CN109546109B - High-temperature stable lithium battery anode - Google Patents
High-temperature stable lithium battery anode Download PDFInfo
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- CN109546109B CN109546109B CN201811340633.1A CN201811340633A CN109546109B CN 109546109 B CN109546109 B CN 109546109B CN 201811340633 A CN201811340633 A CN 201811340633A CN 109546109 B CN109546109 B CN 109546109B
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- 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
- H01M4/364—Composites as mixtures
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H—ELECTRICITY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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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- 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 high-temperature stable lithium battery positive electrode which comprises a positive electrode current collector and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry comprises a positive electrode active substance, a conductive agent, a binder and a solvent, and the positive electrode active substance comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of (0.2-0.8): (1-1.5): (0.5-1): 1. According to the invention, lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate are compounded according to a specific proportion, and the structural change of the material in the charging and discharging processes can be slowed down by utilizing the structural difference and the surface energy difference of different materials, so that the dissolution of divalent metal ions in the charging and discharging processes is reduced, and the stability of the material is improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a high-temperature stable lithium battery anode.
Background
The lithium ion battery has the advantages of high open-circuit voltage, large energy density, long service life, no memory effect, no pollution, small self-discharge and the like, is a battery system with the best comprehensive performance at present, and is also a battery system with the widest applicable range. Through the rapid development of over ten years, the lithium ion battery industry chain is mature in China, the technical performance, the maturity and the industrialization reach a considerable scale, the lithium ion battery industry chain is the first choice for new energy and batteries in the electric automobile industry in a future period, and the lithium ion battery industry chain has absolute popularization and application advantages and huge development space. It is well known that the performance of lithium ion batteries depends mainly on the structure and performance of the lithium ion battery material. The lithium ion battery material mainly comprises a positive electrode material, a negative electrode material, a diaphragm and electrolyte, wherein the positive electrode material directly determines the performances of the lithium ion battery such as energy density, service life and the like, and is a key influence factor of the performance of the lithium ion battery.
As the anode material of the power lithium ion battery, ternary oxide series materials containing cobalt and nickel, phosphate series materials such as lithium iron phosphate and the like and spinel lithium manganate materials become alternative common materials by respective advantages. The spinel lithium manganate material has the outstanding advantages of high energy density, high power density, high working voltage, low cost and the like, and is a power type lithium ion battery anode material with the most application prospect. Ternary materials also have their own problems, among them poor high temperature storage performance and poor high temperature cycle capacity retention. And lithium cell group is in electric motor car in-service use, even if there is BMS's management and control, and the module temperature rise also often reaches more than 50 ℃, and present ternary material cycle life is not ideal, therefore how to promote the cycle life of battery under the high temperature condition and become very important problem.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the high-temperature stable lithium battery anode which has good cycling stability at high temperature and can effectively prolong the cycling life of the battery at high temperature.
In order to solve the technical problems, the invention provides a high-temperature stable lithium battery positive electrode which comprises a positive electrode current collector and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry comprises a positive electrode active substance, a conductive agent, a binder and a solvent, and the positive electrode active substance comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of (0.2-0.8): (1-1.5): (0.5-1): 1.
The inventor of the invention finds that the lithium manganate, the nickel cobalt lithium manganate 532, the lithium vanadium phosphate and the lithium iron phosphate are compounded according to a specific proportion in a long-term research and development process, so that the synergistic effect among materials can be optimized, the contact area of a positive electrode material is increased, the lithium ion transmission is facilitated in the circulating charge and discharge process of the lithium battery, the internal resistance is reduced, and the charge and discharge efficiency is improved; in addition, due to the structural difference and the surface energy difference of different materials, the structural change of the materials in the charge and discharge process can be slowed down, and the dissolution of divalent metal ions in the charge and discharge process is reduced, so that the stability of the materials is improved.
