CN111443243A - Detection method for conductivity of lithium ion battery binder - Google Patents

Abstract

A method for detecting the conductivity of a lithium ion battery binder provided by the present invention obtains a solid binder to be tested, and manufactures a battery structure using the binder to be tested; EIS test is performed on the battery structure, and according to the test As a result, the conductivity of the binder to be tested is calculated. The method for detecting the conductivity of the lithium ion battery binder provided by the present invention provides very important performance parameters for selecting a suitable binder, and the method has accurate test results, simple and rapid method and easy operation.

Description

A kind of detection method of lithium ion battery binder conductivity

technical field

The invention relates to the technical field of lithium batteries, in particular to a method for detecting the conductivity of a lithium ion battery binder.

Background technique

Due to its high energy density, lithium-ion batteries have played an increasingly important role in new energy. The capacity of lithium-ion batteries is determined by the active lithium ions of the positive electrode material and the ability of the negative electrode material to intercalate and remove lithium. The stability in various environments determines the performance of the battery, and even seriously affects the safety of the battery. In order to further improve the performance of lithium-ion batteries, researchers try to find new electrode materials, electrolytes and additives. However, the efficiency of lithium-ion batteries depends largely on the optimization of electrode preparation conditions. The most suitable binder for electrodes. In the electrode, the binder is a very important part of the positive and negative electrode materials of the lithium battery. It can tightly bond the active material, the conductive agent and the current collector in the electrode material, and enhance the active material, the conductive agent and the active material. The electronic contact between the material and the current collector can better stabilize the structure of the pole piece, and the binder also plays an important buffering role in the volume expansion/contraction of the positive and negative electrodes of the lithium-ion battery during charging and discharging. Its selection and use significantly affect the macroscopic electrochemical performance of the electrode, and its optimization is an important factor that must be considered in the fabrication of high-performance lithium-ion battery electrode sheets. Therefore, a suitable binder is one of the key points for the success of lithium-ion power batteries.

Choosing a suitable lithium-ion battery binder requires stable performance in the electrolyte, no swelling, no looseness, no powder removal, and small ohmic resistance. Therefore, a simple and accurate battery binder conductance is developed. The test method of the rate is crucial and provides very important performance parameters for the selection of a suitable binder.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background art, the present invention provides a method for detecting the conductivity of a lithium ion battery binder.

A method for detecting the conductivity of a lithium ion battery binder provided by the present invention obtains a solid binder to be tested, and manufactures a battery structure using the binder to be tested; EIS test is performed on the battery structure, according to the test As a result, the conductivity of the binder to be tested is calculated.

Preferably, the binder to be tested has a sheet-like structure.

Preferably, the method for obtaining the solid binder to be tested is as follows: coating the liquid binder on the surface of the copper foil for drying treatment, the drying temperature is 60-120°C, and the drying time is 4-12 hours, and then the binder is cut out. The film is used as the binder to be tested.

Preferably, the adhesive to be tested is a circular diaphragm with a diameter of 12-18mm and a thickness of L20-200um.

Preferably, the battery structure is composed of a battery negative electrode shell, a first stainless steel sheet, a copper foil, a binder to be tested, a separator, a second stainless steel sheet, a spring gasket and a battery positive electrode shell from bottom to top.

The method for detecting the conductivity of a lithium ion battery binder provided by the present invention provides very important performance parameters for selecting a suitable binder, and the method has accurate test results, simple and rapid method and easy operation.

Description of drawings

1 is a flowchart of a method for detecting the conductivity of a lithium-ion battery binder proposed by the present invention;

2 is a schematic diagram of a battery structure in a method for detecting the conductivity of a lithium-ion battery binder proposed by the present invention;

FIG. 3 is a line graph of the test data of the conductivity of the lithium-ion battery binder in Example 1. FIG.

Detailed ways

Referring to FIG. 1 , a method for detecting the conductivity of a lithium-ion battery binder proposed by the present invention obtains a solid binder to be tested, and manufactures a battery structure using the binder to be tested; EIS is performed on the battery structure. Test, calculate the conductivity of the binder to be tested according to the test results.

Specifically, the battery structure in this embodiment is composed of a battery negative electrode shell, a first stainless steel sheet, a copper foil, a binder to be tested, a separator, a second stainless steel sheet, a spring gasket and a battery positive electrode shell from bottom to top. The EIS test can be completed by placing the battery structure in the electrolyte, or adding the electrolyte in the closed space formed by the battery negative shell and the battery positive shell.

In a specific embodiment of the method, the EIS test frequency range can be selected to be 1-500KHz, the amplitude is 5mV, and the test temperature is room temperature. The test result of the test group is recorded as R ₁ , and the test result of the reference group is recorded as R ₀ . The electrical conductivity σ of the adhesive is calculated according to the formula ΔRct=R ₁ -R ₀ , σ=L/(ΔRct×A), where A is the area of the adhesive film, and L is the thickness of the adhesive film. Make and measure 3-5 button batteries according to the above steps, and take the average of the results as the test results of the electrical conductivity of the binder.

During specific implementation, in order to ensure the stability of the battery structure, the adhesive to be tested adopts a sheet-like structure.

Specifically, in this embodiment, the method for obtaining the solid binder to be tested is as follows: coating the liquid binder on the surface of the copper foil for drying treatment, the drying temperature is 60-120°C, and the drying time is 4-12h, The adhesive film is then cut out as the adhesive to be tested. Specifically, the adhesive to be tested is a circular diaphragm with a diameter of 12-18mm and a thickness of L20-200um.

This method is suitable for polyvinyl alcohol (PVA), polyacrylic acid (PAA) and its salts, polytetrafluoroethylene (PTFE), polyimide (PI), sodium carboxymethyl cellulose (CMC), polyolefins ( PP, PE and other copolymers), (PVDF/NMP) or other solvent systems, PVDF-based fluoropolymers, polyelectrolyte polymers, styrene-butadiene rubber (SBR), modified SBR rubber with good adhesion properties, Fluorinated rubber, lithium polyacrylate (Li-PAA) or other ionic polymer binders, polyurethane and other binders.

The present invention is demonstrated below with reference to two specific embodiments.

Example 1

The specific steps of the method for detecting the conductivity of the lithium-ion battery binder in this embodiment are as follows:

Step 1: Coat the modified SBR emulsion with good adhesive properties and the liquid adhesive with sample number AB on the surface of the copper foil, dry it at 60°C for 12h, and use a punching machine to make 5 adhesive films with a diameter of 12mm The film area A is 113.097mm ² , the thickness of the copper foil is 0.01mm measured with a micrometer, and the thickness L of the five adhesive films (the thickness of the adhesive minus the thickness of the copper foil) is 0.0774mm, 0.0754mm, 0.0714mm, 0.0718mm, 0.0762mm.

Step 2: Assemble the 2032 type button battery. The structure of the 2032 type button battery from bottom to top is the battery negative shell (with plastic sealing ring), stainless steel sheet, copper foil, adhesive diaphragm, diaphragm, Stainless steel sheet, spring gasket and battery positive shell, the electrolyte uses silicon carbon special electrolyte.

Step 3: Carry out EIS test on five 2032 type button batteries respectively. The EIS test frequency range is ₁ ~500KHz, the amplitude is 5mV, and the test temperature is room temperature. , 3.9746.

The average R ₀ of the EIS test results of five 2032 type coin cells can be calculated to be 2.8843. According to the formula ΔRct=R ₁ -R ₀ , σ=L/(ΔRct×A), the conductivity σ of the binder is calculated to be 6.15E-04, see Table 1 for details.

Table 1 Test results of lithium ion battery binder conductivity in Example 1.

Example 2

The specific steps of the method for detecting the conductivity of the lithium-ion battery binder in this embodiment are as follows:

Step 1: Coat polyacrylic acid (PAA) and liquid adhesive with sample number AP on the surface of copper foil, dry at 60°C for 12h, and use a punching machine to make 5 adhesive films with a diameter of 12mm. The area A was 113.097 mm ² , the thickness of the copper foil was measured as 0.01 mm using a micrometer, and the thickness of the adhesive film was L.

Step 2: Assemble 2032 type button battery, the order from bottom to top is battery negative shell (with plastic sealing ring), stainless steel sheet, copper foil, adhesive diaphragm, diaphragm, stainless steel sheet, spring gasket, The positive electrode shell of the battery, the electrolyte uses silicon carbon special electrolyte, and 5 binder diaphragms are assembled into 5 2032 type button batteries.

Step 3: Carry out EIS test on the assembled battery. The EIS test frequency range is 1-500KHz, the amplitude is 5mV, and the test temperature is room temperature. The average R ₀ of the EIS test results of the 5 batteries is 2.8843. The electrical conductivity of the binder is calculated according to the formula ΔRct=R ₁ −R ₀ , σ=L/(ΔRct×A).

The above descriptions are only the preferred specific embodiments involved in the present invention, but the protection scope of the present invention is not limited thereto. Equivalent replacement or modification of the technical solution and its inventive concept shall be included within the protection scope of the present invention.

Claims (5)

1. a detection method of lithium ion battery binder conductivity, is characterized in that, obtain solid state binder to be measured, and make the battery structure that adopts described binder to be measured; EIS test is carried out to battery structure, Calculate the conductivity of the binder to be tested based on the test results. 2 . The method for detecting the conductivity of a lithium ion battery binder according to claim 1 , wherein the binder to be tested has a sheet-like structure. 3 . 3. the detection method of lithium ion battery binder conductivity as claimed in claim 1, is characterized in that, the method that obtains solid state binder to be tested is: the binder of liquid is coated on copper foil surface drying Treatment, drying temperature is 60 ~ 120 ℃, drying time is 4 ~ 12h, and then the adhesive film is cut out as the adhesive to be tested. 4 . The method for detecting the conductivity of a lithium ion battery binder according to claim 3 , wherein the binder to be tested is a circular diaphragm with a diameter of 12-18 mm and a thickness of L20-200 um. 5 . 5. the detection method of lithium ion battery binder conductivity as claimed in claim 1 is characterized in that, the battery structure consists of the battery negative shell, the first stainless steel sheet, copper foil, the binder to be tested from bottom to top , diaphragm, second stainless steel sheet, spring gasket and battery positive shell.

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