Sensor for in-situ detection of dissolved oxygen and pH in electrolyte and application method thereof

Abstract

The invention relates to the field of sensors, and discloses a sensor for in-situ detection of dissolved oxygen and pH in an electrolyte and an application method thereof. The sensor of the present invention comprises: a substrate; the integrated circuit chip, the voltage / current reading interface and the planar electrode are arranged on the substrate; the reference electrode, the pH sensitive grid electrode and the dissolved oxygen sensitive grid electrode are arranged outside the substrate. Wherein the voltage / current reading interface is respectively connected with the integrated circuit chip and the planar electrode; the reference electrode, the pH sensitive grid electrode and the dissolved oxygen sensitive grid electrode are respectively connected with the planar electrode through an epitaxial tab and a lead; the reference electrode, the pH sensitive grid electrode and the dissolved oxygen sensitive grid electrode are fibrous and are clamped between the two layers of diaphragms of the battery. The sensor disclosed by the invention can accurately detect the pH value and the dissolved oxygen concentration of the electrolyte in real time under the condition of not influencing the normal operation of the battery.

Description

Technical Field

[0001] The present invention relates to the field of sensors, and in particular to a sensor for in-situ detection of dissolved oxygen and pH in an electrolyte and an application method thereof. Background Art

[0002] The battery-dominated new energy-related industries have become one of the most promising areas in recent years. Both high-energy-density lithium-ion batteries and safe and reliable aqueous batteries have attracted widespread attention from the academic community. However, the development of aqueous batteries still faces some challenges. Taking aqueous zinc-ion batteries as an example, the growth of zinc dendrites, the dissolution and corrosion passivation of positive electrode materials, and the decomposition of electrolytes, etc., these factors will lead to the decay of the battery's cycle life, the rapid decline of Coulomb efficiency and reversible capacity, and seriously affect the battery performance. The changes in the composition of the battery electrolyte during operation can reflect the interaction between the side reactions in the battery and the electrolyte electrode interface. Real-time monitoring of the composition of the battery electrolyte, especially the real-time detection of dissolved oxygen and pH, helps to deepen the understanding of the complex potential electrochemical processes inside the battery, and opens up a new perspective for the analysis of battery performance decay and failure mechanisms.

[0003] It is not easy to capture the changes of target components in the complex environment of the battery. On the one hand, in-situ monitoring requires that the implantation of sensors should not affect the normal operation of the battery; on the other hand, the real-time changes of interface side reactions also put forward new requirements for the sensitivity and response time of the sensors. The existing battery monitoring and analysis field is often based on some relatively complex and large optical equipment. Optical sensors have insulation stability and high spatial resolution, which can accurately capture the subtle electrochemical changes inside the electrolyte, but at the same time, there are also some problems that cannot be ignored in the in-situ detection of batteries with optical fibers: first, the optical signal is easily affected by the internal stress strain and temperature of the battery, and the complex correction and decoupling of the target signal need to be considered; the short interaction at the tip of the optical fiber and the background noise of the inner core will limit the intensity of the target signal and be easily disturbed. The currently reported optical detection methods have large errors in the quantitative analysis of specific components of the electrolyte; due to incompatibility with the battery preparation process, the implantation of optical fibers will inevitably destroy the battery structure, and the large and expensive light source, optical path setting and spectrometer and other equipment also increase the difficulty of portable reading of conventional batteries, limiting the application value.

[0004] In summary, how to achieve accurate composition analysis and highly sensitive real-time in-situ monitoring of a small amount of electrolyte in a small space of a battery without destroying the battery structure and affecting the battery function is an important challenge. Accurate detection of electrolyte composition during battery operation can provide a basis and guide for internal battery mechanism research and battery design optimization, which is of great significance. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a sensor for in-situ detection of dissolved oxygen and pH in an electrolyte and an application method thereof. The sensor of the present invention can detect the pH value and dissolved oxygen concentration of the electrolyte in real time and accurately without affecting the normal operation of the battery.

[0006] The specific technical scheme of the present invention is: In a first aspect, the present invention provides a sensor for in-situ detection of dissolved oxygen and pH in an electrolyte, comprising: substrate; An integrated circuit chip containing transistors, a voltage / current reading interface and a planar electrode disposed on a substrate; A reference electrode, a pH sensitive gate and a dissolved oxygen sensitive gate are externally arranged on the substrate.

[0007] Wherein: the voltage / current reading interface is connected to the integrated circuit chip and the planar electrode respectively; the reference electrode, the pH sensitive gate and the dissolved oxygen sensitive gate are connected to the planar electrode through the epitaxial tabs and the wires respectively; the reference electrode, the pH sensitive gate and the dissolved oxygen sensitive gate are in the shape of fibers and are sandwiched between the double-layer diaphragms of the battery to be tested.

