Preparation method of lithium manganate battery
Technical Field
The invention relates to a preparation method of a lithium manganate battery.
Background
The lithium manganate has the advantages of high safety, low cost, environmental protection and the like, is one of common materials of the lithium ion battery, but the lithium manganate battery has poor cycle performance due to the volume effect, and particularly has serious influence on the application range of the lithium manganate battery due to the dissolution of manganese and the generation of gas caused by the decomposition of electrolyte on the surface of an electrode in a high-temperature environment.
Disclosure of Invention
The invention provides a preparation method of a lithium manganate battery, wherein an active substance in a positive electrode of the lithium manganate battery is LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4The electrolyte of the lithium manganate battery contains an additive, the additive consists of 1-propylene-1, 3-sultone (PST) and 1-propylene-1, 3-sultone (MMDS), and the volume ratio of PST: MMDS ═ 1: 1.35-1.40; and the additive accounts for 3-5% of the volume of the electrolyte; the preparation method comprises the step of adding LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Mixing the materials according to a preset proportion, preparing a first slurry, and mixing the LiFe0.9Mn0.1PO4Preparing a second slurry, sequentially coating and drying the first slurry and the second slurry on a current collector to obtain a positive electrode, preparing artificial graphite into a negative electrode slurry, coating the negative electrode slurry on the current collector and drying to obtain a negative electrode, laminating the positive electrode, a diaphragm and the negative electrode into a battery core, placing the battery core in a shell, injecting electrolyte, and performing formation within a preset voltage range to obtain the lithium manganate battery.
The specific scheme is as follows:
a process for preparing the lithium manganate battery whose positive electrode contains LiMn as active component0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4The electrolyte of the lithium manganate battery contains an additive accounting for 3-5 vol% of the electrolyte, and the additive consists of 1-propylene-1, 3-sultone (PST) and 1-propylene-1, 3-sultone (MMDS), wherein the volume ratio of PST: MMDS ═ 1: 1.35-1.40; the preparation method comprises the step of adding LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Mixing the materials in a predetermined ratio to prepare a first slurry, and mixing the first slurry with LiFe0.9Mn0.1PO4Preparing a second slurry, sequentially coating and drying the first slurry and the second slurry on a current collector to obtain a positive electrode, preparing artificial graphite into a negative electrode slurry, coating the negative electrode slurry on the current collector and drying to obtain a negative electrode, laminating the positive electrode, a diaphragm and the negative electrode into a battery core, placing the battery core in a shell, injecting electrolyte, and performing formation within a preset voltage range to obtain the lithium manganate battery.
Further, the preparation method comprises the following steps:
1) mixing LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Ball milling and mixing the LiMn and the LiMn in a ratio of 8:2-9:10.83Co0.15Al0.02O2Average particleThe diameter is 1.8-2.0 μm, and the LiFe0.9Mn0.1PO4The average grain diameter is 1.2-1.4 μm;
2) adding a solvent into a stirring kettle, then adding a binder and a conductive agent, uniformly stirring, then adding the mixed active material obtained in the step (1), and uniformly stirring to obtain a first slurry, wherein the active material is prepared from the following components in percentage by mass: adhesive: the conductive agent is 100:3-5: 3-5;
3) adding a solvent into a stirring kettle, then adding a dispersing agent, a binder and a conductive agent, uniformly stirring, and then adding LiFe0.9Mn0.1PO4(ii) a The LiFe0.9Mn0.1PO4The average particle size is 0.8-1 mu m, and the second slurry is obtained by uniformly stirring, wherein the mass ratio of the LiFe to the first slurry is0.9Mn0.1PO4: dispersing agent: adhesive: the conductive agent is 100:3-5:3-5: 6-10;
4) coating and drying the first slurry and the second slurry on the aluminum foil to obtain the anode;
5) adding a solvent into a stirring kettle, then adding a binder and a conductive agent, uniformly stirring, and adding a negative electrode active material to obtain negative electrode slurry;
6) coating and drying the negative electrode slurry on the copper foil to obtain the negative electrode;
7) laminating the positive electrode, the diaphragm and the negative electrode into a battery cell, placing the battery cell in a shell, and injecting electrolyte;
8) and forming to obtain the lithium manganate battery.
