CN111029581B - Positive electrode slurry and preparation method thereof, positive plate and preparation method thereof, lithium ion battery and application thereof - Google Patents
Positive electrode slurry and preparation method thereof, positive plate and preparation method thereof, lithium ion battery and application thereof Download PDFInfo
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Abstract
The invention relates to the field of batteries, and particularly provides a positive electrode slurry capable of improving coating and baking cracking and a preparation method thereof, wherein the positive electrode slurry contains a positive electrode active material, a conductive agent, a dispersing agent, a binder, a solvent, an additive and an optional pH regulator, and the additive is one or more of C2-C10 alkylene oxide, C1-C10 liquid fat, C1-C10 liquid alcohol and N-ethyl pyrrolidone. The invention provides a positive plate and a preparation method thereof. The invention provides a lithium ion battery and application thereof. The slurry can effectively improve the occurrence of the cracking condition and the black spot of the pole piece in the process of coating the battery anode.
Description
Technical Field
The invention relates to a positive electrode slurry and a preparation method thereof, a positive plate and a preparation method thereof, and a lithium ion battery and application thereof.
Background
In the current new energy automobile, 50% of the cost comes from the power battery pack of the automobile, and along with the gradual decline of the national support force for the new energy automobile, the landslide of the subsidy force can further promote the industry cost to shift to the middle and lower reaches of the industry, so how to improve the production efficiency and reduce the production cost under the condition of ensuring the electrical property and the safety performance of the battery is the problem to be solved urgently in the current battery enterprises. The current lithium iron phosphate and ternary system pulping both utilize N-methyl pyrrolidone as a solvent, then a conductive agent, an adhesive and a dispersant are added and fully stirred for several hours, then an active substance is added and stirred at a high speed, finally, the pulp is mixed to the viscosity of 6000-12000/pa.s, the solid content is 40-70%, and then the pulp is coated.
The method is a method used in large area in each battery factory at present, and has the advantages of high production stability, low cost, easy recovery and treatment of the used solvent, no environmental pollution and the like. However, the slurry prepared by the current method is easy to be coated in the slurry inner layer due to the uneven heating of the slurry surface layer and the slurry inner layer in the coating process of the sheet making, the drying rate is inconsistent, the surface layer is dried more quickly, and the slurry inner layer is slower. Under the condition that the toughness of a surface coating film is poor, the increase of pressure can finally cause the baking crack and black spots of the pole piece along with the increase of gas, and the condition is more serious along with the increase of the density of the coating surface of the pole piece and the reduction of the thickness of a current collector. If the coating rupture pole piece is used in the battery, the powder falling phenomenon can occur, and the adverse effect is caused on the cycle performance, the electrical performance and the safety performance of the battery. Therefore, the cracked pole piece is generally scrapped as a defective product, the yield of the pole piece is greatly reduced, the production efficiency is reduced, and the improvement of the energy density of the battery in the later period is influenced.
Disclosure of Invention
The invention aims to reduce the drying time difference of the surface layer and the inner layer of coating slurry and improve the toughness of the surface of a coating film to improve the baking crack condition of a pole piece and improve the production efficiency by adding a special positive electrode slurry additive and the like under the conditions of not influencing the electrical performance and the safety performance of a battery and not reducing the energy density of the battery.
In order to achieve the above object, in one aspect, the present invention provides a positive electrode slurry capable of improving coating crack, the positive electrode slurry comprising a positive electrode active material, a conductive agent, a dispersant, a binder, a solvent, an additive and optionally a pH adjuster, wherein the additive is one or more of C2-C10 alkylene oxide, C1-C10 liquid ester, C1-C10 liquid alcohol and N-ethylpyrrolidone.
In a second aspect, the present invention provides a method of preparing the positive electrode slurry according to the present invention, the method comprising:
the positive electrode active material, the conductive agent, the dispersing agent, the binder, the optional pH regulator, the solvent and the additive are uniformly mixed and dispersed at the temperature below 0 ℃ and within 35 ℃ to obtain slurry.
In a third aspect, the present invention provides a method for preparing a positive electrode sheet, wherein the method comprises:
(1) Preparing positive electrode slurry according to the preparation method;
(2) And coating the positive electrode slurry on a positive electrode current collector, drying, rolling and punching to obtain the positive plate.
In a fourth aspect, the invention provides a positive plate prepared by the preparation method.
In a fifth aspect, the present invention provides a lithium ion battery, comprising: the plastic film comprises a positive plate, a negative plate, a diaphragm, electrolyte, a positive tab, a negative tab and a plastic film.
In a sixth aspect, the invention provides an application of the lithium ion battery in a new energy automobile.
According to the invention, the additive is added to prepare the anode slurry, and the occurrence of the baking crack condition and black spots of the pole piece can be effectively improved in the process of coating the battery anode.
The special additive added in the invention is completely volatilized with the organic solvent under high-temperature baking in the coating process, and the energy density, the electrical property and the safety performance of the later-stage battery cell are not influenced.
According to the method for preparing the anode slurry, the anode slurry is uniformly coated in the sheet-making process, so that the performance of the anode sheet can be effectively improved, and the performance of the lithium ion battery is improved.
Drawings
FIG. 1 is a graphical representation of surface film face cracking for comparative example 1;
FIG. 2 is a graphical representation of the surface film face cracking of example 1;
FIG. 3 is a graphical representation of the surface film face cracking of comparative example 2;
FIG. 4 is a graphical representation of surface film face cracking for example 2;
FIG. 5 is a graphical representation of the surface film face cracking of comparative example 3;
FIG. 6 is a graphical representation of surface film face cracking for example 3;
FIG. 7 is a graphical representation of surface film face cracking for comparative example 4;
FIG. 8 is a graph showing the surface film surface cracking of example 4;
FIG. 9 is a graphical representation of surface film face cracking for comparative example 5;
FIG. 10 is a graphical representation of surface film face cracking for example 5;
FIG. 11 is a comparison of 45 ℃ 1C/1C cycles of cells made from intact and cracked sheets;
FIG. 12 is a comparison of the 25 ℃ 1C/1C cycle of cells made from intact and cracked sheets.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a positive electrode slurry capable of improving coating crack, which contains a positive electrode active material, a conductive agent, a dispersing agent, a binder, a solvent, an additive and optionally a pH regulator, and is characterized in that the additive is one or more of C2-C10 alkylene oxide, C1-C10 liquid ester, C1-C10 liquid alcohol and N-ethyl pyrrolidone.
According to the present invention, the positive electrode slurry solute preferably contains, by mass, 89 to 98.4% of a positive electrode active material, 1 to 8% of a conductive agent, 0.1 to 0.5% of a dispersant, 0.5 to 2% of a binder, and 0 to 0.5% of a pH adjuster.
According to the present invention, it is preferable that the total content X of the solvent and the additive in the positive electrode slurry is 30 to 60%, the content a of the solvent is 20 to 58%, and the content X-a of the additive. According to the formula, the coating performance of the slurry can be further improved, so that the performance of the positive plate can be finally improved.
According to the invention of the additive category of wide choice, preferably the additive is ethylene oxide, butylene oxide, N-ethyl pyrrolidone (NEP), gamma-carboxyl butyric acid lactone, alpha acetyl gamma butyric acid lactone (ABL) and 1,2-octanediol in one or more.
According to the present invention, the selectable range of the solvent is wide, and for the present invention, the solvent is preferably one or more of NMP, ethanol, ethylene glycol and glycerol.
According to the invention, the dispersant is widely available, and for the purposes of the invention, the dispersant is preferably polyvinylpyrrolidone.
According to the invention, the conductive agent has a wide selection range, and according to the invention, the conductive agent is, for example, a graphite conductive material, and according to the invention, the conductive agent is preferably one or more of graphite conductive materials such as carbon black, carbon nanotubes and graphene.
According to the invention, the binder can be selected from a wide range, such as one or more of polyvinylidene fluoride and its homopolymer and copolymer, vinylidene fluoride and its homopolymer, hexafluoropropylene and its copolymer, and for the invention, preferably, the binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride homopolymer, polyvinylidene fluoride copolymer, vinylidene fluoride acetylene, vinylidene fluoride homopolymer, hexafluoropropylene and hexafluoropropylene copolymer.
According to the present invention, the selectable range of the positive electrode active material is wide, and for the present invention, the positive electrode active material is preferably one or more of lithium iron phosphate, a ternary material 111, a ternary material 523, a ternary material 622, and a ternary material 811.
According to the invention, the pH regulator can be selected from a wide range, and for the purposes of the invention, oxalic acid is preferred. Oxalic acid is used as the pH regulator of the invention, and the performance of the positive plate can be improved by combining the additive used by the invention.
According to the present invention, there is provided a method of preparing the positive electrode slurry according to the present invention, the method comprising:
the positive electrode active material, the conductive agent, the dispersing agent, the binder, the optional pH regulator, the solvent and the additive are uniformly mixed and dispersed at the temperature below 0 ℃ and within 35 ℃ to obtain slurry.
According to the present invention, it is preferable that the method further comprises adjusting the viscosity of the slurry to 6000 to 12000 mpa-s with the use of the solvent, and the solid content is 40 to 70% by weight.
According to the invention, the method preferably comprises:
d1, uniformly mixing and dispersing the positive active material, the first part of additive and the first part of solvent to obtain first slurry;
d2, uniformly mixing and dispersing the binder, the conductive agent, the dispersing agent, the second part of additive and the second part of solvent to obtain second slurry;
and d3, mixing the first slurry and the second slurry, adding a pH regulator, mixing and stirring to ensure that the pH value of the slurry is 7-11, the viscosity is 6000-12000mpa · s, and the solid content is 40-70%.
According to the method for preparing the anode slurry, the anode slurry is uniformly coated in the sheet-making process, so that the performance of the anode sheet can be effectively improved, and the performance of the lithium ion battery is improved.
According to the invention, the first portion of additives is preferably used in an amount of 20 to 40% by weight and the second portion of additives in an amount of 60 to 80% by weight, based on the total weight of the additives.
According to the present invention, it is preferred that the first portion of solvent is used in an amount of 60 to 80 wt% and the second portion of solvent is used in an amount of 20 to 40 wt%, based on the total weight of the solvents.
According to the present invention, it is preferable that the adjustment of the viscosity of the slurry using the solvent can improve the performance of the positive electrode sheet, thereby improving the performance of the lithium ion battery.
According to the invention, in order to disperse uniformly, the low-speed stirring and the high-speed stirring can be carried out firstly, the low-speed stirring revolution and the dispersion rotation speed are 0-1000r/min, and the high-speed stirring revolution and the dispersion rotation speed are 1000-3000r/min.
According to the invention, the whole batching process is preferably carried out below 0 ℃, wherein the dew point refers to the temperature at which the air is cooled to saturation under the condition that the moisture content in the air is unchanged and the air pressure is kept constant.
According to the invention, the circulation cooling is preferably started in the whole ingredient stirring process, so that the temperature of the slurry is ensured to be below 35 ℃.
According to the present invention, it is preferable that the slurry be stored at room temperature in a vacuum environment.
According to the present invention, it is preferable that the positive electrode slurry of the present invention is coated within 18 hours.
The invention provides a preparation method of a positive plate, which comprises the following steps:
(1) Preparing positive electrode slurry according to the preparation method;
(2) And coating the positive electrode slurry on a positive electrode current collector, drying, rolling and punching to obtain the positive plate.
The method for preparing the positive electrode slurry can improve the positive electrode plate, thereby improving the performance of the lithium ion battery as the positive electrode of the lithium ion battery.
The invention provides a positive plate prepared by the preparation method.
The present invention provides a lithium ion battery, comprising: the plastic film comprises a positive plate, a negative plate, a diaphragm, electrolyte, a positive tab, a negative tab and a plastic film.
The invention provides application of the lithium ion battery in a new energy automobile.
When the lithium ion battery is used as a new energy automobile battery, the lithium ion battery has the advantages of long cycle service life, low self-discharge, good safety performance and the like.
The present invention will be described in detail below by way of examples. In the following examples, the parameters were obtained by reference to the latest national standard measurement method.
In the invention, the battery cell raw material is a product sold by the company under the brand number of IMP06160230p 29B.
Example 1
Preparation method and application of lithium ion positive electrode slurry for preventing coating and baking cracking of lithium ions
(1) Adding NMP solvent accounting for 25% of the mass of the slurry, ethylene oxide accounting for 5% of the mass of the slurry, SUPER-LI conductive agent accounting for 2% of the mass of the solute, bonding agent FL2100 accounting for 1.5% of the mass of the solute and polyvinylpyrrolidone K30 dispersing agent accounting for 0.1% of the mass of the solute into a stirring cylinder;
(2) Stirring the slurry at a low speed for 20min, fully soaking the solutes, and then stirring at a high speed for 3h to fully disperse the conductive agent, the dispersing agent, the coating improvement additive and the adhesive in the slurry to obtain a mother solution;
(3) After the mother solution is uniformly dispersed, adding a lithium iron phosphate positive active material with the solute mass of 96.4%, stirring at a low speed for 30min to fully soak the active material, and then stirring at a high speed;
(4) Stirring the slurry for 3 hours, then measuring the viscosity, the fineness and the solid content of the slurry, and then adding a solvent NMP to adjust the viscosity of the slurry to 6230mpa · s, the solid content to 53.2 percent and the fineness to 60 mu m;
(5) And (4) vacuumizing the slurry, stirring at a low speed for 30min, and stirring at a low speed in vacuum for storage until the slurry is discharged and coated.
Wherein the low-speed stirring revolution and dispersion rotating speed is 500r/min, and the high-speed stirring revolution and dispersion rotating speed is 1500r/min.
Wherein, the whole batching process is carried out below the dew point of 0 ℃ of the environmental humidity.
Wherein, the cooling system is required to be started in the stirring cylinder in the whole stirring process, so as to ensure that the temperature of the slurry is 25-35 ℃.
Wherein the prepared slurry needs to be stored at normal temperature in a vacuum environment.
Wherein, the viscosity is measured by a 4# rotor at 30r/min.
Comparative example 1
The procedure is as in example 1 except that ethylene oxide, the coating improving additive, is not added in step (1), and the solvent is NMP.
Example 2
Preparation method and application of lithium ion coating and cracking prevention lithium ion positive electrode slurry
(1) Adding a solvent NMP accounting for 25% of the mass of the slurry into a stirring cylinder, coating a solvent accounting for 8% of the mass of the slurry with an improvement additive of butylene oxide, 1% of the mass of solute SUPER-LI, 1% of conductive agent CNTS, 1.5% of the mass of solute with a binder PVDF5130, 0.2% of solute with a dispersant K30 and 0.2% of solute with a pH regulator of oxalic acid;
(2) Stirring the slurry at a low speed for 20min, fully soaking the solutes, then stirring at a high speed for 3h to fully disperse the conductive agent, the dispersing agent, the coating improvement additive, the adhesive and the oxalic acid in the slurry to obtain a mother solution;
(3) After the mother liquor is uniformly dispersed, adding lithium iron phosphate anode active substance with the solute mass of 96.1%, stirring at low speed for 30min to fully soak the active substance, and then stirring at high speed.
(4) Stirring the slurry for 3 hours, then measuring the viscosity, the fineness and the solid content of the slurry, and then adding a solvent NMP to adjust the viscosity of the slurry to 6127mpa · s, wherein the solid content is 51.9 percent and the fineness is 60 mu m.
(5) And (4) vacuumizing the slurry, stirring at a low speed for 30min, and stirring at a low speed in vacuum for storage until the slurry is discharged and coated.
Wherein the low-speed stirring revolution and dispersion rotating speed is 500r/min, and the high-speed stirring revolution and dispersion rotating speed is 2000r/min.
Wherein, the whole batching process is carried out below the dew point of 0 ℃ of the environmental humidity.
Wherein, the cooling system is required to be started in the stirring cylinder in the whole stirring process, so as to ensure that the temperature of the slurry is 25-35 ℃.
Wherein the prepared slurry needs to be stored at normal temperature in a vacuum environment.
Wherein, the viscosity is measured by a 4# rotor at 30r/min.
Comparative example 2
The procedure is essentially the same as in example 2, except that in step (1), no coating-improving additive, butylene oxide, is added, and all are solvent NMP.
Example 3
(1) Adding a solvent ethylene glycol of 28% by mass of the slurry into a stirring cylinder, adding a solvent coating improving additive NEP of 5% by mass of the slurry, SUPER-LI of 1% by mass of the solute, 1% VGCF, a conductive agent of 0.5% ECP-600, a binder of 1.5% by mass of the solute FL2100, a dispersant of 0.3% by mass of the solute K30, and a pH adjusting agent of 0.1% by mass of the solute oxalic acid;
(2) Stirring the slurry at a low speed for 20min, fully soaking the solutes, and then stirring at a high speed for 3h to fully disperse the conductive agent, the dispersing agent, the coating improvement additive, the adhesive and the oxalic acid in the slurry to obtain a mother solution;
(3) After the mother liquor is uniformly dispersed, adding a ternary 523 positive active substance with the mass of 95.6 percent of the dry powder, stirring at a low speed for 30min to fully soak the active substance, and then stirring at a high speed;
(4) And (3) stirring the slurry for 3 hours, and then measuring the viscosity, the fineness and the solid content of the slurry. Then adding a solvent ethylene glycol to adjust the viscosity of the slurry to 6893mpa & s, wherein the solid content is 66.5 percent, and the fineness is 40 mu m;
(5) Vacuumizing the slurry, stirring at a low speed for 30min, and stirring at a low speed for storage until the slurry is discharged and coated;
wherein, the low-speed stirring revolution and the dispersion rotation speed are 500r/min, and the high-speed stirring revolution and the dispersion rotation speed are 1500r/min;
wherein, the whole batching process is carried out below the dew point of 0 ℃ of the environmental humidity;
wherein, the cooling system is required to be started in the stirring cylinder in the whole stirring process to ensure that the temperature of the slurry is 25-35 ℃;
wherein the prepared slurry needs to be stored at normal temperature in a vacuum environment;
wherein, the viscosity is measured by a 4# rotor at 30r/min.
Comparative example 3
The procedure is as in example 3 except that in step (1) no coating-improving additive is added, all being solvent ethylene glycol.
Example 4
(1) Adding SUPER-LI with solute mass of 1%, 1% CNTS, 0.3% ABG1010, 0.7% ECP-600 conductive agent, 1.5% binder PVDF5130 with solute mass, 0.3% dispersant K30 with solute mass, 0.2% pH regulator with solute mass of oxalic acid, 95% ternary 523 positive electrode active material into a stirring cylinder;
(2) The solute is stirred for 3 hours in a low-speed dry mixing mode, the solvent ethylene glycol accounting for 20 percent of the mass of the slurry is added, the solvent coating improving additive gamma-carboxyl butyrate lactone accounts for 10 percent of the mass of the slurry, the low-speed stirring mode is carried out for 30 minutes to enable the solute to be fully soaked, and then the high-speed stirring mode is carried out;
(3) And (3) stirring the slurry for 3 hours, and then measuring the viscosity, the fineness and the solid content of the slurry. Then, adding a solvent ethylene glycol to adjust the viscosity of the slurry to 7160mpa & s, wherein the solid content is 66.3 percent, and the fineness is 40 mu m;
(4) After the slurry is vacuumized and stirred at a low speed for 30min, the slurry is stirred at a low speed in vacuum and stored until the slurry is discharged and coated;
wherein the low-speed stirring revolution and dispersion rotating speed is 500r/min, and the high-speed stirring revolution and dispersion rotating speed is 2000r/min;
wherein, the whole batching process is carried out below the dew point of 0 ℃ of the environmental humidity;
wherein, the cooling system is required to be started in the stirring cylinder in the whole stirring process to ensure that the temperature of the slurry is 25-35 ℃;
wherein the prepared slurry needs to be stored at normal temperature in a vacuum environment;
wherein, the viscosity is measured by a 4# rotor at 30r/min.
Comparative example 4
The embodiment is substantially the same as example 4 except that no coating-improving additive is added in step (2), and all is solvent ethylene glycol.
Example 5
Preparation method and application of lithium ion positive electrode slurry for preventing coating and baking cracking of lithium ions
(1) Adding a solvent glycerol accounting for 15% of the mass of the slurry into a No. 1 stirring cylinder, coating a ternary 811 positive electrode active substance which improves the ABL and solute accounting for 93.5% of the mass of the additive and is coated by the solvent accounting for 3% of the mass of the slurry, stirring at a low speed for 30min, and then stirring at a high speed for 2h to obtain a first slurry;
(2) Adding glycerol solvent 5% of the mass of the slurry, 5% of solvent coating improvement additive 1,2-octanediol of the mass of the slurry, 1% of solute mass SUPER-LI, 2% of CNTS, 1% of ECP-600, 0.5% of conductive agent of graphene, 1.5% of binder PVDF5130 of solute mass and 0.2% of dispersant K30 of solute mass into a No. 2 stirring cylinder, stirring at a low speed for 30min and then stirring at a high speed for 2h to obtain a second slurry;
(3) Mixing the first slurry and the second slurry in equal mass; adding oxalic acid pH regulator with solute mass of 0.3%, mixing and stirring for 30min to make the pH value of the slurry be 9;
(4) And (3) stirring the slurry for 2 hours, and then measuring the viscosity, the fineness and the solid content of the slurry. Then adding a solvent of glycerol to adjust the viscosity of the slurry to 7348mpa · s, wherein the solid content is 69.8 percent, and the fineness is 40 mu m;
(5) Vacuumizing the slurry, stirring at a low speed for 30min, and stirring at a low speed for storage until the slurry is discharged and coated;
wherein the low-speed stirring revolution and dispersion rotating speed is 500r/min, and the high-speed stirring revolution and dispersion rotating speed is 2000r/min;
wherein, the whole batching process is carried out below the dew point of the environmental humidity of 0 ℃;
wherein, the cooling system is required to be started in the stirring cylinder in the whole stirring process to ensure that the temperature of the slurry is 25-35 ℃;
wherein the prepared slurry needs to be stored at normal temperature in a vacuum environment;
wherein, the viscosity is measured by a 4# rotor at 30r/min.
Comparative example 5
The procedure is as in example 5, except that no coating-improving additive is added in steps (1) and (2), and all the additives are solvent glycerol.
Comparing the surface film crack of the coating of the positive electrode plate prepared in examples 1,2, 3, 4 and 5 with those of comparative examples 1,2, 3, 4 and 5, specifically, refer to fig. 1 (comparative example 1) to fig. 2 (example 2), fig. 3 (comparative example 2) to fig. 4 (example 2), fig. 5 (comparative example 3) to fig. 6 (example 3), fig. 7 (comparative example 4) to fig. 8 (example 4), and fig. 9 (comparative example 5) to fig. 10 (example 5). Fig. 1-10 are all pictures taken after 30 times magnification by using an imager.
The comparison shows that: the pole piece film surfaces obtained in the comparative examples 1 to 5 have cracks, and the pole piece film surfaces in the examples 1 to 5 have no cracks. Therefore, the situation of film surface cracks can be effectively improved by adding the additive, and the supposition is that the positive electrode slurry without the additive is coated on the current collector, the coating surface layer has high temperature with the external contact surface, the toughness of the coating film surface is gradually weakened along with the increase of the drying degree, so that the internal volatile gas overflows and difficultly cracks on the surface layer, and cracks are formed.
The following table 1 shows the comparison of self-discharge data of cell manufactured in examples and comparative examples at 25 ℃ 50% SOC 35 day test period (positive plate of the manufactured cell is manufactured by coating a pair of roll punching sheets with positive material ratio corresponding to the examples and comparative examples, negative plate is manufactured by coating a pair of roll punching sheets with graphite, conductive agent, thickening agent and adhesive according to a certain ratio, baking the positive and negative plates for a certain time to reach the moisture standard, coating Tao Gemo lamination sheets with corresponding size and thickness of 16 mu m (12 + 4), welding the tabs with high temperature glue, and packaging with aluminum plastic film with corresponding size and thickness of 152 mu m, wherein the electrolyte is PC, EC, DEC, DMC, liPF according to a certain ratio 6 The organic solution is activated, converted, aged and subjected to Degas-volume separation to obtain the battery cell. All the materials used in the cells of the manufactured examples and comparative examples except the positive electrode are consistent, and all the process parameters are also consistent).
The self-discharge test method comprises the following steps:
1. after the cell is subjected to capacity grading, constant-current and constant-voltage charging is carried out until the cell is fully charged (constant-current discharging, constant-current and constant-voltage charging, constant-current discharging and constant-current and constant-voltage charging), the voltage range is 2.75-4.3V, the current is 0.33C, and the constant-voltage cutoff current is 0.05C;
2. calibrating according to the capacity of the cell, adjusting the constant current discharge of 0.33C to 50% SOC;
3. placing the split-capacity battery cell into a constant temperature box at 25 ℃ and 35 ℃ for storage, measuring the voltage of the battery cell after 35 days, and measuring the precision of a measuring instrument to be 0.01mV;
4. where 1C is the magnitude of current required to discharge the cell 1h, SOC is the cell state of charge, and 50% is the SOC, i.e., half-state of charge.
The battery cell circulating discharge test method comprises the following steps:
1, putting a cell on a clamping plate, applying a pressure of 5N/m, and then placing the cell in a constant temperature room at 25 ℃/45 ℃ for 1C/1C circulation (constant current and constant voltage charging and constant current discharging), wherein the voltage range is 2.75-4.3V;
and 2, taking the capacity average value of 5 circles before as the calibration capacity, calculating the capacity retention, and charging and discharging once by using 0.33C/0.33C instead of 49 circles per cycle until the cycle is stopped until the battery cell capacity is retained at 80%.
FIGS. 11 to 12 are graphs showing the comparison of the cycle life of the battery cells obtained in example 5 and comparative example 5 at ambient temperatures of 25 ℃ and 45 ℃, the cycle voltage range of 2.75V to 4.3V, and the charge/discharge current of 1C/1C (CV-CC).
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
TABLE 1
Wherein the sample number refers to the sample number of the test.
Claims (12)
1. A positive electrode slurry capable of improving coating crack, which contains a positive electrode active material, a conductive agent, a dispersant, a binder, a solvent, and an additive,
the additive is one or more of ethylene oxide, butylene oxide, gamma-carboxyl butyrate lactone, alpha-acetyl-gamma butyrate lactone and 1,2-octanediol;
the solvent is one or more of ethanol, glycol and glycerol;
in the positive electrode slurry, the total content X of the solvent and the additive is 30-60%, the content a of the solvent is 20-58%, and the content of the additive is X-a.
2. The positive electrode slurry according to claim 1, further comprising a pH adjuster.
3. The positive electrode slurry according to claim 2, wherein the positive electrode slurry solute contains, by mass, 89 to 98.4% of the positive electrode active material, 1 to 8% of the conductive agent, 0.1 to 0.5% of the dispersant, 0.5 to 2% of the binder, 0 to 0.5% of the pH adjuster, and 3 to 8% of the additive.
4. The positive electrode slurry according to claim 2 or 3, wherein the dispersant is polyvinylpyrrolidone;
the conductive agent is one or more of carbon black, carbon nano tubes and graphene;
the binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride homopolymer, polyvinylidene fluoride copolymer, vinylidene fluoride acetylene homopolymer, hexafluoropropylene and hexafluoropropylene copolymer;
the positive active material is one or more of lithium iron phosphate, a ternary material 111, a ternary material 523, a ternary material 622 and a ternary material 811;
the pH regulator is oxalic acid.
5. A method for producing the positive electrode slurry according to any one of claims 1 to 4, comprising: the positive active material, the conductive agent, the dispersant, the binder, the solvent and the additive are uniformly mixed and dispersed at the dew point of 0 ℃ or below and the temperature of 35 ℃ to obtain slurry.
6. The method of claim 5, further comprising adjusting the viscosity of the slurry to 6000-12000 mpa-s with the solvent to a solids content of 40-70 wt%.
7. The method of claim 5 or 6, wherein the method comprises:
d1, uniformly mixing and dispersing the positive active material, the first part of additive and the first part of solvent to obtain first slurry;
d2, uniformly mixing and dispersing the binder, the conductive agent, the dispersing agent, the second part of additive and the second part of solvent to obtain second slurry;
and d3, mixing the first slurry and the second slurry, adding a pH regulator, mixing and stirring to ensure that the pH value of the slurry is 7-11, the viscosity is 6000-12000mpa · s, and the solid content is 40-70 wt%.
8. The method of claim 7, wherein,
based on the total weight of the additives, the first part of additives is used in an amount of 20-40 wt%, and the second part of additives is used in an amount of 60-80 wt%;
the first portion of solvent is present in an amount of 60 to 80 wt% and the second portion of solvent is present in an amount of 20 to 40 wt%, based on the total weight of the solvents.
9. A method for preparing a positive electrode plate, wherein the method comprises the following steps:
(1) Preparing a positive electrode slurry according to the production method described in any one of claims 5 to 8;
(2) And coating the positive electrode slurry on a positive electrode current collector, drying, rolling and punching to obtain the positive plate.
10. A positive electrode sheet produced by the production method according to claim 9.
11. A lithium ion battery, the lithium ion battery comprising: the positive plate, the negative plate, the diaphragm, the electrolyte, the positive tab, the negative tab and the plastic film, wherein the positive plate is the positive plate of claim 10.
12. The use of the lithium ion battery of claim 11 in a new energy vehicle.
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| PCT/CN2020/128379 WO2021093810A1 (en) | 2019-11-14 | 2020-11-12 | Positive electrode slurry and preparation method therefor, positive electrode sheet and preparation method therefor, lithium ion battery and use thereof, and cell |
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| CN111029581B (en) * | 2019-11-14 | 2023-03-10 | 孚能科技(赣州)股份有限公司 | Positive electrode slurry and preparation method thereof, positive plate and preparation method thereof, lithium ion battery and application thereof |
| CN111584861B (en) * | 2020-05-18 | 2022-02-22 | 蜂巢能源科技有限公司 | Cobalt-free system, positive electrode slurry, homogenizing method and application thereof |
| CN111710868A (en) * | 2020-06-30 | 2020-09-25 | 昆山宝创新能源科技有限公司 | High-alkalinity anode slurry and preparation method and application thereof |
| CN112652801B (en) * | 2020-12-23 | 2022-03-18 | 深圳市言九电子科技有限公司 | Button battery roll core, preparation method thereof and button battery using same |
| CN113410462B (en) * | 2021-05-27 | 2022-06-14 | 东莞赣锋电子有限公司 | Additive for lithium ion battery positive electrode, positive electrode slurry using same and preparation method thereof |
| CN114361378B (en) * | 2021-12-14 | 2024-03-29 | 宁德厦钨新能源材料有限公司 | Electrochemical performance detection method for ternary material |
| CN114864871B (en) * | 2022-03-31 | 2024-04-02 | 湖北亿纬动力有限公司 | Positive electrode slurry and preparation method and application thereof |
| CN114927691A (en) * | 2022-05-20 | 2022-08-19 | 上海瑞浦青创新能源有限公司 | Ternary positive electrode slurry, preparation method and application in lithium ion battery |
| CN116053476A (en) * | 2023-01-13 | 2023-05-02 | 上海兰钧新能源科技有限公司 | Positive electrode slurry and preparation method and application thereof |
| CN116314803A (en) * | 2023-03-10 | 2023-06-23 | 东莞格林德能源有限公司 | Positive electrode slurry of sodium ion battery, sodium ion battery and preparation method of sodium ion battery |
| CN117117075B (en) * | 2023-10-23 | 2023-12-29 | 江苏众钠能源科技有限公司 | Pole piece preparation method for regulating compaction density, pole piece and sodium ion battery |
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