Lithium ion battery and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a lithium ion battery and application thereof. The lithium ion battery comprises a positive pole piece and an electrolyte, the electrolyte comprises a first additive and a second additive, the structural formula of the first additive is as shown in formula I or II, and the second additive comprises fluorophosphate; the positive pole piece comprises a positive pole current collector and a positive pole film layer located on the surface of at least one side of the positive pole current collector, the positive pole film layer comprises a lithium-nickel transition metal oxide, and based on the total mole number of transition metal in the lithium-nickel transition metal oxide, the mole percentage content t of the nickel element is larger than or equal to 50%. The lithium ion battery provided by the invention is beneficial to improving the cycle performance of the battery and improving the high-temperature storage performance. # imgabs0 #

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a lithium-ion battery and its applications. Background Art

[0002] With the development of new energy technologies, batteries are being used in more and more applications, such as in mobile phones, laptops, electric vehicles, electric cars, energy storage devices, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. This places increasingly higher demands on battery performance. Summary of the Invention

[0003] The present application provides a lithium-ion battery and its application. The battery forms a stable and low-impedance positive electrode interface film on the surface of the lithium nickel transition metal oxide positive electrode active material. The interface film can effectively inhibit the decomposition of the electrolyte, reduce the gas production of the electrolyte decomposition, and at the same time improve the high-temperature storage performance and cycle performance of the battery.

[0004] To achieve the above technical objectives, the first aspect of the present application discloses a lithium-ion battery, which includes a positive electrode plate and an electrolyte. The electrolyte includes a first additive and a second additive. The structural formula of the first additive is the following formula I or II:

[0005]

[0006] In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene,

[0007] Any one of; the above-mentioned substituted substituent is selected from halogen;

[0008] wherein R1 and R2 are independently selected from any one or more of halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the above-mentioned substituents are selected from halogen;

[0009] The second additive includes fluorophosphate;

[0010] The above-mentioned positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on the surface of at least one side of the above-mentioned positive electrode current collector. The positive electrode film layer includes lithium nickel transition metal oxide. Based on the total molar number of transition metals in the lithium nickel transition metal oxide, the molar percentage content t of the above-mentioned nickel element is greater than or equal to 50%.

[0011] In some embodiments, based on the total moles of transition metals in the lithium nickel transition metal oxide, the molar percentage content t of the nickel element is greater than or equal to 50% and less than or equal to 99%;

[0012] Preferably, the structural formula of the lithium nickel transition metal oxide is Li a Ni x Co y M z O2, M includes any one or more of Mn, Al, Ti, Mg, Zr, W and Ce, x+y+z=1, a=0.8~1.2, x=0.50~0.92, y=0.05~0.45, z=0.05~0.45.

[0013] In some embodiments, the lithium nickel transition metal oxide includes single crystal particles and / or quasi-single crystal particles, and the particle size of the single crystal particles and / or quasi-single crystal particles satisfies: 1.0<Dv99 / Dv50≤5.0;

[0014] Preferably, Dv99≤12μm, 2μm≤Dv50≤5μm;

[0015] Preferably, based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage content of the single crystal particles and / or quasi-single crystal particles is 10% to 100%.

[0016] In some embodiments, the lithium nickel transition metal oxide includes single crystal particles and polycrystalline particles, wherein the particle size of the single crystal particles satisfies: Dv99≤12 μm, 2 μm≤Dv50≤5 μm; the particle size of the polycrystalline particles satisfies: Dv99≤25 μm, 8 μm≤Dv50≤15 μm;

[0017] Preferably, based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage content of the single crystal particles is 10% to 80%.

[0018] In some embodiments, the above formula I includes any one or more of the following compounds:

[0019]

[0020]

[0021] And / or, the above formula II includes any one or more of the following compounds;

[0022]

[0023] In some embodiments, the mass ratio of the first additive to the second additive is (0.1-5): (0.1-2);

[0024] In some embodiments, the mass percentage content of the first additive in the electrolyte is 0.1% to 5%;

[0025] And / or, the mass percentage content of the above-mentioned fluorophosphate in the electrolyte is 0.1% to 2%;

[0026] Preferably, the fluorophosphate includes any one or more of lithium difluorophosphate, lithium difluorobisoxalatephosphate, and lithium tetrafluorooxalatephosphate.

[0027] In some embodiments, the compaction density of the positive electrode film is 2.9 g / cm 2 ~3.7g / cm 2 ;

[0028] And / or, the double-sided density of the positive electrode sheet is 200g / m 2 ~600g / m 2 .

[0029] And / or, based on the total mass of each component in the positive electrode film layer, the mass percentage content of the lithium nickel transition metal oxide is 95.0% to 98.0%.

[0030] In some embodiments, the positive electrode film layer includes a first positive electrode film layer disposed near a current collector and a second positive electrode film layer disposed away from the positive electrode current collector and located above the first positive electrode film layer. The molar percentage content of nickel in the first positive electrode film layer is t1, and the molar percentage content of nickel in the second positive electrode film layer is t2, satisfying: t1>t2;

[0031] Preferably, 0.70≤t1≤0.92; 0.5≤t2≤0.75.

[0032] A second aspect of the present application is to provide an electrical device, which includes the lithium-ion battery described in the first aspect.

[0033] Beneficial technical effects of this application:

[0034] The additive combination selected in this application can play a synergistic role in forming a stable and low-impedance positive electrode interface film on the surface of the ternary positive electrode material, which can effectively inhibit the decomposition of the electrolyte, reduce the gas production of the electrolyte decomposition, and improve the high-temperature storage performance of the battery. At the same time, the use of the additive combination facilitates the continuous film-forming reaction, adjusts the film-forming components, promotes the formation of a low-impedance and highly stable interface film at the positive and negative electrode interfaces, inhibits the increase of DCR during the cycle process, and improves the long-term cycle stability of the battery.

[0035] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to denote the same components. In the drawings:

[0037] Figure 1 This is a schematic diagram of the positive electrode structure of some embodiments of the present application;

[0038] The accompanying drawings in the specific implementation manner are as follows:

[0039] 1. Positive electrode sheet; 11. Positive electrode current collector; 12. Positive electrode film layer;

[0040] 121. First positive electrode film layer; 122. Second positive electrode film layer;

[0041] Coordinate axis y direction: the extension direction of the current collector, also refers to the length direction of the current collector;

[0042] Coordinate axis x direction: also refers to the thickness direction or stacking direction of the current collector. DETAILED DESCRIPTION

[0043] Below, embodiments of the battery device and power device of the present application are described in detail, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary length in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, in this application, the terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0046] Lithium-ion batteries have been widely used in various products due to their long cycle life, safety, and reliability. In recent years, with the significant increase in demand for batteries as an energy source, higher requirements have been placed on battery performance, such as cycle stability and storage life.

[0047] Based on the above considerations, in order to improve the cycle stability and storage life of the battery, the present application conducted relevant experimental research and obtained a lithium-ion battery, in which the first additive in the battery belongs to the fluorophosphate additive, and the second additive belongs to the fluorophosphate additive. These two additives are conveniently combined with the nickel in the lithium nickel transition metal oxide to form a positive electrode solid electrolyte interface film (CEI) with stable structure and properties. The CEI film improves the cycle stability and storage life of the battery by inhibiting the side reaction between the positive electrode active material and the electrolyte.

