CN111965090A - Device for measuring swelling characteristic of high polymer for lithium battery and characterization method - Google Patents
Device for measuring swelling characteristic of high polymer for lithium battery and characterization method Download PDFInfo
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- 230000008961 swelling Effects 0.000 title claims abstract description 150
- 229920000642 polymer Polymers 0.000 title claims abstract description 74
- 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
- 238000012512 characterization method Methods 0.000 title claims description 7
- 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 22
- 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
- 239000000843 powder Substances 0.000 claims description 11
- 238000005259 measurement Methods 0.000 claims description 8
- 238000003825 pressing Methods 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 4
- 230000003746 surface roughness Effects 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 17
- 238000012545 processing Methods 0.000 abstract description 13
- 239000002245 particle Substances 0.000 abstract description 11
- 150000003384 small molecules Chemical class 0.000 abstract description 4
- 238000012544 monitoring process Methods 0.000 abstract description 3
- 206010042674 Swelling Diseases 0.000 description 107
- 239000000463 material Substances 0.000 description 13
- 239000002033 PVDF binder Substances 0.000 description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 239000003292 glue Substances 0.000 description 4
- 230000002522 swelling effect Effects 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 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
- 238000010586 diagram Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000000203 mixture Substances 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
- 238000002360 preparation method Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 238000005303 weighing 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
- 239000013543 active substance Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229920006184 cellulose methylcellulose Polymers 0.000 description 1
- 239000011530 conductive current collector Substances 0.000 description 1
- 238000007405 data analysis 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
- 238000000265 homogenisation 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
- 229920002521 macromolecule Polymers 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 238000002156 mixing Methods 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
- 238000013139 quantization 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
- 238000012360 testing method Methods 0.000 description 1
- 238000012876 topography 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
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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
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- 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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Abstract
The invention provides a device for measuring the swelling characteristic 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, and a through hole for allowing the laser of the laser range finder to pass through is also formed in the rubber plug. And calculating the quality of the high polymer to be added and the characteristic of the swelling characteristic of the high polymer. By monitoring the volume from time to time, the data acquisition and processing system converts the volume into a swelling characteristic value, a characteristic curve of time and the swelling characteristic value is formed, and the characteristic curve represents that small molecules of a solvent enter macromolecular particles of a high molecular polymer, so that the particles are expanded, molecular chains are opened, and the particles stretch to reach the process of 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 the swelling characteristic of a high polymer for a lithium battery and a characterization method.
Background
With the wide application of lithium batteries and nickel batteries in the field of new energy, various large battery manufacturers have intense competition in the aspects of new technology, high quality, low cost, rapid manufacturing and the like, and particularly make a great deal of research in the aspects of rapid evaluation of physical properties at the initial stage of new material development, formulation of reasonable and effective production process parameters after mass production and the like.
The high polymer such as CMC, PVDF, HPMC, PTFE, xanthan gum and the like is a common binder for lithium batteries and nickel batteries, plays a role in adhering living particles, conductive agents and current collectors in the batteries and plays a key role in maintaining the structural characteristics of the electrodes. When in use, the high polymer powder is fully dissolved in a solvent to prepare a glue solution. The glue solution is mixed with active substance, conductive agent and other powder to form slurry which is added into the battery. The swelling and dissolving characteristics of the high polymer in the solvent are main influencing factors of the glue solution preparation process.
The formation of the high polymer in the solvent is divided into two processes of swelling and dissolving, wherein the swelling is a process that solvent small molecules enter pores of high polymer particles, the high polymer particles expand, and a macromolecular chain stretches and opens. Dissolution is the process by which the opened macromolecules and solvent small molecules form a binary homogeneous phase. In the process of developing a new material, the mastering of the swelling property is necessary for development and application, and plays a vital role in applying the new material to a production and manufacturing link.
At present, the swelling and dissolution characteristics of the high polymer for the lithium ion battery are evaluated simply in the industry, a unified technique and standard are not formed, a quantitative value cannot be given, and a quantitative value of a swelling process of the high polymer material cannot be provided.
Disclosure of Invention
In view of the above, the present invention provides a device and a method for measuring swelling characteristics of a polymer for a lithium battery, wherein a volume is monitored at any time, a data acquisition and processing system converts the volume into a swelling characteristic value to form a characteristic curve of the swelling characteristic value, and a characteristic curve of the swelling characteristic value is formed to represent a process in which small solvent molecules enter macromolecular particles of a high molecular polymer, so that the particles expand, a molecular chain is opened, and the molecules stretch to a thermodynamically stable binary homogeneous system.
