CN112968169A

CN112968169A - Composite negative electrode material for lithium ion battery and preparation method thereof

Info

Publication number: CN112968169A
Application number: CN202110143079.3A
Authority: CN
Inventors: 阳柳; 王燕飞; 周桂民
Original assignee: Changde Sucarbon New Energy Technology Co ltd
Current assignee: Ganzhou Litan New Energy Technology Co.,Ltd.
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2021-06-15

Abstract

A composite anode material for a lithium ion battery and a preparation method thereof are provided, wherein the composite anode material comprises: the carbon particles are obtained by performing high-temperature sintering operation, mechanical shaping operation and surface coating operation on carbon raw materials. According to the invention, the hard carbon particles and the graphite particles are compounded, and the performance advantages of the hard carbon particles and the graphite particles are complementary, so that the rate performance and the low-temperature performance of the composite material are improved, and the first efficiency, the high temperature and the storage performance of the composite material can be ensured; when the composite negative electrode material provided by the invention is used as a negative electrode active material of a lithium ion battery, the lithium ion battery has excellent rate performance, the raw materials are cheap, the preparation process and equipment are mature, and the composite negative electrode material is suitable for large-scale production.

Description

Composite negative electrode material for lithium ion battery and preparation method thereof

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a composite negative electrode material for a lithium ion battery and a preparation method thereof.

Background

The lithium ion battery has the advantages of good stability, high energy density, no memory effect and the like, and is widely applied to the field of 3C consumer batteries, power batteries and energy storage batteries, the current commercial lithium ion battery composite negative electrode material mainly uses a graphite particle negative electrode, but the theoretical specific capacity of the graphite particle negative electrode is lower and only 372mAh/g, and the high-rate continuous charge and discharge capacity and the low-temperature performance are difficult to effectively improve, so that the development of a novel lithium ion battery negative electrode material which has high specific capacity, excellent rate performance and good low-temperature performance is an important direction of current research.

Disclosure of Invention

In order to solve the above problems, the present invention provides a composite anode material for a lithium ion battery, comprising: the carbon particles are obtained by performing high-temperature sintering operation, mechanical shaping operation and surface coating operation on carbon raw materials.

Preferably, the mass fraction of the hard carbon particles is 10% -50%, and the mass fraction of the graphite particles is 50% -90%.

Preferably, the carbon raw material is one or more of a high molecular material or a saccharide.

Preferably, the polymer material comprises one or more of polyvinyl chloride resin, acrylic resin, phenolic resin, epoxy resin, polyester resin, polyamide resin, bismaleimide, polypropylene polycarbonate, polyether ether ketone or polystyrene.

Preferably, the saccharide comprises one or more of fructose, mannose, sucrose, glucose, galactose, an amino sugar, ribose or deoxyribose.

Preferably, the graphite particles are one or more of artificial graphite particles, natural graphite particles, isostatic pressing graphite particles, mould pressing graphite particles, extrusion graphite particles, dense crystalline graphite particles, crystalline flake graphite particles, cryptocrystalline graphite particles, micron graphite particles or nano-silicon graphite particles.

Preferably, the temperature in the high-temperature sintering operation is 1000-1500 ℃, and the sintering time is 2-4 h.

Preferably, the particle size D50 in the mechanical shaping operation is 3 μm to 10 μm.

Preferably, the organic material in the surface coating operation is one or more of methane, ethane, ethylene, acetylene, propane, propylene, acetone, butane, butylene, pentane, hexane, liquefied gas, polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyether polyester resin, polyamide resin or polyimide resin, and the average thickness of the coating layer is 10nm to 1000 nm.

The invention also provides a preparation method of the composite anode material for the lithium ion battery, the composite anode material comprises the composite anode material for the lithium ion battery, and the method comprises the following steps:

preparing a carbon raw material and graphite particles;

adding the carbon raw material into an atmosphere furnace, introducing nitrogen for protection, controlling the oxygen content in the atmosphere furnace to be lower than 300ppm, sintering at 1000-1500 ℃ for 2-4 h, and obtaining a first carbon precursor;

crushing the first carbon precursor, controlling the particle size D50 to be 3-10 μm, then sieving by a 320-mesh sieve to remove large particles, and controlling the magnetic foreign matters in the first carbon precursor to be less than 0.5ppm through a demagnetizing process to obtain a second carbon precursor;

compounding the second carbon precursor with an organic material, and performing pyrolysis to form a thermal decomposition product of the organic material on the surface of the second carbon precursor to form a coating layer and obtain hard carbon particles;

and sequentially carrying out high-speed mixing and three-eccentric mixing on the hard carbon particles and the graphite particles to obtain the composite cathode material.

