CN111965090B - Measurement device and characterization method for swelling characteristics of high polymer for lithium battery - Google Patents
Measurement device and characterization method for swelling characteristics of high polymer for lithium battery Download PDFInfo
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- 230000008961 swelling Effects 0.000 title claims abstract description 136
- 229920000642 polymer Polymers 0.000 title claims abstract description 80
- 238000012512 characterization method Methods 0.000 title claims abstract description 23
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 16
- 238000005259 measurement Methods 0.000 title claims description 14
- 239000002904 solvent Substances 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 29
- 229920001971 elastomer Polymers 0.000 claims abstract description 25
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 20
- 239000010959 steel Substances 0.000 claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 16
- 230000002522 swelling effect Effects 0.000 claims abstract description 16
- 239000000843 powder Substances 0.000 claims description 11
- 230000008859 change Effects 0.000 claims description 4
- 238000005303 weighing Methods 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 3
- 230000003746 surface roughness Effects 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 16
- 238000012545 processing Methods 0.000 abstract description 14
- 239000002245 particle Substances 0.000 abstract description 11
- 229920002521 macromolecule Polymers 0.000 abstract description 4
- 238000012544 monitoring process Methods 0.000 abstract description 4
- 150000003384 small molecules Chemical class 0.000 abstract description 3
- 206010042674 Swelling Diseases 0.000 description 103
- 239000000463 material Substances 0.000 description 12
- 239000002033 PVDF binder Substances 0.000 description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 238000004090 dissolution Methods 0.000 description 5
- 239000003292 glue Substances 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 208000011231 Crohn disease Diseases 0.000 description 2
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 2
- 229920002943 EPDM rubber Polymers 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000013139 quantization Methods 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000000861 blow drying Methods 0.000 description 1
- 229920006184 cellulose methylcellulose Polymers 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000011530 conductive current collector Substances 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 description 1
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004482 other powder Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 229920001285 xanthan gum Polymers 0.000 description 1
- 229940082509 xanthan gum Drugs 0.000 description 1
- 235000010493 xanthan gum Nutrition 0.000 description 1
- 239000000230 xanthan gum Substances 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/0806—Details, e.g. sample holders, mounting samples for testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
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- Treatments Of Macromolecular Shaped Articles (AREA)
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Abstract
The invention provides a measuring device for swelling characteristics of a high polymer for a lithium battery, which comprises a swelling chamber for placing the high polymer and a solvent, wherein a steel mesh is movably placed in the swelling chamber, a guide rod is fixed at the top of the steel mesh, a rubber plug is plugged at a liquid inlet of the swelling chamber, an opening for allowing the guide rod to pass through is formed in the rubber plug, a laser range finder is arranged above the swelling chamber, a through hole for allowing laser of the laser range finder to pass through is formed in the rubber plug, and a method for representing the swelling characteristics of the high polymer is further provided, and the measuring device comprises the following steps: the mass of the polymer to be added and the characterization of the swelling properties of the polymer are calculated. Through monitoring the volume from time to time, the data acquisition processing system converts the volume into a swelling characterization value, a characteristic curve of time and the swelling characterization value is formed, and the characteristic curve characterizes the process that solvent small molecules enter high polymer macromolecule particles to expand the particles, open molecular chains and stretch to reach a thermodynamically stable binary homogeneous system.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a device for measuring swelling characteristics of a polymer for a lithium battery and a characterization method.
Background
With the wide application of lithium battery and nickel battery in the new energy field, various large battery manufacturers compete strongly in new technology, high quality, low cost, rapid manufacturing and the like, and particularly, a great deal of researches are made in the aspects of rapid evaluation of physical properties in the initial stage of new material development, formulation of reasonable and effective production process parameters after volume production and the like.
The high molecular polymers such as CMC, PVDF, HPMC, PTFE, xanthan gum and the like are binders commonly used for lithium batteries and nickel batteries, play a key role in adhering active particles, conductive agents and current collectors in batteries and keeping the structural characteristics of electrodes. When in use, the polymer powder is fully dissolved in a solvent to prepare a glue solution. Mixing the glue solution with active material, conductive agent and other powder to obtain slurry, and adding into the battery. The swelling and dissolution characteristics of the high polymer in the solvent are the main influencing factors of the glue solution manufacturing process.
The polymer forms homogeneous phase in the solvent and is divided into two processes of swelling and dissolution, wherein swelling is the process that solvent small molecules enter the pores of polymer particles, the polymer particles expand, macromolecular chains are stretched and opened. Dissolution is a process in which the opened macromolecules and solvent small molecules form a binary homogeneous phase. In the development process of the new material, the mastering of the swelling characteristic is necessary for development and application, and plays a vital role in the production and manufacturing link of the new material.
