CN117740707A - Method for measuring carbon and sulfur content of lithium iron phosphate - Google Patents
Method for measuring carbon and sulfur content of lithium iron phosphate Download PDFInfo
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- CN117740707A CN117740707A CN202311755326.0A CN202311755326A CN117740707A CN 117740707 A CN117740707 A CN 117740707A CN 202311755326 A CN202311755326 A CN 202311755326A CN 117740707 A CN117740707 A CN 117740707A
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- carbon
- fluxing agent
- sulfur
- iron phosphate
- lithium iron
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- 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 97
- 238000000034 method Methods 0.000 title claims abstract description 45
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 45
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 42
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 37
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 239000011593 sulfur Substances 0.000 title claims abstract description 35
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 156
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 140
- YQCIWBXEVYWRCW-UHFFFAOYSA-N methane;sulfane Chemical compound C.S YQCIWBXEVYWRCW-UHFFFAOYSA-N 0.000 claims abstract description 119
- 229910052742 iron Inorganic materials 0.000 claims abstract description 70
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 65
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 65
- 239000010937 tungsten Substances 0.000 claims abstract description 65
- 238000005259 measurement Methods 0.000 claims abstract description 36
- 239000000126 substance Substances 0.000 claims description 74
- 238000012360 testing method Methods 0.000 claims description 27
- 238000004458 analytical method Methods 0.000 claims description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 21
- 229910052760 oxygen Inorganic materials 0.000 claims description 21
- 239000001301 oxygen Substances 0.000 claims description 21
- 238000005303 weighing Methods 0.000 claims description 20
- 239000000919 ceramic Substances 0.000 claims description 15
- 230000004907 flux Effects 0.000 claims description 9
- 238000001514 detection method Methods 0.000 claims description 8
- 229910000975 Carbon steel Inorganic materials 0.000 claims description 5
- 239000010962 carbon steel Substances 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 230000000052 comparative effect Effects 0.000 description 25
- 238000012986 modification Methods 0.000 description 18
- 230000004048 modification Effects 0.000 description 18
- 239000000463 material Substances 0.000 description 7
- 238000010521 absorption reaction Methods 0.000 description 6
- 238000002485 combustion reaction Methods 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000004448 titration Methods 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000006184 cosolvent Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000011573 trace mineral Substances 0.000 description 1
- 235000013619 trace mineral Nutrition 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 And Analyzing Materials By Characteristic Methods (AREA)
Abstract
The invention discloses a method for measuring carbon-sulfur content of lithium iron phosphate, which adopts an infrared carbon-sulfur analyzer to measure carbon-sulfur content of lithium iron phosphate, wherein in the process of measuring a lithium iron phosphate sample, the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively a tungsten fluxing agent, a pure iron fluxing agent and a lithium iron phosphate sample, the adding amount of the tungsten fluxing agent is 1.5-2.0g, the adding amount of the pure iron fluxing agent is 0.3-0.4g, and the adding amount of the lithium iron phosphate sample is 0.05-0.15g; according to the invention, the carbon and sulfur content of the lithium iron phosphate is tested by adopting a mode that the upper layer, the middle layer and the lower layer are tungsten fluxing agents, pure iron fluxing agents and lithium iron phosphate, the fluxing agents are added in the middle layer and the upper layer, and the addition sequence and the addition amount of the fluxing agents are changed, so that the lithium iron phosphate sample is combusted more fully, the release of carbon and sulfur is more complete, and the method has the characteristics of simplicity and rapidness in operation and high accuracy, and stable carbon and sulfur content measurement data can be obtained.
Description
Technical Field
The invention belongs to the technical field of lithium battery anode materials, and particularly relates to a method for measuring carbon sulfur content of lithium iron phosphate.
