CN117747909A - Lithium ion battery and electric equipment - Google Patents

Lithium ion battery and electric equipment Download PDF

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Publication number
CN117747909A
CN117747909A CN202211160158.6A CN202211160158A CN117747909A CN 117747909 A CN117747909 A CN 117747909A CN 202211160158 A CN202211160158 A CN 202211160158A CN 117747909 A CN117747909 A CN 117747909A
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layer
sub
positive electrode
negative electrode
material layer
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CN202211160158.6A
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Inventor
李枝贤
刘帅
田雷雷
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to CN202211160158.6A priority Critical patent/CN117747909A/en
Priority to PCT/CN2023/117492 priority patent/WO2024061011A1/en
Publication of CN117747909A publication Critical patent/CN117747909A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application provides a lithium ion battery and electric equipment. The lithium ion battery comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer which are arranged in a lamination manner, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer which are arranged in a lamination manner, the negative electrode material layer comprises a first sub-layer, a negative electrode active material in the first sub-layer comprises lithium titanate, and the area density of the first sub-layer is more than or equal to 0.1mg/cm 2 The capacity ratio Nc/Pc of the anode material layer and the cathode material layer was 0<Nc/Pc is less than or equal to 1.04. The lithium ion battery has higher energy density on the premise of high safety.

Description

Lithium ion battery and electric equipment
Technical Field
The application relates to the field of new energy batteries, in particular to a lithium ion battery and electric equipment.
Background
Lithium ion batteries are widely used in consumer electronics (e.g., mobile phones, notebook computers, etc.) and electric vehicles due to their high energy density and long cycle life. However, in recent years, the safety problem of lithium ion batteries has been increasingly remarkable, and if the batteries are improperly used, problems such as combustion and explosion occur. It has been found that the above safety problems of lithium ion batteries are mainly related to the following 4 short-circuit modes: 1) The positive electrode material layer contacts the negative electrode material layer; 2) The positive electrode material layer contacts the copper foil; 3) The aluminum foil contacts the negative electrode material layer; 4) The aluminum foil contacts the copper foil. Of the above short circuit modes, the 3 rd mode more easily causes occurrence of thermal runaway, and thus, combustion and explosion of the battery. In order to solve the problem of battery safety, one of the existing schemes is to use lithium titanate as a negative electrode active material, and since lithium titanate itself can suppress the formation of lithium dendrites, the use of lithium titanate as a negative electrode active material can improve safety between the separator aluminum foil and the negative electrode material layer. However, because of the low specific capacity of lithium titanate, when lithium titanate is used as a negative electrode active material, the energy density of the lithium ion battery is low, and the requirement of the existing product on the energy density cannot be met, so that the commercialized application cannot be realized.
Disclosure of Invention
The application provides a lithium ion battery and electric equipment to obtain the lithium ion battery with high safety and high energy density.
In a first aspect, the application provides a lithium ion battery, the lithium ion battery comprises a positive electrode plate and a negative electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer which are arranged in a lamination manner, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer which are arranged in a lamination manner, the negative electrode material layer comprises a first sub-layer, a negative electrode active material in the first sub-layer comprises lithium titanate, and the surface density of the first sub-layer is more than or equal to 0.1mg/cm 2 The capacity ratio Nc/Pc of the anode material layer and the cathode material layer was 0<Nc/Pc≤1.04。
The lithium ion battery of this application, negative pole piece include negative pole current collector and negative pole material layer, because negative pole active material in the first sublayer in the negative pole material layer is lithium titanate, in lithium ion battery's cyclic use in-process, lithium titanate has higher embedded lithium potential, can restrain the formation of lithium dendrite, and then can prevent that positive pole current collector and negative pole material layer from contacting and taking place thermal runaway, consequently, this lithium ion battery has higher security. In addition, the surface density of the first sub-layer is controlled to be more than or equal to 0.1mg/cm 2 And by controlling the capacity ratio Nc/Pc of the anode material layer and the cathode material layer to be 0<Nc/Pc is less than or equal to 1.04, the relative dosage between the positive electrode active material and the negative electrode active material can be effectively controlled, the dosage between the positive electrode active material and the negative electrode active material is more matched, and the positive electrode activity is avoidedThe active material and the negative electrode active material are unnecessarily added, so that when the capacity of the positive electrode plate of the battery is fixed, the dosage of the negative electrode material can be reduced, the volume of the negative electrode plate can be reduced, and the energy density of the lithium ion battery can be improved while the safety between the first sub-layer and the positive electrode current collector is ensured.
In one possible implementation, the capacity ratio Nc/Pc of the negative electrode material layer and the positive electrode material layer is 0.2-Nc/Pc-1.04; preferably, nc/Pc is equal to or greater than 0.3, nc/Pc is equal to or greater than 1.02, and even more preferably, nc/Pc is equal to or greater than 0.4, and Nc/Pc is equal to or greater than 1. The ratio of Nc/Pc is preferably selected for the through hole, so that the lithium ion battery can be effectively prevented from being subjected to cyclic attenuation caused by the fact that the relative content of the anode active material is too low, and the lithium ion battery can keep good cyclic performance.
In one possible implementation, the anode material layer includes a second sub-layer disposed between the anode current collector and the first sub-layer, and the anode active material in the second sub-layer includes a carbon material or a silicon-based material. Since the carbon material and the silicon-based material have a high specific capacity, the energy density of the lithium ion battery can be further improved by providing the anode active material containing the carbon material and/or the silicon-based material as the second sub-layer.
In one possible implementation, the mass ratio of the second sub-layer to the first sub-layer is greater than or equal to 1, preferably 7:1 to 12:1, preferably greater than or equal to 7.5:1, less than or equal to 11.5:1, more preferably greater than or equal to 8:1, and less than or equal to 11:1.
