阅读说明：本技术 一种复合补锂浆料、制备方法及应用 (Composite lithium supplement slurry, preparation method and application ) 是由 董彬彬 张振宇 巩志男 于 2020-03-31 设计创作，主要内容包括：本发明公开了一种复合补锂浆料、制备方法及应用,所述复合补锂浆料包括：补锂材料、电子导体材料、粘结剂、分散剂和溶剂；所述复合浆料中,所述补锂材料、电子导体材料、粘结剂、分散剂、溶剂的质量百分比分别为0.1％≤a≤29.9％,0.1％≤b≤29.9％,0≤c≤29.8％、0≤d≤10％,50％≤e≤99.8％,a+b+c+d+e＝100％。本发明提供的复合补锂浆料,制备工艺简单；浆料中正极补锂添加剂可以有效的弥补充放电过程中由于形成SEI膜而损失的锂离子,从而保证有更多的锂离子可以再次嵌入正极材料,提高正极材料的容量发挥,保证整体锂离子电池具有更高的能量密度,电子导体材料可以提高材料的导电性,从而进一步保证材料能够快速的脱嵌锂。(The invention discloses a composite lithium supplement slurry, a preparation method and application thereof, wherein the composite lithium supplement slurry comprises the following components: lithium supplement materials, electronic conductor materials, binders, dispersants and solvents; in the composite slurry, the mass percentages of the lithium supplement material, the electronic conductor material, the binder, the dispersant and the solvent are respectively 0.1-29.9% of a, 0.1-29.9% of b, 0-29.8% of c, 0-10% of d, 50-99.8% of e and 100% of a + b + c + d + e. The composite lithium supplement slurry provided by the invention has a simple preparation process; the anode lithium supplement additive in the slurry can effectively make up lithium ions lost due to the formation of an SEI film in the charging and discharging process, so that more lithium ions can be inserted into the anode material again, the capacity of the anode material is improved, the whole lithium ion battery is ensured to have higher energy density, the electronic conductor material can improve the conductivity of the material, and the material is further ensured to be capable of rapidly extracting and inserting lithium.)

1. A composite lithium replenishment slurry, comprising: lithium supplement materials, electronic conductor materials, binders, dispersants and solvents; in the composite lithium supplementing slurry, the mass percentages of the lithium supplementing material, the electronic conductor material, the binder, the dispersant and the solvent are respectively 0.1-29.9% of a, 0.1-29.9% of b, 0-29.8% of c, 0-10% of d, 50-99.8% of e and 100% of a + b + c + d + e.

2. The composite lithium supplementing slurry according to claim 1, wherein the solid content of the composite slurry is 0.2% to 50%.

3. The composite lithium replenishing slurry according to claim 2, wherein the solid content of the composite slurry is 1-25%.

4. The composite lithium replenishing slurry according to claim 1, wherein the viscosity of the composite slurry is 1000 to 10000 mPa.s.

5. The composite lithium replenishing slurry according to claim 4, wherein the viscosity of the composite slurry is 2000 to 8000 mPa.s.

6. The composite lithium replenishing slurry according to any one of claims 1 to 5, wherein the lithium replenishing material is Li₃N、LiF、Li₂S₂、Li₂S、Li₂C₂O₄、Li₂NiO₂、Li₂CuO₂、Li₂S₂O₃、Li₂S₂O₄、Li₂S₂O₅、Li₂S₂O₆、Li₂S₄O₆、Li₅Fe₅O₈、Li_5±xM_yO₄、Li_zM’_1-z、a1Li₂MnO₃·(1-a1)LiM”O₂、Li_1+eNi_0.5Mn_1.5O₄Wherein x is more than or equal to 0 and less than or equal to 5, y is more than 0, z is more than 0 and less than 1, 0<a1 is less than or equal to 1, e1 is more than 0, M is any one or more selected from Fe, Al, Co, Mn, Zn, Ni, Pt, Ni, Sb, Te, Ti, V, Mo, Nb, B, Si, Ge and Sn, M 'is any one or more selected from Si, C, B, Mg, Al, Zn, Sn, Cu, Fe, Ni, Mn, Co and Ti, and M' is any one or more selected from Fe, Al, Co, Mn, Ni, Cr, Ti, V, Mg and Ru.

