Method for detecting residual alkali on surface of battery positive electrode material

Abstract

The invention discloses a method for detecting residual alkali on the surface of a battery positive electrode material. The method comprises the following steps: preparing materials: preparing nitrogen, a heating device, condensing equipment, a positive electrode material, a solvent and a titration acid solution; according to the invention, nitrogen is introduced into the heating device and is used for replacing oxygen, and the heating device is used for heating the positive electrode material, so that residual alkali on the positive electrode material is separated from the positive electrode material in a gas volatilization manner; converting the gas from a gas state into a liquid through a condensing device to obtain a condensate with residual alkali; detecting the residual alkali amount through a traditional hydrochloric acid titration mode; by adopting the method, the cathode material does not need to contact with the solvent; the positive electrode material and the solvent are not subjected to oxidation and ion exchange reaction, and the positive electrode material cannot be put into use due to oxygen corrosion; the condition that the alkali value of the residual alkali content is increased due to the generation of the ion exchange reaction is avoided; the use stability of the positive electrode material is ensured, and the accurate value of residual alkali content detection is also ensured.

Description

Technical Field

[0001] The invention relates to the technical field of battery detection, and in particular to a method for detecting residual alkali on the surface of a battery positive electrode material. Background Art

[0002] ‌Residual alkali on the surface of positive electrode materials of batteries‌ refers to the alkaline substances attached to the surface of positive electrode materials, mainly including lithium hydroxide and lithium carbonate. These alkaline substances mainly exist in the form of hydroxide and carbonate. After testing, their amount is expressed as lithium carbonate content, which is the residual alkali‌.

[0003] If the residual alkali content of the battery positive electrode material is too high during the production process, it will cause slurry flocculation and increase gas production during the battery cycle, greatly reducing the safety performance of the battery. Therefore, how to detect the residual alkali content of the sodium-ion battery positive electrode material has always been a key issue that has plagued the sodium-ion battery preparation industry.

[0004] The traditional method for detecting residual alkali on the surface of positive electrode materials of batteries is to immerse the positive electrode materials of batteries in a solvent, and the solvent is mostly water to dissolve the residual alkali; then the residual alkali amount is determined by hydrochloric acid titration; although this method can meet the detection of residual alkali, the positive electrode materials will produce oxidation and ion exchange phenomena when they are immersed in the solvent and contacted with water in the solvent. In this case, the oxidation of the positive electrode materials will affect their stability, and the positive electrode materials cannot be put into use after the detection, resulting in waste; secondly, the ion exchange phenomenon caused by the contact of the positive electrode materials with water will cause the alkalinity value to be too high, so that the residual alkali on the surface of the material cannot be accurately determined in the later detection.

[0005] Therefore, a method for detecting residual alkali on the surface of battery positive electrode material is proposed to solve this problem. Summary of the invention

[0006] The purpose of the present invention is to provide a method for detecting residual alkali on the surface of a positive electrode material of a battery, which solves the problem that oxidation and ion exchange phenomena will occur when the positive electrode material is soaked in a solvent.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for detecting residual alkali on the surface of a positive electrode material of a battery, comprising the following steps: S1: Material preparation: nitrogen, heating device, condensation equipment, positive electrode material, solvent, titration acid solution; The nitrogen gas shall be introduced into the heating device; the air inlet of the condensing device shall be connected to the air outlet of the heating device; The positive electrode material is placed in a heating device and heated in a nitrogen environment at a temperature of 60-65°C; S2: Nitrogen is filled into the heating device, and the heating device heats the positive electrode material. Nitrogen has a low activity, which prevents the positive electrode material from reacting with oxygen in the air during the heating process; The positive electrode material is heated to 60-65°C by a heating device, and the residual alkali on the positive electrode material will produce volatile gas. After being produced, the volatile gas will enter the condensation device through the gas outlet of the heating device. The condensation device cools the volatile gas to convert it from gas to liquid, and finally obtains condensate. The residual alkali in the positive electrode material is volatilized in the form of gas after heating and the positive electrode material is stripped; S3: mixing the obtained condensate with a solvent (water) to obtain a solution to be measured; S4: According to the basic acid-base titration principle, add the corresponding indicator, titrate with standard hydrochloric acid solution, and calculate the residual content.