[0008] During the assembly process, in order to prevent the fiber electrodes (reference electrode, pH sensitive grid and dissolved oxygen sensitive grid) from directly contacting the positive and negative electrodes of the battery, the present invention cleverly designs the single-layer diaphragm into two-layer diaphragms, and sandwiches the fiber electrodes between the two layers of diaphragms, so that real-time in-situ detection can be performed without affecting the normal operation of the battery.

[0009] In summary, the present invention designs different fibrous pH-sensitive gates and dissolved oxygen-sensitive gates according to the changes in dissolved oxygen and pH of the specific components of the electrolyte during the operation of the aqueous battery, and implants them inside the battery. At the same time, they are connected to transistors outside the battery, which can integrate the selective detection of electrochemical signals inside the battery with the amplification of the signals, thereby realizing real-time in-situ detection of pH and dissolved oxygen inside the battery.

[0010] The working principle of the sensor of the present invention is as follows: Generally, after the target monitoring object (dissolved oxygen, hydrogen ions) undergoes an electrochemical reaction on the surface of the sensitive gate, the open circuit potential signal between the sensitive gate and the reference electrode changes, thereby converting the concentration signal into an electrical signal, and the transistor can convert the weak potential signal change (Δ V in ) translates into a significant change in source-drain current (Δ I DS ), so we can use I DSThe change of the signal can be used to obtain the concentration change of different objects to be detected in the electrolyte. On the one hand, the signal-to-noise ratio is improved while the difficulty of signal processing is reduced, which is conducive to the reading of the back-end system. On the other hand, the multi-channel circuit setting of this extended gate enables the entire sensor to achieve simultaneous and continuous detection of pH and dissolved oxygen in the electrolyte.

[0011] Preferably, the reference electrode comprises: a fibrous conductive substrate; an Ag / AgCl layer attached to the surface of the conductive substrate; and a solid electrolyte layer coated on the surface of the Ag / AgCl layer.

[0012] Preferably, the conductive substrate is carbon fiber or carbon nanotube fiber. The Ag / AgCl layer is coated on the surface of the conductive substrate by electrochemical reduction or silver paste, and then the silver on the surface is chlorinated by chemical reagents or electrochemical methods. The solid electrolyte is a PVB ethanol solution containing potassium chloride or sodium chloride.

[0013] The reference electrode of the present invention has good stability in various electrolytes, and can therefore provide a stable reference potential for various electrochemical tests. The flexible fiber substrate and miniaturized size make it suitable for various narrow spaces, and the preparation method is simple and has the advantage of low cost and large-scale preparation.

[0014] Preferably, the dissolved oxygen sensitive grid comprises: a fibrous conductive substrate; an oxygen reduction catalyst layer attached to the surface of the conductive substrate; an inner encapsulation layer coated on the surface of the oxygen reduction catalyst layer; and an outer encapsulation layer coated on the surface of the inner encapsulation layer. Further preferably, the conductive substrate is carbon fiber or carbon nanotube fiber. The oxygen reduction catalyst is platinum metal nanoparticles with a particle size of less than or equal to 10 nm. The inner encapsulation layer is a Nafion encapsulation layer; and the outer encapsulation layer is a PDMS encapsulation layer. Further preferably, when preparing the coating, Nafion is first applied to the electrode on which the oxygen reduction catalyst is deposited and dried, and then the electrode is further encapsulated with a PDMS solution.

[0015] The above-mentioned dissolved oxygen sensitive gate of the present invention has the advantages of high selectivity, high sensitivity, good robustness and low cost for large-scale preparation. In addition, the dissolved oxygen sensitive gate of the present invention is designed with inner and outer double packaging layers, which has the advantages that the inner packaging layer is conducive to oxygen reaction, repels negatively charged substances, reduces interference, and provides hydrogen ions in oxygen reduction reaction (for example, Nafion is selected as the inner packaging layer), and the outer packaging layer is conducive to protecting the inner packaging layer while also improving the mechanical properties (for example, PDMS is selected as the outer packaging layer).

[0016] Preferably, the pH sensitive grid comprises: a conductive substrate in a fibrous shape; and a pH sensitive material layer attached to the surface of the conductive substrate. Further preferably, the conductive substrate is carbon fiber or carbon nanotube fiber. The pH sensitive material is selected from polyaniline, carbon nanotube, graphene, zinc oxide, aluminum oxide, phthalocyanine or a composite material of the above pH sensitive materials.

[0017] The pH sensitive electrode of the present invention has the advantages of high selectivity and high sensitivity for pH and can be prepared on a large scale at low cost.

