A lithium ion concentration detection system and method

Abstract

The application discloses a lithium ion concentration detection system, comprising: a control module, used for sending control instructions to a scanning signal generation module; the scanning signal generation module is used for generating signals required by a constant potential generation module according to the control instructions; the constant potential generation module is connected with a polyanion compound electrode module, and used for providing scanning voltage to the polyanion compound electrode module; a working electrode, an auxiliary electrode and a reference electrode; the application can collect the characteristic current of the working electrode in real time through the control module, and then determine the lithium ion concentration in the solution to be measured. The online and offline detection of lithium ions is realized. The concentration of lithium ions can be simply, low-cost and quickly tested. When used for industrial production, the lithium ion concentration can be transmitted to a process system, and then the process is adjusted in real time according to the lithium ion concentration, so that the application has the characteristics of real-time online, high accuracy and high efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ion concentration detection, in particular to a lithium ion concentration detection system and method. BACKGROUND

[0002] In the process of field exploration and industrial production, it is very important to quickly detect the lithium ion concentration in the aqueous solution. At present, the commonly used methods for detecting the lithium ion concentration are atomic absorption spectrometry and inductively coupled plasma emission spectrometry. However, once the equipment is installed, it is difficult to move, and nitrogen or argon is required in the detection process, which is costly.

[0003] The lithium ion selective electrode is made of a material that is selective to lithium ions and is divided into two types: voltage lithium ion selective electrode and current lithium ion selective electrode. When the voltage lithium ion selective electrode is working, it is immersed in a lithium-containing solution together with a reference electrode to form a primary cell. The potential of the primary cell and the logarithm of the lithium concentration in the solution are linearly related. Accordingly, the lithium concentration in the solution can be detected. Crystal film, ion-association complex, and neutral carrier materials have been used to make voltage lithium ion selective electrodes. However, these materials are either expensive or difficult to use for a long time or have poor resistance to interference from homologous impurities, which cannot meet the requirements. When the current lithium ion selective electrode is working, it is subjected to voltammetric testing, and the current obtained is linearly related to the lithium concentration in the solution. Accordingly, the lithium concentration in the solution can be detected. However, the material used is an organic material with poor electrical conductivity, and the material structure is complex and difficult to synthesize, such as 6,6-dibenzyl-14-crown-4.

[0004] At the same time, in the process of lithium production, it is often necessary to quickly and real-time obtain the lithium ion concentration of the solution in production to facilitate timely adjustment or feedback of the industrial production process. The usual practice is to sample the solution, send the sample off-line for detection to obtain the lithium ion concentration, and adjust the production process according to the detected lithium ion concentration, which results in a tedious detection process and makes it impossible to collect signals in real time and make timely process adjustments. SUMMARY

[0005] Therefore, it is necessary to propose a lithium ion concentration detection system to solve the above problems.

[0006] A lithium ion concentration detection system, comprising:

[0007] A control module connected to a scanning signal generation module and a constant potential generation module, used to send control instructions to the scanning signal generation module, collect characteristic current flowing through the working electrode, and perform data processing.

[0008] A scanning signal generation module connected to a constant potential generation module, used to generate signals required by the constant potential generation module according to the control instructions.

[0009] A constant potential generating module is connected with the polyanionic compound electrode module, and is used to provide a scanning voltage to the polyanionic compound electrode module.

[0010] A polyanionic compound electrode module is connected with the control module, and is used to react with lithium ions in a solution to be measured; the polyanionic compound electrode module comprises a working electrode, an auxiliary electrode and a reference electrode.

[0011] In an embodiment, the control module collects a characteristic current after the working electrode is placed in the solution to be measured, and determines the lithium ion concentration of the solution to be measured according to a standard curve (hereinafter referred to as a standard curve) between the characteristic current and the relationship between the lithium ion concentration in the solution and the characteristic current of a test standard solution.

