bond is selected from at least one of the compounds of Formula II:

[0015]

[0016] wherein, R 21 , R 22 , R23 and R 24 each independently is selected from any one of a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 alkyl group, a substituted or unsubstituted C2 to C 10 alkenyl group, a substituted or unsubstituted C2 to C 10 alkynyl group, a substituted or unsubstituted C1 to C 10 heteroatom-containing functional group, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 , R 22 , R 23 and R 24 may form a ring between any two groups; wherein, R 21 , R 22 , R 23 and R 24 contains at least one unsaturated bond; the mass percentage content of the compound of formula II is f%, 0.01≤f≤1, based on the mass of the electrolyte, by regulating the type and mass percentage of the compound of formula II within the scope of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be improved.

[0017] In an embodiment of the present application, the compound of formula II includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilyl) maleate, tetraallylsilane, pentamethylpentaethenylcyclopentasiloxane, vinyltrimethylsilane, divinyl dimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethylenedisiloxane, triethenylmethylsilane, triethylvinylsilane, allyltriethoxysilane, triethylsilylacetylene, tetraethenylsilane, triacetoxyethylsilane, tetramethyltetraethenylcyclo tetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane or vinyltriethoxysilane. By selecting the above-mentioned compound of formula II, the chemical stability of the electrolyte can be improved, thereby further improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0018] In an embodiment of the present application, the first positive electrode material layer includes a first positive electrode active material, the first positive electrode active material includes at least one of lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium iron manganese phosphate, lithium manganese phosphate or lithium-rich manganese-based material, and the mass percentage content of Mn element in the first positive electrode material layer is y1%, 20≤y1≤60, based on the mass of the first positive electrode material layer. By regulating the type of the first positive electrode active material and the mass percentage of Mn element within the scope of the present application, the first positive electrode material layer has a suitable content of Mn element, which can reduce the dissolution of Mn 2+ , thereby improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0019] In an embodiment of the present application, the second positive electrode material layer comprises a second positive electrode active material, the second positive electrode active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium vanadate, lithium nickelate, lithium nickel cobalt manganese phosphate, lithium-rich manganese-based material, lithium nickel cobalt aluminum phosphate or lithium titanate, the mass percentage of Mn element in the second positive electrode material layer is y2%, y1>y2, based on the mass of the second positive electrode material layer. By adjusting the type of the second positive electrode active material and the mass percentage of Mn element within the scope of the present application, the mass percentage of Mn element in the second positive electrode material layer is less than that in the first positive electrode material layer, which can reduce the contact area of the first positive electrode material layer with the electrolyte, reduce the dissolution of Mn element in the first positive electrode material layer, and further improve the cycle performance, storage performance and safety performance of the electrochemical device. 2+

[0020] In an embodiment of the present application, the first positive electrode material layer comprises a first positive electrode active material, the first positive electrode active material comprises at least one of lithium manganate or lithium iron manganese phosphate; the second positive electrode material layer comprises a second positive electrode active material, the second positive electrode active material comprises at least one of lithium iron phosphate or lithium nickel cobalt manganese phosphate.

[0021] In an embodiment of the present application, the electrolyte comprises a cyclic carbonate compound, the mass percentage of the cyclic carbonate compound is z%, 5≤z≤40, based on the mass of the electrolyte. By adjusting the mass percentage of the cyclic carbonate compound within the scope of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be improved.

[0022] In an embodiment of the present application, based on the thickness h1 of the first positive electrode material layer, 1.25≤h1 / z≤30. By adjusting the value of h1 / z within the scope of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be further improved.

[0023] In an embodiment of the present application, the cyclic carbonate compound comprises at least one of ethylene carbonate, propylene carbonate or butylene carbonate. By adjusting the type of the cyclic carbonate compound within the scope of the present application, the cycle performance, storage performance and safety performance can be further improved.

[0024] The second aspect of the present application provides an electronic device comprising the electrochemical device in any of the foregoing embodiments.

[0025] The beneficial effects of the present application are as follows:

[0026] ​The application provides an electrochemical device, which comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the electrolyte comprises a compound of formula I, the mass percentage of the compound of formula I is x%, 0.01≤x≤5 based on the mass of the electrolyte; the positive electrode sheet comprises a positive electrode current collector and a first positive electrode material layer and a second positive electrode material layer on at least one surface of the positive electrode current collector, the first positive electrode material layer is between the positive electrode current collector and the second positive electrode material layer, the first positive electrode material layer comprises Mn elements and has a thickness of h1 μm, the second positive electrode material layer has a thickness of h2 μm, x and h1 satisfy the relationship: 0.00033≤x / h1≤0.1. The positive electrode is double-coated, the inner positive electrode material layer has a high content of Mn elements, and the outer positive electrode material layer has a low content of Mn elements or does not contain Mn elements, so that the contact between the Mn-containing material and the electrolyte is reduced, the dissolution of Mn 2+ The compound of formula I can be combined with Lewis acid, can effectively remove Lewis acid, and inhibit the dissolution of transition metal from the positive electrode caused by Lewis acid; the compound of formula I can also form a good SEI film on the negative electrode, and prevent the decomposition of the electrolyte caused by the destruction of the film.

[0027] By adjusting the thickness h1 of the compound of formula I and the first positive electrode material layer, and controlling the value of x / h1 within the range of the application, the film formation stability of the positive and negative electrode surfaces, the structural stability of the positive electrode sheet, the dissolution of Mn 2+ , and the cycle performance, storage performance and safety performance of the electrochemical device can be effectively improved.

