CN117214160A - Method for measuring dissolution rate of iron ions in lithium iron phosphate material - Google Patents
Method for measuring dissolution rate of iron ions in lithium iron phosphate material Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 70
- -1 iron ions Chemical class 0.000 title claims abstract description 70
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000000463 material Substances 0.000 title claims abstract description 29
- 238000004090 dissolution Methods 0.000 title claims abstract description 28
- 239000004094 surface-active agent Substances 0.000 claims abstract description 42
- 239000003085 diluting agent Substances 0.000 claims abstract description 32
- 239000000706 filtrate Substances 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000011259 mixed solution Substances 0.000 claims abstract description 12
- 238000007865 diluting Methods 0.000 claims abstract description 8
- 239000007788 liquid Substances 0.000 claims abstract description 8
- 238000000926 separation method Methods 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 238000001514 detection method Methods 0.000 claims description 23
- 239000007864 aqueous solution Substances 0.000 claims description 18
- 229910052708 sodium Inorganic materials 0.000 claims description 15
- 239000011734 sodium Substances 0.000 claims description 15
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 11
- 238000001914 filtration Methods 0.000 claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 238000009616 inductively coupled plasma Methods 0.000 claims description 6
- 235000010482 polyoxyethylene sorbitan monooleate Nutrition 0.000 claims description 5
- 229920000053 polysorbate 80 Chemical group 0.000 claims description 5
- 238000004993 emission spectroscopy Methods 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229940051841 polyoxyethylene ether Drugs 0.000 claims description 4
- 229920000056 polyoxyethylene ether Polymers 0.000 claims description 4
- 239000000244 polyoxyethylene sorbitan monooleate Chemical group 0.000 claims description 4
- 229940068968 polysorbate 80 Drugs 0.000 claims description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 3
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 3
- 125000005227 alkyl sulfonate group Chemical group 0.000 claims description 3
- 239000003945 anionic surfactant Substances 0.000 claims description 3
- 229910017604 nitric acid Inorganic materials 0.000 claims description 3
- 239000002736 nonionic surfactant Substances 0.000 claims description 3
- 238000005119 centrifugation Methods 0.000 claims description 2
- 230000005693 optoelectronics Effects 0.000 claims 1
- 238000012360 testing method Methods 0.000 abstract description 27
- 239000000243 solution Substances 0.000 description 24
- 239000000843 powder Substances 0.000 description 18
- 239000002002 slurry Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- 238000005303 weighing Methods 0.000 description 7
- 239000006185 dispersion Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 238000001132 ultrasonic dispersion Methods 0.000 description 5
- 238000005070 sampling Methods 0.000 description 4
- 239000006228 supernatant Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000010828 elution Methods 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000001637 plasma atomic emission spectroscopy Methods 0.000 description 3
- 238000012549 training Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000002191 fatty alcohols Chemical class 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- FGHSTPNOXKDLKU-UHFFFAOYSA-N nitric acid;hydrate Chemical compound O.O[N+]([O-])=O FGHSTPNOXKDLKU-UHFFFAOYSA-N 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- DGEZNRSVGBDHLK-UHFFFAOYSA-N [1,10]phenanthroline Chemical compound C1=CN=C2C3=NC=CC=C3C=CC2=C1 DGEZNRSVGBDHLK-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910001447 ferric ion Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 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
- 238000003918 potentiometric titration Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- HOXWFOVSCUWIEH-UHFFFAOYSA-M sodium;4-dodecan-3-ylbenzenesulfonate Chemical compound [Na+].CCCCCCCCCC(CC)C1=CC=C(S([O-])(=O)=O)C=C1 HOXWFOVSCUWIEH-UHFFFAOYSA-M 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- 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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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
The invention relates to a method for measuring the dissolution rate of iron ions in a lithium iron phosphate material, which comprises the following steps: s1: mixing lithium iron phosphate material, surfactant and water, and uniformly dispersing to obtain a mixed solution; s2: carrying out solid-liquid separation on the mixed solution, taking filtrate, and diluting the filtrate by using a diluent to obtain a diluent; s3: and measuring the content of iron ions in the diluent to obtain the iron ion dissolution rate. According to the invention, the surfactant is added, so that iron ions in the lithium iron phosphate material can be rapidly and uniformly dissolved out, the testing efficiency and consistency are improved, and the stable, rapid and accurate determination of the dissolution rate of the iron ions in the lithium iron phosphate material is realized.