In one possible implementation, a lithium-containing metal layer is provided between the first and second sublayers. The lithium-containing metal layer has higher specific capacity, and the energy density of the lithium ion battery can be further improved by arranging the lithium-containing metal layer.
In one possible implementation, the negative electrode material layer includes a lithium-containing metal layer disposed between the negative electrode current collector and the first sublayer.
In one possible implementation, the length dimension of the first sub-layer is greater than or equal to the length dimension of the second sub-layer, and the width dimension of the first sub-layer is greater than or equal to the width dimension of the second sub-layer.
In the negative electrode material layer, the length of the first sub-layer is greater than or equal to that of the second sub-layer, and the width of the second sub-layer is greater than or equal to that of the second sub-layer, so that lithium can be deposited on the surface of the second sub-layer to form lithium dendrites when the negative electrode material layer is subjected to lithium precipitation, and the size of the first sub-layer is greater than or equal to that of the second sub-layer, so that the first sub-layer can prevent the lithium dendrites on the surface of the second sub-layer from penetrating through the diaphragm, and short circuit between the positive electrode pole piece and the negative electrode pole piece is avoided.
In a possible implementation manner, the orthographic projection area of the positive electrode material layer on the plane of the first sub-layer is smaller than or equal to the area of the first sub-layer, and the size difference between the first sub-layer and the positive electrode material layer along the width direction of the positive electrode material layer is smaller than 1.5mm; along the length direction of the positive electrode material layer, the size difference between the first sub-layer and the positive electrode material layer is smaller than 3mm.
In one possible implementation, a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 0.1mm along a width direction of the positive electrode material layer. In one possible implementation, a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 1mm along a length direction of the positive electrode material layer.
According to the lithium ion battery, lithium titanate is used as an active material of the first sub-layer, so that the total edge distance between the first sub-layer and the positive electrode material layer in the width direction is controlled to be 0-1.5 mm, the single side edge distance is controlled to be 0-0.1 mm, the total edge distance between the first sub-layer and the positive electrode material layer in the length direction is controlled to be 0-3.0 mm, and the single side edge distance is controlled to be 0-1 mm. In the implementation manner, the size difference between the first sub-layer and the positive electrode material layer is smaller, and further, the first sub-layer and the positive electrode material layer can be set to be the same size, so that the waste of the size space of the first sub-layer or the positive electrode material layer can be avoided, and the energy density of the lithium ion battery can be further improved.
In one possible implementation, the positive electrode material layer is doped with nano-metal oxide particles. The nano metal oxide is added into the positive electrode material layer, so that the activity of the positive electrode material layer can be reduced, the too high speed of lithium ions in the positive electrode material layer to be embedded into the negative electrode material layer is avoided, and the problem that the negative electrode material layer can not timely contain the lithium ions from the positive electrode material layer and is separated out on the surface is solved. By adding a proper amount of nano metal oxide into the positive electrode material layer, the dosage of the negative electrode active material can be reduced, the Nc/Pc ratio can be further reduced, and the energy density of the battery can be further improved.
In one possible implementation, at least one of the first sub-layer and the second sub-layer is doped with nano-metal oxide particles. The safety of the negative electrode material layer can be further improved by adding the nano metal oxide into at least one of the first sub-layer and the second sub-layer of the negative electrode material layer, the nano metal oxide is added into the negative electrode material layer, the reactivity of the negative electrode plate is reduced, when the aluminum foil contacts the negative electrode plate, the polarization of the negative electrode plate in a short circuit can be increased by adding the nano metal oxide, and therefore the safety of a battery is improved.
In one possible implementation, the positive electrode active material in the positive electrode material layer is LiCo 1-x M x O 2 Wherein x is more than or equal to 0 and less than or equal to 1, and M is selected from at least one of Ni, mn, al, ca, mg, sr, ti, V, cr, fe, cu, zn, mo, W, Y, la, zr, sn, se, te and Bi.
In one possible implementation, the positive current collector comprises an aluminum foil current collector, an aluminum alloy current collector, or an aluminum composite current collector; the negative electrode current collector comprises a copper foil current collector, a copper alloy current collector or a copper composite current collector.
The data in the above possible implementations of the present application, such as the area density of the first sub-layer, nc/Pc, the margin between the first sub-layer and the positive electrode material layer, and the like, should be understood as values within the engineering measurement error range during measurement, which are within the scope defined in the present application.
In a second aspect, the present application provides a lithium ion battery, including a positive electrode sheet and a negative electrode sheet, where the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer that are stacked, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer that are stacked, the negative electrode material layer includes a first sub-layer, and a negative electrode active material in the first sub-layer includes lithium titanate; the orthographic projection area of the positive electrode material layer on the plane of the first sub-layer is smaller than or equal to the area of the first sub-layer, and the size difference between the first sub-layer and the positive electrode material layer along the width direction of the positive electrode material layer is smaller than 1.5mm; along the length direction of the positive electrode material layer, the size difference between the first sub-layer and the positive electrode material layer is smaller than 3mm.
The lithium ion battery of this application, negative pole piece include negative pole current collector and negative pole material layer, because negative pole active material in the first sublayer in the negative pole material layer is lithium titanate, in lithium ion battery's cyclic use in-process, lithium titanate has higher embedded lithium potential, can restrain the formation of lithium dendrite, and then can prevent that positive pole current collector and negative pole material layer from contacting and taking place thermal runaway, consequently, this lithium ion battery has higher security. In addition, the size of the first sub-layer containing lithium titanate of the negative electrode material layer is larger than that of the positive electrode material layer, and when the size difference between the first sub-layer and the positive electrode material layer is limited in the range, on one hand, when the size of the first sub-layer is fixed, the size of the positive electrode material layer can be improved to the greatest extent, so that the area of the positive electrode material layer is increased, the capacity of the positive electrode material layer is further increased, and the energy density of the lithium ion battery can be improved while the safety between the first sub-layer and the positive electrode current collector is ensured. On the other hand, when the size of the positive electrode material layer is fixed, the size of the first sub-layer can be reduced to the greatest extent, the area of the negative electrode plate can be effectively reduced, the volume of the negative electrode plate is further reduced, and therefore the energy density of the lithium ion battery can be improved while the safety between the first sub-layer and the positive electrode current collector is ensured.