[0018] Preferably, the substrate is selected from one or more of a fiber substrate, a silicon substrate, a soda-lime glass substrate, a polyethylene naphthalate substrate and a polyimide substrate.

[0019] Preferably, the transistor is a commercially available metal oxide semiconductor field effect transistor (MOSFET), organic field effect transistor (OFET) or bipolar junction transistor (BJT).

[0020] In a second aspect, the present invention provides an application method for in-situ detection of dissolved oxygen and pH in an aqueous battery electrolyte using the above-mentioned sensor, which specifically comprises the following steps: 1) Connect the voltage / current reading interface to the portable wireless driving / testing device, connect the reference electrode, pH sensitive gate and dissolved oxygen sensitive gate to the gate of the transistor, and connect the source and drain of the transistor to the portable wireless driving / testing device.

[0021] 2) Single-channel tests were performed on the pH sensitive gate and the dissolved oxygen sensitive gate to obtain the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve.

[0022] 3) The aqueous battery is designed to have a double-layer diaphragm. During the battery assembly process, the reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid are sandwiched between the double-layer diaphragm.

[0023] 4) Connect the positive and negative electrodes of the battery to the battery testing system for cyclic charge and discharge; apply the same source-drain voltage and bias gate voltage to the transistor at the same time, and collect the current corresponding to the dissolved oxygen and pH; decouple and calibrate the collected different currents using the fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte inside the battery during the battery charging and discharging process.

[0024] The inventor team found that the gate voltage bias has a significant effect on in-situ detection. If the bias is in the subthreshold region, the transconductance of the device ( g m = Δ I DS / Δ V GS) is the largest, and the ability to convert gate voltage changes into current output is the strongest, but at the same time, the limited subthreshold window will also limit the detection range of analyte concentration. Considering that the multi-channel electrochemical sensor array for in-situ detection of the entire battery adopts a circuit setting with a shared reference, an attempt is made to complete the continuous concentration gradient test of different target detection objects (hydrogen ions and dissolved oxygen) under different gate voltage biases, and the gate voltage bias (-2 V to -1.75 V) that can enable multiple groups of target detection objects to cover a wider detection range is preferred, and the stable source-drain current signal is collected as much as possible to avoid the electrical signal being regulated to the off state by an overly positive gate voltage.

[0025] Preferably, in step 2), the method for single-channel testing of the pH sensitive gate and the dissolved oxygen sensitive gate is: under the same source-drain voltage bias and gate voltage bias, the reference electrode and the pH sensitive gate, the reference electrode and the dissolved oxygen sensitive gate are immersed in gradient pH and gradient dissolved oxygen test solutions for testing, the channel current value is recorded, and the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve are fitted respectively.

[0026] Preferably, in step 3), during the battery assembly process, the electrolyte is subjected to an initial value correction process before perfusion: the initial pH and initial dissolved oxygen of the electrolyte are tested and read, and the initial pH and initial dissolved oxygen are converted into corresponding initial current values ​​according to the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve. I DS in After the cycle charge and discharge in step 4) is completed, the initial current collected in step 4) is recorded as I DS 0 , the current collected in step 4) is based on the current value converted from the initial concentration, and the whole is multiplied by I DS in / I DS 0 , and obtain the corrected in-situ detection current. Finally, the in-situ detection current is converted through the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte inside the battery during the battery charging and discharging process.

[0027] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention implants a fibrous sensitive electrode into the battery, which can give full play to the advantages of electrochemical sensors such as high sensitivity, simple structure, easy miniaturization, diverse forms, and strong real-time monitoring capabilities, and can simultaneously realize real-time monitoring of dissolved oxygen and pH in the electrolyte.

[0028] (2) The present invention cleverly designs a single-layer diaphragm into a two-layer diaphragm, and implants the fiber electrode between the two layers of diaphragms during the battery preparation process. This is compatible with the battery preparation process and will not affect the operation of the battery, thereby enabling in-situ detection of the electrolyte composition inside the battery, and can more realistically reflect the changes in the electrolyte composition during the operation of the battery. This simple and accurate electrochemical in-situ detection method is of great significance for the mechanism research and performance optimization of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the preparation process of three reference electrodes, dissolved oxygen sensitive grids and pH sensitive grids based on carbon fiber substrates in Example 1 of the present invention.

[0030] Figure 2 It is a scanning electron microscope image of each stage of the preparation process of the dissolved oxygen sensitive grid based on the carbon fiber substrate in Example 1 of the present invention.

[0031] Figure 3 It is a structural cross-sectional view (left) of a soft-pack battery with a sensitive grid implanted in Example 2 of the present invention and a structural schematic diagram of the sensor body (right).