[0048] In some embodiments, the lithium-ion battery of the present application is used in electrical devices, including electric vehicles, electric ships, electric aircraft, electric tools, communication base stations, etc.

[0049] In some embodiments, a lithium-ion battery generally includes an electrode assembly. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, with the separator being positioned between the positive and negative electrode sheets. During the charge and discharge process of a lithium-ion battery, lithium ions are inserted and removed back and forth between the positive and negative electrode sheets. The separator, positioned between the positive and negative electrode sheets, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0050] The present application discloses, in some embodiments, a lithium-ion battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a lithium nickel transition metal oxide, wherein the molar percentage content t of the nickel element is greater than or equal to 50% based on the total molar number of transition metals in the lithium nickel transition metal oxide;

[0051] The lithium-ion battery further includes an electrolyte, which includes a first additive and a second additive. The first additive has a structural formula of the following formula I or II:

[0052]

[0053] In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene,

[0054] Any one of; the above-mentioned substituted substituent is selected from halogen;

[0055] wherein R1 and R2 are independently selected from any one or more of halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the above-mentioned substituents are selected from halogen;

[0056] The second additive includes fluorophosphate.

[0057] The positive electrode film layer of the present application is one layer or two layers or more. The present application will mainly use two layers as an example to illustrate in the subsequent specific embodiments, and no special emphasis or explanation will be made in the subsequent application.

[0058] The lithium nickel transition metal oxide of the present application is a positive electrode active material, which can be purchased through commercial channels, and the purchased products have their elemental composition indicated; furthermore, the components of the positive electrode active material of the present application can also be detected by chemical analysis detection methods commonly used in this field, including but not limited to: complexation titration, precipitation weight method, redox method, difference method, plasma emission spectroscopy, atomic absorption spectroscopy, etc.

[0059] The compounds and derivatives provided herein can be named according to the IUPAC (International Union of Pure and Applied Chemistry) or CAS (Chemical Abstracts Service, Columbus, OH) nomenclature system.

[0060] "Substitution" means that the hydrogen atoms in a molecule are replaced by other different atoms or molecules. The "substitution" is selected from halogen, which includes any one or more of fluorine, chlorine, bromine and iodine.

[0061] The minimum and maximum carbon atom content of a hydrocarbon group is indicated by a prefix. For example, the prefix C1-C10 alkyl indicates any alkyl group containing from "a" to "b" carbon atoms. Thus, for example, "C1-C10 alkylene" refers to an alkylene group containing from 1 to 10 carbon atoms.

[0062] "Alkyl" refers to a saturated hydrocarbon chain having a specified number of member atoms. For example, C1-10 alkyl refers to a group having 1 to 10 member atoms. Alkyl groups can be straight or branched. Representative branched alkyl groups have one, two, or three branches. Alkyl groups may be optionally substituted with one or more substituents as defined herein. Alkyl groups include, but are not limited to, methyl, ethyl, propyl (n-propyl and isopropyl), butyl (n-butyl, isobutyl, and tert-butyl), pentyl (n-pentyl, isopentyl, and neopentyl), and hexyl, among others.

[0063] "Alkylene" is compared to "alkyl". Compared with alkyl, alkylene is a group with two connection sites formed by removing two hydrogen atoms from an alkane molecule, such as methylene. Ethylene wait.

[0064] "Alkoxy" refers to a substituent relative to an alkyl group, consisting of an alkyl group and an oxygen atom, such as methoxy, ethoxy, or propoxy.

[0065] Refers to the attachment site, used to connect to other molecules to be connected.

[0066] The first additive of the present application belongs to the fluorophosphate additive class, and the second additive belongs to the fluorophosphate additive class. Among them, the fluorophosphate additive can combine with the Ni on the surface of the ternary positive electrode, reduce the occurrence of positive electrode side reactions, stabilize the positive electrode structure, inhibit the growth of interface impedance, and improve the ternary positive electrode dynamics, thereby improving the battery's cycle performance and high-temperature storage performance. Fluorophosphate additives are reduced on the surface of positive and negative electrode materials to form solid electrolyte interfaces containing organic components such as LiF and Li3PO4, such as the negative electrode solid electrolyte interface (SEI) and the positive electrode electrolyte interface (CEI), which improves the battery's cycle performance and storage performance.

[0067] However, when only one of the additives is added alone, the resulting interface film is not stable enough, and when a single additive is added in excessive amounts, it is easy to deteriorate the performance of the battery. The present application selects the above-mentioned types of additives in combination, which can play a synergistic role in forming a stable and low-impedance positive electrode interface film on the surface of the ternary positive electrode material, which can effectively inhibit the decomposition of the electrolyte, reduce the gas production of the electrolyte decomposition, and improve the high-temperature storage performance of the battery. At the same time, the above-mentioned additives are used in combination to facilitate the continuous film-forming reaction, adjust the film-forming components, promote the formation of a low-impedance and stable interface film on the positive and negative electrode interfaces, inhibit the growth of the DC resistance DCR during the cycle, and improve the long-term cycle stability of the battery.

[0068] In some embodiments, based on the total moles of transition metals in the lithium nickel transition metal oxide, the molar percentage content t of the nickel element is greater than or equal to 50% and less than or equal to 99%;

[0069] In some embodiments, the structural formula of the lithium nickel transition metal oxide is Li a Ni x Co y M z O2, M includes any one or more of Mn, Al, Ti, Mg, Zr, W and Ce, x+y+z=1, a=0.8~1.2, x=0.50~0.92, y=0.05~0.45, z=0.05~0.45.

[0070] The lithium nickel transition metal oxide with a medium to high nickel content in this application is more urgent to improve the battery performance than the lithium nickel transition metal oxide with a low nickel content, so this application further limits the molar percentage content of the nickel element in these embodiments.

[0071] In these embodiments, the present application discloses that the molar percentage content t of nickel element is 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any one of the above two ranges.

[0072] The present application discloses x, y, z, and a in these embodiments to keep the lithium nickel transition metal oxide electrically neutral. The present application discloses that x is 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 0.91, 0.9 68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, or any one of the above ranges of any two. The molar percentage content of the nickel element is t=x*100%.

[0073] The present application discloses in these embodiments that y is any one of 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, and 0.45, or any one of the values ​​satisfying any two ranges.

[0074] The present application discloses in these embodiments that z is any one of 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, and 0.45, or any one of the values ​​satisfying any two ranges.

[0075] The present application discloses in these embodiments that a is any one of 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.1, 1.2 or any one of the values ​​satisfying any two of the above ranges.

[0076] In some embodiments, the lithium nickel transition metal oxide includes single crystal particles and / or single crystal-like particles, and the particle size of the single crystal particles and / or single crystal-like particles satisfies: 1.0<Dv99 / Dv50≤5.0.

[0077] The term "single crystal particle" as used herein refers to a single particle or primary particle having a complete crystalline shape (complete crystal edges and crystal faces), wherein the crystal lattice inside the particle is arranged periodically. The term "quasi-single crystal particle" as used herein refers to an irregularly shaped particle formed by aggregating a small number of large-sized single crystal particles. The shape of the single crystal particles or quasi-single crystal particles used herein may be spherical, quasi-spherical, polygonal, or flake-like.

