Dual-mode MEMS sensor for thermal runaway detection of lithium batteries and its preparation method

Abstract

The present invention discloses a dual-mode MEMS sensor for thermal runaway detection of a lithium battery and a preparation method thereof. The sensor comprises, from bottom to top, a silicon oxide support layer, a heating electrode and a sensing electrode, a silicon nitride isolation layer and a non-precious metal medium entropy alloy gas-sensitive film. The non-precious metal is any three of Fe, Co, Ni, Ti, V, and Cu. The preparation method of the sensor comprises fully ball-milling and mixing the non-precious metal to form a medium entropy alloy powder, and obtaining a gas-sensitive functional powder after heating. Glass powder, ethyl cellulose, and ethylene glycol are added to the gas-sensitive functional powder, and a gas-sensitive slurry is obtained after being fully mixed. The gas-sensitive slurry is dotted on the surface of the suspended membrane of the MEMS chip, and a stable gas-sensitive film is formed after heating, thereby obtaining a dual-mode MEMS sensor for thermal runaway detection of a lithium battery. The sensor does not contain precious metals, and can reduce the preparation cost.

Description

Technical Field

[0001] The present invention belongs to the field of sensing and measuring technology, and relates to a gas sensor that can be used for thermal runaway detection of a lithium battery, and specifically to a dual-mode MEMS sensor for thermal runaway detection of a lithium battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have become one of the most competitive electrochemical energy storage technologies in the field of electric vehicles and large-scale energy storage due to their high energy density, long cycle life, and environmental protection. Improper use such as mechanical damage, overcharging, and fast charging can cause thermal runaway of lithium-ion batteries, releasing flammable gases such as CO, H2, CH4, and C2H6, and accompanied by rapid heating of lithium batteries, leading to smoke, fire, and even explosion. The safety issue should not be underestimated. Therefore, monitoring of related flammable gases such as CO, H2, CH4, and C2H6 before thermal runaway smoke and fire is the most effective means of early safety warning for lithium-ion batteries. MEMS (micro-electromechanical system) gas sensors have great application potential in the field of lithium battery safety warning due to their small size, low power consumption, no device heat generation, and easy integration.

[0003] However, currently, MEMS combustible gas sensors usually use gas-sensitive functional materials doped with precious metals such as Pd and Pt, which are relatively expensive. In addition, in the case of thermal runaway of lithium batteries, the presence of electrolyte vapor makes existing combustible gas sensors easily interfered and send out erroneous signals. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a dual-mode MEMS sensor for thermal runaway detection of lithium batteries and a preparation method. Based on non-precious metal medium-entropy alloys and MEMS micro-hotplates, a semiconductor-catalytic combustion dual-mode MEMS combustible gas sensor with a power consumption of less than 7mW is developed. The sensor can be used for the detection of inorganic combustible gases such as hydrogen, carbon monoxide, methane, propane, etc. released by thermal runaway of lithium batteries, thereby realizing early safety warning of lithium-ion batteries.

[0005] The dual-mode MEMS sensor for thermal runaway detection of lithium batteries includes, from bottom to top, a silicon oxide support layer, a heating electrode and a sensing electrode, a silicon nitride isolation layer, and a non-precious metal medium entropy alloy gas-sensitive film. The non-precious metal is any three of Fe, Co, Ni, Ti, V, and Cu.

[0006] The method for preparing the non-precious metal medium entropy alloy gas-sensitive film comprises the following specific steps:

[0007] Step 1: Select any three metal powders from Fe, Co, Ni, Ti, V, and Cu and mix them in a mass ratio of 1:1:1, add zirconium oxide ball milling beads and anhydrous ethanol, and grind them. Filter and dry the ground solution, separate the zirconium oxide ball milling beads, obtain medium entropy alloy powder, and then perform heat treatment to obtain gas-sensitive functional powder.

[0008] Preferably, the metal powder has a diameter of 50 mm and a purity greater than 99.8%.

[0009] Preferably, the diameter of the zirconium oxide ball milling beads is 1 mm, and the mass ratio of the zirconium oxide ball milling beads to the metal powder is 15:1. The mass ratio of anhydrous ethanol to the metal powder is 1:1.

[0010] Preferably, a planetary ball mill is used for grinding for 10 to 24 hours at a rotation speed of 400 to 600 rpm; the obtained medium-entropy alloy powder is heat treated at a temperature of 400 to 600° C. for 2 to 4 hours to obtain a gas-sensitive functional powder.