[0032] Figure 4 3. The gradient curve (left) and fitting curve (right) of the real-time response during the dissolved oxygen detection process in Example 3 of the present invention.

[0033] Figure 5 3. The left side shows the gradient curve (left) and the right side shows the fitting curve (right) of the real-time response during the pH value measurement process in Example 3 of the present invention.

[0034] Figure 6 This is a physical photograph of the soft-pack battery undergoing in-situ testing in Example 3 of the present invention.

[0035] Figure 7 It is the channel current output signal of dissolved oxygen and pH collected by in-situ detection in Example 3 of the present invention and the real-time change of dissolved oxygen concentration and pH in the battery after decoupling calibration.

[0036] The figures are marked as: battery negative electrode 301, battery positive electrode current collector 302, positive electrode material 303, diaphragm 304, reference electrode 305-1, pH sensitive gate 305-2, dissolved oxygen sensitive gate 305-3, pole ear 306, substrate 307, integrated circuit chip 308, voltage / current reading interface 309, planar electrode 310. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the embodiments.

[0038] Overall embodiment First, a sensor for in-situ detection of dissolved oxygen and pH in an electrolyte, comprising: substrate; An integrated circuit chip containing transistors, a voltage / current reading interface and a planar electrode disposed on a substrate; A reference electrode, a pH sensitive gate and a dissolved oxygen sensitive gate are externally arranged on the substrate.

[0039] Wherein: the voltage / current reading interface is connected to the integrated circuit chip and the planar electrode respectively; the reference electrode, the pH sensitive gate and the dissolved oxygen sensitive gate are connected to the planar electrode through the epitaxial tabs and the wires respectively; the reference electrode, the pH sensitive gate and the dissolved oxygen sensitive gate are in the shape of fibers and are sandwiched between the double-layer diaphragms of the battery.

[0040] In some preferred implementation cases, the reference electrode includes: a fibrous conductive substrate; an Ag / AgCl layer attached to the surface of the conductive substrate; and a solid electrolyte layer coated on the surface of the Ag / AgCl layer.

[0041] In some preferred implementation cases, the conductive substrate is carbon fiber or carbon nanotube fiber. The Ag / AgCl layer is coated on the surface of the conductive substrate by electrochemical reduction or silver paste, and then the silver on the surface is chlorinated by chemical reagents or electrochemical methods. The solid electrolyte is a PVB ethanol solution containing high concentrations of potassium chloride or sodium chloride.

[0042] The reference electrode of the present invention has good stability in various electrolytes, and can therefore provide a stable reference potential for various electrochemical tests. The flexible fiber substrate and miniaturized size make it suitable for various narrow spaces, and the preparation method is simple and has the advantage of low cost and large-scale preparation.

[0043] In some preferred implementation cases, the dissolved oxygen sensitive grid includes: a fibrous conductive substrate; an oxygen reduction catalyst layer attached to the surface of the conductive substrate; an inner encapsulation layer coated on the surface of the oxygen reduction catalyst layer; and an outer encapsulation layer coated on the surface of the inner encapsulation layer. As a further preference, the conductive substrate is carbon fiber or carbon nanotube fiber. The oxygen reduction catalyst is platinum metal nanoparticles with a particle size of less than or equal to 10 nm. The inner encapsulation layer is a Nafion encapsulation layer; and the outer encapsulation layer is a PDMS encapsulation layer. As a further preference, when preparing the coating, Nafion is first applied to the electrode on which the oxygen reduction catalyst is deposited and dried, and then the electrode is further encapsulated with a PDMS solution.

[0044] The above-mentioned dissolved oxygen sensitive gate of the present invention has the advantages of high selectivity, high sensitivity, good robustness and low cost for large-scale preparation. In addition, the dissolved oxygen sensitive gate of the present invention is designed with inner and outer double packaging layers, which has the advantages that the inner packaging layer is conducive to oxygen reaction, repels negatively charged substances, reduces interference, and provides hydrogen ions in oxygen reduction reaction (for example, Nafion is selected as the inner packaging layer), and the outer packaging layer is conducive to protecting the inner packaging layer while also improving the mechanical properties (for example, PDMS is selected as the outer packaging layer).

