CN112421031A - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
- Publication number
- CN112421031A CN112421031A CN202011331981.XA CN202011331981A CN112421031A CN 112421031 A CN112421031 A CN 112421031A CN 202011331981 A CN202011331981 A CN 202011331981A CN 112421031 A CN112421031 A CN 112421031A
- Authority
- CN
- China
- Prior art keywords
- active material
- negative electrode
- electrochemical device
- graphite
- negative
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- 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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
-
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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 present application relates to an electrochemical device and an electronic device. Specifically, the present application provides an electrochemical device, which comprises a negative electrode, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises graphite, wherein the graphite exhibits a low voltage rebound ratio when being charged and discharged through a button cell. The electrochemical device of the present application has a balanced combination of properties.
Description
Technical Field
The application relates to the field of energy storage, in particular to a negative electrode active material, and an electrochemical device and an electronic device using the same.
Background
Electrochemical devices (e.g., lithium ion batteries) are widely used due to their advantages of environmental friendliness, high operating voltage, large specific capacity, and long cycle life, and have become the most promising new green chemical power source in the world today. Small-sized lithium ion batteries are generally used as power sources for driving portable electronic communication devices (e.g., camcorders, mobile phones, or notebook computers, etc.), particularly high-performance portable devices. In recent years, medium-and large-sized lithium ion batteries having high output characteristics have been developed for use in Electric Vehicles (EV) and large-scale Energy Storage Systems (ESS). With the wide application of lithium ion batteries, people have higher and higher requirements on the charging speed of the lithium ion batteries. Improving the fast charge performance of a lithium ion battery generally reduces its first efficiency, increases the direct current internal resistance, and causes the phenomenon of lithium precipitation. How to balance various properties in electrochemical devices has become one of the research and development directions.
In view of the above, it is desirable to provide an electrochemical device and an electronic device having a balanced combination of properties.
Disclosure of Invention
The present application seeks to solve at least one of the problems presented in the related art, at least to some extent, by providing an electrochemical device and an electronic device.
According to one aspect of the present application, there is provided an electrochemical device including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material including graphite, wherein: and performing charge and discharge tests by using the button cell which takes lithium as a negative electrode and the graphite as a positive electrode, wherein the voltage rebound ratio of the button cell discharging at 50 muA is not more than 13.
According to the embodiment of the application, the button cell which takes lithium as a negative electrode and the graphite as a positive electrode is used for carrying out charge and discharge tests, and the voltage rebound ratio of the button cell which discharges at 10 muA is not more than 6.
According to an embodiment of the present application, the negative active material has a gram capacity of 340mAh to 375 mAh.
According to an embodiment of the present application, the specific surface area of the anode active material is 1.2cm2G to 2.2cm2/g。
According to an embodiment of the present application, the negative active material has a median particle diameter of 9.5 μm to 15 μm.
According to the examples of the present application, the graphitization degree of the negative active material measured by the X-ray diffraction method is 93% to 96%.
According to the examples of the present application, the ratio C004/C110 of the peak area C004 of the (004) face and the peak area C110 of the (110) face of the negative electrode active material obtained by X-ray diffraction spectrum measurement is in the range of 2 to 6.
According to an embodiment of the present application, the negative electrode active material includes crystal grains, and a crystal grain size La of the crystal grains in a horizontal direction is 150nm to 160nm and a crystal grain size Lc of the crystal grains in a vertical direction is 33nm to 35nm by an X-ray diffraction method.
According to an embodiment of the present application, the thermal weight loss temperature of the anode active material is 850 ℃ to 930 ℃.
According to the embodiment of the present application, when the electrochemical device is in a voltage state of 3.0V, a ratio C004'/C110' of a peak area C004 'of a (004) face and a peak area C110' of a (110) face of the negative electrode measured by an X-ray diffraction spectrum is in a range of 9.2 to 15.
According to an embodiment of the present application, when the electrochemical device is in a 3.0V voltage state, an area of the negative active material having an orientation degree of 20 ° to 70 ° accounts for 50% to 62% of a total area of the negative active material, as measured by a polarization microscope.
According to an embodiment of the present application, the negative electrode active material layer has a resistivity of 0.001 Ω · m to 0.1 Ω · m.
According to yet another aspect of the present application, there is provided an electronic device comprising an electrochemical device according to the present application.
According to another aspect of the present application, there is provided a method of preparing graphite in an electrochemical device according to the present application, the method including:
(a) mixing the first precursor with a binder to form secondary particles;
(b) graphitizing the secondary particles at a temperature of from 3000 ℃ to 3500 ℃ to form a graphitized product;
(c) coating the graphitized product with pitch to form a first graphite material;
(d) graphitizing the second precursor at a temperature of 3000 ℃ to 3500 ℃ to form a second graphite material; and
(e) mixing the first graphite material and the second graphite material to obtain the graphite.
According to an embodiment of the present application, in step (e), the first graphitic material and the second graphitic material are mixed in a weight ratio greater than or equal to 1: 1.
Additional aspects and advantages of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.
Drawings
Drawings necessary for describing embodiments of the present application or the prior art will be briefly described below in order to describe the embodiments of the present application. It is to be understood that the drawings in the following description are only some of the embodiments of the present application. It will be clear to a person skilled in the art that the drawings of other embodiments can still be obtained on the basis of the results illustrated in these drawings, without the need for inventive work.
Fig. 1 shows a discharge curve of the lithium ion battery of example 3 of the present application.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments described herein with respect to the figures are illustrative in nature, are diagrammatic in nature, and are used to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.
In the detailed description and claims, a list of items joined by the term "at least one of may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
With the wide application of electrochemical devices (hereinafter, taking lithium ion batteries as an example), the requirements for the performance of the electrochemical devices are higher and higher, especially for the quick-charging performance. However, lithium ion batteries are prone to lithium precipitation during rapid charging, which affects the safety of lithium ion batteries. The lithium deposition phenomenon generally occurs when the negative electrode charge potential becomes 0V or less. The surface coating of the negative active material is beneficial to improving the platform voltage of the negative electrode in the charging process, so that the charging potential of the negative electrode is not easy to reach below 0V under the same charging capacity, and the lithium separation phenomenon of the lithium ion battery is improved. But doing so can adversely affect other properties of the lithium ion battery (e.g., kinetic properties, energy density, etc.).
