Lithium ion battery, preparation method thereof and power utilization device

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery which comprises a negative plate and a positive plate. The negative plate comprises a negative current collector as well as a negative active material energy layer and a negative active material power layer which are respectively coated on the surfaces of the two sides of the negative current collector in sequence; and the positive plate comprises a positive current collector and two positive active material layers which are respectively coated on the surfaces of the two sides of the positive current collector in sequence. The fast charging performance, the energy density and the cycling stability of the lithium ion battery are improved by adjusting the particle size relation and the interplanar spacing relation of the active material of the negative plate and matching with the compaction relation of the positive plate. The invention further discloses a preparation method of the lithium ion battery and a power utilization device.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a lithium-ion battery and a preparation method thereof, and an electrical device. Background Art

[0002] The rapid development of the electric vehicle industry, coupled with the continuous innovation of smart grids, high-performance power tools, and robotics, has driven the demand for lithium-ion battery performance to new heights. Specifically, this requires batteries to achieve significant improvements in energy density and power density while maintaining cycling stability to accommodate a wider range of applications and meet high-performance requirements.

[0003] For example, a lithium-ion battery is provided in the related art, including a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The positive electrode sheet includes a positive electrode collector and a positive electrode membrane provided on at least one surface of the positive electrode collector and including a positive electrode active material. The negative electrode sheet includes a negative electrode collector and a negative electrode membrane provided on at least one surface of the negative electrode collector and including a negative electrode active material. The positive electrode active material includes a lithium-containing compound with a layered structure; and the negative electrode active material includes graphite.

[0004] During the implementation of the embodiments of the present disclosure, it was found that at least the following problems exist in the related art:

[0005] In order to improve the energy density of lithium-ion batteries in the related art, large particles and high compaction are generally used to prepare thick electrodes. This will cause the transmission path of lithium ions inside the electrode to become longer, increase the diffusion resistance, and reduce the rate performance; at the same time, during high-rate charging, if the ion diffusion rate cannot match the current input, metallic lithium deposits may form on the surface of the negative electrode, causing safety hazards. If a single-layer electrode with small particles and low compaction is used, the porosity of the electrode can be increased, which is conducive to the diffusion of lithium ions, and the rate performance and fast charging capability are improved. However, due to the reduced particle packing density, the energy density per unit volume decreases, and it is impossible to take into account the high energy output requirements. Therefore, the single-layer electrode design in the related art is limited by the dynamic performance of the electrode, and it is difficult to increase the energy density while taking into account the fast charging capability.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the invention

[0007] In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an extensive review, nor is it intended to identify key / critical elements or delineate the scope of protection of these embodiments, but rather serves as a prelude to the detailed description that follows.

[0008] Embodiments of the present disclosure provide a lithium-ion battery, a preparation method thereof, and an electrical device. By adjusting the particle size relationship of the negative electrode sheet and coordinating with the compaction relationship of the positive electrode sheet, the fast charging performance, energy density, and sequential stability of the lithium-ion battery are improved.

[0009] In some embodiments, the lithium-ion battery includes: a negative electrode sheet, including a negative electrode current collector and a negative electrode active material energy layer and a negative electrode active material power layer respectively coated on both surface sides of the negative electrode current collector in sequence, so that it has four coating layers; wherein, the relationship between the negative electrode active material energy layer and the negative electrode active material power layer satisfies the following conditions:

[0010]

[0011] wherein, D 50，power is the average particle size of the particles in the negative electrode active material power layer, D 50，energy is the average particle size of the particles in the negative electrode active material energy layer, d power is the crystal plane spacing of the negative electrode active material power layer, d energy is the crystal plane spacing of the negative electrode active material energy layer;

[0012] a positive electrode sheet, including a positive electrode current collector and two positive electrode active material layers respectively coated on both surface sides of the positive electrode current collector in sequence, so that it has four coating layers; wherein, the compaction density of the positive electrode sheet satisfies the following conditions:

[0013]

[0014] wherein, P1 is the compaction density of the positive electrode sheet, and P2 is the compaction density of the positive electrode sheet when a set thickness is removed.

[0015] In some embodiments, the average particle size range of the particles in the negative electrode active material energy layer is 6.0 μm to 18.0 μm, and the crystal plane spacing range thereof is 0.335 nm to 0.40 nm; the average particle size range of the particles in the negative electrode active material power layer is 3.0 μm to 10.0 μm, and the crystal plane spacing range thereof is 0.335 nm to 0.50 nm.

[0016] In some embodiments, the average particle size range of the particles in the positive electrode active material layer is 4 μm to 15 μm.

[0017] In some embodiments, P1 ≥ 3.2 g / cm 3 .

[0018] In some embodiments, the X-ray diffraction spectrum is fitted by a Gaussian function, and the corresponding crystal plane spacing is calculated according to the Bragg equation.

[0019] In some embodiments, the corresponding compaction density is calculated based on the areal density, the total thickness of the electrode sheet, and the thickness of the current collector.

[0020] In some embodiments, the particles of the negative active material power layer include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon carbide, silicon oxide, and pre-lithiated silicon oxide; wherein, when the particles of the negative active material power layer include silicon carbide, silicon oxide, or pre-lithiated silicon oxide, their total mass fraction does not exceed 25 wt%.

[0021] In some embodiments, among the particles of the negative active material power layer, the discharge capacity of artificial graphite is 285 mAh / g to 340 mAh / g, the discharge capacity of natural graphite is 330 mAh / g to 370 mAh / g, the discharge capacity of soft carbon is 200 mAh / g to 300 mAh / g, the discharge capacity of hard carbon is 300 mAh / g to 450 mAh / g, the discharge capacity of deposited silicon carbide is 1200 mAh / g to 2000 mAh / g, the discharge capacity of silicon oxide is 600 mAh / g to 1500 mAh / g, and the discharge capacity of pre-lithiated silicon oxide is 1500 mAh / g to 1800 mAh / g.

[0022] In some embodiments, the particles of the negative active material energy layer include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0023] In some embodiments, among the particles of the negative active material energy layer, the discharge capacity of artificial graphite is 300 mAh / g to 350 mAh / g, the discharge capacity of natural graphite is 360 mAh / g to 380 mAh / g, the discharge capacity of soft carbon is 250 mAh / g to 350 mAh / g, and the discharge capacity of hard carbon is 330 mAh / g to 495 mAh / g.