[0028] Of course, implementing any product or method of the application does not necessarily require achieving all the advantages described above at the same time. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the application clearer, the following examples are used to further illustrate the application. Obviously, the described examples are only some of the examples of the application, not all the examples. All other examples obtained by those skilled in the art based on the application are within the scope of protection of the application.

[0030] It should be noted that in the specific embodiments of the application, the lithium ion battery is used as an example of the secondary battery to explain the application, but the secondary battery of the application is not limited to the lithium ion battery.

[0031] The application provides an electrochemical device, which comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the electrolyte comprises at least one compound of formula I:

[0032]

[0033] wherein, R 11 and R 12are independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkynyl, substituted or unsubstituted C1 to C 10 Alkoxy or substituted or unsubstituted C1 to C 10 Acyloxy; when substituted, the substituent is selected from a halogen atom, a C2 to C5 cycloalkyl group or a C6 to C 12 aromatic groups;

[0034] X 11 ¯Anionic group is selected from PF6¯, F¯, NO3¯, PO2F2¯, BF4¯, (FSO2)2N¯, CF3SO2O¯,

[0035] 、 、 、 、 、 or Any of;

[0036] Based on the mass of the electrolyte, the mass percentage of the compound of formula I is x%, 0.01≤x≤5, illustratively, the value of x can be 0.01, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0 or a range consisting of any two of the above values; the positive electrode sheet comprises a positive electrode collector and a first positive electrode material layer and a second positive electrode material layer located on at least one surface of the positive electrode collector, the first positive electrode material layer being located between the positive electrode collector and the second positive electrode material layer, the first positive electrode material layer comprising a Mn element and having a thickness of h1 μm, and the second positive electrode material layer having a thickness of h2 μm, wherein the ratio h1 / h2 of the thickness h1 of the first positive electrode material layer and the thickness h2 of the second positive electrode material layer is k; x and h1 satisfy the relationship: 0.00033≤x / h1≤0.1, illustratively, the value of x / h1 can be 0.00033, 0.0006, 0.0009, 0.003, 0.006, 0.009, 0.03, 0.06, 0.09, 0.3, 0.6, 0.9, 1.0 or a range consisting of any two of the above values.

[0037] The inventors have found that, due to the rich and cheap manganese raw material, simple synthesis process, low price, easy industrialization production, small environmental pollution and good safety performance, lithium manganate material is usually used as the positive active material of the electrochemical device. However, in the electrochemical cycle process, the direct contact of the electrolyte with the positive material can cause the high-valence manganese ions to be reduced and Mn 2+ ions to be precipitated, the manganese loss in the active material, and the structure degradation and capacity attenuation of the electrode. The positive double-layer coating, the first positive material layer with high manganese element content coated in the inner layer, can reduce the contact between the first positive material layer and the electrolyte, reduce the Mn 2+ leaching, and thus improve the cycle performance, storage performance and safety performance of the electrochemical device. In addition, the addition of the compound represented by Formula I in the electrolyte can combine with Lewis acid, effectively eliminate Lewis acid such as HF or PF5, inhibit the leaching of transition metal from the positive electrode caused by Lewis acid, and the compound of Formula I can also form a better SEI film at the negative electrode, prevent the decomposition of the electrolyte caused by the destruction of the film, so that by adjusting the type and coating method of the positive material layer and the type and mass percentage of the compound of Formula I within the scope of the present application, the electrochemical device can have good cycle performance, storage performance and safety performance.

[0038] In an embodiment of the present application, the thickness of the first positive material layer is h1 μm, and 30≤h1≤200. Exemplarily, the value of h1 can be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200 or a range consisting of any two of the above values. By adjusting the thickness of the first positive material layer, the contact between the manganese-containing material and the electrolyte can be reduced and the Mn 2+ leaching can be reduced, thereby improving the cycle performance, storage performance and safety performance of the secondary battery.

[0039] In an embodiment of the present application, the ratio h1 / h2 of the thickness h1 μm of the first positive material layer to the thickness h2 μm of the second positive material layer is k, and 0.5≤k≤150. Exemplarily, the value of k can be 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 or a range consisting of any two of the above values. By adjusting the ratio k within the scope of the present application, the structure of the positive active material layer can be optimized, thereby making the electrochemical device have good cycle performance, storage performance and safety performance.

[0040] In one embodiment of the present application, 0.005≤x / h1≤0.1. Illustratively, the value of x / h1 can be 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1, or a range between any two of the above values. By adjusting the ratio of the content of the compound of Formula I to the thickness of the first positive electrode material layer, x / h1, and controlling the value of x / h1 to be within the above range, preferably the mass percentage content of the compound of Formula I and the thickness of the first positive electrode material layer, x / h1 is made to have a suitable value, the film formation stability on the surface of the positive electrode and the structural stability of the positive electrode sheet can be further improved, and the dissolution of Mn 2+ from the positive electrode is further reduced, thereby further improving the cycle performance, storage performance, and safety performance of the electrochemical device.

[0041] In one embodiment of the present application, the compound of Formula I includes at least one of the following compounds:

[0042] .

[0043] By selecting the compound of Formula I, the compound of Formula I can combine with Lewis acid, effectively eliminate Lewis acid such as HF or PF5, inhibit the dissolution of transition metal from the positive electrode caused by Lewis acid; and form a better SEI film on the negative electrode, prevent the decomposition of electrolyte caused by the destruction of the film, effectively improve the film formation stability on the surface of the positive electrode and the structural stability of the positive electrode sheet, so that the electrochemical device has good cycle performance, storage performance, and safety performance at the same time.