[0012] In an embodiment, the constant potential generating module comprises a first operational amplifier, a second operational amplifier and a third operational amplifier.

[0013] The non-inverting input terminal of the first operational amplifier is connected to ground, the inverting input terminal of the first operational amplifier is connected to a signal sent by the scanning signal generating module, and the output terminal of the first operational amplifier is connected with the auxiliary electrode.

[0014] The non-inverting input terminal of the second operational amplifier is connected with the reference electrode, the inverting input terminal of the second operational amplifier is connected with the output terminal of the second operational amplifier, and the inverting input terminal of the second operational amplifier is connected to the signal.

[0015] The non-inverting input terminal of the third operational amplifier is connected to ground, the inverting input terminal of the third operational amplifier is connected with the working electrode, and the output terminal of the third operational amplifier is connected with the inverting input terminal of the third operational amplifier.

[0016] In an embodiment, the constant potential generating module further comprises a first resistor, a second resistor, a third resistor and a fourth resistor.

[0017] The first resistor and the second resistor are both connected between the scanning signal generating module and the inverting input terminal of the first operational amplifier.

[0018] The third resistor is connected between the inverting input terminal of the first operational amplifier and the output terminal of the second operational amplifier, and the fourth resistor is connected between the output terminal of the third operational amplifier and the inverting input terminal of the third operational amplifier, so as to convert a current signal flowing through the working electrode into a voltage signal and send the voltage signal to the control module for processing.

[0019] In one embodiment, the working electrode is a plurality of working electrodes, each connected to the control module through a switch; the control module sends a control signal to the switch to realize the reaction of the corresponding working electrode with lithium ions in the solution to be measured.

[0020] In one embodiment, the working electrode is a lithium-depleted current collector electrode.

[0021] The auxiliary electrode is a graphite plate.

[0022] The reference electrode is a saturated calomel electrode.

[0023] In one embodiment, the auxiliary electrode can also be a platinum electrode.

[0024] In one embodiment, the working electrode is a current collector electrode composed of a conductive substrate and a layer of polyanion compound material arranged thereon.

[0025] In one embodiment, the working electrode is a FePO4 current collector electrode.

[0026] The FePO4 current collector electrode is obtained by electrochemically de-lithiating a current collector electrode coated with LiFePO4.

[0027] A method for detecting the concentration of lithium ions, the method comprising:

[0028] Electrochemically de-lithiating a current collector electrode coated with a cationic compound;

[0029] Placing a working electrode, an auxiliary electrode, and a reference electrode into a standard solution;

[0030] According to the requirements of the test method, a constant potential generation module applies a scanning voltage to the working electrode, the auxiliary electrode, and the reference electrode;

[0031] A control module collects the characteristic current of the working electrode after being placed in each standard solution, and establishes a standard curve through the characteristic current;

[0032] Placing the working electrode, the auxiliary electrode, and the reference electrode into a solution to be tested, and a control module collects the characteristic current generated after the reaction of the working electrode with lithium ions in the test solution;

[0033] A control module determines the concentration of lithium ions in the solution to be tested using the standard curve.

[0034] The lithium ion concentration detection system can send instructions to the scanning signal generation module through the control module, so that the scanning signal generation module sends scanning signals to the constant potential generation module, so that the constant potential generation module provides voltages for the working electrode, the auxiliary electrode and the reference electrode according to different test methods. During testing, first, the lithium ion concentration detection system is used to test the standard sample, the polyanion compound electrode module is added to the standard solution, so that the working electrode reacts with the lithium ions in the standard solution to generate a characteristic current, and a standard curve is established. The polyanion compound electrode module is added to the to-be-tested solution by using the above method, the current flowing through the working electrode is collected, the characteristic current is obtained, and the lithium ion concentration in the to-be-tested solution is determined by using the obtained standard curve.