[0078] In this application, Dv99 refers to the particle size corresponding to the 99th percentile volume cumulative distribution of the lithium nickel transition metal oxide, starting from the smallest particle size. Dv50 refers to the particle size corresponding to the 50th percentile volume cumulative distribution of the lithium nickel transition metal oxide, starting from the smallest particle size. Dv50 is generally used to represent the average particle size of particles. In this application, 1.0 < Dv99 / Dv50 ≤ 5.0 is selected to adapt lithium nickel transition metal oxides of a certain particle size to electrolytes containing certain additives.

[0079] The present application discloses in these embodiments that Dv99 / Dv50 is any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 or any one of the values ​​satisfying any two of the above ranges.

[0080] In some embodiments, the particle size of the single crystal particles and / or quasi-single crystal particles satisfies: Dv99≤12 μm, 2 μm≤Dv50≤5 μm.

[0081] The present application discloses specific particle sizes of single crystal particles and / or quasi-single crystal particles in these embodiments. In these embodiments, Dv99≤12 μm, such as 11.6 μm, 10.5 μm, etc. Dv50 is any one of 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, and 5.0μm, or any one of the values ​​satisfying any two of the above ranges.

[0082] In some embodiments, based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage of the single crystal particles and / or quasi-single crystal particles is 10% to 100%.

[0083] The present application discloses in these embodiments that the mass percentage content of the above-mentioned single crystal particles and / or quasi-single crystal particles is 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%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109%, 110%, 111%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119%, %, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any of the values ​​satisfying any two of the above ranges.

[0084] In some embodiments, the lithium nickel transition metal oxide includes single crystal particles and polycrystalline particles, wherein the particle size of the single crystal particles satisfies: Dv99≤12 μm, 2 μm≤Dv50≤5 μm; and the particle size of the polycrystalline particles satisfies: Dv99≤25 μm, 8 μm≤Dv50≤15 μm.

[0085] The polycrystalline particles of this application refer to a single particle containing multiple grains. The lattice of each grain is periodically arranged, but the orientation of these grains is random. Such grains will produce some diffraction points due to the internal periodic structure. The diffraction points appear on a circle with a radius equal to the interplanar spacing 1 / d. Different crystal planes have different circle radii, resulting in multiple rings. The single crystal particles of this application can be distinguished from polycrystalline particles with the help of a scanning electron microscope and a diffractometer.

[0086] The present application further discloses the particle size distribution of single crystal particles and polycrystalline particles in these embodiments. In these embodiments, Dv99 of single crystal particles is ≤12μm, such as 11.6μm, 10.5μm, etc.; Dv50 of single crystal particles is 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0 Any one of μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5.0μm or any one of the values ​​satisfying any two of the above ranges.

[0087] At the same time, the particle size Dv99 of the polycrystalline particles is ≤25μm, such as 24.8μm, 20.1μm, etc.; the Dv50 of the polycrystalline particles is 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10.0μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm or any one of the values ​​in any two of the above ranges.

[0088] The present application further discloses in these embodiments that based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage content of the single crystal particles is 10% to 80%, specifically 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% , 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any of the values ​​that meet any two of the above ranges.

[0089] In some embodiments, the above formula I includes any one or more of the compounds shown in Table 1 below;

[0090] Table 1 Structures of some compounds of formula I

[0091]

[0092]

[0093] In some embodiments, the above formula I includes any one or more of the compounds shown in Table 2 below;

[0094] Table 2 Structure list of some compounds of formula II

[0095]

[0096] In Table 2, “-” indicates etc., which are not all listed.

[0097] The sources of the first additive in the present application include but are not limited to preparation and commercial sale. The present application cites the preparation methods of some specific compounds as examples.

[0098] 1. The preparation process of I-9 (2-fluoro-1,3,2-dioxaphosphorinane 2-oxide) is as follows:

[0099] S01: Add 76.7 g of phosphorus oxychloride and 100 ml of dichloromethane to a 500 mL three-necked flask, stir and dilute, cool to 15°C, add 37.9 g of 1,3-propylene glycol dropwise, add the entire amount of 1,3-propylene glycol after 60 min, raise the temperature to 25°C, and continue the reaction for 90 min to obtain a reaction solution containing 2-chloro-1,3,2-dioxaphosphorinane 2-oxide. Transfer the reaction solution to a 500 mL single-necked flask, concentrate under reduced pressure at 30°C and a vacuum of 3 kPa, remove the solvent dichloromethane, and obtain 74.3 g of 2-chloro-1,3,2-dioxaphosphorinane 2-oxide.

[0100] S02: The 2-chloro-1,3,2-dioxaphosphorinane 2-oxide obtained in step S01 was added to a 500 mL three-necked flask, and 300 mL of dimethyl carbonate was added with stirring and diluted. The temperature was controlled to 40° C. and 38.4 g of potassium fluoride was added in batches. After the addition of the raw materials, the reaction was carried out at 40° C. for 3 hours. Quantitative detection by GCMS (gas chromatography-mass spectrometry) showed that the residual amount of 2-chloro-1,3,2-dioxaphosphorinane 2-oxide was less than 10 ppm. The fluorination reaction solution was filtered through a Buchner funnel to remove solid salts, and the filtrate was removed from dimethyl carbonate at 40° C. and a vacuum of 1 kPa to obtain a crude product of 2-fluoro-1,3,2-dioxaphosphorinane 2-oxide, which was distilled under a high vacuum of 0.2 kPa to obtain 69.6 g of 2-fluoro-1,3,2-dioxaphosphorinane 2-oxide product with a purity of 99.75%.

[0101] 2. The preparation process of I-20 (3,9-difluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide) is as follows:

[0102] S01: Add 76.7 g of phosphorus oxychloride and 100 ml of trimethyl phosphate to a 500 mL three-necked flask, stir and dilute, cool to 15 ° C, vacuum control 50 kPa, add 33.9 g of pentaerythritol dropwise, add pentaerythritol after 60 minutes, heat to 25 ° C, and continue to react for 90 minutes to obtain a reaction solution containing 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide. Transfer the reaction solution to a 500 mL single-necked flask, concentrate under reduced pressure at 50 ° C and vacuum 1 kPa to remove the solvent trimethyl phosphate to obtain 74.3 g of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide;

[0103] S02: 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide obtained in step S01 was added to a 500 mL three-necked flask, and 300 mL of dimethyl carbonate was added and stirred for dilution. The temperature was controlled to 40° C. and 34.8 g of potassium fluoride was added in batches. After the addition of the raw materials, the mixture was reacted at 40° C. for 4 h. Quantitative detection by LC-MS (liquid chromatography-mass spectrometry) showed that 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9 -The residual amount of dioxide is less than 10ppm; the fluorination reaction liquid is filtered through a Buchner funnel to remove solid salts, and the filtrate is removed from dimethyl carbonate at 40°C and a vacuum of 1kPa to obtain a crude 3,9-difluoro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide product, which is distilled under a high vacuum of 0.1Pa to obtain 53.6g of 3,9-difluoro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide product with a purity of 99.56%.

