CN111261925A - Lithium iron phosphate power battery - Google Patents
Lithium iron phosphate power battery Download PDFInfo
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- CN111261925A CN111261925A CN202010046692.9A CN202010046692A CN111261925A CN 111261925 A CN111261925 A CN 111261925A CN 202010046692 A CN202010046692 A CN 202010046692A CN 111261925 A CN111261925 A CN 111261925A
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- Prior art keywords
- iron phosphate
- lithium iron
- lithium
- electrode material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- 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 invention provides a lithium iron phosphate power battery, which comprises a positive electrode material, a negative electrode material and electrolyte, wherein the positive electrode material comprises an aggregate of lithium iron phosphate secondary particles and uniformly dispersed graphene, and the graphene is coated on the lithium iron phosphate secondary particles and distributed among the lithium iron phosphate secondary particles; the negative electrode material comprises natural graphite and artificial graphite, and the artificial graphite is modified by carbon coating; the electrolyte includes a co-solvent component, a film-forming additive, and a lithium salt. The lithium iron phosphate power battery provided by the invention can be charged and discharged normally at low temperature and has good cycle performance.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of power batteries, in particular to a lithium iron phosphate power battery.
[ background of the invention ]
With the increase of the supporting force of new energy in China, new energy policies are intensively developed, and the development plans of energy-saving and new energy vehicles (2011 to 2020) point out that the industrialization and marketization of new energy vehicles in China reach the first global level by 2020. The lithium iron phosphate power battery attracts people's high attention by virtue of high safety, good high-temperature characteristic, extremely long cycle life, environmental friendliness, no toxicity, no harm, relatively low price and the like, and gradually becomes an important choice for the power battery of the electric vehicle.
However, the lithium iron phosphate material has poor electronic conductivity and low lithium ion diffusivity, so that the low-temperature performance of the lithium iron phosphate battery is poor, and the requirement of the electric vehicle on running at low temperature is difficult to meet. When the existing electric vehicle is charged at low temperature, the charging time at-25 ℃ is 63% slower than that at 25 ℃, and the low-temperature charging time is prolonged. The cycle life is greatly reduced at low temperature, and in a working environment of-10 ℃, if one electric vehicle is charged and discharged once a day, the battery is scrapped after three months.
In order to improve the low-temperature charge and discharge performance of the lithium iron phosphate battery, a conventional method is to add a conductive agent in the anode batching process, improve the contact among lithium iron phosphate particles and improve the conductivity. But the conductivity and the specific surface area of the conductive agent are limited, so that the conductive agent has no obvious effect on reducing the internal resistance of the battery, and improving the low-temperature charge and discharge performance and the low-temperature cycle performance of the battery. In addition, by adding a plurality of organic solvents for co-dissolution and compounding, the viscosity of the electrolyte is reduced, and the ion diffusion rate is improved. But because part of the solvent in the electrolyte is easy to crystallize at low temperature, the ion migration is difficult and the conductivity is low.
In view of the above, it is desirable to provide a new lithium iron phosphate power battery to overcome the above-mentioned drawbacks.
[ summary of the invention ]
The invention aims to provide a lithium iron phosphate power battery which can be normally charged and discharged at low temperature and has good cycle performance.
In order to achieve the purpose, the invention provides a lithium iron phosphate power battery, which comprises a positive electrode material, a negative electrode material and electrolyte; the positive electrode material comprises an aggregate of lithium iron phosphate secondary particles and uniformly dispersed graphene, and the graphene is coated on the lithium iron phosphate secondary particles and distributed among the lithium iron phosphate secondary particles; the negative electrode material comprises natural graphite and artificial graphite, and the artificial graphite is modified by carbon coating; the electrolyte includes a co-solvent component, a film-forming additive, and a lithium salt.
In a preferred embodiment, the mass ratio of the lithium iron phosphate to the graphene coated on the surface of the lithium iron phosphate is 60-100: 1.
In a preferred embodiment, the number of graphene layers coated on the surface of the lithium iron phosphate particles is 5 to 8.
In a preferred embodiment, the anode material further includes soft carbon and hard carbon; the soft carbon and the hard carbon are amorphous carbon.
In a preferred embodiment, the co-solvent comprises ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate and propylene carbonate.
In a preferred embodiment, the film forming additive comprises vinylene carbonate, fluoroethylene carbonate, propylene sulfite.
In a preferred embodiment, the lithium salt includes LiPF6, LiODFB, LiTFSI, lidfo.
According to the lithium iron phosphate power battery provided by the invention, the conductivity of the lithium iron phosphate secondary particles is greatly improved by coating the graphene on the lithium iron phosphate secondary particles; the artificial graphite is modified by carbon coating, so that the artificial graphite is beneficial to ion diffusion and improves the cycle performance of the graphite. The lithium iron phosphate power battery provided by the invention can be charged and discharged normally at low temperature and has good cycle performance.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantageous effects of the present invention more apparent, the following detailed description of the present invention is provided for further details. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The invention provides a lithium iron phosphate power battery which comprises a positive electrode material, a negative electrode material and electrolyte. The positive electrode material comprises aggregates of lithium iron phosphate secondary particles and uniformly dispersed graphene, wherein the graphene is coated on the lithium iron phosphate secondary particles and distributed among the lithium iron phosphate secondary particles, so that the conductivity and the ion diffusion rate of the lithium iron phosphate are greatly improved. The graphene has a unique two-dimensional layered nano structure and a huge specific surface area, the electron movement speed of the graphene is 2 orders of magnitude greater than that of a carbon nanotube, so that the graphene has excellent conductivity, and the conductivity of the graphene coated modified lithium iron phosphate material is greatly improved. Meanwhile, the lithium iron phosphate material is subjected to nanocrystallization granulation, so that the diffusion distance of lithium ions in the crystal grains is reduced, and the diffusion speed of the lithium ions is increased. In the embodiment, the mass ratio of the lithium iron phosphate to the graphene coated on the surface of the lithium iron phosphate is 60-100: 1; the number of layers of the graphene coated on the surfaces of the lithium iron phosphate particles is 5-8.
The negative electrode material comprises natural graphite and artificial graphite, and the artificial graphite is modified by carbon coating. The structure, crystal face spacing, conductivity and ion diffusion rate of the cathode material have great influence on the low-temperature performance of the battery. A large number of gaps exist among the natural graphite laminated structures, so that more channels are improved for ion migration, and ion diffusion is facilitated; however, natural graphite has poor compatibility with electrolyte, so that solvated lithium ions are easily intercalated in the charging and discharging process to cause graphite sheet peeling, so that the cycle performance is reduced, and the high-current charging and discharging performance is poor. The natural artificial composite graphite modified by carbon coating not only maintains the outstanding ion diffusion rate and high capacity characteristics of natural graphite, but also improves the cycle performance of graphite. Therefore, the mode of mixing natural graphite and artificial graphite is adopted, so that more channels are increased for ion migration, ion diffusion is facilitated, and the cycle performance of graphite is improved.
Further, the negative electrode material further comprises soft carbon and hard carbon. The soft carbon and the hard carbon are amorphous carbon, the surfaces of the soft carbon and the hard carbon have more defect areas, and the crystal face spacing of the soft carbon and the hard carbon is larger, so that the ion diffusion is facilitated, and the high-rate discharge and low-temperature charge and discharge performance can be improved. However, the soft carbon and hard carbon layers have more gaps in the surface structure, so that more lithium ions are consumed, the irreversible capacity is increased, and the first discharge efficiency is low. The negative electrode material system adopts modified natural and artificial composite graphite, soft carbon and hard carbon for compounding, thereby not only ensuring that the capacity of the negative electrode is not too low, but also playing the excellent charge and discharge performance of the soft carbon and the hard carbon.
The electrolyte includes a co-solvent component, a film-forming additive, and a lithium salt. The cosolvent comprises Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DMC), Ethyl Acetate (EA) and Propylene Carbonate (PC), and can effectively improve the low-temperature conductivity of the electrolyte and improve the low-temperature charge and discharge performance.
The film forming additive comprises Vinylene Carbonate (VC), fluoroethylene carbonate (FEC) and Propylene Sulfite (PS), and can form a compact, uniform and stable SEI film, enhance the compatibility of a negative electrode and an electrolyte, improve the conductivity of lithium ions between the electrolyte and a negative electrode interface, and improve the low-temperature charge and discharge performance of the battery.
The lithium salt includes LiPF6, LiODFB, LiTFSI, and lidfo. The lithium salt is mainly LiPF6, lithium salt components such as LiODFB, LiTFSI, LiDFOB and the like are properly added, and the addition of LiODFB, LiTFSI and LiDFOB can help the negative electrode to form a uniform, compact and low-impedance SEI film, so that the low-temperature cycle performance of the battery is effectively improved.
During testing, the positive active material is a lithium iron phosphate material which is coated, modified and nano-granulated by graphene, and the primary particle size of the lithium iron phosphate material is less than 100 nm; the negative electrode material selects modified natural graphite and artificial graphite; preparing electrolyte, wherein the electrolyte consists of a quaternary organic solvent system, lithium salt and an additive
In the first embodiment, the first step is,
-30 ℃/1C charge-discharge test,
the test method comprises the following steps: (1) and (4) carrying out capacity grading test on the battery cell at normal temperature.
(2) And discharging the battery cell to 2.0V at normal temperature.
(3) Standing at-30 deg.C for 24 h.
(4) And charging the battery cell at a rate of 1C.
In the second embodiment, the first embodiment of the method,
-40 ℃/1C discharge test,
the test method comprises the following steps: (1) and (4) carrying out capacity grading test on the battery cell at normal temperature.
(2) And discharging the battery cell to 2.0V at normal temperature.
(3) Standing at-40 deg.C for 24 h.
(4) And charging the battery cell at a rate of 1C.
As can be seen from the comparison of the data in the first and second embodiments, the discharge values of the first and second battery cells at normal temperature are substantially the same. The charge capacity ratio of 83.71% in the first embodiment is obviously greater than the charge capacity ratio of 74.55% in the second embodiment, which indicates that the influence of the low temperature difference on the charging of the battery cell is still relatively large; the discharge capacity ratio 75.33% in the first embodiment is closer to the charge capacity ratio 74.37% in the second embodiment, which indicates that the discharge influence of the low-temperature difference on the battery cell is small and can be ignored almost and is far higher than the discharge capacity ratio of the battery cell in the current low-temperature state.
EXAMPLE III
Cycle test at-20 ℃/1C
The test method comprises the following steps: (1) and fully charging the battery cell at normal temperature.
(2) Standing at-20 deg.C for 24 h.
(3) Discharging at 1C to 2.0V, standing for 20 min; 1C is charged to 3.65V, and the cut-off current is 0.03C; standing for 20 min;
(4) cycle 150 weeks was cut off.
| Example of the implementation | Number of cycles | Capacity retention ratio% |
| Case one | 150 weeks | 86.21％ |
In the third example, the cell was repeatedly charged and discharged at a low temperature, and after 150 cycles, the capacity explosion rate of the cell remained at 86.21%, indicating that the cell was well charged and discharged at a low temperature and the low temperature performance of the electrical property was good.
According to the lithium iron phosphate power battery provided by the invention, the conductivity of the lithium iron phosphate secondary particles is greatly improved by coating the graphene on the lithium iron phosphate secondary particles; the artificial graphite is modified by carbon coating, so that the artificial graphite is beneficial to ion diffusion and improves the cycle performance of the graphite. The lithium iron phosphate power battery provided by the invention can be charged and discharged normally at low temperature and has good cycle performance.
The invention is not limited solely to that described in the specification and the embodiments, and additional advantages and modifications will readily occur to those skilled in the art, and it is not desired to limit the invention to the exact details and representative devices illustrated and described, without departing from the spirit and scope of the general concepts defined in the appended claims and their equivalents.
Claims (7)
1. The utility model provides a lithium iron phosphate power battery, includes cathode material, cathode material and electrolyte, its characterized in that: the positive electrode material comprises an aggregate of lithium iron phosphate secondary particles and uniformly dispersed graphene, and the graphene is coated on the lithium iron phosphate secondary particles and distributed among the lithium iron phosphate secondary particles; the negative electrode material comprises natural graphite and artificial graphite, and the artificial graphite is modified by carbon coating; the electrolyte includes a co-solvent component, a film-forming additive, and a lithium salt.
2. The method of making a lithium iron phosphate power cell of claim 1, wherein: the mass ratio of the lithium iron phosphate to the graphene coated on the surface of the lithium iron phosphate is 60-100: 1.
3. The method of making a lithium iron phosphate power cell of claim 1, wherein: the number of layers of the graphene coated on the surfaces of the lithium iron phosphate particles is 5-8.
4. The method of making a lithium iron phosphate power cell of claim 1, wherein: the negative electrode material further comprises soft carbon and hard carbon; the soft carbon and the hard carbon are amorphous carbon.
5. The method of making a lithium iron phosphate power cell of claim 1, wherein: the cosolvent comprises ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate and propylene carbonate.
6. The method of making a lithium iron phosphate power cell of claim 1, wherein: the film forming additive comprises vinylene carbonate, fluoroethylene carbonate and propylene sulfite.
7. The method of making a lithium iron phosphate power cell of claim 1, wherein: the lithium salt includes LiPF6, LiODFB, LiTFSI, and lidfo.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010046692.9A CN111261925A (en) | 2020-01-16 | 2020-01-16 | Lithium iron phosphate power battery |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010046692.9A CN111261925A (en) | 2020-01-16 | 2020-01-16 | Lithium iron phosphate power battery |
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| Publication Number | Publication Date |
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| CN111261925A true CN111261925A (en) | 2020-06-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202010046692.9A Pending CN111261925A (en) | 2020-01-16 | 2020-01-16 | Lithium iron phosphate power battery |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111969188A (en) * | 2020-08-20 | 2020-11-20 | 贵州梅岭电源有限公司 | Low-temperature graphene/graphite fluoride cathode material |
| TWI762404B (en) * | 2021-08-17 | 2022-04-21 | 台灣立凱電能科技股份有限公司 | Method of manufacturing cathode material for secondary battery |
-
2020
- 2020-01-16 CN CN202010046692.9A patent/CN111261925A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111969188A (en) * | 2020-08-20 | 2020-11-20 | 贵州梅岭电源有限公司 | Low-temperature graphene/graphite fluoride cathode material |
| TWI762404B (en) * | 2021-08-17 | 2022-04-21 | 台灣立凱電能科技股份有限公司 | Method of manufacturing cathode material for secondary battery |
| US11837713B2 (en) | 2021-08-17 | 2023-12-05 | Advanced Lithium Electrochemistry Co., Ltd. | Preparation method of cathode material for secondary battery |
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