At present, the swelling and dissolution characteristics of the polymer for the lithium ion battery in the industry are easy to evaluate, unified techniques and standards are not formed, quantized values cannot be given, and quantized values of the swelling process of the polymer material cannot be provided.
Disclosure of Invention
In view of the above, the invention aims to provide a measurement device and a characterization method for swelling characteristics of a polymer for a lithium battery, so that a data acquisition processing system converts the volume into a swelling characterization value through monitoring the volume in real time to form a characteristic curve of time and the swelling characterization value, and characterizes a process that solvent micromolecules enter macromolecule particles of the polymer to expand the particles, open molecular chains and stretch the particles to achieve a thermodynamically stable binary homogeneous system.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
the utility model provides a measuring device of polymer swelling characteristic for lithium cell, includes the swelling room that is used for placing polymer and solvent, has placed the steel mesh in the swelling room mobilizable, and the top of steel mesh is fixed with the guide arm, and the inlet department of swelling room has the plug, opens on the plug and holds the trompil that the guide arm passed, and the top of swelling room is equipped with laser rangefinder, still opens on the plug and holds the through-hole that laser of laser rangefinder passed.
Further, the device also comprises a fixing frame, wherein the top of the fixing frame is provided with a groove for placing the swelling chamber downwards.
Further, the top of the ejector rod is hung at the top of the rubber plug.
Further, the system also comprises a data acquisition and processing system, wherein the laser range finder is connected with the data acquisition and processing system through an electric signal.
A method of characterizing swelling properties of a polymer comprising the steps of:
(1) Calculating the mass of the polymer to be added:
(A) Measuring a solvent for dissolving the high polymer, and standing under the negative pressure condition to remove bubbles;
further, the negative pressure condition is that the vacuum degree is less than or equal to-90 KPa.
(B) The distance from the laser distance meter to the bottom of the swelling chamber is measured by the laser distance meter and is recorded as H 0 ；
Further, the operating step of thermostatting is performed in a thermostatted bath.
Further, the temperature fluctuation of the constant temperature tank is +/-0.05 ℃, the digital display resolution is 0.01 ℃, the temperature control range is 0-90 ℃, the volume is preferably 10L, and the heating medium is preferably water.
(D) After the constant temperature is finished, the distance between the top of the liquid level of the solvent in the step (3) and the laser distance meter is measured by the laser distance meter and is recorded as H 1 ；
(E) The total volume V of the solvent in the swelling chamber was calculated according to the following formula 0 ：
V 0 ＝(H 1 -H 0 )×(Φ/2) 2 X 3.14, wherein Φ is the inner diameter of the swelling chamber;
(F) The mass W of the polymer to be added into the swelling chamber is calculated according to the following formula 0 ；
W 0 ＝V 0 /(1- α) ×α, where α is the mass percent of polymer in the post-swelling solution;
when calculated, the density of the common solvent is 1g/cm 3 And (5) calculating.
(2) Characterization of the swelling Properties of the Polymer:
(A) The weighing mass is W 1 Wherein W is 1 ＝W 0 0.0005g, placing the weighed polymer into a swelling chamber;
furthermore, when an organic solvent is used as a solvent of the polymer, for example, NMP and cyclohexane are used for dissolving PVDF, the rubber plug is mainly corrosion-resistant, and the material of the rubber plug is preferably ethylene propylene diene monomer; when pure water is used as the polymer solvent, for example, when pure water is used to measure the swelling characteristics of CMC, a rubber plug made of a common rubber material is sufficient.
(C) Real-time measurement of swelling time T and step by laser range finderDistance H from the top of the liquid surface in step (B) to the laser rangefinder in step (2) 2 And the volume of the solution during swelling was calculated according to the following formula: v (V) 2 ＝(H 2 -H 0 )×(Φ/2) 2 ×3.14；
(D) Stopping the measurement when the swelling behaviour value η does not change or changes very little with the swelling time T, wherein the swelling behaviour value η = V 2 /W 1 The method comprises the steps of carrying out a first treatment on the surface of the And drawing a relation curve of the swelling time T and the swelling characterization value eta to obtain a curve for characterizing the swelling characteristic of the polymer.
Further, the H 2 、H 1 、H 0 The units of phi are all mm, and the V 2 、V 1 Is in mL units, the W 1 、W 0 Is in g, and eta is in mL/g.