[0024] In some embodiments, the positive active material layer includes lithium nickel cobalt manganese oxide (Li1Ni x Co y Mn z M b O2), lithium cobalt oxide (LiCoO2), lithium nickel cobalt aluminate (Li1Ni x1 Co y1 Al z1 O2), and nickel cobalt manganese ternary material (LiNi x2 Co y2 Mn z2One or more of O2); wherein, 0.70 ≤ x ≤ 0.95, 0.15 ≤ y < 0.45, 0.05 ≤ z < 0.45, 0.0 ≤ b ≤ 0.25, and x + y + z + b = 1; the element M includes zirconium (Zr), tungsten (W), titanium (Ti), aluminum (Al), strontium (Sr), boron (B), and neodymium (Nd); 0.80 ≤ x1 ≤ 0.98, 0.01 ≤ y1 ≤ 0.15, 0.01 ≤ z1 ≤ 0.10, and x1 + y1 + z1 = 1; 0.33 ≤ x2 ≤ 0.90, 0.05 ≤ y2 ≤ 0.45, 0.05 ≤ z2 ≤ 0.45, and x2 + y2 + z2 = 1.

[0025] In some embodiments, the lithium-ion battery further includes: a negative electrode conductive agent including one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon black; a negative electrode binder including one or more of sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polystyrene-acrylic acid, and styrene-butadiene rubber.

[0026] In some embodiments, the lithium-ion battery further includes: an electrolyte including a lithium salt, an organic solvent, and an additive; wherein, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluoro(oxalato)borate, and lithium bis(trifluoromethylsulfonyl)imide; the organic solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and ethyl methyl carbonate; the additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, vinylene sulfate, vinylene sulfite, vinylene carbonate, and vinyl carbonate.

[0027] In some embodiments, the ratio range of the discharge capacity of the negative electrode sheet to the discharge capacity of the positive electrode sheet is from 1.02 to 1.22.

[0028] In some embodiments, the discharge characteristics of the lithium-ion battery are as follows: After the lithium-ion battery with a 100% charging rate is left standing at 25°C for 6 hours, at 25°C, it is discharged at a 0.1C rate to 2.5V, and the corresponding discharge capacity is Q1; it is discharged at a 2C rate to 2.5V, and the corresponding discharge capacity is Q2; it is discharged at a 5C rate to 2.5V, and the corresponding discharge capacity is Q3; wherein, the retention rate of the discharge capacity Q2 / Q1 ≥ 70%, and the retention rate of the discharge capacity Q3 / Q2 ≥ 45%.

[0029] In some embodiments, at 25°C, after discharging and cycling 1000 times at a 1C rate, the attenuation rate Q of the discharge capacity d ≤ 25%.

[0030] In some embodiments, the method for preparing the lithium-ion battery includes:

[0031] Prepare the positive electrode sheet: Mix the positive electrode coating material, and sequentially coat two layers of the positive electrode coating material on both surfaces of the aluminum foil. After drying and cold pressing, the positive electrode sheet is obtained;

[0032] Prepare the negative electrode sheet: Mix the negative electrode energy layer material and the negative electrode power layer material, and sequentially coat the negative electrode energy layer material and the negative electrode power layer material on both surfaces of the copper foil. After drying and cold pressing, the negative electrode sheet is obtained;

[0033] Prepare the battery core: Roll the positive electrode sheet and the negative electrode sheet after rolling and slitting respectively together with the separator to obtain the battery core;

[0034] Assemble the lithium-ion battery: Weld the tabs of the battery core to the electrical connection sheet, install it into the battery case, and perform the processes of electrolyte injection, sealing, and formation to obtain the lithium-ion battery.

[0035] In some embodiments, the electrical device includes the lithium-ion battery as described in the foregoing embodiments.

[0036] The lithium-ion battery, its preparation method, and the electrical device provided by the embodiments of the present disclosure can achieve the following technical effects:

[0037] In this application, a negative electrode active material energy layer and a negative electrode active material power layer are sequentially coated on both surfaces of the negative electrode current collector of the negative electrode sheet. At the same time, two layers of positive electrode active material layers are sequentially coated on both surfaces of the positive electrode current collector of the positive electrode sheet. The average particle size of the particles in the negative electrode active material power layer is smaller than that of the particles in the negative electrode active material energy layer, and the crystal plane spacing of the negative electrode active material power layer is larger than that of the negative electrode active material energy layer; and in combination with the gradient compaction of the positive electrode sheet, the fast charging performance, energy density, and cycle stability of the lithium-ion battery can be synergistically optimized. In addition, in the case of using a double-layer electrode sheet, by limiting the average particle size ratio, crystal plane spacing ratio, and compaction density ratio of each particle, while improving the energy density, excellent rate performance can be maintained, and the cycle stability of the battery can be significantly improved, thus showing significant advantages in the application of high-performance lithium-ion batteries.

[0038] The above general description and the following description are only exemplary and explanatory, and are not used to limit this application. Description of the Drawings

[0039] One or more embodiments are exemplarily illustrated by the corresponding drawings. These exemplary illustrations and the drawings do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements. The drawings do not constitute a proportional limitation, and among them:

[0040] Figure 1 is a schematic structural diagram of a lithium-ion battery provided by an embodiment of the present disclosure;

[0041] Figure 2 is a schematic structural view of a battery core provided by an embodiment of the present disclosure;

[0042] Figure 3 is a developed view of a battery core provided by an embodiment of the present disclosure;

[0043] Figure 4 is a flowchart of a preparation method of a lithium-ion battery provided by an embodiment of the present disclosure.

[0044] Reference numerals:

[0045] 1 - positive electrode end; 10 - battery core; 11 - positive electrode post; 12 - negative electrode end; 2 - housing; 3 - negative electrode sheet; 4 - separator; 5 - positive electrode sheet. Detailed implementation manners

[0046] In order to be able to understand the features and technical content of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are only for reference and illustration purposes and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a sufficient understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, well-known structures and devices can be shown in a simplified manner.