[0044] In one embodiment of the present application, the electrolyte further includes a silane compound containing an unsaturated bond, and the silane compound containing an unsaturated bond is selected from at least one of the compounds of Formula II:

[0045]

[0046] wherein R 21 , R 22 , R 23 , and R 24 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 alkyl group, a substituted or unsubstituted C2 to C 10 alkenyl group, a substituted or unsubstituted C2 to C 10 alkynyl group, and a substituted or unsubstituted C1 to C 10Any one of the heteroatom-containing functional groups of R, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 、R 22 、R 23 and R 24 Any two groups in can form a ring; 21 、R 22 、R 23 and R 24 The compound of formula II can form a protective film on the surface of the negative electrode, reducing the occurrence of reduction reaction, thereby further improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0047] In one embodiment of the present application, the mass percentage of the compound of formula II is f%, and 0.01≤f≤1. For example, the value of f can be 0.01, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range consisting of any two of the above values. By regulating the mass percentage of the compound of formula II within the scope of this application, the chemical stability of the electrolyte can be improved, thereby further improving the cycle performance, storage performance, and safety performance of the electrochemical device.

[0048] In one embodiment of the present application, the compound of formula II includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilyl)maleate, tetraallylsilane, pentamethylpentavinylcyclopentasiloxane, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetravinyldisiloxane, trivinylmethylsilane, triethylvinylsilane, allyltriethoxysilane, triethylsilylacetylene, tetravinylsilane, triacetoxyethylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane or vinyltriethoxysilane. The above-mentioned compound of formula II is selected to improve the chemical stability of the electrolyte, thereby further improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0049] In an embodiment of the present application, the first positive electrode material layer comprises a first positive electrode active material, the first positive electrode active material comprises at least one of lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium manganese iron phosphate, lithium manganese phosphate or lithium-rich manganese-based material, and the mass percentage of Mn element in the first positive electrode material layer is y1%, 20≤y≤60 based on the mass of the first positive electrode material layer. For example, the value of y1% can be 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60 or a range between any two of the above values. By adjusting the type of the first positive electrode active material and the mass percentage of Mn element in the first positive electrode material layer within the range of the present application, the first positive electrode active material can have a suitable content of Mn element, and the first positive electrode material layer can reduce the dissolution of Mn 2+ when in contact with the electrolyte, thereby effectively improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0050] In an embodiment of the present application, the second positive electrode material layer comprises a second positive electrode active material, the second positive electrode active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium vanadate, lithium nickelate, lithium nickel cobalt manganate, lithium-rich manganese-based material, lithium nickel cobalt aluminum phosphate or lithium titanate, and the mass percentage of Mn element in the second positive electrode material layer is y2%, y1>y2 based on the mass of the second positive electrode material layer. By adjusting the type of the second positive electrode active material and the mass percentage of Mn element in the second positive electrode material layer within the range of the present application, the mass percentage of Mn element in the second positive electrode material layer can be less than y1, which is different from the first positive electrode material layer. The second positive electrode material layer has a smaller content of Mn 2+ element and can reduce the contact area between the first positive electrode material layer and the electrolyte, thereby reducing the dissolution of Mn 2+ element from the first positive electrode material layer and further improving the cycle performance, storage performance and safety performance of the electrochemical device.

[0051] In an embodiment of the present application, the first positive electrode material layer comprises a first positive electrode active material, the first positive electrode active material comprises at least one of lithium manganate or lithium manganese iron phosphate; and the second positive electrode material layer comprises a second positive electrode active material, the second positive electrode active material comprises at least one of lithium iron phosphate or lithium nickel cobalt manganate. By adjusting the types of the first positive electrode active material and the second positive electrode active material within the range of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be further improved.

[0052] In one embodiment of the present application, the electrolyte further comprises a cyclic carbonate compound, and the mass percentage of the cyclic carbonate compound in the electrolyte is z%, 5≤z≤40. Exemplarily, z can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or a range between any two of the above values. By adjusting the mass percentage of the cyclic carbonate compound within the range of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be improved.

[0053] In one embodiment of the present application, the ratio of the thickness h1 of the first positive electrode material layer to the mass percentage z of the cyclic carbonate compound is h1 / z, 1.25≤h1 / z≤30. Exemplarily, h1 / z can be 1.25, 2.5, 3.75, 5, 6.25, 7.5, 8.75, 10, 11.25, 12.5, 13.75, 15, 16.25, 17.5, 18.75, 20, 21.25, 22.5, 23.75, 25, 26.25, 27.5, 28.75, 30, or a range between any two of the above values. By adjusting the value of h1 / z within the range of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be further improved.

[0054] In one embodiment of the present application, the cyclic carbonate compound comprises at least one of ethylene carbonate, propylene carbonate or butylene carbonate. By adjusting the type of the cyclic carbonate compound within the range of the present application, the cycle performance, storage performance and safety performance of the electrochemical device can be further improved.

[0055] In the present application, the features of the different components of the electrolyte described above can be combined, and the embodiments encompassed by the above combinations are all within the protection scope of the present application.

[0056] In the present application, the electrolyte solution further includes a lithium salt and a non-aqueous organic solvent. The lithium salt is not particularly limited in the present application as long as the object of the present application is achieved. For example, the lithium salt can include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. The content of the lithium salt in the electrolyte solution is not particularly limited in the present application as long as the object of the present application is achieved. For example, the mass percentage of the lithium salt is 8% to 15% based on the mass of the electrolyte solution. The non-aqueous solvent is not particularly limited in the present application as long as the object of the present application is achieved, and for example, the non-aqueous solvent can include, but is not limited to, at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, or other organic solvents. The carbonate compound described above can include, but is not limited to, at least one of a chain carbonate compound or a fluorinated carbonate compound. The chain carbonate compound described above can include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The fluorinated carbonate compound can include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, or trifluoromethyl ethylene carbonate. The carboxylic acid ester compound described above can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, or caprolactone. The ether compound described above can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents described above can include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The content of the non-aqueous solvent in the electrolyte solution is not particularly limited in the present application as long as the object of the present application is achieved. For example, the mass percentage of the non-aqueous solvent is 40% to 90%.