[0035] The selective detection of lithium ions is realized: online and offline detection. The concentration of lithium ions can be simply, low-cost and quickly tested. When used for industrial production, the lithium ion concentration can be transmitted to the process system, and the process can be adjusted in real time according to the lithium ion concentration, having the characteristics of real-time online, accurate and efficient. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0037] In which:

[0038] Figure 1 It is a system block diagram of the lithium ion concentration detection system in an embodiment;

[0039] Figure 2 It is a circuit diagram of the constant potential generation module in an embodiment;

[0040] Figure 3 It is a flowchart of the lithium ion concentration detection method in an embodiment;

[0041] Figure 4 It is a curve graph of the relationship between the delithiation peak current and the lithium concentration of the solution. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] The application provides a lithium ion concentration detection system, which refers to Figure 1 , a system block diagram of the embodiment of the application, comprising:

[0044] The control module 100 is connected with the scanning signal generation module 200, and is used for sending a control instruction to the scanning signal generation module 200.

[0045] The scanning signal generation module 200 is connected with the constant potential generation module 300, and is used for generating a signal required by the constant potential generation module 300 according to the control instruction.

[0046] The constant potential generation module 300 is connected with the polyanion compound electrode module, and is used for providing a scanning voltage to the polyanion compound electrode module; when connected with the signal scanning generator, the constant potential generation module 300 can control the working electrode potential (relative to a certain reference electrode) to change with time according to a certain program, and is not affected by the impedance change of the electrode system, and is used for measuring the current response to the potential. Instead of controlling the electrode potential to be unchanged at a certain potential, the electrode potential is controlled to change according to a certain predetermined rule. According to the scanning method of controlling the working electrode potential, the following can be selected: linear potential scanning, differential pulse voltammetry scanning, square wave scanning and the like.

[0047] The polyanion compound electrode module (hereinafter referred to as the electrode module) is connected with the control module 100, and is used for reacting with lithium ions in a to-be-detected solution.

[0048] The electrode module comprises a working electrode 400, an auxiliary electrode 500 and a reference electrode 600; the control module 100 collects a characteristic current of the working electrode 400 after the working electrode 400 is placed in the to-be-detected solution, and the characteristic current is used for determining the lithium ion concentration of the to-be-detected solution.

[0049] Specifically, the lithium ion concentration detection system according to the application sends an instruction to the scanning signal generation module through the control module according to different test methods, so that the scanning signal generation module sends a signal to the constant potential generation module, so that the constant potential generation module can provide a control scanning voltage for the working electrode, the auxiliary electrode and the reference electrode according to the received signal. Under the joint action of the auxiliary electrode and the reference electrode, the working electrode reacts with lithium ions in the to-be-detected solution to produce a current. At this time, the control module can collect the current of the working electrode in real time, obtain a characteristic current, and determine the lithium ion concentration in the to-be-detected solution by substituting the characteristic current into a standard curve of the characteristic current formed when a standard solution is tested in the control module and the lithium ion concentration in the solution. The lithium ion concentration in the solution is detected.

[0050] In the test, first, the lithium ion concentration detection system is used to test the standard solution, the polyanionic compound electrode module is added to the standard solution, so that the working electrode reacts with lithium ions in the standard solution, the system collects and obtains the characteristic current, and a standard curve is established. The polyanionic compound electrode module is added to the solution to be tested by using the above method, the current flowing through the working electrode is collected, the corresponding characteristic current is obtained, and then the standard curve obtained above is used to determine the lithium ion concentration in the solution to be tested. The detection of lithium ions is realized.

[0051] The characteristic current is the peak current value of the lithium ion intercalation or deintercalation voltammetry curve of the working electrode reacting with lithium ions in the solution under the scanning voltage, or the current value of the current platform region in the current-time curve of the lithium ion intercalation process in the working electrode under the constant potential. The characteristic current flowing through the working electrode and the lithium concentration in the solution have a linear relationship.