[0008] Preferably, in step 1, nitrogen must be introduced into the heating device, and the heating device starts heating after nitrogen is introduced to replace the oxygen inside the heating device.

[0009] Preferably, in step 1, the heating temperature of the positive electrode material by the heating device must be controlled at 60-65° C., at which temperature the residual alkali gas is stably volatilized.

[0010] Preferably, in step 2, when the heating device is heating the positive electrode material, it is strictly forbidden to open the device to prevent oxygen from entering the heating device.

[0011] Preferably, in step 2, after the coolant is obtained, it is sealed and stored. The coolant needs to have residual temperature after collection and needs to be cooled naturally in a sealed environment.

[0012] Preferably, in step 3, the condensate and the solvent are mixed and stirred for 5-10 min, and then filtered and filtered again.

[0013] Preferably, in step 3, the mixing ratio of the condensate and the solvent is 1:1.

[0014] Preferably, in step 4, the indicator is one of phenolphthalein, methyl red, methyl orange, bromophenol blue, bromocresol green, bromothymol blue and phenol red.

[0015] Preferably, in step 4, during the titration process, the determination is made by observing the color change of the solution; Phenolphthalein is preferably used as an indicator. When the solution changes from red to colorless and does not fade within 30 seconds, it is the titration endpoint3; Calculation results: According to the volume and concentration of hydrochloric acid consumed, the residual alkali content in the positive electrode material is calculated. The formula is: residual alkali content = (volume of hydrochloric acid consumed × hydrochloric acid degree) / sample mass.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In this invention patent, nitrogen is introduced into a heating device. Nitrogen is used to replace oxygen, and the heating device is used to heat the cathode material, so that the residual alkali on the cathode material is separated from the cathode material in the form of gas volatilization; the gas is converted from a gaseous state to a liquid state by a condensation device to obtain a condensate with residual alkali; then the amount of residual alkali is detected by the traditional hydrochloric acid titration method; by using the above method, the cathode material does not need to come into contact with a solvent; the cathode material will not undergo oxidation and ion exchange reactions with the solvent, and the cathode material will not become unusable due to oxygen corrosion; the content of residual alkali will not increase in alkalinity due to the occurrence of ion exchange reactions; this not only ensures the stable use of the cathode material, but also ensures the accurate value of the detection of the residual alkali content. Detailed implementation mode

[0017] The present invention will be described in more detail by way of examples below. These examples are only illustrative and do not limit the scope of the present invention in any way.

[0018] The present invention provides a technical solution: a method for detecting residual alkali on the surface of a battery cathode material, including the following steps: S1: Material preparation: nitrogen, heating device, condensation equipment, cathode material, solvent, titrant acid solution; Among them, nitrogen is to be introduced into the heating device; the inlet of the condensation equipment is connected to the outlet of the heating device; The cathode material is placed in the heating device and heated in a nitrogen environment, and the heating temperature is 60 - 65 °C; S2: Nitrogen is filled into the heating device, and the heating device heats the cathode material. Nitrogen has low activity, preventing the cathode material from reacting with oxygen in the air during the heating process; The cathode material is heated to 60 - 65 °C by the heating device, and the residual alkali on the cathode material will generate volatilized gas. After the volatilized gas is generated, it will enter the condensation equipment through the outlet of the heating device. The condensation equipment cools the volatilized gas to convert it from a gas to a liquid, and finally a condensate is obtained. The residual alkali in the cathode material volatilizes in the form of gas and is completely separated from the cathode material; S3: The obtained condensate is mixed with a solvent (water) to obtain a solution to be measured; S4: According to the basic acid-base titration principle, an appropriate indicator is added, and titration is carried out with a standard hydrochloric acid solution, and the residual content is calculated.