The present application solves the above-mentioned problems by providing graphite that exhibits a low voltage bounce ratio for charge and discharge testing through button cells. Voltage bounce generally occurs after the battery has terminated discharge. The "voltage bounce ratio" refers to a ratio of a voltage after bouncing under a discharge current to a termination voltage, which can embody properties of a tested material and can be an important parameter for characterizing overall performance of an electrochemical device. For example, when a lithium ion battery is charged, lithium ions generated at a positive electrode move to a negative electrode through an electrolyte, and the voltage of the lithium ion battery increases. When the lithium ion battery discharges, lithium ions in the negative electrode are removed and move back to the positive electrode through the electrolyte, and the voltage of the lithium ion battery is reduced. When the lithium ion battery stops discharging, part of the lithium ions can reversely move to the negative electrode, which causes the voltage bounce of the lithium ion battery (for example, the lithium ion battery in fig. 1 has two voltage bounces). The voltage bounce rate may be influenced by factors such as the lithium deposition in the electrochemical device, internal resistance, etc., which may be controlled by adjusting the properties of the active material in the electrode (e.g., the precursor of the negative electrode active material, the specific surface area, the median particle diameter, the graphitization degree, etc.).
Specifically, the present application provides an electrochemical device comprising a positive electrode, an electrolyte, and a negative electrode as described below.
Negative electrode
The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.
One feature of the negative electrode of the present application is that the negative electrode active material contains graphite, wherein a charge-discharge test is performed using a button cell that has lithium as a negative electrode and the graphite as a positive electrode, and the button cell has a voltage rebound ratio of 50 μ a discharge of not more than 13. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 12 for a 50 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 11 with a 50 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 10 for a 50 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 9 with a 50 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 8 for a 50 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 6 for a 50 μ Α discharge. When the voltage bounce rate for a button cell to discharge at 50 mua is within the above range using a particular graphite, the electrochemical device has balanced kinetic performance and energy density.
In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 6 for a 10 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 5 for a 10 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 4 for a 10 μ Α discharge. In some embodiments, the charge and discharge tests were performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, which had a voltage bounce ratio no greater than 3 for a 10 μ Α discharge. When specific graphite is used so that the voltage bounce rate for a button cell to discharge at 10 μ Α is within the above range, it helps to further balance the kinetic performance and energy density of the electrochemical device.
The button cell battery adopted by the application comprises the following components:
negative electrode: the lithium sheet serves as the negative electrode.
And (3) positive electrode: 94.5 wt% of graphite, 1.5 wt% of acetylene black, 1.5 wt% of sodium carboxymethylcellulose (CMC), and 2.5 wt% of Styrene Butadiene Rubber (SBR) as a positive electrode active material layer, and a copper foil as a current collector.
Electrolyte solution: 1mol/L LiPF6The solvent is Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) in a mass ratio of 1:1:1, and 1 wt% of Vinylene Carbonate (VC) is added.
The process of charging and discharging the button cell used in the application is as follows:
the button cells were discharged to 5.0mV at 0.05C (current value at 0.05 times the design gram capacity) and the voltage recorded as U0. After standing for 10 minutes, the button cells were discharged at 50. mu.A to 5.0mV, and the voltage was recorded as U1. After standing for 10 minutes, the button cells were discharged at 10. mu.A to 5.0mV, and the voltage was recorded as U2. The button cells were then charged to 2.0V at 0.1C. U1/U0 recorded the voltage bounce rate for a discharge at 50 μ A, and U2/U0 recorded the voltage bounce rate for a discharge at 10 μ A.
In some embodiments, the negative active material has a gram capacity of 340mAh to 375 mAh. In some embodiments, the negative active material has a gram capacity of 350mAh to 370 mAh. In some embodiments, the negative active material has a gram capacity of 360mAh to 365 mAh. In some embodiments, the negative active material has a gram capacity of 340mAh, 345mAh, 350mAh, 355mAh, 360mAh, 365mAh, 370mAh, 375mAh, or a range consisting of any two of the foregoing values. When the gram capacity of the negative active material is within the above range, the electrochemical device has balanced kinetic properties and energy density.
In some embodiments, the anode active material has a specific surface area of 1.2cm2G to 2.2cm2(ii) in terms of/g. In some embodiments, the anode active material has a specific surface area of 1.5cm2G to 2.0cm2(ii) in terms of/g. In some embodiments, the specific surface area of the negative active material is 1.6cm2G to 1.8cm2(ii) in terms of/g. In some embodiments, the anode active material has a specific surface area of 1.2cm2/g、1.4cm2/g、1.5cm2/g、1.8cm2/g、2.0cm2/g、2.2cm2In the range of/g or any two of the above values. When the specific surface area of the negative active material is within the above range, it helps to further balance the kinetic performance and energy density of the electrochemical device.
The specific surface area of the anode active material can be obtained by: the specific surface area of the negative active material is measured by a nitrogen adsorption/desorption method using a specific surface area analyzer (e.g., Tristar ii 3020M) after drying a sample of the negative active material in a vacuum drying oven and then loading the sample into a sample tube.
In some embodiments, the negative active material has a median particle diameter of 9.5 μm to 15 μm. In some embodiments, the negative active material has a median particle diameter of 10 μm to 14 μm. In some embodiments, the negative active material has a median particle diameter of 11 μm to 13 μm. In some embodiments, the negative active material has a median particle size of 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or within a range consisting of any two of the foregoing. The "median particle diameter (Dv 50)" refers to a particle diameter of the anode active material reaching 50% cumulative volume from the small particle diameter side in the particle size distribution on a volume basis, that is, the volume of the anode active material smaller than this particle diameter accounts for 50% of the total volume of the anode active material. When the median particle diameter of the negative active material is within the above range, it helps to further balance the kinetic performance and energy density of the electrochemical device.
The median particle diameter (Dv50) of the negative electrode active material may be measured by the following method: and dispersing a negative active material sample in a dispersing agent ethanol, carrying out ultrasonic treatment for 30 minutes, adding the sample into a Malvern particle size tester, and testing the Dv50 of the negative active material.
In some embodiments, the negative active material has a graphitization degree of 93% to 96% as measured by X-ray diffraction method. In some embodiments, the degree of graphitization of the negative active material by X-ray diffraction is 93%, 94%, 95%, 96%, or within a range consisting of any two of the foregoing values.
The "graphitization degree" refers to the degree to which non-graphite carbon is converted into graphite-like carbon at a high temperature or during secondary heating of the negative electrode active material containing graphite. The graphitization degree of the negative active material can be obtained by the following method: the high-purity silicon powder is used as an internal standard for calibration, the surface distance (d002) of the 002 surface of the negative active material is tested by an X-ray diffraction method, and the graphitization degree of the negative active material is calculated according to the following formula: the graphitization degree is (0.344-d002)/0.086 × 100%.
The degree of graphitization of the negative active material including graphite affects intercalation and deintercalation of lithium ions. For example, during cyclic discharge of a lithium ion battery, lithium ions migrate to the negative electrode, the negative electrode receives the lithium ions, and the graphitization degree of the negative electrode active material including graphite affects the rate at which the lithium ions are intercalated into the carbon material particles. Under the condition of high-rate discharge, if lithium ions cannot be rapidly inserted into and diffused in the carbon material particles, the lithium ions are precipitated on the surface, and the cycle decay of the lithium ion battery is accelerated. During the cyclic charging of a lithium ion battery, lithium ions are extracted from the negative electrode. If lithium ions cannot rapidly exit the negative electrode, they can form dead lithium inside the carbon material particles, which also accelerates the cycle decay of the lithium ion battery. The graphitization degree of the negative active material including graphite also affects the thickness of a Solid Electrolyte Interface (SEI) film formed during the first cycle of the lithium ion battery, thereby affecting the first efficiency and the like of the lithium ion battery. When the graphitization degree of the negative active material is within the above range, it helps to further balance the kinetic properties and energy density of the electrochemical device.
