CN110957463A - Positive pole piece, lithium ion battery and manufacturing method thereof - Google Patents
Positive pole piece, lithium ion battery and manufacturing method thereof Download PDFInfo
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- C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
- C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
- C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
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- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract
The invention discloses a positive pole piece, a lithium ion battery and a manufacturing method thereof, wherein a single crystal high nickel ternary material is selected as a positive active material, the positive active material is selected from the single crystal high nickel ternary material and is doped with Mg, the particle surface of the single crystal high nickel ternary material is of a porous structure, the particle size is small, the conductivity is improved, lithium ions can be rapidly embedded into crystal lattices of the single crystal high nickel ternary material during high-rate discharge, and the rate capability of the positive active material, the positive pole piece coated with the positive active material and the lithium ion battery taking the positive pole piece as the positive pole are improved.
Description
Technical Field
The invention relates to the technical field of lithium ion secondary batteries, in particular to a positive pole piece, a lithium ion battery and a manufacturing method thereof.
Background
Lithium ion secondary batteries are widely used as power sources for portable devices such as mobile phones and notebook-size personal computers, and as driving power sources for industrial devices requiring a long service life, such as power storage devices and electric vehicles. In the future, reduction in weight and size of consumer devices are required, and batteries with further high energy density are required. Further, in industrial equipment, high output, high capacity, and long life performance corresponding to a large battery is required with the spread of electric vehicles and stationary power storage devices.
The requirements of people on power batteries are higher and higher, and the nickel content in the ternary material is increased along with the requirement, but the battery failure caused by the stability problem of the positive electrode material, the matching problem of the electrolyte, the high-current charging temperature rise and the like caused by the nickel content is also more and more concerned, so that the single crystal material is produced, the stability of the positive electrode material is enhanced, the voltage of the whole system can be increased to a new height, the structural stability of the single crystal material has great advantages, but the capacity of the single crystal material is not so advantageous.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a preparation method of a positive pole piece and a preparation method of a lithium ion battery using the positive pole piece, wherein the lithium ion battery has the characteristics of high capacity, high multiplying power and long service life.
The purpose of the invention is realized by adopting the following technical scheme:
a preparation method of positive electrode slurry for a lithium ion battery comprises the following steps:
1) synthesizing a positive electrode active substance from a precursor of the positive electrode active substance, wherein the positive electrode active substance is LiNixMyCozO2Wherein M is Mn and/or Al, x is more than or equal to 0.75 and less than or equal to 0.95, y is more than or equal to 0.01 and less than or equal to 0.2, z is more than or equal to 0.1 and less than or equal to 0.2, and x + y + z is 1.0;
2) mixing the positive electrode active substance obtained in the step 1), a binder and a conductive agent, wherein the positive electrode active substance accounts for 97.5 wt% of the positive electrode slurry, the binder accounts for 1.0 wt% of the positive electrode slurry, and the conductive agent accounts for 1.5 wt% of the positive electrode slurry.
3) Adding the mixture obtained in the step 2) into a solvent, and stirring the mixture in a rotation and revolution combined stirrer to prepare the anode slurry for the lithium ion battery with the solid content of 65-75%. The solvent is N-methyl pyrrolidone.
Further, the preparation method of the positive electrode active material comprises the following steps:
a. adding nickel salt, cobalt salt and M salt, mixing, dissolving in deionized water, adding an alkali solution and a complexing agent solution, stirring, standing for precipitation, filtering, removing impurities from filter residue, and drying to obtain a precursor of the positive active material, wherein the nickel salt is hydrated nickel sulfate, the cobalt salt is hydrated cobalt sulfate, and the M salt is hydrated aluminum sulfate or hydrated manganese sulfate; the mole fraction ratios of hydrated nickel sulfate, hydrated cobalt sulfate and hydrated aluminum sulfate or hydrated nickel sulfate, hydrated cobalt sulfate and hydrated manganese sulfate are as follows: 0.85: 0.1: 0.05; the alkali solution is a sodium hydroxide solution with the concentration of 4mol/L, and the molar ratio of the sodium hydroxide to the precursor of the positive active material is 2: 1; the complexing agent solution is 0.2-0.8mol/L ammonia water solution.