[0045] In some preferred implementation cases, the pH sensitive gate comprises: a fibrous conductive substrate; a pH sensitive material layer attached to the surface of the conductive substrate. As a further preferred embodiment, the conductive substrate is carbon fiber or carbon nanotube fiber. The pH sensitive material is selected from polyaniline, carbon nanotubes, graphene, zinc oxide, aluminum oxide, phthalocyanine or a composite material of the above pH sensitive materials. Polyaniline is electrodeposited on the surface of the conductive substrate by cyclic voltammetry. Electropolymerization is performed by cyclic voltammetry or fixed potential in an aniline monomer solution under a three-electrode system, or polyaniline is modified by drop coating on a conductive substrate. The electrode rinsed with deionized water is dried at room temperature overnight to obtain a pH sensitive gate. Alternatively, polyaniline or a composite material of carbon nanotubes, graphene, zinc oxide, aluminum oxide, phthalocyanine and the above pH sensitive materials is directly modified on a conductive substrate.

[0046] The pH sensitive electrode of the present invention has the advantages of high selectivity and high sensitivity for pH and can be prepared on a large scale at low cost.

[0047] In some preferred implementation cases, the substrate is selected from one or more of a fiber substrate, a silicon substrate, a soda-lime glass substrate, a polyethylene naphthalate substrate, and a polyimide substrate.

[0048] In some preferred implementation cases, the transistor is a commercially available metal oxide semiconductor field effect transistor (MOSFET), organic field effect transistor (OFET) or bipolar junction transistor (BJT).

[0049] Secondly, an application method of in-situ detection of dissolved oxygen and pH in aqueous battery electrolyte using the above sensor specifically comprises the following steps: 1) Connect the voltage / current reading interface to the portable wireless driving / testing device, connect the reference electrode, pH sensitive gate and dissolved oxygen sensitive gate to the gate of the transistor, and connect the source and drain of the transistor to the portable wireless driving / testing device.

[0050] 2) Single-channel tests were performed on the pH sensitive gate and the dissolved oxygen sensitive gate to obtain the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve.

[0051] 3) The aqueous battery is designed to have a double-layer diaphragm. During the battery assembly process, the reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid are sandwiched between the double-layer diaphragm.

[0052] 4) Connect the positive and negative electrodes of the battery to the battery testing system for cyclic charge and discharge; apply the same source-drain voltage and bias gate voltage to the transistor at the same time, and collect the current corresponding to the dissolved oxygen and pH; decouple and calibrate the collected different currents using the fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte inside the battery during the battery charging and discharging process.

[0053] In some preferred implementation cases, in step 2), the method for single-channel testing of the pH sensitive gate and the dissolved oxygen sensitive gate is: under the same source-drain voltage bias and gate voltage bias, the reference electrode and the pH sensitive gate, the reference electrode and the dissolved oxygen sensitive gate are immersed in gradient pH and gradient dissolved oxygen test solutions for testing, the channel current value is recorded, and the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve are fitted respectively.

[0054] In some preferred implementation cases, the gate voltage bias is set to -2 V to -1.75 V.

[0055] In some preferred implementation cases, in step 3), during the battery assembly process, the electrolyte is subjected to an initial value correction process before perfusion: the initial pH and initial dissolved oxygen of the electrolyte are tested and read, and the initial pH and initial dissolved oxygen are converted into corresponding initial current values ​​according to the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve. I DS in After the cycle charge and discharge in step 4) is completed, the initial current collected in step 4) is recorded as I DS 0 , the current collected in step 4) is based on the current value converted from the initial concentration, and the whole is multiplied by I DS in / I DS 0 , and obtain the corrected in-situ detection current. Finally, the in-situ detection current is converted through the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte inside the battery during the battery charging and discharging process. Specific embodiments Example 1 Using carbon fiber as the substrate, a reference electrode, a dissolved oxygen sensitive grid and a pH sensitive grid were prepared respectively, such as Figure 1 As shown, the specific steps include: Step 1: Preparation of reference electrode (CF-RE): Separate carbon fiber (CF) from carbon cloth and cut into 2 cm pieces. Then ultrasonically clean and dry the fiber with ethanol and deionized water for 10 minutes to remove grease and dust on the surface of the carbon fiber. Use a pipette to evenly coat the silver paste on the surface of the carbon fiber (50 μL cm -1 ) and annealed at 60 degrees Celsius for 12 hours to obtain CF / Ag(CA). CA was then placed in 0.01 mol L -1 KCl / 0.1 mol L -1 CF / Ag / AgCl (CAC) was obtained by chlorinating the silver on the electrode surface using cyclic voltammetry (CV) in a three-electrode system in HCl, with a voltage window of -0.15 to 1.05 V, a scan rate of 50 mV s and a cycle number of 50 mV s -1 and 10. CAC was then encapsulated with a solid electrolyte to improve the stability of the reference electrode. 79.1 mg of PVB powder, 74.5 mg of potassium chloride, and 1 mL of ethanol were mixed and stirred overnight to obtain a solid electrolyte slurry, which was then evenly coated on the CAC surface (25 μL cm -1 ) and dried at 60 °C for 12 h. Finally, the dried electrode was placed in a potassium chloride solution (3 mol L -1 ) for 12 hours, rinsed with deionized water three times and dried at room temperature overnight to obtain CF-RE.

[0057] Step 2: Preparation of dissolved oxygen sensitive grid, separate the carbon fiber from the carbon cloth and cut it into 2 cm. Then ultrasonically clean and dry the fiber with ethanol and deionized water for 10 minutes in turn to remove grease and dust on the surface of the carbon fiber. Prepare 10 mL of 2.5 mM chloroplatinic acid aqueous solution and 10 ml of 25 mM sodium borohydride aqueous solution, soak the carbon fiber in 10 mL chloroplatinic acid aqueous solution (1 mM) for about 30 minutes, add 1 mL of sodium borohydride solution to the chloroplatinic acid solution, stir vigorously for 60 minutes, and then refrigerate at 5°C for 12 hours. Take out the carbon fiber, wash and dry it with deionized water to obtain CFs / Pt. Finally, prepare 0.5 wt% Nafion ethanol solution and 20 wt% p-xylene PDMS solution, first coat CFs / Pt with Nafion, dry at 60°C for 60 minutes, then coat with PDMS, and dry at 60°C for 60 minutes.

[0058] Step 3: Preparation of pH sensitive gate (CPa.), separate the carbon fiber from the carbon cloth and cut into 2 cm pieces. Then ultrasonically clean and dry the fiber with ethanol and deionized water for 10 minutes to remove grease and dust on the surface of the carbon fiber. Electrodeposit polyaniline on the surface of the carbon fiber using cyclic voltammetry. Dissolve 0.1 mL of aniline solution in 10 mL of 1 molL -1 In the above solution, carbon fiber was used as the working electrode, platinum electrode as the counter electrode, Ag / AgCl (saturated potassium chloride) as the reference electrode, and the reaction temperature was 50 mV s -1 The scan rate was cyclically scanned between 0.2 V and 1.2 V for 10 cycles. The electrode was rinsed with deionized water and dried at room temperature overnight to obtain a pH sensitive electrode (CPa.).

[0059] In other embodiments, the fibrous conductive substrate can be, but is not limited to, carbon fiber, carbon nanotube fiber, etc. For the pH sensitive gate, electropolymerization is carried out in an aniline monomer solution by cyclic voltammetry or fixed potential under a three-electrode system, and polyaniline is drop-coated on the conductive substrate for modification, or polyaniline or carbon nanotubes, graphene, zinc oxide, aluminum oxide, phthalocyanine and composite materials of the above sensitive materials are directly modified on the conductive substrate. For the dissolved oxygen sensitive gate, platinum nanoparticles with oxygen reduction activity can be directly modified on the fiber substrate by chemical reduction, and other materials with oxygen reduction catalytic activity can also be modified by atomic layer deposition or thermal evaporation. For the reference electrode, the modification method of silver can be by coating silver paste or electrochemical deposition, and the chlorination can be carried out by cyclic voltammetry or direct chlorination by chemical reagents.

[0060] Figure 2 A scanning electron microscope image of a dissolved oxygen sensitive grid based on carbon fiber obtained according to the above preparation method is shown, which shows the morphological changes of the dissolved oxygen sensitive grid during the preparation process.

[0061] When the dissolved oxygen sensitive gate is working, at a negative potential, the oxygen in the solution diffuses to the vicinity of the dissolved oxygen sensitive gate, and the oxygen spontaneously undergoes a reduction reaction on the electrode surface under the catalytic action of platinum nanoparticles. The reaction rate of oxygen reduction is much lower than the diffusion rate of dissolved oxygen in the solution to the vicinity of the electrode surface. The entire process is diffusion controlled, and the logarithm of the dissolved oxygen concentration is positively correlated with the open circuit potential.

[0062] Example 2 During the in-situ detection of the soft-pack aqueous battery, the reference electrode (made in Example 1), the pH sensitive grid (made in Example 1), and the dissolved oxygen sensitive grid (made in Example 1) are implanted as follows: Figure 3 shown.

[0063] The structure of soft-pack aqueous battery is as follows Figure 3 (left) including: Battery negative electrode 301; Battery positive electrode current collector 302; A positive electrode material 303 disposed on the positive electrode current collector 302; A double-layer battery separator 304 disposed between the battery positive electrode and the battery negative electrode; A reference electrode 305-1, a pH sensitive grid 305-2 and a dissolved oxygen sensitive grid 305-3 implanted between the double-layer battery separator; The electrode lug 306 is used to lead out the reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid.