[0057] In the present application, the electrochemical device further includes a positive electrode tab including a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector in the thickness direction thereof, or can be disposed on both surfaces of the positive electrode current collector in the thickness direction thereof. It is to be noted that the "surface" herein can be the entire area of the positive electrode current collector, or can be a partial area of the positive electrode current collector, and the present application is not particularly limited, as long as the object of the present application can be achieved. The present application is not particularly limited to the positive electrode current collector, as long as the object of the present application can be achieved, and for example, can include an aluminum foil, an aluminum alloy foil, or a composite current collector (for example, an aluminum-carbon composite current collector), and the like.

[0058] The positive electrode material layer of the present application further includes a conductive agent and a binder, and the present application is not particularly limited to the conductive agent and the binder in the positive electrode material layer, as long as the object of the present application can be achieved. For example, the conductive agent can include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flaky graphite, graphene, a metal material, or a conductive polymer. The above-mentioned conductive carbon black can include, but is not limited to, Super P, acetylene black, or Ketjen black. The above-mentioned carbon nanotubes can include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers can include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal material can include, but is not limited to, metal powder and / or metal fibers, and specifically, the metal can include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above-mentioned conductive polymer can include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder can include, but is not limited to, at least one of polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene butadiene copolymer (SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, or potassium hydroxymethyl cellulose. The mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer is not particularly limited in the present application, and a person skilled in the art can select them according to the actual needs, as long as the object of the present application can be achieved.

[0059] The thickness of the positive electrode current collector is not particularly limited in the present application, as long as the object of the present application can be achieved, and for example, the thickness of the positive electrode current collector is 1 µm to 20 µm. The thickness of the positive electrode material layer is not particularly limited in the present application, as long as the object of the present application can be achieved, and for example, the thickness of the single-sided positive electrode material layer is 30 µm to 120 µm.

[0060] Optionally, the positive electrode sheet can further comprise a conductive layer between the positive current collector and the positive material layer. The composition of the conductive layer is not particularly limited in the present application, and can be a conductive layer commonly used in the art. The conductive layer comprises a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and can be at least one of the conductive agent and the binder described above. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application, and can be selected by a person skilled in the art according to actual needs, as long as the purpose of the present application can be achieved.

[0061] In the present application, the electrochemical device further comprises a negative electrode sheet comprising a negative current collector and a negative material layer disposed on at least one surface of the negative current collector. The above-mentioned "negative material layer disposed on at least one surface of the negative current collector" means that the negative material layer can be disposed on one surface of the negative current collector in the thickness direction of the negative current collector, or can be disposed on two surfaces of the negative current collector in the thickness direction of the negative current collector. It should be noted that the "surface" here can be the entire area of the negative current collector, or can be a partial area of the negative current collector, which is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The negative current collector is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example, can comprise a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam or a composite current collector, etc.

[0062] The negative material layer of the present application comprises a negative active material. The negative active material is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example, the negative active material can comprise natural graphite, artificial graphite, mesophase carbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), silicon-oxygen-carbon material, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12The negative electrode material layer of the present application further includes at least one of a binder, a conductive agent, and a thickening agent. The binder in the negative electrode material layer of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the binder can be at least one of the above-described binders. The conductive agent in the negative electrode material layer of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the conductive agent can be at least one of the above-described conductive agents. The thickening agent in the negative electrode material layer of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the thickening agent can be sodium carboxymethyl cellulose (CMC-Na). The mass ratio of the negative electrode active material, the conductive agent, the thickening agent, and the binder in the negative electrode material layer of the present application is not particularly limited, and a person skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0063] The thickness of the negative electrode current collector of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode current collector is 5 μm to 16 μm. The thickness of the negative electrode material layer of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the single-sided negative electrode material layer is 30 μm to 120 μm.

[0064] Optionally, the negative electrode sheet can further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The composition of the conductive layer of the present application is not particularly limited and can be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer of the present application are not particularly limited and can be at least one of the above-described conductive agents and the above-described binders. The mass ratio of the conductive agent and the binder in the conductive layer of the present application is not particularly limited, and a person skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0065] In the present application, the electrochemical device further includes a separator. The separator of the present application is not particularly limited as long as the object of the present application can be achieved. For example, the material of the separator can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the separator can include at least one of a woven film, a non-woven film, a microporous film, a composite film, a calendered film, or a spunlaid film.

[0066] In some embodiments of the present application, the separator can include a base layer and a surface treatment layer. The base layer can be a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the base layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0067] Optionally, a surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

[0068] In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited in the present application, and for example, the inorganic particles can include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder is not particularly limited in the present application, and for example, the binder can be at least one of the above-described binders. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0069] The thickness of the separator is not particularly limited in the present application, as long as the purpose of the present application is achieved, and for example, the thickness of the separator can be 3 μm to 30 μm.

[0070] The electrochemical device of the present application further includes a packaging bag for containing the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte, and other components known in the art in the electrochemical device, and the present application does not limit the above-described other components. The packaging bag is not particularly limited in the present application, and can be a packaging bag known in the art, as long as the purpose of the present application is achieved.

[0071] The type of the electrochemical device is not particularly limited in the present application, and it can include any device in which an electrochemical reaction occurs. In the present application, the electrochemical device can include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery (lithium ion polymer battery), etc.