b. Mixing and grinding the precursor of the positive active material obtained in the step a with a lithium source and a magnesium salt, and then sintering to obtain the positive active material, wherein the sintering time is 8-20h, and the optimal value is 9-14 h; the sintering temperature is 650-950 ℃, the preferred value is 700-800 ℃, the protective atmosphere is oxygen, during the sintering process, the raw material decomposition in the sintering furnace can generate a large amount of gas, the waste gas in the furnace is driven away by blowing oxygen, and the oxygen gas inflow is generally controlled to ensure the sintering and forming of the material. The molar ratio of the precursor of the positive electrode active material to the lithium source is 1: 1.02-1.15, with a preferred value of 1: 1.06-1.12; the molar ratio of the precursor of the positive electrode active material to the magnesium salt is 1: 0.01-0.05, preferably 1: 0.02-0.04.
Wherein the lithium source can be lithium carbonate (Li)2CO3Battery grade, purity is more than or equal to 99.95 percent) or lithium hydroxide monohydrate (LiOH. H)2O, battery grade, purity is more than or equal to 99.95 percent). The Mg salt can be MgCl2、Mg(OH)2And Mg (NO)3)2One or two of them.
Positive electrode active material LiNixMyCozO2The material is a single crystal high nickel ternary material, is granular, has a porous structure on the surface and has small grain diameter. The positive active substance is doped with Mg, so that the conductivity is obviously improved, and lithium ions can be rapidly embedded into the crystal lattice of the single crystal high-nickel ternary material during high-rate discharge, thereby improving the rate capability of the positive active substance and even the lithium ion battery.
Further, in the step 2), the binder is polyvinylidene fluoride, and the conductive agent is a carbon nanotube-graphene composite conductive agent. The polyvinylidene fluoride has high molecular weight, and the addition amount of the polyvinylidene fluoride in the positive electrode slurry is small, so that the proportion of positive electrode active substances is higher, and the capacity of the lithium ion battery is high; the polyvinylidene fluoride has long main chain and multiple branched chains, and functional groups are uniformly distributed on the main chain, so that the polyvinylidene fluoride has strong flexibility and excellent adhesion effect, and the positive electrode slurry for the lithium ion battery has a stable structure. The carbon nano tube has small tube diameter and can be uniformly attached to the surface of the particles of the positive active material, and simultaneously, the carbon nano tube has long tube length and connects a plurality of positive active material particles, so that an excellent conductive network is established; graphene is a very good electronic conductor, and a small amount of graphene is added into the positive electrode slurry, so that the resistance of the coating is remarkably reduced, and the rate capability of the battery is improved.
The positive pole piece comprises a positive pole current collector and positive pole slurry coated on the surface of the positive pole current collector, wherein the drying temperature of the coated positive pole piece is 80-140 ℃, and the positive pole slurry is prepared by adopting the preparation method of the positive pole slurry for the lithium ion battery.
Furthermore, the positive pole piece also comprises a positive pole lug, and the positive pole lug is welded on the positive pole current collector. The positive lug plays a role in drainage and reduces the structural internal resistance of the lithium ion battery.
A lithium ion battery adopts the anode plate mentioned above as the anode.
Furthermore, the lithium ion battery also comprises electrolyte, a diaphragm and a negative pole piece arranged on the negative pole of the battery core of the lithium ion battery, and a negative pole lug is welded on the negative pole piece.
Still further, the electrolyte of the lithium ion battery comprises lithium salt, additive and solvent, wherein the lithium salt accounts for 12-18 wt% of the electrolyte, the additive accounts for 4-16 wt% of the electrolyte, and the solvent accounts for 70-80 wt% of the electrolyte.