Further, the formation comprises the following steps:
1) charging to a first preset voltage by constant current, wherein the first preset voltage is 3.2-3.3V;
2) performing constant-current charge-discharge circulation for a plurality of times between a first preset voltage and a second preset voltage, wherein the second preset voltage is 3.4-3.5V;
3) charging at constant current to a charging cut-off voltage, and then charging at constant voltage by using the charging cut-off voltage until the charging current is less than a preset value;
4) constant current charge and discharge cycles are performed between the charge cutoff voltage and the discharge cutoff voltage for several times.
Further, the coating thickness ratio of the first slurry to the second slurry is 6:4-9: 1.
Further, the negative active material is a graphite material.
Further, the charge cut-off voltage is 4.25V, and the discharge cut-off voltage is 2.75V.
Further, the organic solvent of the electrolyte is selected from cyclic carbonate, chain carbonate, functional group-substituted cyclic carbonate or functional group-substituted chain carbonate.
The invention has the following beneficial effects:
1) the inventors found that LiMn0.83Co0.15Al0.02O2The material has good rate performance and high-temperature stability, and LiFe0.9Mn0.1PO4The material has good high-temperature electrolyte stability, and the LiFe is prepared by mixing LiFe and water0.9Mn0.1PO4The material is arranged on the surface of the active layer, so that the high-temperature stability of the anode can be improved, the working voltages of the two materials are relatively close, and the phenomena of voltage polarization and the like can not be generated even if the two materials are mixed for use.
2) The researchers found that by selecting the specific particle size range of the particle size of the active material of the first layer and the surface layer, the first layer can be formed after mixing the two active materials, and the volume expansion rate of the first layer is close to that of the surface layer material, so that the stability of the material layer can be improved, and the active material can be prevented from being separated due to interlayer stress.
3) For LiFe0.9Mn0.1PO4The inventor finds that the addition of 1-propene-1, 3-sultone (PST) and 1-propene-1, 3-sultone (MMDS) in the electrolysis can effectively improve the capacity performance of the battery in a high-temperature environment.
4) Particularly, after the two additives are added in a specific ratio, the capacity performance is obviously improved.
5) According to the specific active material and electrolyte components of the invention, researchers set a specific voltage interval to perform charge-discharge cycle, which is more beneficial to forming a stable SEI film and prolonging the cycle life.
Detailed Description
The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples.
The active material of the positive electrode is LiMn0.83Co0.15Al0.02O2Materials and LiFe0.9Mn0.1PO4The material comprises a positive electrode binder and a negative electrode slurry, wherein the positive electrode binder is polyvinylidene fluoride, a dispersing agent is sodium carboxymethylcellulose, a solvent of the positive electrode slurry is NMP, a solvent of the negative electrode slurry is deionized water, and a binder of the negative electrode slurry is SBR; the electrolyte comprises 1M lithium hexafluorophosphate, and the organic solvent is DMC + EC + PC in a ratio of 1:1: 1; the active material of the negative electrode is a natural graphite negative electrode; the positive and negative electrode active material layers were each 60 μm thick on one side.