[0047] In the embodiments of the present disclosure, terms such as "first" and "second" in the specification and claims of the embodiments of the present disclosure and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to implement the embodiments of the present disclosure described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0048] In the embodiments of the present disclosure, the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "middle", "outer", "front", and "rear" is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the embodiments of the present disclosure and their embodiments and are not used to limit that the indicated devices, elements, or components must have a specific orientation or be constructed and operated in a specific orientation. And, in addition to being able to represent an orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0049] In addition, the terms "arranged", "connected", and "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0050] Unless otherwise specified, the term "plurality" means two or more.

[0051] In the embodiments of the present disclosure, the character " / " indicates that the objects before and after are in an "or" relationship. For example, A / B means: A or B.

[0052] The term "and / or" is a description of the associated relationship of objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B, these three relationships.

[0053] It should be noted that, without conflict, the embodiments in the embodiments of the present disclosure and the features in the embodiments can be combined with each other.

[0054] Combined Figure 1 As shown, the embodiments of the present disclosure provide a lithium-ion battery, including a cylindrical housing 2, which is used to accommodate a battery core inside, with the positive electrode end 1 at the top and the negative electrode end 12 at the bottom, and a positive electrode post 11 is arranged on the positive electrode end 1. Specifically, Figure 2 shows a schematic structural diagram of the battery core in the present application, Figure 3 shows a schematic unfolded diagram of the battery core in the present application. Among them, the positive electrode sheet 5, the negative electrode sheet 3, and the separator 4 are stacked as Figure 3 shown and then wound to form Figure 2 a cylindrical battery core 10 as shown. The end of the electrode sheet at the initial stage of winding is the end of the electrode sheet at the axis of the cylinder, and the end of the electrode sheet at the end of winding is the end of the electrode sheet on the outer surface of the cylinder. Among them, the positive electrode sheet 5 includes a strip-shaped positive electrode foil, a positive electrode coating, and a first empty foil area coated on the surface of the strip-shaped positive electrode foil. The negative electrode sheet 3 includes a strip-shaped negative electrode foil, a negative electrode coating, and a second empty foil area coated on the surface of the strip-shaped negative electrode foil. The first empty foil area and the second empty foil area are perpendicular to the winding direction and form the top end face or the bottom end face of the lithium-ion battery by methods such as flattening or cutting and laminating.

[0055] To further improve the energy density of the lithium-ion battery and simultaneously take into account the fast charging ability, the embodiments of the present disclosure provide a lithium-ion battery, including a negative electrode sheet and a positive electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material energy layer and a negative electrode active material power layer respectively coated on both sides of the negative electrode current collector in sequence, so that it has four coating layers; among them, the relationship between the negative electrode active material energy layer and the negative electrode active material power layer satisfies the following conditions:

[0056]

[0057] wherein, D 50，power is the average particle size of the particles in the power layer of the negative electrode active material, and D 50，energy is the average particle size of the particles in the energy layer of the negative electrode active material, and d power is the interplanar spacing of the crystal planes in the power layer of the negative electrode active material, and d energy is the interplanar spacing of the crystal planes in the energy layer of the negative electrode active material.

[0058] The positive electrode sheet includes a positive electrode current collector and two layers of positive electrode active material layers sequentially coated on both side surfaces of the positive electrode current collector, so that it has four coating layers; wherein, the tap density of the positive electrode sheet satisfies the following conditions:

[0059]

[0060] wherein, P1 is the tap density of the positive electrode sheet, and P2 is the tap density of the positive electrode sheet when a set thickness is removed.

[0061] Using the lithium-ion battery provided by the embodiments of the present disclosure, by sequentially coating a negative electrode active material energy layer and a negative electrode active material power layer on both side surfaces of the negative electrode current collector of the negative electrode sheet, and at the same time, sequentially coating two layers of positive electrode active material layers on both side surfaces of the positive electrode current collector of the positive electrode sheet. The average particle size of the particles in the negative electrode active material power layer is smaller than the average particle size of the particles in the negative electrode active material energy layer, and the interplanar spacing of the crystal planes in the negative electrode active material power layer is larger than the interplanar spacing of the crystal planes in the negative electrode active material energy layer; and in combination with the gradient compaction of the positive electrode sheet, the synergistic optimization of the fast charging performance, energy density and cycling stability of the lithium-ion battery can be achieved. In addition, in the case of using a double-layer electrode sheet, by limiting the average particle size ratio, interplanar spacing ratio and tap density ratio of each particle, while increasing the battery energy density ≥ 300 Wh / Kg, excellent rate performance can be maintained, continuous discharge of ≥ 70 A, instantaneous discharge of ≥ 200 A - 250 A can be achieved, and the cycle stability of the battery can be significantly improved, and the battery cycle life is greater than 3000 times, thus showing significant advantages in the application of high-performance lithium-ion batteries.

[0062] Optionally, the average particle size range of the particles in the negative electrode active material energy layer is 6.0 μm to 18.0 μm, and the range of its interplanar spacing is 0.335 nm to 0.40 nm.

[0063] Optionally, the average particle size range of the particles in the negative electrode active material power layer is 3.0 μm to 10.0 μm, and the range of its interplanar spacing is 0.335 nm to 0.50 nm.

[0064] Optionally, the average particle size range of the particles in the positive electrode active material layer is from 4 μm to 15 μm.

[0065] Optionally, P1 ≥ 3.2 g / cm 3 。

[0066] In the embodiment of the present disclosure, a precision scraper with a blade angle of 15° and a thickness error of ±2 μm is used to remove a set thickness from the positive electrode sheet. Here, after removing 50% of the thickness of the upper layer of the positive electrode sheet with the precision scraper, the lower layer compaction density is measured as P2.

[0067] Optionally, the corresponding compaction density is calculated through the surface density, the total thickness of the electrode sheet, and the thickness of the current collector. Specifically, the calculation method of the compaction density is as follows:

[0068]

[0069] where P is the compaction density, P S is the surface density, t p is the total thickness of the pressed electrode sheet, t c is the thickness of the current collector.

[0070] Optionally, the X-ray diffraction spectrum is fitted by a Gaussian function, and the corresponding interplanar spacing is calculated based on the Bragg equation. Specifically, the calculation method of the interplanar spacing is as follows:

[0071] The diffraction peak positions in the X-ray diffraction (XRD) spectrum are fitted by a Gaussian function in the range of 24° - 26°, based on the Bragg equation:

[0072]

[0073] where d is the interplanar spacing, n is the first-order diffraction, λ is the wavelength, and θ is the half-value of the diffraction angle.