In one possible implementation, a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 0.1mm along a width direction of the positive electrode material layer. In one possible implementation, a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 1mm along a length direction of the positive electrode material layer. In one possible implementation, the positive electrode material layer is the same size as the first sub-layer. In the implementation manner, the size difference between the first sub-layer and the positive electrode material layer is smaller, and further, the first sub-layer and the positive electrode material layer can be set to be the same size, so that the waste of the size space of the first sub-layer or the positive electrode material layer can be avoided, and the energy density of the lithium ion battery can be further improved.
In one possible implementation, the anode material layer includes a second sub-layer disposed between the anode current collector and the first sub-layer, and the anode active material in the second sub-layer includes a carbon material or a silicon-based material.
In one possible implementation, a lithium-containing metal negative electrode layer is disposed between the first sub-layer and the second sub-layer.
In one possible implementation, the negative electrode material layer includes a lithium-containing metal layer disposed between the negative electrode current collector and the first sub-layer.
In a third aspect, the present application provides an electrical device, including an electricity consumption module and the lithium ion battery of the first aspect or the lithium ion battery of the second aspect of the present application, where the lithium ion battery is electrically connected with the electricity consumption module, and provides power for the electricity consumption module.
The technical effects that may be achieved by the third aspect may be described with reference to the corresponding effects in the first aspect, and the detailed description is not repeated here.
Drawings
Fig. 1 is a schematic structural diagram of a lithium ion battery;
fig. 2 is a schematic structural view of a negative electrode plate according to the present application;
fig. 3 is a schematic structural view of another negative electrode sheet of the present application;
fig. 4 is a schematic structural view of another negative electrode sheet of the present application;
fig. 5 is a schematic structural view of another negative electrode sheet of the present application.
Reference numerals:
10-a positive pole piece; 11-positive electrode current collector; 12-a positive electrode material layer; 20-a negative electrode piece; 21-a negative electrode current collector;
22-a layer of negative electrode material; 221-a first sub-layer; 222-a second sub-layer; 223-lithium metal layer; 30-a separator; 40-electrolyte.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail with reference to the accompanying drawings.
The terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the specification and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include, for example, "one or more" such forms of expression, unless the context clearly indicates to the contrary.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
Currently, the safety of lithium ion batteries has become a hotspot concern. In order to solve the safety problem of lithium ion batteries, one of the existing methods is to use lithium titanate as an anode active material and to improve the safety between the anode and the cathode by utilizing the characteristic that lithium titanate does not separate out of lithium. However, since the specific capacity of lithium titanate is low, the energy density of a lithium ion battery using lithium titanate as a negative electrode active material is low, and thus the commercial application of the existing electronic products cannot be satisfied.
In order to solve the above problems, the present application provides a lithium ion battery. Fig. 1 is a schematic structural diagram of a lithium ion battery, as shown in fig. 1, the lithium ion battery includes a positive electrode plate 10 and a negative electrode plate 20, a diaphragm 30 may be disposed between the positive electrode plate 10 and the negative electrode plate 20, and an electrolyte 40 filled between the positive electrode plate 10 and the negative electrode plate 20 and infiltrating the diaphragm 30. During charging, lithium ions are separated from the positive electrode active material of the positive electrode plate 10 and are inserted into the negative electrode active material of the negative electrode plate 20 after passing through the electrolyte 40; during discharge, lithium ions are extracted from the negative electrode active material, pass through the electrolyte 40, and then are inserted into the positive electrode active material.
As shown in fig. 1, the positive electrode tab 10 includes a positive electrode current collector 11 and a positive electrode material layer 12. The material of the positive electrode current collector 11 may be, for example, aluminum foil, aluminum alloy, aluminum composite, or gold foil. The specific material of the positive electrode current collector 11 may be selected according to the chemical potential of the negative electrode current collector, and is not particularly limited herein.
The positive electrode material layer 12 may include components such as a positive electrode active material, a conductive agent, and a binder. Wherein the positive electrode active material in the positive electrode material layer 12 may be LiCo 1-x M x O 2 Wherein x is more than or equal to 0 and less than or equal to 1, and M can be at least one of Ni, mn, al, ca, mg, sr, ti, V, cr, fe, cu, zn, mo, W, Y, la, zr, sn, se, te and Bi.
The conductive agent in the positive electrode material layer 12 may be conductive carbon black, acetylene black, carbon nanotubes or a mixture thereof. The binder may include one of polyvinylidene fluoride (polyvinylidene difluoride, PVDF), styrene-butadiene rubber (polymerized styrene butadiene rubber, SBR), carboxymethyl cellulose (carboxymethyl cellulose, CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyethylene oxide (polyethylene oxidized, PEO), vinylidene fluoride-hexafluoropropylene copolymer (poly (vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP), polymethyl methacrylate (polymethyl methacrylate, PMMA), polytetrafluoroethylene (PTFE), and a combination of at least two thereof.
Wherein nano metal can be added into the positive electrode material layer 12The oxide is silicon oxide (SiO) 2 ) Boehmite (AlOOH), alumina (Al) 2 O 3 ) Magnesium oxide (MgO), zirconium oxide (ZrO), zinc oxide (ZnO), titanium oxide (TiO) 2 ) And the like.