[0064] The structure of the sensor is as follows Figure 3 (right) including: A substrate 307; an integrated circuit chip 308 including a transistor, a voltage / current reading interface 309 and a planar electrode 310 disposed on the substrate; like Figure 3 (Left) The reference electrode, pH sensitive grid, and dissolved oxygen sensitive grid are shown.

[0065] Wherein: the voltage / current reading interface is connected to the integrated circuit chip and the planar electrode respectively; the reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid are connected to the planar electrode respectively through the epitaxial tabs and the wires.

[0066] Example 3 An application method for in-situ detection of dissolved oxygen and pH in an aqueous battery electrolyte using a sensor (Example 2) specifically comprises the following steps: 1) Connect the voltage / current reading interface to the portable wireless driver / test device (TruEbox, 02CM, LinkZill Co., Ltd), connect the reference electrode, pH sensitive gate and dissolved oxygen sensitive gate to the gate of the transistor, and connect the source and drain of the transistor to the portable wireless driver / test device.

[0067] 2) Perform single-channel tests on the pH sensitive gate and dissolved oxygen sensitive gate respectively to obtain the pH-current fitting curve and dissolved oxygen concentration-current fitting curve. Specifically: Under the same source-drain voltage bias (-1.5 V) and gate voltage bias (-2 V), the reference electrode and the pH-sensitive gate, as well as the reference electrode and the dissolved oxygen-sensitive gate were immersed in test solutions with different gradient pH values ​​for testing. The channel current values ​​were recorded and the pH-current fitting curve was obtained by fitting. Figure 5 3. The real-time response gradient curve (left) and the dissolved oxygen concentration-current fitting curve (right) of the pH value measurement process in Example 3 of the present invention.

[0068] Under the same source-drain voltage bias (-1.5 V) and gate voltage bias (-2 V), the reference electrode and the pH-sensitive gate, as well as the reference electrode and the dissolved oxygen-sensitive gate were immersed in test solutions with different gradient dissolved oxygen concentrations for testing. The channel current values ​​were recorded, and the dissolved oxygen concentration-current fitting curve was obtained by fitting. Figure 4 3. The real-time response gradient curve (left) and pH-current fitting curve (right) of the dissolved oxygen detection process in Example 3 of the present invention.

[0069] 3) During the battery assembly process, the electrolyte is subjected to initial value correction before filling: the initial pH and initial dissolved oxygen of the electrolyte are tested and read, and the initial pH and initial dissolved oxygen are converted into corresponding initial current values ​​according to the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve. I DS in .like Figure 3 As shown, the reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid are sandwiched between the double-layer diaphragms, and then the electrolyte is poured in, the soft-pack battery is evacuated and the aluminum-plastic film is thermally sealed.

[0070] 4) Connect the positive and negative electrodes of the battery to a battery testing system (Land CT2001A, Wuhan Shenglan Electronic Technology Co., Ltd., Wuhan, China) for cyclic charge and discharge; apply the same source-drain voltage (-2 V) and bias gate voltage (-1.5 V) to the transistor, and collect the current corresponding to dissolved oxygen and pH. Figure 6 The figure shows a real photo of the soft-pack battery in Example 3 of the present invention being subjected to in-situ testing). After the cycle charge and discharge is completed, the collected initial current is recorded as I DS 0 , the collected current is based on the current value converted from the initial concentration, and the whole is multiplied by I DS in / I DS 0 , and obtain the corrected in-situ detection current. Finally, the in-situ detection current is decoupled and calibrated through the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte inside the battery during battery charging and discharging. All the above tests were completed at 25°C, and all data transmission and collection were carried out in real time via Bluetooth.

[0071] Figure 7The real-time channel circuit changes collected by the dissolved oxygen sensitive gate and pH sensitive gate during the three-time continuous charge and discharge process of the zinc ion soft pack battery of the present invention in the voltage window of 0.8 V – 1.8 V and the real-time change curves of dissolved oxygen and pH after fitting curve decoupling and initial value calibration are shown ( Figure 7 The upper middle picture shows dissolved oxygen. Figure 7 The lower middle figure is pH).

[0072] In summary, the technical solution of the present invention has the following beneficial effects: (1) The present invention implants a fibrous sensitive electrode into the battery, which can give full play to the advantages of electrochemical sensors such as high sensitivity, simple structure, easy miniaturization, diverse forms, and strong real-time monitoring capabilities, and can simultaneously realize real-time monitoring of dissolved oxygen and pH in the electrolyte.