Background
The lithium iron phosphate is a common positive electrode material, and is characterized by large discharge specific capacity, low price, long service life, good safety performance, no toxicity and no environmental pollution, and is widely applied to lithium ion batteries. The lithium iron phosphate contains trace elements such as lithium, iron, phosphorus, oxygen, carbon and the like, and the difference of carbon and sulfur contents in the lithium iron phosphate can have great influence on the performance of the material. Experiments show that when the carbon content in the lithium iron phosphate material is low, fe in the material 2+ The oxidized proportion is large, so that the purity of the sample is reduced, and the charging resistance is overlarge due to low electronic conductivity; however, when the carbon content in the lithium iron phosphate material is too high, the tap density of the material is affected, so that the gram capacity of the material is low; when the sulfur content reaches a certain degree, the influence on the particle morphology, discharge capacity and cycle performance of the lithium iron phosphate is gradually obvious. Therefore, the carbon and sulfur content of the lithium iron phosphate is necessary to be tested.
The current carbon-sulfur detection method comprises a conductivity method, a capacity method, a titration method, a weight method and the like, but the detection method has complex operation steps, and the titration method and the capacity method also need to consume standard solution and reagent, so that the operation is inconvenient. The most commonly used method for detecting carbon and sulfur is infrared absorption. CO is used in infrared absorption method 2 SO and SO 2 Having strong characteristic absorption bands at 4.26 μm and 7.4 μm, respectively, and analyzing CO by measuring gas absorption intensity 2 SO and SO 2 And the content is used for indirectly determining the percentage content of carbon and sulfur in the measured sample. The infrared absorption method needs to add fluxing agent, which can reduce the melting point of the sample, and simultaneously, the fluxing agent oxidizes a large amount of heat energy released by combustion to increase the furnace temperature, thereby being beneficial to the combustion of the sample and leading the carbon and sulfur in the sample to be completely released.
In the prior art, a high-frequency infrared absorption method is generally adopted for testing the carbon-sulfur content, the upper layer, the middle layer and the lower layer of an infrared carbon-sulfur instrument are respectively tungsten fluxing agents-lithium iron phosphate-pure iron fluxing agents, and the addition sequence of the cosolvent is adopted for testing, so that the problems of insufficient burning of a sample and incomplete release of carbon and sulfur exist, and the tested carbon-sulfur content results are lower and the accuracy is unstable.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for measuring the carbon sulfur content of lithium iron phosphate, which ensures that a lithium iron phosphate sample burns more fully and releases carbon sulfur more completely by changing the addition sequence and the addition amount of a fluxing agent, thereby ensuring that better accuracy and stability are achieved in the subsequent detection.
The aim of the invention can be achieved by the following technical scheme:
in the process of measuring the lithium iron phosphate sample, an infrared carbon-sulfur analyzer is adopted to measure the carbon-sulfur content of the lithium iron phosphate, wherein the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively a tungsten fluxing agent, a pure iron fluxing agent and a lithium iron phosphate sample, the adding amount of the tungsten fluxing agent is 1.5-2.0g, the adding amount of the pure iron fluxing agent is 0.3-0.4g, and the adding amount of the lithium iron phosphate sample is 0.05-0.15g.
Further, the method specifically comprises the following steps:
s1: preparing a spare part for measurement, wherein the spare part comprises a standard substance, a pure iron fluxing agent and a tungsten fluxing agent; the standard substance is carbon steel: c=1.202%, s=0.006%; pure iron fluxing agent: c is less than 0.001%, S is less than 0.001%; tungsten flux: w is more than or equal to 99.95%, C is less than or equal to 0.0005%, and S is less than or equal to 0.0005%;
s2: placing the lithium iron phosphate sample in a drying oven at 140-150 ℃ for baking for 1-3 hours, and cooling to room temperature for standby;
s3: setting analysis power, comparison level, analysis time, oxygen pressure and oxygen flow of an infrared carbon-sulfur analyzer;
s4: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the standard substance at least once according to the working condition selected by the infrared carbon-sulfur analyzer to obtain a carbon-sulfur standard value of the standard substance;
s5: inputting a carbon-sulfur standard value corresponding to a standard substance, wherein the test result is expressed in percentage, selecting 'daily calibration', selecting the tested standard substance result, and automatically correcting and storing coefficients by an infrared carbon-sulfur analyzer;
s6: repeating the test of the standard substance at least once, and returning to the step S4 until the test result meets the carbon-sulfur standard value range of the standard substance if the result does not meet the carbon-sulfur standard value range of the standard substance;
s7: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of lithium iron phosphate sample, placing the sample into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent into the sample by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the lithium iron phosphate according to the working conditions selected by the infrared carbon-sulfur analyzer;
s8: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, measuring the carbon-sulfur content of the standard substance at least once, and judging whether the test result meets the carbon-sulfur standard value range;
s9: and outputting the detection data of the carbon and sulfur content of the lithium iron phosphate sample.