In order to achieve the 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, and the mobilizable steel mesh of having placed in the swelling room, the top of steel mesh are fixed with the guide arm, and the feed inlet department of swelling room is filled with the plug, and it has the trompil that holds the guide arm and pass to open on the plug, and the top of swelling room is equipped with laser range finder, still opens the through-hole that the laser that holds laser range finder passed on the plug.
Furthermore, the device also comprises a fixing frame, and a groove for placing the swelling chamber is formed downwards in the top of the fixing frame.
Further, the top of the ejector rod is hung on the top of the rubber plug.
Furthermore, the laser range finder is connected with the data acquisition and processing system through an electric signal.
A method for characterizing the swelling characteristics of a high polymer, comprising the steps of:
(1) calculating the mass of the high polymer to be added:
(A) measuring a solvent for dissolving the high polymer, and standing under a 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) Measuring the distance from the laser range finder to the bottom of the swelling chamber by using the laser range finder and recording the distance as H0；
Further, the operation step of constant temperature is carried out in a constant temperature tank.
Furthermore, the temperature fluctuation of the thermostatic bath 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 range finder is measured by the laser range finder and recorded as H1；
(E) The total volume V of solvent in the swelling chamber was calculated according to the following formula0：
V0＝(H1-H0)×(Φ/2)2X 3.14, wherein Φ is the inner diameter of the swelling chamber;
(F) the mass W of the polymer to be added to the swelling chamber was calculated according to the following formula0；
W0＝V0(1-alpha) x alpha, wherein alpha is the mass percent of the polymer in the solution after swelling;
the density of the solvent used is calculated as 1g/cm3And (4) calculating.
(2) Characterization of the swelling characteristics of the polymer:
(A) a weight of W1Wherein W is1＝W0+/-0.0005 g, putting the weighed high polymer into a swelling chamber;
furthermore, when an organic solvent is used as a solvent of the high polymer, for example, when NMP and cyclohexane are used to dissolve 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, pure water is used to measure the swelling property of CMC, the rubber plug made of ordinary rubber material is only needed.
(C) Measuring swelling time T in real time by using a laser range finder and measuring distance H between the top of the liquid level in the step (B) in the step (2) and the laser range finder2And the volume of the solution during swelling was calculated according to the following formula: v2＝(H2-H0)×(Φ/2)2×3.14；
(D) Stopping the measurement when the characteristic swelling value eta does not change or changes little with the swelling time T, wherein the characteristic swelling value eta is V2/W1(ii) a And drawing a relation curve of the swelling time T and the swelling characteristic value eta, namely a curve for representing the swelling characteristic of the high polymer.
Further, said H2、H1、H0Phi is in mm, and V is2、V1All units of (A) are mL, the W1、W0The unit of (a) is g, and the unit of eta is mL/g.
Further, the constant temperature in the step (C) in the step (1) is preferably 20 to 25 ℃.
Furthermore, the inner diameter value of the swelling chamber is not less than 5mm and not more than 15mm, the inner diameter precision of the swelling chamber is not less than +/-0.01 mm, the cylindricity of the swelling chamber is not more than 3um, the surface roughness of the swelling chamber is not less than 0.8, and the height value of the swelling chamber is not less than 100mm and not more than 300 mm.
Furthermore, the diameter of the guide rod is less than or equal to 0.5mm, and meshes with the aperture less than or equal to 20um are formed in the steel mesh.
Further, the material of the steel net is preferably sus 304.
Further, the mass of the polymer was weighed using a balance, and the balance precision was 0.0001 g.
Furthermore, the measurement accuracy of the laser range finder is 0.01mm, the measuring range is selected according to the height of the swelling chamber, and the preferential brand of the laser range finder is Keynes.
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 function of forming a real-time monitoring curve is achieved, and the checking by an operator is facilitated; has the function of exporting the original data.
Compared with the prior art, the device for measuring the swelling characteristic of the high polymer for the lithium battery and the characterization method have the following advantages:
(1) according to the device and the method for measuring the swelling characteristic of the high polymer for the lithium battery, disclosed by the invention, the volume is monitored at any time, the data acquisition and processing system converts the volume into the swelling characteristic value, a characteristic curve of time and the swelling characteristic value is formed, and small molecules of a solvent enter macromolecular particles to be characterized, so that the process of a thermodynamically stable binary homogeneous system is achieved by particle expansion, molecular chain opening and stretching.
