CN111721674A - Testing method and testing device for pole piece infiltration state - Google Patents
Testing method and testing device for pole piece infiltration state Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 72
- 238000001764 infiltration Methods 0.000 title claims abstract description 36
- 230000008595 infiltration Effects 0.000 title claims abstract description 35
- 239000003792 electrolyte Substances 0.000 claims abstract description 105
- 238000005070 sampling Methods 0.000 claims abstract description 47
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 31
- 238000009736 wetting Methods 0.000 claims abstract description 14
- 238000009616 inductively coupled plasma Methods 0.000 claims description 32
- 239000012086 standard solution Substances 0.000 claims description 29
- 239000000523 sample Substances 0.000 claims description 25
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 24
- 229910052698 phosphorus Inorganic materials 0.000 claims description 24
- 239000011574 phosphorus Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000012496 blank sample Substances 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- -1 nickel-cobalt-aluminum Chemical compound 0.000 claims description 6
- 238000002203 pretreatment Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 3
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 3
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 2
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 2
- 230000001939 inductive effect Effects 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- 239000010703 silicon Substances 0.000 claims description 2
- 238000004611 spectroscopical analysis Methods 0.000 claims description 2
- 238000001228 spectrum Methods 0.000 claims description 2
- 238000010998 test method Methods 0.000 claims 6
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 23
- 239000007788 liquid Substances 0.000 abstract description 11
- 238000001514 detection method Methods 0.000 abstract description 8
- 238000002347 injection Methods 0.000 abstract description 7
- 239000007924 injection Substances 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 230000003595 spectral effect Effects 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000012452 mother liquor Substances 0.000 description 2
- 239000010413 mother solution Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000003755 preservative agent Substances 0.000 description 2
- 230000002335 preservative effect Effects 0.000 description 2
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 1
- 239000005955 Ferric phosphate Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229940032958 ferric phosphate Drugs 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
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- Secondary Cells (AREA)
Abstract
The invention provides a testing method and a testing device for a pole piece infiltration state. The method comprises the following steps: 1) selecting target elements according to the types of the pole pieces to be detected and the components of the electrolyte; 2) sampling is carried out on the pole piece to be tested which is not soaked in the electrolyte and the pole piece to be tested which is soaked in the electrolyte, and the content of the target element is tested to obtain the wetting condition of the pole piece. The pole piece infiltration state testing method provided by the invention realizes electrolyte infiltration state detection in the practical production of the lithium ion battery, improves the pole piece infiltration detection from the theoretical to the practical, and truly detects the infiltration state of the pole piece after the liquid injection of the lithium ion battery is finished.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a testing method and a testing device for a pole piece infiltration state.
Background
According to the existing theory, the lithium ion battery mainly comprises a positive electrode, a negative electrode, a diaphragm, electrolyte, a structural component and the like. In the lithium ion battery, electrons are conducted between the positive electrode and the negative electrode through a lead, a load and the like, in the battery, the positive electrode and the negative electrode are connected through electrolyte, Li + is diffused from the negative electrode to the positive electrode through the electrolyte during discharging and is embedded into a crystal structure of the positive electrode, and the reverse process occurs during charging. Therefore, in the lithium ion battery, the electrolyte is very important and has an important influence on the performance of the lithium ion battery. If the electrolyte in the lithium ion battery cannot be uniformly distributed, the performance of the lithium ion battery is adversely affected.
The first method is to drop electrolyte of the lithium ion battery on the surfaces of the positive and negative pole pieces of the lithium ion battery by using a rubber head dropper and then observe the time for the electrolyte to soak the surfaces of the pole pieces. The second method is to hang the positive and negative pole pieces of the lithium ion battery on a frame, draw a line at a certain distance from the bottom end of the pole piece, place the electrolyte of the lithium ion battery under the pole piece, immerse the pole piece in the electrolyte, and observe the time required for the electrolyte to diffuse to the line drawing position above the pole piece. And thirdly, pretreating the pole piece, coating a polyvinylidene fluoride layer on the surface of the pole piece, immersing the treated pole piece into electrolyte, and calculating the infiltration speed according to the mass of the electrolyte entering the pole piece to be tested within a certain time.