Further, the constant temperature in step (C) in step (1) is preferably 20 to 25 ℃.
Further, the inner diameter value of the swelling chamber is less than or equal to 5mm and less than or equal to 15mm, the inner diameter precision of the swelling chamber is not lower than +/-0.01 mm, the cylindricity of the swelling chamber is not higher than 3um, the surface roughness of the swelling chamber is not lower than 0.8, and the height value of the swelling chamber is less than or equal to 100mm and less than or equal to 300mm.
Further, the diameter of the guide rod is less than or equal to 0.5mm, and the steel mesh is provided with meshes with the aperture of less than or equal to 20 um.
Further, the steel mesh is preferably formed of sus304.
Further, the mass of the polymer was weighed using a balance with a balance accuracy of 0.0001g.
Further, the measurement precision of the laser range finder is 0.01mm, the measuring range is selected according to the height of the swelling chamber, and the brand of the laser range finder is Crohn's disease.
Furthermore, the data acquisition processing system can automatically read and record the data output by the laser range finder, the data acquisition time, frequency and interval can be set through a system window, and the acquisition frequency is more than or equal to 1/5 s; the system has the function of forming a real-time monitoring curve, and is convenient for operators to check; has the function of deriving the original data.
Compared with the prior art, the device for measuring the swelling property of the polymer for the lithium battery and the characterization method have the following advantages:
(1) According to the measuring device and the characterization method for the swelling characteristics of the high polymer for the lithium battery, the volume is monitored constantly, the data acquisition processing system converts the volume into the swelling characterization value to form the characteristic curve of time and the swelling characterization value, and the characteristic curve characterizes the process that solvent micromolecules enter high polymer macromolecule particles to enable the particles to expand, molecular chains to open and stretch to reach a thermodynamically stable binary homogeneous system.
(2) According to the measuring device and the characterization method for the swelling characteristics of the high polymer for the lithium battery, provided by the invention, the swelling characteristics of the material can be mastered quickly through the swelling quantization curve, the new material can be applied to the establishment of technological parameters in a production and manufacturing link quickly, and when the new material is developed, the swelling and dissolution characteristics of the high polymer of the new material can be mastered quickly through the comparison of the novel material and the existing model quantization characteristic curve, so that reasonable production technological parameters can be established quickly.
(3) According to the measuring device and the characterization method for the swelling characteristics of the high polymer for the lithium battery, provided by the invention, the swelling process of the high polymer is quantified through the characteristic curves of time and swelling characterization values, and the measuring device for the swelling characteristics of the high polymer is provided, and the swelling process is quantified through the volume change in the swelling process and the quantified curve is given.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute an undue limitation on the invention. In the drawings:
FIG. 1 is a schematic view of a measuring device according to an inventive embodiment of the present invention;
FIG. 2 is an enlarged view of part of A of FIG. 1 of the present invention;
FIG. 3 is a schematic view of SEM morphology of sample A according to an inventive example;
FIG. 4 is a SEM schematic of sample B according to an inventive example;
FIG. 5 is a schematic representation of the swelling curve of PVDF according to the inventive examples of the present invention.
Reference numerals illustrate:
1-a high polymer powder layer; 2-a swelling chamber; 3-a constant temperature tank; 4-steel mesh; 5-a guide rod; 6, a rubber plug; 7-fixing frames; 8-a laser range finder; 9-a data acquisition and processing system.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In the description of the invention, it should be understood that the terms "center," "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships that are based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the invention and simplify the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be configured and operate in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The term "fixedly attached" may be used in a conventional manner of attachment such as plugging, welding, threading, bolting, etc., unless explicitly stated and limited otherwise. The specific meaning of the above terms in the creation of the present invention can be understood by those of ordinary skill in the art in a specific case.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
The utility model provides a measuring device of polymer swelling characteristic for lithium cell, includes the swelling room 2 that is used for placing polymer and solvent, has placed steel mesh 4 in the swelling room 2 mobilizable, and the top of steel mesh 4 is fixed with guide arm 5, and the inlet department of swelling room 2 has plugged plug 6, opens on plug 6 and has the trompil that holds guide arm 5 and pass, and the top of swelling room 2 is equipped with laser range finder 8, still opens the through-hole that holds laser range finder 8's laser to pass on the plug 6.
The swelling device also comprises a fixing frame 7, wherein the top of the fixing frame 7 is provided with a groove for placing the swelling chamber 2 downwards.