[0019] Example 1: Material preparation: nitrogen, heating device, condensation equipment, positive electrode material, solvent, titration acid solution; among them, nitrogen should be introduced into the heating device; the inlet of the condensation equipment is connected to the outlet of the heating device; the positive electrode material is placed in the heating device and heated in a nitrogen environment, and the heating temperature is 60-65 °C; nitrogen is introduced into the heating device, and the heating device heats the positive electrode material. Nitrogen has low activity to prevent the positive electrode material from reacting with oxygen in the air during heating; the positive electrode material is heated to 60-65 °C by the heating device, and the residual alkali on the positive electrode material will generate volatile gas. After the volatile gas is generated, it will enter the condensation equipment through the outlet of the heating device. The condensation equipment cools the volatile gas to convert it from gas to liquid, and finally obtains the condensate. The residual alkali in the positive electrode material volatilizes in the form of gas and is separated from the positive electrode material; the obtained condensate and solvent (water) are mixed to obtain the solution to be measured; according to the basic acid-base titration principle, the corresponding indicator is added, and titration is carried out with a standard hydrochloric acid solution, and the residual content is calculated.

[0020] Example 2: In Example 1, the following processes are added: In step 1, nitrogen must be introduced into the heating device, and the heating device starts heating after nitrogen replaces the oxygen inside it; the heating temperature of the heating device for the positive electrode material must be controlled at 60-65 °C, and the residual alkali gas volatilizes stably at this temperature.

[0021] In step 2, during the heating of the positive electrode material by the heating device, it is strictly prohibited to open the device to avoid oxygen entering the heating device; after the coolant is obtained, it is stored in a sealed manner. The coolant needs to be collected with residual heat and cooled naturally in a sealed environment.

[0022] Material preparation: nitrogen, heating device, condensing device, positive electrode material, solvent, titrated acid solution; nitrogen must be passed into the heating device; the air inlet of the condensing device is connected to the air outlet of the heating device; the positive electrode material is placed in the heating device and heated in a nitrogen environment at a temperature of 60-65°C; nitrogen must be passed into the heating device, and the heating device starts heating after nitrogen is passed in to replace the internal oxygen; the heating temperature of the positive electrode material by the heating device must be controlled at 60-65°C, at which temperature the residual alkali gas evaporates stably; the heating device is filled with nitrogen, and the heating device heats the positive electrode material. Nitrogen has a low activity, which prevents the positive electrode material from reacting with oxygen in the air during the heating process; the positive electrode material is heated to 6 by the heating device. 0-65℃, the residual alkali on the positive electrode material will produce volatile gas, which will enter the condensing device through the gas outlet of the heating device. The condensing device cools the volatile gas to convert it from gas to liquid, and finally obtains the condensate. The residual alkali in the positive electrode material is volatilized in the form of gas after heating and the positive electrode material is stripped; during the heating process of the positive electrode material by the heating device, it is strictly forbidden to open the device to prevent oxygen from entering the heating device; after the coolant is obtained, it is sealed and stored. The coolant needs to have residual temperature after collection and needs to be naturally cooled in a sealed environment; the obtained condensate is mixed with the solvent (water) to obtain the liquid to be measured; according to the basic principle of acid-base titration, the corresponding indicator is added, titrated with standard hydrochloric acid solution, and the residual content is calculated.

[0023] Embodiment three: In the second embodiment, the following steps are added: In step 3, the condensate and the solvent need to be mixed and stirred for 5-10 minutes, and then filtered and filtered again; the mixing ratio of the condensate and the solvent is 1:1.

[0024] In step 4, the indicator is one of phenolphthalein, methyl red, methyl orange, bromophenol blue, bromocresol green, bromothymol blue and phenol red; during the titration process, the color change of the solution is observed to make a judgment; phenolphthalein is preferably used as the indicator, and when the solution changes from red to colorless and does not fade within 30 seconds, it is the titration endpoint; calculation result: the residual alkali content in the positive electrode material is calculated according to the volume and concentration of the consumed hydrochloric acid, and the formula is: residual alkali content = (consumed hydrochloric acid volume × salt concentration) / sample mass.