In some embodiments, a ratio C004/C110 of a peak area C004 of the (004) face and a peak area C110 of the (110) face of the negative electrode active material determined by X-ray diffraction spectrum is in a range of 2 to 6. In some embodiments, the negative active material has a C004/C110 in the range of 3 to 5 as determined by X-ray diffraction spectroscopy. In some embodiments, the negative active material has a C004/C110 of 2, 3, 4, 5, 6, or within a range consisting of any two of the foregoing values, as determined by X-ray diffraction spectroscopy.
In some embodiments, a ratio C004'/C110' of a peak area C004 'of a (004) face and a peak area C110' of a (110) face of the negative electrode measured by an X-ray diffraction spectrum is in a range of 9.2 to 15 when the electrochemical device is in a state of a voltage of 3.0V. In some embodiments, the cathode has a C004'/C110' in the range of 9.5 to 12 as determined by X-ray diffraction spectroscopy when the electrochemical device is under a voltage of 3.0V. In some embodiments, the negative electrode has a C004'/C110' in the range of 10 to 11 as determined by X-ray diffraction spectroscopy when the electrochemical device is under a voltage of 3.0V. In some embodiments, the negative electrode has a C004'/C110' of 9.2, 9.5, 10, 11, 12, 13, 14, 1 or a range consisting of any two of the foregoing values as determined by X-ray diffraction spectroscopy at a voltage of 3.0V for an electrochemical device.
The anisotropy of the material can be reflected by the ratio of the peak area of the (004) surface and the peak area of the (110) surface of the material determined by an X-ray diffraction spectrum. The smaller the ratio, the smaller the anisotropy. When C004/C110 of the anode active material and C004'/C110' of the anode are in the above range, it helps to balance the lithium precipitation phenomenon and rate capability of the electrochemical device.
In some embodiments, the negative active material includes crystal grains, and a crystal grain size La of the crystal grains in a horizontal direction is 150nm to 160nm and a crystal grain size Lc of the crystal grains in a vertical direction is 33nm to 35nm by an X-ray diffraction method. The negative active material having the above-described grain size contributes to further improvement in overall performance of the electrochemical device.
In some embodiments, the thermal weight loss temperature of the anode active material is 850 ℃ to 930 ℃. In some embodiments, the thermal weight loss temperature of the anode active material is 880 ℃ to 900 ℃. When the thermal weight loss temperature of the negative active material is within the above range, the electrochemical device has balanced kinetic properties and energy density.
In some embodiments, an area of the negative active material having an orientation degree of 20 ° to 70 ° accounts for 50% to 62% of a total area of the negative active material when the electrochemical device is in a 3.0V voltage state, as measured by a polarization microscope. In some embodiments, an area of the negative active material having an orientation degree of 20 ° to 70 ° accounts for 55% to 60% of a total area of the negative active material when the electrochemical device is in a 3.0V voltage state, as measured by a polarization microscope. When the area of the anode active material having the degree of orientation of 20 ° to 70 ° is within the above range, it helps to further balance the kinetic performance and energy density of the electrochemical device.
In some embodiments, the negative active material layer has a resistivity of 0.001 Ω · m to 0.1 Ω · m. In some embodiments, the negative electrode active material layer has a resistivity of 0.005 Ω · m to 0.05 Ω · m. In some embodiments, the negative electrode active material layer has a resistivity of 0.01 Ω · m to 0.03 Ω · m. The resistivity of the negative active material layer can be determined by a two-probe sheet resistance test method. When the resistivity of the anode active material layer is within the above range, the electrochemical device has a rate capability and a lithium precipitation phenomenon that balance the electrochemical device.
In some embodiments, the thickness of the negative active material layer is in a range of 0.08mm to 0.15 mm. In some embodiments, the thickness of the anode active material layer is in a range of 0.1mm to 0.12 mm.
In some embodiments, the compacted density of the negative active material layer is at 1.60g/cm3To 1.80g/cm3Within the range of (1). In some embodiments, the compacted density of the negative active material layer is at 1.65g/cm3To 1.75g/cm3Within the range of (1). In some embodiments, the compacted density of the negative active material layer is at 1.65g/cm3To 1.70g/cm3Within the range of (1).
In some embodiments, the negative electrode current collector used in the present application may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.
In some embodiments, the negative electrode further comprises a negative electrode conductive layer. The conductive material of the negative electrode conductive layer may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of the negative electrode conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
In some embodiments, the anode further comprises an anode binder. Non-limiting, illustrative examples of the negative electrode binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like.
The negative electrode of the present application may be manufactured by any method known in the art. In some embodiments, the negative electrode may be formed by adding a binder and a solvent to a negative electrode active material and adding a thickener, a conductive material, a filler material, and the like as needed to prepare a slurry, coating the slurry on a current collector, drying, and then pressing. When the anode includes an alloy material, the anode active material layer may be formed using a vapor deposition method, a sputtering method, a plating method, or the like.
The present application also provides a method of preparing graphite in an electrochemical device according to the present application, the method comprising the steps of:
(a) mixing the first precursor with a binder to form secondary particles;
(b) graphitizing the secondary particles at a temperature of from 3000 ℃ to 3500 ℃ to form a graphitized product;
(c) coating the graphitized product with pitch to form a first graphite material;
(d) graphitizing the second precursor at a temperature of 3000 ℃ to 3500 ℃ to form a second graphite material; and
(e) mixing the first graphite material and the second graphite material to obtain the graphite.
In the above steps, the preparation order of the first graphite material and the second graphite material may be interchanged.
In some embodiments, the first precursor comprises post-forging coke.
In some embodiments, the second precursor comprises green coke.
In some embodiments, the first graphitic material and the second graphitic material are mixed in a weight ratio greater than or equal to 1: 1.
Positive electrode
The positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector. The specific kind of the positive electrode active material is not particularly limited and may be selected as desired.
In some embodiments, the positive active material includes a compound that reversibly intercalates and deintercalates lithium ions. In some embodiments, the positive active material may include a composite oxide containing lithium and at least one element selected from cobalt, manganese, and nickel. In still other embodiments, the positive active material is selected from lithium cobaltate (LiCoO)2) Lithium nickel manganese cobalt ternary material and lithium manganate (LiMn)2O4) Lithium nickel manganese oxide (LiNi)0.5Mn1.5O4) Lithium iron phosphate (LiFePO)4) One or more of them.