CN110487665A discloses a method for detecting wettability of a pole piece, which comprises the following steps: s1, pole piece pretreatment: coating a polyvinylidene fluoride layer on the surface of the pole piece to obtain a pole piece to be detected; s2, detecting wettability: and immersing the pole piece to be tested into the electrolyte, and calculating the infiltration speed according to the mass of the electrolyte entering the pole piece to be tested within a certain time. According to the invention, the surface of the pole piece is coated with the vinylidene fluoride layer, then the pole piece is immersed in the electrolyte, and the infiltration speed is calculated according to the mass of the electrolyte entering the pole piece to be tested within a certain time, so that the infiltration of the pole piece is tested.
CN110333461A discloses a method for characterizing electrolyte wettability by tortuosity, which comprises the following steps: manufacturing a pole piece; recording the thickness d and porosity of an active substance of the pole piece and the conductivity kappa of the electrolyte to be injected; assembling the pole pieces into a positive electrode or negative electrode symmetrical battery with a laminated or wound structure; injecting electrolyte into the symmetrical battery, monitoring and detecting impedance change after sealing, drawing an impedance-infiltration time map, and calculating the pore impedance R of the whole symmetrical battery and the pore impedance Rpore of the electrolyte on a single pole piece as n.R; and (4) calculating the change tau of the tortuosity of the pole piece, wherein the change tau is Rcore, A, kappa and/d.
CN102866084A discloses a method for measuring wettability of lithium or lithium ion battery electrolyte to battery materials. The method comprises the following steps: 1) preparation of the test substrate: manufacturing a positive electrode, a negative electrode and a diaphragm of the battery into a sheet sample with a smooth and flat surface to be used as a test substrate of electrolyte to be tested; 2) preparing an electrolyte: preparing electrolyte as electrolyte to be detected according to the principle of matching with the battery; 3) the wettability of the electrolyte was measured at 25 ℃ at room temperature: observing and photographing the falling process of the electrolyte liquid drop to be measured by using a contact angle measuring instrument to obtain a wettability photo of the electrolyte to be measured on a battery anode, a battery cathode and a diaphragm, and analyzing the obtained photo by using a half-angle method; 4) the wettability of the electrolyte was measured at a low temperature of 0 ℃ at 20 ℃: and placing the electrolyte, the test substrate and the contact angle tester in a low-temperature refrigerator in a drying room, and detecting the low-temperature wettability of the electrolyte.
However, the above methods are all to test the liquid absorption of the pole piece in a free state, and only the comparison of pole pieces in different schemes can be made, but there is still no way to detect the infiltration state of the pole piece after the liquid injection of the lithium ion battery is completed.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a method and an apparatus for testing the pole piece wetting state. The pole piece infiltration state testing method provided by the invention can detect the infiltration state of the pole piece after the liquid injection of the lithium ion battery is finished, but not the liquid absorption of the pole piece in the conventional free state, thereby solving the technical problem that the pole piece infiltration state is difficult to detect after the liquid injection is finished.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for testing a pole piece wetting state, the method comprising the following steps:
(1) selecting target elements according to the types of the pole pieces to be detected and the components of the electrolyte;
(2) sampling on the pole piece to be tested which is not soaked in the electrolyte and the pole piece to be tested which is soaked in the electrolyte, and testing the content of the target element in the step (1) to obtain the wetting condition of the pole piece.
According to the pole piece infiltration state testing method provided by the invention, the target element is selected, and the content of the target element in different areas in the pole piece is quantitatively analyzed according to the characteristic that the target element cannot be lost along with the evaporation of the organic solvent of the electrolyte in the pole piece. After the content is obtained, the standard deviation can be used as an index for representing the uniformity degree of the electrolyte in different areas of the pole piece.