[0074] Optionally, the particles in the negative electrode active material power layer include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon carbon, silicon oxide, and pre-lithiated silicon oxide; wherein, when the particles in the negative electrode active material power layer include silicon carbon, silicon oxide, or pre-lithiated silicon oxide, their total mass fraction does not exceed 25 wt%.

[0075] Among the particles of the negative electrode active material power layer, the discharge capacity of artificial graphite is 285 mAh / g to 340 mAh / g, the discharge capacity of natural graphite is 330 mAh / g to 370 mAh / g, the discharge capacity of soft carbon is 200 mAh / g to 300 mAh / g, the discharge capacity of hard carbon is 300 mAh / g to 450 mAh / g, the discharge capacity of deposited silicon carbide is 1200 mAh / g to 2000 mAh / g, the discharge capacity of silicon oxide is 600 mAh / g to 1500 mAh / g, and the discharge capacity of pre-lithiated silicon oxide is 1500 mAh / g to 1800 mAh / g.

[0076] Optionally, the particles of the negative electrode active material energy layer include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0077] Among the particles of the negative electrode active material energy layer, the discharge capacity of artificial graphite is 300 mAh / g to 350 mAh / g, the discharge capacity of natural graphite is 360 mAh / g to 380 mAh / g, the discharge capacity of soft carbon is 250 mAh / g to 350 mAh / g, and the discharge capacity of hard carbon is 330 mAh / g to 495 mAh / g.

[0078] Optionally, the positive electrode active material layer includes one or more of lithium nickel cobalt manganese oxide (Li1Ni x Co y Mn z M b O2), lithium cobalt oxide (LiCoO2), lithium nickel cobalt aluminate (Li1Ni x1 Co y1 Al z1 O2), and lithium nickel cobalt manganese ternary material (LiNi x2 Co y2 Mn z2 O2); where 0.70 ≤ x ≤ 0.95, 0.15 ≤ y < 0.45, 0.05 ≤ z < 0.45, 0.0 ≤ b ≤ 0.25, and x + y + z + b = 1; element M includes zirconium (Zr), tungsten (W), titanium (Ti), aluminum (Al), strontium (Sr), boron (B), and neodymium (Nd); 0.80 ≤ x1 ≤ 0.98, 0.01 ≤ y1 ≤ 0.15, 0.01 ≤ z1 ≤ 0.10, and x1 + y1 + z1 = 1; 0.33 ≤ x2 ≤ 0.90, 0.05 ≤ y2 ≤ 0.45, 0.05 ≤ z2 ≤ 0.45, and x2 + y2 + z2 = 1.

[0079] Optionally, the lithium-ion battery further includes: a negative electrode conductive agent including one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon black; and a negative electrode binder including one or more of sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, styrene-acrylic acid, and styrene-butadiene rubber.

[0080] Optionally, the lithium-ion battery further includes: an electrolyte including a lithium salt, an organic solvent, and an additive; wherein the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluoro(oxalato)borate, and lithium bis(trifluoromethylsulfonyl)imide; the organic solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and ethyl methyl carbonate; and the additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, vinylene sulfate, vinylene sulfite, vinylene carbonate, and vinyl carbonate.

[0081] Optionally, the ratio range of the discharge capacity N of the negative electrode sheet to the discharge capacity P of the positive electrode sheet is 1.02 to 1.22.

[0082] Here, since the cost of the positive electrode sheet is relatively high, in order to fully utilize the discharge capacity of the positive electrode sheet and reduce the generation of lithium deposition on the surface of the negative electrode sheet, the discharge capacity of the negative electrode sheet is made greater than that of the positive electrode sheet, leaving a certain redundancy. Among them, if the redundancy is too high or too low, it will affect the performance of the battery. For example, when N / P > 1.22, at this time, the positive electrode is in a deep lithium-depleted state (Li + extraction amount > 80%), but the negative electrode still has a surplus to receive Li + . In this way, the positive electrode kinetic limitation dominates over-discharge, which will lead to irreversible phase change and oxygen release of the positive electrode material, affecting the cycle performance, and at the same time will also lead to a decrease in the battery energy density. For example, when N / P < 1.02, during high-current charging, Li + cannot be embedded in time and is likely to deposit on the surface of the negative electrode to form lithium dendrites, posing a short-circuit risk.

[0083] Therefore, limiting the ratio range of the discharge capacity N of the negative electrode sheet to the discharge capacity P of the positive electrode sheet between 1.02 and 1.22 can ensure both the cycle performance and the energy density.

[0084] Optionally, the discharge characteristics of the lithium-ion battery are as follows: After a lithium-ion battery with a 100% charging rate is left standing at 25°C for 6 hours, at 25°C, it is discharged to 2.5V at a 0.1C rate, and the corresponding discharge capacity is Q1; discharged to 2.5V at a 2C rate, and the corresponding discharge capacity is Q2; discharged to 2.5V at a 5C rate, and the corresponding discharge capacity is Q3; wherein, the retention rate of the discharge capacity Q2 / Q1 ≥ 70%, and the retention rate of the discharge capacity Q3 / Q2 ≥ 45%.

[0085] Optionally, at 25 °C, after 1000 discharge cycles at a rate of 1C, the decay rate Q of the discharge capacity d ≤ 25%.

[0086] Meanwhile, in combination with Figure 4 As shown, an embodiment of the present disclosure provides a method for preparing a lithium-ion battery, including:

[0087] S401. Prepare a positive electrode sheet: Mix positive electrode coating materials, and sequentially coat two layers of positive electrode coating materials on both surfaces of an aluminum foil. After drying and cold pressing, a positive electrode sheet is obtained;

[0088] S402. Prepare a negative electrode sheet: Mix negative electrode energy layer materials and negative electrode power layer materials, and sequentially coat negative electrode energy layer materials and negative electrode power layer materials on both surfaces of a copper foil. After drying and cold pressing, a negative electrode sheet is obtained;

[0089] S403. Prepare a battery core: Roll the positive electrode sheet and the negative electrode sheet together with a separator after rolling and slitting to obtain a battery core;

[0090] S404. Assemble a lithium-ion battery: Weld the tabs of the battery core to an electrical connection sheet, place it in a battery case, and perform electrolyte injection, sealing, and formation processes to obtain a lithium-ion battery.