In some embodiments, the positive electrode active material layer may have a coating layer on the surface, or may be mixed with another compound having a coating layer. The coating may include at least one coating element compound selected from an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate (oxycarbonate) of the coating element, and an oxycarbonate (hydroxycarbonate) of the coating element. The compounds used for the coating may be amorphous or crystalline. The coating element contained in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or a mixture thereof. The coating layer may be applied by any method as long as the method does not adversely affect the properties of the positive electrode active material. For example, the method may include any coating method well known to those of ordinary skill in the art, such as spraying, dipping, and the like.
In some embodiments, the positive active material layer further comprises a positive binder. The positive electrode binder may improve the binding of the positive electrode active material particles to each other and also improve the binding of the positive electrode active material to the current collector. Non-limiting examples of the positive electrode binder include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.
In some embodiments, the positive active material layer includes a positive conductive material, thereby imparting conductivity to the electrode. The positive electrode conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of the positive electrode conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
The positive electrode current collector for the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
Electrolyte solution
The electrolyte that may be used in the embodiments of the present application may be an electrolyte known in the art. Electrolytes that may be used in the electrolytes of embodiments of the present application include, but are not limited to: inorganic lithium salts, e.g. LiClO4、LiPF6、LiBF4、LiSbF6、LiSO3F、LiN(FSO2)2Etc.; organic lithium salts containing fluorine, e.g. LiCF3SO3、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic 1, 3-hexafluoropropane disulfonimide lithium, cyclic 1, 2-tetrafluoroethane disulfonimide lithium, LiN (CF)3SO2)(C4F9SO2)、LiC(CF3SO2)3、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2(ii) a The dicarboxylic acid complex-containing lithium salt may, for example, be lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, or the like. The electrolyte may be used alone or in combination of two or more. For example, in some embodiments, the electrolyte comprises LiPF6And LiBF4Combinations of (a) and (b). In some embodiments, the electrolyte comprises LiPF6Or LiBF4An inorganic lithium salt and LiCF3SO3、LiN(CF3SO2)2、LiN(C2F5SO2)2And the like, a combination of fluorine-containing organic lithium salts.
In some embodiments, the concentration of the electrolyte is in the range of 0.8 to 3mol/L, such as in the range of 0.8 to 2.5mol/L, in the range of 0.8 to 2mol/L, in the range of 1 to 2mol/L, again, for example, 1, 1.15, 1.2, 1.5, 2, or 2.5 mol/L.
Solvents that may be used in the electrolytes of embodiments of the present application include, but are not limited to: a carbonate compound, an ester-based compound, an ether-based compound, a ketone-based compound, an alcohol-based compound, an aprotic solvent, or a combination thereof.
Examples of the carbonate compound include, but are not limited to, a chain carbonate compound, a cyclic carbonate compound, a fluoro carbonate compound, or a combination thereof.
Examples of the chain carbonate compound include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Methyl Ethyl Carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC), Vinyl Ethylene Carbonate (VEC), and combinations thereof. Examples of the fluoro carbonate compound are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1,2, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
Examples of ester-based compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, γ -butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, methyl formate, and combinations thereof.
Examples of ether-based compounds include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
Examples of ketone-based compounds include, but are not limited to, cyclohexanone.
Examples of alcohol-based compounds include, but are not limited to, ethanol and isopropanol.
Examples of aprotic solvents include, but are not limited to, dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
Isolation film
In some embodiments, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separation film that can be used for the embodiment of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.
For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. The porous structure can improve the heat resistance, the oxidation resistance and the electrolyte infiltration performance of the isolating membrane and enhance the adhesion between the isolating membrane and the pole piece.
At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer comprises inorganic particles and a binder, wherein the inorganic particles comprise one or more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder comprises polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and/or polyhexafluoropropylene.
The polymer layer comprises a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
Applications of
The electrochemical device of the present application includes any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries or secondary electricity. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
The present application further provides an electronic device comprising an electrochemical device according to the present application.
The use of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the art. In some embodiments, the electrochemical device of the present application can be used in, but is not limited to, a mobile phone, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flashlight, a camera, or a large household battery, and the like.
Taking a lithium ion battery as an example and describing the preparation of the lithium ion battery with reference to specific examples, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.
Examples
The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application.
Preparation of lithium ion battery
1. Preparation of the negative electrode
Preparing graphite:
selecting a precursor A and a precursor B, wherein A is forged coke, B is green coke, bonding the precursor A with a binder (the binder is 8-20 wt%) to obtain secondary particles, graphitizing at 3500 ℃ in 3000-fold manner to obtain a graphitized product A1, coating and carbonizing the A1 with asphalt, the addition of the asphalt is 1-10 wt%, and the carbonization temperature is set to 1500-fold manner to obtain a first graphite material A2.
And (3) directly graphitizing the precursor B at 3000-3500 ℃ to obtain a second graphite material B1, and finally mixing the first graphite material A2 and the second graphite material B1 for use, wherein the weight mixing ratio of the first graphite material A2 to the second graphite material B1 is greater than or equal to 1: 1.
The parameters of graphite can be controlled by controlling the type of graphite precursor, the proportion of different precursors, the particle size of the precursor or the sintering temperature.
The prepared graphite negative electrode active material, Styrene Butadiene Rubber (SBR) and sodium carboxymethyl cellulose (CMC) are dispersed in deionized water according to the weight ratio of 97.7:1.2:1.1, and are fully stirred and uniformly mixed to obtain negative electrode slurry. And coating the negative electrode slurry on a negative electrode current collector, drying, cold-pressing to form a negative electrode active material layer, cutting pieces, and welding tabs to obtain a negative electrode.
2. Preparation of the Positive electrode
Mixing lithium cobaltate (LiCoO)2) The preparation method comprises the following steps of fully stirring and uniformly mixing acetylene black and polyvinylidene fluoride (PVDF) in a proper amount of N-methyl pyrrolidone (NMP) according to a weight ratio of 96:2:2, coating the mixture on an aluminum foil of a positive electrode current collector, drying, cold-pressing to form a positive electrode active material layer, cutting the positive electrode active material layer, and welding a tab to obtain the positive electrode.
3. Preparation of the electrolyte
Ethylene Carbonate (EC), Propylene Carbonate (PC) and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1 under a dry argon atmosphere, and LiPF was added6And (4) uniformly mixing. Adding 3% of fluoroethylene carbonate and 2% of 1, 3-propane sultone, and uniformly mixing to obtain electrolyte, wherein LiPF6The concentration of (2) is 1.15 mol/L.
4. Preparation of the separator
A Polyethylene (PE) porous polymer film having a thickness of 12 μm was used as a separator.
5. Preparation of lithium ion battery
And sequentially stacking the anode, the isolating film and the cathode to enable the isolating film to be positioned between the anode and the cathode to play an isolating role, then winding the battery, welding a tab, placing the battery into an outer packaging foil aluminum plastic film, injecting the prepared electrolyte, and carrying out vacuum packaging, standing, formation, shaping, capacity test and other procedures to obtain the lithium ion battery.