Description
Technical Field
The invention relates to the field of detection and analysis, in particular to a method for measuring the dissolution rate of iron ions in a lithium iron phosphate material.
Background
The lithium iron phosphate is a novel lithium ion battery anode material, has the advantages of high energy density, long cycle life, good safety and the like, and is widely applied to the fields of electric automobiles, energy storage systems and the like.
However, the problem of iron ion elution in lithium iron phosphate cathode materials has been one of the bottlenecks that limit their use. The dissolution of iron ions causes problems such as a decrease in battery capacity, a decrease in cycle life, and a decrease in safety. Therefore, the dissolution rate of iron ions in the lithium iron phosphate material is one of indexes for monitoring the product quality.
The current standard GB/T30835-2014 lithium ion battery carbon composite lithium iron phosphate anode material provides a method for testing the dissolution rate of iron ions in a lithium iron phosphate material, specifically, powder is dissolved in pure water, kept stand for a long time (more than or equal to 6 h), filtered, and the content of the iron ions in the filtrate is measured. However, the above method has two problems, namely, low efficiency: the treatment method has long standing time (more than or equal to 6 h); secondly, the consistency is poor: iron ions of the sample are unevenly dissolved in water, so that the consistency of detection results is poor.
Disclosure of Invention
The invention aims to overcome the defects and shortcomings of the existing method for testing the dissolution rate of iron ions in the lithium iron phosphate material, and provides a method for measuring the dissolution rate of iron ions in the lithium iron phosphate material.
The above object of the present invention is achieved by the following technical scheme:
a method for determining the dissolution rate of iron ions in a lithium iron phosphate material, comprising the steps of:
s1: mixing a lithium iron phosphate material with a surfactant aqueous solution, and uniformly dispersing to obtain a mixed solution;
s2: carrying out solid-liquid separation on the mixed solution, taking filtrate, and diluting the filtrate by using a diluent to obtain a diluent;
s3: determining the content of iron ions in the diluent to obtain the dissolution rate of the iron ions;
the mass ratio of the surfactant to water in the mixed solution of S1 is (0.03-0.07): 100.
The inventor of the invention repeatedly researches and discovers that the surfactant is added into the aqueous dispersion of the lithium iron phosphate material, so that the iron ions in the lithium iron phosphate material can be quickly and uniformly dissolved out, the testing efficiency and consistency are improved, and the stable, quick and accurate determination of the dissolution rate of the iron ions in the lithium iron phosphate material is realized.
Preferably, the surfactant in S1 is one or more of an anionic surfactant or a nonionic surfactant.
More preferably, the surfactant in S1 is one or more of sodium linear alkylbenzenesulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium secondary alkyl sulfonate or polysorbate-80.
Preferably, in the mixed solution of S1, the mass ratio of the lithium iron phosphate material to the surfactant is 1 (0.003-0.007).
Preferably, the particle size Dv50 of the lithium iron phosphate material is 0.5 μm to 20 μm.
Preferably, the dispersing time in S1 is 10min to 60min, more preferably 10min to 50min, still more preferably 10min to 20min.
The dispersion is the process of breaking the agglomeration of the lithium iron phosphate powder and leading the free iron in the lithium iron phosphate powder to be dissolved out, the dispersion time is proper, and the dispersion time is regulated, so that the effect of dissolving out the iron ions is better and the efficiency is higher (the time is short).
Preferably, the diluent in the S2 is one or more of a dilute nitric acid aqueous solution, a dilute hydrochloric acid aqueous solution or a dilute sulfuric acid aqueous solution, and the mass percentage concentration of the diluent is 2-5%.
Preferably, the mass ratio of the filtrate to the diluent in S2 is 1 (20-50). Specifically, it may be 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, etc., preferably 1 (20 to 40), more preferably 1 (20 to 30), and even more preferably 1:20.
Preferably, the solid-liquid separation in S2 is performed by centrifugation and filtration.