[0052] In one embodiment, the control module 100 comprises:

[0053] The control module module is used for sending control instructions to the scanning signal generation module 200; and

[0054] The characteristic current after the working electrode 400 is placed in the solution to be tested is collected and sent to the control module, and the control module determines the lithium ion concentration of the solution to be tested according to the characteristic current.

[0055] In one embodiment, as shown in Figure 2 The constant potential generation module 300 comprises a first operational amplifier A1, a second operational amplifier A2, a third operational amplifier A3, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4.

[0056] The noninverting input terminal of the first operational amplifier A1 is grounded, the inverting input terminal of the first operational amplifier A1 is connected to the signal sent by the scanning signal generation module 200, and the output terminal of the first operational amplifier A1 is connected to the auxiliary electrode 500.

[0057] The noninverting input terminal of the second operational amplifier A2 is connected to the reference electrode 600, the inverting input terminal of the second operational amplifier A2 is connected to the output terminal of the second operational amplifier A2, and the inverting input terminal of the second operational amplifier A2 is connected to the signal.

[0058] The noninverting input terminal of the third operational amplifier A3 is grounded, the inverting input terminal of the third operational amplifier A3 is connected to the working electrode 400, and the output terminal of the third operational amplifier A3 is connected to the inverting input terminal of the third operational amplifier A3.

[0059] The first resistor R1 and the second resistor R2 are connected between the scanning signal generation module 200 and the inverting input terminal of the first operational amplifier A1;

[0060] The third resistor R3 is connected between the inverting input terminal of the first operational amplifier A1 and the output terminal of the second operational amplifier A2; and the fourth resistor R4 is connected between the output terminal of the third operational amplifier A3 and the inverting input terminal of the third operational amplifier A3, so as to change the current flowing through the working electrode into a voltage signal and send the voltage signal to the control module for processing. The signals sent by the scanning signal generation module 200 can be amplified by the first operational amplifier A1, the second operational amplifier A2 and the third operational amplifier A3, so that the constant potential generation module can provide accurate scanning voltage for the working electrode, the auxiliary electrode and the reference electrode.

[0061] In one embodiment, the working electrode 400 is multiple and connected to the control module 100 through switches respectively; the control module 100 sends a control switching signal to the switches, so as to realize the embedding or de-embedding reaction of the corresponding working electrode 400 and lithium ions in the solution to be measured.

[0062] Specifically, in order to ensure the stable operation of the system and avoid the performance decline of the working electrode when only one working electrode works for a long time, in the embodiment, the working electrode 400 is multiple, each working electrode 400 is connected to a switch, each switch is connected to the constant potential generation module, each switch is controlled by the control module 100, and the use time of each working electrode is fixed. After the current working electrode reaches the fixed use time, the control module 100 controls the next switch to be turned on, so that the constant potential generation module provides scanning voltage for the working electrode corresponding to the switch, so that the working electrode continues to work normally, and manual replacement of the working electrode is avoided, and the working efficiency of the system is improved.

[0063] In one embodiment, the working electrode 400 is a current collector electrode after lithium is removed;

[0064] The auxiliary electrode 500 is a graphite plate or a platinum electrode; the reference electrode 600 is a saturated calomel electrode; and the scanning signal generation module 200 generates a waveform of a scanning signal, and the constant potential generation module controls the signal output to the electrode module.

[0065] In one embodiment, the working electrode 400 is a FePO4 current collector electrode;

[0066] The current collector electrode coated with LiFePO4 is chemically delithiated, and is preferentially electrochemically delithiated, so that the current collector electrode coated with LiFePO4 is delithiated to obtain the FePO4 current collector electrode.

[0067] The conductive base of the current collector electrode is one of titanium, zirconium, hafnium, tantalum, niobium, gold, platinum and the like, or an alloy thereof, and graphite, carbon paper, carbon fiber cloth and the like can also be used.