Fig. 2 is a schematic view of a negative electrode tab, as shown in fig. 2, in an alternative embodiment, the negative electrode tab 20 includes a negative electrode current collector 21 and a negative electrode material layer 22 arranged in a stack. The material of the negative electrode current collector 21 includes, but is not limited to, copper foil, copper alloy, copper composite material, or the like. The negative electrode material layer 22 includes at least a first sub-layer 221, and the first sub-layer 221 may include lithium titanate, a conductive agent, and a binder. Wherein the lithium titanate may be elemental lithium titanate (Li 4 Ti 5 O 12 ) May be carbon-coated lithium titanate (C-Li) 4 Ti 5 O 12 ) Two kinds of compositions are also possible. The conductive agent and the binder in the first sub-layer 221 may refer to optional materials of the conductive agent and the binder in the positive electrode material layer, and a detailed description thereof will not be repeated.
Wherein, nano metal oxide can be added in the first sub-layer 221, and the nano metal oxide can be silicon oxide (SiO 2 ) Boehmite (AlOOH), alumina (Al) 2 O 3 ) Magnesium oxide (MgO), zirconium oxide (ZrO), zinc oxide (ZnO), titanium oxide (TiO) 2 ) And the like.
Fig. 3 is a schematic structural diagram of an anode tab according to another embodiment, as shown in fig. 3, in an alternative embodiment, the anode material layer 22 of the anode tab further includes a second sub-layer 222, where the second sub-layer 222 is located between the anode current collector 21 and the first sub-layer 221. The second sub-layer 222 includes a negative electrode active material, a conductive agent, and a binder, wherein the negative electrode active material in the second sub-layer 222 may include a carbon material, a silicon-based material, or the like, and the silicon-based material may include, for example, a silicon material, a silicon composite material, a silicon-carbon material, or the like. The negative electrode active material may be, for example, one or more selected from graphite, si, siOx, si-C and Si halides, wherein 0< x.ltoreq.2. The first sub-layer 221 may be a negative electrode material layer formed of lithium metal or lithium alloy, in addition to a negative electrode material layer including a carbon material or a silicon-based material. The mass ratio of the second sub-layer 222 to the first sub-layer 221 may be, for example, 7:1 to 12:1, and the ratio of the two may be, for example, 7:1, 8:1, 9:1, 10:1, 11:1 or 12:1.
In this embodiment, the first sublayer 221 is located at the outermost layer of the negative electrode plate, the second sublayer 222 is located at the middle layer, and the specific capacity of the negative electrode active material, i.e. the carbon material and the silicon-based material, in the second sublayer 222 is much higher than that of lithium titanate, so that the energy density of the lithium ion battery can be further improved by providing the second sublayer 222. The negative electrode active material in the second sub-layer 222 is a negative electrode active material that is liable to precipitate lithium, and the lithium precipitated on the surface of the second sub-layer 222 can be confined between the first sub-layer 221 and the second sub-layer 222 by disposing the negative electrode active material in the intermediate layer. In addition, the negative electrode active material in the second sub-layer 222 can be prevented from contacting the positive electrode current collector, so that the safety of the lithium ion battery is further improved.
Fig. 4 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present application, as shown in fig. 4, in another embodiment of the present application, the negative electrode material layer 22 may further include a lithium metal layer 223 in addition to the first sub-layer 221 and the second sub-layer 222, and the lithium metal layer 223 is located between the first sub-layer 221 and the second sub-layer 222. The lithium metal layer 223 between the first sublayer 221 and the second sublayer 222 may be a lithium metal layer 223 added separately during the preparation of the negative electrode tab, or may be a lithium metal layer 223 formed by lithium precipitated from the second sublayer 222 during the cycling of the lithium ion battery.
Also, by providing the second sub-layer 222 and the lithium metal layer 223, the energy density and safety of the lithium ion battery can be further improved. In addition, when the negative electrode active material in the second sub-layer 222 is a silicon-based material, lithium supplementation to the silicon-based material can be achieved through the formed lithium metal layer 223, so that the cycle stability of the silicon-based material is improved, and the cycle performance of the lithium ion battery is further improved.
When the negative electrode tab includes both the first sub-layer 221 and the second sub-layer 222, the length dimension of the first sub-layer 221 is greater than or equal to the length dimension of the second sub-layer 222, and the width dimension of the first sub-layer 221 is greater than or equal to the width dimension of the second sub-layer 222, so as to avoid contact between the second sub-layer 222 and the positive electrode tab.
The structure of the negative electrode tab is exemplified above, and the relationship between the positive electrode material layer and the negative electrode material layer will be explained below.
In the lithium ion battery of each possible embodiment of the present application, the capacity ratio Nc/Pc of the anode material layer to the cathode material layer satisfies 0<Nc/Pc is less than or equal to 1.04, wherein the surface density of the first sub-layer 221 is more than or equal to 0.1mg/cm 2 。
By making the capacity ratio Nc/Pc of the anode material layer to the cathode material layer satisfy 0<Nc/Pc is less than or equal to 1.04, and the surface density of the first sub-layer is more than or equal to 0.1mg/cm 2 The relative dosage between the positive electrode active material and the negative electrode active material can be effectively controlled, so that the dosage between the positive electrode active material and the negative electrode active material is more matched, and unnecessary addition of the positive electrode active material and the negative electrode active material is avoided.
As an exemplary illustration, the areal density of the first sublayer may be, for example, 0.1mg/cm 2 、0.2mg/cm 2 、0.3mg/cm 2 、0.4mg/cm 2 、0.5mg/cm 2 、0.6mg/cm 2 、0.7mg/cm 2 、0.8mg/cm 2 、0.9mg/cm 2 Or 1.0mg/cm 2 Or greater, the maximum density of the first sub-layer is not particularly limited herein.