The composite negative electrode material for the lithium ion battery and the preparation method thereof have the advantages that:

(1) in the composite negative electrode material prepared by the invention, the hard carbon particles have higher first reversible capacity, the first reversible capacity is more than 450mAh/g, and the first reversible capacity of the composite negative electrode material can be higher than that of the traditional graphite negative electrode;

(2) in the composite cathode material prepared by the invention, the hard carbon particles have excellent dynamic performance, and the low-temperature performance and the cycle performance of the composite cathode material can be obviously improved;

(3) in the composite cathode material prepared by the invention, the graphite particles are the traditional mature cathode material, so that the composite cathode material has a quite stable voltage platform and first efficiency, and the comprehensive electrochemical performance of the composite cathode material can be ensured;

(4) in the composite negative electrode material prepared by the invention, the thermal decomposition product of the organic material forms a coating layer, so that on one hand, the conductivity and the ion transmission rate of the negative electrode material can be obviously improved, on the other hand, the corrosion of the electrolytic solution can be isolated, the structure of the negative electrode material is stabilized, and the electrochemical performance of the negative electrode material is improved;

(5) the composite negative electrode material prepared by the invention has the advantages of low price of raw materials, mature preparation process and equipment, and suitability for large-scale production;

(6) the composite anode material prepared by the invention has excellent electrochemical performance, high specific capacity which is more than 370mAh/g, high first efficiency which is more than or equal to 87 percent, and excellent cycle performance, and the cycle capacity retention rate of 18650 cylindrical batteries for 4000 times can reach 83 percent under the charge-discharge rate of 1C/1C.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a cross-sectional view of hard carbon particles in example 1 of the present invention;

FIG. 2 is an SEM image of a composite anode material prepared in example 1 of the present invention;

FIG. 3 is an XRD pattern of a composite anode material prepared in example 1 of the present invention;

fig. 4 is a first charge-discharge curve of button cell with hard carbon particles in composite negative electrode material prepared in example 1 of the present invention;

FIG. 5 is the first charge-discharge curve of button cell with graphite particles in composite negative electrode material prepared in example 1 of the present invention;

FIG. 6 is the first charge-discharge curve of the button cell with composite negative electrode material prepared in example 1 of the present invention;

FIG. 7 is a cycle curve of the composite anode material prepared in example 1 of the present invention at 1C/1C rate in 18650 cylindrical cells.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

The invention provides a composite anode material for a lithium ion battery, which comprises the following components: the carbon particles are obtained by performing high-temperature sintering operation, mechanical shaping operation and surface coating operation on carbon raw materials.

Specifically, the mass fraction of the hard carbon particles is 10% -50%, and the mass fraction of the graphite particles is 50% -90%.

Specifically, the carbon raw material is one or more of a high molecular material or a saccharide.

Specifically, the polymer material comprises one or more of polyvinyl chloride resin, acrylic resin, phenolic resin, epoxy resin, polyester resin, polyamide resin, bismaleimide, polypropylene polycarbonate, polyether ether ketone or polystyrene.

Specifically, the saccharide includes one or more of fructose, mannose, sucrose, glucose, galactose, an amino sugar, ribose, or deoxyribose.

Specifically, the graphite particles are one or more of artificial graphite particles, natural graphite particles, isostatic pressing graphite particles, mould pressing graphite particles, extrusion graphite particles, dense crystalline graphite particles, crystalline flake graphite particles, cryptocrystalline graphite particles, micron graphite particles or nano silicon graphite particles.

Specifically, the temperature in the high-temperature sintering operation is 1000-1500 ℃, and the sintering time is 2-4 h.

Specifically, the particle size D50 in the mechanical shaping operation is 3 μm to 10 μm.

Specifically, the organic material in the surface coating operation is one or more of methane, ethane, ethylene, acetylene, propane, propylene, acetone, butane, butylene, pentane, hexane, liquefied gas, polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyether polyester resin, polyamide resin or polyimide resin, and the average thickness of the coating layer is 10nm-1000 nm.

preparing a carbon raw material and graphite particles;

Specifically, the hard carbon particles were prepared into a cross-sectional planar sample by an argon ion cutter, and contained a pore structure inside thereof when used for SEM imaging observation.

Specifically, the device for performing the high-speed mixing is a high-efficiency VC mixer, and the device for performing the triple eccentric mixing is a triple eccentric mixer.