[0025] Material preparation: nitrogen, heating device, condensing device, positive electrode material, solvent, titrated acid solution; nitrogen must be passed into the heating device; the air inlet of the condensing device is connected to the air outlet of the heating device; the positive electrode material is placed in the heating device and heated in a nitrogen environment, and the heating temperature is 60-65°C; nitrogen must be passed into the heating device, and the heating device starts heating after nitrogen is introduced to replace the internal oxygen; the heating temperature of the positive electrode material by the heating device must be controlled at 60-65°C, at which temperature the residual alkali gas evaporates stably; the heating device is filled with nitrogen, and the heating device heats the positive electrode material. Nitrogen has low activity to prevent the positive electrode material from reacting with oxygen in the air during the heating process; the positive electrode material is heated to 60-65°C by the heating device, and the residual alkali on the positive electrode material will produce volatile gas, which will enter the condensing device through the air outlet of the heating device after being produced. The condensing device cools the volatile gas to convert it from gas to liquid, and finally obtains the condensate. The residual alkali in the positive electrode material is volatilized in the form of gas after heating and the positive electrode material is completed Stripping; During the heating process of the positive electrode material by the heating device, it is strictly forbidden to open the device to prevent oxygen from entering the heating device; After the coolant is obtained, it is sealed and stored. The coolant needs to have residual temperature after collection and needs to be cooled naturally in a sealed environment; The obtained condensate is mixed with the solvent (water) to obtain the liquid to be measured; The condensate and the solvent need to be stirred for 5-10 minutes, and then filtered after stirring; The mixing ratio of condensate and solvent is 1:1; According to the basic principle of acid-base titration, the corresponding indicator is added and the standard is used. The quasi-hydrochloric acid solution is titrated and the residual content is calculated; the indicator is one of phenolphthalein, methyl red, methyl orange, bromophenol blue, bromocresol green, bromothymol blue and phenol red; during the titration, the color change of the solution is observed; phenolphthalein is preferably used as the indicator, and when the solution changes from red to colorless and does not fade within 30 seconds, it is the titration endpoint; Calculation result: According to the volume and concentration of hydrochloric acid consumed, the residual alkali content in the positive electrode material is calculated, and the formula is: residual alkali content = (volume of hydrochloric acid consumed × salt concentration) / sample mass.

[0026] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for detecting residual alkali on the surface of a battery positive electrode material, characterized in that: The following steps are involved: S1: Material preparation: nitrogen, heating device, condensation equipment, positive electrode material, solvent, titration acid solution; The nitrogen gas shall be introduced into the heating device; the air inlet of the condensing device shall be connected to the air outlet of the heating device; The positive electrode material is placed in a heating device and heated in a nitrogen environment at a temperature of 60-65°C; S2: Nitrogen is filled into the heating device, and the heating device heats the positive electrode material. Nitrogen has a low activity, which prevents the positive electrode material from reacting with oxygen in the air during the heating process; The positive electrode material is heated to 60-65°C by a heating device, and the residual alkali on the positive electrode material will produce volatile gas. After being produced, the volatile gas will enter the condensation device through the gas outlet of the heating device. The condensation device cools the volatile gas to convert it from gas to liquid, and finally obtains condensate. The residual alkali in the positive electrode material is volatilized in the form of gas after heating and the positive electrode material is stripped; S3: mixing the obtained condensate with a solvent (water) to obtain a solution to be measured; S4: According to the basic acid-base titration principle, add the corresponding indicator, titrate with standard hydrochloric acid solution, and calculate the residual content.

2. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 1, nitrogen must be introduced into the heating device, and the heating device starts heating after nitrogen is introduced to replace the oxygen inside it.

3. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 1, the heating temperature of the positive electrode material by the heating device must be controlled at 60-65°C, at which temperature the residual alkali gas stably evaporates.

4. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 2, when the heating device is heating the positive electrode material, it is strictly forbidden to open the device to prevent oxygen from entering the heating device.

5. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 2, after the coolant is obtained, it is sealed and stored. The coolant needs to have residual temperature after collection and needs to be cooled naturally in a sealed environment.

6. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 3, the condensate and the solvent are mixed and stirred for 5-10 minutes, and then filtered.

7. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 3, the mixing ratio of the condensate and the solvent is 1:

1.

8. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 4, the indicator is one of phenolphthalein, methyl red, methyl orange, bromophenol blue, bromocresol green, bromothymol blue and phenol red.

9. The method for detecting residual alkali on the surface of a positive electrode material of a battery according to claim 1, characterized in that: In step 4, during the titration process, the color change of the solution is observed to determine; Phenolphthalein is preferably used as an indicator. When the solution changes from red to colorless and does not fade within 30 seconds, it is the titration endpoint; Calculation results: According to the volume and concentration of hydrochloric acid consumed, the residual alkali content in the positive electrode material is calculated. The formula is: residual alkali content = (volume of hydrochloric acid consumed × hydrochloric acid degree) / sample mass.