Further, the analysis power is 1.5kw-3.0kw, the comparison level is 2%, the analysis time is 30-50s, the oxygen pressure is 0.05-0.08MPa, and the oxygen flow is 2.8L/min.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a method for measuring carbon-sulfur content of lithium iron phosphate, which adopts a mode that an upper layer, a middle layer and a lower layer are tungsten fluxing agent-pure iron fluxing agent-lithium iron phosphate to test the carbon-sulfur content of lithium iron phosphate, wherein the fluxing agent is added in the middle layer and the upper layer, and the tungsten fluxing agent in the upper layer is oxidized to release a large amount of heat, and an oxidation product WO thereof 3 Increases the diffusion rate of carbon and sulfur, fully oxidizes the carbon and sulfur in the sample, and WO 3 After leaving the molten pool, the mixture is converted into a solid phase to be covered on a pipeline, so that the adsorption of carbon and sulfur by the pipeline can be prevented; the pure iron fluxing agent mainly plays roles of magnetic conduction and heat release, the pure iron fluxing agent is arranged on the middle layer to cover the lithium iron phosphate sample, and the heat released by the fluxing agent can leadThe sample burns more fully; since the IR spectrum is obtained by measuring SO 2 And CO 2 Indirectly determining the carbon-sulfur content of the sample, thereby rapidly increasing the temperature and controlling the oxygen content to facilitate SO 2 And CO 2 The release of the flux is favorable for improving the precision of the instrument, and the effect of improving the combustion temperature of the sample is poor due to the small flux, so that the sample is incompletely combusted; the fluxing agent is large in dosage, is easy to splash and corrode the crucible, is easy to generate dust, and is unstable in test data, SO that the invention can effectively improve the combustion temperature by reasonably controlling the addition amount of the fluxing agent, and enables SO 2 And CO 2 Is more stable.
2. According to the method for measuring the carbon and sulfur content of the lithium iron phosphate, disclosed by the invention, in the sample weighing process, the weighing step is directly replaced by the small ladle with fixed weight, and when the lithium iron phosphate sample, the pure iron fluxing agent and the tungsten fluxing agent are sequentially weighed, the condition that a sample is discarded due to a large weight error during sample weighing can be avoided, the sample weighing times are reduced, and the weighing step can be completed quickly.
3. According to the method for measuring the carbon and sulfur content of the lithium iron phosphate, in the step S3, the analysis power is 1.5kw-3.0kw, the comparison level is 2%, the analysis time is 30-50S, the oxygen pressure is 0.05-0.08MPa, and the oxygen flow is 2.8L/min, and the accuracy and stability of the analysis result of the infrared carbon and sulfur analyzer can be further improved, the analysis error is reduced, and the analysis result is more accurate and reliable by controlling the analysis power, the comparison level, the analysis time, the oxygen pressure and the oxygen flow of the infrared carbon and sulfur analyzer.
Drawings
FIG. 1 is a flow chart of a method for measuring the carbon-sulfur content of lithium iron phosphate.
Detailed Description
The invention is further described below in connection with the preferred embodiments and with reference to fig. 1, and neither the endpoints of the ranges disclosed in the invention nor any value are limited to the precise range or value, and such range or value should be understood to include values near the range or value; for a range of values, one or more new ranges of values can be obtained in combination with each other between the endpoints of each range, between the endpoints of each range and the individual point values, and between the individual point values, and are to be considered as specifically disclosed herein; materials, reagents and the like used in the following examples are commercially available unless otherwise specified; the experimental methods in the following examples are conventional methods unless otherwise specified.