[0104] 3. The preparation process of II-9 (3,3,3,9,9,9-hexafluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane) is as follows:

[0105] S01: Add 40.8g of pentaerythritol and 300mL of anhydrous dichloromethane to a 500mL three-necked flask. After nitrogen displacement, dissolve 90.6g of phosphorus trichloride in 80mL of dichloromethane and add dropwise at 15°C. After complete addition, heat and reflux at 40°C for 6 hours until gas production ceases. Cool the reaction mixture to room temperature, remove the dichloromethane using a rotary evaporator, and then distill under reduced pressure to yield 52.5g of the intermediate 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0106] S02: To a 500 mL three-necked flask, add 25 g of the intermediate 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane and 25 mL of anhydrous dichloromethane. Bubble chlorine at 10-0°C. Monitor the reaction progress with GC. Complete conversion is achieved in approximately 2 hours. Remove the dichloromethane by rotary evaporation to obtain 26.9 g of the intermediate 3,3,3,9,9,9-hexachloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0107] S03: Add 17.2 g of potassium fluoride and 100 mL of anhydrous acetonitrile to a 500 mL three-necked reaction flask. After nitrogen purge, add dropwise a mixture of 20 g of the intermediate 3,3,3,9,9,9-hexachloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane and 20 mL of anhydrous acetonitrile at 30°C. After addition, react at 80°C for 12 h. Monitor the reaction progress by GC until complete conversion of the starting material. Filter the reaction solution, and the filtrate is evaporated under reduced pressure to remove the acetonitrile. The residue is then distilled under reduced pressure to yield 12.11 g of the product 3,3,3,9,9,9-hexafluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0108] 4. The preparation process of II-10 (2,2,2-trifluoro-1,3,2-dioxaphosphorinane) is as follows:

[0109] S01: Add 15.2g of 1,3-propylene glycol and 60mL of anhydrous dichloromethane to a 500mL three-necked flask. After nitrogen displacement, dissolve 30.21g of phosphorus trichloride in 40mL of dichloromethane and add dropwise at 15°C. After complete addition, heat and reflux at 40°C for 6 hours until gas production ceases. Cool the reaction mixture to room temperature, remove the dichloromethane using a rotary evaporator, and then distill under reduced pressure to yield 22.5g of the 2-chloro-1,3,2-dioxaphosphorinane intermediate.

[0110] S02: Add 22.5 g of the 2-chloro-1,3,2-dioxaphosphorinane intermediate and 25 mL of anhydrous dichloromethane to a 500 mL three-necked flask. Bubble chlorine gas at 10-0°C. Monitor the reaction progress with GC. Complete conversion is achieved in approximately 2 hours. Remove the dichloromethane by rotary evaporation to obtain 33.8 g of the 2,2,2-chloro-1,3,2-dioxaphosphorinane intermediate.

[0111] S03: Add 33.3 g of potassium fluoride and 100 mL of anhydrous acetonitrile to a 500 mL three-necked reaction flask. After nitrogen purge, a mixture of 33.8 g of the 2,2,2-chloro-1,3,2-dioxaphosphorinane intermediate and 20 mL of anhydrous acetonitrile was added dropwise at 30°C. After addition, the mixture was allowed to react at 80°C for 12 h. The reaction progress was monitored by GC until complete conversion of the starting material. The reaction solution was filtered, and the filtrate was evaporated under reduced pressure to remove the acetonitrile. The residue was then distilled under reduced pressure to yield 22.0 g of the 2,2,2-trifluoro-1,3,2-dioxaphosphorinane product.

[0112] In some embodiments, the mass ratio of the first additive to the second additive is (0.1-5): (0.1-2).

[0113] In these embodiments, the present application controls the first additive and the second additive to have a certain quality, so as to better exert the technical effect of the two synergistically enhancing the stability of the solid electrolyte interface film.

[0114] The present application discloses in these embodiments that the mass ratio of the first additive to the second additive is 0.1:0.1, 0.1:0.2, 0.1:0.3, 0.1:0.4, 0.1:0.5, 0.1:0.6, 0.1:0.7, 0.1:0.8, 0.1:0.9, 0.1:1.0, 0.1:1.1, 0.1:1.2, 0.1:1.3, 0.1:1.4, 0.1:1.6, 0.1:1.7, 0.1:1.8, 0.1:1.9, 0.1:1.10, 0.1:1.11, 0.1:1.12, 0.1:1.13, 0.1:1. Any one of 1:1.4, 0.1:1.5, 0.1:1.6, 0.1:1.7, 0.1:1.8, 0.1:1.9, 0.1:2.0, 0.5:0.1, 1:0.1, 2:0.1, 3:0.1, 4:0.1, 5:0.1, 2.1:2, 2.5:2, 3:2, 4:2, 5:2 or any one of the values ​​satisfying any two of the above ranges.

[0115] In some embodiments, the first additive has a mass percentage content in the electrolyte of 0.1% to 5.0%.

[0116] The present application discloses in these embodiments that the mass percentage content of the first additive in the electrolyte is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, Any one of 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or any one of the values ​​satisfying any two of the above ranges.

[0117] In some embodiments, the mass percentage of the fluorophosphate in the electrolyte is 0.1% to 2%.

[0118] The present application discloses in these embodiments that the mass percentage content of fluorophosphate in the electrolyte is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or any one of the values ​​satisfying any two of the above ranges.

[0119] In some embodiments, the fluorophosphate includes any one or more of lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalatophosphate (LiODFP), and lithium tetrafluorooxalatophosphate (LiOTFP).

[0120] In some embodiments, the battery of the present application uses a liquid electrolyte, that is, an electrolyte. The electrolyte comprises an electrolyte salt and an organic solvent. The type of electrolyte salt includes any conventional type in the art, such as, but not limited to, lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluorosulfonyl)imide.

[0121] According to some embodiments of the present application, the concentration of the electrolyte salt in the electrolyte is 0.1 mol / L to 4 mol / L. In these embodiments, the present application discloses that the concentration of the electrolyte salt is any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the values ​​satisfying the above ranges.

[0122] In some embodiments, the organic solvent comprises any one or more of a carboxylate compound, a carbonate compound, and an ether compound. The carboxylate compound comprises one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL); the carbonate compound comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), and fluoroethylene carbonate (FEC). The ether compound comprises at least one of tetrahydrofuran, dimethyltetrahydrofuran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, and dimethyl phthalate. The organic solvents of the present application further include one or both of nitrile solvents and sulfone solvents. Nitrile solvents include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN). Sulfone solvents include at least one of sulfolane (SF), dimethyl sulfone (MSM), ethylmethyl sulfone (EMS), and diethyl sulfone (ESE), or a combination of two.

[0123] According to some embodiments of the present application, the electrolyte further includes a film-forming stabilizer, which includes a positive electrode film-forming stabilizer and a negative electrode film-forming stabilizer, wherein the positive electrode film-forming stabilizer includes carbonate additives and / or sulfate additives or borate additives or phosphate additives, and the carbonate additives include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC) and dioctyl carbonate (CC). Sulfate ester additives include cyclic sulfonate additives and / or alkyl sulfate additives; further, cyclic sulfonate additives include one or more of 1,3-propane sultone (PS), propylene sultone (PES), and 3-fluoro-1,3-propane sultone (FPS); alkyl sulfate additives include one or more of vinyl sulfate (DTD), diethyl sulfate (DES), dimethyl sulfate (DMS), and methylene methanedisulfonate (MMDS); borate additives include tris(trimethylsilyl)borate (TMSB); and phosphate additives include tris(trimethylsilyl)phosphate (TMSP). The negative electrode film-forming stabilizer includes one or more boron lithium salts, phosphorus-containing lithium salts, and sulfur-containing lithium salts; the boron-containing lithium salts include one or more of lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), and lithium bis(fluorooxalatoborate) (LiDFOB); the phosphorus-containing lithium salts include one or more of lithium difluorophosphate (LiPO2F2), lithium fluorophosphate (Li2PO3F), and lithium phosphate (Li3PO4). The sulfur-containing lithium salts include one or more of lithium fluorosulfonate (LiFSO3), lithium sulfate (Li2SO4), and lithium sulfamate (LiSO3NH2).