[0091] In addition, an embodiment of the present disclosure provides an electrical device including a lithium-ion battery for providing power as described in this application.

[0092] The following continues to further explain and illustrate the present invention with examples.

[0093] Example 1

[0094] Example 1 provides a lithium-ion battery, which is prepared by the following method:

[0095] Prepare a positive electrode sheet: Take a positive electrode active material (Li1Ni 50 with D 0.8 Co 0.1 Mn 0.1 O2), conductive carbon black, carbon nanotubes, and polyvinylidene fluoride (PVDF), and stir and mix them evenly in an N-methylpyrrolidone solvent system according to a mass ratio of 96:1:1:2 to obtain a positive electrode coating material with a solid content of 68%. Coat the positive electrode coating material on both sides of an aluminum foil with a thickness of 12.0 μm, and the coating thickness is 100 μm. Here, each side of the aluminum foil is 50 μm. After drying and cold pressing, the side close to the positive electrode current collector is compacted to 3.5 g / cm 3The positive electrode sheet; on the surface of the first compacted layer, the same slurry is continuously coated, and the thicknesses on both sides of the aluminum foil are 45 μm respectively. After drying and cold pressing, the total compaction P1 is 3.4 g / cm 3 of the overall positive electrode sheet. Among them, after removing 50% of the thickness of the upper layer of the positive electrode sheet with a precision scraper, the compaction P2 of the lower layer of the positive electrode sheet is measured again to be 3.55 g / cm 3 .

[0096] Preparing the negative electrode sheet: Calculated by mass percentage, the materials of the negative electrode power layer include 96.0% active material (graphite content 95 wt%, deposited silicon carbide content 5 wt%; among them, the D 50，power of graphite is 4.2 μm and the crystal plane spacing is 0.335 nm, and the D 50 of the deposited silicon carbide is 4.5 μm), 1.5% carbon nanotubes, 1.0% thickening agent sodium carboxymethyl cellulose, 1.0% binder polyacrylic acid, and 0.5% binder styrene-butadiene rubber; the materials of the negative electrode energy layer include 96.0% graphite (D 50，energy is 12.6 μm and the crystal plane spacing is 0.335 nm), 1.5% carbon nanotubes, 1.0% thickening agent sodium carboxymethyl cellulose, and 1.5% binder styrene-butadiene rubber. The above two negative electrode formulations are respectively added to deionized water and stirred to form negative electrode coating materials with a solid content of 40%. The negative electrode energy layer material is coated on both sides of a copper foil with a thickness of 8 μm, and the coating thickness is 40 μm. After the negative electrode sheet is dried, the negative electrode power layer material is coated on the negative electrode active material energy layers on both sides. Here, the coating thickness is 80 μm. After drying and cold pressing, a negative electrode sheet is formed, and its compaction density is 1.6 g / cm 3 .

[0097] Preparing the electrolyte: The lithium salt lithium hexafluorophosphate (LiPF6), the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), the first type of additive fluoroethylene carbonate (FEC), the second type of additive ethylene sulfate (DTD), and the third type of additive vinylene carbonate (VC) are mixed in a ratio of 10.0:20.0:55.0:2.0:8.0:5.0 by mass percentage to obtain the electrolyte.

[0098] Preparing the separator: A separator with a high porosity is selected. The thickness of the base film PE in the separator is 9 μm, and the thicknesses of the ceramic coatings on both sides of the base film are 1.0 μm and the thickness of the PVDF coating is 1.0 μm.

[0099] Assembly of lithium-ion battery: After rolling and slitting the positive electrode sheet and the negative electrode sheet respectively, they are wound together with the separator to obtain a cylindrical battery core. Subsequently, after welding the battery core with the electrical connection sheet, it is installed into the battery housing. After completing the processes of liquid injection, sealing, and formation, the lithium-ion battery of Example 1 is obtained. The housing of this lithium-ion battery is cylindrical, and its dimensional parameters are diameter: 21.0 mm, length 70.0 mm.

[0100] Example 2

[0101] Example 2 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite D 50，power is 5.3 μm, and the others are the same as those in Example 1.

[0102] Example 3

[0103] Example 3 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite D 50，power is 6.7 μm, and the others are the same as those in Example 1.

[0104] Example 4

[0105] Example 4 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite D 50，power is 8.6 μm, and the others are the same as those in Example 1.

[0106] Example 5

[0107] Example 5 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite is treated by the low-temperature bromine intercalation method for 2 h to increase the interplanar spacing d power to 0.42 nm, and the others are the same as those in Example 1.

[0108] In this example, the operation steps of the low-temperature bromine intercalation method include: sealing graphite and excessive Br2 in a glass tube, reacting at a constant temperature of 60 °C for 2 hours. Among them, Br2 diffuses and inserts into the interlayer to form C n Br intercalation compound, and then quickly transferring it to a 200 °C tubular furnace, purging with nitrogen, and performing heat treatment for 10 min. Br2 is vaporized by heat to generate pressure, so as to increase the interplanar spacing of graphite.

[0109] Example 6

[0110] Example 6 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite is treated by the low-temperature bromine intercalation method for 6 h to increase the interplanar spacing d power to 0.48 nm, and the others are the same as those in Example 1.

[0111] Example 7

[0112] Example 7 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite D 50，energy is 9.4 μm, and the others are the same as in Example 1.

[0113] Example 8

[0114] Example 8 provides a lithium-ion battery. The difference between this example and Example 1 is that the added graphite D 50，energy is 15.7 μm, and the others are the same as in Example 1.

[0115] Example 9

[0116] Example 9 provides a lithium-ion battery. The difference between this example and Example 1 is that the D of the added positive electrode Li1Ni 0.8 Co 0.1 Mn 0.1 O2 50 is 5.2 μm, and the others are the same as in Example 1.

[0117] Example 10

[0118] Example 10 provides a lithium-ion battery. The difference between this example and Example 1 is that the D of the added positive electrode Li1Ni 0.8 Co 0.1 Mn 0.1 O2 50 is 8.7 μm, and the others are the same as in Example 1.