Example 1
In the method for measuring the carbon sulfur content of lithium iron phosphate, an infrared carbon sulfur analyzer is adopted to measure the carbon sulfur content of lithium iron phosphate, in the process of measuring a lithium iron phosphate sample 1, the upper layer, the middle layer and the lower layer of the infrared carbon sulfur analyzer are respectively a tungsten fluxing agent, a pure iron fluxing agent and a lithium iron phosphate sample 1, the adding amount of the tungsten fluxing agent is 1.75g, the adding amount of the pure iron fluxing agent is 0.35g, and the adding amount of the lithium iron phosphate sample 1 is 0.05g.
Further, the method specifically comprises the following steps:
s1: preparing a spare part for measurement, wherein the spare part comprises a standard substance, a pure iron fluxing agent and a tungsten fluxing agent; the standard substance is carbon steel: c=1.202%, s=0.006%; pure iron fluxing agent: c is less than 0.001%, S is less than 0.001%; tungsten flux: w is more than or equal to 99.95%, C is less than or equal to 0.0005%, and S is less than or equal to 0.0005%;
s2: placing the lithium iron phosphate sample 1 in a drying oven at 140 ℃ for 2h, and cooling to room temperature for standby;
s3: setting the analysis power of the infrared carbon-sulfur analyzer to be 1.5kw, the comparison level to be 2%, the analysis time to be 50s, the oxygen pressure to be 0.05MPa and the oxygen flow to be 2.8L/min;
s4: placing a ceramic crucible on an analytical balance, weighing 0.05g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.35g of pure iron fluxing agent and 1.75g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the standard substance once according to the working condition selected by the infrared carbon-sulfur analyzer to obtain a carbon-sulfur standard value of the standard substance;
s5: inputting a carbon-sulfur standard value corresponding to a standard substance, wherein the test result is expressed in percentage, selecting 'daily calibration', selecting the tested standard substance result, and automatically correcting and storing coefficients by an infrared carbon-sulfur analyzer;
s6: repeating the test of the standard substance once, and returning to the step S4 until the test result meets the carbon-sulfur standard value range of the standard substance if the result does not meet the standard value range of the standard substance;
s7: placing a ceramic crucible on an analytical balance, weighing 0.05g of a lithium iron phosphate sample 1, placing the sample into an infrared carbon-sulfur analyzer, sequentially adding 0.35g of pure iron fluxing agent and 1.75g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the lithium iron phosphate according to the working conditions selected by the infrared carbon-sulfur analyzer;
s8: placing a ceramic crucible on an analytical balance, weighing 0.05g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.35g of pure iron fluxing agent and 1.75g of tungsten fluxing agent by using a special fluxing agent small ladle, measuring the carbon-sulfur content of the standard substance once, and judging whether the test result meets the carbon-sulfur standard value range;
s9: and outputting the detection data of the carbon and sulfur content of the lithium iron phosphate sample 1, wherein the measurement result is shown in table 1.
Example 2
The method for measuring the carbon-sulfur content of the lithium iron phosphate comprises the steps of measuring the carbon-sulfur content of the lithium iron phosphate by adopting an infrared carbon-sulfur analyzer, wherein in the process of measuring the lithium iron phosphate sample 1, the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively tungsten fluxing agent, pure iron fluxing agent and lithium iron phosphate sample 1, the method for measuring the carbon-sulfur content of the lithium iron phosphate by adopting the infrared carbon-sulfur analyzer, in the process of measuring the lithium iron phosphate sample 1, the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively tungsten fluxing agent, pure iron fluxing agent and lithium iron phosphate sample 1, the adding amount of the tungsten fluxing agent is 1.5g, the adding amount of the pure iron fluxing agent is 0.3g, and the adding amount of the lithium iron phosphate sample 1 is 0.1g.