[0124] In some embodiments, the compaction density of the positive electrode film is 2.9 g / cm 2 ~3.7g / cm 2 ;

[0125] The compaction density of this application can be used to characterize the energy density of the material. The compaction density of the positive electrode film layer = the surface density of the positive electrode film layer / the thickness of the positive electrode film layer. The thickness of the positive electrode film layer includes the distance between the two end faces of the positive electrode film layer along the thickness direction. The surface density of the positive electrode film layer = the weight of the single-sided positive electrode film layer / the area of ​​the single-sided positive electrode film layer. Among them, the weight of the single-sided positive electrode film layer can be obtained by weighing, and the area of ​​the single-sided positive electrode film layer can be obtained by the area calculation formula based on the shape of the film layer. This application mainly discusses the compaction density of the positive electrode film layer after formation and before recycling. Those skilled in the art know that the compaction density of the positive electrode film layer will decrease with the use of the battery.

[0126] The present application discloses in these examples that the compacted density of the positive electrode film layer is 2.9 g / cm 2 , 3.0g / cm2 , 3.1g / cm 2 、3.2g / cm 2 , 3.3g / cm 2 、3.4g / cm 2 、3.5g / cm 2 、3.6g / cm 2 、3.7g / cm 2 Any one of the above two ranges or any one of the above two ranges.

[0127] In some embodiments, the double-sided density of the positive electrode sheet is 200 g / m 2 ~600g / m 2 ; The present application discloses in these embodiments that the double-sided surface density of the positive electrode film layer is 200g / m 2 , 250g / m 2 , 300g / m 2 、350g / m 2 , 400g / m 2 , 450g / m 2 , 500g / m 2 , 550g / m 2 , 600g / m 2 Any one of the above two ranges or any one of the above two ranges.

[0128] In some embodiments, based on the total mass of the components in the positive electrode film layer, the mass percentage of the lithium nickel transition metal oxide is 95.0% to 98.0%.

[0129] According to some embodiments of the present application, the positive electrode film layer contains lithium nickel transition metal oxide as the positive electrode active material, and may further contain a conductive agent, a binder, etc. The conductive agent includes but is not limited to any one or more of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes but is not limited to any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The dispersant includes sodium carboxymethyl cellulose, hydrogenated nitrile rubber, etc.

[0130] The present application discloses in these embodiments that the mass percentage content of the above-mentioned lithium nickel transition metal oxide is 95.0%, 95.1%, 95.2%, 95.3%, 95.4%, 95.5%, 95.6%, 95.7%, 95.8%, 95.9%, 96.0%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, 96.6%, 96.7%, 96.8%, 96.9%, 97.0%, 97.1%, 97.2%, 97.3%, 97.4%, 97.5%, 97.6%, 97.7%, 97.8%, 97.9%, and 98.0%.

[0131] The current collector of the present application can be a metal foil or a composite current collector, wherein the metal foil can be an aluminum foil, and the composite current collector can include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector can be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0132] The method for forming the positive electrode film layer of the present application comprises mixing the above raw materials with a solvent (such as N-methylpyrrolidone) in a certain mass ratio to form a positive electrode slurry, uniformly coating the positive electrode slurry on both sides of the current collector; controlling a certain single-sided coating weight; and after drying, using a cold press to compact to a certain compaction density (2.9g / cm 3 ~3.7g / cm 3 ), that is, a positive electrode sheet including a positive electrode film layer is obtained.

[0133] In some embodiments, the above-mentioned positive electrode film layer includes a first positive electrode film layer arranged close to the current collector and a second positive electrode film layer arranged away from the above-mentioned positive electrode current collector. The molar percentage content of the nickel element in the above-mentioned first positive electrode film layer is t1, and the molar percentage content of the nickel element in the above-mentioned second positive electrode film layer is t2, satisfying: t1>t2.

[0134] In some embodiments, 0.70≤t1≤0.92; 0.5≤t2≤0.75. The present application discloses in these embodiments that the molar percentage content t1 of the nickel element in the first positive electrode film layer is any one of 0.70, 0.75, 0.80, 0.85, 0.90, 0.91, and 0.92, or any one of the above two ranges; and the molar percentage content t2 of the nickel element in the second positive electrode film layer is any one of 0.50, 0.55, 0.60, 0.65, 0.70, and 0.75, or any one of the above two ranges.

[0135] like Figure 1 Schematic diagram, this application illustrates two sub-positive electrode film layers of the positive electrode film layer. This application adopts this design method, which is beneficial to reduce the side reaction between the electrolyte and the lithium nickel transition metal oxide by placing a low content of lithium nickel transition metal oxide at a position away from the positive electrode current collector. This is because the position away from the positive electrode current collector has more sufficient wettability with the electrolyte than the position close to the positive electrode current collector, and the probability of side reactions is higher.

[0136] This application also discloses, in some embodiments, a lithium-ion battery including a negative electrode sheet. The negative electrode sheet includes a current collector and a negative electrode film layer located on one or both surfaces of the current collector. Generally, the negative electrode film layer is located on both surfaces of the current collector and may be formed by coating or deposition. This application will subsequently use both sides as an example.

[0137] The present application discloses in some embodiments that the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes one or more of a carbonaceous material, a silicon-based material, a tin-based material, and an alloy thereof. The carbonaceous material in the present application includes one or a combination of two or more of artificial graphite, natural graphite, soft carbon, and hard carbon. Among them, artificial graphite, natural graphite, soft carbon, hard carbon, etc. include materials of any form conventional in the art, and include any conventional manufacturer and model in the art. The silicon-based material in the present application includes one or two of nano-silicon, silicon alloy, silicon-oxygen material, or silicon-carbon material. The tin-based and alloy materials in the present application include but are not limited to Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, etc. And the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for lithium-ion batteries or sodium-ion batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0138] The present application discloses in some embodiments that the conductive agent comprises one or more of a point-shaped conductive agent, a linear conductive agent, and a planar conductive agent, wherein the point-shaped conductive agent comprises one or more of conductive carbon black (Super P or Super S), acetylene black, conductive graphite (KS-6 or KS-15 or SFG-6 or SFG-15), and Ketjen black, the linear conductive agent comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers, and the planar conductive agent comprises but is not limited to graphene.

[0139] In some embodiments, the present application discloses that the negative electrode film layer includes a binder and a dispersant, etc. The binder includes but is not limited to polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, styrene-butadiene rubber (SBR), etc. The dispersant also includes any conventional type in the art, such as cellulose and its salts, specifically including but not limited to methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc.

[0140] The method for forming the negative electrode film layer of the present application comprises mixing the above raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry, defoaming the negative electrode slurry, and evenly coating the negative electrode slurry on both sides of the negative electrode current collector; controlling the coating weight on one side; drying, and compacting the negative electrode slurry to a certain compaction density (greater than or equal to 1.60g / cm 3 ), that is, a negative electrode sheet including a negative electrode film layer is obtained.

[0141] The present application discloses in these embodiments that the double-sided density of the negative electrode sheet is 180 g / m 2 ~250g / m 2 .

[0142] Some embodiments of the present application disclose a lithium-ion battery including an isolation member. The present application does not particularly limit the type of isolation member, and any known porous structure isolation member with good chemical stability and mechanical stability can be selected.