As a preferred embodiment, the capacity ratio Nc/Pc of the anode material layer to the cathode material layer is more than or equal to 0.2, further, nc/Pc is more than or equal to 0.3, still further, nc/Pc is more than or equal to 0.5; illustratively, the capacity ratio Nc/Pc of the negative electrode material layer to the positive electrode material layer is 1.04 or less, further, nc/Pc is 1.00 or less, and still further, nc/Pc is 0.95 or less.
By optimizing the lower limit value of the capacity ratio Nc/Pc of the anode material layer and the cathode material layer, the lithium separation risk can be reduced as much as possible on the premise of ensuring the improvement of the energy density of the lithium ion battery, and the safety and the cycle performance of the lithium ion battery are improved. The use amount of the anode material can be further reduced by optimizing the upper limit value of the capacity ratio Nc/Pc of the anode material layer to the cathode material layer, and the energy density of the lithium ion battery can be further improved.
Fig. 5 is a dimensional relationship between the first sub-layer and the positive electrode material layer in an embodiment of the present application, as shown in fig. 5, the dimension of the first sub-layer 221 is greater than or equal to the dimension of the positive electrode material layer 12, and the single-side margin W1 or W2 between the first sub-layer 221 and the positive electrode material layer 12 in the width direction is greater than or equal to 0mm, preferably 0 to 0.1mm, and the total double-side margin w1+w2 is 0 to 1.5mm. In the longitudinal direction of the first sub-layer 221, the one-sided margin L1 or L2 between the first sub-layer 221 and the positive electrode material layer 12 is 0mm or more, preferably 0 to 1mm, and the double-sided total margin l1+l2 is 0 to 3mm. By optimizing the size difference between the first sub-layer 221 and the positive electrode material layer 12, on the one hand, when the size of the first sub-layer 221 is fixed, the size of the positive electrode material layer 12 can be increased to the maximum extent, so as to increase the area of the positive electrode material layer 12, and thus, the energy density of the lithium ion battery can be increased on the basis of increasing the capacity of the positive electrode material layer 12. On the other hand, when the size of the positive electrode material layer 12 is fixed, the size of the first sub-layer 221 can be reduced to the greatest extent, so that the area of the negative electrode plate can be effectively reduced, the energy density of the lithium ion battery can be improved on the basis of reducing the volume of the negative electrode plate, and the energy density of the lithium ion battery can be improved while the safety between the first sub-layer and the positive electrode current collector can be ensured due to the high safety of the first sub-layer.
When the size difference between the first sub-layer and the positive electrode material layer is in the range of 0-0.1 mm, a lithium metal layer can be precipitated between the negative electrode current collector and the first sub-layer in the charge-discharge process of the battery, and the precipitated lithium metal layer can not puncture the first sub-layer due to the high safety of the first sub-layer between the first sub-layer and the negative electrode current collector, and further, can be used as a negative electrode active material, so that the energy density of a negative electrode plate is effectively improved.
In addition, when the size difference between the first sub-layer and the positive electrode material layer is in the range of 0-0.1 mm, a second sub-layer containing a silicon-based material can be arranged between the first sub-layer and the negative electrode current collector, at this time, lithium is precipitated on the surface of the second sub-layer to form a lithium metal layer (the specific capacity is up to 3860 mAh/g) in the charging process of the lithium ion battery, and the precipitated lithium can supplement lithium to the silicon-based material, so that the lithium supplementing cost of the silicon-based material can be reduced, and the utilization rate of the battery can be further improved.
The above description is given of the structure of the lithium ion battery, and the performance of the lithium ion battery of the present application will be specifically described with reference to specific embodiments.
Example 1
The embodiment of the application is a lithium ion battery, which mainly comprises a positive electrode plate 10, a negative electrode plate 20 (the negative electrode current collector is copper foil, the negative electrode material layer comprises a first sublayer 221 and a second sublayer 222, the structure can be referred to as fig. 3, the single side edge distances L1, L2, W1 and W2 are respectively 0.1mm, the structure can be referred to as fig. 5), and LiFP 6 Electrolyte, PE isolating film, etc. The preparation process of the lithium ion battery comprises the following steps:
s11, preparing a positive electrode plate: lithium cobaltate (with specific capacity of 180 mAh/g), conductive carbon black and polyvinylidene fluoride binder PVDF are respectively mixed according to the mass ratio: 96%, 2% of N-methylpyrrolidone (NMP) is taken as a solvent, the mixture is stirred uniformly to obtain positive electrode slurry, the positive electrode slurry is coated on the surface of an aluminum foil current collector in a squeezing or transfer coating mode, and the positive electrode plate is obtained after drying, wherein the weight of a positive electrode material layer is 0.216g.
S12, preparing a first negative electrode slurry: the lithium titanate (the specific capacity is 170 mAh/g), the conductive carbon black and the polyvinylidene fluoride binder PVDF are respectively prepared according to the mass ratio: 96%, 2% and 2% of the mixture are mixed, and NMP is used as a solvent to be uniformly stirred to obtain first negative electrode slurry.
S13, preparing a second negative electrode slurry: graphite (with the specific capacity of 355 mAh/g), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively mixed according to the mass ratio: 96%:1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the negative second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate 20 containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer was 0.11g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this embodiment, the Nc/Pc ratio of the anode material layer to the cathode material layer is 1.0, where Nc/Pc is calculated as follows: 355×0.11×0.96/(180×0.96×0.216) =1.0.
Since the capacity of the first sub-layer is small and the capacity of the negative electrode material layer is mainly the capacity of the second sub-layer, the specific capacity of the negative electrode material layer in example 1 is the specific capacity of the second sub-layer.
Example 2
The embodiment of the application is a lithium ion battery, and the preparation process of the lithium ion battery can refer to the preparation process of the lithium ion battery in embodiment 1, and the difference between the preparation process and embodiment 1 is that the second negative electrode material adopts a graphite-silica composite material, so that the capacity ratio of the negative electrode material layer to the positive electrode material layer is reduced to 0.8, and the second negative electrode material self-supplements lithium. The specific process comprises the following steps:
S11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 1. Wherein the weight of the positive electrode material layer was 0.31g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 1.