[0072] The preparation process of the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited, for example, can include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding, etc. as needed to obtain a wound structure of the electrode assembly, placing the electrode assembly into a packaging bag, injecting an electrolyte into the packaging bag and sealing to obtain an electrochemical device; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, then fixing the four corners of the entire stack structure with tape to obtain a stack structure of the electrode assembly, placing the electrode assembly into a packaging bag, injecting an electrolyte into the packaging bag and sealing to obtain an electrochemical device. In addition, a current protection element, a guide plate, etc. can also be placed in the packaging bag as needed, thereby preventing the pressure inside the electrochemical device from rising, overcharging and discharging.

[0073] The second aspect of the present application provides an electronic device comprising the electrochemical device of any of the foregoing embodiments. Therefore, the electronic device provided by the present application has good use performance.

[0074] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the art. In some embodiments, the electronic device can include but is not limited to a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0075] Embodiments

[0076] Hereinafter, embodiments and comparative examples are given to more specifically explain the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0077] Test methods and equipment:

[0078] Cycling performance test:

[0079] The lithium ion battery was placed in a 25°C constant temperature oven and allowed to stand for 30 minutes to allow the lithium ion battery to reach a constant temperature. The lithium ion battery that reached a constant temperature was charged at 0.2C constant current to 4.2V at 25°C, charged at constant voltage to 0.05C at 4.2V, allowed to stand for 5 minutes, discharged at 0.2C constant current to 2.8V, allowed to stand for 5 minutes, and the initial discharge capacity C0 of the lithium ion battery was tested; then charged at 1C constant current to 4.2V, charged at constant voltage to 0.05C at 4.2V; allowed to stand for 5 minutes; then discharged at 1C constant current to 2.8V, allowed to stand for 5 minutes, which was one charge-discharge cycle. This charge-discharge cycle was repeated to 1000 cycles, and the discharge capacity C1 of the lithium ion battery after 1000 cycles was measured.

[0080] Capacity retention rate after 1000 cycles at 25°C = C1 / C0 x 100%.

[0081] Nail test

[0082] Ten lithium ion batteries to be tested were charged at a constant current of 0.5C rate to a voltage of 4.2V at room temperature, and further charged at a constant voltage of 4.2V to a current of 0.05C, so that they were in a full charge state of 4.2V. Then the lithium ion battery was nailed at room temperature, a nail with a diameter of 2.5mm (steel nail, material is carbon steel, taper is 16.5mm, total length of steel nail is 100mm) was used, the nail speed was 30mm / s, the nail depth was the taper of the steel nail passing through the lithium ion battery, and the lithium ion battery was observed for smoke, fire or explosion. If not, the lithium ion battery is considered to pass the nail test.

[0083] High temperature storage impedance (IMP) growth rate test

[0084] Three lithium ion batteries to be tested were charged at a constant current of 0.5C rate to a voltage of 4.2V at room temperature (25°C±3°C), and further charged at a constant voltage of 4.2V to a current of 0.05C, so that they were in a full charge state of 4.2V, an OCV / IMP tester was used to record the AC impedance of the battery at 1KHz, in units of mΩ, recorded as the initial impedance of the battery. Then placed in an oven at 85°C for 8h, after the end, the battery was placed in a condition of 25°C±3°C for 2h, then an OCV / IMP tester was used to record the AC impedance of the battery at 1KHz, in units of mΩ. Taking the initial impedance of the battery as the reference, the IMP growth rate after 8h storage at 85°C was compared.

[0085] Example 1-1

[0086] Preparation of positive electrode sheet

[0087] The first positive electrode active material lithium manganate (LiMn2O4), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75 wt% is prepared. After uniform stirring in a vacuum stirrer, a first positive electrode slurry is obtained. The second positive electrode active material lithium cobaltate (LiCoO2), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75 wt% is prepared. After uniform stirring in a vacuum stirrer, a second positive electrode slurry is obtained. The first positive electrode slurry is coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and dried at 85°C to obtain a first positive electrode material layer with a thickness of 100 μm. Then, the second positive electrode slurry is coated on the first positive electrode material layer, and dried at 85°C to obtain a second positive electrode material layer with a thickness of 50 μm. A single-sided coated positive electrode sheet is obtained. Then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with double-sided coated positive electrode material layers. After coating, the positive electrode sheet is cold-pressed and cut into a specification of 74 mm x 866 mm for use. The cold-pressed positive electrode material layer has a compacted density of 3.2 g / cm3. 3 .

[0088] <Manufacture of negative electrode sheet>

[0089] The negative electrode active material artificial graphite, conductive agent (Super P), thickening agent carboxymethyl cellulose sodium, and binder styrene-butadiene rubber are mixed in a mass ratio of 96.4:1.5:0.5:1.6, deionized water is added as a solvent, and a slurry with a solid content of 70 wt% is prepared. After uniform stirring in a vacuum stirrer, a negative electrode slurry is obtained. The negative electrode slurry is uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 8 μm, and dried at 110°C to obtain a single-sided coated negative electrode material layer with a coating thickness of 110 μm. Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with double-sided coated negative electrode material layers. After coating, the negative electrode sheet is cold-pressed and cut into a specification of 78 mm x 875 mm for use. The cold-pressed negative electrode material layer has a compacted density of 1.70 g / cm3. 3 .