[0011] Step 2: Mix the gas-sensitive functional powder obtained in step 1 with glass powder, ethyl cellulose and ethylene glycol, add zirconium oxide ball milling beads and grind, and after screening out the zirconium oxide ball milling beads, obtain a gas-sensitive slurry.

[0012] Preferably, the mixed gas-sensitive functional powder, glass powder, ethyl cellulose, and ethylene glycol are preliminarily ground, and then loaded into a ball mill jar together with zirconium oxide ball milling beads, and ground for 4 to 6 hours using a planetary ball mill at a rotation speed of 200 to 400 rpm.

[0013] Preferably, the mass ratio of the gas-sensitive functional powder, glass powder, ethyl cellulose and ethylene glycol is 10:(0.5-2):(4-6):100, and the mass ratio of the gas-sensitive functional powder to the zirconia ball milling beads is 1:15.

[0014] Step 3: spot-coat and heat the gas-sensitive slurry obtained in step 2 to obtain a gas-sensitive medium-entropy alloy film.

[0015] The preparation method of the dual-mode MEMS sensor for thermal runaway detection of lithium batteries includes the following specific steps:

[0016] Step 1: Use a MEMS chip with an integrated micro-hotplate as a sensor electrode chip, and apply the gas-sensitive slurry to the suspended film surface of the MEMS chip by a pneumatic dispenser.

[0017] Preferably, the dispensing pressure of the pneumatic dispensing machine is controlled at 0.4~0.5k Pa, the inner diameter of the dispensing needle is 150~160mm, the outer diameter is 280~320 mm, and the dispensing time for each time is 0.2~0.3 s.

[0018] Step 2: After the dispensing is completed, the device is heated and aged by a micro-hotplate integrated in the MEMS chip, thereby forming a stable gas-sensitive medium-entropy alloy film on the chip surface to obtain the semiconductor-catalytic combustion dual-mode MEMS combustible gas sensor.

[0019] Preferably, the heating aging adopts a step temperature mode, the temperature of the micro-hot plate is controlled at 100, 200, 300, 400, and 500° C. in sequence, and heating is performed at each temperature for 30 to 120 min to obtain the semiconductor-catalytic combustion dual-mode MEMS combustible gas sensor.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present application uses any three metal powders of non-precious metals Fe, Co, Ni, Ti, V, and Cu as raw materials to prepare medium-entropy alloy oxides containing three elements such as FeCoNi, FeCoCu, and FeNiTi as gas-sensitive functional materials for combustible gases. It does not contain precious metals and can reduce the preparation cost of the sensor.

[0022] 2. This application utilizes the catalytic effect of non-precious metals on combustible gases to realize the gas-sensing function detection of semiconductor chemical sensitivity and catalytic combustion dual modes of a single MEMS sensor, which can realize full-range detection of combustible gases and meet the requirements for accurate detection of combustible gases released by thermal runaway of lithium batteries.

[0023] 3. The prepared medium-entropy alloy gas-sensitive film can obtain good semiconductor chemical sensitivity and catalytic combustion gas detection performance in the temperature range of 100 ~150 °C, so that the MEMS combustible gas sensor of this application consumes only 7mW of power under the optimal working state.

[0024] 4. The MEMS combustible gas sensor based on non-precious metal medium entropy alloy in this application has almost no response to organic volatile gases such as ethanol and lithium battery electrolyte vapor, and can accurately determine the thermal runaway state of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a dual-mode MEMS sensor chip for thermal runaway detection of a lithium battery prepared in an embodiment;

[0026] Figure 2 Comparison of the sensitivity of the sensor in Example 1 to different detection gases in semiconductor gas sensing mode;

[0027] Figure 3 Comparison of the sensitivity of the sensor in Example 1 to different detection gases in the catalytic combustion gas sensing mode;

[0028] Figure 4The response / recovery characteristics of the sensor in Example 2 to different concentrations of H2 in the two gas-sensing modes of semiconductor-catalytic combustion;

[0029] Figure 5 The response / recovery characteristics of the sensor in Example 2 to different concentrations of CH4 in the two gas-sensing modes of semiconductor-catalytic combustion;

[0030] Figure 6 The response / recovery characteristics of the sensor in Example 3 to different CO concentrations in the two gas-sensing modes of semiconductor-catalytic combustion. DETAILED DESCRIPTION

[0031] The present invention will be further explained below with reference to the accompanying drawings;

[0032] Example 1

[0033] This embodiment prepares a dual-mode MEMS sensor for thermal runaway detection of lithium batteries, and the specific steps are as follows:

[0034] Step 1: Fe, Co, and Ni metal powders with a diameter of 50 mm and a purity greater than 99.8% are loaded into a ball mill at a mass ratio of 1:1:1, and zirconium oxide ball milling beads with a diameter of 1 mm and anhydrous ethanol are added. The mass ratio of the zirconium oxide ball milling beads to the metal powder is 15:1, and the mass ratio of anhydrous ethanol to the metal powder is 1:1. The metal powder particles are reduced to 2-3 mm by ball milling with a planetary ball mill at a speed of 400 rpm for 10 h, and the various metal powders are mixed evenly and disorderly to form a medium entropy alloy. The solution obtained by ball milling is filtered and dried, and the zirconium oxide ball milling beads are separated to obtain medium entropy alloy powder, which is heat treated at 600 ° C for 4 h to obtain gas-sensitive functional powder.

[0035] Step 2: Take the gas-sensitive functional powder obtained in step 1, mix it with glass powder, ethyl cellulose and ethylene glycol in a mass ratio of 10:1:4:100, transfer it to a ball mill after preliminary grinding, and put zirconia ball milling beads with a diameter of 1 mm into the ball mill together. The mass ratio of zirconia ball milling beads to gas-sensitive functional powder is 15:1. Use a planetary ball mill for ball milling for 4 hours at a rotation speed of 200 rpm to obtain a gas-sensitive slurry.

[0036] Step 3: Use a MEMS chip with an integrated microheater as the sensor electrode chip, and use a pneumatic dispensing machine to apply the gas-sensitive slurry to the middle interdigitated electrode area of ​​the MEMS chip. The dispensing pressure of the pneumatic dispensing machine is controlled at 0.4 kPa, the inner diameter of the dispensing needle is 160 mm, the outer diameter is 320 mm, and the dispensing time for each time is 0.2 s.

[0037] Step 4: After the dispensing is completed, the device is heated and aged by a micro-hotplate integrated in the MEMS chip. The temperature is controlled to be 100, 200, 300, 400, and 500 °C in sequence, and heated for 120 min at each temperature, thereby forming a stable non-precious metal medium entropy alloy gas-sensitive film on the chip surface. Figure 1 The low-power MEMS combustible gas sensor shown includes, from bottom to top, a silicon oxide support layer 1, a heating electrode and a sensing electrode 2, a silicon nitride isolation layer, and a non-precious metal medium-entropy alloy gas-sensitive film 4. The sensor uses the interdigital electrodes of the silicon-based suspended film integrated microheater to output the electrical signal of the semiconductor gas-sensitive response of the sensitive layer, and the microheater electrode is used as a catalytic combustion heating unit to output the electrical signal of the catalytic combustion gas-sensitive response of the sensitive layer.

[0038] The dynamic gas distribution method is used to measure the sensitivity characteristics of the sensor, and the calculation method of sensitivity is defined as:

[0039]

[0040] in, I s Indicates the output current value of the sensor in a certain concentration of the gas to be tested. I 0 Indicates the output current value of the sensor in clean gas, C Indicates the concentration of the detected gas in ppm.

[0041] The sensitivity of the sensor prepared in this embodiment to different detection gases in semiconductor gas sensing mode and catalytic combustion gas sensing mode was tested. The results are as follows Figure 2 and Figure 3 As shown in the figure, in both modes, the sensor exhibits good response characteristics to CO, H2, CH4, and C2H6 gases, and has almost no response to lithium battery electrolyte vapor DMC, which indicates that the sensor has a specific response to the combustible gas in the thermal runaway scenario of the lithium battery and will not be interfered by the electrolyte vapor; under this working condition, the power consumption of the sensor is about 7 mW.

[0042] Example 2

[0043] This embodiment prepares a dual-mode MEMS sensor for detecting thermal runaway of a lithium battery. The difference from Embodiment 1 is that Fe, Co, and Ti metal powders are used to prepare a medium-entropy alloy, and the medium-entropy alloy powder obtained after drying is heat treated at 400°C for 4 hours; the gas-sensitive functional powder is mixed with glass powder, ethyl cellulose, and ethylene glycol in a mass ratio of 10:0.5:4:100.

[0044] The semiconductor gas-sensitive response and catalytic combustion gas-sensitive response current changes of the sensor prepared in this embodiment to different concentrations of H2 were tested. Figure 4As shown in Figure 2, the semiconductor gas-sensing response and catalytic combustion gas-sensing response current changes to different concentrations of CH4 are shown in Figure 2. Figure 5 Under this operating condition, the power consumption of the sensor is about 6.5 mW.