S13, preparing a second negative electrode slurry: graphite-silica composite material (the mass ratio of graphite to silica is 0.85:0.15, the specific capacity is 480 mAh/g), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively prepared according to the mass ratio of 96%:1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the graphite-silicon negative second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer was 0.093g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=480×0.093×0.96/(180×0.96×0.31) =0.8 of the negative electrode material layer to the positive electrode material layer.
Example 3
The embodiment of the present application is a lithium ion battery, and the preparation process of the lithium ion battery can refer to the preparation process of the lithium ion battery of embodiment 2, and the difference between the preparation process and embodiment 2 is that a lithium metal layer is added to supplement lithium for the second negative electrode material layer. The specific process comprises the following steps:
s11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 1. Wherein the weight of the positive electrode material layer was 0.31g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 1.
S13, preparing a second negative electrode slurry: the graphite-silica composite material (the mass ratio of graphite to silica is 0.85:0.15), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively prepared according to the mass ratio of 96 percent: 1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the graphite-silicon negative second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of a copper foil current collector in an extrusion or transfer coating mode, drying, setting a layer of lithium metal layer on the surface of the second sub-layer, wherein the thickness of the lithium metal layer is 10 mu m +/-0.5 mu m, coating the first negative electrode slurry on the surface of the lithium metal layer in a gravure printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate 20 containing the first sub-layer 221, the lithium metal layer 223 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 4. Wherein the weight of the negative electrode material layer was 0.093g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=480×0.093×0.96/(180×0.96×0.31) =0.8 of the negative electrode material layer to the positive electrode material layer.
Example 4
The embodiment of the present application is a lithium ion battery, and the preparation process of the lithium ion battery can refer to the preparation process of the lithium ion battery in embodiment 1, and the difference between the preparation process and embodiment 1 is that the second negative electrode material layer is not included. The specific process comprises the following steps:
s11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 1. Wherein the weight of the positive electrode material layer was 0.11g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 1.
And S13, coating the first negative electrode slurry on the surface of a copper foil current collector in an extrusion or transfer coating mode, and drying to obtain the negative electrode plate 20 containing the first sublayer 221, wherein the structure of the obtained negative electrode plate can be referred to as figure 2. Wherein the weight of the negative electrode material layer was 0.093g.
S14, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=170×0.093×0.96/(180×0.96×0.11) =0.8 of the negative electrode material layer to the positive electrode material layer.
In examples 1 to 4, the relative dimensional relationship between the first sub-layer and the positive electrode material layer can be seen in fig. 5, wherein the dimensional differences L1 and L2 in the longitudinal direction are both 0.1mm, and the dimensional differences W1 and W2 in the width direction are both 0.1mm.
Example 5
The lithium ion battery of this example was prepared in the same manner as in example 1, except that the first sub-layer and the positive electrode material layer had the same dimensions, i.e., the single-sided pitches L1 and L2 in the longitudinal direction were 0mm respectively, and the single-sided pitches W1 and W2 in the width direction were 0mm respectively, as compared with example 1.
Example 6
The embodiment of the application is a lithium ion battery, and the preparation process of the lithium ion battery can refer to the preparation process of the lithium ion battery of embodiment 2, wherein the difference is that the capacity ratio of the negative electrode material layer to the positive electrode material layer is reduced to 0.2. The specific process comprises the following steps:
s11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 2. Wherein, the weight of the positive electrode material layer is: 0.31g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 2.
S13, preparing a second negative electrode slurry: the graphite-silica composite material (the mass ratio of graphite to silica is 0.85:0.15), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively prepared according to the mass ratio of 96 percent: 1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the graphite-silicon negative electrode second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer was 0.023g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=480×0.023×0.96/(180×0.96×0.31) =0.2 of the negative electrode material layer to the positive electrode material layer.
Example 7
The lithium ion battery of example 7 was prepared in the same manner as in example 2, except that the capacity ratio of the negative electrode material layer to the positive electrode material layer was reduced to 0.4 as compared with example 2. Specific values are listed in table 1.
S11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 2. Wherein the weight of the positive electrode material layer was 0.31g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 2.
S13, preparing a second negative electrode slurry: the graphite-silica composite material (the mass ratio of graphite to silica is 0.85:0.15), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively prepared according to the mass ratio of 96 percent: 1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the graphite-silicon negative second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer was 0.047g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=480×0.047×0.96/(180×0.96×0.31) =0.4 of the negative electrode material layer to the positive electrode material layer.
Example 8
The lithium ion battery of example 8 was prepared in the same manner as in example 2, except that the capacity ratio of the negative electrode material layer and the positive electrode material layer was 0.6 and the single side pitches L1, L2, W1 and W2 were 0.05mm, respectively, as compared with example 2, and specific values are shown in table 1.
S11, preparing a positive electrode plate: reference is made to the preparation of the positive electrode sheet in example 2. Wherein the weight of the positive electrode material layer was 0.31g.
S12, preparing a first negative electrode slurry: reference is made to the preparation procedure in example 2.
S13, preparing a second negative electrode slurry: the graphite-silica composite material (the mass ratio of graphite to silica is 0.85:0.15), conductive carbon black, styrene-butadiene rubber and carboxymethyl cellulose are respectively prepared according to the mass ratio of 96 percent: 1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the graphite-silicon negative second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer is 0.065g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, the capacity ratio Nc/pc=480×0.065×0.96/(180×0.96×0.31) =0.6 of the negative electrode material layer to the positive electrode material layer.
