阅读说明：本技术 一种锂离子电池正极极片及其制备方法 (Lithium ion battery positive pole piece and preparation method thereof ) 是由 谈亚军 赵成龙 陈梦婷 于 2021-08-30 设计创作，主要内容包括：本发明属于锂离子电池技术领域,具体涉及一种锂离子电池正极极片及其制备方法,所述锂离子电池正极极片,包括集流体和涂覆在集流体表面的正极涂层,所述正极涂层包括正极活性材料、导电剂和粘结剂,所述正极活性材料为单晶三元材料和富锂锰基材料形成的复合物。本发明的单晶三元材料和富锂锰基材料可在锂电池生产过程中直接复合,进而制备出锂电池用正极极片,成本低,易于工业化生产；该正极片制备的锂离子电池可应用于4.3V及以上电压,具备高能量密度、低成本的特点；富锂锰基的存在可以补充循环过程中消耗的Li,一定程度减缓寿命衰减；该正极片匹配首次效率偏低的硅碳负极时,克服了硅碳负极首效偏低的缺陷。(The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery positive pole piece and a preparation method thereof. The single crystal ternary material and the lithium-rich manganese-based material can be directly compounded in the production process of the lithium battery, so that the positive pole piece for the lithium battery is prepared, the cost is low, and the industrial production is easy to realize; the lithium ion battery prepared by the positive plate can be applied to voltages of 4.3V and above, and has the characteristics of high energy density and low cost; the existence of the lithium-rich manganese base can supplement Li consumed in the circulation process, and the service life decay is slowed down to a certain extent; when the positive plate is matched with a silicon-carbon negative electrode with low efficiency for the first time, the defect of low first effect of the silicon-carbon negative electrode is overcome.)

1. A positive pole piece of a lithium ion battery comprises a current collector and a positive coating coated on the surface of the current collector, wherein the positive coating comprises a positive active material, a conductive agent and a binder, and is characterized in that the positive active material is a compound formed by a single crystal ternary material and a lithium-rich manganese-based material,

the general formula of the single crystal ternary material is Li_xNi_yCo_zM_1-y-zO₂Wherein x is more than or equal to 1.0 and less than or equal to 1.1, y is more than or equal to 0.5 and less than or equal to 0.7, z is more than 0 and less than or equal to 0.2, and M is selected from one or more of Mn, Mg, Al, Ti, Ca, Sr, Cr and Ba;

the general formula of the lithium-rich manganese-based material is nLi₂MnO₃·(1-n)LiM'O₂Wherein n is more than 0 and less than 1, and M' is one or more selected from Ni, Co, Mn, Mg, Al, V, Zn, Ti, Fe and Cr.

2. The positive electrode plate of the lithium ion battery of claim 1, wherein the molecular formula of the single crystal ternary material is LiNi_0.55Co_0.15Mn_0.3O₂。

3. The positive electrode plate of the lithium ion battery as claimed in claim 1 or 2, wherein the single crystal ternary material has a particle median diameter D50 of 3-8 μm and a specific surface area of 0.3-0.8m²/g。

4. The positive pole piece of the lithium ion battery of claim 1, wherein n is greater than or equal to 0.2 and less than or equal to 0.4 in the general formula of the lithium-rich manganese-based material.

5. The positive electrode sheet of the lithium ion battery of claim 1, wherein the lithium-rich manganese-based material has a chemical formula of Li_1.15Ni_0.35Mn_0.5O₂。

6. The positive electrode plate of the lithium ion battery of any one of claims 1, 4 or 5, wherein the lithium-rich manganese-based material has a particle median diameter D50 of 5-10 μm and a specific surface area of 0.5-1.0m²/g。

7. The positive electrode sheet of the lithium ion battery of claim 1, wherein the mass of the lithium-rich manganese-based material is 20-50% of the total mass of the positive active material.

8. The preparation method of the positive pole piece of the lithium ion battery of any one of claims 1 to 7, which comprises the following steps,

s1: placing the carbon nano tube, the binder and the solvent in a closed container and stirring;

s2: adding conductive carbon black, graphite and a single crystal ternary material, and continuously stirring;

s3: adding a lithium-rich manganese-based material, and continuously stirring to obtain a slurry stock solution;

s4: adjusting the viscosity of the slurry stock solution to 14000-160000mpa.s, and continuously stirring to obtain anode slurry;

s5: and coating the positive coating on the surface of the current collector to obtain the lithium ion battery positive pole piece.

9. The method of claim 8, wherein the binder is carboxymethyl cellulose or polyvinylidene fluoride.

10. The method of claim 8, wherein the solvent is one or more of N-methylpyrrolidone, cyclohexanone, acetone, and isopropanol.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery positive pole piece and a preparation method thereof.

Background

In the current lithium ion battery system, the specific capacity of the whole battery is mainly limited by the capacity of the anode material. In addition, in the production of batteries, the cost of the positive electrode material accounts for more than 30% of the total material cost. Therefore, the cathode material with low preparation cost and high energy density is an important target for the research and production of the lithium ion battery at present.

At present, the existing ternary material synthesis process is optimized by a main material factory, the stability of the material is improved by doping or generating a single crystal structure, the upper limit working voltage of the battery can be improved to 4.3V or above, the gram capacity and the platform voltage of the material are improved, and the energy density of the system is improved. Such as patents CN201810214611.4 and CN 202011243928.4.

Due to process optimization, doping and cladding, the cost is greatly improved. In addition, the increase of the working voltage of the battery (4.3V and above) also causes the increase of side reaction, the increase of Li consumption, the great attenuation of cycle performance and the reduction of safety performance to a certain extent.

The specific discharge capacity of the lithium-rich manganese material exceeds 250 mAh.g^-1The lithium ion battery has high working upper limit voltage (4.2-4.8V), high safety and obvious cost advantage, is expected to become a next-generation lithium ion anode material capable of being industrialized, and has great commercial prospect.

In the prior art, the Chinese patent with the application number of CN201810568955.5 discloses a lithium ion battery anode material and a preparation method thereof, wherein the preparation method comprises the steps of firstly preparing a single crystal ternary material, a lithium-rich manganese-based material and MoO₃Fully mixing, sintering at high temperature for a certain time, naturally cooling to room temperature, and performing the sintering process and the cooling process in an oxygen atmosphere with the purity of more than 99.5%. And then, the anode material can be obtained by crushing, sieving and other treatments and is used for preparing the lithium battery. MoO introduced in the technical scheme of the invention₃Acting as an important shell role, the lack of MoO can be found by comparing samples₃The cycle performance is greatly reduced. Simultaneous MoO₃No capacity is available and additional costs are added. The whole anode material pre-synthesis process is complex, has high requirements on environment and high cost, and is not beneficial to industrial application.

Disclosure of Invention

The invention aims to provide a lithium ion battery positive pole piece and a preparation method thereof, which have the advantages of low cost, capability of slowing down the life attenuation, simple preparation process and easiness in industrial production.

According to the calculation scheme of the invention, the lithium ion battery positive pole piece comprises a current collector and a positive coating coated on the surface of the current collector, wherein the positive coating comprises a positive active material, a conductive agent and a binder, and is characterized in that the positive active material is a compound formed by a single crystal ternary material and a lithium-rich manganese-based material,

the general formula of the single crystal ternary material is Li_xNi_yCo_zM_1-y-zO₂Wherein x is more than or equal to 1.0 and less than or equal to 1.1, y is more than or equal to 0.5 and less than or equal to 0.7, z is more than 0 and less than or equal to 0.2, and M is selected from one or more of Mn, Mg, Al, Ti, Ca, Sr, Cr and Ba;

the general formula of the lithium-rich manganese-based material is nLi₂MnO₃·(1-n)LiM'O₂Wherein n is more than 0 and less than 1, and M' is one or more selected from Ni, Co, Mn, Mg, Al, V, Zn, Ti, Fe and Cr.

Furthermore, the molecular formula of the single crystal ternary material is LiNi_0.55Co_0.15Mn_0.3O₂(nickel 55 ternary) can reach the highest performance priceAnd (4) the ratio.

Furthermore, the median particle diameter D50 of the single crystal ternary material particles is 3-8 μm, and the specific surface area is 0.3-0.8m²/g。

Furthermore, in order to achieve better capacity and stability of the material, n is more than or equal to 0.2 and less than or equal to 0.4 in the general formula of the lithium-rich manganese-based material, preferably, the chemical formula of the lithium-rich manganese-based material is Li_1.15Ni_0.35Mn_0.5O₂(n＝1.5)。

Furthermore, the lithium-rich manganese-based material has a particle median diameter D50 of 5-10 μm and a specific surface area of 0.5-1.0m²/g。

Further, the mass of the lithium-rich manganese-based material is 20-50% of the total mass of the positive electrode active material.

Furthermore, the upper limit working voltage of the battery manufactured by the lithium ion battery anode pole piece can be 4.3V or above.

The invention also provides a preparation method of the anode piece of the lithium ion battery, which comprises the following steps,

s1: placing the carbon nano tube, the binder and the solvent in a closed container and stirring;

s2: adding conductive carbon black, graphite and a single crystal ternary material, and continuously stirring;

s3: adding a lithium-rich manganese-based material, and continuously stirring to obtain a slurry stock solution;

s4: adjusting the viscosity of the slurry stock solution to 14000-160000mpa.s, and continuously stirring to obtain anode slurry;

s5: and coating the positive coating on the surface of the current collector to obtain the lithium ion battery positive pole piece.

Further, in the step S1, the stirring time is 40-90 min; in the step S2, the stirring time is 40-90 min; in the step S3, the stirring time is 40-90 min; in the step S4, the stirring time is 80-180 min.

Further, in step S1, the viscosity of the slurry stock solution is adjusted by adding one or more of N-methyl pyrrolidone, cyclohexanone, acetone, and isopropanol.

Further, the binder is carboxymethyl cellulose or polyvinylidene fluoride.

Further, the solvent is one or more of N-methyl pyrrolidone, cyclohexanone, acetone and isopropanol.

Further, the current collector is an aluminum foil.

Specifically, the preparation method of the positive pole piece of the lithium ion battery can comprise the following steps,

s1: placing the carbon nano tube slurry, the polyvinylidene fluoride sizing material and the solvent N-methyl pyrrolidone in a closed container and stirring for 40-90 min;

s2: adding conductive carbon black, graphite and single crystal ternary materials, and continuously stirring for 40-90 min;

s3: adding a lithium-rich manganese-based material, and continuously stirring to obtain a slurry stock solution for 40-90 min;

s4: adjusting the viscosity of the slurry stock solution to 14000-160000mpa.s, and continuously stirring for 80-180min to obtain anode slurry;

s5: and coating the positive coating on the surface of an aluminum foil to obtain the positive pole piece of the lithium ion battery.

Further, the mass ratio of the carbon nanotube slurry, the conductive carbon black and the graphite in the conductive agent is 40: 0.8-1.2: 0.8-1.2. Further, the mass ratio of the conductive agent to the polyvinylidene fluoride sizing material is 12-18: 1.

compared with the prior art, the technical scheme of the invention has the following advantages:

1. the single crystal ternary material and the lithium-rich manganese-based material which are active materials of the positive electrode can be directly added and compounded in the production process of the lithium battery, so that the positive electrode piece for the lithium battery is prepared, the cost is low, and the industrial production is easy to realize;

2. the lithium ion battery prepared by the positive plate has the characteristics of high energy density and low cost;

3. the existence of the lithium-rich manganese base can supplement Li consumed in the circulation process, and the service life decay is slowed down to a certain extent;

4. when the positive plate is matched with a silicon-carbon negative electrode with low efficiency for the first time, the negative electrode can be pre-lithiated at the initial stage of circulation, so that the defect of low first effect of the silicon-carbon negative electrode is overcome.

Drawings

FIG. 1 is a graph of the normal temperature 1C/1C cycle performance of cells A, B and C of example 1, comparative example 1, and comparative example 2.

FIG. 2 is a graph of the high temperature 1C/1C cycle performance of cells A, B and C in example 1, comparative example 1, and comparative example 2.

FIG. 3 is a graph showing the normal temperature 1C/1C cycle performance of examples 1 and 2.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Example 1

The mass percentage of the lithium-rich manganese-based material in the positive electrode active material is 50%:

1) checking the air tightness of the batching pot, adding 800g of carbon nanotube slurry (LB 100-50, Jiangsu Tiannai science and technology Co., Ltd.) and 56g of polyvinylidene fluoride glue solution (HEVER 601, Daiyuan Dongyang fluororesin Co., Ltd.), adding 500g of N-methyl pyrrolidone, and stirring for 60 min;

2) the batch pot was opened and 20g of conductive carbon black, 20g of graphite and 2400g of single crystal ternary material LiNi were added_0.55Co_0.15Mn_0.3O₂(ternary Ni 55, median particle diameter D50 of 3-8 μm, specific surface area of 0.3-0.8m²(g) stirring for 60 min;

3) the batch pot was opened and 2400g of Li-rich manganese-based material Li were added_1.15Ni_0.35Mn_0.5O₂(the median particle diameter D50 is 5-10 μm, and the specific surface area is 0.5-1.0m²Stirring for 60min to obtain a slurry stock solution;

4) finally, adjusting the viscosity of the slurry stock solution to about 15000mpa.s by adding N-methyl pyrrolidone, and continuously stirring for 120min to obtain anode slurry;

and preparing the positive electrode slurry into a positive plate, assembling the positive plate and a conventional negative electrode with graphite as an active material to form a battery A, and testing the electrical property.

Comparative example 1

Pure single crystal ternary material system:

1) checking the air tightness of the batching pot, adding 800g of carbon nanotube slurry and 56g of polyvinylidene fluoride glue solution after ensuring no abnormal air tightness, adding 500g N-methyl pyrrolidone, and stirring for 60 min;

2) opening the batching pot, adding 20g of conductive carbon black, 20g of graphite and 4800g of nickel 55 ternary, and stirring for 60min to obtain a slurry stock solution;

3) finally, adjusting the viscosity of the slurry stock solution to about 15000mpa.s by adding N-methyl pyrrolidone, and continuously stirring for 120min to obtain anode slurry;

and preparing the positive electrode slurry into a positive plate, assembling the positive plate and a conventional negative electrode with graphite as an active material to form a battery B, and testing the electrical property.

Comparative example 2

Pure lithium-rich manganese-based material system:

on the basis of the comparative example 1, the nickel 55 in the step 2 is replaced by a lithium-rich manganese-based material Li in a ternary way_1.15Ni_0.35Mn_0.5O₂And similarly, preparing the positive electrode slurry into an electrode, assembling the electrode and a conventional negative electrode material taking graphite as an active material into a battery C, and testing the electrical property.

Example 2

The content of the lithium-rich manganese-based material in the positive electrode active material is 20%:

based on example 1, the addition amounts of the single crystal ternary material in the step 2 and the lithium-rich manganese-based material in the step 3 were adjusted to 3840g and 960 g. The slurry was also made into an electrode, which was assembled with a conventional negative electrode material with graphite as an active material to test electrical properties.

As shown in fig. 1 and 2, the cycle performance of battery a at normal temperature and high temperature 1C/1C is superior to that of batteries B and C, and it can be seen that the cycle performance of battery 1C/1C using the positive active material formed by compounding the single crystal ternary material and the lithium-rich manganese-based material is superior to that of a battery using the single crystal ternary material and the lithium-rich manganese-based material as the positive active material. As shown in FIG. 3, the normal temperature 1C/1C cycle performance of battery A is better than that of battery D, and it can be seen that the higher the mass percentage of the lithium-rich manganese-based material in the positive active material is, the better the 1C/1C cycle performance is.

Example 3

1) Checking the air tightness of the batching pot, adding 800g of carbon nanotube slurry and 69g of polyvinylidene fluoride glue solution after ensuring no abnormal air tightness, adding 500g of acetone, and stirring for 90 min;

2) opening the batching pot, adding 16g of conductive carbon black, 16g of graphite and 2400g of nickel 55 ternary, and stirring for 90 min;

3) the batch pot was opened and 2400g of Li-rich manganese-based material Li were added_1.15Ni_0.35Mn_0.5O₂Stirring for 60min to obtain a slurry stock solution;

4) and finally, adding N-methyl pyrrolidone to adjust the viscosity of the slurry stock solution to about 14000mpa.s, and continuously stirring for 180min to obtain the anode slurry.

Example 4

1) Checking the air tightness of the batching pot, adding 800g of carbon nanotube slurry and 47g of polyvinylidene fluoride glue solution after ensuring no abnormal air tightness, adding 500g of cyclohexanone, and stirring for 40 min;

2) opening the batching pot, adding 24g of conductive carbon black, 24g of graphite and 2400g of nickel 55 ternary, and stirring for 40 min;

3) the batch pot was opened and 2400g of Li-rich manganese-based material Li were added_1.15Ni_0.35Mn_0.5O₂Stirring for 40min to obtain slurry stock solution;

4) and finally, adding N-methyl pyrrolidone to adjust the viscosity of the slurry stock solution to be about 16000mpa.s, and continuously stirring for 80min to obtain the anode slurry.

Example 5

The content of the lithium-rich manganese-based material in the positive electrode active material is 35%:

based on example 1, the addition amount of the single crystal ternary material in the step 2 and the addition amount of the lithium-rich manganese-based material in the step 3 were adjusted to 3120g and 1680 g.

Example 6

On the basis of example 1, the solvent of step 1 was replaced by isopropanol.

Examples 7 to 10

On the basis of example 1, the single crystal ternary material is replaced by 523 ternary, 622 ternary, nickel 65 ternary and 811 ternary respectively.

Examples 11 to 12

On the basis of example 1, the lithium-rich manganese-based materials were respectively replaced with 0.25Li₂MnO₃·0.75LiMnO₂And 0.5Li₂MnO₃·0.5Li[Mn_1/3Ni_1/3Co_1/3]O₂。

Example 13

On the basis of example 1, the polyvinylidene fluoride glue was replaced by carboxymethyl cellulose.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.