Care was taken during the experiment to maintain the level of the holder 7 and swelling chamber 2.
The top of the ejector rod is hung at the top of the rubber plug 6.
The laser range finder device also comprises a data acquisition and processing system 9, wherein the laser range finder 8 is connected with the data acquisition and processing system 9 through an electric signal.
A method of characterizing swelling properties of a polymer comprising the steps of:
(1) Calculating the mass of the polymer to be added:
(A) Measuring a solvent for dissolving the high polymer, and standing under the negative pressure condition to remove bubbles;
the negative pressure condition is that the vacuum degree is less than or equal to-90 KPa.
(B) Measuring the distance from the laser distance meter 8 to the bottom of the swelling chamber 2 by using the laser distance meter 8, and recording as H0;
when the size of the swelling chamber 2 and the position of the laser range finder 8 are changed, the H0 value needs to be collected again.
Putting the solvent after the bubble removal in the step (1) into a swelling chamber 2, and keeping constant temperature for a certain time;
the operating step of the constant temperature is carried out in a constant temperature bath 3.
The temperature fluctuation of the constant temperature tank 3 is +/-0.05 ℃, the digital display resolution is 0.01 ℃, the temperature control range is 0-90 ℃, the volume is preferably 10L, and the heating medium is preferably water.
(D) After the constant temperature is finished, the distance from the top of the liquid level of the solvent in the step (3) to the laser distance meter 8 is measured by the laser distance meter 8 and is recorded as H 1 ；
(E) The total volume V of the solvent in the swelling chamber 2 was calculated according to the following formula 0 ：
V 0 ＝(H 1 -H 0 )×(Φ/2) 2 X 3.14, wherein Φ is the inner diameter of the swelling chamber 2;
(F) The mass W of the polymer to be added into the swelling chamber 2 is calculated according to the following formula 0 ；
W 0 ＝V 0 /(1- α) ×α, where α is the mass percent of polymer in the post-swelling solution;
(2) Characterization of the swelling Properties of the Polymer:
(A) The weighing mass is W 1 Wherein W is 1 ＝W 0 0.0005g, placing the weighed polymer into the swelling chamber 2;
the polymer is required to be weighed under the environment that the normal temperature and the humidity are less than or equal to 10 percent after being dried, and is not allowed to be exposed to the high-humidity environment before being added into the swelling chamber 2, so that the stretching and opening of the polymer chains in the solvent of the polymer are prevented from being influenced by the water absorption of the polymer.
The high polymer powder is pressed and immersed into the solvent by a steel mesh 4, a guide rod 5 at the top of the steel mesh 4 is hung at an opening of a rubber plug 6, and then the rubber plug 6 is plugged at a liquid inlet of the swelling chamber 2;
the smaller and better the diameter of the opening of the rubber plug 6 is on the premise of meeting the operation requirement, and the error caused by volatilization of NMP in the swelling process is reduced.
When an organic solvent is used as a solvent of the high polymer, for example, NMP and cyclohexane are used for dissolving PVDF, the rubber plug 6 is mainly corrosion-resistant, and the material of the rubber plug 6 is preferably ethylene propylene diene monomer; when pure water is used as the polymer solvent, for example, when the CMC swelling property is measured with pure water, the rubber plug 6 made of a common rubber material may be used.
(C) Laser range finder 8 real-timeMeasuring the swelling time T and the distance H2 from the top of the liquid level to the laser range finder 8 in the step (B) in the step (2), and calculating the volume of the solution in the swelling process according to the following formula: v (V) 2 ＝(H 2 -H 0 )×(Φ/2) 2 ×3.14；
(D) Stopping the measurement when the swelling behaviour value η does not change or changes very little with the swelling time T, wherein the swelling behaviour value η = V 2 /W 1 The method comprises the steps of carrying out a first treatment on the surface of the And drawing a relation curve of the swelling time T and the swelling characterization value eta to obtain a curve for characterizing the swelling characteristic of the polymer.
The H is 2 、H 1 、H 0 The units of phi are all mm, and the V 2 The units of V1 are mL, and the W 1 、W 0 Is in g, and eta is in mL/g.
The constant temperature in step (C) in step (1) is preferably 20 to 25 ℃.
The inner diameter of the swelling chamber 2 is equal to or less than 5mm and equal to or less than 15mm, the precision of the swelling chamber 2 is not lower than +/-0.01 mm, the cylindricity of the swelling chamber 2 is not higher than 3um, the surface roughness of the swelling chamber 2 is not lower than 0.8, and the height of the swelling chamber 2 is equal to or less than 100mm and equal to or less than 300mm.