[0119] Example 11

[0120] Example 11 provides a lithium-ion battery. The difference between this example and Example 1 is that the D of the added positive electrode Li1Ni 0.8 Co 0.1 Mn 0.1 O2 50 is 10.4 μm, and the others are the same as in Example 1.

[0121] Example 12

[0122] Example 12 provides a lithium-ion battery. The difference between this example and Example 1 is that the total compaction P1 of the positive electrode sheet is 3.2 g / cm 3 , and the compaction P2 of the lower-layer positive electrode sheet is 3.3 g / cm 3 , and the others are the same as in Example 1.

[0123] Example 13

[0124] Example 13 provides a lithium-ion battery. The difference between this example and Example 1 is that the total compaction P1 of the positive electrode sheet is 3.6 g / cm 3 , and the compaction P2 of the lower-layer positive electrode sheet is 3.65 g / cm 3 , and the others are the same as those in Example 1.

[0125] Comparative Example 1

[0126] Comparative Example 1 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the added graphite D 50，power and D 50，energy are both 12.6 μm, and the others are the same as those in Example 1.

[0127] Comparative Example 2

[0128] Comparative Example 2 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the added graphite D 50，power and D 50，energy are both 4.2 μm, and the others are the same as those in Example 1.

[0129] Comparative Example 3

[0130] Comparative Example 3 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the compaction P1 and P2 of the positive electrode sheet are both 3.4 g / cm 3 , and the others are the same as those in Example 1.

[0131] Testing equipment: First, discharge the lithium-ion battery to 2.5 V. Inside the glove box, carefully disassemble the battery and take out the negative electrode sheet of the cylindrical battery cell. Immerse the negative electrode sheet in dimethyl carbonate for 30 min, take it out and wipe the surface to remove the residual organic solvent; repeat this process three times to ensure the removal of all possible impurities and residues. Leave part of the negative electrode sheet and let it stand in the glove box for 48 h. After ensuring it is dry, take it out of the glove box for film resistance testing. Use a precision scraper to scrape off the material in the material area on the positive electrode sheet. The scraped positive electrode material is immersed in NMP and ultrasonically treated for 30 min, and the precipitate is taken after centrifugation. For the negative electrode sheet, the active materials of the negative electrode active material power layer and the negative electrode active material energy layer need to be scraped respectively, ultrasonically treated in ethanol for 30 min, and the precipitate is taken after centrifugation. Finally, let it stand in the glove box for 48 hours to ensure that the active material is completely dry. Take out the active material from the glove box and immediately perform scanning electron microscope (SEM) and X-ray diffraction (XRD) characterization.

[0132] Test 1. Determination of negative electrode sheet D 50，power , D 50，energy and positive electrode sheet D 50 , including:

[0133] Take a small amount of powder and evenly spread it on the conductive tape. Subsequently, take clear particle images of at least 5 different regions under a scanning electron microscope. Import the images using ImageJ or Nanomeasure software. After calibrating the scale, manually or automatically measure the projected diameters of more than 200 particles. Arrange the data in ascending order and plot the cumulative distribution curve. Take the particle size value corresponding to a cumulative percentage of 50% as D 50 , and at the same time, it is necessary to exclude the interference data of obvious aggregates to ensure accuracy.

[0134] Test 2, negative electrode sheet d power and d energy Determination, including:

[0135] Use a copper target X-ray diffractometer (Cu-Kα radiation, λ = 0.15 nm, tube voltage 40 kV, tube current 40 mA). Uniformly disperse the sample on a silicon substrate and obtain the XRD pattern at a scanning rate of 2° / min in the range of 2θ = 10° - 80°. Based on the diffraction peak position corresponding to the (002) crystal plane in the XRD pattern (~25° - 27°), and calculate the negative electrode sheet d power and d energy .

[0136] Test 3, testing the tap density of the positive electrode sheet, including:

[0137] Cut the positive electrode sheet that has been rinsed with dimethyl carbonate and vacuum dried into 9 square samples of standard size (2.0 cm × 2.0 cm); Erase the active material on the front and back of 3 of the square samples, rinse and dry them with N-methylpyrrolidone (NMP), weigh them and calculate the average mass M1. At the same time, use a micrometer to measure the average thickness L1 of the samples; Weigh the masses of the other 3 square samples and calculate the average mass M2. At the same time, measure the average thickness L2 of the samples; Use a precision scraper to remove the upper 50% thickness of the last 3 square electrode sheets, weigh the mass of the samples and calculate the average mass M3. At the same time, measure the average thickness L3 of the samples.

[0138] Calculate the tap density of the positive electrode sheet (unit g / cm 3 ):

[0139]

[0140] Test 4, rate performance test, including:

[0141] Place the battery in an incubator at 25°C for 4 h and conduct the test according to the following steps:

[0142] (11) Constant current and constant voltage charge to 4.2V at a rate of 0.1C, with a cut-off current of 0.01C, and let it stand for 10 minutes. The capacity measured during the constant current charge to 4.2V is denoted as Q1;

[0143] (12) Constant current discharge to cut-off at 2.5V at a rate of 0.1C, with a cut-off current of 0.01C, and let it stand for 10 minutes;

[0144] (13) Constant current and constant voltage charge to 4.2V at a rate of 2.0C, with a cut-off current of 0.01C, and let it stand for 10 minutes. The capacity measured during the constant current charge to 4.2V is denoted as Q2;

[0145] (14) Constant current discharge to cut-off at 2.5V at a rate of 0.1C, with a cut-off current of 0.01C, and let it stand for 10 minutes;

[0146] (15) Constant current and constant voltage charge to 4.2V at a rate of 5.0C, with a cut-off current of 0.01C, and let it stand for 10 minutes. The capacity measured during the constant current charge to 4.2V is denoted as Q3;

[0147] (16) Constant current discharge to cut-off at 2.5V at a rate of 0.1C, with a cut-off current of 0.01C, and let it stand for 10 minutes.

[0148] Among them, the calculation method of the 2C capacity retention rate is: Q2 / Q1×100; the calculation method of the 5C capacity retention rate is: Q3 / Q1×100.