Further, the lithium salt in the electrolyte of the lithium ion battery is LiPF6，LiPF6In a molar ratio of EC: EMC: DMC ═ 2:1:7, and comprises a combination of at least one of fluoroethylene carbonate (FEC), Vinyl Ethylene Sulfite (VES), 3-fluoropropane sultone (FPS), 1-propene-1, 3-sultone (PST), and lithium bis-fluorosulfonylimide (LiFSI).
LiPF in electrolyte6The concentration is high, the content of active lithium ions is more, the transfer number of the lithium ions in unit time is more in the high-rate discharge process, the rate performance is favorably improved, and the cycle life of the product is prolonged. Fluoroethylene carbonate (FEC) and 1-propylene-1, 3-sultone (PST) are used as additives, and can participate in forming a compact and thin SEI film with low impedance and good flexibility on a negative pole piece; the film forming impedance is low, which is beneficial to the rapid conduction of lithium ions; the internal temperature of the lithium ion battery can be rapidly increased during high-rate discharge to cause the thermal decomposition of the SEI film, and the VES and the FPS are added to participate in the formation of the SEI film, so that the structure of the SEI film is more stable at high temperature, and the problem that the performance of the battery is reduced due to the decomposition of the SEI film at high temperature is avoided; LiFSI is added to improve the conductivity of the electrolyte, and the electrolyte and LiPF are added6The synergistic effect is realized by the synergistic effect,and the high-rate discharge capacity of the battery is improved.
The installation method of the lithium ion battery comprises the following steps:
winding the positive pole piece, the negative pole piece and the diaphragm according to the overlapping mode of the diaphragm/the negative pole piece/the diaphragm/the positive pole piece to prepare a cylindrical winding core; 1 insulating gasket is sleeved at the upper end and the lower end of the winding core respectively;
and II, welding the negative electrode lug of the negative electrode plate at the bottom of the shell, welding the positive electrode lug of the positive electrode plate at the position of the cap afflux sheet, baking the cylindrical winding core, injecting 5.6-6.0g of electrolyte, and sealing to obtain the lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
the positive active substance is a single-crystal high-nickel ternary material doped with Mg, the particle surface of the single-crystal high-nickel ternary material is in a porous structure, the particle size is small, the conductivity is improved, lithium ions can be rapidly embedded into crystal lattices of the single-crystal high-nickel ternary material during high-rate discharge, and the rate capability, the capacity capability and the cycle life of the positive active substance, a positive pole piece coated with the positive active substance and a lithium ion battery taking the positive pole piece as a positive pole are improved.
Drawings
Fig. 1 is an internal structural view of a lithium ion battery.
Reference numerals:
1. a positive electrode plate; 2. a negative pole piece; 3. a safety valve; 4. a diaphragm; 5. an insulating sheet; 6. capping; 11. a positive tab; 21. and a negative tab.
Detailed Description
The present invention will be further described with reference to the drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.
Example 1
The preparation method of the positive electrode active material comprises the following steps:
a. adding hydrated nickel sulfate, hydrated cobalt sulfate and hydrated aluminum sulfate, mixing, dissolving in deionized water, adding a sodium hydroxide solution with the concentration of 4mol/L and an ammonia water solution with the concentration of 0.2mol/L, stirring, standing for precipitation, filtering, removing impurities from filter residues, and drying to obtain a precursor of the positive active substance, wherein the mole fraction ratio of the hydrated nickel sulfate to the hydrated cobalt sulfate to the hydrated aluminum sulfate is 0.85: 0.1: 0.05, wherein the molar ratio of the sodium hydroxide solution to the precursor of the positive active material is 2: 1;
b. mixing the precursor of the positive electrode active material obtained in the step a with lithium carbonate (Li)2CO3Battery grade, purity > 99.95%) and MgCl2And mixing, grinding and sintering to obtain the anode active substance, wherein the sintering time is 8h, the sintering temperature is 650 ℃, the protective atmosphere is oxygen, during the sintering process, the raw materials in the sintering furnace are decomposed to generate a large amount of gas, and the waste gas in the furnace is driven away by blowing oxygen and adjusting the air inflow to ensure the sintering and forming of the materials. Precursor of positive electrode active material and Li2CO3In a molar ratio of 1: 1.02 precursors of Positive electrode active substances with MgCl2In a molar ratio of 1: 0.01.