[0143] In some embodiments, the spacer includes a base film layer.

[0144] In some embodiments, the isolation member includes a base film layer and an organic coating layer, wherein the organic coating layer is located on at least one side surface of the base film layer.

[0145] In some embodiments, this application discloses an organic coating disposed on both sides of a base film layer, with the organic coating facing the positive and negative active material layers of a lithium-ion battery. The organic coating has a saturated electrolyte absorption rate greater than that of the base film layer. This design facilitates sufficient and effective electrolyte infiltration into the active material layers.

[0146] In some embodiments, this application discloses an organic coating disposed on one surface of a base film layer and an inorganic coating disposed on the other surface, wherein the organic coating faces the negative electrode active material layer of a lithium-ion battery, and the inorganic coating faces the positive electrode active material layer. The organic coating of this application facilitates sufficient and effective electrolyte infiltration of the negative electrode active material layer, while the inorganic coating of this application provides insulation, reducing the probability of puncturing the separator and causing a short circuit.

[0147] As described above, the materials of the base film layer and the organic coating of the present application are independently selected from any one or more of polyethylene (PE), polypropylene (PP), poly(p-phenylene terephthalamide) (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI) and polyamide (PA).

[0148] The inorganic coating of the present application includes a ceramic coating, and the ceramic particles in the ceramic coating include one or more of SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2 and BaSO4.

[0149] The battery of the present application will be described in detail below with reference to specific embodiments.

[0150] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0151] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0152] The present application can adopt conventional techniques of inorganic chemistry within the art. In the following examples, efforts have been made to ensure the accuracy of the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. The temperatures used in the following examples (in degrees Celsius) are expressed in ° C, and the pressures are atmospheric pressure or near atmospheric pressure. All pharmaceutical reagents were purchased as AR grade, and all reactions were carried out under argon protection. Unless otherwise noted, all reagents were obtained from commercial sources.

[0153] Experimental materials:

[0154] The materials of the positive electrode active material, the negative electrode active material, the electrolyte components and various auxiliary materials and components are all commercially available.

[0155] Example 1

[0156] A method for preparing a lithium-ion battery is provided, comprising the following preparation process:

[0157] Preparation of positive electrode sheet:

[0158] Take lithium nickel transition metal oxide LiNi 0.6 Co 0.1 Mn 0.3O2 (NCM613) (all single crystal particles, Dv50 of the single crystal particles is 3.5 μm, Dv99 is 10.5 μm, Dv99 / Dv50=3.0), conductive carbon black Super P, conductive carbon nanotubes, and binder PVDF are mixed in a ratio of 96.5:1.5:0.5:1.5, and N-methylpyrrolidone solvent is added and stirred to form a positive electrode slurry. The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil, and the double-sided coating surface density is 320 g / m 2 ; Then roll compaction, compaction density is 3.4g / cm 3 ; Then it is divided into strips and slices. Finally, the positive electrode of the lithium-ion battery is obtained;

[0159] Preparation of negative electrode sheet:

[0160] Artificial graphite, conductive carbon black Super P, dispersant sodium carboxymethyl cellulose and binder styrene-butadiene rubber (SBR) were dispersed in deionized water at a mass ratio of 96.0:1.0:1.2:1.8 to form a negative electrode slurry. The negative electrode slurry was evenly coated on the surface of the copper foil with a double-sided coating density of 200 g / m 2 ; Then roll compaction, compaction density is 1.6g / cm 3 Then it is divided into strips and slices to finally obtain the negative electrode of the lithium-ion battery.

[0161] Prepare the electrolyte:

[0162] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2, and lithium hexafluorophosphate (LiPF6) is added to dissolve into a 1M solution. Then, 0.5% by mass of vinylene carbonate (VC), 0.5% by mass of a first additive (I-9 in Table 1), and 0.5% by mass of a second additive, lithium difluorophosphate (LiPO2F2), are added, and the mass ratio of the first additive to the second additive is 1:1.

[0163] Isolators available:

[0164] A porous polyethylene (PE) film with a thickness of 13 μm was used as the separator.

[0165] Assembling lithium-ion batteries:

[0166] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the corresponding assembly forms a wound bare cell; the wound bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte, and after vacuum packaging, standing, formation, capacity division and other processes, a lithium-ion battery is obtained.

[0167] The following Examples 2-1 to 2-4 mainly explore the effect of the first additive content in the electrolyte on battery performance, as follows:

[0168] Example 2-1

[0169] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-1 is the same as in Example 1, except that: the electrolyte contains an additive (I-9) with a mass percentage of 1%, and the mass ratio of the first additive to the second additive is 2:1. Other aspects remain the same as in Example 1.

[0170] Example 2-2

[0171] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-2 is the same as in Example 1, except that: the electrolyte contains an additive (I-9) with a mass percentage of 2%, and the mass ratio of the first additive to the second additive is 4:1. Other aspects remain the same as in Example 1.

[0172] Example 2-3

[0173] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-3 is the same as in Example 1, except that: the electrolyte contains an additive (I-9) with a mass percentage of 0.1%, and the mass ratio of the first additive to the second additive is 1:5. Other aspects remain the same as in Example 1.

[0174] Examples 2-4

[0175] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Examples 2-4 is the same as in Example 1, except that: the electrolyte contains an additive (I-9) with a mass percentage of 5%, and the mass ratio of the first additive to the second additive is 10:1. Other aspects remain the same as in Example 1.

[0176] The following Examples 3-1 to 3-9 mainly explore the effect on battery performance by adjusting the type of the first additive, as follows:

[0177] Example 3-1

[0178] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-1 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-11 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0179] Example 3-2

[0180] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-2 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-16 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0181] Example 3-3

[0182] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-3 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-17 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0183] Examples 3-4

[0184] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-4 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-4 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0185] Examples 3-5

[0186] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-5 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-8 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0187] Examples 3-6

[0188] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-6 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-1 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0189] Examples 3-7

[0190] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-7 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-5 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0191] Examples 3-8

[0192] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-8 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-6 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0193] Examples 3-9

[0194] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-9 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-8 with a mass percentage of 0.5%, and the mass ratio of the first additive to the second additive is 1:1. Other aspects remain the same as in Example 1.

[0195] The following Examples 4-1 to 4-3 mainly explore the effects on battery performance by adjusting the type of the second additive and its content in the electrolyte, as follows:

[0196] Example 4-1

[0197] A method for preparing a lithium-ion battery is provided. The difference between Example 4-1 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive lithium difluorophosphate (LiPO2F2) with a mass percentage of 0.5% in the electrolyte is replaced with 0.1% lithium difluorobis(oxaloyl)phosphate, and the mass ratio of the first additive to the second additive is 5:1. Other aspects remain the same as in Example 1.

[0198] Example 4-2

[0199] A method for preparing a lithium-ion battery is provided. The difference between Example 4-2 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive lithium difluorophosphate (LiPO2F2) with a mass percentage of 0.5% in the electrolyte is replaced with 1.0% lithium tetrafluorooxalophosphate, and the mass ratio of the first additive to the second additive is 1:2. Other aspects remain the same as in Example 1.

[0200] Example 4-3

[0201] A method for preparing a lithium-ion battery is provided. The difference between Example 4-3 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive lithium difluorophosphate (LiPO2F2) with a mass percentage of 0.5% in the electrolyte is replaced with 2.0% lithium tetrafluorooxalophosphate, and the mass ratio of the first additive to the second additive is 1:4. Other aspects remain the same as in Example 1.