Further, the method specifically comprises the following steps:
s1: preparing a spare part for measurement, wherein the spare part comprises a standard substance, a pure iron fluxing agent and a tungsten fluxing agent; the standard substance is carbon steel: c=1.202%, s=0.006%; pure iron fluxing agent: c is less than 0.001%, S is less than 0.001%; tungsten flux: w is more than or equal to 99.95%, C is less than or equal to 0.0005%, and S is less than or equal to 0.0005%;
s2: placing the lithium iron phosphate sample 1 in a 145 ℃ drying oven for baking for 1.5 hours, and cooling to room temperature for standby;
s3: setting the analysis power of the infrared carbon-sulfur analyzer to be 2.0kw, the comparison level to be 2%, the analysis time to be 40s, the oxygen pressure to be 0.06MPa and the oxygen flow to be 2.8L/min;
s4: placing a ceramic crucible on an analytical balance, weighing 0.1g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3g of pure iron fluxing agent and 1.5g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the standard substance twice according to the working condition selected by the infrared carbon-sulfur analyzer to obtain a carbon-sulfur standard value of the standard substance;
s5: inputting a carbon-sulfur standard value corresponding to a standard substance, wherein the test result is expressed in percentage, selecting 'daily calibration', selecting the tested standard substance result, and automatically correcting and storing coefficients by an infrared carbon-sulfur analyzer;
s6: repeating the test of the standard substance twice, and returning to the step S4 until the test result meets the carbon-sulfur standard value range of the standard substance if the result does not meet the carbon-sulfur standard value range of the standard substance;
s7: placing a ceramic crucible on an analytical balance, weighing 0.1g of lithium iron phosphate sample 1, placing the sample into an infrared carbon-sulfur analyzer, sequentially adding 0.3g of pure iron fluxing agent and 1.5g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the lithium iron phosphate according to the working conditions selected by the infrared carbon-sulfur analyzer;
s8: placing a ceramic crucible on an analytical balance, weighing 0.1g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3g of pure iron fluxing agent and 1.5g of tungsten fluxing agent by using a special fluxing agent small ladle, measuring the carbon-sulfur content of the standard substance twice, and judging whether the test result meets the carbon-sulfur standard value range;
s9: and outputting the detection data of the carbon and sulfur content of the lithium iron phosphate sample 1, wherein the measurement result is shown in table 1.
Example 3
The method for measuring the carbon-sulfur content of the lithium iron phosphate comprises the steps of measuring the carbon-sulfur content of the lithium iron phosphate by adopting an infrared carbon-sulfur analyzer, wherein in the process of measuring the lithium iron phosphate sample 1, the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively tungsten fluxing agent, pure iron fluxing agent and lithium iron phosphate sample 1, the method for measuring the carbon-sulfur content of the lithium iron phosphate by adopting the infrared carbon-sulfur analyzer, in the process of measuring the lithium iron phosphate sample 1, the upper layer, the middle layer and the lower layer of the infrared carbon-sulfur analyzer are respectively tungsten fluxing agent, pure iron fluxing agent and lithium iron phosphate sample 1, the adding amount of the tungsten fluxing agent is 2.0g, the adding amount of the pure iron fluxing agent is 0.4g, and the adding amount of the lithium iron phosphate sample 1 is 0.15g.