[0149] Test 5. The calculation method of energy includes:

[0150] Place the battery in an incubator at 25°C for 4 hours and conduct tests according to the following steps:

[0151] (21) Constant current charge to 4.2V at a rate of 1.0C, and then switch to constant voltage charge until the current drops to 0.05C;

[0152] (22) Let it stand for 30 minutes after charging is completed;

[0153] (23) Constant current discharge to cut-off at 2.5V at a rate of 1.0C, and record the discharge time and voltage curve;

[0154] (24) Calculate the discharge capacity and average voltage to obtain the total energy.

[0155] The discharge capacity is C = I×t, where I is the discharge current and t is the discharge duration.

[0156] The average voltage is

[0157] The total energy is E = C×Vaverage .

[0158] Test 6. Cycle performance test, including:

[0159] Place the battery in an incubator at 25°C for 4 h and perform the test according to the following steps:

[0160] (31) Constant current charge at a rate of 0.1C until 4.2V, then switch to constant voltage charge until the current drops to 0.01C;

[0161] (32) Let it stand for 10 min after charging is completed;

[0162] (33) Perform constant current discharge and discharge to 2.5V at a rate of 0.1C;

[0163] (34) Repeat the above charging and discharging process: perform constant current charge at a rate of 1C until 4.2V, and let it stand for 10 min again.

[0164] (35) Perform constant current discharge at a rate of 1C until 2.5V.

[0165] (36) Repeat the above charging and discharging 1000 cycles in total.

[0166] Statistically analyze the capacity of the battery after the 1st and 1000th cycle, and calculate the capacity attenuation rate of the battery.

[0167] Among them, according to the tests of Examples 1 to 13 and Comparative Examples 1 to 3, the following Table 1 is obtained.

[0168]

[0169] Table 1

[0170] As shown in Table 1, by comparing Examples 1 to 4, it can be seen that as the average particle size of the particles in the negative active material power layer of the negative electrode sheet gradually increases, the rate performance shows an obvious downward trend, while the energy density first increases and then stabilizes, and at the same time, the capacity attenuation rate shows a significant trend after 1000 cycles. The main reason is that: small-sized negative active materials are beneficial to shortening the solid-phase diffusion path of lithium ions and improving the rate capability; while large-sized negative active materials can increase the packing density and improve the cycle performance by reducing the active interface and suppressing stress damage.

[0171] By comparing Examples 1, 5 and 6, it can be seen that appropriately increasing the crystal plane spacing of the negative active material power layer helps to improve the rate performance and has little effect on the energy density, but too large a crystal plane spacing will reduce the cycle stability. The main reason is:

[0172] 1. A larger crystal plane spacing can reduce the lithium-ion diffusion resistance, improve the electrolyte permeability, optimize ion transport, thereby enhancing the rate performance, and at the same time have a relatively small impact on the tap density.

[0173] 2. An overly large crystal plane spacing may reduce the mechanical strength of the electrode, allow some solvated lithium ions to embed, lead to an enhanced interfacial side reaction, and exacerbate the polarization effect, thereby affecting the cycle life.

[0174] It was also observed by comparing Example 1, Example 7, and Example 8 that as the average particle size of the particles in the energy layer of the negative electrode active material gradually increases, the rate performance decreases, the energy density first increases, and the cycle performance improves.

[0175] By comparing Example 1, Example 9 to Example 13, it can be seen that as the average particle size of the particles in the positive electrode active material layer of the positive electrode sheet gradually increases and the tap density increases, the rate performance decreases somewhat, and the energy density gradually increases; at the same time, the capacity attenuation rate after 1000 cycles shows a different trend from the particle size and tap density. That is, it decreases with the increase of the average particle size and increases with the increase of the tap density. The main reasons are as follows:

[0176] 1. A larger average particle size of the particles and a higher tap density will reduce the porosity of the electrode sheet, make the diffusion path of lithium ions inside the electrode longer, and increase the lithium-ion transport resistance.

[0177] 2. Increasing the average particle size of the particles and the tap density can increase the filling amount of the active material per unit volume, thereby enhancing the volume energy density.

[0178] 3. Larger particles can reduce the number of interfaces between particles, reduce the probability of side reactions, and reduce irreversible capacity loss. However, since the lithium ions consumed by the fragmentation of the interface of the positive electrode material are much less than the lithium loss of the negative electrode material to form the SEI (Solid Electrolyte Interface membrane), its impact is relatively small.

[0179] 4. An overly large tap density will increase the uneven growth of the CEI (Chemical-Electrochemical Interface) membrane, exacerbate side reactions, and thus accelerate capacity attenuation. In addition, by comparing Example 1 and Comparative Examples 1 to 3, it can be seen that when the average particle size of the particles in the energy layer and power layer of the negative electrode active material of the negative electrode sheet is the same and the positive electrode sheet uses the same tap density, its rate, energy density, and cycle stability are all inferior to the negative electrode sheet and positive electrode sheet disclosed in this application.

[0180] In summary, in the case of using double-layer electrodes, by limiting the average particle size ratio, crystal plane spacing ratio, and compaction density ratio of each particle, it is possible to improve the energy density while maintaining excellent rate performance and significantly improving the cycle stability of the battery, thus showing significant advantages in the application of high-performance lithium-ion batteries.

[0181] The above description and the accompanying drawings fully illustrate the embodiments of the present disclosure, enabling those skilled in the art to practice them. Other embodiments may include structural and other changes. Embodiments merely represent possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations may vary. Parts and features of some embodiments may be included in or substituted for parts and features of other embodiments. The embodiments of the present disclosure are not limited to the structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present disclosure is only limited by the appended claims.

Claims

1. A lithium-ion battery, characterized in that, Comprising: A negative electrode sheet, including a negative electrode current collector and a negative electrode active material energy layer and a negative electrode active material power layer respectively coated on both surface sides of the negative electrode current collector in sequence; wherein, the relationship between the negative electrode active material energy layer and the negative electrode active material power layer satisfies the following conditions: Among them, D 50，power is the average particle size of the particles in the power layer of the negative electrode active material, D 50，energy is the average particle size of the particles in the energy layer of the negative electrode active material, d power is the interplanar spacing of the crystal planes in the power layer of the negative electrode active material, d energy is the interplanar spacing of the crystal planes in the energy layer of the negative electrode active material; A positive electrode sheet, including a positive electrode current collector and two positive electrode active material layers respectively coated on both surface sides of the positive electrode current collector in sequence; wherein, the tap density of the positive electrode sheet satisfies the following conditions: Wherein, P1 is the tap density of the positive electrode sheet, and P2 is the tap density of the positive electrode sheet when a set thickness is removed.

