阅读说明：本技术 补锂导电浆料的制备方法、补锂导电浆料、锂离子电池及电子设备 (Preparation method of lithium supplement conductive paste, lithium ion battery and electronic equipment ) 是由 郭挺 史哲忠 解晖 孟嘉锋 王晓亚 于 2019-08-30 设计创作，主要内容包括：本公开提供了一种用于锂离子电池正极的补锂导电浆料的制备方法,包括以下步骤：S100、将正极补锂材料、导电剂、分散剂和溶剂混合均匀,制成混合料；S200、将混合料球磨,至所述正极补锂材料的平均粒径达到50-5000nm并形成均匀的补锂导电浆料。还进一步公开了一种补锂导电浆料、锂离子电池及电子设备。(The invention provides a preparation method of lithium-supplementing conductive slurry for a lithium ion battery anode, which comprises the following steps: s100, uniformly mixing the positive electrode lithium supplement material, the conductive agent, the dispersing agent and the solvent to prepare a mixture; s200, ball-milling the mixture until the average particle size of the anode lithium supplement material reaches 50-5000nm and forming uniform lithium supplement conductive slurry. Further disclosed are a lithium-supplementing conductive paste, a lithium ion battery and an electronic device.)

1. A preparation method of lithium-supplementing conductive slurry for a lithium ion battery anode comprises the following steps:

s100, uniformly mixing the positive electrode lithium supplement material, the conductive agent, the dispersing agent and the solvent to prepare a mixture;

s200, ball-milling the mixture until the average particle size of the anode lithium supplement material reaches 50-5000nm and forming uniform lithium supplement conductive slurry.

2. The method for preparing lithium-supplementing conductive paste according to claim 1, wherein the positive lithium-supplementing material is selected from Li₂O、Li₃N、Li₅FeO₄、Li₆CoO₄、Li₆MnO₄And Li₅VO₄At least one of (1).

3. The preparation method of the lithium-supplementing conductive paste according to claim 1 or 2, wherein the mass percentage of the positive electrode lithium-supplementing material in the lithium-supplementing conductive paste is 0.5-50%.

4. The preparation method of the lithium-supplementing conductive paste according to claim 3, wherein the mass percentage of the positive electrode lithium-supplementing material in the lithium-supplementing conductive paste is 2-20%.

5. The method for preparing lithium-supplementing conductive paste according to claim 1, wherein the conductive agent is at least one selected from the group consisting of conductive carbon black, conductive carbon nanotubes, conductive carbon nanofibers, and conductive carbon spheres.

6. The preparation method of the lithium-supplementing conductive paste according to claim 1 or 5, wherein the conductive agent is contained in the lithium-supplementing conductive paste by 0.01-20% by mass.

7. The preparation method of the lithium-supplementing conductive paste according to claim 6, wherein the conductive agent is contained in the lithium-supplementing conductive paste in an amount of 0.05 to 5% by mass.

8. The method for preparing lithium-supplementing conductive paste according to claim 1, wherein the dispersant is at least one selected from polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polytetrafluoroethylene, sodium carboxymethylcellulose, styrene-butadiene rubber, polyacrylic acid, lithium polyacrylate, and polyperfluorosulfonimide.

9. The preparation method of the lithium-supplementing conductive paste according to claim 1 or 8, wherein the mass percentage of the dispersant in the lithium-supplementing conductive paste is 0.2-10%.

10. The method for preparing lithium supplementing conductive paste according to claim 1, wherein the solvent is at least one selected from the group consisting of N-methyl pyrrolidone (NMP), ethanol, phenyl ether, toluene, xylene, hexane, cyclohexane, heptane, octane, decane, vinyl carbonate, dimethyl ether, diethyl ether, tetrahydrofuran, tetrahydropyran, dimethyl sulfoxide, and dimethylformamide.

11. The preparation method of the lithium-supplementing conductive paste according to claim 1, wherein in step S200, the mixture is ball-milled until the average particle size of the positive electrode lithium-supplementing material is 50-1000 nm.

12. The method for preparing lithium-supplementing conductive paste according to claim 1, wherein in step S200, the mixture is ball-milled until the average particle size of the positive lithium-supplementing material is 100-2000 nm.

13. A lithium-replenishing electroconductive paste obtained by the production method according to any one of claims 1 to 12.

14. A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein in the preparation process of the positive electrode, the lithium supplementing conductive paste of claim 13 is added into positive electrode paste.

15. The lithium ion battery according to claim 14, wherein the mass ratio of the positive electrode lithium supplement material to the positive electrode material is 0.1-10: 100.

16. the lithium ion battery of claim 14, wherein the first charge voltage of the lithium ion battery required by the positive electrode lithium supplement material to release lithium supplement capacity does not exceed 4.35V.

17. An electronic device, comprising: the lithium ion battery according to claim 14, and an electronic device main body, the lithium ion battery being used for supplying power to the electronic device main body.

Technical Field

The invention relates to a preparation method of lithium supplement conductive paste, a lithium ion battery and electronic equipment.

Background

In recent 20 years, lithium ion batteries have been rapidly developed as a new energy industry. The cathode material of the commercial lithium ion battery is mainly various graphite materials, and the theoretical specific capacity of the cathode material is 372 mAh/g. At present, the commercial graphite cathode material is close to the theoretical specific capacity, and the lifting space is very limited. With the market demand for high specific energy lithium ion batteries becoming higher and higher, the development and application of silicon-based negative electrode systems become more and more important. However, the silicon-based material, especially SiOx material, tends to have a problem of low coulombic efficiency for the first time, resulting in waste of the positive electrode material and reduction in the battery capacity. In order to further improve the energy density of the lithium ion battery, the method for supplementing lithium to the positive electrode or the negative electrode is an effective method.

Compared with the negative electrode lithium supplement, the positive electrode lithium supplement process is simple, the requirements on equipment and environment are relatively low, the using process is safer, and the cost is relatively low. Some lithium composite oxide positive electrode lithium-supplementing materials, such as Li, have been used in the prior art₅FeO₄、Li₆CoO₄And the like. The positive electrode lithium supplement materials can play a certain role in lithium supplement after being added into the positive electrode of the lithium ion battery. However, after the positive electrode lithium supplement material is decomposed, metal oxide remains, which affects battery performance and brings safety hazards. Meanwhile, the electron conductivity of the positive electrode lithium supplement material is low, so that the polarization is large during charging, and the lithium supplement capacity is difficult to completely release. With Li₂O is used as a positive electrode lithium supplement additive, the lithium supplement capacity is up to 1794mAh/g and is far higher than Li₅FeO₄、Li₆CoO₄And the like. Li₂Oxygen generated after O decomposition can be discharged after formation, and no residue is left after decomposition, so that the performance of the battery is not influenced. However, Li₂O has extremely poor conductivity, so that the decomposition overpotential is very large and the O is not easy to decompose. Even if Li is present₂O decomposes at very high voltages, and the risk of lithium precipitation is likely to occur because the amount of lithium released from the positive electrode increases greatly after the voltage increases. These factors limit Li₂And O is used as a positive electrode lithium supplement material. In the prior art, by incorporating Li₂O is doped or compounded with a material having excellent conductivity to increase Li₂Conductivity of O and reduction of decomposition overpotential. However, these methods still have problems such as residual impurities after decomposition and difficulty in production. In addition, reduction of Li₂The particle size of O is also effective in reducing its decomposition potential, however directly to Li₂The O grinding has the problems of secondary agglomeration, easy side reaction and the like。

Disclosure of Invention

In order to solve the technical problem, the embodiment of the present disclosure provides a preparation method of a lithium supplement conductive paste for a lithium ion battery anode.

According to the preparation method of the lithium-supplementing conductive slurry, the anode lithium-supplementing material, the conductive agent and the dispersing agent are subjected to ball milling and stable dispersion, so that the particle size of the anode lithium-supplementing material is reduced, the contact between the anode lithium-supplementing material and the conductive agent is increased, the conductivity is improved, and the overpotential of the anode lithium-supplementing material during charging decomposition is effectively reduced. Meanwhile, due to the existence of a dispersing agent and a solvent, the lithium-supplemented material of the positive electrode after ball milling is not easy to agglomerate to form secondary large particles. In addition, the solvent can isolate the contact between the anode lithium supplement material and air, and prevent the side reaction of the lithium supplement material with moisture and carbon dioxide, thereby effectively improving the storage property. The positive electrode lithium-supplementing conductive slurry is particularly suitable for a lithium ion battery system containing a negative electrode material with high specific capacity and low initial coulombic efficiency, and the negative electrode material with high specific capacity and low initial coulombic efficiency is silicon carbon, silicon oxygen, hard carbon or soft carbon material and the like.

One embodiment of the invention provides a preparation method of a lithium-supplementing conductive paste for a lithium ion battery anode, which comprises the following steps:

s100, uniformly mixing the positive electrode lithium supplement material, the conductive agent, the dispersing agent and the solvent to prepare a mixture;

s200, ball-milling the mixture until the average particle size of the anode lithium supplement material reaches 50-5000nm and forming uniform lithium supplement conductive slurry.

The positive electrode lithium-supplementing material in step S100 may be selected from Li₂O、Li₃N、Li₅FeO₄、Li₆CoO₄、Li₆MnO₄And Li₅VO₄At least one of (1). Wherein Li₂The electrical conductivity of O is the worst, and Li is obtained after the lithium-supplementing conductive slurry is prepared by the preparation method₂The lithium supplementing effect of O is improved more obviously. Optionally, the mass percentage of the positive electrode lithium supplement material in the lithium supplement conductive paste is 0.5-50%. At another placeIn a possible embodiment, the mass percentage of the positive electrode lithium supplement material in the lithium supplement conductive paste is 2-20%, or the mass percentage of the positive electrode lithium supplement material in the lithium supplement conductive paste is 5-30%.

The conductive agent in step S100 may be at least one selected from conductive carbon black, conductive carbon nanotubes, conductive carbon nanofibers, and conductive carbon spheres. Conductive carbon nanotubes with high aspect ratios are preferred. Optionally, the content of the conductive agent in the lithium-supplement conductive paste is 0.01-20% by mass. In another possible embodiment, the content of the conductive agent in the slurry is 0.05-5% by mass.

The dispersant in step S100 may be at least one selected from polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polytetrafluoroethylene, sodium carboxymethylcellulose, styrene-butadiene rubber, polyacrylic acid, lithium polyacrylate, and polyperfluorosulfonimide. If the positive electrode homogenate contains PVDF, the preferable dispersant in the lithium-supplementing conductive paste is PVDF. Generally, the mass percentage of the dispersing agent in the lithium-supplementing conductive slurry is 0.2-10%. In another possible embodiment, the dispersant is present in the slurry in an amount of 0.5 to 5% by weight.

The solvent used in step S100 may be at least one selected from the group consisting of N-methyl pyrrolidone (NMP), ethanol, phenyl ether, toluene, xylene, hexane, cyclohexane, heptane, octane, decane, vinyl carbonate, dimethyl ether, diethyl ether, tetrahydrofuran, tetrahydropyran, dimethyl sulfoxide, and dimethylformamide. If the positive electrode slurry contains NMP, the preferred solvent in the lithium-supplemented conductive slurry is NMP.

Since the commercial conductive agent slurry in the market already contains the conductive agent, the dispersant and the solvent, the positive electrode lithium supplement material and the commercial conductive agent slurry can be directly and uniformly mixed in step S100 to prepare a mixture.

The proper particle size in step S200 refers to the average particle size of the positive electrode lithium supplement material after ball milling. In one possible embodiment, the average particle size of the positive electrode lithium-supplementing material after ball milling is 50 to 5000 nm. In another possible embodiment, the average particle size of the positive electrode lithium supplement material after ball milling is 50-1000nm, or the average particle size of the positive electrode lithium supplement material after ball milling is 100-2000 nm.

The main purpose of ball milling in step S200 is to reduce the particle size of the positive electrode lithium supplement material, increase the contact between the positive electrode lithium supplement material and the conductive agent, and form a stable slurry. It is understood that the rotation speed and time of the ball mill can be selected by those skilled in the art according to the nature and amount of the slurry. For example, the rotation speed of the ball mill can be selected from 200rpm to 3000rpm, and the ball milling time can be selected from 1h to 30 h.

In another aspect, the embodiment of the present disclosure provides a lithium supplement conductive paste obtained by the above preparation method.

In another aspect, the embodiment of the present disclosure provides a lithium ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein in a positive electrode preparation process, the lithium supplement conductive paste as described above is added to a positive electrode paste.

And preparing the battery by adopting the lithium-supplementing conductive slurry. In the preparation process of the battery, the lithium-supplementing conductive slurry can be added in the anode homogenizing process. The addition can be performed before the addition of the positive electrode material, simultaneously with the addition of the positive electrode material, or after the addition of the positive electrode material. The addition can be carried out in one time or in several times. The adding sequence and method of the lithium-supplementing conductive slurry can be adjusted according to the specific production process, and no specific requirements are made here. The positive electrode homogenizing process may be carried out by a usual operation technique, and is not particularly limited.

The positive electrode material suitable for the lithium-supplementing conductive paste can be selected from LiCoO₂、LiMn₂O₄、LiFePO₄And at least one of a nickel-cobalt-manganese ternary positive electrode material (NCM), a nickel-cobalt-aluminum ternary positive electrode material (NCA), a nickel-cobalt-manganese-aluminum (NCMA) quaternary positive electrode material, and a lithium-rich positive electrode (including a lithium-rich manganese-based positive electrode, etc.).

In the preparation process of the battery, the addition amount of the lithium supplementing conductive slurry is determined according to the mass ratio of the positive electrode lithium supplementing material to the positive electrode material. Generally, the mass ratio of the positive electrode lithium supplement material to the positive electrode material is 0.1-10: 100. in another possible embodiment, the mass ratio of the positive electrode lithium supplement material to the positive electrode material is 0.5-6: 100.

in one possible embodiment, the first charge voltage of the lithium ion battery required by the positive electrode lithium supplement material to release the lithium supplement capacity does not exceed 4.35V. The battery prepared by the lithium-supplementing conductive paste has the advantages that the first charging voltage is usually not more than 4.3V, and the lithium-supplementing capacity can be released by the positive electrode lithium-supplementing material, so that the aim of the invention is fulfilled. For some battery systems, for example, the positive electrode material is LiCoO₂Or Li₂Mn₂O₄The first charge voltage of the system (2) can be 4.35V or more to fully utilize the capacity of the positive electrode material.

Another aspect of the disclosed embodiments provides an electronic device, including: the lithium ion battery described above is used to supply power to the electronic device main body. The electronic equipment can be an electric automobile or an energy storage device.

Compared with the prior art, the technical scheme has the advantages that the contact between the positive electrode lithium supplement material and the conductive agent is better, and the overpotential during charging decomposition is smaller. The positive electrode lithium supplement material has better dispersibility, stability and storage property. In addition, the lithium-supplementing conductive slurry is simple in preparation process, low in cost, convenient to use and safe. The lithium-supplementing conductive slurry can effectively improve the capacity exertion of the anode material, and is particularly suitable for a lithium ion battery system containing a cathode with high specific capacity and low initial coulombic efficiency.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

160g of Li₆CoO₄And 1000g of commercial conductive agent slurry, wherein the commercial conductive agent slurry comprises 0.4% of single-walled carbon nanotubes, 2% of PVDF and the balance of NMP. Ball milling was carried out at 500rpm for 1.5h and the resulting slurry was collected. Measuring Li in slurry by using Malvern particle size analyzer₆CoO₄Has an average particle diameter (D50) of 530 nm.

Example 2

20g of Li₂And uniformly mixing the O with 1000g of commercial conductive agent slurry, wherein the commercial conductive agent slurry comprises 3% of multi-walled carbon nanotubes, 1% of PVP and the balance of NMP. Ball milling was carried out at 1000rpm for 2.5h and the resulting slurry was collected. Measuring Li in slurry by using Malvern particle size analyzer₂The average particle diameter of O (D50) was about 300 nm.

Example 3

80g of Li₅FeO₄70g of PVDF, 20g of VGCF as a conductive agent and 1000g of NMP were uniformly mixed, and then ball-milled at a rotation speed of 300rpm for 2 hours, and the obtained slurry was collected. Measuring Li in slurry by using Malvern particle size analyzer₅FeO₄Has an average particle diameter (D50) of 820 nm.

First set of comparative experiments:

reference example 4.1

0.949kg of NCM523, 0.020kg of conductive agent Super-P, 0.025kg of adhesive PVDF, 0.250kg of commercial conductive slurry and 0.450kg of solvent NMP were stirred and homogenized to prepare positive electrode slurry. The commercial conductive slurry contains 0.5% of single-walled carbon nanotubes, 2% of dispersant PVDF and the balance of NMP. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 4.2

0.949kg of NCM523, 0.020kg of conductive agent Super-P, 0.025kg of adhesive PVDF, 0.250kg of commercial conductive paste, 0.450kg of solvent NMP, 0.020kg of Li with an average particle size of 20 mu m₆CoO₄Stirring and homogenizing to prepare the anode slurry. Wherein, the commercial conductive slurry contains 0.5 percent of single-walled carbon nano-tube and 2 percent of dispersant PVDF. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 4.3

0.949kg of NCM523, 0.020kg of conductive agent Super-P, 0.025kg of adhesive PVDF, 0.250kg of commercial conductive paste, 0.450kg of solvent NMP, 0.020kg of Li with an average particle size of 530nm₆CoO₄Stirring and homogenizing to prepare the anode slurry. Wherein, the commercial conductive slurry contains 0.5 percent of single-walled carbon nano-tube and 2 percent of dispersant PVDF. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Example 4.4

0.949kg of NCM523, 0.020kg of conductive agent Super-P, 0.025kg of adhesive PVDF, 0.125kg of commercial conductive slurry, 0.145kg of the positive electrode lithium-supplemented conductive slurry of example 1, and 0.450kg of solvent NMP were stirred and homogenized to prepare positive electrode slurry. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

The negative electrode is made of hard carbon, Styrene Butadiene Rubber (SBR), sodium carboxymethylcellulose (CMC) and a conductive agent Super-P, and the hard carbon, the SBR, the CMC and the conductive agent Super-P are added into deionized water according to the mass ratio of 94:2.5:2:1.5 to be stirred and homogenized to prepare negative electrode slurry; coating the two sides of the negative electrode slurry on a negative electrode current collector, and drying, compacting, slitting, cutting and welding tabs to obtain a negative electrode plate.

In reference example 4.1, comparative example 4.2, comparative example 4.3, and example 4.4, the preparation conditions were the same except for the positive electrode slurry, including the same current collector foil, the same active material content per unit area of the positive and negative electrode sheets, the same coating length and width of the positive and negative electrode sheets, and the same electrolyte solution.

Assembling the negative pole piece and the positive pole piece prepared by the process with a diaphragm to prepare a battery cell, filling the battery cell into an outer package, injecting electrolyte into the outer package, sealing, pre-charging, and forming to prepare the lithium ion secondary battery.

Description of the test methods:

at 25 +/-2 ℃, different battery cores are taken and respectively charged to 4.2 and 4.3V at a constant current of 1600mA, and then respectively charged to a constant voltage of 4.2 and 4.3V until the current is less than 240 mA. The mixture was left for 10 minutes and discharged to 2.7V at a constant current of 1600mA to obtain a discharge capacity.

Second set of comparative tests:

reference example 5.1

0.930kg of LiCoO₂0.010kg of conductive agent Super-P, 0.040kg of adhesive PVDF, 0.500kg of commercial conductive slurry, and 0.200kg of solvent NMP. Wherein, the commercial conductive paste contains 3 percent of multi-wall carbon nano-tube and 1 percent of dispersant PVP. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 5.2

0.930kg of LiCoO₂0.010kg of conductive agent Super-P, 0.040kg of adhesive PVDF, 0.500kg of commercial conductive paste, 0.200kg of solvent NMP, 0.010kg of Li with an average particle size of 7 mu m₂And O, stirring and homogenizing to prepare the anode slurry. Wherein, the commercial conductive paste contains 3 percent of multi-wall carbon nano-tube and 1 percent of dispersant PVP. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 5.3

0.930kg of LiCoO₂0.010kg of conductive agent Super-P, 0.040kg of adhesive PVDF, 0.500kg of commercial conductive paste, 0.200kg of solvent NMP, 0.010kg of Li with the average particle size of 300nm₂And O, stirring and homogenizing to prepare the anode slurry. Wherein, the commercial conductive paste contains 3 percent of multi-wall carbon nano-tube and 1 percent of dispersant PVP. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Example 5.4

0.930kg of LiCoO₂0.010kg of conductive agent Super-P, 0.040kg of adhesive PVDF, 0.510kg of the positive electrode lithium-supplementing conductive slurry in the embodiment 2 and 0.200kg of solvent NMP are stirred and homogenized to prepare positive electrode slurry. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

The negative electrode is made of silicon carbon material, graphite, SBR, CMC and conductive agent Super-P, and is added into deionized water according to the weight ratio of 14:80:2.5:2:1.5 to be stirred and homogenized to prepare negative electrode slurry; coating the two sides of the negative electrode slurry on a negative electrode current collector, and drying, compacting, slitting, cutting and welding tabs to obtain a negative electrode plate.

In reference example 5.1, comparative example 5.2, comparative example 5.3, and example 5.4, the current collector foils were the same, the active material contents per unit area of the positive and negative electrode sheets were the same, the coating lengths and widths of the positive and negative electrode sheets were the same, and the electrolytes were used in the same manner.

Assembling the negative pole piece and the positive pole piece prepared by the process with a diaphragm to prepare a battery cell, filling the battery cell into an outer package, injecting electrolyte into the outer package, sealing, pre-charging, and forming to prepare the lithium ion secondary battery.

Description of the test methods:

at 25 +/-2 ℃, different battery cores are taken and respectively charged to 4.3 and 4.5V at constant current of 1667mA, and then respectively charged to the current of less than 250mA at constant voltage of 4.3 and 4.5V. After leaving for 10 minutes, the discharge was carried out at a constant current of 1667mA until reaching 3.0V to obtain a discharge capacity.

Third set of comparative experiments:

reference example 6.1

0.94kg of NCA, 0.015kg of conductive agent Super-P, 0.010kg of conductive agent VGCF, 0.035kg of adhesive PVDF and 0.7kg of solvent NMP are stirred and homogenized to prepare positive electrode slurry. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 6.2

0.940kg of NCA, 0.015kg of conductive agent Super-P, 0.010kg of conductive agent VGCF, 0.035kg of adhesive PVDF, 0.700kg of solvent NMP, 0.040kg of Li having an average particle size of 30 μm₅FeO₄Stirring and homogenizing to prepare the anode slurry. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Comparative example 6.3

0.940kg of NCA, 0.015kg of conductive agent Super-P, 0.010kg of conductive agent VGCF, 0.035kg of adhesive PVDF, 0.700kg of solvent NMP, 0.040kg of Li with the average particle size of 820nm₅FeO₄Stirring and homogenizing to prepare the anode slurry.Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

Example 6.4

0.940kg of NCA, 0.015kg of conductive agent Super-P, 0.585kg of the positive electrode lithium-supplementing conductive slurry of example 3 and 0.200kg of solvent NMP were stirred and homogenized to prepare a positive electrode slurry. Coating the two sides of the positive electrode slurry on a positive electrode current collector, and drying, compacting, cutting pieces and welding tabs to obtain the positive electrode piece.

The negative electrode is a silica material, graphite, SBR, CMC, a conductive agent Super-P and a conductive agent VGCF, and the materials are added into deionized water according to the weight ratio of 13:80:2.5:2:1.5:1 and stirred and homogenized to prepare negative electrode slurry; coating the two sides of the negative electrode slurry on a negative electrode current collector, and drying, compacting, slitting, cutting pieces and welding tabs to obtain a negative electrode piece.

Description of the test methods:

at 25 +/-2 ℃, different battery cores are taken and respectively charged to 4.15 and 4.25V at a constant current of 1500mA, and then respectively charged to a constant voltage of 4.15 and 4.25V until the current is less than 225 mA. The mixture was left for 10 minutes and discharged to 2.5V at a constant current of 1500mA to obtain a discharge capacity.

According to the reference example, the comparative example and the embodiment, the first charge and discharge specific capacity of the positive electrode in different samples is calculated according to the total mass of the positive electrode active material of the battery and the charge and discharge capacity of the corresponding battery, and the lithium supplement condition of the positive electrode is compared and analyzed, which is shown in the following tables 1, 2 and 3.

TABLE 1 test results of the first set of comparative tests

TABLE 2 test results of the second set of comparative tests

TABLE 3 test results of the third set of comparative tests

The results of comparative reference 4.1, comparative example 4.3 and example 4.4 are: under the primary charging voltage of 4.2V, the primary charging and discharging capacity of the corresponding lithium ion battery in the comparative example is lower, and the designed lithium supplement capacity is not reached; while the examples have reached the designed lithium replenishment capacity. Both comparative examples and examples can achieve the designed lithium replenishment capacity at a first charge voltage of 4.3V. Comparative example 4.2, comparative example 4.3 and example 4.4 show that: although reducing the particle size can increase Li₆CoO₄But Li in the examples₆CoO₄The decomposition degree is higher, and a better lithium supplementing effect is obtained.

Comparative reference example 5.1, comparative example 5.3 and example 5.4 are known; under the primary charging voltage of 4.3V, the primary charging and discharging capacity of the corresponding lithium ion battery in the comparative example is lower, and the designed lithium supplement capacity is not reached; while the examples have reached the designed lithium replenishment capacity. At the initial charging voltage of 4.5V, the Li2O decomposition degree in the comparative example is improved, but the designed lithium supplement capacity is not completely reached; while the examples have reached the designed lithium replenishment capacity. Comparative example 5.2, comparative example 5.3 and example 5.4 show that: the reduction of the particle size can significantly improve Li₂Degree of decomposition of O, but Li in examples₂The decomposition degree of O is higher, and a better lithium supplementing effect is obtained.

Comparative reference example 6.1, comparative example 6.3 and example 6.4 are known; under the primary charging voltage of 4.15V, the primary charging and discharging capacity of the corresponding lithium ion battery in the comparative example is lower, and the designed lithium supplement capacity is not reached; while the examples have reached the designed lithium replenishment capacity. Li in comparative example at a first charge voltage of 4.25V₅FeO₄The decomposition degree is improved, and the lithium supplement capacity is designed according to the embodiment. Comparative example 6.2, comparative example 6.3 and example 6.4 show: the reduction of the particle size can significantly improve Li₅FeO₄But Li in the examples₅FeO₄The decomposition degree is higher, and a better lithium supplementing effect is obtained.

Compared with the method of directly adding the anode lithium supplement material, the anode lithium supplement conductive slurry of the invention has the advantages that the voltage required for completely decomposing the anode lithium supplement material to achieve the lithium supplement effect is lower, and the lithium supplement effect on Li is realized₂O is especially pronounced. The preparation method provided by the invention has the advantages that after the anode lithium-supplementing conductive slurry is prepared, the conductivity and the dispersibility of the anode lithium-supplementing material are improved, the overpotential during charging decomposition is smaller, and the lithium supplementing effect is better.