The smaller the inner diameter of the swelling chamber 2, the higher the liquid level will make the measurement more accurate, but the inner diameter of the swelling chamber 2 cannot be too small, otherwise the inner diameter is too small to make the rubber plug 6 smaller, and the aperture of the opening hole on the rubber plug 6 will be too small, so that the laser alignment of the laser range finder 8 is not accurate enough, the accuracy of the measurement data is affected, and the meniscus may be formed at the top of the liquid level if the inner diameter is too small, resulting in inaccurate measurement.
During the swelling process, the total volume of the solution gradually decreases as the polymer is continuously swelled in the solvent.
The swelling chamber 2 is a tool for precisely measuring the volume, is properly stored, avoids collision, uses high-pressure water for flushing and compressed air for blow-drying during cleaning, and avoids scratch caused by hard objects such as steel wire balls.
The diameter of the guide rod 5 is less than or equal to 0.5mm, and the steel mesh 4 is provided with meshes with the aperture of less than or equal to 20 um.
The steel mesh 4 is preferably formed of sus304.
The mass of the polymer was weighed using a balance with a balance accuracy of 0.0001g.
The weighed PVDF is slowly placed in the swelling chamber 2, taking care to avoid sticking of the powder to the inner walls of the swelling chamber 2.
The measurement accuracy of the laser range finder 8 is 0.01mm, the measuring range is selected according to the height of the swelling chamber 2, and the brand of the laser range finder 8 is Crohn's disease.
The data acquisition processing system 9 can automatically read and record the data output by the laser range finder 8, the data acquisition time, frequency and interval can be set through a system window, and the acquisition frequency is more than or equal to 1/5 s; the system has the function of forming a real-time monitoring curve, and is convenient for operators to check; has the function of deriving the original data.
The addition amount of the solvent is slightly higher than the amount of the solvent required by swelling and dissolving the high-molecular polymer, so that the swelling speed of the high-molecular polymer is reduced due to the fact that the solvent amount is too small.
Examples
Preparation:
one beaker (200 ml), one pipette (10 ml), one ear-washing ball and a vacuum cavity are connected with a vacuum pump; leveling the fixing frame; the inner diameter of the swelling chamber is 10mm, and the height is 200mm; the physical properties of two PVDF samples are shown in Table 1 below:
table 1 parameter lists of two PVDF samples
The specific operation process comprises the following steps:
measurement of sample a:
(1) High polymer NMP debubbling: taking about 100ml of NMP by a beaker, placing the NMP in a negative pressure cavity to remove bubbles, wherein the vacuum degree is less than or equal to-90 KPa, and the bubble removing time is 30min;
(2) NMP removal: 10ml of NMP solution was pipetted into the swelling chamber 2, the thermostatic bath 3 was opened, the constant temperature was set at 20℃and the temperature was maintained for 1 hour. Starting a laser range finder 8, starting a data acquisition and processing system 9, measuring and calculating to obtain the volume V of NMP in the swelling chamber 2 0 ＝10.0602ml；
(3) PVDF weighing: drying PVDF powder at 80 ℃ and vacuum degree of less than or equal to-90 KPa for 12 hours; according to V 0 = 10.0602ml, the swelling was calculated according to the following formula to give a mass percentage of PVDF of 6%: w (W) 0 ＝V 0 /(1-6％)×6％＝10.0602/(1-6％)×6％＝0.6421g；
Weigh W 1 = 0.6425g, will W 1 The actual value powder is input into the data acquisition and processing system 9.
(4) Slowly feeding the weighed PVDF powder into the swelling chamber 2, slowly pressing and immersing the powder floating on the liquid surface below the liquid surface by using a steel mesh 4, and pressing and immersing the powder to the middle position of the liquid surface of the NMP solvent visually, wherein a rubber plug 6 is pressed and covered on a liquid inlet of the swelling chamber 2;
(5) The data acquisition and processing system 9 measures and calculates V 1 And V is combined with 1 Converting into a swelling characterization value eta;
(6) Setting an execution mode on the data acquisition processing system 9:
the first step: data acquisition interval 10s, execution time 12 hours;
and a second step of: data acquisition interval 60s, execution time 12 hours;
and a third step of: the data acquisition interval is 120s, the execution time is 24 hours, and the process is finished;
measurement of sample B:
(7) Repeating the steps (1) to (6), and testing the sample B;
(8) Exporting data and sorting;
(9) Data analysis:
the two samples are two products of the same manufacturer and different models, and can be obtained from characteristic curve comparison:
sample A reaches a binary homogeneous phase time of about 30 hours, and sample B takes about 46 hours, so that the swelling property of sample A is better than that of sample B;
at the initial stage of swelling, the NMP solvent has better capacity to enter the powder particles of the sample A than the sample B;
in the later period of swelling, the polymer of sample B is not as stretched and opened as sample A;
assuming that the sample A is a currently used product, according to the glue production parameters of the sample A, the glue solution with good quality can be obtained by presuming that the sample B needs to be slightly improved on the basis of the sample A in the aspects of stirring time, temperature, rotating speed and the like.