The pole piece infiltration state testing method provided by the invention realizes the electrolyte infiltration state detection of the lithium ion battery in the actual production, improves the pole piece infiltration detection from the theoretical to the actual, and truly detects the infiltration state of the pole piece after the liquid injection of the lithium ion battery is finished.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
As a preferred technical scheme of the invention, the pole piece to be tested in the step (1) comprises a positive pole piece and/or a negative pole piece.
Preferably, the positive electrode piece includes any one of or a combination of at least two of a lithium cobalt oxide positive electrode piece, a lithium manganese oxide positive electrode piece, a nickel cobalt manganese ternary positive electrode piece or a nickel cobalt aluminum ternary positive electrode piece.
Preferably, the negative electrode plate includes any one of a graphite negative electrode plate, a silicon negative electrode plate, or a silicon-carbon negative electrode plate, or a combination of at least two of them.
In a preferred embodiment of the present invention, the electrolyte in step (1) includes lithium and phosphorus.
Besides ferric phosphate lithium, other positive electrode materials generally do not contain phosphorus elements, and other negative electrode materials generally do not contain lithium elements except lithium titanate, so that the solute of the electrolyte comprises lithium elements and phosphorus elements, which are beneficial to adopting the two elements as target elements to obtain the wetting state data of the pole piece through an inductively coupled plasma test.
Preferably, the electrolyte in step (1) comprises lithium hexafluorophosphate.
The material is common in electrolyte, and contains lithium element and phosphorus element, which is beneficial to carrying out inductively coupled plasma test to obtain the infiltration state data of the pole piece.
Preferably, the electrolyte in step (1) further comprises any one or a combination of at least two of ethylene carbonate, dimethyl carbonate, propylene carbonate or diethyl carbonate.
As a preferred technical scheme of the invention, the pole piece to be tested in the step (1) is a positive electrode, the electrolyte comprises phosphorus, and the target element is phosphorus.
Preferably, the pole piece to be tested in the step (1) is a negative electrode, the electrolyte comprises lithium element, and the target element is lithium element.
Namely, if the anode does not contain phosphorus and the electrolyte contains phosphorus, the phosphorus is selected as the target element of the anode piece, so that the electrolyte infiltration condition can be obtained without being interfered by the components of the anode.
If the negative electrode does not contain lithium element and the electrolyte contains lithium element, the lithium element is selected as the target element of the negative electrode pole piece, so that the electrode liquid immersion condition can be obtained without being interfered by the components of the negative electrode.
As a preferable technical scheme of the invention, the sampling in the step (2) comprises sampling at different positions of the pole piece to be tested which is not immersed in the electrolyte. The samples are taken at different positions, so that the soaking conditions of the electrolyte on different positions of the pole piece can be more clearly known.
Preferably, the sampling in the step (2) includes sampling at different positions of the pole piece to be tested, which is immersed in the electrolyte.
Preferably, in the sampling in the step (2), the sampling position of the pole piece to be detected, which is not immersed in the electrolyte, is the same as the sampling position of the pole piece to be detected, which is immersed in the electrolyte. This may make the test results more comparable.
As a preferable technical scheme of the present invention, in the step (2), the electrode plate to be tested soaked in the electrolyte is a pre-charged and standing electrode plate in the battery cell.
The standing is to enable the electrolyte to gradually soak in the pole piece.
Preferably, the standing time is 12-48h, such as 12h, 18h, 24h, 30h, 36h, 42h or 48h and the like.
As a preferable technical scheme of the invention, the test in the step (2) is an Inductively Coupled Plasma (ICP) test.
By adopting the test, the quantitative analysis can be carried out on the target element, and further the infiltration condition of the pole piece can be obtained. Further, before the ICP test was performed, it was determined that the linearity of each element was 3 or more and 9 or less.