Conventional methods for determining the iron ion content in the art can be used in the present invention. Such as microcomputer photoelectron colorimetric detection method, iron ion concentration meter by phenanthroline spectrophotometry, inductive coupling plasma emission spectrometry, electrochemical reduction method, PH value potentiometric titration method, precipitation weighing method and the like. However, the research shows that the inductively coupled plasma emission spectrometry is used for testing the content of the iron ions, the equipment and standard solution cost is high, and the testing cost of the iron ion dissolution rate parameter is increased.
Preferably, in the step S3, the iron ion content of the diluent is measured by using a microcomputer photoelectron colorimetric detection method. The test method is accurate in measurement, simple and quick to operate, free of professional training on operators, and capable of remarkably reducing the detection cost.
Preferably, the method for determining the dissolution rate of iron ions in the lithium iron phosphate material comprises the following steps:
s1: providing a surfactant and water to prepare an aqueous surfactant solution; mixing the lithium iron phosphate material with the surfactant aqueous solution under ultrasonic and/or stirring, and uniformly dispersing to obtain a mixed solution;
s2: centrifuging and filtering the mixed solution to obtain filtrate; then diluting the filtrate by using a diluent to obtain a diluent;
s3: measuring the iron ion content of the diluent, and recording as m; and according to the measurement result, calculating to obtain the iron ion dissolution rate M.
Optionally, aIn the step S1, the mass of the lithium iron phosphate material is denoted as m 1 The mass of the aqueous surfactant solution is denoted as m 2 The method comprises the steps of carrying out a first treatment on the surface of the In the step S2, the quality of the obtained filtrate is recorded as m 3 The mass of the diluent is denoted as m 4 The method comprises the steps of carrying out a first treatment on the surface of the Iron ion dissolution rate
The invention has at least the following beneficial effects:
(1) By adding the surfactant, the free iron ions can be uniformly dissolved out from the sample in a short time, so that the test efficiency and the test stability are improved;
(2) The method avoids the problem that the particle structure of lithium iron phosphate is damaged due to long-time stirring, and iron ions are abnormally dissolved out to influence the accuracy of a test result;
(3) Furthermore, the iron ion content in the filtrate is measured by adopting a microcomputer photoelectron colorimetric detection method, the measurement is accurate and quick, the operation is simple and quick, no professional training is required for operators, and the detection cost can be obviously reduced.
Detailed Description
The invention will be further illustrated by the following specific examples in connection with the description, which are not intended to limit the invention in any way. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.
Reagents and materials used in the following examples are commercially available unless otherwise specified.
The lithium iron phosphate material or the lithium iron phosphate/carbon composite material is mainly an electrode material and is mainly used for various lithium ion batteries, unreacted and complete iron ions are inevitably called free iron in the production process, the free iron can accumulate in a form of elemental iron at the negative electrode of the battery in the charging and discharging processes, the shape of the free iron is like a branch, the separator of the battery can be pierced, the battery is short-circuited, and potential safety hazards are formed, so that downstream battery manufacturers pay attention to the content of the free iron in the lithium iron phosphate material.
The method for measuring the dissolution rate of iron ions in the lithium iron phosphate material mainly comprises the following steps:
(1) Preparing a surfactant aqueous solution A with the mass fraction of about 0.03-0.07%, wherein the surfactant is selected from anionic surfactant and nonionic surfactant, and can be one or more than two of linear sodium alkylbenzenesulfonate, fatty alcohol polyoxyethylene ether sodium sulfate, secondary sodium alkylsulfonate and polysorbate-80;
(2) Accurately weighing lithium iron phosphate powder, and adding the lithium iron phosphate powder into the solution A to obtain slurry B;
(3) Dispersing the obtained feed liquid slurry B for 10-20 min;
(4) Placing the slurry B into a high-speed centrifuge, centrifuging at 5000-10000 rpm for 5-30 min, collecting supernatant, filtering to obtain filtrate,
(5) Weight is taken as m 3 Diluting the filtrate according to the mass ratio of 1:20-1:50 to obtain a diluent, wherein the diluent is one or more than two of a dilute nitric acid aqueous solution, a dilute hydrochloric acid aqueous solution and a dilute sulfuric acid aqueous solution with the mass fraction of 2-5%,
(6) Measuring the content of iron ions in the solution by adopting a microcomputer photoelectron colorimetric detection method, and marking the content as m;
(7) And (3) calculating an iron ion dissolution content result:
m-measuring the content of iron ions in the lithium iron phosphate dissolved solution;
m 1 -lithium iron phosphate powder mass;
m 2 -the mass of the aqueous surfactant solution;
m 3 -lithium iron phosphate filtrate sampling amount;
m 4 -diluent mass.