[0073] (2) The present invention cleverly designs a single-layer diaphragm into a two-layer diaphragm, and implants the fiber electrode between the two layers of diaphragms during the battery preparation process. This is compatible with the battery preparation process and will not affect the operation of the battery, thereby enabling in-situ detection of the electrolyte composition inside the battery, and can more realistically reflect the changes in the electrolyte composition during the operation of the battery. This simple and accurate electrochemical in-situ detection method is of great significance for the mechanism research and performance optimization of the battery.

[0074] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0075] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A sensor for in-situ detection of dissolved oxygen and pH in an electrolyte, characterized in that include: substrate; An integrated circuit chip containing transistors, a voltage / current reading interface and a planar electrode disposed on a substrate; A reference electrode, a pH sensitive grid and a dissolved oxygen sensitive grid externally arranged on the substrate; in: The voltage / current reading interface is connected to the integrated circuit chip and the planar electrode respectively; The reference electrode, pH sensitive grid and dissolved oxygen sensitive grid are connected to the planar electrode through epitaxial tabs and wires respectively; The reference electrode, the pH sensitive grid and the dissolved oxygen sensitive grid are in the shape of fibers and are sandwiched between the double-layer diaphragms of the battery to be detected.

2. The sensor according to claim 1, characterized in that: The reference electrode comprises: A conductive substrate in a fibrous form; Ag / AgCl layer attached to the surface of the conductive substrate; A solid electrolyte layer coated on the surface of the Ag / AgCl layer.

3. The sensor according to claim 1, characterized in that: The dissolved oxygen sensitive grid comprises: A conductive substrate in a fibrous form; an oxygen reduction catalyst layer attached to the surface of the conductive substrate; An inner encapsulation layer coated on the surface of the oxygen reduction catalyst layer; An outer packaging layer coated on the surface of the inner packaging layer.

4. The sensor according to claim 1, characterized in that: The pH sensitive gate comprises: A conductive substrate in a fibrous form; A layer of pH sensitive material is attached to the surface of a conductive substrate.

5. The sensor according to claim 1, characterized in that: The substrate is selected from one or more of a fiber substrate, a silicon substrate, a soda-lime glass substrate, a polyethylene naphthalate substrate and a polyimide substrate.

6. The sensor according to claim 1, characterized in that: The transistor is a metal oxide semiconductor field effect transistor, an organic field effect transistor or a bipolar transistor.

7. An application method for in-situ detection of dissolved oxygen and pH in aqueous battery electrolyte using the sensor according to any one of claims 1 to 6, characterized in that include: 1) Connect the voltage / current reading interface to the portable wireless driving / testing device, connect the reference electrode, pH sensitive gate and dissolved oxygen sensitive gate to the gate of the transistor, and connect the source and drain of the transistor to the portable wireless driving / testing device; 2) Perform single-channel tests on the pH sensitive gate and the dissolved oxygen sensitive gate respectively to obtain the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve; 3) The aqueous battery is designed to be a double-layer diaphragm. During the battery assembly process, the reference electrode, pH sensitive grid and dissolved oxygen sensitive grid are sandwiched between the double-layer diaphragm; 4) Connect the positive and negative electrodes of the battery to the battery testing system for cyclic charge and discharge; at the same time, apply the same source-drain voltage and bias gate voltage to the transistor to collect current; decouple and calibrate the different collected currents using the fitting curve to obtain real-time data of dissolved oxygen and pH in the electrolyte.

8. The application method according to claim 7, characterized in that: In step 2), the method for single-channel testing of the pH sensitive gate and the dissolved oxygen sensitive gate is as follows: under the same source-drain voltage bias and gate voltage bias, the reference electrode and the pH sensitive gate, and the reference electrode and the dissolved oxygen sensitive gate are immersed in gradient pH and gradient dissolved oxygen test solutions for testing, and the channel current value is recorded, and the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve are fitted respectively.

9. The application method according to claim 7 or 8, characterized in that: The gate bias voltage is set to -2 V to -1.75 V.

10. The application method according to claim 1, characterized in that: In step 3), during the battery assembly process, the electrolyte is subjected to initial value correction before filling: the initial pH and initial dissolved oxygen of the electrolyte are tested and read, and the initial pH and initial dissolved oxygen are converted into corresponding initial current values ​​according to the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve. I DS in After the cycle charge and discharge in step 4) is completed, the initial current collected in step 4) is recorded as I DS 0 , the current collected in step 4) is based on the current value converted from the initial concentration, and the whole is multiplied by I DS in / I DS 0 , and obtain the corrected in-situ detection current. Finally, the in-situ detection current is converted through the pH-current fitting curve and the dissolved oxygen concentration-current fitting curve to obtain the real-time data of dissolved oxygen and pH in the electrolyte.

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