7. The composite lithium supplement slurry according to claim 6, wherein the lithium supplement material is crystalline, amorphous or a mixture of crystalline and amorphous, and the lithium supplement material has a median particle size of not greater than 30 μm.

8. The composite lithium replenishing slurry of claim 7, wherein the lithium replenishing material has a median particle size of no greater than 1 μm.

9. The composite lithium replenishing paste according to any one of claims 1 to 5, wherein the electronic conductor is one or more of amorphous carbon, conductive graphite, nanographite, conductive carbon black, carbon nanotubes, carbon fibers, fullerene, graphene, a conductive polymer derivative or a partially carbonized conductive polymer.

10. The composite lithium supplementing slurry according to any one of claims 1 to 5, wherein the dispersant is one or more of an inorganic dispersant, an organic dispersant and a polymeric dispersant; the inorganic dispersant is polyphosphate or silicate; the organic dispersant is an anionic dispersant, a nonionic dispersant or a cationic dispersant; the polymeric dispersant comprises polycarboxylate, polyacrylic acid derivative, maleic anhydride copolymer or nonionic water-soluble polymer; the solvent is selected from one or more of N-methyl pyrrolidone, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, dimethyl sulfoxide, tetrahydrofuran, water, methanol, ethanol, propanol, isopropanol, ethylene glycol, benzyl alcohol, acetone, acetonitrile, dimethyl carbonate, propylene carbonate, benzene, toluene, xylene, methyl ether, ethyl ether and ethylene glycol dimethyl ether.

11. A method for preparing the composite lithium replenishing slurry according to any one of claims 1 to 10, characterized by: the method comprises the following steps:

providing a lithium supplement material, an electronic conductor material, a binder, a dispersant and a solvent in formula amounts;

and adding the lithium supplement material, the electronic conductor material, the binder and the dispersant into the solvent for uniform dispersion to obtain the composite conductive slurry.

12. A preparation method of a lithium battery positive pole piece is characterized by comprising the following steps: in the mixing/pulping/size mixing/pulping stage of preparing the positive pole piece, the composite lithium supplement slurry, the positive active material, the binder, the conductive agent and the second solvent are added according to any one of claims 1 to 10, and the positive pole piece coated with the composite lithium supplement slurry is prepared through the working procedures of coating, baking, rolling and die cutting.

13. A composite lithium-supplementing slurry coated positive pole piece prepared by the method of claim 12, wherein the mass ratio of the composite lithium-supplementing slurry in the positive pole piece is A, the mass ratio of the positive active material in the positive pole piece is B, the mass ratio of the binder in the positive active material in the positive pole piece is C, and the mass ratio of the conductive agent in the positive pole piece is D, wherein the mass ratio of A is 0.1-50%, B is 50-99.9%, C is 0-20%, D is 0-10%, and A + B + C + D is 100%.

14. The application method of the composite lithium supplement slurry coated positive pole piece prepared by the method of claim 12 is characterized by comprising the following steps: the lithium ion battery anode plate is used as a lithium ion battery anode plate, or a part of the electronic conductor material and the lithium supplement material on the anode plate are coated on the surface of the anode active material on the anode plate by a hot-pressing compounding process.

15. The application method of the hot-pressing compounding process according to claim 14, wherein the temperature of the hot-pressing compounding process is 50-300 ℃, and the pressure is 0.1-100 MPa.

16. The use method of claim 15, wherein the hot-pressing compounding process is carried out at a temperature of 60-200 ℃ and a pressure of 0.5-60 MPa.

17. A lithium ion battery using the positive electrode sheet prepared by the method of claim 12 as a positive electrode sheet.

Technical Field

The invention belongs to the field of lithium ion batteries, particularly relates to the field of lithium ion battery anode slurry, and particularly relates to composite lithium supplement slurry, a preparation method thereof, an anode plate adopting the composite lithium supplement slurry and a lithium ion battery.

Background

The lithium ion battery has wide application in the fields of power batteries, 3C, energy storage and the like. The market has higher and higher requirements on the performances of lithium ion batteries such as energy density, cycle and the like, and the optimization of battery materials relates to a positive electrode material, a negative electrode material, a diaphragm, electrolyte, a battery preparation process and the like.

Currently, materials such as lithium iron phosphate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide and the like are generally used as the positive electrode of the lithium ion battery, and materials such as carbon, silicon and the like are used as the negative electrode of the lithium ion battery. However, during the initial charge and discharge of the lithium ion battery, a solid electrolyte thin film is formed on the surface of the negative electrode, and active lithium ions are consumed in the process, thereby increasing the irreversible capacity.

Researchers supplement lithium ions lost due to the formation of an SEI film by a method of supplementing lithium through a negative electrode, so that the first efficiency and the specific discharge capacity of the lithium ion battery are improved. For example, lithium can be replenished by spraying lithium powder on the surface of the negative electrode or coating a thin layer of lithium on the surface of the negative electrode. However, the requirement of lithium supplement of the negative electrode on the environment is high, the investment is large, and meanwhile, the adoption of the metal lithium has great potential safety hazard.

Some researchers have conducted research on lithium supplement of the positive electrode, for example, chinese patent No. CN201810282994.9, in which lithium peroxide is used as a lithium supplement material to prepare a conductive paste, but the conductive paste has a low melting point and is sensitive to water, so that the stability of the conductive paste is poor, and lithium peroxide cannot form a good coating effect on the surface of the positive electrode material, which may affect electrochemical properties such as cycle. In the chinese patent No. 201810120654.6, the lithium supplement material and the conductive agent are directly added during the process of preparing the positive electrode slurry, and the method is difficult to ensure the uniform dispersion of the lithium supplement material, the conductive agent of carbon nanotube and other types and the active substance, thereby affecting the performance of the material.

Disclosure of Invention

In view of the background, the invention aims to provide a novel low-cost, green, environment-friendly and stable composite lithium supplement slurry for a lithium ion battery, a positive pole piece adopting the composite lithium supplement slurry and a battery adopting the positive pole piece.

The purpose of the invention is realized by the following technical scheme:

a composite lithium replenishment slurry comprising: lithium supplement materials, electronic conductor materials, binders, dispersants and solvents; in the composite lithium supplementing slurry, the mass percentages of the lithium supplementing material, the electronic conductor material, the binder, the dispersant and the solvent are respectively 0.1-29.9% of a, 0.1-29.9% of b, 0-29.8% of c, 0-10% of d, 50-99.8% of e and 100% of a + b + c + d + e.

Further, the solid content of the composite slurry is 0.2-50%, and the solid content is preferably 1-25%.

Further, the viscosity of the composite slurry is 1000 to 10000mPa.s, preferably 2000 to 8000 mPa.s.

Further, the lithium supplement material is Li₃N、LiF、Li₂S₂、Li₂S、Li₂C₂O₄、Li₂NiO₂、Li₂CuO₂、Li₂S₂O₃、Li₂S₂O₄、Li₂S₂O₅、Li₂S₂O₆、Li₂S₄O₆、Li₅Fe₅O₈、Li_5±xM_yO₄、Li_zM’_1-z、a1Li₂MnO₃·(1-a1)LiM”O₂、Li_1+e1Ni_0.5Mn_1.5O₄Wherein x is more than or equal to 0 and less than or equal to 5, y is more than 0, z is more than 0 and less than 1, 0<a1 is not more than 1, e1 is more than 0, M is selected from Fe, Al, Co, Mn, Zn, Ni, Pt, Ni, Sb, Te, Ti, V, Mo, Nb, B, Si, Ge and SnM 'is selected from any one or more of Si, C, B, Mg, Al, Zn, Sn, Cu, Fe, Ni, Mn, Co and Ti, and M' is selected from any one or more of Fe, Al, Co, Mn, Ni, Cr, Ti, V, Mg and Ru.

Further, the lithium supplement material has a median particle size of no greater than 30 μm, preferably no greater than 1 μm.

Further, the lithium supplement material is in a crystalline state, an amorphous state or a crystalline-amorphous mixed state.

Further, the electronic conductor material is one or more of amorphous carbon, conductive graphite, nano-graphite, conductive carbon black, carbon nanotubes, carbon fibers, fullerenes, graphene, conductive polymers or partially carbonized conductive polymers.

Further, the conductive polymer in the electronic conductor includes, but is not limited to, common conductive polymers and their derivatives, for example, polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene ethylene, polydiyne, and the like.

Further, the specific type of the adhesive is not particularly limited as long as it can perform an adhesive function, and may be any of hot melt type adhesives, solvent type adhesives, emulsion type adhesives, and solvent-free type adhesives, and may be selected according to actual needs. Preferably, the binder is PVDF.

Further, the dispersant is one or more of an inorganic dispersant, an organic dispersant and a polymer dispersant. The inorganic dispersant includes, but is not limited to, common polyphosphates and silicates, such as sodium pyrophosphate, trisodium phosphate, sodium hexametaphosphate, sodium metasilicate, sodium disilicate, and the like; the organic dispersant includes, but is not limited to, common anionic dispersants, nonionic dispersants, cationic dispersants, such as alkyl aryl sulfonate, polyoxyethylene alkyl phenol ether, trimethyl stearyl phthalide chloride, triethyl hexyl phosphoric acid, sodium dodecyl sulfate, methyl amyl alcohol, cellulose derivatives, etc.; the polymeric dispersant comprises polycarboxylate, polyacrylic acid derivative, maleic anhydride copolymer, nonionic water-soluble polymer and the like.

Further, the solvent is selected from one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, dimethylsulfoxide, tetrahydrofuran, water, methanol, ethanol, propanol, isopropanol, ethylene glycol, benzyl alcohol, acetone, acetonitrile, dimethyl carbonate, propylene carbonate, benzene, toluene, xylene, methyl ether, ethyl ether, and ethylene glycol dimethyl ether.

The invention also provides a preparation method of the composite lithium supplement slurry, which comprises the following steps:

providing a lithium supplement material, an electronic conductor material, a binder, a dispersant and a solvent in formula amounts;

and adding the lithium supplement material, the electronic conductor material, the binder and the dispersant into the solvent for uniform dispersion to obtain the composite conductive slurry.

The lithium-supplementing material, the electron-conducting material, the binder and the dispersant may be added to the solvent at one time or may be added in a plurality of times.

Further, the dispersing equipment can be a sand mill, a mechanical stirrer, a high-pressure homogenizer or an ultrasonic instrument as long as the dispersing equipment can achieve the purpose of uniform dispersion.

The invention also provides a positive pole piece coated by the composite lithium supplement slurry, in the mixing/pulping/size mixing/pulping stage of preparing the positive pole piece known in the technical field, the composite lithium supplement slurry, the positive active material, the binder and the conductive agent are added to obtain the positive pole slurry X, the second solvent is added to adjust the viscosity of the slurry to obtain the positive pole slurry, and the pole piece is prepared by the working procedures of coating, baking, rolling, die cutting and the like.

Further, the positive pole piece can be directly used as a positive pole piece of a lithium ion battery, and part of the electronic conductor and the lithium supplement material on the positive pole piece can be coated on the surface of the positive active material on the positive pole piece through a hot-pressing compounding process.

Further, the second solvent is preferably N-methylpyrrolidone.

Further, in the positive electrode slurry X, the mass ratio of the composite lithium supplementing slurry is A, the mass ratio of the positive electrode active material is B, the mass ratio of the binder is C, and the mass ratio of the conductive agent is D, wherein A is more than or equal to 0.1% and less than or equal to 50%, B is more than or equal to 50% and less than or equal to 99.9%, C is more than or equal to 0% and less than 20%, D is more than or equal to 0% and less than 10%, and A + B + C + D is 100%.

Further, the viscosity of the positive electrode slurry is 2000-10000mPa.s, preferably 4000-8000 mPa.s.

Furthermore, the hot pressing temperature adopted by the positive pole piece is 50-300 ℃, preferably 60-200 ℃, and the pressure is 0.1-100 MPa, preferably 0.5-60 MPa.

The invention also provides a lithium ion battery containing the positive pole piece prepared from the composite slurry, and the positive pole piece is used as the positive pole piece. The preparation process is known in the prior art and will not be described herein.

Compared with the prior art, the invention has the following advantages:

the composite lithium supplement slurry provided by the invention has a simple preparation process; the anode lithium supplement material in the slurry can effectively compensate lithium ions lost due to the formation of an SEI film in the charging and discharging process, so that more lithium ions can be inserted into the anode material again, the capacity of the anode material is improved, the whole lithium ion battery is ensured to have higher energy density, the conductivity of the material can be improved by the electronic conductor material, and the material can be further ensured to be rapidly de-inserted with lithium.

The partial lithium supplement material is coated on the surface of the positive active material, and the partial lithium removal material has low activity after lithium removal and can be used as an effective coating layer of a base material, so that side reactions with electrolyte can be reduced, and the cycling stability of the material is further improved.

After the negative electrodes with low initial efficiency such as silicon carbon are widely applied, the specific capacity of the material can be effectively improved by matching the positive electrode lithium supplement slurry, and the application of the material is more and more extensive.

Drawings

FIG. 1 is a scanning electron microscope image of a positive electrode sheet prepared in example 1 of the present invention;

FIG. 2 is a comparison graph of the first cycle charge and discharge curves of the liquid lithium ion batteries respectively prepared in example 1 and comparative example 1 of the present invention;

fig. 3 is a comparison chart of the cycles of the liquid lithium ion batteries respectively manufactured in example 1 and comparative example 1 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

In the following examples and comparative examples, materials, reagents and instruments used therein were commercially available or materials and reagents therein were prepared by a conventional method, unless otherwise specified.

Example 1

1) Preparation of composite lithium-supplementing slurry

20g of carbon nanotubes, 80gLi₅FeO₄10g of carboxymethyl cellulose and 10g of PVDF are added into 880g N-methyl pyrrolidone, and the mixture is dispersed for 60min by a sand mill at the rotating speed of 1500rpm to obtain composite lithium supplement slurry A₁；

299g of polyaniline, 31gLi₅FeO₄Adding into 670g N-methyl pyrrolidone, and dispersing for 40min at 1200rpm by a sand mill to obtain composite lithium supplement slurry A₂(ii) a 5g of carbon nanotubes, 1g of Li₂NiO₂4g of carboxymethyl cellulose and 10g of PVDF are added into 980g N-methyl pyrrolidone, and the composite lithium supplement slurry A is obtained by ultrasonic dispersion for 30min₃；

1g of graphene, 59gLi₅FeO₄15g of maleic acid-acrylic acid copolymer is added into 925g N-methyl pyrrolidone, and the mixture is dispersed for 50min by a sand mill at the rotating speed of 1500rpm to obtain the composite lithium supplement slurry A₄；

Mixing 11g of graphene and 299g of Li₂NiO₂90g of PVDF is added into 600g N-methyl pyrrolidone, and the mixture is dispersed for 90min by a sand mill at the rotating speed of 1500rpm to obtain the composite lithium supplement slurry A₅；

2) Preparation of positive electrode slurry

LiNi is selected as the positive electrode active material_0.9Co_0.07Mn_0.03O₂The particle diameter D50 was 10.5. mu.m.

50g of composite lithium supplementing slurry A₁90g of lithium cobaltate, 4g of conductive carbon black and 2g of PVDF are placed in a mixing tank to be uniformly stirred, and N-methyl pyrrolidone is added in the stirring process to adjust the viscosity to 6000mPa.s, so as to obtain anode slurry B₁；

1g of composite lithium supplementing slurry A₂、90g LiNi_0.9Co_0.07Mn_0.03O₂4g of conductive carbon black and 5g of PVD are put in a mixing tank to be uniformly stirred, N-methyl pyrrolidone is added in the stirring process to adjust the viscosity to 6000mPa.s, and anode slurry B is obtained₂；

40g of composite lithium supplementing slurry A₃、55g LiNi_0.9Co_0.07Mn_0.03O₂2g of conductive carbon black and 3g of PVDF are put in a mixing tank to be uniformly stirred, and N-methyl pyrrolidone is added in the stirring process to adjust the viscosity to 7000mPa.s, so as to obtain anode slurry B₃；

25g of composite lithium-supplementing slurry A₄、70g LiNi_0.9Co_0.07Mn_0.03O₂1g of conductive carbon black and 3g of PVDF are put in a mixing tank to be uniformly stirred, and N-methyl pyrrolidone is added in the stirring process to adjust the viscosity to 6000mPa.s, so as to obtain anode slurry B₄；

10g of composite lithium-supplementing slurry A₅、90g LiNi_0.9Co_0.07Mn_0.03O₂2g of conductive carbon black and 1g of PVDF are put in a mixing tank to be uniformly stirred, and N-methyl pyrrolidone is added in the stirring process to adjust the viscosity to 7500mPa.s, so as to obtain anode slurry B₅；

Respectively replacing the positive electrode active materials with LiNi_0.5Mn_1.5O₄D50 is 10.0 μm, each as for positive electrode slurry B₁～B₅The preparation method of (2) to obtain positive electrode slurry B₆～B₁₀；

3) The positive electrode slurry B obtained in the step 2)₁-B₁₀The positive pole piece C is prepared by the working procedures of coating, baking, rolling, die cutting and the like₁-C₁₀Wherein the scanning electron micrograph of the positive electrode plate in example 1 is shown in FIG. 1Shown in the figure.

Comparative examples 1 to 2

Comparative examples 1 to 2 positive electrode active materials LiNi of the materials of example 1 were used_0.9Co_0.07Mn_0.03O₂、LiNi_0.5Co_0.2Mn_0.3O₂。

1) Respectively adding 90g of LiNi_0.9Co_0.07Mn_0.03O₂、LiNi_0.5Mn_1.5O₄Adding 5g of conductive carbon black and 3g of PVDF into N-methyl pyrrolidone, uniformly stirring, adding N-methyl pyrrolidone during stirring to adjust the viscosity to 6000mPa.s, and obtaining anode slurry B₁₁And B₁₂；

2) The positive pole slurry obtained in the comparative example is processed by the working procedures of coating, baking, rolling, die cutting and the like to obtain a positive pole piece C₁₁And C₁₂。

Respectively taking the positive pole pieces obtained in the example 1 and the comparative example 1 as working electrodes and taking the silicon-carbon pole pieces as negative electrodes to assemble a liquid lithium ion battery and/or a mixed solid-liquid lithium ion battery, and carrying out charge and discharge tests on the batteries, wherein C₁～C₅And C₁₁The voltage range is 2.80-4.25V, C₆～C₁₀And C₁₂The voltage range is 2.80-4.50V, the charge-discharge specific capacity is tested at 0.1C/0.1C, the charge-discharge specific capacity is tested at 1C/1C, and the cycle capacity retention rate is tested for 100 weeks, and the results are shown in fig. 2-fig. 3 and table 1.

TABLE 1 comparison of specific charge-discharge capacity and cycling performance results

Fig. 2 is a first-cycle charge-discharge curve of the liquid lithium ion battery system in example 1 and comparative example 1, and it can be seen that the polarization of the lithium ion battery obtained in example 1 is smaller, the corresponding charge-discharge capacity is obviously improved, and the corresponding coulombic efficiency is improved. As can be seen from table 1, the charge and discharge capacity of the battery prepared by using the composite lithium supplement slurry is significantly improved, because the addition of the lithium supplement material can effectively compensate for the capacity reduction caused by lithium loss, and especially when the negative electrode material with low efficiency is used, the coulomb efficiency of the material can be effectively improved. Fig. 3 is a comparison graph of cycle performance of the liquid lithium ion battery system in example 1 and comparative example 1, the battery prepared by using the composite lithium supplement slurry has better cycle performance, and the lithium supplement material can be used as an effective coating layer to reduce the release of active substances and electrolyte and improve the cycle performance.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.