[0068] The application further provides a lithium ion concentration detection method, as shown in the specification, which comprises the following steps: Figure 3

[0069] S10: electrochemically delithiating the current collector electrode coated with the polyanion compound;

[0070] S20: placing the working electrode, the auxiliary electrode and the reference electrode into a standard solution;

[0071] S30: applying a scanning voltage to the working electrode, the auxiliary electrode and the reference electrode by the constant potential generation module according to the requirements of the test method;

[0072] S40: collecting the characteristic current of the working electrode after being placed into each standard sample solution, and establishing a standard curve according to the linear relationship between the characteristic current and the lithium ion concentration of the solution;

[0073] S50: placing the working electrode, the auxiliary electrode and the reference electrode into a solution to be tested, and collecting the characteristic current generated after the working electrode reacts with lithium ions in the test solution by the control module;

[0074] S60: determining the concentration of lithium ions in the solution to be tested by the control module using the standard curve and the characteristic current of the test solution.

[0075] Specifically, the current collector electrode coated with LiFePO4 as the positive electrode and the foamed nickel as the negative electrode are simultaneously placed into a 10 g / mol Nacl solution; a voltage is applied, the current collector electrode coated with LiFePO4 is delithiated to obtain a FePO4 current collector electrode, and the working electrode 400 is obtained;

[0076] The working electrode 400, the auxiliary electrode 500 and the reference electrode 600 are placed into a standard solution to obtain a standard curve of the characteristic current of the working electrode 400 and the lithium ion concentration in the standard solution, and the characteristic current in the standard curve is proportional to or in other functional relationship with the lithium ion concentration in the standard solution. The working electrode 400, the auxiliary electrode 500 and the reference electrode 600 are placed into a solution to be tested; the scanning signal generation module 200 generates a scanning excitation signal under the control of the control module 100, the scanning voltage is applied to the working electrode 400, the auxiliary electrode 500 and the reference electrode 600 by the constant potential generation module 300, the characteristic current of the working electrode 400 after being placed into the test solution is collected, and the collected characteristic current of the working electrode 400 is substituted into the standard curve to obtain the lithium ion concentration of the test solution.​

[0077] The application can acquire the characteristic current by collecting the current of the working electrode in real time through the control module, and then determine the lithium ion concentration in the solution to be measured. The online and offline detection of lithium ions is realized. The concentration of lithium ions can be tested simply, at low cost and quickly. When used in industrial production, the lithium ion concentration can be transmitted to the process system, and then the process is adjusted in real time according to the lithium ion concentration, which has the characteristics of real-time online and accurate and efficient.

[0078] Verification test example:

[0079] LiFePO4, Ketjen black and PVDF were mixed uniformly according to a mass ratio of 7:2:1, then NMP was added, and the mixture was stirred uniformly and coated on titanium and dried to prepare an electrode. Under the condition of 15℃, the potential was controlled at 0.5V (vs SCE), 100% lithium was removed by electricity, then the lithium was embedded in a chloride solution with a lithium concentration of 1-100ppm, a sodium ion concentration of 1g / L, a magnesium ion concentration of 2g / L and a potassium ion concentration of 1.5g / L, a potential control of-0.15V (vs SCE) and lithium embedding for 40s, then the lithium was removed by scanning, a linear scanning was adopted, and the scanning was performed from-0.15V (vs SCE) to 0.5V (vs SCE) at a scanning speed of 2mv / s. The linear relationship between the obtained lithium removal peak current and the solution lithium concentration is shown in Figure 4 .

[0080] The chloride solution with different lithium concentrations, a sodium ion concentration of 1g / L, a magnesium ion concentration of 2g / L and a potassium ion concentration of 1.5g / L was prepared and tested according to the above method, and the obtained current was compared with the Figure 4 linear relationship, so that the lithium ion concentration in the solution can be measured. The detection results and the recovery rate are shown in Table 1.