Preferably, the inductively coupled plasma test is an inductively coupled plasma spectroscopy test.
As the preferable technical scheme of the invention, the inductively coupled plasma test in the step (2) adopts a standard curve method;
preferably, the method of obtaining the standard curve comprises: and transferring the mixed standard solution, mixing the mixed standard solution with water to a constant volume, mixing the mixed standard solution with nitric acid to prepare standard solutions with different concentrations, using water as a blank standard solution, and testing the standard solutions with different concentrations and the blank standard solution to obtain a standard curve.
The mixed standard solution can use a commercial product. The water is pure water. It should be noted that the mixed standard solution is usually a reagent matched with the inductively coupled plasma spectrometer, and the instrument manufacturer or the same company can purchase the corresponding mixed standard solution according to the element to be tested.
As a preferable embodiment of the present invention, the step (2) further comprises: pre-treating the sample taken prior to performing the inductively coupled plasma test.
Preferably, the method of pre-treatment comprises: and mixing the sample with aqua regia, heating to react to dissolve the sample, cooling after reaction, filtering, and fixing the volume to obtain the pretreated sample.
Preferably, the heating temperature is 155-165 ℃, such as 155 ℃, 156 ℃, 157 ℃, 158 ℃, 159 ℃, 160 ℃, 161 ℃, 162 ℃, 163 ℃, 164 ℃ or 165 ℃.
Preferably, the reaction time is 1-2h, such as 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, or the like.
Preferably, step (2) further comprises: a blank sample was prepared in the same manner as the pretreatment except that the sample was not used.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) selecting target elements according to the types of the pole pieces to be detected and the components of the electrolyte;
when the pole piece to be detected is a positive electrode, the electrolyte comprises a phosphorus element, and the target element is the phosphorus element; when the pole piece to be detected is a negative electrode, the electrolyte comprises lithium element, and the target element is lithium element;
(2) sampling on the pole piece to be tested which is not soaked in the electrolyte and the pole piece to be tested which is soaked in the electrolyte, and carrying out inductive coupling plasma test to obtain the wetting condition of the pole piece;
the sampling comprises sampling at different positions of the pole piece to be detected which is not soaked in the electrolyte and sampling at different positions of the pole piece to be detected which is soaked in the electrolyte; in the sampling, the sampling position of the pole piece to be detected which is not soaked in the electrolyte is the same as the sampling position of the pole piece to be detected which is soaked in the electrolyte;
the pole piece to be tested soaked in the electrolyte is a pole piece in the battery cell which is pre-charged and stands for 12-48 hours;
the inductively coupled plasma test is an inductively coupled plasma spectrum test, and a standard curve method is adopted for the inductively coupled plasma test;
pre-treating the obtained sample before the inductively coupled plasma test; the pretreatment method comprises the following steps: mixing the sample with aqua regia, heating at 155-165 ℃ for reaction for 1-2h to dissolve the sample, cooling after reaction, filtering, and fixing the volume to obtain a pretreated sample; meanwhile, a blank sample was prepared in the same manner as the pretreatment except that the sample was not used.
In a second aspect, the present invention provides a testing apparatus for detecting a pole piece saturation state, which is implemented based on the pole piece saturation state testing method described in any of the above embodiments. That is, the pole piece wetting state testing method provided by the present invention has potential application in a testing apparatus, i.e., a structural design can be performed according to the pole piece wetting state testing method described in the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
the pole piece infiltration state testing method provided by the invention realizes electrolyte infiltration state detection in the practical production of the lithium ion battery, improves the pole piece infiltration detection from the theoretical to the practical, and truly detects the infiltration state of the pole piece after the liquid injection of the lithium ion battery is finished.