[0202] The following Examples 5-1 to 5-3 mainly explore the effects on battery performance by adjusting the type of lithium nickel transition metal oxide and the content of single crystal particles, as follows:

[0203] Example 5-1

[0204] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-1 has the same negative electrode sheet and electrolyte, but the difference is that the type of positive electrode active material is Li 1.05 Ni 0.92 Co 0.06 Mn 0.02 O2 contains 23.5% single crystal particles and the rest are polycrystalline particles, and the Dv50 of the single crystal particles is 2.7μm, Dv99 is 9.5μm, Dv99 / Dv50=3.52; the Dv50 of the polycrystalline particles is 13.9μm, Dv99 is 20.3μm, Dv99 / Dv50=1.46, and other aspects remain the same as Example 1.

[0205] Example 5-2

[0206] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-2 has the same negative electrode sheet and electrolyte, but the difference is that the type of positive electrode active material is Li 1.05 Ni 0.5 Co 0.2 Mn 0.3O2 contains 51.2% single crystal particles and the rest are polycrystalline particles, and the Dv50 of the single crystal particles is 4.7μm, Dv99 is 11.5μm, Dv99 / Dv50=2.45; the Dv50 of the polycrystalline particles is 14.9μm, Dv99 is 23.7μm, Dv99 / Dv50=1.59, and other aspects remain the same as Example 1.

[0207] Example 5-3

[0208] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-3 has the same negative electrode plate and electrolyte, but differs in that: the positive electrode active material is all polycrystalline particles, and the particle size of the polycrystalline particles satisfies: Dv50 is 15μm, Dv99 is 23μm, Dv99 / Dv50 of the polycrystalline particles is 1.53, and other aspects remain the same as Example 1.

[0209] The following Example 6-1 mainly explores the effect on battery performance by setting the positive electrode film layer close to the current collector and the area away from the current collector to have different nickel contents, as follows:

[0210] Example 6-1

[0211] A method for preparing a lithium-ion battery is provided. Example 6-1 differs from Example 1 in that the preparation method is as follows:

[0212] (2) Prepare the first positive electrode slurry: Lithium nickel transition metal oxide (Li 1.05 Ni 0.92 Co 0.06 Mn 0.02 O2): contains 23.5% single crystal particles, the single crystal particles have a Dv50 of 2.7 μm and a Dv99 of 9.5 μm, and the polycrystalline particles have a Dv50 of 13.9 μm and a Dv99 of 20.3 μm; lithium nickel transition metal oxide is mixed with conductive carbon black Super P, conductive carbon nanotubes, and binder PVDF in a ratio of 96.5:1.5:0.5:1.5 to form a first positive electrode slurry;

[0213] (3) Prepare the second positive electrode slurry: Take lithium nickel transition metal oxide LiNi 0.6 Co 0.1 Mn 0.3 O2 (NCM613) (all single crystal particles, Dv50 of the single crystal particles is 3.5 μm, Dv99 is 10.5 μm, Dv99 / Dv50 = 3.0), conductive carbon black SuperP, conductive carbon nanotubes, and binder PVDF are mixed together in a ratio of 96.5:1.5:0.5:1.5, and N-methylpyrrolidone solvent is added and stirred to form a second positive electrode slurry;

[0214] (4) Preparation of positive electrode sheet: The first positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil to obtain a first positive electrode film layer, and the second positive electrode slurry is coated on both surfaces of the first positive electrode film layer to obtain a second positive electrode film layer, wherein the compaction density of the entire positive electrode sheet is 3.4 g / cm 3 .

[0215] Other aspects remain the same as in Example 1.

[0216] Comparative Example 1

[0217] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 1 is the same as in Example 1, except that the first additive is not added to the electrolyte, and other aspects remain the same as in Example 1.

[0218] Comparative Example 2

[0219] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 1 is the same as in Example 1, except that no second additive is added to the electrolyte, and other aspects remain the same as in Example 1.

[0220] Comparative Example 3

[0221] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 1 is the same as in Example 1, except that the first additive and the second additive are not added to the electrolyte, and other aspects remain the same as in Example 1.

[0222] Comparative Example 4-1

[0223] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Comparative Example 1 has the same electrolyte, except that the positive electrode film layer contains lithium iron phosphate (LiFePO4) and does not contain lithium nickel transition metal oxide, and other aspects remain the same as Example 1.

[0224] Comparative Example 4-2

[0225] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Comparative Example 1 differs in that: the positive electrode film layer contains lithium iron phosphate (LiFePO4) and does not contain lithium nickel transition metal oxide, and the electrolyte does not contain the first additive and the second additive, and other aspects remain the same as Example 1.

[0226] Comparative Example 5-1

[0227] A method for preparing a lithium ion battery is provided. Compared with Example 1, the electrolyte of Comparative Example 1 is the same, but the difference is that the positive electrode film layer contains lithium nickel transition metal oxide, and the lithium nickel transition metal oxide is Li 1.05 Ni 1 / 3 Co 1 / 3Mn 1 / 3 O2, and other aspects remain the same as in Example 1.

[0228] Comparative Example 5-2

[0229] A method for preparing a lithium ion battery is provided. Compared with Example 1, the electrolyte of Comparative Example 1 is the same, but the difference is that the positive electrode film layer contains lithium nickel transition metal oxide, and the lithium nickel transition metal oxide is Li 1.05 Ni 1 / 3 Co 1 / 3Mn 1 / 3 O2, and the electrolyte does not contain the first additive and the second additive, and other aspects remain the same as in Example 1.

[0230] The batteries prepared in the above examples and comparative examples of this application were tested as follows:

[0231] (1) High temperature storage test: After the divided batteries are placed in a 25°C environment and left to stand for 1 hour, the capacity is calibrated at a rate of 0.33C, and the discharge capacity C1 is recorded. Charge at 0.33C to 4.45V and cut off at 0.05C. Then place the fully charged batteries in a 60°C oven for 28 days. After 28 days, perform a 0.33C discharge test on the batteries, discharge them to 2.8V, and obtain the discharge capacity C2. Then perform a 0.33C charge and discharge test for two weeks, and take the discharge capacity C3 of the last week. The capacity retention rate is: C2 / C1×%; the capacity recovery rate is: C3 / C1×%.

[0232] (2) 25°C cycle test: The battery was charged at a constant temperature of 25°C with a constant current and constant voltage of 1C to 4.45V, with a cut-off current of 0.05C, and then discharged at 1C to 2.8V. The capacity retention rate after 1000 cycles was recorded: Capacity retention rate of the battery after 1000 cycles at 25°C (%) = discharge capacity after 1000 cycles / discharge capacity at the first cycle × 100%.

[0233] (3) 45°C cycle test: The battery was charged at a constant temperature of 45°C with a constant current and constant voltage of 1C to 4.45V, with a cut-off current of 0.05C, and then discharged at 1C to 2.8V. The capacity retention rate after 800 cycles was recorded: Capacity retention rate of the battery after 800 cycles at 45°C (%) = discharge capacity after 800 cycles / discharge capacity at the first cycle × 100%.