(2) According to the device and the method for measuring the swelling characteristic of the high polymer for the lithium battery, disclosed by the invention, the swelling characteristic of the material can be rapidly mastered through a swelling quantitative curve, the process parameter formulation of a new material in a production and manufacturing link can be facilitated, and the swelling and dissolving characteristics of the high polymer of the new material can be rapidly mastered through comparing the new material with the existing model quantitative characteristic curve during the development of the new material, so that the reasonable production process parameter can be rapidly formulated.
(3) The device and the method for measuring the swelling characteristic of the high polymer for the lithium battery quantize the swelling process of the high polymer through the characteristic curves of time and a swelling characteristic value, quantize the swelling process through the volume change in the swelling process, and give a quantization curve.
Drawings
The accompanying drawings, which 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 without limitation. In the drawings:
FIG. 1 is a schematic view of a measuring device according to an embodiment of the present invention;
FIG. 2 is an enlarged view of a portion of A in FIG. 1 of the present application;
FIG. 3 is a schematic SEM topography of sample A according to an embodiment of the present invention;
FIG. 4 is a SEM diagram of sample B according to the inventive example;
FIG. 5 is a schematic diagram of the swelling curve of PVDF according to the inventive example.
Description of reference numerals:
1-high polymer powder layer; 2-a swelling chamber; 3-a constant temperature tank; 4-a steel mesh; 5-a guide rod; 6-rubber plug; 7-a fixing frame; 8-laser rangefinder; and 9, a data acquisition and processing system.
Detailed Description
It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings, which are merely for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be construed as limiting the invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the invention, the meaning of "a plurality" is two or more unless otherwise specified.
In the description of the invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted", "connected" and "connected" are to be construed broadly, e.g. as being fixed or detachable or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. Unless otherwise specifically stated or limited, the term "fixedly connected" may be a commonly used fixedly connected manner such as a plug, a weld, a threaded connection, a bolt connection, etc. 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 through specific situations.
The invention will be described in detail with reference to the following embodiments with reference to the attached drawings.
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, mobilizable steel mesh 4 of having placed in the swelling room 2, and the top of steel mesh 4 is fixed with guide arm 5, and the feed inlet department of swelling room 2 is filled with plug 6, and it has the trompil that holds guide arm 5 and pass to open on the plug 6, and the top of swelling room 2 is equipped with laser range finder 8, still opens the through-hole that the laser that holds laser range finder 8 passed on the plug 6.
The swelling device also comprises a fixing frame 7, and a groove for placing the swelling chamber 2 is formed downwards in the top of the fixing frame 7.
Care was taken during the experiment to maintain the level of the mounting frame 7 and the swelling chamber 2.
The top of the ejector rod is hung on the top of the rubber plug 6.
The laser range finder is characterized by further comprising 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 for characterizing the swelling characteristics of a high polymer, comprising the steps of:
(1) calculating the mass of the high polymer to be added:
(A) measuring a solvent for dissolving the high polymer, and standing under a 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 range finder 8 to the bottom of the swelling chamber 2 by using the laser range finder 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 subjected to defoaming in the step (1) into a swelling chamber 2, and keeping the temperature for a certain time;
the operation step of the constant temperature is performed in the constant temperature bath 3.
The temperature fluctuation of the thermostatic bath 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 laser range finder 8 measures the distance from the top of the liquid level of the solvent in the step (3) to the laser range finder 8, and records the distance as H1；
(E) The total volume V of solvent in the swelling chamber 2 was calculated according to the following formula0：
V0＝(H1-H0)×(Φ/2)2X 3.14, where Φ is the inner diameter of the swelling chamber 2;
(F) the mass W of the polymer to be added to the swelling chamber 2 was calculated according to the following formula0；
W0＝V0(1-alpha) x alpha, wherein alpha is the mass percent of the polymer in the solution after swelling;
(2) characterization of the swelling characteristics of the polymer:
(A) a weight of W1Wherein W is1＝W0+/-0.0005 g, putting the weighed high polymer into a swelling chamber 2;
the high polymer is weighed at normal temperature and humidity less than or equal to 10% after being dried, and is not allowed to be exposed in a high-humidity environment before being added into the swelling chamber 2, so that the unfolding and opening of high polymer chains in the solvent are prevented from being influenced by the water absorption of the high polymer.
Pressing and soaking the high polymer powder into the 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 the swelling chamber 2;
the diameter of the opening of the rubber plug 6 is smaller and better on the premise of meeting the operation requirement, so that the error caused by NMP volatilization in the swelling process is reduced.
When an organic solvent is used as a solvent of the high polymer, for example, when 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, pure water is used to measure the swelling property of CMC, the rubber plug 6 made of ordinary rubber is sufficient.