Drawings
FIG. 1 is a schematic diagram of the sampling positions on the pole piece in example 1, wherein the marks 1, 2, 3, 4 and 5 are sampling points.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Example 1
In this embodiment, the pole piece wetting state is tested according to the following method:
(1) the pole piece to be detected is a positive pole piece and a negative pole piece of the lithium ion battery, the positive pole piece is a lithium cobaltate positive pole piece, the negative pole piece is a graphite negative pole piece, and the electrolyte contains lithium hexafluorophosphate, ethylene carbonate and dimethyl carbonate, so that phosphorus is selected as a target element of the positive pole piece, and lithium is selected as a target element of the negative pole piece.
(2) Taking positive and negative pole pieces in the bare roll core without electrolyte, respectively naming the positive and negative pole pieces as no positive/no negative, sampling and carrying out ICP spectral test, wherein schematic diagrams of sampling positions on the positive pole piece and the negative pole piece are shown in figure 1, wherein 1, 2 and 3 in the figures are taken as representative areas for infiltration of upper, middle and lower parts of the pole pieces, and 4 and 5 in the figures are taken as representative areas for infiltration of left and right parts of the pole pieces.
Taking positive and negative pole pieces in the cell, which are taken with the electrolyte and are kept stand for 24 hours after pre-charging, respectively naming the positive pole piece and the negative pole piece as positive/negative, sampling and carrying out ICP spectral test, wherein the sampling positions on the positive pole piece and the negative pole piece (namely, positive and negative) soaked with the electrolyte are also shown in figure 1 and are the same as the sampling positions on the non-positive and non-negative poles.
Wherein, the ICP spectral test adopts a standard curve method to obtain the content of the lithium element or the phosphorus element. The standard curve is obtained by performing ICP spectral test on a standard solution, and the preparation method of the standard solution comprises the following steps:
(1) 10ml of the mixed standard solution of 100. mu.g/ml was pipetted into a 100ml volumetric flask and the volume was fixed with pure water to obtain a mixed standard mother solution of 10. mu.g/ml.
(2) Respectively transferring 0ml/2ml/4ml/6ml/8ml mixed standard mother liquor and phosphorus single standard solution into five 100ml volumetric flasks by using a pipette, adding 5ml of superior pure nitric acid, and fixing the volume by using pure water to obtain standard solution blank/0.2/0.4/0.6/0.8 mu g/ml standard solution.
For the samples taken on the pole pieces, pretreatment is carried out before the ICP test, and for each sample, the pretreatment method is as follows:
(1) weigh 1g of pole piece into a clean dry beaker and record the mass. The beaker mouth is sealed by a preservative film and numbers are written on the preservative film.
(2) Transferring 9ml of aqua regia into a beaker by using a transfer pipette, and slightly shaking the beaker to ensure that the powder is completely soaked by the aqua regia
(3) The beaker was placed on a hot plate (160 ℃ C.) and the time to boil the solution was 1 h. (prolonged time if dissolution is incomplete)
(4) Taking down the beaker from the heating plate, placing in a fume hood, standing, and cooling
(5) After the solution is completely cooled, the solution is filtered into a 100ml volumetric flask, pure water is added for constant volume, and the serial number of the sample is recorded on the volumetric flask. The preparation of the blank sample is completely the same as the sample pretreatment step except that the powder is not added in the step one, and the blank sample is marked on a volumetric flask.
The test results are given in the following table:
TABLE 1
From the above table, it can be calculated that the standard deviation of phosphorus element at each sampling point of the positive electrode sheet soaked by the electrolyte is 12.49, and the standard deviation of lithium element at each sampling point of the negative electrode sheet soaked by the electrolyte is 4.97, which indicates that the pole sheet soaking condition of the embodiment is good.
Example 2
In this embodiment, the pole piece wetting state is tested according to the following method:
(1) the pole piece to be detected is a positive pole piece and a negative pole piece of the lithium ion battery, the positive pole piece is a lithium manganate positive pole piece, the negative pole piece is a silicon carbon negative pole piece, and the electrolyte contains lithium hexafluorophosphate, propylene carbonate and diethyl carbonate, so that phosphorus is selected as a target element of the positive pole piece, and lithium is selected as a target element of the negative pole piece.