The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A method for characterizing swelling properties of a polymer by a measuring device for swelling properties of a polymer for a lithium battery, characterized by: the device for measuring the swelling characteristics of the high polymer for the lithium battery comprises a swelling chamber (2) for placing the high polymer and a solvent, wherein a steel mesh (4) is movably placed in the swelling chamber (2), a guide rod (5) is fixed at the top of the steel mesh (4), a rubber plug (6) is plugged at a liquid inlet of the swelling chamber (2), an opening for allowing the guide rod (5) to pass through is formed in the rubber plug (6), a laser range finder (8) is arranged above the swelling chamber (2), and a through hole for allowing laser of the laser range finder (8) to pass through is formed in the rubber plug (6);
a method for characterizing swelling properties of a polymer using the device described above, comprising the steps of:
(1) Calculating the mass of the polymer to be added:
(A) Measuring a solvent for dissolving the high polymer, and standing under the negative pressure condition to remove bubbles;
(B) The distance from the laser distance meter (8) to the bottom of the swelling chamber (2) is measured by the laser distance meter (8), and is marked as H 0 ；
(C) Putting the solvent after the bubble removal in the step (A) in the step (1) into a swelling chamber (2), and keeping the temperature for a certain time;
(D) After the constant temperature is finished, the distance from the top of the liquid level of the solvent in the step (C) to the laser distance meter (8) in the step (1) is measured by the laser distance meter (8), and is recorded as H 1 ；
(E) The total volume V of the solvent in the swelling chamber (2) was calculated according to the following formula 0 ：
V 0 ＝(H 1 -H 0 )×(Φ/2) 2 X 3.14, wherein Φ is the inner diameter of the swelling chamber (2);
(F) The mass W of the polymer to be added into the swelling chamber (2) is calculated according to the following formula 0 ；
W 0 ＝V 0 /(1- α) ×α, where α is the mass percent of polymer in the post-swelling solution;
(2) Characterization of the swelling Properties of the Polymer:
(A) The weighing mass is W 1 Wherein W is 1 ＝W 0 0.0005g, placing the weighed polymer into a swelling chamber (2);
(B) Pressing and immersing high polymer powder into a solvent by using a steel mesh (4), hanging a guide rod (5) at the top of the steel mesh (4) at an opening of a rubber plug (6), and then plugging the rubber plug (6) at a liquid inlet of a swelling chamber (2);
(C) The laser distance meter (8) measures the swelling time T in real time and the distance H from the top of the liquid level to the laser distance meter (8) in the step (B) in the step (2) 2 And the volume of the solution during swelling was calculated according to the following formula: v (V) 2 ＝(H 2 -H 0 )×(Φ/2) 2 ×3.14；
(D) Stopping the measurement when the swelling behaviour value η does not change or changes very little with the swelling time T, wherein the swelling behaviour value η = V 2 /W 1 The method comprises the steps of carrying out a first treatment on the surface of the And drawing a relation curve of the swelling time T and the swelling characterization value eta to obtain a curve for characterizing the swelling characteristic of the polymer.
2. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the measuring device also comprises a fixing frame (7), and a groove for placing the swelling chamber (2) is formed in the top of the fixing frame (7) downwards.
3. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the constant temperature of the step (C) in the step (1) is 20-25 ℃.
4. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the inner diameter value of the swelling chamber (2) is less than or equal to 5mm and less than or equal to 15mm, the inner diameter precision of the swelling chamber (2) is not lower than +/-0.01 mm, the cylindricity of the swelling chamber (2) is not higher than 3um, the surface roughness of the swelling chamber (2) is not lower than 0.8, and the height value of the swelling chamber (2) is less than or equal to 100mm and less than or equal to 300mm.
5. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the diameter of the guide rod (5) is less than or equal to 0.5mm, and the steel mesh (4) is provided with meshes with the aperture of less than or equal to 20 mu m.
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