[0234] (4) DCR growth rate test: Charge the fresh battery before cycling to 50% SOC, let it rest for 1 hour, record the voltage V1 after rest, discharge it at 2C for 30 seconds, record the termination voltage V2, and calculate the DCR of the battery: DCR1 = (V1-V2) / I 2C ; Charge the cycled battery to 50% SOC, let it rest for 1 hour, record the voltage V3 after rest, discharge it at 2C for 30 seconds, record the termination voltage V4, and calculate the DCR of the battery, DCR2 = (V3-V4) / I 2C， Cyclic DCR growth rate = (DCR2 - DCR1) / DCR1 x 100%, wherein the test temperatures include 25°C and 45°C.

[0235] The specific test results are shown in Table 3 below:

[0236] Table 3 Performance test list

[0237]

[0238]

[0239] In combination with Examples 1, 2-1, and 2-4 of the present application, it can be seen that, without changing the type of additive, by adjusting the content of the first additive so that the first additive and the second additive have a certain mass ratio, for example, when the mass ratio shown in Example 1 is 1:1, the mass ratio shown in Example 2-1 is 2:1, and the mass ratio shown in Example 2-2 is 4:1, the high-temperature storage performance and cycle performance of the batteries prepared in each case are higher than those of Examples 2-3 and 2-4. When the amount of the first additive added is too small, an effective protective film cannot be formed at the interface, and the effect on high-temperature cycling and high-temperature storage is weak; when the amount of the first additive added is too large, it will have a negative effect on high-temperature storage and cycling performance, worsening performance.

[0240] In combination with Example 1 and Examples 4-1 to 4-3 of the present application, it can be seen that when the type and content of the second additive are changed, it has a significant impact on the high-temperature storage performance and cycle performance of the battery.

[0241] In combination with Example 1, Example 3-1 to Example 3-9, and Example 4-1 to Example 4-3 of the present application, it can be seen that adjusting the type of the first additive or the second additive in the electrolyte has an impact on the high-temperature storage performance and cycle performance of the battery, and the impact on the cycle performance is greater than the impact on the high-temperature storage performance of the battery. This may be due to the different interface impedances of the positive electrode solid electrolyte interface film (CEI) and the negative electrode solid electrolyte interface film (SEI) formed by different types of first additives and second additives, resulting in different DCR growth during the battery cycle.

[0242] In combination with Example 1, Example 5-1, Example 5-2 and Example 5-3 of the present application, it can be seen that the single crystal particle content and nickel content in the lithium nickel transition metal oxide have an impact on the high-temperature storage performance and cycle performance of the obtained battery. Generally speaking, within a certain range, the higher the single crystal particle content and the lower the nickel content, the better the battery's cycle performance at room temperature and the better the high-temperature storage performance. Specifically, the nickel content of Example 5-2 is lower than that of Example 1, and the proportion of single crystal particles is lower than that of Example 1, which makes the high-temperature storage performance of Example 5-2 higher than that of Example 1, but the storage performance of Example 5-2 is lower than that of Example 1.

[0243] In combination with Example 1, Example 5-1 and Example 6-1 of the present application, it can be seen that in Example 6-1 of the present application, the molar content of nickel in the first film layer of the positive electrode film layer close to the current collector area is further set to be relatively higher than the molar content of nickel in the second film layer away from the current collector area, which is beneficial to significantly improve the room temperature cycle performance of the battery, and to a certain extent can also improve the high temperature storage performance.

[0244] In combination with Example 1 of the present application, Comparative Examples 1 to 3, it can be seen that the first additive and the second additive are important for improving the performance of the battery of the present application, and both are indispensable.

[0245] In combination with Example 1 of the present application, Comparative Examples 1 to 3, Comparative Examples 4-1 to 4-2, and Comparative Examples 5-1 to 5-2, it can be seen that the first additive and the second additive have a greater impact on lithium nickel transition metal oxide than on other positive electrode active materials, such as lithium iron phosphate, and the higher the molar content of nickel element in the lithium nickel transition metal oxide within a certain range, the higher the demand for the first additive and the second additive will be.

[0246] In summary, the design approach provided in this application is conducive to improving the high-temperature storage performance and cycle performance of lithium nickel transition metal oxide batteries.

[0247] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A lithium-ion battery, characterized in that: The invention comprises a positive electrode plate and an electrolyte, wherein the electrolyte comprises a first additive and a second additive, and the structural formula of the first additive is the following formula I or II: In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene, Any one of; the substituted substituent is selected from halogen; wherein R1 and R2 are independently selected from any one or more of halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the substituted substituent is selected from halogen; The second additive includes a fluorophosphate; The positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. The positive electrode film layer includes lithium nickel transition metal oxide. Based on the total molar number of transition metals in the lithium nickel transition metal oxide, the molar percentage content t of the nickel element is greater than or equal to 50%.

2. The lithium-ion battery according to claim 1, wherein: Based on the total moles of transition metals in the lithium nickel transition metal oxide, the molar percentage content t of the nickel element is greater than or equal to 50% and less than or equal to 99%; Preferably, the structural formula of the lithium nickel transition metal oxide is Li a Ni x Co y M z O2, M includes any one or more of Mn, Al, Ti, Mg, Zr, W and Ce, x+y+z=1, a=0.8~1.2, x=0.50~0.92, y=0.05~0.45, z=0.05~0.

45.

3. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The lithium nickel transition metal oxide includes single crystal particles and / or single crystal-like particles, and the particle size of the single crystal particles and / or single crystal-like particles satisfies: 1.0<Dv99 / Dv50≤5.0; Preferably, Dv99≤12μm, 2μm≤Dv50≤5μm; Preferably, based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage content of the single crystal particles and / or quasi-single crystal particles is 10% to 100%.

4. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The lithium nickel transition metal oxide includes single crystal particles and polycrystalline particles, wherein the particle size of the single crystal particles satisfies: Dv99≤12μm, 2μm≤Dv50≤5μm; the particle size of the polycrystalline particles satisfies: Dv99≤25μm, 8μm≤Dv50≤15μm; Preferably, based on the total mass of the lithium nickel transition metal oxide particles, the mass percentage content of the single crystal particles is 10% to 80%.

5. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The formula I includes any one or more of the following compounds: And / or, the formula II includes any one or more of the following compounds; 6. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The mass ratio of the first additive to the second additive is (0.1-5): (0.1-2).

7. The lithium-ion battery according to claim 6, wherein: The mass percentage content of the first additive in the electrolyte is 0.1% to 5%; And / or, the mass percentage content of the fluorophosphate in the electrolyte is 0.1% to 2%; Preferably, the fluorophosphate includes any one or more of lithium difluorophosphate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

8. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The compaction density of the positive electrode film layer is 2.9 g / cm 2 ~3.7g / cm 2 ; And / or, the double-sided density of the positive electrode sheet is 200g / m 2 ~600g / m 2 ; And / or, based on the total mass of each component in the positive electrode film layer, the mass percentage content of the lithium nickel transition metal oxide is 95.0% to 98.0%.

9. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The positive electrode film layer includes a first positive electrode film layer disposed close to the current collector and a second positive electrode film layer disposed away from the positive electrode current collector and located on the first positive electrode film layer. The molar percentage content of nickel in the first positive electrode film layer is t1, and the molar percentage content of nickel in the second positive electrode film layer is t2, satisfying: t1>t2; Preferably, 0.70≤t1≤0.92; 0.5≤t2≤0.

75.

10. An electrical device, characterized in that: A lithium ion battery comprising the lithium ion battery according to any one of claims 1 to 9.

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