(C) The laser range finder 8 measures the swelling time T in real time and the distance H2 from the top of the liquid surface to the laser range finder 8 in the step (B) in the step (2), and calculates the volume of the solution in the swelling process according to the following formula: v2＝(H2-H0)×(Φ/2)2×3.14；
(D) Stopping the measurement when the characteristic swelling value eta does not change or changes little with the swelling time T, wherein the characteristic swelling value eta is V2/W1(ii) a And drawing a relation curve of the swelling time T and the swelling characteristic value eta, namely a curve for representing the swelling characteristic of the high polymer.
Said H2、H1、H0Phi is in mm, and V is2And V1 are all in mL, the W1、W0The unit of (a) is g, and the unit of eta is mL/g.
The constant temperature in the step (C) in the step (1) is preferably 20 to 25 ℃.
The inner diameter value of the swelling chamber 2 is not less than 5mm and not more than 15mm, the precision of the swelling chamber 2 is not less than +/-0.01 mm, the cylindricity of the swelling chamber 2 is not more than 3um, the surface roughness of the swelling chamber 2 is not less than 0.8, and the height value of the swelling chamber 2 is not less than 100mm and not more than 300 mm.
The smaller the inner diameter of the swelling chamber 2, the higher the liquid level height can 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, so that the rubber plug 6 is smaller, the hole diameter of the opening on the rubber plug 6 is too small, the laser alignment of the laser range finder 8 is not accurate enough, the accuracy of the measured data is affected, and the meniscus can be formed at the top of the liquid level if the inner diameter is too small, so that the measurement is not accurate.
During the swelling process, the total volume of the solution will gradually decrease as the polymer is continuously swollen in the solvent.
The swelling chamber 2 is a tool for precisely measuring the volume, is kept properly and is prevented from colliding, high-pressure water is used for washing during washing, compressed air is used for drying, and the hard objects such as steel wire balls and the like are prevented from being scratched.
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 less than or equal to 20 um.
The material of the steel net 4 is preferably sus 304.
The balance was weighed to the mass of the polymer with a balance precision of 0.0001 g.
The weighed PVDF is slowly introduced into the swelling chamber 2, taking care to avoid the powder sticking to the inner walls of the swelling chamber 2.
The measuring precision of the laser distance measuring instrument 8 is 0.01mm, the measuring range is selected according to the height of the swelling chamber 2, and the preferential brand of the laser distance measuring instrument 8 is Keynes.
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 function of forming a real-time monitoring curve is achieved, and the checking by an operator is facilitated; has the function of exporting the original data.
The addition amount of the solvent needs to be slightly higher than the amount of the solvent needed for swelling and dissolving the high molecular polymer, so that the influence on the swelling speed of the high molecular polymer due to too small amount of the solvent is reduced.
Examples
Preparation work:
one beaker (200ml), one pipette (10ml) and one aurilave, and the vacuum chamber is connected with a vacuum pump; leveling the fixed frame; the inner diameter of the swelling chamber is 10mm, and the height of the swelling chamber is 200 mm; two PVDF samples have the following physical property parameters:
TABLE 1 parameter List for two PVDF samples
The specific operation process comprises the following steps:
measurement of sample a:
(1) defoaming by using high polymer NMP: taking about 100ml of NMP by using a beaker, placing the NMP in a negative pressure cavity for defoaming, wherein the vacuum degree is less than or equal to-90 KPa, and the defoaming time is 30 min;
(2) transferring and taking NMP: 10ml of NMP solution was pipetted into the swelling chamber 2, and the thermostatic bath 3 was opened, and the temperature was set at 20 ℃ for 1 hour. Starting the laser range finder 8, starting the data acquisition and processing system 9, measuring and calculating to obtain the volume V of the NMP in the swelling chamber 20＝10.0602ml；
(3) PVDF weighing: drying the PVDF powder for 12 hours at 80 ℃ under the vacuum degree of less than or equal to-90 KPa; according to V010.0602ml, swelling was calculated according to the following formula to give a mass of PVDF of 6% by mass: w0＝V0/(1-6％)×6％＝10.0602/(1-6％)×6％＝0.6421g；
Weighing W10.6425g, mixing W1The 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, preferably pressing and immersing the powder to the middle position of the liquid surface of the NMP solvent visually, and pressing a rubber plug 6 on a liquid inlet of the swelling chamber 2;
(5) the data acquisition and processing system 9 measures and calculates to obtain V1And will V1Converting into a swelling characteristic value eta;
(6) an execution mode is set on the data acquisition and processing system 9:
the first step is as follows: the data acquisition interval is 10s, and the execution time is 12 hours;
the second step is that: the data acquisition interval is 60s, and the execution time is 12 hours;
the third step: the data acquisition interval is 120s, the execution time is 24 hours, and the process is finished;
measurement of sample B:
(7) repeating the above steps (1) to (6), and testing the sample B;
(8) exporting data and sorting;
(9) and (3) data analysis:
the two samples are two products of the same manufacturer with different models, and can be obtained by comparing characteristic curves:
sample A achieves binary phase homogenization for about 30 hours, and sample B requires about 46 hours, so the swelling property of sample A is better than that of sample B;
at the initial stage of swelling, the NMP solvent has better ability to enter the powder particles of the sample A than the sample B;
in the late swelling stage, the polymer of sample B is less stretched and opened than sample A;
assuming that the sample A is a currently used product, according to the glue-making production parameters of the sample A, the sample B can be presumed to be slightly improved on the basis of the sample A in stirring time, temperature, rotating speed and the like so as to obtain a glue solution with excellent quality.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the invention, so that any modifications, equivalents, improvements and the like, which are within the spirit and principle of the present invention, should be included in the scope of the present invention.