[0090] <Separator>

[0091] The inorganic layer slurry was prepared by mixing alumina and PVDF in a mass ratio of 95:5, adding NMP as a solvent, adjusting the solid content to 12wt%, and stirring uniformly. The inorganic layer slurry was uniformly coated on one surface of a polyethylene substrate with a thickness of 9μm, and after drying, a single-sided inorganic layer coated separator with a coating thickness of 2μm was obtained. Then, the PVDF was stirred uniformly in NMP solvent to prepare a polymer layer slurry with a solid content of 25wt%, and then the polymer layer slurry was uniformly coated on the surface of the inorganic layer away from the substrate, and after drying, a single-sided inorganic layer and polymer layer coated separator was obtained. Then, the polymer layer slurry was uniformly coated on the other surface of the polyethylene substrate, and after drying, a separator with one side coated with an inorganic layer and a polymer layer and the other side coated only with a polymer layer was obtained. The areal density of the polymer layer coating was 0.15mg / cm 2 .

[0092] <Preparation of electrolyte>

[0093] In an argon atmosphere glove box with a water content of less than 10ppm, ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed to obtain a basic organic solvent, and then lithium salt lithium hexafluorophosphate was added to the basic organic solvent, dissolved and mixed uniformly. Then the compound of formula I-1 was added to obtain a non-aqueous electrolyte. Among them, the mass percentage of lithium salt is 12.5%, the mass percentage of compound of formula I is 1%, the mass percentage of EC is 20%, the mass percentage of PC is 20%, and the mass percentage of DEC is 46.5% based on the mass of the non-aqueous electrolyte.

[0094] <Preparation of lithium battery>

[0095] The positive electrode sheet, separator, negative electrode sheet, and separator prepared above were stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to act as a barrier, and then wound to obtain an electrode assembly; the electrode assembly was placed in an outer packaging aluminum plastic film, and after removing the water at 80℃, the prepared non-aqueous electrolyte was injected and packaged, and after standing, formation, degassing, edge cutting, shaping, and capacity testing processes, a lithium ion battery was obtained.

[0096] Examples 1-2 to 1-7

[0097] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0098] Among them, when the mass percentage x of the compound of formula I changes, the mass percentage of diethyl carbonate changes accordingly, and the mass percentages of lithium salt, ethylene carbonate and propylene carbonate remain unchanged. The mass percentages of compound of formula I, lithium salt, ethylene carbonate, propylene carbonate and diethyl carbonate add up to 100%.

[0099] Example 1-8

[0100] The rest is the same as Example 1-1 except that the positive electrode sheet is prepared according to the following steps in the <Preparation of positive electrode sheet>.

[0101] Preparation of positive electrode sheet

[0102] The first positive electrode active material lithium manganate (LiMn2O4), conductive agent Super P, binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared. After stirring uniformly in a vacuum stirrer, the first positive electrode slurry is obtained. The second positive electrode active material lithium cobaltate (LiCoO2), conductive agent Super P, binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared. After stirring uniformly in a vacuum stirrer, the second positive electrode slurry is obtained. The first positive electrode slurry is coated on one surface of the positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85℃ to obtain a first positive electrode material layer with a thickness of 150μm. Then the second positive electrode slurry is sprayed on the first positive electrode material layer using a spraying device, and dried at 85℃ to obtain a second positive electrode material layer with a thickness of 1μm. After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with double-coated positive electrode material layers. After coating, the positive electrode sheet is cold-pressed and cut into a specification of 74mm×866m for use. The compaction density of the positive electrode material layer after cold-pressing is 3.2g / cm 3 .

[0103] Example 1-9

[0104] The rest is the same as Example 1-1 except that the positive electrode sheet is prepared according to the following steps in the <Preparation of positive electrode sheet>.

[0105] Preparation of positive electrode sheet

[0106] The first positive electrode active material lithium manganate (LiMn2O4), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared. After uniform stirring in a vacuum stirrer, a first positive electrode slurry is obtained. The second positive electrode active material lithium cobaltate (LiCoO2), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared. After uniform stirring in a vacuum stirrer, a second positive electrode slurry is obtained. The first positive electrode slurry is coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85℃ to obtain a first positive electrode material layer with a thickness of 200μm. Then, the second positive electrode slurry is sprayed on the first positive electrode material layer using a spraying device, and dried at 85℃ to obtain a second positive electrode material layer with a thickness of 1μm. A single-sided coated positive electrode sheet is obtained. After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with double-sided coated positive electrode material layers. After coating, the positive electrode sheet is cold-pressed and cut into a specification of 74mm×866mm for use. The cold-pressed positive electrode material layer has a compacted density of 3.2g / cm 3 .

[0107] Examples 1-10 to 1-18

[0108] The rest is the same as Example 1-1, except that the relevant preparation parameters are adjusted according to Table 1.

[0109] wherein when the mass percentage content x of the compound of formula I changes, the mass percentage content of diethyl carbonate changes accordingly, and the mass percentage contents of the lithium salt, ethylene carbonate, and propylene carbonate remain unchanged. The sum of the mass percentage contents of the compound of formula I, the lithium salt, ethylene carbonate, propylene carbonate, and diethyl carbonate is 100%.

[0110] Example 2-1

[0111] The rest is the same as Example 1-1, except that the electrolyte is prepared according to the following steps in <Preparation of electrolyte>.

[0112] <Preparation of electrolyte>

[0113] In an argon atmosphere glove box with water content less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed to obtain a base organic solvent, then lithium salt lithium hexafluorophosphate was added into the base organic solvent, dissolved and mixed uniformly. Then compound of formula I-1 and compound of formula II tetramethyldivinyl disiloxane were added to obtain a non-aqueous electrolyte. Among them, the mass percentage of lithium salt was 12.5%, the mass percentage of compound of formula I was 1%, the mass percentage of tetramethyldivinyl disiloxane was 0.01%, the mass percentage of EC was 20%, the mass percentage of PC was 20%, and the mass percentage of DEC was 46.49% based on the mass of the non-aqueous electrolyte.