In order to further improve the cycle stability of the lithium battery positive electrode at high temperature, the weight ratio of lithium manganese oxide, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate in the positive electrode active material is preferably (0.35-0.66): (1.15-1.36): (0.58-0.85): 1; more preferably (0.42 to 0.6): (1.2-1.32): (0.6-0.75): 1, for example, can be 0.35:1.15:0.85: 1; 0.66:1.36:0.58: 1; 0.42:1.26:0.68: 1; 0.6:1.32:0.75: 1; 0.5:1.2:0.6:1.
The inventor of the invention finds that the tap density of each substance in the positive active material has a remarkable influence on the high-temperature cycle performance of the lithium battery positive electrode, the cycle stability of the lithium battery positive electrode at high temperature can be remarkably improved by adjusting the tap density of each substance in the positive active material, and preferably, the tap density of lithium manganate is 2.8-4.3 g/cm3(ii) a More preferably 3 to 3.8g/cm3(for example, it may be 2.8g/cm3；3g/cm3；3.2g/cm3；3.5g/cm3；3.8g/cm3；4g/cm3；4.2g/cm3；4.3g/cm3)；
The tap density of the nickel cobalt lithium manganate 532 is 2.9-3.5 g/cm3(ii) a More preferably 3 to 3.8g/cm3(for example, it may be 2.9g/cm3；3g/cm3；3.2g/cm3；3.5g/cm3；)；
The tap density of the lithium vanadium phosphate and the lithium vanadium phosphate is 2.9-3.8 g/cm3(ii) a More preferably 3.2 to 3.6g/cm3(for example, it may be 2.9g/cm3；3.2g/cm3；3.5g/cm3；3.6g/cm3；3.8g/cm3)；
The tap density of the lithium iron phosphate is 2.8-3.6 g/cm3(ii) a More preferably 3 to 3.2g/cm3(for example, it may be 2.8g/cm3；3g/cm3；3.2g/cm3；3.5g/cm3；3.6g/cm3)。
The positive electrode of the invention comprises the following components: 95 wt% of a positive electrode active material, 3 wt% of a conductive agent, and 2 wt% of a binder.
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The conductive agent in the present invention may be known to those skilled in the art, and when the conductive agent is formed by mixing conductive graphite and carbon nanotubes in an amount of 1: (1-2), the cycle stability of the lithium battery positive electrode at high temperature can be further improved.
The binder of the present invention can be known to those skilled in the art, and when the binder is sodium carboxymethylcellulose and PVDF in a weight ratio of 1: (1.5-2), the cycling stability of the lithium battery anode at high temperature can be further improved.
The lithium battery anode is suitable for being combined with various conventional lithium battery cathodes to prepare a lithium battery with good cycling stability at high temperature. When the negative active material is artificial graphite, mesocarbon microbeads and porous carbon, the ratio of (0.5-0.8) to 1: (0.1-0.3), the cycle performance of the lithium battery is best.
Through the technical scheme, the invention has the following technical effects:
according to the invention, by compounding lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to a specific proportion, the synergistic effect among materials can be optimized, the contact area of the anode material is increased, the lithium ion transmission is facilitated in the circulating charge-discharge process of the lithium battery, the internal resistance is reduced, and the charge-discharge efficiency is increased; in addition, due to the structural difference and the surface energy difference of different materials, the structural change of the materials in the charge and discharge process can be slowed down, and the dissolution of divalent metal ions in the charge and discharge process is reduced, so that the stability of the materials is improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
The high-temperature stable lithium battery positive electrode material consists of a positive electrode current collector copper foil and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry consists of 95 wt% of positive electrode active substances, 3 wt% of conductive agents (consisting of conductive graphite and carbon nano tubes in a weight ratio of 1:1.5), 2 wt% of binders (sodium carboxymethyl cellulose and PVDF in a weight ratio of 1:1.8) and solvents;
the positive active material is composed of lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.5:1.2:0.6: 1;
the tap density of the lithium manganate is 3.5g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 3.2g/cm3(ii) a The tap density of the lithium vanadium phosphate is 3.2g/cm3(ii) a The tap density of the lithium manganate is 3.2g/cm3。
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The embodiment also provides a lithium battery which comprises a positive electrode, a diaphragm, a negative electrode and electrolyte, wherein the positive electrode is prepared according to the method.