In the following examples, the ultrasonic apparatus was purchased from Elma, germany under the name of a general-purpose ultrasonic cleaner, model S100H;
the centrifuge is purchased from Hunan, and is named as a desk type high-speed centrifuge, and the model is TG16-WS;
the HAD-Mi408 high range ion concentration meter was purchased from the company of the family of the huilongcyclic, model number Mi408 high range ion concentration meter
ICP-OES was purchased from Agilent technologies under the name inductively coupled plasma emission spectrometer, model 5110
The linear sodium alkylbenzenesulfonate surfactant, commercially available as Michael reagent, is named sodium dodecylbenzenesulfonate, under the trade designation CAS25155-30-0.
The present invention is not limited to the above-mentioned surfactants, and other similar surfactants such as sodium fatty alcohol polyoxyethylene ether sulfate (also called sodium fatty alcohol ether sulfate), sodium secondary alkyl sulfonate, polysorbate-80 (also called tween-80) and the like are also applicable to the present invention.
Example 1
The embodiment adopts a microcomputer photoelectron colorimetric detection method to test the content of iron ions in the solution to be tested, and the specific method is as follows:
(1) Weighing about 0.1g of linear sodium alkylbenzenesulfonate surfactant into a 250ml beaker, adding 200ml of pure water, and uniformly stirring to obtain an aqueous solution A with the mass percentage concentration of 0.05%;
(2) Accurately weigh weight m 1 Lithium iron phosphate powder and weight m 2 An aqueous solution A;
(3) Weight is m 1 The adding weight of the lithium iron phosphate powder is m 2 And (3) obtaining a slurry B feed liquid by using the aqueous solution A.
(4) Slurry B was sonicated for 10min.
(5) Placing the slurry into a high-speed centrifuge, centrifuging at 5000rpm for 10min, collecting supernatant, filtering to obtain filtrate, and weighing m 3 A filtrate; diluting the filtrate with 2wt% of a diluent to obtain a weight m 4 Is diluted with a diluent of (2)
(6) Measuring the content m of iron ions in the diluent by using a microcomputer photoelectron colorimetric detection method;
(7) Iron ion elution amount results were calculated:wherein:
measuring the content of iron ions dissolved out by the lithium iron phosphate by an m-microcomputer photoelectron colorimetric detection method;
m 1 -lithium iron phosphate powder mass;
m 2 -watchThe mass of the surfactant aqueous solution;
m 3 -lithium iron phosphate filtrate sampling amount;
m 4 -diluent mass;
(8) Repeating the steps (1) - (7) twice to obtain parallel test data M 2 、M 3 。
Example 2
The method for testing the iron ion content in the solution to be tested by adopting the inductively coupled plasma emission spectrometry comprises the following steps of:
(1) Weighing about 0.1g of linear sodium alkylbenzenesulfonate surfactant in a 250ml beaker, adding 200ml of pure water, and uniformly stirring to obtain a surfactant aqueous solution A with the mass percentage concentration of 0.05%;
(2) Accurately weighing the mass of m 1 Lithium iron phosphate powder of m 2 Is added to the aqueous surfactant solution A of (a),
(3) Will have a mass of m 1 The adding mass of the lithium iron phosphate powder is m 2 Is added to the aqueous solution of the surfactant to obtain slurry B
(4) Ultrasonically dispersing the obtained slurry B for 10min;
(5) Placing the solution after standing in a high-speed centrifuge, centrifuging at 5000rpm for 10min, collecting supernatant, and filtering to obtain filtrate with accurate weight of m 3 Diluting the filtrate with 2wt% dilute nitric acid water solution to obtain weight m 4 Is diluted with a diluent of (2)
(6) Testing the content m of iron ions in the solution to be tested by adopting an inductive coupling plasma emission spectrometry
(7) And (3) calculating an iron ion dissolution content result:
measuring the content of ferric ions in the lithium iron phosphate dissolved solution by an m-inductively coupled plasma emission spectrometry;
m 1 -lithium iron phosphate powder mass;
m 2 -the mass of the aqueous surfactant solution;
m 3 -lithium iron phosphate filtrate sampling amount;
m 4 -total mass of diluent.