Claims (6)
1. A measuring device for swelling characteristics of high polymer for lithium batteries is characterized in that: including swelling room (2) for placing high polymer and solvent, mobilizable steel mesh (4) of having placed in swelling room (2), the top of steel mesh (4) is fixed with guide arm (5), the liquid inlet department of swelling room (2) is filled with plug (6), it has the trompil that holds guide arm (5) and pass to open on plug (6), the top of swelling room (2) is equipped with laser range finder (8), still open the through-hole that the laser that holds laser range finder (8) passed on plug (6).
2. The apparatus for measuring swelling characteristics of a high polymer for lithium battery as claimed in claim 1, wherein: the swelling device also comprises a fixing frame (7), and a groove for placing the swelling chamber (2) is formed downwards in the top of the fixing frame (7).
3. A method for characterizing the swelling behavior of a polymer using a measuring device according to any one of claims 1-2, wherein: the method comprises the following steps:
(1) calculating the mass of the high polymer to be added:
(A) measuring a solvent for dissolving the high polymer, and standing under a negative pressure condition to remove bubbles;
(B) measuring the distance from the laser range finder (8) to the bottom of the swelling chamber (2) by using the laser range finder (8) and recording the distance as H0；
(C) Putting the solvent subjected to defoaming 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 laser range finder (8) measures the distance from the top of the liquid level of the solvent in the step (3) to the laser range finder (8), and the distance is recorded as H1；
(E) The total volume V of solvent in the swelling chamber (2) is calculated according to the following formula0：
V0＝(H1-H0)×(Φ/2)2X 3.14, wherein Φ is the inner diameter of the swelling chamber (2);
(F) the mass W of the polymer to be added to the swelling chamber (2) is calculated according to the following formula0；
W0＝V0(1-alpha) x alpha, wherein alpha is the mass percent of the polymer in the solution after swelling;
(2) characterization of the swelling characteristics of the polymer:
(A) a weight of W1Wherein W is1＝W0+/-0.0005 g, putting the weighed high polymer into a swelling chamber (2);
(B) pressing and soaking the high polymer powder into the 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 the swelling chamber (2);
(C) the laser range finder (8) measures the swelling time T in real time and the distance H from the top of the liquid level to the laser range finder (8) in the step (2) and the step (B)2And the volume of the solution during swelling was calculated according to the following formula: v2＝(H2-H0)×(Φ/2)2×3.14；
(D) When swelling is characterizedStopping the measurement when the value eta does not or very little change with the swelling time T, wherein the swelling characteristic value eta is V2/W1(ii) a And drawing a relation curve of the swelling time T and the swelling characteristic value eta, namely a curve for representing the swelling characteristic of the high polymer.
4. The method for characterizing the swelling behavior of polymers according to claim 3, wherein: the constant temperature in the step (C) in the step (1) is preferably 20 to 25 ℃.
5. The method for characterizing the swelling behavior of polymers according to claim 3, wherein: the inner diameter value of the swelling chamber (2) is not less than 5mm and not more than 15mm, the inner diameter precision of the swelling chamber (2) is not less than +/-0.01 mm, the cylindricity of the swelling chamber (2) is not more than 3um, the surface roughness of the swelling chamber (2) is not less than 0.8, and the height value of the swelling chamber (2) is not less than 100mm and not more than 300 mm.
6. The method for characterizing the swelling behavior of polymers according to claim 3, 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 less than or equal to 20 um.
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