Specifically, when the button cell is used for testing the specific capacity of the material, the voltage range is 0.005V-1.5V, the test current is 350mA, the reversible capacity of the hard carbon particles is greater than 450mAh/g, the reversible capacity of the graphite particles is greater than 330mAh/g, and the reversible capacity of the composite negative electrode material is between the capacity of the graphite particles and the capacity of the hard carbon particles.

Specifically, when a particle size range of the material is tested by using a malvern laser particle sizer Mastersizer 3000, the particle size D50 of the hard carbon particles is 3 μm to 10 μm, the particle size D50 of the graphite is 5 μm to 15 μm, and the particle size D50 of the composite negative electrode material is 4 μm to 15 μm.

Specifically, when the first carbon precursor is pulverized, the pulverizing apparatus is one or more of a jaw crusher, a roller crusher, a double roller crusher, a hammer crusher, a counterimpact crusher, a vertical crusher, a universal crusher, cryogenic pulverization, a mechanical-hammer mill, an ultra-micro impact mill, a flat jet mill, a fluidized bed opposed jet mill, a circulating tube jet mill, an opposed jet mill, or a target jet mill.

Example 1

The preparation method of the composite negative electrode material for the lithium ion battery specifically comprises the following steps:

(1) 1kg of phenolic resin (carbon raw material) is placed in a box furnace, nitrogen is introduced until the oxygen content in the box furnace is lower than 100ppm, then the temperature is raised to 1000 ℃ at 3 ℃/min, and sintering is carried out for 4h, so as to obtain 0.43kg of first carbon precursor. And (3) crushing the first carbon precursor, controlling the granularity D50 after crushing to be 4 microns +/-1 micron, then sieving by a 320-mesh sieve to remove large particles, and finally controlling the magnetic foreign matters in the material to be below 0.5ppm through a demagnetization procedure to obtain a second carbon precursor. And (3) placing the second carbon precursor in a vapor deposition furnace, introducing nitrogen for protection, heating to 700 ℃ at the heating rate of 3 ℃/min, and introducing methane (coating organic material) for vapor deposition to obtain hard carbon particles.

(2) And (2) adding the hard carbon particles and the artificial graphite particles obtained in the step (1) into a high-efficiency VC mixer according to the mass ratio of 50:50, wherein the mixing rotating speed is 800rpm, the mixing time is 1h, adding the mixed materials into a three-eccentric mixer, and further mixing for 1h to obtain the composite negative electrode material.

Example 2

The difference from example 1 is that the carbon raw material in step (1) is polyamide resin, the sintering temperature is 1100 ℃, and the sintering time is 3.5 h. The pulverized particle size of the first carbon precursor was 5 μm ± 1 μm. The organic material of the coating layer of the second carbon precursor is acetylene.

Adding the hard carbon particles and the natural graphite particles into a high-efficiency VC mixer according to the mass ratio of 30:70 in the step (2), uniformly stirring, and then putting into a three-eccentric mixer for mixing to obtain the composite negative electrode material

Example 3

The difference from the example 1 is that the carbon raw material in the step (1) is sucrose, the sintering temperature is 1300 ℃, and the sintering time is 3 h. The pulverized particle size of the first carbon precursor was 7 μm ± 1 μm. The coating organic material of the second carbon precursor is hexane.

Adding the hard carbon particles and the natural graphite into a high-efficiency VC mixer according to the mass ratio of 20:80 in the step (2), uniformly stirring, and then carrying out three-eccentric mixing to obtain the composite cathode material

Example 4

The difference from the example 1 is that the carbon raw material in the step (1) is amino sugar, the sintering temperature is 1500 ℃, and the sintering time is 2 h. The pulverized particle size of the first carbon precursor was 9 ± 1 μm. The organic material of the coating layer of the second carbon precursor is polyethylene.

Adding the hard carbon particles and the natural graphite particles into a high-efficiency VC mixer according to the mass ratio of 10:90 in the step (2), uniformly stirring, and then putting into a triple eccentric mixer for mixing to obtain the composite negative electrode material

Comparative example 1

The difference from example 1 is that the sintering temperature of the hard carbon particles in step (1) is 900 ℃, and the rest is the same as example 1, and the description is omitted.

Comparative example 2

The difference from example 1 is that the sintering temperature of the hard carbon particles in step (1) is 1600 ℃, and the rest is the same as example 1, and will not be described again.

Comparative example 3

The difference from example 1 is that in step (1), the pulverization control particle size D50 of the first carbon precursor is 1 μm, and the rest is the same as example 1, and will not be described again.