(8) Repeating the steps (1) - (7) twice to obtain parallel test data M 2 、M 3 。
Example 3
In this example, the iron ion content in the solution to be measured was measured by a microcomputer photoelectron colorimetric detection method, and the amount of the linear sodium alkylbenzenesulfonate surfactant in this example was 0.06g, to prepare an aqueous surfactant solution with a mass percentage concentration of 0.03%, and other steps and parameters were the same as in example 1.
Example 4
The embodiment adopts a microcomputer photoelectron colorimetric detection method to test the content of iron ions in the solution to be tested,
the amount of the linear sodium alkylbenzenesulfonate surfactant used in this example was 0.14g, and an aqueous surfactant solution having a mass percent concentration of 0.07% was obtained, and the other steps and parameters were the same as those in example 1.
Example 5
The ultrasonic dispersion time of this example was 15min, and the other steps and parameters were the same as in example 1.
Example 6
The ultrasonic dispersion time of this example was 20min, and the other steps and parameters were the same as in example 1.
Example 7
The ultrasonic dispersion time of this example was 25min, and the other steps and parameters were the same as in example 1.
Comparative example 1
The amount of the linear sodium alkylbenzenesulfonate surfactant used in this comparative example was 0.04g, and an aqueous surfactant solution having a mass percent concentration of 0.02% was obtained, and the other steps and parameters were the same as those in example 1.
Comparative example 2
The comparative example does not use a surfactant to soak lithium iron phosphate powder, and replaces the powder with pure water, and the specific method is as follows:
(1) Accurately weigh the weight of m 1 Lithium iron phosphate powder and weight of m 2 Pure water is used for the treatment of the skin,
(2) Adding lithium iron phosphate powder into pure water to obtain slurry,
(3) The slurry was allowed to stand for 4 hours,
(4) Placing the slurry into a high-speed centrifuge, centrifuging at 5000rpm for 10min, collecting supernatant, filtering to obtain filtrate, and accurately weighing m 3 A filtrate; diluting with 2wt% dilute nitric acid water solution to weight m 4 Dilution liquid
(5) Method for testing iron ion content m in diluent by microcomputer photoelectron colorimetric detection method
(6) And (3) calculating an iron ion dissolution content result:
measuring the content of iron ions in the lithium iron phosphate dissolved solution by an m-microcomputer photoelectron colorimetric detection method;
m 1 -lithium iron phosphate powder mass;
m 2 -pure water quality;
m 3 -lithium iron phosphate filtrate sampling amount;
m 4 -diluent mass;
(7) Repeating the steps (1) - (6) twice to obtain parallel test data M 2 、M 3 。
M 1 The raw data are shown in table 1:
table 1M 1 Original data table
M 2 The raw data are shown in table 2:
table 2M 2 Original data table
| m | m 1 | m 2 | m 3 | m 4 | |
| Example 1 | 0.0124 | 5.0024 | 50.1254 | 1.0058 | 20.2323 |
| Example 2 | 0.0123 | 4.9995 | 50.2312 | 1.0056 | 20.3003 |
| Example 3 | 0.0122 | 4.9992 | 50.2215 | 1.0045 | 20.4811 |
| Example 4 | 0.0124 | 5.0015 | 50.0612 | 1.0052 | 20.2413 |
| Example 5 | 0.0125 | 5.0014 | 50.0378 | 1.0041 | 20.0642 |
| Example 6 | 0.0125 | 5.0120 | 50.0453 | 1.0012 | 20.0456 |
| Example 7 | 0.0124 | 5.0024 | 50.2312 | 1.0048 | 20.1665 |
| Comparative example 1 | 0.0120 | 5.1235 | 50.4215 | 1.0042 | 20.3546 |
| Comparative example 2 | 0.0117 | 5.0041 | 50.4215 | 1.0047 | 20.4571 |
M 3 The raw data are shown in table 3:
table 3M 3 Original data table
The results of the iron ion elution rates obtained by calculation from the raw data of tables 1 to 3 are shown in Table 4.