Further, the method specifically comprises the following steps:
s1: preparing a spare part for measurement, wherein the spare part comprises a standard substance, a pure iron fluxing agent and a tungsten fluxing agent; the standard substance is carbon steel: c=1.202%, s=0.006%; pure iron fluxing agent: c is less than 0.001%, S is less than 0.001%; tungsten flux: w is more than or equal to 99.95%, C is less than or equal to 0.0005%, and S is less than or equal to 0.0005%;
s2: placing the lithium iron phosphate sample 1 in a drying oven at 150 ℃ for baking for 2 hours, and cooling to room temperature for standby;
s3: setting the analysis power of the infrared carbon-sulfur analyzer to be 3.0kw, the comparison level to be 2%, the analysis time to be 30s, the oxygen pressure to be 0.08MPa and the oxygen flow to be 2.8L/min;
s4: placing a ceramic crucible on an analytical balance, weighing 0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.4g of pure iron fluxing agent and 2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the standard substance three times according to the working condition selected by the infrared carbon-sulfur analyzer to obtain a carbon-sulfur standard value of the standard substance;
s5: inputting a carbon-sulfur standard value corresponding to a standard substance, wherein the test result is expressed in percentage, selecting 'daily calibration', selecting the tested standard substance result, and automatically correcting and storing coefficients by an infrared carbon-sulfur analyzer;
s6: repeating the test of the standard substance for three times, and returning to the step S4 until the test result meets the carbon-sulfur standard value range of the standard substance if the result does not meet the carbon-sulfur standard value range of the standard substance;
s7: placing a ceramic crucible on an analytical balance, weighing 0.15g of a lithium iron phosphate sample 1, placing the sample into an infrared carbon-sulfur analyzer, sequentially adding 0.4g of pure iron fluxing agent and 2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the lithium iron phosphate according to the working conditions selected by the infrared carbon-sulfur analyzer;
s8: placing a ceramic crucible on an analytical balance, weighing 0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.4g of pure iron fluxing agent and 2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, measuring the carbon-sulfur content of the standard substance for three times, and judging whether the test result meets the carbon-sulfur standard value range;
s9: and outputting the detection data of the carbon and sulfur content of the lithium iron phosphate sample 1, wherein the measurement result is shown in table 1.
Table 1 statistics of measurement results
Comparative example 1
Substantially the same as in example 2, but with the following modifications:
in the steps S4 and S8, 0.35g of pure iron fluxing agent is added by a special fluxing agent small ladle, then 0.1g of standard substance is weighed, and 1.75g of tungsten fluxing agent is added by the special fluxing agent small ladle;
in the step S7, 0.35g of pure iron fluxing agent is added by a special fluxing agent small ladle, then 0.1g of lithium iron phosphate sample 1 is weighed, and 1.75g of tungsten fluxing agent is added by the special fluxing agent small ladle;
the measurement results are shown in Table 2.
Table 2 comparison of the results of the measurements of example 2 and comparative example 1
| Category(s) | Sample size (g) | Pure iron fluxing agent (g) | Tungsten fluxing agent (g) | Measurement of C (%) | S measurement value (%) |
| Example 2 | 0.1 | 0.3 | 1.5 | 1.4013 | 0.0225 |
| Comparative example 1 | 0.1 | 0.3 | 1.5 | 1.3654 | 0.0218 |
As can be seen from table 2, according to the method for measuring the carbon and sulfur content of lithium iron phosphate provided by the invention, the addition sequence of the fluxing agent is changed, so that the lithium iron phosphate sample 1 can be combusted more fully, and the release of carbon and sulfur can be more complete.
Comparative example 2
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.1g, the addition amount of the tungsten fluxing agent was 1g, and the measurement results are shown in Table 3.
Comparative example 3
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.1g, the addition amount of the tungsten fluxing agent was 1.5g, and the measurement results are shown in Table 3.
Comparative example 4
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.1g, the addition amount of the tungsten fluxing agent was 2g, and the measurement results are shown in Table 3.
Comparative example 5
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.2g, the addition amount of the tungsten fluxing agent was 1g, and the measurement results are shown in Table 3.
Comparative example 6
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.2g, the addition amount of the tungsten fluxing agent was 1.5g, and the measurement results are shown in Table 3.
Comparative example 7
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.2g, the addition amount of the tungsten fluxing agent was 2g, and the measurement results are shown in Table 3.
Comparative example 8
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.3g, the addition amount of the tungsten fluxing agent was 1g, and the measurement results are shown in Table 3.
Comparative example 9
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.3g, the addition amount of the tungsten fluxing agent was 2g, and the measurement results are shown in Table 3.
Comparative example 10
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.4g, the addition amount of the tungsten fluxing agent was 1g, and the measurement results are shown in Table 3.
Comparative example 11
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.4g, the addition amount of the tungsten fluxing agent was 1.5g, and the measurement results are shown in Table 3.