Comparative example 1
The embodiment of the application is a lithium ion battery, which mainly comprises a positive pole piece, a negative pole piece and LiFP 6 Electrolyte, PE isolating film, etc. The battery provided in comparative example 1 only comprises one negative electrode layer using graphite, each having a single side pitch of 0.1mm. The preparation process of the lithium ion battery comprises the following steps:
s11, preparing a positive electrode plate: the preparation method comprises the following steps of respectively mixing lithium cobaltate, conductive carbon black and polyvinylidene fluoride binder PVDF according to mass ratio: 96%, 2% and N-methylpyrrolidone (NMP) is used as a solvent, the mixture is stirred uniformly to obtain positive electrode slurry, the positive electrode slurry is coated on the surface of an aluminum foil current collector in an extrusion or transfer coating mode, and the positive electrode plate is obtained after drying. Wherein the weight of the positive electrode material layer was 0.216g.
S12, preparing negative electrode slurry: graphite, conductive carbon black, styrene butadiene rubber and carboxymethyl cellulose are respectively mixed according to the mass ratio: 96%:1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the cathode slurry.
And S13, coating the negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, and drying to obtain the negative electrode plate. Wherein the weight of the negative electrode material layer was 0.117g.
S14, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, nc/pc=355×0.117×0.96/(180×0.96×0.216) =1.07 of the negative electrode sheet.
Comparative example 2
The embodiment of the application is a lithium ion battery, which mainly comprises a positive pole piece, a negative pole piece and LiFP 6 Electrolyte, PE isolating film, etc. The battery provided in comparative example 2 comprises two negative electrode layers, the first negative electrode layer being lithium titanate and the second negative electrode layer being graphite, each edge distance being 0.1mm. The preparation process of the lithium ion battery comprises the following steps:
s11, preparing a positive electrode plate: reference is made to comparative example 1. Wherein the weight of the positive electrode material layer was 0.216g.
S12, preparing a first negative electrode slurry: the method comprises the following steps of respectively proportioning lithium titanate, conductive carbon black and polyvinylidene fluoride binder PVDF according to mass ratio: 96%, 2% and 2% of the mixture are mixed, and NMP is used as a solvent to be uniformly stirred to obtain first negative electrode slurry.
S13, preparing a second negative electrode slurry: graphite, conductive carbon black, styrene butadiene rubber and carboxymethyl cellulose are respectively mixed according to the mass ratio: 96%:1%: mixing 2% to 1%, and uniformly stirring with water as a solvent to obtain the second negative electrode slurry.
S14, coating the second negative electrode slurry on the surface of the copper foil current collector in an extrusion or transfer coating mode, drying, coating the first negative electrode slurry on the surface of the negative second sub-layer in an intaglio printing, extrusion or transfer coating mode, and drying to obtain the negative electrode plate containing the first sub-layer 221 and the second sub-layer 222, wherein the mass ratio of the second sub-layer 222 to the first sub-layer 221 is 9:1. The structure of the obtained negative electrode sheet can be referred to fig. 3. Wherein the weight of the negative electrode material layer was 0.117g.
S15, assembling the lithium ion battery by using the positive pole piece, the negative pole piece, the diaphragm and the electrolyte group.
In this example, nc/pc=355×0.117×0.96/(180×0.96×0.216) =1.07 of the negative electrode sheet.
Comparative example 3
The embodiment of the application is a lithium ion battery, which mainly comprises a positive pole piece, a negative pole piece and LiFP 6 Electrolyte, PE isolating film, etc. Which is a kind ofThe preparation process was the same as comparative example 2, except that each of the single side pitches of the first sublayer and the positive electrode material layer was 1mm, respectively.
In each of the above examples and comparative examples, the capacity ratio Nc/Pc of the anode material layer to the cathode material layer, the capacity (Nc) of the anode material layer=the specific capacity of the anode active material, the mass ratio of the anode active material; capacity of positive electrode material layer (Pc) =specific capacity of positive electrode active material positive electrode material mass positive electrode active material mass ratio.
The mass of the anode active material is the total mass of the anode active material in the anode material layer, and the mass ratio of the anode active material is the ratio of the mass of the anode active material to the mass of the anode material in the anode material layer. The mass ratio of the positive electrode active material is the ratio of the mass of the positive electrode active material in the positive electrode material layer to the mass of the positive electrode material.
The lithium ion batteries of each example and comparative example were subjected to a needling safety test at a needling speed of 100mm/s and a nail diameter of 2.0mm, and the batteries were observed for burning or smoking, and the pass rate of each group of samples was recorded. The test results are shown in Table 1.
TABLE 1
As can be seen from the data in table 1, each of the lithium ion batteries of examples 1-8 of the present application has an energy density higher than that of comparative example 1 and a pass rate for safety test much higher than that of comparative example 1. As is clear from the data relating to examples 1 to 8 and comparative example 2, when the value of Nc/Pc is greater than 1.04, such as 1.07 of comparative examples 2 and 3, the corresponding lithium ion battery has higher safety, but the energy density thereof is lower than that of examples 1 to 8.
In each lithium ion battery of embodiments 1-5, the negative electrode plate is provided with the first sublayer containing lithium titanate, and the energy density of the battery composed of lithium titanate is relatively low, so that in order to reduce the loss of energy density caused by lithium titanate, the safety of the negative electrode plate is not affected, and the purpose of improving the energy density of the lithium ion battery is achieved by adjusting the ratio of Nc/Pc in each embodiment of the application.
In embodiment 2, during the continuous charging, excessive lithium is stored at the interface between the first sub-layer and the second sub-layer, and the second sub-layer contains the silicon-based material, so that the precipitated lithium can be used for supplementing lithium to the silicon-based material, thereby simplifying the lithium supplementing process of the traditional silicon-based material and reducing the lithium supplementing cost of the silicon-based material. Meanwhile, the first sub-layer containing lithium titanate can be used as a protective layer to prevent precipitated lithium from forming lithium dendrites to pierce through the diaphragm.