(2) Taking positive and negative pole pieces in the bare roll core without electrolyte, respectively naming the positive and negative pole pieces, sampling, and carrying out ICP spectral test, wherein the sampling positions on the positive pole piece and the negative pole piece refer to example 1.
Taking positive and negative pole pieces in the cell, which are taken with electrolyte and are kept stand for 12 hours after pre-charging, respectively naming the positive and negative pole pieces as positive/negative, sampling and carrying out ICP spectral test, wherein the sampling positions on the positive pole piece and the negative pole piece (namely, positive and negative) soaked with the electrolyte are the same as the sampling positions on the positive-free pole piece and the negative-free pole piece.
Wherein, the ICP spectral test adopts a standard curve method to obtain the content of the lithium element or the phosphorus element. The standard curve is obtained by performing ICP spectral test on a standard solution, and the preparation method of the standard solution comprises the following steps:
(1) 10ml of the mixed standard solution of 100. mu.g/ml was pipetted into a 100ml volumetric flask and the volume was fixed with pure water to obtain a mixed standard mother solution of 10. mu.g/ml.
(2) Respectively transferring 0ml/2ml/4ml/6ml/8ml mixed standard mother liquor and phosphorus single standard solution into five 100ml volumetric flasks by using a pipette, adding 5ml of superior pure nitric acid, and fixing the volume by using pure water to obtain standard solution blank/0.2/0.4/0.6/0.8 mu g/ml standard solution.
For the samples taken on the pole pieces, a pretreatment was carried out before the ICP test, and for each sample, the pretreatment method was the same as that of example 1.
The test results are given in the following table:
TABLE 1
From the above table, it can be calculated that the standard deviation of phosphorus element at each sampling point of the positive electrode sheet soaked by the electrolyte is 27.38, and the standard deviation of lithium element at each sampling point of the negative electrode sheet soaked by the electrolyte is 19.40, which indicates that the pole sheet soaking condition of the embodiment is good.
By combining the above embodiments, the method for testing the pole piece infiltration state provided by the invention realizes the electrolyte infiltration state detection in the actual production of the lithium ion battery, improves the pole piece infiltration detection from the theoretical to the actual, and truly detects the pole piece infiltration state of the lithium ion battery after the liquid injection is completed.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A pole piece infiltration state testing method is characterized by comprising the following steps:
(1) selecting target elements according to the types of the pole pieces to be detected and the components of the electrolyte;
(2) sampling on the pole piece to be tested which is not soaked in the electrolyte and the pole piece to be tested which is soaked in the electrolyte, and testing the content of the target element in the step (1) to obtain the wetting condition of the pole piece.
2. The testing method according to claim 1, wherein the pole piece to be tested in step (1) comprises a positive pole piece and/or a negative pole piece;
preferably, the positive electrode piece comprises any one or a combination of at least two of a lithium cobaltate positive electrode piece, a lithium manganate positive electrode piece, a nickel-cobalt-manganese ternary positive electrode piece or a nickel-cobalt-aluminum ternary positive electrode piece;
preferably, the negative electrode plate includes any one of a graphite negative electrode plate, a silicon negative electrode plate, or a silicon-carbon negative electrode plate, or a combination of at least two of them.
3. The test method according to claim 1 or 2, wherein the electrolyte of step (1) comprises lithium element and phosphorus element;
preferably, the electrolyte in the step (1) comprises lithium hexafluorophosphate;
preferably, the electrolyte in step (1) further comprises any one or a combination of at least two of ethylene carbonate, dimethyl carbonate, propylene carbonate or diethyl carbonate.
4. The test method according to any one of claims 1 to 3, wherein the pole piece to be tested in the step (1) is a positive electrode, the electrolyte comprises phosphorus, and the target element is phosphorus;
preferably, the pole piece to be tested in the step (1) is a negative electrode, the electrolyte comprises lithium element, and the target element is lithium element.