Table 4 calculation results table
As can be seen from the results of Table 4, by controlling the amount of the surface active agent to be within a proper range, the RSD values of the test results of the parallel tests of each of examples 1 to 7 were all less than 0.0006%, indicating that the uniformity of the test results of the method of the present invention was good. In addition, the dispersion time of the invention can be controlled to be 10-60 min, thus greatly improving the test efficiency.
The amount of the surfactant added in comparative example 1 was unsuitable, fluctuation of the dissolution rate of iron ions was large, consistency of the detection result was poor, and the overall level of the detection result was low.
Comparative example 2 was dissolved in iron ions without adding a surfactant by a long-term standing method, and the consistency of the detection results was poor, and the test time was long and the detection efficiency was low.
Regarding the effect of the ultrasonic dispersion time on the measurement results, it can be seen from the measurement results of examples 1, 5, 6, and 7 that iron ions were completely eluted when ultrasonic dispersion was performed for 10 minutes in a 0.05% A solution.
From the results of the embodiment 1 and the embodiment 2, the result of the microcomputer photoelectron colorimetric detection method for testing the iron ion content in the solution to be tested is equivalent to that of the inductance coupling plasma emission spectrometry, and the microcomputer photoelectron colorimetric detection method for testing the iron ion content in the solution to be tested is simple and quick to operate, so that the problems that an ICP-OES instrument is expensive and complex to operate, ICP professional training is not needed for operators, and the detection cost is greatly reduced.
In conclusion, the surfactant is added, so that the iron ions in the lithium iron phosphate can be rapidly dissolved out and uniformly dispersed, the testing efficiency and consistency are improved, and the problem that the testing result consistency is poor due to long stacking and dissolution time of directly standing lithium iron phosphate powder, poor testing result consistency or abnormal dissolution of iron ions caused by destroying the particle structure of the lithium iron phosphate by long-time strong stirring due to reduction of the iron ion dissolution time is solved.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. A method for determining the dissolution rate of iron ions in a lithium iron phosphate material, comprising the steps of:
s1: mixing lithium iron phosphate material, surfactant and water, and uniformly dispersing to obtain a mixed solution;
s2: carrying out solid-liquid separation on the mixed solution, taking filtrate, and diluting the filtrate by using a diluent to obtain a diluent;
s3: determining the content of iron ions in the diluent to obtain the dissolution rate of the iron ions;
the mass ratio of the surfactant to water in the mixed solution of S1 is (0.03-0.07): 100.
2. The method of claim 1, wherein the surfactant in S1 is one or more of an anionic surfactant or a nonionic surfactant.
3. The method according to claim 2, wherein the surfactant in S1 is one or more of sodium linear alkylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium secondary alkyl sulfonate or polysorbate-80.
4. The method of claim 1, wherein the mass ratio of the lithium iron phosphate material to the surfactant in the mixed solution of S1 is 1 (0.003-0.007).
5. The method of claim 1, wherein the lithium iron phosphate material in S1 has a particle size Dv50 of 0.5 μιη to 20 μιη.
6. The method according to claim 1, wherein the dispersing time in S1 is 10min to 60min.
7. The method according to claim 1, wherein the diluent in S2 is one or more of a dilute nitric acid aqueous solution, a dilute hydrochloric acid aqueous solution and a dilute sulfuric acid aqueous solution, and the mass percentage concentration of the diluent is 2-5%.
8. The method according to claim 1, wherein the mass ratio of the filtrate to the diluent in S2 is 1 (20-50).
9. The method according to claim 1, wherein the solid-liquid separation in S2 is performed by centrifugation and filtration.
10. The method of claim 1, wherein the iron ion content of the diluent is determined in S3 using microcomputer optoelectronics colorimetric detection or inductively coupled plasma emission spectrometry.
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