In the lithium ion battery of embodiment 3, by directly providing the lithium metal layer, since the lithium metal has a higher specific capacity and a specific capacity up to 3860mAh/g, the lithium supplementing effect on the silicon-based material can be improved, so that the energy density of the negative electrode plate can be improved, and the energy density of the battery can be further improved.
The lithium ion battery of example 4 only contains the first sublayer, and the lithium metal layer can be directly formed on the surface of the negative electrode current collector in the charge-discharge cycle process of the lithium ion battery of this example, so that the energy density of the lithium ion battery can be further improved. In the lithium ion battery of the embodiment, the lithium metal layer can be formed by low-temperature charging, overcharging or the like, so that the forming cost and difficulty of the lithium metal layer can be reduced.
In the lithium ion battery of embodiment 5, the first sub-layer and the positive electrode material layer are disposed opposite to each other, and the dimensions of the first sub-layer and the positive electrode material layer are substantially the same, so that the waste of the dimension space of the first sub-layer or the positive electrode material layer can be avoided, the space in the length and width directions of the lithium ion battery can be fully utilized, and the energy density of the battery can be improved.
As is clear from the data relating to examples 1 and 5, the energy density of the lithium ion battery can be increased by decreasing the single-sided margin between the first sub-layer and the positive electrode material layer.
From the data relating to examples 1-2 and examples 6-8, it can be seen that the energy density of the obtained lithium ion batteries is different when the Nc/Pc ratio is different. When the ratio of Nc/Pc is in the range of 0.6-1.0, the lithium ion battery with both safety and higher energy density can be obtained.
In summary, by controlling the Nc/Pc ratio or controlling the values of the single side pitches of the positive electrode material layer and the negative electrode first sub-layer, a lithium ion battery with both safety and higher energy density can be obtained.
Based on the same technical conception, the application provides electric equipment, which comprises an electricity utilization module and the lithium ion battery, wherein the lithium ion battery is electrically connected with the electricity utilization module to provide power for the electricity utilization module.
The electric equipment comprises power devices such as mobile phones, computers, telephone watches, plane display devices, energy storage equipment, vehicles and the like.
The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present application, and the changes or substitutions are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (15)

1. The lithium ion battery is characterized by comprising a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer which are arranged in a laminated manner, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer which are arranged in a laminated manner, the negative electrode material layer comprises a first sub-layer, a negative electrode active material in the first sub-layer comprises lithium titanate, and the surface density of the first sub-layer is more than or equal to 0.1mg/cm 2 The capacity ratio Nc/Pc of the negative electrode material layer and the positive electrode material layer is 0<Nc/Pc≤1.04。
2. The lithium ion battery according to claim 1, wherein a capacity ratio Nc/Pc of the negative electrode material layer and the positive electrode material layer is 0.2-Nc/Pc-1.04.
3. The lithium ion battery of claim 1 or 2, wherein the negative electrode material layer comprises a second sub-layer disposed between the negative electrode current collector and the first sub-layer, the negative electrode active material in the second sub-layer comprising a carbon material or a silicon-based material.
4. A lithium ion battery according to claim 3, wherein a lithium-containing metal layer is provided between the first sub-layer and the second sub-layer.
5. The lithium ion battery of claim 3 or 4, wherein the first sub-layer has a length dimension greater than or equal to a length dimension of the second sub-layer, and wherein the first sub-layer has a width dimension greater than or equal to a width dimension of the second sub-layer.
6. The lithium-ion battery of any of claims 3-5, wherein the mass ratio of the second sub-layer to the first sub-layer is greater than or equal to 1.
7. The lithium ion battery of claim 1 or 2, wherein the negative electrode material layer comprises a lithium-containing metal layer disposed between the negative electrode current collector and the first sub-layer.
8. The lithium ion battery of any of claims 1-7, wherein an orthographic projection area of the positive electrode material layer on a plane of the first sub-layer is smaller than or equal to an area of the first sub-layer, and a dimension difference between the first sub-layer and the positive electrode material layer along a width direction of the positive electrode material layer is smaller than 1.5mm; along the length direction of the positive electrode material layer, the size difference between the first sub-layer and the positive electrode material layer is smaller than 3mm.
9. The lithium ion battery of claim 8, wherein a single side margin between the positive electrode material layer and the first sub-layer is 0 to 0.1mm in a width direction of the positive electrode material layer.
10. The lithium ion battery of claim 8 or 9, wherein a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 1mm along a length direction of the positive electrode material layer.
11. The lithium ion battery is characterized by comprising a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer which are arranged in a laminated manner, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer which are arranged in a laminated manner, the negative electrode material layer comprises a first sub-layer, and a negative electrode active material in the first sub-layer comprises lithium titanate;
the orthographic projection area of the positive electrode material layer on the plane of the first sub-layer is smaller than or equal to the area of the first sub-layer, and the size difference between the first sub-layer and the positive electrode material layer along the width direction of the positive electrode material layer is smaller than 1.5mm; along the length direction of the positive electrode material layer, the size difference between the first sub-layer and the positive electrode material layer is smaller than 3mm.
12. The lithium ion battery of claim 11, wherein a single side margin between the positive electrode material layer and the first sub-layer is 0 to 0.1mm in a width direction of the positive electrode material layer.
13. The lithium ion battery of claim 11 or 12, wherein a single-sided margin between the positive electrode material layer and the first sub-layer is 0 to 1mm along a length direction of the positive electrode material layer.
14. The lithium ion battery of any of claims 11-13, wherein the positive electrode material layer is the same size as the first sub-layer.
15. An electrical consumer comprising an electrical module and a lithium-ion battery as claimed in any one of claims 1-14 connected to the electrical module.
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