Comparative example 12
Substantially the same as in example 2, but with the following modifications:
in steps S4, S7 and S8, the addition amount of the pure iron fluxing agent was 0.4g, the addition amount of the tungsten fluxing agent was 2g, and the measurement results are shown in Table 3.
Table 3 comparison of the results of the measurements of example 2 and comparative examples 2-12
As can be seen from Table 3, according to the method for measuring the carbon and sulfur content of lithium iron phosphate provided by the invention, under the condition that the addition amount of the lithium iron phosphate sample 1 is constant, the addition amount of the pure iron fluxing agent is 0.3-0.4g, and the addition amount of the tungsten fluxing agent is 1.5-2.0g, so that the carbon and sulfur in the lithium iron phosphate sample 1 can be released more completely, and the measurement data is more stable.
Comparative example 13
Substantially the same as in example 2, but with the following modifications:
in step S7, the carbon-sulfur content of lithium iron phosphate was measured six times repeatedly, and the measurement results are shown in table 4.
Comparative example 14
Substantially the same as comparative example 13, but with the following modifications:
the lithium iron phosphate sample 1 in step S7 was replaced with the lithium iron phosphate sample 2, and the measurement results are shown in table 4.
Comparative example 15
Substantially the same as comparative example 13, but with the following modifications:
the lithium iron phosphate sample 1 in step S7 was replaced with the lithium iron phosphate sample 3, and the measurement results are shown in table 4.
Table 4 comparative examples 13-15 comparative tables of measurement results
As can be seen from Table 4, the relative standard deviation of the test results of each group of the method for measuring the carbon sulfur content of the lithium iron phosphate provided by the invention is less than 0.1%, which indicates that the method is good in precision.
Comparative example 16
Substantially the same as in example 2, but with the following modifications:
the lithium iron phosphate sample 1 in step S7 was replaced with a standard substance, and the measurement was repeated three times, and the measurement results are shown in table 5.
Comparative example 17
Substantially the same as in example 2, but with the following modifications:
replacing the lithium iron phosphate sample 1 in the step S7 with a standard substance;
in the steps S4 and S8, 0.35g of pure iron fluxing agent is added by a special fluxing agent small ladle, then 0.1g of standard substance is weighed, and 1.75g of tungsten fluxing agent is added by the special fluxing agent small ladle;
in the step S7, 0.35g of pure iron fluxing agent is added by a special fluxing agent small ladle, then 0.1g of lithium iron phosphate sample is weighed, and 1.75g of tungsten fluxing agent is added by the special fluxing agent small ladle;
and the measurement was repeated three times, and the measurement results are shown in Table 5.
Table 5 comparison of the results of the measurements of example 2 and comparative examples 16-17
As can be seen from Table 5, the method for measuring the carbon and sulfur content of lithium iron phosphate provided by the invention adopts a tungsten fluxing agent-pure iron fluxing agent-standard steel sample mode for measuring the high-frequency infrared carbon and sulfur at the upper, middle and lower layers, and the measured value is very close to the standard value, so that the accuracy of the method is good.
The invention solves the problems of insufficient burning of samples and incomplete release of carbon and sulfur in the prior art by adopting a mode of adopting tungsten fluxing agent-lithium iron phosphate-pure iron fluxing agent as an upper layer, a middle layer and a lower layer to carry out the carbon and sulfur content test of lithium iron phosphate, adopting a mode of adopting tungsten fluxing agent-pure iron fluxing agent-lithium iron phosphate as an upper layer, adding fluxing agent into the middle layer and the upper layer, oxidizing the tungsten fluxing agent at the upper layer to release a large amount of heat, and oxidizing the product WO 3 Increases the diffusion rate of carbon and sulfur, fully oxidizes the carbon and sulfur in the sample, and WO 3 After leaving the molten pool, the mixture is converted into a solid phase to be covered on a pipeline, so that the adsorption of carbon and sulfur by the pipeline can be prevented; the pure iron fluxing agent mainly plays roles of magnetic conduction and heat release, the pure iron fluxing agent is placed on the middle layer to cover the lithium iron phosphate sample, and the heat released by the fluxing agent can enable the sample to burn more fully; since the IR spectrum is obtained by measuring SO 2 And CO 2 Indirectly determining the carbon-sulfur content of the sample, thereby rapidly increasing the temperature and controlling the oxygen content to facilitate SO 2 And CO 2 The release of the flux is favorable for improving the precision of the instrument, and the effect of improving the combustion temperature of the sample is poor due to the small flux, so that the sample is incompletely combusted; the fluxing agent is large in dosage, is easy to splash and corrode the crucible, is easy to generate dust, and is unstable in test data, SO that the invention can effectively improve the combustion temperature by reasonably controlling the addition amount of the fluxing agent, and enables SO 2 And CO 2 Is more stable.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and improvements could be made by those skilled in the art without departing from the inventive concept, which falls within the scope of the present invention.