[0081] Table 1. Solution lithium ion test comparison table

[0082]

[0083]

[0084] The technical features of the above embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0085] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific manner, but should not be construed as limiting the scope of the patent of the present application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A lithium ion concentration detection system, characterized by, The application relates to a lithium ion concentration detection system. The control module is connected with a scanning signal generation module and a constant potential generation module, is used for sending a control instruction to the scanning signal generation module, collecting characteristic current flowing through a working electrode, and performing data processing; The scanning signal generation module is connected with the constant potential generation module, and is used for generating a signal required by the constant potential generation module according to the control instruction; The constant potential generation module is connected with a polyanion compound electrode module, and is used for providing a scanning voltage to the polyanion compound electrode module; The polyanion compound electrode module is connected with the control module, and is used for reacting with lithium ions in a to-be-detected solution; the polyanion compound electrode module comprises a working electrode, an auxiliary electrode and a reference electrode; The control module collects characteristic current of the working electrode after the working electrode is placed in the to-be-detected solution, and determines the lithium ion concentration of the to-be-detected solution according to the characteristic current and a standard curve obtained according to a standard solution; The working electrode is a FePO4 current collector electrode; the FePO4 current collector electrode is obtained by delithiating a current collector electrode coated with LiFePO4 by using an electrochemical method.

2. The lithium ion concentration detection system of claim 1, wherein The constant potential generation module comprises a first operational amplifier, a second operational amplifier and a third operational amplifier; The non-inverting input end of the first operational amplifier is connected with the scanning signal generation module, and the output end of the first operational amplifier is connected with the auxiliary electrode; The inverting input end of the second operational amplifier is connected with the reference electrode, the output end of the second operational amplifier is connected with the inverting input end of the second operational amplifier, and the inverting input end of the second operational amplifier is connected with the signal; The non-inverting input end of the third operational amplifier is connected with the working electrode, and the output end of the third operational amplifier is connected with the inverting input end of the third operational amplifier.

3. The lithium ion concentration detection system of claim 2, wherein The constant potential generation module further comprises a first resistor, a second resistor, a third resistor and a fourth resistor; The first resistor and the second resistor are both connected between the scanning signal generation module and the inverting input end of the first operational amplifier; The third resistor is connected between the inverting input end of the first operational amplifier and the output end of the second operational amplifier, and the fourth resistor is connected between the output end of the third operational amplifier and the inverting input end of the third operational amplifier.

4. The lithium ion concentration detection system of claim 1, wherein The working electrode is a plurality of working electrodes, and each working electrode is connected with the control module through a switch; the control module sends a control signal to the switch to realize the reaction of the corresponding working electrode with the lithium ions in the to-be-detected solution.

5. The lithium ion concentration detection system according to claim 1, wherein The working electrode is a current collector electrode after delithiation treatment; The auxiliary electrode is a graphite plate; The reference electrode is a saturated calomel electrode.

6. The lithium ion concentration detection system of claim 1, wherein The auxiliary electrode is a platinum electrode.

7. The lithium ion concentration detection system according to claim 1, wherein The working electrode is a current collector electrode composed of a conductive substrate and a polyanion compound material layer arranged thereon.

8. A method of detecting lithium ion concentration, characterized by, The method comprises: electrochemically delithiating the current collector electrode coated with the polyanion compound; placing the working electrode, the auxiliary electrode and the reference electrode into a standard solution; the working electrode is a FePO4 current collector electrode; the FePO4 current collector electrode is obtained by delithiating a current collector electrode coated with LiFePO4 by using an electrochemical method; applying a scanning voltage to the working electrode, the auxiliary electrode and the reference electrode by a constant potential generating module according to the requirements of the test method; collecting the characteristic current of the working electrode after being placed into each standard solution by a control module, and establishing a standard curve; placing the working electrode, the auxiliary electrode and the reference electrode into a solution to be tested, and collecting the characteristic current generated after the working electrode reacts with lithium ions in the test solution by the control module; determining the concentration of lithium ions in the solution to be tested by the control module by using the standard curve and the characteristic current of the solution to be tested.

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