Example 1
1) Mixing LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Ball milling and mixing the LiMn and the LiMn in a mass ratio of 8:20.83Co0.15Al0.02O2The average particle diameter is 1.8 mu m, and the LiFe0.9Mn0.1PO4The average particle diameter is 1.2 mu m;
2) adding NMP into a stirring kettle, then adding PVDF and conductive carbon black, stirring uniformly, then adding the mixed active material obtained in the step (1), and stirring uniformly to obtain a first slurry, wherein the active material is prepared from the following components in percentage by mass: PVDF: conductive carbon black 100:3: 3;
3) adding NMP into a stirring kettle, then adding CMC, PVDF and conductive carbon black, stirring uniformly, and then adding LiFe0.9Mn0.1PO4(ii) a The LiFe0.9Mn0.1PO4The average particle size is 0.8 mu m, and the second slurry is obtained by uniformly stirring, wherein the mass ratio of the LiFe to the first slurry is0.9Mn0.1PO4: CMC: PVDF: conductive carbon black 100:3:3: 6;
4) coating and drying first slurry and second slurry on an aluminum foil, wherein the coating thickness ratio of the first slurry to the second slurry is 6:4, and obtaining the anode;
5) adding deionized water into a stirring kettle, then adding SBR and conductive carbon black, uniformly stirring, and then adding natural graphite to obtain negative electrode slurry, wherein the natural graphite: SBR: conductive carbon black 100:4: 4;
6) coating and drying the negative electrode slurry on the copper foil to obtain the negative electrode;
7) laminating a positive electrode, a diaphragm and a negative electrode into a battery cell, placing the battery cell in a shell, and injecting electrolyte, wherein the content of PST in the electrolyte is 1 volume percent, and the content of MMDS is 1.35 volume percent;
8) charging to 3.2V at a constant current of 0.05C;
9) performing constant current charge and discharge at 0.02C between 3.2V and 3.4V for 5 times;
10) charging to 4.25V at constant current of 0.05C, and then charging at constant voltage of 4.25V until the charging current is less than 0.01C;
11) and performing 0.05C constant-current charge and discharge circulation for 3 times between 4.25V and 2.75V to obtain the battery.
Example 2
1) Mixing LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Ball milling and mixing the LiMn and the LiMn in a mass ratio of 9:10.83Co0.15Al0.02O2Average particle diameter of 2.0 μm, said LiFe0.9Mn0.1PO4The average particle diameter is 1.4 mu m;
2) adding NMP into a stirring kettle, then adding PVDF and conductive carbon black, stirring uniformly, then adding the mixed active material obtained in the step (1), and stirring uniformly to obtain a first slurry, wherein the active material is prepared from the following components in percentage by mass: PVDF: conductive carbon black 100:5: 5;
3) adding NMP into a stirring kettle, then adding CMC, PVDF and conductive carbon black, stirring uniformly, and then adding LiFe0.9Mn0.1PO4(ii) a The LiFe0.9Mn0.1PO4The average particle size is 1 mu m, and the second slurry is obtained by uniformly stirring, wherein the mass ratio of the LiFe to the first slurry is0.9Mn0.1PO4: CMC: PVDF: conductive carbon black 100:5:5: 10;
4) coating and drying first slurry and second slurry on an aluminum foil, wherein the coating thickness ratio of the first slurry to the second slurry is 9:1, and obtaining the anode;
5) adding deionized water into a stirring kettle, then adding SBR and conductive carbon black, uniformly stirring, and then adding natural graphite to obtain negative electrode slurry, wherein the natural graphite: SBR: conductive carbon black 100:4: 4;
6) coating and drying the negative electrode slurry on the copper foil to obtain the negative electrode;
7) laminating a positive electrode, a diaphragm and a negative electrode into a battery cell, placing the battery cell in a shell, and injecting an electrolyte, wherein the content of PST in the electrolyte is 2 volume percent, and the content of MMDS is 2.8 volume percent;
8) charging to 3.3V at a constant current of 0.05C;
9) performing constant current charge and discharge at 0.02C between 3.3V and 3.5V for 5 times;
10) charging to 4.25V at constant current of 0.05C, and then charging at constant voltage of 4.25V until the charging current is less than 0.01C;
11) and performing 0.05C constant-current charge and discharge circulation for 3 times between 4.25V and 2.75V to obtain the battery.