The composition of the negative electrode was: the negative electrode consists of 95 wt% of mesocarbon microbeads, 1 wt% of conductive graphite and 4 wt% of binder (carboxymethyl cellulose);
the negative active material is composed of artificial graphite, mesocarbon microbeads and porous carbon according to the weight ratio of 0.6:1: 0.15.
The preparation method of the negative electrode comprises the following steps:
the cathode material and deionized water are evenly stirred in a vacuum stirrer at the stirring speed of
1200r/min, stirring time of 90min and stirring temperature of 40 ℃ to obtain slurry with viscosity of 3200mPa & s, and sieving the slurry with a 120-mesh sieve to obtain negative electrode slurry; coating the screened negative electrode slurry on the front and back surfaces of a copper foil with the thickness of 8 mu m, drying at 120 ℃, and rolling under the pressure of 1.6MPa to obtain the negative electrode slurry with the compacted density of 1.2g/cm3Areal density of 68g/cm2The negative electrode sheet of (1).
Assembly of a battery
LiPF6 was formulated with methylene methanedisulfonate, Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and dimethyl carbonate (DMC) into a solution having a concentration of 1mol/L of LiPF6 (wherein the weight ratio of EC, EMC and DMC was 1: 1), wherein the content of methylene methanedisulfonate was 2% of the total weight of EC, EMC and DMC, to obtain a nonaqueous electrolytic solution.
The positive electrode, a PE separator having a thickness of 25 μm and a negative electrode were sequentially stacked and wound by a winder to form an aluminum prismatic can battery IFP2714897-20, the obtained electrode assembly was placed in a can case having an open end, the nonaqueous electrolytic solution was poured into the can case, the can case was left at 60 ℃ for 1 day, and then the can case was sealed with steel balls under a vacuum of-0.08 MPa, and the electrochemical properties of the can case were as shown in Table 1.
Example 2
The high-temperature stable lithium battery positive electrode material consists of a positive electrode current collector copper foil and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry consists of 95 wt% of positive electrode active substances, 3 wt% of conductive agents (consisting of conductive graphite and carbon nano tubes in a weight ratio of 1:1.5), 2 wt% of binders (sodium carboxymethyl cellulose and PVDF in a weight ratio of 1:2) and a solvent;
the positive active material comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.6:1.32:0.75: 1;
the tap density of the lithium manganate is 4g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 3.5g/cm3(ii) a The tap density of the lithium vanadium phosphate is 2.9g/cm3(ii) a The tap density of the lithium manganate is 2.8g/cm3。
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The embodiment also provides a lithium battery, which comprises an anode, a diaphragm, a cathode and electrolyte, wherein the anode is prepared according to the method; the method of preparing the negative electrode and the method of assembling the battery were the same as in example 1.
Example 3
The high-temperature stable lithium battery positive electrode material consists of a positive electrode current collector copper foil and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry consists of 95 wt% of positive electrode active substances, 3 wt% of conductive agents (comprising conductive graphite and carbon nano tubes in a weight ratio of 1:1.5), 2 wt% of binders (sodium carboxymethylcellulose and styrene-butadiene latex in a weight ratio of 1:1.5) and solvents;
the positive active material is composed of lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.42:1.26:0.68: 1;
the tap density of the lithium manganate is 3.8g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 2.9g/cm3(ii) a The tap density of the lithium vanadium phosphate is 2.9g/cm3(ii) a The tap density of the lithium manganate is 3.8g/cm3。
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The embodiment also provides a lithium battery, which comprises an anode, a diaphragm, a cathode and electrolyte, wherein the anode is prepared according to the method; the method of preparing the negative electrode and the method of assembling the battery were the same as in example 1.
Example 4
A high-temperature stable lithium battery positive electrode material comprises a positive electrode current collector copper foil and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry comprises 95 wt% of positive electrode active substances, 3 wt% of conductive agents (comprising conductive graphite and carbon nano tubes in a weight ratio of 1: 1), 2 wt% of binders (sodium carboxymethyl cellulose and styrene-butadiene latex in a weight ratio of 1:1.8) and a solvent;
the positive active material is composed of lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.66:1.36:0.58: 1;
the tap density of the lithium manganate is 2.8g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 3.5g/cm3(ii) a The tap density of the lithium vanadium phosphate is 3.0g/cm3(ii) a The tap density of the lithium manganate is 3.5g/cm3。
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The embodiment also provides a lithium battery, which comprises an anode, a diaphragm, a cathode and electrolyte, wherein the anode is prepared according to the method; the method of preparing the negative electrode and the method of assembling the battery were the same as in example 1.
Example 5
A high-temperature stable lithium battery positive electrode material comprises a positive electrode current collector copper foil and positive electrode slurry coated on the positive electrode current collector, wherein the positive electrode slurry comprises 95 wt% of positive electrode active substances, 3 wt% of conductive agents (comprising conductive graphite and carbon nano tubes in a weight ratio of 1:2), 2 wt% of binders (sodium carboxymethyl cellulose and styrene-butadiene latex in a weight ratio of 1:1.8) and a solvent;
the positive active material is composed of lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.35:1.15:0.85: 1;
the tap density of the lithium manganate is 3.2g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 3.2g/cm3(ii) a The tap density of the lithium vanadium phosphate is 3.8g/cm3(ii) a The tap density of the lithium manganate is 3.5g/cm3。
The preparation steps of the positive electrode are as follows:
(1) weighing lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio to obtain a positive electrode mixture, adding the positive electrode mixture, a conductive agent and the binder into a vacuum stirrer, and stirring for 45min at the rotating speed of 20r/min to obtain positive electrode powder;
(2) uniformly stirring the positive electrode powder and NMP in a vacuum stirrer to obtain a positive electrode slurry paste body 1, wherein the stirring speed is 1500r/min, and the stirring time is 60 min;
(3) uniformly stirring the positive electrode slurry mixing paste body 1 and NMP in a vacuum stirrer to obtain a positive electrode slurry mixing paste body 2, wherein the stirring speed is 2000r/min, and the stirring time is 90 min;
(4) adding NMP into the positive electrode slurry-mixing paste body 2 to obtain slurry with the viscosity of 6600mPa & s, and sieving the slurry with a 120-mesh sieve to obtain positive electrode slurry;
(5) and coating the screened positive electrode slurry on the front side and the back side of a copper foil with the thickness of 20 mu m, and then drying and rolling at 120 ℃ to obtain the high-temperature stable lithium battery positive electrode.
The embodiment also provides a lithium battery, which comprises an anode, a diaphragm, a cathode and electrolyte, wherein the anode is prepared according to the method; the method of preparing the negative electrode and the method of assembling the battery were the same as in example 1.
Comparative example 1
The process of example 1 was followed except that: the positive active material comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 0.1:1.8:1.5: 1.
Comparative example 2
The process of example 1 was followed except that: the positive active material is prepared from lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 1:0.5: 0.2: 1.
Comparative example 3
The procedure of example 1 was repeated, except that the tap density of lithium manganate was 2.5g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 4g/cm3(ii) a The tap density of the lithium vanadium phosphate is 2.5g/cm3(ii) a The tap density of the lithium iron phosphate is 4.2g/cm3。
Comparative example 4
The procedure of example 1 was repeated, except that the tap density of lithium manganate was 4.5g/cm3(ii) a The tap density of the nickel cobalt lithium manganate 532 is 2.1g/cm3(ii) a The tap density of the lithium vanadium phosphate is 4g/cm3(ii) a The tap density of the lithium iron phosphate is 2.5g/cm3。
Comparative example 5
The process of example 1 was followed except that: the positive active material comprises lithium manganate, nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio of 0.5:1.8: 1.
Comparative example 6
The process of example 1 was followed except that: the positive active material is composed of nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of 1.2:1.1: 1.
Comparative example 7
The process of example 1 was followed except that: the positive active material is composed of nickel cobalt lithium manganate 532 and lithium iron phosphate according to the weight ratio of 2.3: 1.
Comparative example 8
The process of example 1 was followed except that: the positive active material is lithium iron phosphate.
Examples of the experiments
At 65 ℃, the charge was performed in a constant voltage charge mode with a limit current of 0.5C and a stop voltage of 3.5V, the discharge was performed in a constant current discharge mode with a discharge current of 0.5C and a discharge cut-off voltage of 2.5V, the cycle was performed 600 times, and the capacity retention ratio R after 600 cycles was calculated, and the experimental results are shown in table 1.
Table 1:
| capacity retention rate R/%) | |
| Example 1 | 84.3 |
| Example 2 | 83.2 |
| Example 3 | 81.9 |
| Example 4 | 79.6 |
| Example 5 | 80.6 |
| Comparative example 1 | 65.2 |
| Comparative example 2 | 68.4 |
| Comparative example 3 | 72.3 |
| Comparative example 4 | 73.1 |
| Comparative example 5 | 62.8 |
| Comparative example 6 | 63.2 |
| Comparative example 7 | 61.9 |
| Comparative example 8 | 58.3 |
The above description is only for the purpose of describing some embodiments of the present invention, and is not intended to limit the scope of the present invention, and one skilled in the art can make improvements or modifications to the above embodiments according to the present invention, but all fall within the scope of the present invention.
Claims (9)
1. The utility model provides a high temperature stable form lithium cell positive pole, comprises anodal mass flow body and the anodal thick liquids of coating on the anodal mass flow body, anodal thick liquids comprises anodal active material, conductive agent, binder and solvent, its characterized in that, anodal active material is (0.2 ~ 0.8) by lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate, lithium iron phosphate according to the weight ratio: (1-1.5): (0.5-1): 1, preparing a composition;
the tap density of the lithium manganate is 2.8-4.3 g/cm3；
The tap density of the nickel cobalt lithium manganate 532 is 2.9-3.5 g/cm3；
The tap density of the lithium vanadium phosphate is 2.9-3.8 g/cm3；
The tap density of the lithium iron phosphate is 2.8-3.6 g/cm3。
2. The high temperature stable lithium battery positive electrode according to claim 1, wherein the positive electrode active material comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of (0.35-0.66): (1.15-1.36): (0.58-0.85): 1.
3. The high temperature stable lithium battery positive electrode according to claim 2, wherein the positive electrode active material comprises lithium manganate, nickel cobalt lithium manganate 532, lithium vanadium phosphate and lithium iron phosphate according to the weight ratio of (0.42-0.6): (1.2-1.32): (0.6-0.75): 1.
4. A high temperature stable lithium battery positive electrode as claimed in any one of claims 1 to 3, wherein the tap density of lithium manganate is 3 to 3.8g/cm3。
5. The high temperature stable lithium battery positive electrode according to claim 4, wherein the tap density of NiCoMn 532 is 3-3.5 g/cm3。
6. According to the claimsSolving 5 the high-temperature stable lithium battery positive electrode, wherein the tap density of the lithium vanadium phosphate is 3.2 to 3.6g/cm3。
7. The high temperature stable lithium battery positive electrode according to claim 6, wherein the tap density of the lithium iron phosphate is 3 to 3.2g/cm3。
8. The high temperature stable lithium battery positive electrode of claim 7, wherein the conductive agent is formed from conductive graphite and carbon nanotubes in a weight ratio of 1: (1-2).
9. The high temperature stable lithium battery positive electrode of claim 8, wherein the binder is sodium carboxymethyl cellulose and PVDF in a weight ratio of 1: (1.5-2).
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