a preparation method of positive electrode slurry for a lithium ion battery comprises the following steps:
1) synthesizing a positive electrode active substance from a precursor of the positive electrode active substance, wherein the positive electrode active substance is LiNi0.85Al0.05Co0.10O2；
2) Mixing the positive electrode active substance obtained in the step 1), a binder and a conductive agent, wherein the positive electrode active substance accounts for 97.5 wt% of the positive electrode slurry, the binder accounts for 1.0 wt% of the positive electrode slurry, and the conductive agent accounts for 1.5 wt% of the positive electrode slurry. The binder is polyvinylidene fluoride, and the conductive agent is a carbon nano tube-graphene composite conductive agent.
3) Adding the mixture obtained in the step 2) into a solvent. The positive electrode active material, the binder, the conductive agent and the solvent are all added into a rotation and revolution combined stirrer to be stirred, wherein the charging sequence, the stirring and revolution and rotation speeds, the stirring time, the vacuum degree and the temperature of the slurry during stirring are all summarized in table 1. Stirring to prepare the anode slurry with the solid content of 65 percent for the lithium ion battery. The solvent is N-methyl pyrrolidone. As can be seen from table 1, the binder was added 1 time, the solvent was added 3 times, the conductive agent was added 1 time, and the positive electrode active material was added 1 time.
TABLE 1 parameters of the charging step and the stirring process in step 2) and step 3)
A positive pole piece 1 comprises a positive pole current collector and positive pole slurry coated on the surface of the positive pole current collector, wherein the positive pole slurry is prepared by the preparation method of the positive pole slurry for the lithium ion battery. The positive electrode current collector is aluminum foil, the positive electrode slurry is coated on the aluminum foil with the thickness of 16 mu m, the aluminum foil is put into a coating machine oven to be dried at the temperature of 80-140 ℃, and then the aluminum foil is rolled into a positive electrode plate 1 with the thickness of about 100 mu m, and then the positive electrode plate is cut. The final positive electrode sheet 1 was rectangular and was sized to be 950 ± 50 mm long by 56-57 mm wide by 0.10mm thick.
Further, the positive pole piece 1 further comprises a positive pole tab 11, and the positive pole tab 11 is welded on the positive pole current collector. And 1/3 and 2/3 points in the length direction of the aluminum foil are respectively welded with 1 positive tab 11. Then the insulating paster is pasted.
A lithium ion battery adopts the anode plate 1 as the anode.
Further, the lithium ion battery also comprises electrolyte, a diaphragm 4 and a negative pole piece 2, wherein a negative pole lug 21 is welded on the negative pole piece 2.
Still further, the electrolyte of the lithium ion battery comprises lithium salt, an additive and a solvent, wherein the lithium salt accounts for 12 wt% of the electrolyte, the additive accounts for 8 wt% of the electrolyte, and the solvent accounts for 80 wt% of the electrolyte.
Further, the lithium salt in the electrolyte of the lithium ion battery is LiPF6，LiPF6In a concentration of 1.2mol/L, a solvent comprising Ethylene Carbonate (EC), methylethyl carbonate (EMC) and dimethyl carbonate (DMC) in a molar ratio of EC: EMC: DMC ═ 2:1:7, and additives comprising fluoroethylene carbonate (FEC), ethylene sulfite (VES), 3-fluoropropane sultone (FPS), 1-propene-1, 3-sultone (PST) andone or more of lithium bis (fluorosulfonyl) imide (LiFSI).
The method for mounting the lithium ion battery, as shown in fig. 1, comprises the following steps:
i, winding a positive pole piece 1, a negative pole piece 2 and a diaphragm 4 in an overlapping mode of the diaphragm 4/the negative pole piece 2/the diaphragm 4/the positive pole piece 1 to prepare a cylindrical winding core; an insulating sheet 5 is respectively sleeved on the upper end and the lower end of the winding core.
II, welding the negative tab 21 of the negative pole piece 2 at the bottom of the shell, welding the positive tab 11 of the positive pole piece 1 at the position of the afflux sheet of the cap 6 by laser, baking the cylindrical winding core, injecting 6.0g of electrolyte, combining the cap 6 and the shell, and sealing to obtain the lithium ion battery, wherein the diaphragm 4 is a PP/PE/PP composite diaphragm 4 with high porosity (45-52%) and low air permeability (110 plus material 160s/100mL), and is beneficial to rapid migration of lithium ions; the diaphragm 4 has high compressive strength and tensile strength, and is beneficial to improving the safety performance of the lithium ion battery; the diaphragm 4 has strong liquid absorption, which is beneficial to enhancing the infiltration effect of the anode pole piece 1 and the cathode pole piece 2 and improving the cycle performance of the lithium ion battery.
Wherein, the cap 6 is a combined part and is formed by combining a confluence piece, a safety valve 3, a steel cap and a sealing ring.
Example 2
The preparation method of the positive electrode active material comprises the following steps:
a. adding hydrated nickel sulfate, hydrated cobalt sulfate and hydrated manganese sulfate, mixing, dissolving in deionized water, adding sodium hydroxide with the concentration of 4mol/L and ammonia water solution with the concentration of 0.8mol/L, stirring, standing for precipitation, filtering, removing impurities from filter residues, and drying to obtain a precursor of the positive active substance, wherein the mole fraction ratio of the hydrated nickel sulfate to the hydrated cobalt sulfate to the hydrated manganese sulfate is as follows: 0.85: 0.1: 0.05, the molar ratio of the sodium hydroxide solution to the precursor of the positive active material is 2: 1;
b. b, mixing the precursor of the positive active material obtained in the step a with lithium hydroxide monohydrate (LiOH. H)2O, battery grade, purity > 99.95%) and Mg (OH)2Mixing, grinding, and sintering to obtain positive electrode active substance, wherein the sintering time is 20h and the sintering temperature is highThe temperature is 950 ℃, the protective atmosphere is oxygen, during the sintering process, the raw materials in the sintering furnace are decomposed to generate a large amount of gas, and the waste gas in the furnace is driven away by blowing oxygen and controlling the air inflow so as to ensure the sintering and forming of the material. Precursor of positive electrode active material and LiOH H2The molar ratio of O is 1: 1.15 precursors of Positive electrode active Material and Mg (OH)2In a molar ratio of 1: 0.05.
a preparation method of positive electrode slurry for a lithium ion battery comprises the following steps:
1) synthesizing a positive electrode active substance from a precursor of the positive electrode active substance, wherein the positive electrode active substance is LiNi0.85Mn0.05Co0.10O2；
2) Mixing the positive electrode active substance obtained in the step 1), a binder and a conductive agent, wherein the positive electrode active substance accounts for 97.5 wt% of the positive electrode slurry, the binder accounts for 1.0 wt% of the positive electrode slurry, and the conductive agent accounts for 1.5 wt% of the positive electrode slurry. The binder is polyvinylidene fluoride, and the conductive agent is a carbon nano tube-graphene composite conductive agent.
3) Adding the mixture obtained in the step 2) into a solvent. The positive electrode active material, the binder, the conductive agent and the solvent were all added to a rotation and revolution combined stirrer and stirred, wherein the charging order, the stirring and revolution and rotation speeds, the stirring time, the vacuum degree and the temperature of the slurry during stirring were the same as those in example 1. Stirring to prepare the anode slurry with the solid content of 65 percent for the lithium ion battery. The solvent is N-methyl pyrrolidone.
A positive electrode plate 1, as shown in fig. 1, includes a positive electrode current collector and a positive electrode slurry coated on the surface of the positive electrode current collector, wherein the positive electrode slurry is prepared by the above-mentioned preparation method of the positive electrode slurry for the lithium ion battery. The positive electrode current collector is aluminum foil, the positive electrode slurry is coated on the aluminum foil with the thickness of 16 mu m, the aluminum foil is put into a coating machine oven to be dried at the temperature of 80-140 ℃, and then the aluminum foil is rolled into a positive electrode plate 1 with the thickness of about 100 mu m, and then the positive electrode plate is cut. The final positive electrode sheet 1 was rectangular and was sized to be 950 ± 50 mm long by 56-57 mm wide by 0.10mm thick.
Further, the positive pole piece 1 further comprises a positive pole tab 11, and the positive pole tab 11 is welded on the positive pole current collector. And 1/3 and 2/3 points in the length direction of the aluminum foil are respectively welded with 1 positive tab 11. Then the insulating paster is pasted.
A lithium ion battery adopts the anode plate 1 as the anode.
Further, the lithium ion battery also comprises electrolyte, a diaphragm 4 and a negative pole piece 2, wherein a negative pole lug 21 is welded on the negative pole piece 2.
Still further, the electrolyte of the lithium ion battery comprises lithium salt, an additive and a solvent, wherein the lithium salt accounts for 18 wt% of the electrolyte, the additive accounts for 12 wt% of the electrolyte, and the solvent accounts for 70 wt% of the electrolyte.
Further, the lithium salt in the electrolyte of the lithium ion battery is LiPF6，LiPF6In a molar ratio of EC: EMC: DMC ═ 2:1:7, and a dimethyl carbonate (DMC), the additive comprises a combination of at least one of fluoroethylene carbonate (FEC), ethylene sulfite (VES), 3-fluoropropane sultone (FPS), 1-propene-1, 3-sultone (PST), and lithium bis-fluorosulfonylimide (LiFSI).
The method for mounting the lithium ion battery, as shown in fig. 1, comprises the following steps:
i, winding a positive pole piece 1, a negative pole piece 2 and a diaphragm 4 in an overlapping mode of the diaphragm 4/the negative pole piece 2/the diaphragm 4/the positive pole piece 1 to prepare a cylindrical winding core; an insulating sheet 5 is respectively sleeved on the upper end and the lower end of the winding core.
II, welding the negative electrode tab 21 of the negative electrode plate 2 at the bottom of the shell, laser welding the positive electrode tab 11 of the positive electrode plate 1 at the position of the bus piece of the cap 6, baking the cylindrical winding core, injecting 5.6g of electrolyte, combining the cap 6 and the shell, sealing, and forming to obtain the lithium ion battery. The diaphragm 4 is a PP/PE/PP composite diaphragm 4 with high porosity (45-52%) and low air permeability (110-; the diaphragm 4 has high compressive strength and tensile strength, and is beneficial to improving the safety performance of the lithium ion battery; the diaphragm 4 has strong liquid absorption, which is beneficial to enhancing the infiltration effect of the anode pole piece 1 and the cathode pole piece 2 and improving the cycle performance of the lithium ion battery.
Wherein, the cap 6 is a combined part and is formed by combining a confluence piece, a safety valve 3, a steel cap and a sealing ring.
Results of battery performance testing
The performance of the lithium ion battery manufactured in example 1 was measured to obtain the following results:
and (3) capacity testing: the battery was fully charged with a CC-CV (cutoff current 0.01CA) using a 0.2CA (i.e., 0.5A) current, left to stand for 5min, and then discharged to 2.75V using a 0.2CA (i.e., 0.5A) constant current discharge, and the discharge capacity was recorded.
And (3) rate discharge test: charging to 4.2V with constant current and constant voltage at 1.25A (0.5CA), stopping current at 25mA, standing for 5min, discharging to 2.75V with 1.25A (0.5CA), and standing for five min; the cells were charged according to the above-mentioned charge system, and then discharged at 5A/10A/15A/20A/25A/30A/35A/40A, respectively, and the discharge capacities thereof were recorded.
And (3) testing the cycle performance: charging to 4.2V at constant current and constant voltage with 2A (0.8CA) current and cutoff current of 25mA, standing for five minutes, discharging to 2.75V with 20A (8CA) current, and standing for five minutes; the cycle life test was carried out according to this protocol.
TABLE 1 Battery capacity test results
| Battery numbering | Charging current (A) | Discharge current (A) | Discharge capacity (mAh) |
| Example 11 # | 0.5 | 0.5 | 2560 |
| Example 12 # | 0.5 | 0.5 | 2535 |
| Example 21 # | 0.5 | 0.5 | 2505 |
| Example 22 # | 0.5 | 0.5 | 2535 |
Table 2 example 1 results of battery rate discharge test
| Discharge current | Discharge rate | Discharge capacity (mAh) | Capacity retention rate |
| 1.25A | 0.5C | 2560 | 100.00％ |
| 5A | 2C | 2535 | 99.02％ |
| 10A | 4C | 2502 | 97.73％ |
| 15A | 6C | 2455 | 95.90％ |
| 20A | 8C | 2401 | 93.79％ |
| 25A | 10C | 2478 | 95.12％ |
| 30A | 12C | 2501 | 96.95％ |
| 35A | 14C | 2410 | 94.14％ |
| 40A | 16C | 2388 | 93.28％ |
Table 3 example 2 battery rate discharge test results
Table 4 battery cycling test results
As can be seen from Table 1, the lithium ion batteries of examples 1 and 2 had discharge capacities of 2500mAh or more and high capacities. As can be seen from table 2, the maximum sustained discharge rate of the lithium ion battery in example 1 is 16C (i.e., the discharge current is 40A), and the capacity retention rate reaches 93.28%, which results in good rate performance. As can be seen from table 3, the maximum sustained discharge rate of the lithium ion battery in example 2 is 16C (i.e., the discharge current is 40A), and the capacity retention rate reaches 93.63%, which results in good rate performance. As can be seen from Table 4, the lithium ion battery in example 1 has a capacity retention rate of not less than 80% at 1000 weeks and a long battery cycle life when a cycle test is performed in a manner of 2A charge/20A discharge. The lithium ion battery in example 2 is subjected to cycle test in a mode of 2A charging/20A discharging, the capacity retention rate at 1000 weeks is more than or equal to 80%, and the cycle life of the battery is long.
In summary, the lithium ion battery adopts the positive electrode plate coated with the positive electrode slurry which takes the single-crystal high-nickel ternary material as the positive electrode active material as the positive electrode, and the capacity retention rate can be kept above 90% under the discharge rate of 16C. The discharge capacity was 2300mAh or more at a discharge rate of 16C. The capacity retention rate of the battery is more than or equal to 80 percent after 1000 weeks of cyclic test by a system of charging 2A and discharging 20A. The lithium ion was demonstrated to have high capacity, high rate, and long life characteristics.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A preparation method of positive electrode slurry for a lithium ion battery is characterized by comprising the following steps:
1) synthesizing a positive electrode active substance from a precursor of the positive electrode active substance, wherein the positive electrode active substance is LiNixMyCozO2Wherein M is Mn and/or Al, x is more than or equal to 0.75 and less than or equal to 0.95, y is more than or equal to 0.01 and less than or equal to 0.2, z is more than or equal to 0.1 and less than or equal to 0.2, and x + y + z is 1.0;
2) mixing the positive electrode active substance obtained in the step 1), a binder and a conductive agent, wherein the positive electrode active substance accounts for 97.5 wt% of the positive electrode slurry, the binder accounts for 1.0 wt% of the positive electrode slurry, and the conductive agent accounts for 1.5 wt% of the positive electrode slurry.
3) Adding the mixture obtained in the step 2) into a solvent, and stirring to prepare the anode slurry for the lithium ion battery with the solid content of 65-75%.
2. The method for preparing the positive electrode slurry for a lithium ion battery according to claim 1, wherein the method for preparing the positive electrode active material comprises the steps of:
a. adding nickel salt, cobalt salt and M salt, mixing, dissolving in deionized water, adding an alkali solution and a complexing agent solution, stirring, standing for precipitation, filtering, removing impurities from filter residue, and drying to obtain a precursor of the positive active material, wherein the molar fraction ratio of the nickel salt, the cobalt salt and the M salt is as follows: 0.85: 0.1: 0.05, the molar ratio of the alkali solution to the precursor of the positive active material is 2:1, complexing agent is 0.2-0.8mol/L ammonia water solution;
b. and b, mixing and grinding the precursor of the positive active material obtained in the step a with a lithium source and a magnesium salt, and then sintering to obtain the positive active material, wherein the sintering time is 9-14h, the sintering temperature is 700-800 ℃, the protective atmosphere is oxygen, and the molar ratio of the lithium source to the precursor of the positive active material is 1: 1.02-1.15, wherein the molar ratio of the magnesium salt to the precursor of the positive active material is 1: 0.01-0.05.
3. The method for producing a positive electrode slurry for a lithium ion battery according to claim 1, characterized in that: in the step 2), the binder is polyvinylidene fluoride, and the conductive agent is a carbon nanotube-graphene composite conductive agent.
4. A positive pole piece is characterized in that: the positive pole piece drying method comprises a positive pole current collector and positive pole slurry coated on the surface of the positive pole current collector, wherein the drying temperature of the coated positive pole piece is 80-140 ℃, and the positive pole slurry is prepared by the preparation method of the positive pole slurry for the lithium ion battery according to any one of claims 1-3.
5. The positive electrode sheet according to claim 4, wherein: the positive lug is welded on the positive current collector.
6. A lithium ion battery, characterized in that the positive pole piece according to any one of claims 4 to 5 is used as a positive pole.
7. The lithium ion battery of claim 6, wherein: the lithium ion battery also comprises electrolyte, a diaphragm and a negative pole piece, wherein a negative pole lug is welded on the negative pole piece.
8. The lithium ion battery of claim 7, wherein: the electrolyte of the lithium ion battery comprises lithium salt, an additive and a solvent, wherein the lithium salt accounts for 12-18 wt% of the electrolyte, the solvent accounts for 70-80 wt% of the electrolyte, and the additive accounts for 4-16 wt% of the electrolyte.
9. The lithium ion battery of claim 8, wherein: the lithium salt in the electrolyte of the lithium ion battery is LiPF6，LiPF6In a concentration of 1.2 to 1.6mol/L, the solvent comprises ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a molar ratio of ethylene carbonate to methyl ethyl carbonate to dimethyl carbonate of 2:1:7,the additive comprises a combination of at least one of fluoroethylene carbonate, vinyl ethylene sulfite, 3-fluoropropane sultone, 1-propene-1, 3-sultone and lithium bis-fluorosulfonylimide.
10. A method of mounting a lithium ion battery according to any of claims 7 to 9, comprising the steps of:
winding the positive pole piece, the negative pole piece and the diaphragm according to the overlapping mode of the diaphragm/the negative pole piece/the diaphragm/the positive pole piece to prepare a cylindrical winding core;
and II, welding the negative electrode lug of the negative electrode plate at the bottom of the shell, welding the positive electrode lug of the positive electrode plate at the position of the cap afflux sheet, baking the cylindrical winding core, injecting 5.6-6.0g of electrolyte, and sealing to obtain the lithium ion battery.
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| CN112421019A (en) * | 2020-11-20 | 2021-02-26 | 浙江帕瓦新能源股份有限公司 | B/Mg co-doped high-nickel ternary precursor material, positive electrode material and preparation method |
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| CN113964372A (en) * | 2021-09-28 | 2022-01-21 | 天津力神电池股份有限公司 | High-power cylindrical lithium ion battery |
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