Example 3
1) Mixing LiMn0.83Co0.15Al0.02O2And LiFe0.9Mn0.1PO4Ball milling and mixing the LiMn and the LiMn in a mass ratio of 85:150.83Co0.15Al0.02O2An average particle diameter of 1.9 μm, said LiFe0.9Mn0.1PO4The average particle diameter is 1.9 μm;
2) adding NMP into a stirring kettle, then adding PVDF and conductive carbon black, stirring uniformly, then adding the mixed active material obtained in the step (1), and stirring uniformly to obtain a first slurry, wherein the active material is prepared from the following components in percentage by mass: PVDF: conductive carbon black 100:4: 4;
3) adding NMP into a stirring kettle, then adding CMC, PVDF and conductive carbon black, stirring uniformly, and then adding LiFe0.9Mn0.1PO4(ii) a The LiFe0.9Mn0.1PO4The average particle size is 0.9 mu m, and the second slurry is obtained by uniformly stirring, wherein the mass ratio of the LiFe to the first slurry is0.9Mn0.1PO4: CMC: PVDF: conductive carbon black 100:4:4: 8;
4) coating and drying first slurry and second slurry on an aluminum foil, wherein the coating thickness ratio of the first slurry to the second slurry is 8:2, and obtaining the anode;
5) adding deionized water into a stirring kettle, then adding SBR and conductive carbon black, uniformly stirring, and then adding natural graphite to obtain negative electrode slurry, wherein the natural graphite: SBR: conductive carbon black 100:4: 4;
6) coating and drying the negative electrode slurry on the copper foil to obtain the negative electrode;
7) laminating a positive electrode, a diaphragm and a negative electrode into a battery cell, placing the battery cell in a shell, and injecting electrolyte, wherein the content of PST in the electrolyte is 1.5 volume percent, and the content of MMDS is 2.1 volume percent;
8) charging to 3.25V at a constant current of 0.05C;
9) performing constant current charge and discharge at 0.02C between 3.25V and 3.45V for 5 times;
10) charging to 4.25V at constant current of 0.05C, and then charging at constant voltage of 4.25V until the charging current is less than 0.01C;
11) and performing 0.05C constant-current charge and discharge circulation for 3 times between 4.25V and 2.75V to obtain the battery.
Comparative example 1
LiMn as described in step 1)0.83Co0.15Al0.02O2The average particle diameter is 3.0 mu m, and the LiFe0.9Mn0.1PO4The average particle size is 2 μm; said LiFe in step 3)0.9Mn0.1PO4The average particle size was 2 μm, and the other process parameters were the same as in example 3.
Comparative example 2
The first slurry contains only LiMn0.83Co0.15Al0.02O2The other process parameters were the same as in example 3.
Comparative example 3
The coating thickness ratio of the first slurry to the second slurry is 10:0, that is, the positive electrode is obtained by coating all the first slurry, and other process parameters are the same as those in example 3.
Comparative example 4
The electrolyte only contains PST, and other process parameters are the same as those of the embodiment 3.
Comparative example 5
The electrolyte only contains MMDS, and other process parameters are the same as those of the embodiment 3.
Comparative example 6
The electrolyte contains 1.5 volume percent of PST and 3 volume percent of MMDS, and other process parameters are the same as those in example 3.
Comparative example 7
The formation process is carried out for 3 times by carrying out 0.05C constant current charge-discharge circulation between 4.25V and 2.75V, and other parameters are the same as those of the embodiment 3.
Experiment and data
The capacity of the batteries respectively obtained according to the formation methods of examples 1 to 3 and comparative examples 1 to 7 was measured, and then the batteries were subjected to charge and discharge cycles at 0.5C rate at normal temperature and high temperature of 50 ℃ for 100 times to calculate the capacity retention rate, and the results are shown in the following table. Therefore, the structural arrangement and the particle size selection of the material have great influence on the cyclicity; the selection and the proportion of the additive have obvious effect of improving the high-temperature performance; and the formation process can further promote the improvement of the cycle performance.
TABLE 1
|
At normal temperature%
|
High temperature%
|
Example 1
|
98.1
|
95.2
|
Example 2
|
97.5
|
95.4
|
Example 3
|
98.6
|
96.0
|
Comparative example 1
|
92.1
|
90.2
|
Comparative example 2
|
86.4
|
82.1
|
Comparative example 3
|
85.3
|
80.1
|
Comparative example 4
|
88.9
|
84.5
|
Comparative example 5
|
90.2
|
86.4
|
Comparative example 6
|
89.2
|
85.9
|
Comparative example 7
|
94.5
|
92.1 |
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention.