CN117936698A - Negative electrode plate of sodium ion battery, evaluation method and preparation method - Google Patents
Negative electrode plate of sodium ion battery, evaluation method and preparation method Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 18
- 238000011156 evaluation Methods 0.000 title abstract description 7
- 239000007773 negative electrode material Substances 0.000 claims abstract description 31
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Abstract
The application discloses a negative electrode plate, an evaluation method and a preparation method of a sodium ion battery, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode membrane, the negative electrode membrane comprises a negative electrode active material, the negative electrode plate satisfies 0.05-0.4 of (I-PD)/D v50, wherein I=C Constant current /C Total (S) ,C Total (S) ＝C Constant current +C Constant pressure ;C Constant current is a first discharge capacity measured by discharging a button half battery to 0V under a constant current of 0.1C, and C Constant pressure is a second discharge capacity measured by discharging the button half battery to a current of 10 mu A under a constant voltage of 0V; the button type half cell comprises a negative pole piece; PD is the compacted density of the negative electrode membrane; d v50 is the median particle diameter of the anode active material. According to the application, the constant current section capacity ratio in the sodium ion battery is analyzed, and the compaction density and the median particle diameter of the negative electrode membrane are combined, so that the speed of sodium ion migration is improved, and the negative electrode plate of the sodium ion battery with better multiplying power and cycle performance is obtained.
Description
Technical Field
The application relates to the technical field of sodium ion batteries, in particular to a negative electrode plate of a sodium ion battery, an evaluation method and a preparation method.
Background
The sodium ion battery has greater advantages in a future large-scale energy storage system due to abundant global sodium resources; and the sodium ion battery can use Propylene Carbonate (PC) -based electrolyte, so that the sodium ion battery is more advantageous to be applied in a low-temperature environment than the lithium ion battery.
Sodium ion batteries also have some disadvantages, for example, the negative electrode plate of the sodium ion battery mostly adopts hard carbon and soft carbon as negative electrode active materials, so that the surface defect of the negative electrode plate negative electrode active materials of the sodium ion battery is more, sodium ions are consumed more, and the first effect of the sodium ion battery is lower than that of the lithium ion battery under the same condition; in addition, the negative pole piece of the sodium ion battery is easy to separate sodium, and the cycle life is reduced.
In view of the above, the application provides a negative electrode plate of a sodium ion battery for improving the cycle performance and the multiplying power performance.
Disclosure of Invention
The application aims to provide a negative electrode piece of a sodium ion battery, an evaluation method and a preparation method, so as to improve the cycle performance and the multiplying power performance of the sodium ion battery.
The application is realized in the following way:
In a first aspect, the application provides a negative electrode plate of a sodium ion battery, comprising a negative electrode current collector and a negative electrode membrane arranged on the surface of the negative electrode current collector, wherein the negative electrode membrane comprises a negative electrode active material, the negative electrode plate satisfies 0.05-0 (I-PD)/D v50 -0.4,
I=c Constant current /C Total (S) , dimensionless, C Total (S) ＝C Constant current +C Constant pressure ; wherein, C Constant current is the first discharge capacity measured by the button half cell discharging to 0V under 0.1C constant current, and C Constant pressure is the second discharge capacity measured by the button half cell discharging to 10 μA under 0V constant voltage; the button half cell comprises the negative electrode piece;
PD is the compacted density of the negative electrode membrane, and the unit is g/cm 3;
D v50 is the median particle diameter of the anode active material in μm.
In an alternative embodiment, the cell is tested at a temperature in the range of 20 ℃ to 30 ℃ first for C Constant current followed by C Constant pressure ;
preferably, the cell is tested at 25℃, followed by test C Constant current Constant pressure ;
Preferably, both C Constant current and C Constant pressure are tested on first discharge.
In an alternative embodiment, the 0.4.ltoreq.I.ltoreq.1, preferably 0.6.ltoreq.I.ltoreq.0.95, more preferably 0.65.ltoreq.I.ltoreq.0.9.
In an alternative embodiment, 0.7g/cm 3≤PD≤1.5g/cm3, preferably 0.9g/cm 3≤PD≤1.1g/cm3.
In an alternative embodiment, 1 μm.ltoreq.D v50.ltoreq.10μm, preferably 4 μm.ltoreq.D v50.ltoreq.6μm.
In an alternative embodiment, the negative active material includes amorphous carbon; preferably, the amorphous carbon is hard carbon and/or soft carbon;
Preferably, the battery is a button type half battery assembled by taking a sodium sheet as a counter electrode and the negative electrode sheet, and the assembling sequence of the button type half battery is positive electrode shell, negative electrode sheet, electrolyte, glass fiber, electrolyte, sodium sheet, gasket, elastic sheet and negative electrode shell.
In an alternative embodiment, the negative electrode sheet satisfies 0.05 +.i. (PD)/D v50 +.0.3; preferably, the negative electrode sheet satisfies 0.1 < 7 > (i×pd)/D v50 < 0.25; preferably, the negative electrode sheet satisfies 0.1 < 7.pd)/D v50 < 0.2.
In a second aspect, the present application provides a performance evaluation method for a negative electrode tab of a sodium ion battery according to any one of the foregoing embodiments, the performance evaluation method including:
Calculating a difference value between the (i×pd)/D v50 and a preset value, wherein the preset value is determined according to the cycle performance of the sodium ion battery and/or the rate performance of the sodium ion battery;
Determining the grade of the negative electrode plate according to the difference value;
Preferably, the preset value is 0.14.
In a third aspect, the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet according to any one of the preceding embodiments.
In a fourth aspect, the present application provides a method for preparing a negative electrode plate of a sodium ion battery according to the foregoing embodiment, wherein the slurry containing the negative electrode active material is coated on the surface of a negative electrode current collector, and the negative electrode plate of the sodium ion battery is obtained after drying.
In an alternative embodiment, the slurry includes a negative electrode active material, a conductive agent, a dispersant, a binder, and water;
preferably, the slurry viscosity is 4800 mPas-5200 mPas;
Preferably, the conductive agent is superconducting carbon black; and/or the conductive agent is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material; and/or, the dispersing agent is sodium carboxymethyl cellulose; and/or the dispersant is added in an amount of 1.2wt.% to 1.8wt.% of the anode active material; and/or, the binder is styrene-butadiene rubber; and/or the binder is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material.
The application has the following beneficial effects:
In the negative electrode membrane of the sodium ion battery, surface defects, intercalation and closed pore filling of an active material can contribute to capacity, C Constant current can reflect the capacity contributed by surface adsorption and intercalation to a certain extent, the capacity contributed by intercalation is more to indicate that sodium ions are easier to embed, the dynamic performance is good, and high-rate quick charge can be realized; the capacity expressed from constant voltage discharge to current of 10 mu A can reflect the capacity of closed cell contribution to a certain extent, the capacity of closed cell contribution can enable sodium ions to be more embedded, the capacity is improved, and the cycle with high capacity and long service life can be realized under low multiplying power. According to the application, the capacity ratio of each stage in the sodium ion battery is analyzed, and meanwhile, the compaction density and the median particle diameter of the negative electrode membrane are combined, so that the speed of sodium ion migration is improved, and the negative electrode plate of the sodium ion battery with better multiplying power and cycle performance is obtained.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
As previously mentioned, sodium ion batteries suffer from several disadvantages, the specific principle of which is as follows: ① The radius of sodium ions is larger than that of lithium ions, and the requirement on the interlayer spacing of the anode material is high. At present, the negative electrode active materials comprise hard carbon, soft carbon, hard carbon, soft carbon and other negative electrode active materials, and the surface defects are more, and sodium ions are consumed more, so that the first effect of the sodium ion battery is lower than that of the lithium ion battery under the same condition. ② Because the sodium intercalation potential of the anode active materials such as hard carbon, soft carbon and the like is close to 0V, the anode plate is easy to separate sodium, and the cycle life is reduced. ③ At present, the capacity of the anode active materials such as hard carbon, soft carbon and the like is mainly improved, but the improvement of the closed pore volume can reduce the defects on the surface of the hard carbon, influence the diffusion of sodium ions on the surface of the hard carbon, and further reduce the quick charge and power performance.
Based on the above problems, the present application provides a negative electrode tab of a sodium ion battery, comprising a negative electrode current collector and a negative electrode membrane disposed on the surface of the negative electrode current collector, the negative electrode membrane comprising a negative electrode active material, the negative electrode tab satisfying 0.05 < i.r.pd)/D v50 < 0.4, wherein,
I=c Constant current /C Total (S) , dimensionless, C Total (S) ＝C Constant current +C Constant pressure ; wherein, C Constant current is the first discharge capacity measured by the button half cell discharging to 0V under 0.1C constant current, and C Constant pressure is the second discharge capacity measured by the button half cell discharging to 10 μA under 0V constant voltage; the button half cell comprises the negative electrode piece;
PD is the compacted density of the negative electrode membrane, and the unit is g/cm 3;
D v50 is the median particle diameter of the anode active material in μm.
The embodiment provides a negative electrode plate of a sodium ion battery, which comprises a negative electrode current collector, wherein the negative electrode current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
The negative electrode membrane in this embodiment includes a negative electrode active material, which may be one or a combination of several of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like, and some negative electrode membranes also include necessary adhesive, dispersant, conductive agent, and the like. The negative electrode film may be disposed on one surface or both opposite surfaces of the negative electrode current collector in this embodiment.
In the negative electrode membrane of the sodium ion battery, surface defects, intercalation and closed pore filling of an active material can all contribute to capacity, C Constant current can reflect the capacity contributed by surface adsorption and intercalation, and the more capacity contributed by intercalation indicates that sodium ions are easier to embed, so that the dynamic performance is good, and high-rate quick charge can be realized; the capacity expressed by the constant voltage discharge to the current of 10 mu A can represent the capacity of closed cell contribution, the capacity of closed cell contribution can enable sodium ions to be more embedded, the capacity is improved, and the cycle with high capacity and long service life can be realized under low multiplying power. According to the application, the sodium ion battery negative electrode plate with better multiplying power and cycle performance is obtained by analyzing the capacity ratio of each stage in the sodium ion battery.
In addition, the compaction density of the negative electrode membrane can influence gaps among particles, and further influence the size, the type and the like of holes in the negative electrode membrane; the size of the median particle size affects the speed of sodium ion migration and thus the stability of the material, and in general, the smaller the particle size, the shorter the path of sodium ion migration and the faster the migration speed. In view of the above, the application combines the compaction density and the median particle diameter of the C Constant current 、C Total (S) 、 negative electrode membrane to obtain the sodium ion battery negative electrode plate with better multiplying power and cycle performance.
It should be noted that, in the present application, I varies with the test temperature, so the test temperature varies, and the values of (i×pd)/D v50 vary slightly, so that, for convenience of testing, I is usually tested at room temperature, i.e., in the temperature range of 20 ℃ to 30 ℃.
Specifically, in this embodiment, the specific value of 0.05+.ltoreq.i.pd/D v50≤0.4,(I*PD)/Dv50 may be any value between 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or 0.05 and 0.4.
In an alternative embodiment, the cell is tested at a temperature in the range of 20 ℃ to 30 ℃ first for C Constant current followed by C Constant pressure ;
preferably, the cell is tested at 25℃, followed by test C Constant current Constant pressure ;
Preferably, both C Constant current and C Constant pressure are tested on first discharge.
In an alternative embodiment, the 0.4.ltoreq.I.ltoreq.1, preferably 0.6.ltoreq.I.ltoreq.0.95, more preferably 0.65.ltoreq.I.ltoreq.0.9. Specifically, I can be any value between 0.4, 0.6, 0.8, 1.0 or 0.4-1, and the surface defect and intercalation stage capacity ratio in the sodium ion battery are reasonably selected.
In alternative embodiments, 0.7g/cm 3≤PD≤1.5g/cm3, preferably 0.9g/cm 3≤PD≤1.1g/cm3, in particular, PD may be any value between 0.7g/cm3、0.8g/cm3、0.9g/cm3、1.0g/cm3、1.1g/cm3、1.2g/cm3、1.3g/cm3、1.4g/cm3、1.5g/cm3 or 0.9g/cm 3～1.5g/cm3.
In alternative embodiments, 1 μm.ltoreq.D v50.ltoreq.10μm, preferably 4 μm.ltoreq.D v50.ltoreq.6μm, in particular, D v50 may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value between 1 μm and 10 μm or 4 μm and 6 μm.
In an alternative embodiment, the negative active material includes amorphous carbon; preferably, the amorphous carbon is hard carbon and/or soft carbon. The capacity of 0.1V or more of a sodium-ion half cell using hard carbon or the like as a negative electrode active material mainly contributes to surface defects, the capacity of 0V to 0.1V or less mainly contributes to intercalation, and the capacity near 0V mainly contributes to closed cell filling.
In an alternative embodiment, the kind of battery has little effect on (i×pd)/D v50. It should be noted that the battery may be tested using other types of batteries other than button type half batteries, and is not limited thereto. Such as a pouch cell.
In an alternative embodiment, the battery is a button type half battery assembled by taking a sodium sheet as a counter electrode and the negative electrode sheet, and the assembling sequence of the button type half battery is positive electrode shell, negative electrode sheet, electrolyte, glass fiber, electrolyte, sodium sheet, gasket, elastic sheet and negative electrode shell.
In an alternative embodiment, the negative electrode sheet satisfies 0.05 +.i. (PD)/D v50 +.0.3; preferably, the negative electrode sheet satisfies 0.1 < 7 > (i×pd)/D v50 < 0.25; preferably, the negative electrode sheet satisfies 0.1 < 7.pd)/D v50 < 0.2.
Another embodiment of the present application provides a method for evaluating the performance of the negative electrode tab of a sodium ion battery according to any one of the foregoing embodiments, the method comprising:
Calculating a difference value between the (i×pd)/D v50 and a preset value, wherein the preset value is determined according to the cycle performance of the sodium ion battery and/or the rate performance of the sodium ion battery;
And determining the grade of the negative electrode plate according to the difference value.
The preset value is usually the value of (i×pd)/D v50 corresponding to the optimal cycling performance or the optimal multiplying power performance of the negative electrode plate or the optimal state after balancing the cycling performance and multiplying power performance; determining the cycle performance and/or the multiplying power performance of the negative electrode plate according to the difference value;
Preferably, the preset value is 0.14.
The inventors found that when the value of the negative electrode tab corresponding to (i×pd)/D v50 is 0.14, the cycle performance and the rate performance are optimal, and the closer the value of the negative electrode tab corresponding to (i×pd)/D v50 is to 0.14, the better the cycle performance and the rate performance are, so the value of (i×pd)/D v50 can be used as a criterion for evaluating the negative electrode tab.
Specifically, a person skilled in the art may calculate the value of the prepared negative electrode sheet (i×pd)/D v50 according to actual needs, and define a range meeting the needs, for example, the value of (i×pd)/D v50 may be defined to be 0.1-0.25 in the case of higher requirements on the cycle performance and the rate performance of the battery product; when the cycle performance and rate performance requirements for the product are not high, the value of (i×pd)/D v50 may be defined as 0.05 to 0.4. Similarly, the product may be classified according to the value of (i×pd)/D v50, for example, when the value of (i×pd)/D v50 is 0.1 to 0.2, it is an first grade product, and when the value of (i×pd)/D v50 is 0.05 to 0.3, it is a second grade product, etc.
In a further embodiment, the present application provides a sodium ion battery comprising a negative electrode sheet according to any one of the preceding embodiments.
The application also provides a preparation method of the negative electrode plate of the sodium ion battery, which is characterized in that the slurry containing the negative electrode active material is coated on the surface of the negative electrode current collector, and the negative electrode plate of the sodium ion battery is obtained after drying.
In an alternative embodiment, the slurry includes a negative electrode active material, a conductive agent, a dispersant, a binder, and water;
In some optional embodiments of the present application, the conductive agent is at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some optional embodiments of the present application, the binder is at least one of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some optional embodiments of the present application, the dispersing agent is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxyethyl cellulose, lithium carboxyethyl cellulose, and polyvinylpyrrolidone.
In some embodiments, the slurry viscosity is 4800 to 5200 mPa-s; specifically, the value may be any value between 4800 mPas, 4900 mPas, 5000 mPas, 5100 mPas, 5200 mPas, or 4800 mPas to 5200 mPas.
In some embodiments, the conductive agent is a superconducting carbon black; and/or the conductive agent is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material, specifically may be any value between 1.5wt.%, 1.7wt.%, 1.9wt.%, 2.1wt.%, 2.3wt.%, 2.5wt.%, or 1.5wt.% to 2.5 wt.%; and/or, the dispersing agent is sodium carboxymethyl cellulose; and/or the dispersant is added in an amount of 1.2wt.% to 1.8wt.% of the anode active material, specifically may be any value between 1.2wt.%, 1.4wt.%, 1.6wt.%, 1.8wt.%, or 1.2wt.% to 1.8 wt.%; and/or, the binder is styrene-butadiene rubber; and/or the binder is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material, specifically may be any value between 1.5wt.%, 1.7wt.%, 1.9wt.%, 2.1wt.%, 2.3wt.%, 2.5wt.%, or 1.5wt.% to 2.5 wt.%.
The features and capabilities of the present application are described in further detail below in connection with the examples.
Example 1
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=300 mAh/g of a button half cell, dv50=5 μm, i=0.85 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (super-p, abbreviated SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (Sodium carboxymethyl cellulose, abbreviated CMC) for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (Polymerized Styrene Butadiene Rubber, abbreviated SBR) and stirring for 6 hours, to finally obtain a negative electrode slurry having a viscosity of about 5000mpa·s.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet to be 8mg/cm 2 in the coating process, passing the coated electrode sheet through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode sheet after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.9g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 2:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity of button half cell=303 mAh/g, dv50=7 μm, i=0.7 of button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 1.0g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 3:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity of button half cell=303 mAh/g, dv50=4 μm, i=0.9 of button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.9g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 4:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=3.2 μm, i=0.85 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.95g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 5:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=6.5 μm, i=0.9 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.9g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 6:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=2.6 μm, i=0.9 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.89g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 7:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=2.3 μm, i=0.9 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.89g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 8:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=1.9 μm, i=0.95 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), stirred for 6 hours, and finally a negative electrode slurry having a viscosity of about 5000mpa·s was obtained.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.8g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Example 9:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=323 mAh/g of a button half cell, dv50=8 μm, i=0.5 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), and stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), and stirring for 6 hours, to finally obtain a negative electrode slurry having a viscosity of about 5000mpa·s.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.8g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Comparative example 1:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=327 mAh/g of a button half cell, dv50=16 μm, i=0.3 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), and stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), and stirring for 6 hours, to finally obtain a negative electrode slurry having a viscosity of about 5000mpa·s.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 0.80g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Comparative example 2:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=246 mAh/g of a button half cell, dv50=8 μm, i=0.2 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), and stirred for 30 minutes, followed by adding 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR), and stirring for 6 hours, to finally obtain a negative electrode slurry having a viscosity of about 5000mpa·s.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 1.10g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Comparative example 3:
The embodiment provides a negative electrode piece of a sodium ion battery, which comprises the following steps:
step 1, preparing anode active material slurry:
6.71kg of a negative electrode active material (first charge specific capacity=246 mAh/g of a button half cell, dv50=2 μm, i=0.9 of the button half cell) was dry-blended with 0.112kg of a superconducting carbon black conductive agent (SP), 0.085kg of a dispersant sodium carboxymethyl cellulose (CMC), stirred for 30 minutes, and then 7.95kg of solvent water and 0.127kg of a binder styrene-butadiene rubber (SBR) were added, stirred for 6 hours, to finally obtain a negative electrode slurry having a viscosity of about 5000mpa·s.
Step 2, manufacturing a negative plate:
Uniformly coating the anode slurry on the front side and the back side of an aluminum foil with the thickness of 8mm, controlling the surface density of a film sheet at 8mg/cm 2 in the coating process, passing the coated pole piece through a 110 ℃ oven with the length of 20m at the speed of 3m/s, and obtaining the anode pole piece after coating and drying.
Step 3, preparation of the soft package battery
The prepared negative electrode plate is rolled (the compacted density of the plate is 1.20g/cm 3), and the cut negative electrode plate and the sodium ion layered oxygen positive electrode plate are assembled and injected to form the battery.
Capacity test: discharging the sodium ion button half cell to 0V at a constant current of 0.1C for the first time at 25 ℃, wherein the capacity of the battery is C Constant current , and the battery is discharged to 10 mu A at a constant voltage of 0V for the first time, and the capacity of the battery is C Constant pressure ; then, the mixture was left for 5 minutes at 0.1C until the charge voltage became 2.0V, and the charge capacity of the button half cell was calculated and represented as C.
Kinetic performance test: the sodium ion batteries prepared in examples and comparative examples were fully charged at 0.5xC (x is a positive integer of 1 to 20) and repeated 20 times at 1C, at 25 ℃, to see the discharge capacity retention rate at the 20 th turn, and the recording capacity retention rate was lower than the rate of 99% (i.e., 0.5x value). The quick charge rate is excellent at 2.5C or higher, and the quick charge rate is generally 1.5C to 2.5C, but the quick charge rate is poor at 1.5C or lower.
And (3) testing the cycle performance: the sodium ion batteries prepared in the examples and the comparative examples were fully charged at 25 ℃ with 1C, 1C discharged to a cut-off voltage, the discharge capacity was recorded as C 1, left for 30min, then 1C/1C charged and discharged, the discharge capacity C 2 was recorded, and the cycle was operated until C n/C1 was less than 0.8, and n was recorded. The larger n, the better the cycle performance. n is greater than 4000 circles and has excellent circulation capability, n ranges from 3000 circles to 4000 circles and is common in circulation capability, and n is less than 3000 circles and has poor circulation capability.
As can be seen from the above table, example 1 and example 2 have a fast charge capacity and cycle life that are relatively excellent with 0.05.ltoreq.I.PD/D v50.ltoreq.0.4. In comparative example 1 (i×pd)/D v50 <0.05, most of the capacity is contributed by intercalation of sodium ions into closed cells, sodium ions form metal clusters in the closed cells, sodium is separated out, dead sodium is formed, and removal is difficult; and the particles are large, the diffusion rate of sodium ions in a solid phase is small, the time for embedding the sodium ions into disordered carbon is long, and the dynamics performance is poor. In examples 6 to 8, the particle size was small, the specific surface area was large, and the side reactions were large, so that the cycle life was relatively short. In comparative example 2, (i×pd)/D v50 >0.4, the main capacity is the surface adsorption and intercalation contribution, but the irreversible capacity is much in the capacity of surface adsorption, resulting in low coulombic efficiency; because of the large interlayer spacing, solvent co-intercalation occurs, causing delamination of the carbon layer, affecting cycle performance.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. The negative electrode plate of the sodium ion battery is characterized by comprising a negative electrode current collector and a negative electrode membrane arranged on the surface of the negative electrode current collector, wherein the negative electrode membrane comprises a negative electrode active material, the negative electrode plate satisfies 0.05-0 (I-PD)/D v50 -0.4,
I=c Constant current /C Total (S) , dimensionless, C Total (S) ＝C Constant current +C Constant pressure ; wherein, C Constant current is the first discharge capacity measured by the button half cell discharging to 0V under 0.1C constant current, and C Constant pressure is the second discharge capacity measured by the button half cell discharging to 10 μA under 0V constant voltage; the button half cell comprises the negative electrode piece;
PD is the compacted density of the negative electrode membrane, and the unit is g/cm 3;
D v50 is the median particle diameter of the anode active material in μm.
2. The negative electrode tab of sodium ion battery of claim 1, wherein the battery is tested for C Constant current followed by C Constant pressure at a temperature in the range of 20 ℃ to 30 ℃;
preferably, the cell is tested at 25℃, followed by test C Constant current Constant pressure ;
Preferably, both C Constant current and C Constant pressure are tested on first discharge.
3. The negative electrode tab of a sodium ion battery according to claim 1, wherein 0.4.ltoreq.i.ltoreq.1, preferably 0.6.ltoreq.i.ltoreq.0.95, more preferably 0.65.ltoreq.i.ltoreq.0.9.
4. The negative electrode tab of a sodium ion battery according to claim 1, characterized by 0.7g/cm 3≤PD≤1.5g/cm3, preferably 0.9g/cm 3≤PD≤1.1g/cm3.
5. The negative electrode tab of a sodium ion battery according to claim 1, characterized in that 1 μm-D v50 -10 μm, preferably 4 μm-D v50 -6 μm.
6. The negative electrode tab of sodium ion battery of claim 1, wherein the negative active material comprises amorphous carbon; preferably, the amorphous carbon is hard carbon and/or soft carbon;
Preferably, the negative electrode sheet satisfies 0.05 < 7 (i×pd)/D v50 < 0.3; preferably, the negative electrode sheet satisfies 0.1 < 7 > (i×pd)/D v50 < 0.25; preferably, the negative electrode sheet satisfies 0.1 < 7.pd)/D v50 < 0.2.
7. A method for evaluating the performance of a negative electrode tab of a sodium ion battery as defined in any one of claims 1 to 6, comprising:
Calculating a difference value between the (i×pd)/D v50 and a preset value, wherein the preset value is determined according to the cycle performance of the sodium ion battery and/or the rate performance of the sodium ion battery;
Determining the grade of the negative electrode plate according to the difference value;
Preferably, the preset value is 0.14.
8. A sodium ion battery comprising a positive electrode sheet, a negative electrode sheet according to any one of claims 1-6.
9. A method for preparing a negative electrode plate of a sodium ion battery according to any one of claims 1 to 6, wherein the negative electrode plate of the sodium ion battery is obtained by coating a slurry containing a negative electrode active material on the surface of a negative electrode current collector and drying.
10. The method for producing a negative electrode tab of a sodium ion battery according to claim 9, wherein the slurry comprises a negative electrode active material, a conductive agent, a dispersant, an adhesive and water;
preferably, the slurry viscosity is 4800 mPas-5200 mPas;
Preferably, the conductive agent is superconducting carbon black; and/or the conductive agent is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material; and/or, the dispersing agent is sodium carboxymethyl cellulose; and/or the dispersant is added in an amount of 1.2wt.% to 1.8wt.% of the anode active material; and/or the adhesive is styrene-butadiene rubber; and/or the binder is added in an amount of 1.5wt.% to 2.5wt.% of the anode active material.
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