Second, testing method
1. Method for testing voltage rebound proportion
The button cells were discharged to 5.0mV at 0.05C (current value at 0.05 times the design gram capacity) and the voltage recorded as U0. After standing for 10 minutes, the button cells were discharged at 50. mu.A to 5.0mV, and the voltage was recorded as U1. After standing for 10 minutes, the button cells were discharged at 10. mu.A to 5.0mV, and the voltage was recorded as U2. The button cells were then charged to 2.0V at 0.1C. U1/U0 recorded the voltage bounce rate for a discharge at 50 μ A, and U2/U0 recorded the voltage bounce rate for a discharge at 10 μ A.
The graphite in the button cell can also be obtained by discharging the electrochemical device to 3.0V, taking a proper amount of negative active material layer, and calcining the negative active material layer in a muffle furnace at the temperature of 400 ℃ for 2 hours.
2. Method for testing particle size of negative electrode active material
The particle diameter of the negative electrode active material was measured using a malvern particle size tester: and dispersing a negative active material sample in a dispersing agent ethanol, carrying out ultrasonic treatment for 30 minutes, adding the sample into a Malvern particle size tester, and testing the Dv50 of the negative active material.
3. Method for testing specific surface area of negative electrode active material
The specific surface area of the negative electrode active material was measured by a nitrogen adsorption/desorption method using a specific surface area analyzer (Tristar ii 3020M): the negative active material sample was dried in a vacuum drying oven, and then filled in a sample tube to be measured in an analyzer.
4. Method for testing graphitization degree of negative electrode active material
High-purity silicon powder (the purity is more than or equal to 99.99%) is used as an internal standard for calibration, and the method comprises the following steps of: silicon-5: 1, grinding uniformly, tabletting and preparing a sample. The surface-to-surface distance (d002) of the 002 face of the negative active material was measured using an X-ray diffractometer (Cu K α target), and the graphitization degree of the carbon material was calculated by the following formula:
the graphitization degree is (0.344-d002)/0.086 × 100%.
5. Method for testing resistivity of negative electrode
And placing the negative electrode between two probes in a two-probe Diaphragm Resistance Meter (DRM) V1.0, continuously moving the position of the negative electrode, and testing the resistivity of the negative electrode.
6. X-ray diffraction pattern testing method
And (004) surface diffraction line patterns and (110) surface diffraction line patterns in the X-ray diffraction spectrum of the negative active material or the negative electrode are tested according to the standard JB/T4220 and 2011 < method for measuring lattice parameters of artificial graphite > in the mechanical industry of the people's republic of China. The test conditions were as follows: the X-rays are CuK α radiation, which is removed by a filter or monochromator. The working voltage of the X-ray tube is (30-35) kV, and the working current is (15-20) mA. The scanning speed of the counter was 1/4(°)/min. The diffraction angle 2 theta was scanned over a range of 53 deg. -57 deg. when recording 004 the diffraction line pattern. The diffraction angle 2 theta was scanned over 75 deg. -79 deg. while recording a 110 diffraction pattern. The peak area obtained from the (004) plane diffraction pattern was designated as C004 or C004'. The peak area obtained from the (110) plane diffraction pattern was designated as C110 or C110'. The ratio of C004/C110 of the negative electrode active material and the ratio of C004'/C110' of the negative electrode were calculated.
7. Method for testing gram capacity of lithium ion battery
The lithium ion cell was discharged to 5.0mV at 0.05C, 5.0mV at 50 μ A, 5.0mV at 10 μ A, and 2.0V at 0.1C, and the capacity of the lithium ion cell at this time was recorded as gram capacity. 0.05C means a current value at 0.05 times the design gram capacity, and 0.1C means a current value at 0.1 times the design gram capacity.
8. Method for testing first efficiency of lithium ion battery
The lithium ion battery was charged to 4.45V at 0.5C, the first charge capacity C was recorded, and then discharged to 3.0V at 0.5C, and its discharge capacity D was recorded. The first efficiency CE of the lithium ion battery was calculated by:
CE＝D/C。
9. method for testing Direct Current Resistance (DCR) of lithium ion battery
At 25 ℃, the lithium ion battery was charged to 4.45V at a constant current of 1.5C, then charged to 0.05C at a constant voltage of 4.45V, and left to stand for 30 minutes. The voltage value was recorded as U by discharging at 0.1C for 10 seconds, and U' by discharging at 1C for 360 seconds. The charging and discharging steps were repeated 5 times. "1C" is a current value at which the capacity of the lithium ion battery is completely discharged within 1 hour.
The dc resistance R of the lithium ion battery at 25 ℃ was calculated by the following formula:
R＝(U'-U)/(1C-0.1C)。
unless otherwise specified, DCR as used herein refers to the direct current resistance of a lithium ion battery at 50% state of charge (SOC).
10. Method for judging lithium analysis condition of lithium ion battery
The lithium ion battery was discharged to 3.0V at 0.5C, charged to 4.45V at 1.5C, and then charged to 0.025C at a constant voltage. And repeating the same steps for 12 circles of charging and discharging, then charging the lithium ion battery to 4.45V, disassembling the lithium ion battery under a dry condition, and taking a picture to record the state of the negative electrode.
Judging the lithium separation degree of the lithium ion battery according to the following standards:
when the whole disassembled negative electrode is golden yellow, a few parts can be observed in gray; and the area of the gray region is less than 2%, it is judged that lithium is not precipitated.
When most of the disassembled negative electrode is golden yellow, gray can be observed at partial positions; and the area of the gray region is between 2% and 20%, it is judged to be slightly lithium-precipitated.
When the whole disassembled cathode is gray, golden yellow can be observed at partial positions; and the area of the gray region is between 20% and 60%, then it is judged to be lithium deposition.
When the disassembled negative electrode is gray overall and the area of the gray area is larger than 60%, the lithium is judged to be seriously separated.
11. Method for testing charging rate performance of lithium ion battery
The lithium ion battery is charged to 4.45V by a current constant current of 1.5C multiplying power, the capacity at the moment is recorded as a CC value, then the lithium ion battery is charged to 0.05C by a constant voltage of 4.45V, and the capacity at the moment is recorded as a CV value. The value of CC/(CC + CV) × 100% at 1.5C magnification of the lithium ion battery was calculated.
Third, test results
Table 1 shows the effect of the voltage bounce ratio and the properties of the negative active material on the first efficiency and direct current internal resistance (DCR) of the lithium ion battery.
TABLE 1
The results show that the properties of the negative active material affect the voltage bounce ratio of the button cell test (U1/U0 and U2/U0). When the specific surface area, the median diameter (Dv50) and the graphitization degree of the negative electrode active material are adjusted so that the ratio of U1/U0 (i.e., the voltage rebound ratio of a button cell discharging at 50 μ a in a charge-discharge test using a button cell with lithium as a negative electrode and graphite as a positive electrode) is not more than 13, the lithium ion battery has balanced primary efficiency and direct current internal resistance.
Specifically, as shown in comparative examples 1 and 2, U1/U0 is larger than 13, and although the first efficiency is higher, the direct current internal resistance is too high, the dynamic performance of the lithium ion battery is too poor, the comprehensive performance is not good, and the practical application prospect is not good.
As shown in examples 1 to 18, in the case where the median particle diameter (Dv50) and the graphitization degree of the anode active material were maintained, the voltage rebound ratios (U1/U0 and U2/U0) were decreased as the specific surface area (BET) of the anode active material was increased. Under the condition, the deintercalation channel of lithium ions is increased, the Solid Electrolyte Interface (SEI) film forming area between the negative electrode and the electrolyte is increased, the gram capacity and the thermal weight loss temperature of the negative electrode active material are reduced, the first efficiency of the lithium ion battery is reduced, and the energy density is reduced; and meanwhile, the direct current internal resistance is obviously reduced, so that the dynamic performance is obviously improved. Overall, lithium ion batteries achieve a balance of energy density and kinetic performance.
When the specific surface area of the negative electrode active material is changed to make U2/U0 less than or equal to 6, the energy density and the dynamic performance of the lithium ion battery can be further balanced.
When the specific surface area of the negative electrode active material was 1.2g/cm3To 2.2g/cm3Within the ranges of (a), helps to further balance the energy density and kinetic performance of the lithium ion battery.
In the case where the specific surface area (BET) and the graphitization degree of the negative electrode active material were kept constant, the voltage rebound ratio (U1/U0 and U2/U0) decreased as the median particle diameter (Dv50) of the negative electrode active material decreased. The reduction of the size of the negative active material can shorten the transmission path of lithium ions between the negative active material layers, thereby reducing the direct current internal resistance of the lithium ion battery and improving the dynamic performance of the lithium ion battery, but the gram capacity and the thermal weight loss temperature of the negative active material are reduced, the first efficiency of the lithium ion battery is reduced, and the energy density is reduced. Overall, lithium ion batteries have balanced energy density and kinetic properties. When the median particle diameter of the negative active material is 9.5 μm to 15 μm, it helps to further balance the energy density and the kinetic properties of the lithium ion battery.
Under the condition that the specific surface area (BET) and the median particle diameter (Dv50) of the negative electrode active material are kept unchanged, the voltage rebound ratio (U1/U0 and U2/U0) is reduced along with the reduction of the graphitization degree of the negative electrode active material, so that the direct current internal resistance of the lithium ion battery is reduced, the dynamic performance is improved, but the gram capacity and the thermal weight loss temperature of the negative electrode active material are reduced, the first efficiency of the lithium ion battery is reduced, and the energy density is reduced. Overall, lithium ion batteries have balanced energy density and kinetic properties.
When the graphitization degree of the negative active material is 93% to 96%, it helps to further balance the energy density and kinetic properties of the lithium ion battery.
Table 2 shows the influence of the structure and properties of the negative electrode on the lithium deposition condition and rate performance of the lithium ion battery, in which the parameter a represents the ratio of the area of the negative electrode active material having a degree of orientation of 20 ° to 70 ° to the total area of the negative electrode active material. Examples 19-37 differ from example 11 only in the parameters listed in table 2.
TABLE 2
The results indicate that the orientation degrees of the anode active material and the anode (C004/C110 and C004'/C110') are mainly related to the compacted density of the anode active material layer, which is not substantially affected by the thickness variation of the anode active material layer. The resistivity of the negative electrode may be affected by the thickness and the compaction density of the negative electrode active material layer.
When the thickness of the anode active material layer is kept constant, the resistivity of the anode slightly increases and a lithium deposition phenomenon is liable to occur as the compacted density of the anode active material layer decreases. Meanwhile, the C004/C110 of the negative electrode active material and the C004'/C110' of the negative electrode are reduced, the anisotropy of the negative electrode active material layer and the negative electrode is reduced, the porosity of the negative electrode active material layer is increased, so that the electrolyte is easy to infiltrate into the negative electrode, the contact area of the electrolyte and the negative electrode active material is increased, the diffusion of lithium ions is facilitated, and the charge rate performance of the lithium ion battery can be improved. Overall, lithium ion batteries have a balanced primary efficiency, rate capability, and lithium evolution. When the C004/C110 of the anode active material is in the range of 2 to 6 and/or the C004'/C110' of the anode is in the range of 9.2 to 15, it helps to further balance the first efficiency, rate capability and lithium evolution phenomenon of the lithium ion battery.
When the electrochemical device is tested by a polarization microscope in a voltage state of 3.0V, the area of the negative active material having an orientation degree of 20 ° to 70 ° accounts for 50% to 62% of the total area of the negative active material, contributing to further balancing the first efficiency, rate capability and lithium precipitation phenomenon of the lithium ion battery.
Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that at least one embodiment or example in this application includes a particular feature, structure, material, or characteristic described in the embodiment or example. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.
Claims (15)
1. An electrochemical device comprising a negative electrode including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material comprising graphite, wherein:
and performing charge and discharge tests by using the button cell which takes lithium as a negative electrode and the graphite as a positive electrode, wherein the voltage rebound ratio of the button cell discharging at 50 muA is not more than 13.
2. The electrochemical device of claim 1, wherein a charge-discharge test is performed using a button cell with lithium as the negative electrode and the graphite as the positive electrode, the button cell having a voltage bounce ratio of no greater than 6 at 10 μ Α discharge.
3. The electrochemical device according to claim 1, wherein the gram capacity of the negative active material is 340mAh to 375 mAh.
4. The electrochemical device according to claim 1, wherein the specific surface area of the negative electrode active material is 1.2cm2G to 2.2cm2/g。
5. The electrochemical device according to claim 1, wherein the negative active material has a median particle diameter of 9.5 μm to 15 μm.
6. The electrochemical device according to claim 1, wherein the degree of graphitization of the negative active material by X-ray diffraction method test is 93% to 96%.
7. The electrochemical device according to claim 1, wherein a ratio C004/C110 of a peak area C004 of a (004) face and a peak area C110 of a (110) face of the negative electrode active material determined by X-ray diffraction spectrum is in a range of 2 to 6.
8. The electrochemical device according to claim 1, wherein the negative active material includes crystal grains, and a crystal grain size La of the crystal grains in a horizontal direction is 150nm to 160nm and a crystal grain size Lc of the crystal grains in a vertical direction is 33nm to 35nm by an X-ray diffraction method.
9. The electrochemical device according to claim 1, wherein the thermal weight loss temperature of the negative active material is 850 ℃ to 930 ℃.
10. The electrochemical device according to claim 1, wherein a ratio C004'/C110' of a peak area C004 'of a (004) face and a peak area C110' of a (110) face of the negative electrode measured by an X-ray diffraction spectrum is in a range of 9.2 to 15 when the electrochemical device is in a state of a voltage of 3.0V.
11. The electrochemical device according to claim 1, wherein an area of the negative active material having an orientation degree of 20 ° to 70 ° accounts for 50% to 62% of a total area of the negative active material when the electrochemical device is in a 3.0V voltage state, as measured by a polarization microscope.
12. The electrochemical device according to claim 1, wherein the negative electrode active material layer has a resistivity of 0.001 Ω -m to 0.1 Ω -m.
13. An electronic device comprising the electrochemical device of any one of claims 1 to 12.
14. A method of making graphite in the electrochemical device of claim 1, the method comprising:
(a) mixing the first precursor with a binder to form secondary particles;
(b) graphitizing the secondary particles at a temperature of from 3000 ℃ to 3500 ℃ to form a graphitized product;
(c) coating the graphitized product with pitch to form a first graphite material;
(d) graphitizing the second precursor at a temperature of 3000 ℃ to 3500 ℃ to form a second graphite material; and
(e) mixing the first graphite material and the second graphite material to obtain the graphite.
15. The method of claim 14, wherein in step (e), the first graphitic material and the second graphitic material are mixed in a weight ratio greater than or equal to 1: 1.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111464641.9A CN114156472B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202111464968.6A CN114171739B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202011331981.XA CN112421031B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011331981.XA CN112421031B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
Related Child Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111464968.6A Division CN114171739B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202111464641.9A Division CN114156472B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112421031A true CN112421031A (en) | 2021-02-26 |
| CN112421031B CN112421031B (en) | 2022-04-05 |
Family
ID=74778763
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011331981.XA Active CN112421031B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202111464968.6A Active CN114171739B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202111464641.9A Active CN114156472B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
Family Applications After (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111464968.6A Active CN114171739B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
| CN202111464641.9A Active CN114156472B (en) | 2020-11-24 | 2020-11-24 | Electrochemical device and electronic device |
Country Status (1)
| Country | Link |
|---|---|
| CN (3) | CN112421031B (en) |
Citations (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101533935A (en) * | 2009-04-14 | 2009-09-16 | 黄穗阳 | A high-energy safe rechargeable lithium-oxygen battery |
| CN102544510A (en) * | 2011-12-31 | 2012-07-04 | 陈骏 | Graphite compound modification method and lithium ion battery anode material preparation method |
| CN102723539A (en) * | 2012-05-04 | 2012-10-10 | 赵军辉 | Lithium-oxygen battery capable of improving battery energy density and method for manufacturing lithium-oxygen battery |
| CN103457002A (en) * | 2012-05-28 | 2013-12-18 | 广州丰江电池新技术股份有限公司 | Lithium ion battery storage or transportation method |
| CN103682350A (en) * | 2013-12-25 | 2014-03-26 | 东莞市凯金新能源科技有限公司 | Preparation method of asphalt liquid phase coated modified artificial graphite lithium battery cathode material |
| CN104319418A (en) * | 2014-10-24 | 2015-01-28 | 东莞锂威能源科技有限公司 | High capacity lithium ion battery |
| CN104659366A (en) * | 2014-12-30 | 2015-05-27 | 东莞市凯金新能源科技有限公司 | Preparation method of anode material for power lithium ion battery |
| CN106384853A (en) * | 2016-11-24 | 2017-02-08 | 山东精工电子科技有限公司 | Lithium ion battery stepped formation and consistency screening method |
| CN108539299A (en) * | 2018-04-11 | 2018-09-14 | 广东力科新能源有限公司 | A kind of multi-series and parallel Li-ion batteries piles dynamic low voltage method for group matching and system |
| CN108807995A (en) * | 2018-08-03 | 2018-11-13 | 安徽科达洁能新材料有限公司 | A kind of lithium ion battery graphite cathode material and preparation method thereof |
| CN108872859A (en) * | 2017-05-16 | 2018-11-23 | 宁德时代新能源科技股份有限公司 | Detection method for battery lithium separation, battery management system and battery system |
| CN109768217A (en) * | 2018-12-19 | 2019-05-17 | 深圳市金润能源材料有限公司 | Graphite material and preparation method thereof, cathode and lithium ion battery |
| CN110642247A (en) * | 2019-09-30 | 2020-01-03 | 广东凯金新能源科技股份有限公司 | Artificial graphite negative electrode material, preparation method thereof and lithium ion battery |
| CN111029543A (en) * | 2019-11-28 | 2020-04-17 | 宁德新能源科技有限公司 | Negative electrode material, and electrochemical device and electronic device comprising same |
| CN111029527A (en) * | 2019-12-11 | 2020-04-17 | 宁德新能源科技有限公司 | Negative electrode, and electrochemical device and electronic device including the same |
| CN111204756A (en) * | 2020-02-27 | 2020-05-29 | 深圳市翔丰华科技股份有限公司 | Quick-charging graphite negative electrode material and preparation method thereof |
| CN111354944A (en) * | 2020-03-20 | 2020-06-30 | 宁德新能源科技有限公司 | Negative electrode active material, and electrochemical device and electronic device using same |
| CN111370695A (en) * | 2020-03-20 | 2020-07-03 | 宁德新能源科技有限公司 | Negative electrode active material, and electrochemical device and electronic device using same |
| CN111384395A (en) * | 2020-03-20 | 2020-07-07 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
| CN111525194A (en) * | 2020-04-28 | 2020-08-11 | 宁德新能源科技有限公司 | Electrochemical device and electronic device including the same |
| CN111834634A (en) * | 2020-07-07 | 2020-10-27 | 鞍钢化学科技有限公司 | High-performance artificial graphite negative electrode material and production process thereof |
| CN111825088A (en) * | 2020-07-07 | 2020-10-27 | 鞍钢化学科技有限公司 | Preparation method of artificial graphite material special for lithium ion battery cathode |
| CN111864859A (en) * | 2020-08-12 | 2020-10-30 | 优动能科技(深圳)有限公司 | System and method for prolonging service life of lithium battery pack with constant-current and constant-voltage charging and discharging |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU6535998A (en) * | 1997-02-26 | 1998-09-18 | Columbian Chemicals Company | Use of thermal carbon black as anode material for lithium-ion batteries |
| JP4252846B2 (en) * | 2002-07-31 | 2009-04-08 | パナソニック株式会社 | Lithium secondary battery |
| US8647436B2 (en) * | 2008-04-02 | 2014-02-11 | Raytheon Company | Carbon ion beam growth of isotopically-enriched graphene and isotope-junctions |
| JP6121645B2 (en) * | 2010-09-16 | 2017-04-26 | 三菱化学株式会社 | Negative electrode material for non-aqueous electrolyte secondary battery, negative electrode using the same, and non-aqueous electrolyte secondary battery |
| CN207834509U (en) * | 2018-02-08 | 2018-09-07 | 合肥国轩高科动力能源有限公司 | A kind of electric discharge device for discarding ternary lithium battery |
| CN108383116A (en) * | 2018-02-11 | 2018-08-10 | 珠海光宇电池有限公司 | Artificial plumbago negative pole material and preparation method thereof and negative electrode of lithium ion battery |
| CN111792640B (en) * | 2020-07-31 | 2022-05-06 | 广东凯金新能源科技股份有限公司 | Spheroidal low-expansion high-capacity graphite negative electrode material, preparation method and lithium ion battery |
-
2020
- 2020-11-24 CN CN202011331981.XA patent/CN112421031B/en active Active
- 2020-11-24 CN CN202111464968.6A patent/CN114171739B/en active Active
- 2020-11-24 CN CN202111464641.9A patent/CN114156472B/en active Active
Patent Citations (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101533935A (en) * | 2009-04-14 | 2009-09-16 | 黄穗阳 | A high-energy safe rechargeable lithium-oxygen battery |
| CN102544510A (en) * | 2011-12-31 | 2012-07-04 | 陈骏 | Graphite compound modification method and lithium ion battery anode material preparation method |
| CN102723539A (en) * | 2012-05-04 | 2012-10-10 | 赵军辉 | Lithium-oxygen battery capable of improving battery energy density and method for manufacturing lithium-oxygen battery |
| CN103457002A (en) * | 2012-05-28 | 2013-12-18 | 广州丰江电池新技术股份有限公司 | Lithium ion battery storage or transportation method |
| CN103682350A (en) * | 2013-12-25 | 2014-03-26 | 东莞市凯金新能源科技有限公司 | Preparation method of asphalt liquid phase coated modified artificial graphite lithium battery cathode material |
| CN104319418A (en) * | 2014-10-24 | 2015-01-28 | 东莞锂威能源科技有限公司 | High capacity lithium ion battery |
| CN104659366A (en) * | 2014-12-30 | 2015-05-27 | 东莞市凯金新能源科技有限公司 | Preparation method of anode material for power lithium ion battery |
| CN106384853A (en) * | 2016-11-24 | 2017-02-08 | 山东精工电子科技有限公司 | Lithium ion battery stepped formation and consistency screening method |
| CN108872859A (en) * | 2017-05-16 | 2018-11-23 | 宁德时代新能源科技股份有限公司 | Detection method for battery lithium separation, battery management system and battery system |
| CN108539299A (en) * | 2018-04-11 | 2018-09-14 | 广东力科新能源有限公司 | A kind of multi-series and parallel Li-ion batteries piles dynamic low voltage method for group matching and system |
| CN108807995A (en) * | 2018-08-03 | 2018-11-13 | 安徽科达洁能新材料有限公司 | A kind of lithium ion battery graphite cathode material and preparation method thereof |
| CN109768217A (en) * | 2018-12-19 | 2019-05-17 | 深圳市金润能源材料有限公司 | Graphite material and preparation method thereof, cathode and lithium ion battery |
| CN110642247A (en) * | 2019-09-30 | 2020-01-03 | 广东凯金新能源科技股份有限公司 | Artificial graphite negative electrode material, preparation method thereof and lithium ion battery |
| CN111029543A (en) * | 2019-11-28 | 2020-04-17 | 宁德新能源科技有限公司 | Negative electrode material, and electrochemical device and electronic device comprising same |
| CN111029527A (en) * | 2019-12-11 | 2020-04-17 | 宁德新能源科技有限公司 | Negative electrode, and electrochemical device and electronic device including the same |
| CN111204756A (en) * | 2020-02-27 | 2020-05-29 | 深圳市翔丰华科技股份有限公司 | Quick-charging graphite negative electrode material and preparation method thereof |
| CN111354944A (en) * | 2020-03-20 | 2020-06-30 | 宁德新能源科技有限公司 | Negative electrode active material, and electrochemical device and electronic device using same |
| CN111370695A (en) * | 2020-03-20 | 2020-07-03 | 宁德新能源科技有限公司 | Negative electrode active material, and electrochemical device and electronic device using same |
| CN111384395A (en) * | 2020-03-20 | 2020-07-07 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
| CN111525194A (en) * | 2020-04-28 | 2020-08-11 | 宁德新能源科技有限公司 | Electrochemical device and electronic device including the same |
| CN111834634A (en) * | 2020-07-07 | 2020-10-27 | 鞍钢化学科技有限公司 | High-performance artificial graphite negative electrode material and production process thereof |
| CN111825088A (en) * | 2020-07-07 | 2020-10-27 | 鞍钢化学科技有限公司 | Preparation method of artificial graphite material special for lithium ion battery cathode |
| CN111864859A (en) * | 2020-08-12 | 2020-10-30 | 优动能科技(深圳)有限公司 | System and method for prolonging service life of lithium battery pack with constant-current and constant-voltage charging and discharging |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112421031B (en) | 2022-04-05 |
| CN114171739A (en) | 2022-03-11 |
| CN114156472A (en) | 2022-03-08 |
| CN114171739B (en) | 2023-08-01 |
| CN114156472B (en) | 2023-07-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP7280942B2 (en) | Negative electrode materials and negative electrodes containing said negative electrode materials, and electrochemical devices | |
| CN111354944B (en) | Negative electrode active material, and electrochemical device and electronic device using same | |
| CN111029543B (en) | Negative electrode material, and electrochemical device and electronic device comprising same | |
| CN111082129B (en) | Electrochemical device and electronic device | |
| CN111384395B (en) | Electrochemical device and electronic device | |
| CN113097438B (en) | Electrochemical device and electronic device | |
| CN111370695B (en) | Negative electrode active material, and electrochemical device and electronic device using same | |
| CN113795947B (en) | Negative electrode active material, and negative electrode, electrochemical device and electronic device including the same | |
| CN112335080B (en) | Negative electrode active material, and electrochemical device and electronic device using same | |
| CN113812021A (en) | Electrochemical device and electronic device | |
| WO2021203408A1 (en) | Negative electrode active material, and electrochemical device and electronic device using same | |
| CN112689919A (en) | Negative electrode active material, and electrochemical device and electronic device using same | |
| CN114144919A (en) | Positive pole piece, electrochemical device comprising positive pole piece and electronic device | |
| WO2023050044A1 (en) | Electrochemical apparatus and electronic apparatus | |
| JP7190030B2 (en) | Negative electrode active material and electrochemical device and electronic equipment using the same | |
| CN112421031B (en) | Electrochemical device and electronic device | |
| CN113517442A (en) | Negative electrode material, electrochemical device, and electronic device | |
| WO2023184080A1 (en) | Electrochemical apparatus and electronic apparatus | |
| CN116581245A (en) | Negative electrode, electrochemical device using same and electronic device | |
| CN114762151A (en) | Cathode material and electrochemical device comprising same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |