阅读说明：本技术 一种极片电阻率测试方法 (Pole piece resistivity testing method ) 是由 李掌权 桂亚林 杨国强 夏小勇 于 2020-12-10 设计创作，主要内容包括：本发明属于锂离子电池极片领域,尤其涉及一种极片电阻率测试方法,包括以下步骤：S1、将涂覆浆料后的极片固定在绝缘板上,该极片包括涂料层和集流体,将极片上的集流体分离,从而得到待测涂料层；S2、将待测涂料层连接于电化学工作站上进行电阻率测试；S3、计算待测涂料层表观电阻率；与现有技术相比,降低测量极片电阻率的误差。(The invention belongs to the field of lithium ion battery pole pieces, and particularly relates to a pole piece resistivity testing method, which comprises the following steps: s1, fixing the pole piece coated with the slurry on an insulating plate, wherein the pole piece comprises a coating layer and a current collector, and separating the current collector on the pole piece to obtain the coating layer to be tested; s2, connecting the coating layer to be tested on an electrochemical workstation for resistivity test; s3, calculating the apparent resistivity of the coating layer to be measured; compared with the prior art, the method reduces the error of measuring the resistivity of the pole piece.)

1. A pole piece resistivity test method is characterized by comprising the following steps:

s1, fixing the pole piece coated with the slurry on an insulating plate, wherein the pole piece comprises a coating layer and a current collector, and separating the current collector on the pole piece to obtain the coating layer to be tested;

s2, connecting the coating layer to be tested on an electrochemical workstation for resistivity test;

and S3, calculating the apparent resistivity of the coating layer to be measured.

2. The method of claim 1, wherein in step S1, the pole piece coated with the slurry is fixed on the insulating plate by double-sided tape.

3. The method for testing the resistivity of the pole piece according to claim 2, wherein the surface of the pole piece is rolled, so that the pole piece is folded by 180 degrees along the edge of the double-sided adhesive tape beyond the double-sided adhesive tape, and the current collector is peeled off from the pole piece along the 180-degree direction.

4. The method of claim 3, wherein in step S2, one end of the paint layer to be tested is electrically connected and clamped to one alligator clip, the other end of the paint layer to be tested is electrically connected and clamped to the other alligator clip, and the two alligator clips are respectively electrically connected to the electrochemical workstation.

5. The method for testing the resistivity of the pole piece according to claim 1, wherein the pole piece coated with the slurry is a positive pole piece

6. The method of claim 1, wherein the insulating plate is a glass plate.

7. The method for testing the resistivity of the pole piece according to claim 1, wherein the apparent resistivity of the pole piece is the comprehensive resistivity of the coating layer to be tested.

Technical Field

The invention belongs to the field of lithium ion battery pole pieces, and particularly relates to a pole piece resistivity testing method.

Background

In the process of charging and discharging of the lithium ion battery, lithium ions and electrons are transmitted in a battery pole piece, wherein the lithium ions are transmitted through electrolyte filled in electrode pores, and the electrons are mainly transmitted to active substance particles or an electrolyte interface to participate in electrode reaction through a three-dimensional network formed by solid particles, particularly conductive agents; the conductivity of electrons has great influence on the performance of the battery, and mainly influences the rate performance of the battery; in the battery pole piece, the main factors influencing the resistivity comprise the condition of a bonding interface between the foil substrate and the coating layer, the distribution state of the conductive agent, the contact state among particles and the like; the uniformity of the microstructure in the pole piece can be judged through the resistivity of the battery pole piece, and the performance of the battery is predicted.

The prior art 1(CN 109358234 a) discloses a method for testing resistivity of a pole piece resistor, which is mainly based on the above patent, and measures RSD% of resistivity at different positions by optimizing resistor acquisition time and corresponding forward pressure parameters, but the publication introduces the concept of forward pressure parameters, and has a better test effect on resistivity at different positions of the same pole piece.

The disadvantages are as follows: the testing method in the prior art 1 has a relative reference significance only when the forward pressure parameter fluctuation is small, but for pole pieces with different compaction states and large conductivity difference, for example, the resistance of a coating layer of the pole piece and the resistance of a current collector of the pole piece have large difference, under the condition of large forward pressure parameter difference, the contact condition difference between an upper detection pressure head and a lower detection pressure head and the pole piece is large, and the measurement error is large.

Disclosure of Invention

The invention aims to provide a pole piece resistivity testing method, which can reduce the error of pole piece resistivity measurement.

In order to achieve the purpose, the invention adopts the following technical scheme:

a pole piece resistivity test method comprises the following steps:

s1, fixing the pole piece coated with the slurry on an insulating plate, wherein the pole piece comprises a coating layer and a current collector, and separating the current collector on the pole piece to obtain the coating layer to be tested;

s2, connecting the coating layer to be coated on an electrochemical workstation for resistivity test;

and S3, calculating the apparent resistivity of the pole piece to be measured.

Preferably, in step S1, the pole piece after being coated with the slurry is fixed on the insulating plate by double-sided tape.

Preferably, the surface of the pole piece is rolled, so that the pole piece exceeds the double-sided adhesive tape part and is turned over at 180 degrees along the edge of the double-sided adhesive tape in the width direction, and the current collector is stripped from the pole piece in the 180-degree direction.

Preferably, in step S2, the two ends of the pole piece to be tested are respectively fixed by using crocodile clips, and the crocodile clips are connected to the electrochemical workstation.

Preferably, the pole piece coated with the slurry is a positive pole piece

Preferably, the insulating plate is a glass plate.

Preferably, the apparent resistivity of the pole piece is the comprehensive resistivity of the pole piece coating layer.

The invention has at least the following beneficial effects: according to the invention, the resistivity of the coating layer is measured after the current collector is removed from the pole piece, so that the problem of large measurement error caused by the contact problem between the upper pressure head and the lower pressure head and the current collector of the pole piece when the resistivity in the thickness direction is measured in the prior art is solved.

Detailed Description

The invention provides a pole piece resistivity test method, which comprises the following steps:

s1, fixing the pole piece coated with the slurry on an insulating plate, wherein the pole piece comprises a coating layer and a current collector, and separating the current collector on the pole piece to obtain the coating layer to be tested;

s2, electrically connecting the coating layer to be coated on an electrochemical workstation for resistivity test;

and S3, calculating the apparent resistivity of the pole piece to be measured.

The pole pieces comprise a positive pole piece before rolling, a positive pole piece after rolling, a negative pole piece before rolling and a negative pole piece after rolling.

Wherein, the pole piece can be a positive pole piece or a negative pole piece.

The active material of the positive plate can be at least one of lithium manganate, lithium cobaltate, lithium nickel cobalt manganese, lithium iron phosphate and lithium-rich manganese, and the auxiliary material comprises a conductive agent and a binder.

The negative plate active material can be at least one of graphite, hard carbon, soft carbon and silicon-based materials, and the auxiliary materials comprise a conductive agent, a binder and a thickening agent.

Wherein, the insulating plate can be one of a glass plate, a plastic plate and a wood plate. The thickness of the insulating plate is not limited to 1-20 mm. The length of the insulating plate is 1-100 mm, preferably the length of the coating layer to be tested, and the width of the insulating plate is 1-100 mm, preferably slightly wider than the coating layer to be tested.

Wherein, in the step S1, the pole piece surface is through the running roller roll-in, makes the pole piece surpass the double faced adhesive tape part and turn over along the edge 180 of double faced adhesive tape width direction and turn over to make the mass collector peel off away from the pole piece along 180 orientations, preferred, running roller weight is: 1-20 KG, the rolling frequency is as follows: 1-100 times to ensure that the coating layer can be completely stripped from the current collector.

In step S2, fixing two ends of the paint layer to be tested by using crocodile clips, and connecting the crocodile clips to the electrochemical workstation. Preferably, the crocodile clip has the biting force of 5 kg-100 kg, so that the crocodile clip is in full contact with the material to be tested, and the phenomenon that the crocodile clip slides in the test process to cause the material to fall off to cause poor contact is prevented.

The following examples further illustrate the present invention in detail, but are not intended to limit the present invention.

Example 1:

1. the formula is as follows: conductive agent SP: and (3) oppositely facing a pole piece with 2:2:96 lithium cobaltate to a glass plate (100mm multiplied by 50mm) pasted with a high-strength double-sided adhesive (10mm multiplied by 50mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece, which exceeds the double-sided adhesive, along the width direction edge of the double-sided adhesive at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 2:

1. the formula is as follows: conductive agent SP: and (3) rolling a pole piece (the pole piece compaction density is 4.0g/cm3) with 2:2:96 of lithium cobaltate on a glass plate (100mm multiplied by 40mm) which is pasted with a high-strength double-sided adhesive (10mm multiplied by 40mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece which exceeds the double-sided adhesive along the edge of the double-sided adhesive in the width direction at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 30mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 3:

1. the formula is as follows: conductive agent SP: and (3) oppositely facing a pole piece with 2:2:96 lithium cobaltate to a glass plate (100mm multiplied by 30mm) pasted with a high-strength double-sided adhesive (10mm multiplied by 30mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece, which exceeds the double-sided adhesive, along the width direction edge of the double-sided adhesive at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 20mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 4:

1. the formula is as follows: conductive agent SP: and (3) oppositely facing a pole piece with 2:2:96 lithium cobaltate to a glass plate (100mm multiplied by 20mm) pasted with a high-strength double-sided adhesive (10mm multiplied by 20mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece, which exceeds the double-sided adhesive, along the width direction edge of the double-sided adhesive at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 10mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

The crocodile clip contact resistance only accounts for 1-3 ten-thousandth of the resistance according to the results of the comprehensive examples 1-4, so that the measured resistance can be basically regarded as the resistance of the pole piece.

The above examples 1 to 4 are repeated for a plurality of times to prepare samples, and the apparent charge rate ρ and the relative standard deviation RSD of the four examples are calculated respectively:

and S in the resistivity rho formula is the cross-sectional area of the coating layer to be measured, L is the length of the coating layer to be measured, and R is the resistance of the coating layer to be measured.

S in the relative standard deviation RSD formula is standard deviation, is the square root of the square sum of the deviation of each measured data divided by the number of data minus 1, and the square of the deviation of each single data is reflected prominently, so that the dispersion degree of the measured result data can be explained through the standard deviation;the corresponding average value is obtained by measuring multiple times to obtain an accurate result, and the arithmetic mean value of the measured data can represent the average level of the measured result

Example 5:

1. the formula is as follows: conductive agent SP: and (3) rolling a pole piece (the pole piece compaction density is 4.0g/cm3) with 2:1:96 of lithium cobaltate on a glass plate (100mm multiplied by 50mm) adhered with a high-strength double-sided adhesive (10mm multiplied by 50mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece, which exceeds the double-sided adhesive, along the edge of the double-sided adhesive in the width direction at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 6:

1. the formula is as follows: conductive agent SP: and (3) rolling 96 parts of lithium cobaltate (the compacted density of the pole piece is 4.0g/cm3) in a ratio of 2:3, rolling 50 times on the pole piece by using a 10kg roller on a glass plate (100mm multiplied by 50mm) adhered with a high-strength double-sided adhesive (10mm multiplied by 50mm), folding the part of the pole piece, which exceeds the double-sided adhesive, at 180 ℃ along the edge of the double-sided adhesive in the width direction, and separating a current collector from a coating layer to prepare the coating layer to be tested.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 7:

1. the formula is as follows: conductive agent SP: and (3) rolling a pole piece (the pole piece compaction density is 4.0g/cm3) with 2:4:96 of lithium cobaltate on a glass plate (100mm multiplied by 50mm) which is pasted with a high-strength double-sided adhesive (10mm multiplied by 50mm), rolling the pole piece for 50 times by using a 10kg roller, folding the part of the pole piece which exceeds the double-sided adhesive along the edge of the double-sided adhesive in the width direction at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 8:

1. the formula is as follows: conductive agent SP: and (3) rolling a pole piece (the compaction density of the pole piece is 4.0g/cm3) with 2:5:96 roll, pressing the pole piece for 50 times on a glass plate (100mm multiplied by 50mm) adhered with a high-strength double-sided adhesive (10mm multiplied by 50mm) by using a 10kg roller, folding the part of the pole piece, which exceeds the double-sided adhesive, along the width direction edge of the double-sided adhesive at 180 ℃, separating a current collector from the coating layer, and preparing the coating layer to be detected

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 9:

1. the formula is as follows: conductive agent SP: and (3) rolling a pole piece (the pole piece compaction density is 4.0g/cm3) with 2:6:96 roll, pressing the pole piece for 50 times by using a 10kg roller on the pole piece, wherein the pole piece is opposite to a glass plate (100mm multiplied by 50mm) adhered with a high-strength double-sided adhesive (10mm multiplied by 50mm), the part of the pole piece, which exceeds the double-sided adhesive, is folded at 180 ℃ along the edge of the double-sided adhesive in the width direction, and separating a current collector from a coating layer to prepare the coating layer to be tested.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

The above examples 1, 5, 6, 7, 8 and 9 were repeated a plurality of times to prepare samples, and the apparent charge rate ρ of each of the 6 examples was calculated.

Example 10:

1. the formula is as follows: conductive agent SP: and the ternary (111 type ternary) is a pole piece (the compaction density of the pole piece is 3.4g/cm3) after being rolled at a ratio of 2:2:96, the pole piece is directly opposite to a glass plate (100mm multiplied by 50mm) adhered with a high-strength double-sided adhesive (10mm multiplied by 50mm), a roller of 10kg is used for rolling the pole piece for 50 times, the part of the pole piece, which exceeds the double-sided adhesive, is folded at 180 ℃ along the edge of the double-sided adhesive in the width direction, and the current collector is separated from the coating layer material to prepare the coating layer to be.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 11:

1. the formula is as follows: conductive agent SP: and (3) rolling the lithium manganate into a pole piece (the compaction density of the pole piece is 3.0g/cm3) at a ratio of 2:2:96, and rolling the pole piece for 50 times by using a 10kg roller on the pole piece, wherein the pole piece is opposite to a glass plate (100mm X50 mm) adhered with a high-strength double-sided adhesive (10mm X50 mm), the part of the pole piece, which exceeds the double-sided adhesive, is folded at 180 ℃ along the edge in the width direction of the double-sided adhesive, and the current collector is separated from the coating layer to prepare the.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

Example 12:

1. the formula comprises thickening agent CMC, binder SBR: conductive agent SP: the artificial graphite is 2:2: 2: and (3) rolling the 96 rolled pole piece (the compaction density of the pole piece is 1.6g/cm3) on a glass plate (100mm multiplied by 50mm) which is just opposite to a high-strength double-sided adhesive (10mm multiplied by 50mm) for 50 times by using a 10kg roller, folding the part of the pole piece which exceeds the double-sided adhesive along the width direction edge of the double-sided adhesive at 180 ℃, and separating a current collector from a coating layer to prepare the coating layer to be tested.

2. And (3) clamping the alligator clips (the width of the clips is 5mm) with the gripping force of 10kg at the positions of 5mm at two ends of the length direction of the coating layer to be tested (the upper metal sheet and the lower metal sheet of the alligator clips are respectively contacted with the coating layer to be tested and the glass plate), wherein the length of the coating layer to be tested is 40mm, and the width of the coating layer to be tested is 10 mm.

3. And connecting the crocodile clip to an electrochemical workstation, and scanning the EIS at a fixed frequency of 1000HZ to obtain the resistance value.

The above examples 1, 10, 11 and 12 were repeated a plurality of times to prepare samples, and the apparent charge group rate ρ of each of 3 examples was calculated.

The results of the examples are shown in tables 1, 2 and 3

Table 1 coating layer length test results

Item	Example 1	Example 2	Example 3	Example 4
					ρ(ΩM)	0.4013	0.4008	0.4011	0.4014
RSD(％)	0.23	0.34	0.37	0.41

TABLE 2 Pole piece formulation test results

Item	Example 1	Example 5	Example 6	Example 7	Example 8	Example 9
							ρ(ΩM)	0.4013	0.482	0.3763	0.3537	0.3527	0.3512
RSD(％)	0.34	0.23	0.37	0.41	0.41	0.39

Table 3 material test results

Item	Example 1	Example 10	Example 11	Example 12
					ρ(ΩM)	0.4013	0.4208	0.6121	0.0331
RSD(％)	0.34	0.031	0.026	0.052

The pole piece is a mixture formed by mixing a plurality of materials, and the apparent resistivity of the coating layer is the resistivity of the mixture.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.