2. The lithium ion battery according to claim 1, characterized in that, The average particle size D of the particles in the energy layer of the negative electrode active material 50，energy is in the range of 6.0 μm to 18.0 μm, and the range of its crystal plane spacing is 0.335 nm to 0.40 nm; the average particle size D of the particles in the power layer of the negative electrode active material 50，power is in the range of 3.0 μm to 10.0 μm, and the range of its crystal plane spacing is 0.335 nm to 0.50 nm.

3. The lithium-ion battery according to claim 1, characterized in that, The average particle diameter D of the particles in the positive electrode active material layer 50 is in the range of 4 μm to 15 μm.

4. The lithium-ion battery according to claim 1, characterized in that, The particles of the negative electrode active material power layer include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, deposited silicon carbon, silicon oxide, and prelithiated silicon oxide; wherein, when the particles of the negative electrode active material power layer include deposited silicon carbon, silicon oxide, or prelithiated silicon oxide, their total mass fraction does not exceed 25wt%.

5. The lithium-ion battery according to claim 4, characterized in that, Among the particles of the negative electrode active material power layer, the discharge capacity of its artificial graphite is 285 mAh / g to 340 mAh / g, the discharge capacity of its natural graphite is 330 mAh / g to 370 mAh / g, the discharge capacity of its soft carbon is 200 mAh / g to 300 mAh / g, the discharge capacity of its hard carbon is 300 mAh / g to 450 mAh / g, the discharge capacity of its deposited silicon carbon is 1200 mAh / g to 2000 mAh / g, the discharge capacity of its silicon oxide is 600 mAh / g to 1500 mAh / g, and the discharge capacity of its prelithiated silicon oxide is 1500 mAh / g to 1800 mAh / g.

6. The lithium-ion battery according to claim 1, characterized in that, The particles of the negative electrode active material energy layer include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

7. The lithium-ion battery according to claim 6, characterized in that, Among the particles of the negative electrode active material energy layer, the discharge capacity of its artificial graphite is 300 mAh / g to 350 mAh / g, the discharge capacity of its natural graphite is 360 mAh / g to 380 mAh / g, the discharge capacity of its soft carbon is 250 mAh / g to 350 mAh / g, and the discharge capacity of its hard carbon is 330 mAh / g to 495 mAh / g.

8. The lithium ion battery according to any one of claims 1 to 7, characterized in that, The positive electrode active material layer includes one or more of lithium nickel cobalt manganese oxide (Li1Ni x Co y Mn z M b O2), lithium cobalt oxide (LiCoO2), lithium nickel cobalt aluminate (Li1Ni x1 Co y1 Al z1 O2) and lithium nickel cobalt manganese ternary material (LiNi x2 Co y2 Mn z2 O2); wherein, 0.70 ≤ x ≤ 0.95, 0.15 ≤ y < 0.45, 0.05 ≤ z < 0.45, 0.0 ≤ b ≤ 0.25, and x + y + z + b = 1; the element M includes one or more of zirconium (Zr), tungsten (W), titanium (Ti), aluminum (Al), strontium (Sr), boron (B) and neodymium (Nd); 0.80 ≤ x1 ≤ 0.98, 0.01 ≤ y1 ≤ 0.15, 0.01 ≤ z1 ≤ 0.10, and x1 + y1 + z1 = 1; 0.33 ≤ x2 ≤ 0.90, 0.05 ≤ y2 ≤ 0.45, 0.05 ≤ z2 ≤ 0.45, and x2 + y2 + z2 = 1.

9. The lithium ion battery according to any one of claims 1 to 7, characterized in that, Also comprising: An electrolyte, including a lithium salt, an organic solvent, and an additive; Wherein, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluoro(oxalato)borate, and lithium bis(trifluoromethylsulfonyl)imide; the organic solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and ethyl methyl carbonate; the additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, vinylene sulfate, vinylene sulfite, vinylene carbonate, and vinyl carbonate.

10. The lithium ion battery according to any one of claims 1 to 7, characterized in that, The ratio range of the discharge capacity of the negative electrode sheet to the discharge capacity of the positive electrode sheet is 1.02 to 1.

22.

11. The lithium-ion battery according to any one of claims 1 to 7, characterized in that, The discharge characteristics of the lithium-ion battery are as follows: After the lithium-ion battery with a 100% charging rate is left standing at 25°C for 6 hours, at 25°C, it is discharged to 2.5V at a 0.1C rate, and the corresponding discharge capacity is Q1; it is discharged to 2.5V at a 2C rate, and the corresponding discharge capacity is Q2; it is discharged to 2.5V at a 5C rate, and the corresponding discharge capacity is Q3; Among them, the retention rate of discharge capacity Q2 / Q1 ≥ 70%, and the retention rate of discharge capacity Q3 / Q2 ≥ 45%; Among them, after 1000 charge-discharge cycles at a rate of 1C at 25°C, the decay rate Q of the discharge capacity d ≤25%.

12. A method for preparing a lithium-ion battery according to any one of claims 1 to 11, characterized in that, It includes: Preparing a positive electrode sheet: Mixing positive electrode coating materials, and sequentially coating two layers of positive electrode coating materials on both side surfaces of an aluminum foil, and obtaining the positive electrode sheet after drying and cold pressing; Preparing a negative electrode sheet: Separately mixing negative electrode energy layer materials and negative electrode power layer materials, and sequentially coating the negative electrode energy layer materials and the negative electrode power layer materials on both side surfaces of a copper foil, and obtaining the negative electrode sheet after drying and cold pressing; Preparing a battery core: After rolling and slitting the positive electrode sheet and the negative electrode sheet respectively, winding them together with a separator to obtain a battery core; Assembling a lithium-ion battery: Welding the tabs of the battery core to an electrical connection sheet, loading it into a battery case, and performing electrolyte injection, sealing and formation processes to obtain a lithium-ion battery.

13. An electrical device, characterized in that, It includes the lithium-ion battery according to any one of claims 1 to 10.

Images