5. The test method according to any one of claims 1 to 4, wherein the sampling of step (2) comprises sampling at different positions of the pole piece to be tested which is not immersed in the electrolyte;
preferably, the sampling in the step (2) includes sampling at different positions of the pole piece to be tested, which is immersed in the electrolyte;
preferably, in the sampling in the step (2), the sampling position of the pole piece to be detected, which is not immersed in the electrolyte, is the same as the sampling position of the pole piece to be detected, which is immersed in the electrolyte.
6. The test method according to any one of claims 1 to 5, wherein in the step (2), the pole piece to be tested soaked in the electrolyte is a pole piece in a pre-charged and standing cell;
preferably, the standing time is 12-48 h.
7. The test method according to any one of claims 1 to 6, wherein the test of step (2) is an inductively coupled plasma test;
preferably, the inductively coupled plasma test is an inductively coupled plasma spectroscopy test.
8. The method of any one of claims 1-7, wherein the inductively coupled plasma test of step (2) is performed using a standard curve method;
preferably, the method of obtaining the standard curve comprises: transferring the mixed standard solution, mixing the mixed standard solution with water to a constant volume, mixing the mixed standard solution with nitric acid to prepare standard solutions with different concentrations, using water as a blank standard solution, and testing the standard solutions with different concentrations and the blank standard solution to obtain a standard curve;
preferably, step (2) further comprises: pre-treating the obtained sample before the inductively coupled plasma test;
preferably, the method of pre-treatment comprises: mixing the sample with aqua regia, heating to react to dissolve the sample, cooling after reaction, filtering, and fixing the volume to obtain a pretreated sample;
preferably, the temperature of the heating is 155-165 ℃;
preferably, the reaction time is 1-2 h;
preferably, step (2) further comprises: a blank sample was prepared in the same manner as the pretreatment except that the sample was not used.
9. The test method according to any one of claims 1 to 8, characterized in that it comprises the following steps:
(1) selecting target elements according to the types of the pole pieces to be detected and the components of the electrolyte;
when the pole piece to be detected is a positive electrode, the electrolyte comprises a phosphorus element, and the target element is the phosphorus element; when the pole piece to be detected is a negative electrode, the electrolyte comprises lithium element, and the target element is lithium element;
(2) sampling on the pole piece to be tested which is not soaked in the electrolyte and the pole piece to be tested which is soaked in the electrolyte, and carrying out inductive coupling plasma test to obtain the wetting condition of the pole piece;
the sampling comprises sampling at different positions of the pole piece to be detected which is not soaked in the electrolyte and sampling at different positions of the pole piece to be detected which is soaked in the electrolyte; in the sampling, the sampling position of the pole piece to be detected which is not soaked in the electrolyte is the same as the sampling position of the pole piece to be detected which is soaked in the electrolyte;
the pole piece to be tested soaked in the electrolyte is a pole piece in the battery cell which is pre-charged and stands for 12-48 hours;
the inductively coupled plasma test is an inductively coupled plasma spectrum test, and a standard curve method is adopted for the inductively coupled plasma test;
pre-treating the obtained sample before the inductively coupled plasma test; the pretreatment method comprises the following steps: mixing the sample with aqua regia, heating at 155-165 ℃ for reaction for 1-2h to dissolve the sample, cooling after reaction, filtering, and fixing the volume to obtain a pretreated sample; meanwhile, a blank sample was prepared in the same manner as the pretreatment except that the sample was not used.
10. A testing device for detecting the pole piece wetting state, which is realized based on the pole piece wetting state testing method of any one of claims 1 to 9.
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| CN113866155A (en) * | 2021-09-16 | 2021-12-31 | 江苏中兴派能电池有限公司 | Lithium ion battery electrolyte infiltration judgment method |
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