Claims (3)
1. The method for measuring the carbon sulfur content of the lithium iron phosphate is characterized in that in the process of measuring the lithium iron phosphate sample, an infrared carbon sulfur analyzer is adopted to measure the carbon sulfur content of the lithium iron phosphate, wherein the upper layer, the middle layer and the lower layer of the infrared carbon sulfur analyzer are respectively a tungsten fluxing agent, a pure iron fluxing agent and a lithium iron phosphate sample, the adding amount of the tungsten fluxing agent is 1.5-2.0g, the adding amount of the pure iron fluxing agent is 0.3-0.4g, and the adding amount of the lithium iron phosphate sample is 0.05-0.15g.
2. The method for measuring the carbon sulfur content of lithium iron phosphate according to claim 1, which is characterized by comprising the following steps:
s1: preparing a spare part for measurement, wherein the spare part comprises a standard substance, a pure iron fluxing agent and a tungsten fluxing agent; the standard substance is carbon steel: c=1.202%, s=0.006%; pure iron fluxing agent: c is less than 0.001%, S is less than 0.001%; tungsten flux: w is more than or equal to 99.95%, C is less than or equal to 0.0005%, and S is less than or equal to 0.0005%;
s2: placing the lithium iron phosphate sample in a drying oven at 140-150 ℃ for baking for 1-3 hours, and cooling to room temperature for standby;
s3: setting analysis power, comparison level, analysis time, oxygen pressure and oxygen flow of an infrared carbon-sulfur analyzer;
s4: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the standard substance at least once according to the working condition selected by the infrared carbon-sulfur analyzer to obtain a carbon-sulfur standard value of the standard substance;
s5: inputting a carbon-sulfur standard value corresponding to a standard substance, wherein the test result is expressed in percentage, selecting 'daily calibration', selecting the tested standard substance result, and automatically correcting and storing coefficients by an infrared carbon-sulfur analyzer;
s6: repeating the test of the standard substance at least once, and returning to the step S4 until the test result meets the carbon-sulfur standard value range of the standard substance if the result does not meet the carbon-sulfur standard value range of the standard substance;
s7: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of lithium iron phosphate sample, placing the sample into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent into the sample by using a special fluxing agent small ladle, and measuring the carbon-sulfur content of the lithium iron phosphate according to the working conditions selected by the infrared carbon-sulfur analyzer;
s8: placing a ceramic crucible on an analytical balance, weighing 0.05-0.15g of standard substance, placing the standard substance into an infrared carbon-sulfur analyzer, sequentially adding 0.3-0.4g of pure iron fluxing agent and 1.5-2.0g of tungsten fluxing agent by using a special fluxing agent small ladle, measuring the carbon-sulfur content of the standard substance at least once, and judging whether the test result meets the carbon-sulfur standard value range;
s9: and outputting the detection data of the carbon and sulfur content of the lithium iron phosphate sample.
3. The method for measuring the carbon-sulfur content of lithium iron phosphate according to claim 2, wherein in the step S3, the analysis power is 1.5kw-3.0kw, the comparison level is 2%, the analysis time is 30-50S, the oxygen pressure is 0.05-0.08MPa, and the oxygen flow is 2.8L/min.
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