Comparative example 4

The difference from example 1 is that in step (1), the pulverization control particle size D50 of the first carbon precursor is 12 μm, and the rest is the same as example 1, and will not be described again.

Comparative example 5

The difference from example 1 is that in step (1), the first carbon precursor is pulverized and then does not undergo the screening and demagnetizing processes, which is the same as example 1 and will not be described herein again.

Comparative example 6

The difference from example 1 is that in step (1), the second carbon precursor is not coated, and the rest is the same as example 1, which is not described herein again.

Comparative example 7

The difference from example 1 is that in step (2), the mass ratio of the hard carbon particles to the natural graphite particles is 5:95, and the rest is the same as example 1, and the description is omitted.

Comparative example 8

The difference from example 1 is that step (2) is not performed, i.e., the hard carbon particles are not mixed with the graphite particles, and the description is omitted as in example 1.

The composite anode materials in examples 1 to 7 and comparative examples 1 to 7 were tested by the following methods:

the particle size range of the material was tested using a malvern laser particle sizer Mastersizer 3000.

The morphology and the graphical processing of the material were analyzed using a field emission Scanning Electron Microscope (SEM) (JSM-7160).

The material was subjected to phase analysis using an XRD diffractometer (X' Pert3 Powder) to determine the grain size of the material.

A cross-sectional plane sample of the negative electrode material was prepared using an argon ion cutter (IB-19530CP) for SEM imaging observation and microscopic analysis.

The specific surface area and porosity of the negative electrode material were determined using a U.S. Mach Chart and pore Analyzer (TriStar II 3020).

And mixing the composite negative electrode materials obtained in the examples 1 to 4 and the comparative examples 1 to 7 in pure solvent water according to a mass ratio of 91:2:2:5, homogenizing, controlling the solid content to be 45%, coating the mixture on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate. Button cells were assembled in an argon atmosphere glove box using a separator Celgard2400, an electrolyte of 1mol/L LiPF6/EC + DMC + EMC (v/v 1:1:1), and a metallic lithium plate as the counter electrode. And (3) performing charge and discharge tests on the button cell, wherein the voltage interval is 5 mV-1.5V, and the current density is 80 mA/g. The first reversible capacity and efficiency of the composite anode materials in examples and comparative examples were measured.

And assembling the ternary positive pole piece prepared by the mature process, 1mol/L LiPF6/EC + DMC + EMC (v/v is 1:1:1) electrolyte, Celgard2400 diaphragm and an outer shell into the 18650 cylindrical single battery by adopting a conventional production process. On a LanD battery test system of Wuhanjinnuo electronics Co Ltd, the charge and discharge performance of the prepared cylindrical battery is tested, and the test conditions are as follows: and (3) charging and discharging at constant current of 0.2C at normal temperature, wherein the charging and discharging voltage is limited to 2.75V-4.2V.

According to the first reversible capacity measured in the button cell, the composite negative electrode materials in the examples and the comparative examples are mixed with the same stable artificial graphite, and the first reversible capacity tested by the button cell of the mixed powder is 480 +/-5 mAh/g. And preparing a negative pole piece from the mixed powder by a button cell process, and assembling a ternary pole piece, an isolating membrane and electrode liquid which are prepared by a mature process as a positive pole into the 18650 cylindrical single cell without changing. The 18650 cylindrical single battery is subjected to charge and discharge tests, the voltage interval is 2.5 mV-4.2V, and the current density is 480mA/g

The test equipment of the button cell and the 18650 cylindrical single cell are both the LAND battery test system of Wuhanjinnuo electronics, Inc.

Results of performance tests of hard carbon particles and composite anode materials in examples 1 to 4 and comparative examples 1 to 8:

table 1 hard carbon particle process parameters and performance indices in examples 1 to 4 and comparative examples 1 to 8:

table 2 components and electrochemical performance test results of the composite anode materials in examples 1 to 4 and comparative examples 1 to 8:

as can be seen from Table 1, the composite negative electrode material prepared by the method has the advantages that the hard carbon has higher first reversible capacity which is more than 450mAh/g, and the first reversible capacity of the composite negative electrode material can be higher than that of the traditional graphite negative electrode (more than 370 mAh/g); the graphite is used as a traditional mature anode material, the composite anode material can be ensured to have a stable voltage platform and a first efficiency (more than or equal to 87%), and the cycle capacity retention rate of 4000 times of the composite anode material prepared by the invention can reach 83% under the charge-discharge rate of 1C/1C in a 18650 cylindrical battery.

In examples 1 to 5, the electrochemical performance of the composite negative electrode material was greatly affected by changing the manufacturing processes of the carbonaceous raw material, the calcination temperature, the coating type, and the like, and when the calcination temperature was high, the reversible capacity of the hard carbon negative electrode material was reduced, but the first efficiency was improved, and the properties of the hard carbon negative electrode finished products prepared from different hard carbon raw materials were also different.

In comparative examples 1-2, changing the calcination temperature affected the internal structure of the hard carbon particles and thus their electrochemical properties, and when the calcination temperature was decreased to 900 ℃, the first efficiency of the obtained hard carbon particles was significantly decreased, only 78.7%, and when the calcination temperature was increased to 1600 ℃, the first reversible capacity of the obtained hard carbon particles was significantly decreased, only 409.0 mAh/g.

In comparative examples 3 to 4, changing the particle size of the hard carbon particles affects on the one hand the diffusion rate of lithium ions inside the hard carbon particles and thus its kinetics, and on the other hand also the contact area of the hard carbon particles with the electrolyte, and especially when the particle size is too small, it causes a significant increase in side reactions, which is detrimental to long-term cycling.

In comparative example 5, after the first carbon precursor was pulverized, the screening and demagnetization steps were not performed, the D100 of the obtained hard carbon particles would be too large, and there would be too large particles that would easily pierce the separator, resulting in battery failure, and the demagnetization step was not performed, so magnetic foreign matter with inevitably high content in the material would significantly affect the electrochemical performance of the composite negative electrode material.

In comparative example 6, the second carbon precursor was not coated, and the reversible capacity and the first efficiency of the prepared composite anode material were slightly improved, but the cycle performance was significantly reduced, and the capacity retention rate was only 58.7% at 4000 cycles of 1C/1C in 18650 cylindrical batteries.

In comparative example 8, the mass ratio of the hard carbon particles to the natural graphite particles was 5:95, and the first efficiency of the prepared composite anode material was 93.3%, but the reversible capacity and the cycle performance were significantly reduced.

In comparative example 8, the hard carbon particles were not mixed with the graphite particles, and the first efficiency of the prepared composite anode material was significantly reduced, only 80.5%, which was difficult to meet the actual performance requirements of the battery.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention shall be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims

1. A composite anode material for a lithium ion battery, comprising: the carbon particles are obtained by performing high-temperature sintering operation, mechanical shaping operation and surface coating operation on carbon raw materials.

2. The composite anode material for a lithium ion battery according to claim 1, wherein the mass fraction of the hard carbon particles is 10% to 50%, and the mass fraction of the graphite particles is 50% to 90%.

3. The composite anode material for a lithium ion battery according to claim 1, wherein the carbon raw material is one or more of a polymer material and a saccharide.

4. The composite anode material for the lithium ion battery according to claim 3, wherein the polymer material comprises one or more of polyvinyl chloride resin, acrylic resin, phenolic resin, epoxy resin, polyester resin, polyamide resin, bismaleimide, polypropylene polycarbonate, polyether ether ketone, or polystyrene.

5. The composite anode material for a lithium ion battery according to claim 3, wherein the saccharide includes one or more of fructose, mannose, sucrose, glucose, galactose, an amino sugar, ribose, or deoxyribose.

6. The composite anode material for lithium ion batteries according to claim 1, wherein said graphite particles are one or more of artificial graphite particles, natural graphite particles, isostatic graphite particles, molded graphite particles, extruded graphite particles, dense crystalline graphite particles, crystalline flake graphite particles, cryptocrystalline graphite particles, micron graphite particles, or nano-silicon graphite particles.

7. The composite anode material for the lithium ion battery according to claim 1, wherein the temperature in the high-temperature sintering operation is 1000 ℃ to 1500 ℃, and the sintering time is 2h to 4 h.

8. The composite anode material for lithium ion batteries according to claim 1, wherein the particle size D50 in the mechanical shaping operation is 3 μm to 10 μm.

9. The composite negative electrode material for lithium ion batteries according to claim 1, wherein the organic material in the surface coating operation is one or more of methane, ethane, ethylene, acetylene, propane, propylene, acetone, butane, butene, pentane, hexane, liquefied gas, polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyether polyester resin, polyamide resin, or polyimide resin, and the average thickness of the coating layer is 10nm to 1000 nm.

10. A method for preparing a composite anode material for a lithium ion battery, wherein the composite anode material comprises the composite anode material for a lithium ion battery according to any one of claims 1 to 9, and the method comprises the steps of:

preparing a carbon raw material and graphite particles;