[0114] Examples 2-2 to 2-5

[0115] Except that compound of formula II was added in the electrolyte and the relevant preparation parameters were adjusted according to Table 2, the rest was the same as Example 1-1.

[0116] Among them, when the mass percentage f of compound of formula II changes, the mass percentage of diethyl carbonate changes accordingly, and the mass percentages of compound of formula I, lithium salt, ethylene carbonate and propylene carbonate remain unchanged. The sum of the mass percentages of compound of formula II, compound of formula I, lithium salt, ethylene carbonate, propylene carbonate and diethyl carbonate is 100%.

[0117] Example 3-1

[0118] Except that the electrolyte was prepared in the following method in <Preparation of electrolyte>, the rest was the same as Example 1-1

[0119] <Preparation of electrolyte>

[0120] In an argon atmosphere glove box with water content less than 10 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain a base organic solvent, then lithium salt lithium hexafluorophosphate was added into the base organic solvent, dissolved and mixed uniformly. Then compound of formula I-1 was added to obtain a non-aqueous electrolyte. Among them, the mass percentage of lithium salt was 12.5%, the mass percentage of compound of formula I was 1%, the mass percentage of EC was 5%, and the mass percentage of DEC was 81.5% based on the mass of the non-aqueous electrolyte, the rest was the same as Example 1-1.

[0121] Examples 3-2 to 3-7

[0122] Except that the relevant preparation parameters were adjusted according to Table 3, the rest was the same as Example 3-1.

[0123] wherein, when the mass percentage content z of the cyclic carbonate compound changes, the mass percentage content of diethyl carbonate changes accordingly, the mass percentage contents of the compound of formula I, the lithium salt, the ethylene carbonate and the propylene carbonate remain unchanged. The sum of the mass percentage contents of the cyclic carbonate compound, the compound of formula I, the lithium salt, the ethylene carbonate, the propylene carbonate and the diethyl carbonate is 100%.

[0124] Comparative Example 1 is the same as Example 1-1 except that the following steps are taken in the <Preparation of the positive electrode sheet> and <Preparation of the electrolyte>.

[0125] <Preparation of the positive electrode sheet>

[0126] The first positive electrode active material lithium manganate (LiMn2O4), the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, N-methyl pyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75 wt% is prepared. After uniform stirring in a vacuum stirrer, a positive electrode slurry is obtained. The positive electrode slurry is coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and dried at 85°C to obtain a positive electrode material layer with a thickness of 150 μm. The above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. After coating, the positive electrode sheet is cold-pressed and cut into a specification of 74 mm x 866 mm for use. The cold-pressed positive electrode material layer has a compacted density of 2.6 g / cm3. 3 .

[0127] <Preparation of the electrolyte>

[0128] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) are mixed to obtain a base organic solvent, and then lithium salt lithium hexafluorophosphate is added to the base organic solvent, dissolved and uniformly mixed to obtain a non-aqueous electrolyte. The mass percentage content of the lithium salt is 12.5%, the mass percentage content of EC is 20%, the mass percentage content of PC is 20%, and the mass percentage content of DEC is 47.5% based on the mass of the non-aqueous electrolyte.

[0129] Comparative Examples 2 to 4

[0130] Comparative Examples 2 to 4 are the same as Example 1-1 except that the relevant preparation parameters are adjusted according to Table 1.

[0131] wherein, when the mass percentage content x of the compound of formula I changes, the mass percentage content of diethyl carbonate changes accordingly, the mass percentage contents of the lithium salt, the ethylene carbonate and the propylene carbonate remain unchanged. The sum of the mass percentage contents of the compound of formula I, the lithium salt, the ethylene carbonate, the propylene carbonate and the diethyl carbonate is 100%.

[0132] Table 1

[0133]

[0134] As can be seen from Examples 1-1 to 1-18 and Comparative Examples 1 to 4, the electrochemical device of the embodiments of the present application contains an electrolyte containing the compound of Formula I and a double-layer coated positive electrode sheet, and the mass percentage content x of the compound of Formula I is controlled in the range of 0.01% to 5%; the ratio x / h1 of x to the thickness h1 of the first positive electrode material layer is controlled in the range of 0.00033 to 0.1, which can enable the electrochemical device to have a higher cycle capacity retention rate and nail penetration rate, while having a lower IMP growth rate, indicating that the electrochemical device of the embodiments of the present application has good cycle performance, storage performance and safety performance. The electrochemical device of the comparative examples does not contain an electrolyte containing the compound of Formula I and a double-layer coated positive electrode sheet, or the values of x and x / h1 are not within the range of the present application. The electrochemical device of the comparative examples has a lower cycle capacity retention rate and nail penetration rate, while having a higher IMP growth rate, indicating that the electrochemical device of the comparative examples has poor cycle performance, storage performance and safety performance.

[0135] The thickness h1 of the first positive electrode material layer generally affects the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Examples 1-1, 1-4 to 1-6, when the value of h1 is controlled within the range of the present application, the electrochemical device can have a higher cycle capacity retention rate and nail penetration rate, while having a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0136] The ratio k of the thickness of the first positive electrode material layer to the thickness of the second positive electrode material layer generally affects the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Examples 1-1, 1-7 to 1-9, when the value of k is controlled within the range of the present application, the electrochemical device can have a higher cycle capacity retention rate and nail penetration rate, while having a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0137] The type of the compound of Formula I generally affects the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Examples 1-1, 1-10 to 1-13, when the type of the compound of Formula I is controlled within the range of the present application, the electrochemical device can have a higher cycle capacity retention rate and nail penetration rate, while having a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0138] The type and content of the first positive electrode active material and the type and content of the second positive electrode active material generally affect the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Example 1-1, Example 1-14 to Example 1-18, when the type and content of the first positive electrode active material and the second positive electrode active material are regulated within the scope of the present application, the electrochemical device has a higher cycle capacity retention rate and nail penetration rate, and a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0139] Table 2

[0140]

[0141] The content f and type of the compound of formula II generally affect the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Example 1-1, Example 2-1 to Example 2-5, by regulating the content f and type of the compound of formula II within the scope of the present application, the chemical stability of the electrolyte can be improved, the electrochemical device has a higher cycle capacity retention rate and nail penetration rate, and a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0142] Table 3

[0143]

[0144] The type and mass percentage of the cyclic carbonate compound generally affect the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Example 1-1, Example 3-1 to Example 3-7, by regulating the type and mass percentage of the cyclic carbonate compound within the scope of the present application, the electrochemical device has a higher cycle capacity retention rate and nail penetration rate, and a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0145] The ratio of the thickness of the first positive electrode material layer to the mass percentage of the cyclic carbonate generally affects the cycle performance, storage performance and safety performance of the electrochemical device. As can be seen from Example 1-1, Example 3-3 to Example 3-5, by regulating the value of h1 / z within the scope of the present application, the electrochemical device has a higher cycle capacity retention rate and nail penetration rate, and a lower IMP growth rate, indicating that the electrochemical device provided by the present application has good cycle performance, storage performance and safety performance.

[0146] The above description is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, The electrolyte comprises at least one compound of formula I: ; in, R 11 and R 12 are independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkynyl, substituted or unsubstituted C1 to C 10 Alkoxy or substituted or unsubstituted C1 to C 10 Acyloxy; when substituted, the substituent is selected from a halogen atom, a C2 to C5 cycloalkyl group or a C6 to C 12 aromatic groups; The X 11 ¯Anionic group is selected from PF6¯, F¯, NO3¯, PO2F2¯, BF4¯, (FSO2)2N¯, CF3SO2O¯, 、 、 、 、 、 or Any of; Based on the mass of the electrolyte, the mass percentage of the compound of formula I is x%, 0.01≤x≤5; The positive electrode sheet includes a positive electrode current collector and a first positive electrode material layer and a second positive electrode material layer located on at least one surface of the positive electrode current collector, the first positive electrode material layer being located between the positive electrode current collector and the second positive electrode material layer, the first positive electrode material layer containing Mn and having a thickness of h1 μm, and the second positive electrode material layer having a thickness of h2 μm, wherein a ratio h1 / h2 of the thickness h1 of the first positive electrode material layer to the thickness h2 of the second positive electrode material layer is k; based on the mass of the first positive electrode material layer, the mass percentage content of the Mn element in the first positive electrode material layer is y1%, 20≤y1≤60; based on the mass of the second positive electrode material layer, the mass percentage content of the Mn element in the second positive electrode material layer is y2%, y1>y2; The x and h1 satisfy the relationship: 0.00033≤x / h1≤0.

1.

2. The electrochemical device according to claim 1, wherein The electrochemical device satisfies at least one of the following characteristics: （1）30≤h1≤200； （2）0.5≤k≤150； (3) 0.005≤x / h1≤0.

1.

3. The electrochemical device according to claim 1, wherein The compound of formula I includes at least one of the following compounds: 。 4. The electrochemical device according to claim 1, wherein The electrolyte further comprises a silane compound containing an unsaturated bond, wherein the silane compound containing an unsaturated bond is selected from at least one compound of formula II: ; Among them, R 21 、R 22 、R 23 and R 24 are independently selected from hydrogen atoms, halogen atoms, cyano groups, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkynyl or substituted or unsubstituted C1 to C 10 Any one of the heteroatom-containing functional groups, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; the R 21 、R 22 、R 23 and R 24 Any two groups in can form a ring; 21 、R 22 、R 23 and R 24 At least one of them contains an unsaturated bond; Based on the mass of the electrolyte, the mass percentage of the compound of formula II is f%, 0.01≤f≤1.

5. The electrochemical device according to claim 4, wherein The compound of formula II includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilyl)maleate, tetraallylsilane, pentamethylpentavinylcyclopentasiloxane, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetravinyldisiloxane, trivinylmethylsilane, triethylvinylsilane, allyltriethoxysilane, triethylsilylacetylene, tetravinylsilane, triacetoxyethylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane or vinyltriethoxysilane.

6. The electrochemical device according to claim 1, wherein: The first positive electrode material layer includes a first positive electrode active material, and the first positive electrode active material includes at least one of lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, lithium manganese phosphate or lithium-rich manganese-based material; The second positive electrode material layer includes a second positive electrode active material, and the second positive electrode active material includes at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium vanadate, lithium nickelate, lithium nickel cobalt manganeseate, lithium-rich manganese-based material, lithium nickel cobalt aluminum oxide or lithium titanate.

7. The electrochemical device according to claim 1, wherein The first positive electrode material layer includes a first positive electrode active material, which includes at least one of lithium manganese oxide or lithium iron manganese phosphate; the second positive electrode material layer includes a second positive electrode active material, which includes at least one of lithium iron phosphate or lithium nickel cobalt manganese oxide.

8. The electrochemical device according to claim 1 or 2, wherein: The electrolyte further includes a cyclic carbonate compound. Based on the mass of the electrolyte, the mass percentage of the cyclic carbonate compound is z%, and 5≤z≤40.

9. The electrochemical device according to claim 8, wherein 1.25≤h1 / z≤30.

10. The electrochemical device according to claim 8 or 9, wherein The cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate or butylene carbonate.

11. An electronic device comprising the electrochemical device according to any one of claims 1 to 10.

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