[0045] Example 3

[0046] In this embodiment, a dual-mode MEMS sensor for thermal runaway detection of a lithium battery is prepared. The difference from Embodiment 1 is that Fe, V, and Cu metal powders are used to prepare a medium-entropy alloy, and the medium-entropy alloy powder obtained after drying is heat treated at 400°C for 4 h; the gas-sensitive functional powder is mixed with glass powder, ethyl cellulose, and ethylene glycol in a mass ratio of 10:1:5:100; the dispensing pressure of the pneumatic dispensing machine is controlled at 0.5 kPa, and the dispensing time for each time is 0.3 s.

[0047] The semiconductor gas-sensitive response and catalytic combustion gas-sensitive response current changes of the sensor prepared in this embodiment to different concentrations of CO were tested. Figure 6 shown.

[0048] Example 4

[0049] In this embodiment, a dual-mode MEMS sensor for thermal runaway detection of a lithium battery is prepared. The difference from Embodiment 1 is that Fe, Co, and Ti metal powders are used to prepare a medium-entropy alloy, and the medium-entropy alloy powder obtained after drying is heat treated at 600°C for 4 h; the gas-sensitive functional powder is mixed with glass powder, ethyl cellulose, and ethylene glycol in a mass ratio of 10:1:5:100; the inner diameter of the needle of the pneumatic dispensing machine is 150 mm and the outer diameter is 280 mm, and the dispensing time for each time is 0.3 s.

[0050] Example 5

[0051] In this embodiment, a dual-mode MEMS sensor for thermal runaway detection of a lithium battery is prepared. The difference from Embodiment 1 is that Cu, Co, and Ti metal powders are selected to prepare a medium-entropy alloy, and a planetary ball mill is used to grind for 24 h at a rotation speed of 400 rpm; the medium-entropy alloy powder obtained after drying is heat treated at 500°C for 3 h; the gas-sensitive functional powder is mixed with glass powder, ethyl cellulose, and ethylene glycol in a mass ratio of 10:1.5:5:100; the dispensing pressure of the pneumatic dispensing machine is controlled at 0.5 kPa, the inner diameter of the needle is 160 mm, the outer diameter is 320 mm, and the dispensing time for each time is 0.2 s.

Claims

1. A dual-mode MEMS sensor for thermal runaway detection of a lithium battery comprises, from bottom to top, a silicon oxide support layer, a heating electrode, a sensing electrode, and a silicon nitride isolation layer, characterized in that: It also includes a non-precious metal medium-entropy alloy gas-sensitive film located on the surface of the silicon nitride isolation layer; the non-precious metal is any three of Fe, Co, Ni, Ti, V, and Cu; The sensor uses semiconductor chemical sensitivity and catalytic combustion dual-mode gas sensing functions to detect combustible gases released by thermal runaway of lithium batteries. The combustible gases include hydrogen, carbon monoxide, methane and propane. The preparation method of the dual-mode MEMS sensor for detecting thermal runaway of a lithium battery is as follows: Step 1, select any three metal powders of Fe, Co, Ni, Ti, V, and Cu and mix them in a mass ratio of 1:1:1, add zirconium oxide ball milling beads and anhydrous ethanol and grind them; filter and dry the ground solution, separate the zirconium oxide ball milling beads, obtain medium entropy alloy powder, and then perform heat treatment to obtain gas-sensitive functional powder; Step 2, mixing the gas-sensitive functional powder obtained in step 1 with glass powder, ethyl cellulose and ethylene glycol, adding zirconium oxide ball milling beads and grinding, and screening out the zirconium oxide ball milling beads to obtain a gas-sensitive slurry; Step 3: Use a MEMS chip with an integrated micro-hotplate as a sensor electrode chip, and apply the gas-sensitive slurry to the suspended film surface of the MEMS chip by a pneumatic dispenser; Step 4: After the dispensing is completed, the device is heated and aged by a micro-hotplate integrated in the MEMS chip, so as to form a stable gas-sensitive medium-entropy alloy film on the surface of the chip, and obtain the dual-mode MEMS sensor for thermal runaway detection of the lithium battery; The heat aging adopts a step temperature mode, and the temperature of the micro-hot plate is controlled at 100, 200, 300, 400, and 500 ° C in sequence, and heating is performed at each temperature for 30 to 120 min.

2. The dual-mode MEMS sensor for thermal runaway detection of a lithium battery as claimed in claim 1, characterized in that: The diameter of the zirconium oxide ball milling beads is 1 mm, and the mass ratio of the zirconium oxide ball milling beads to the metal powder is 15:1; the mass ratio of anhydrous ethanol to the metal powder is 1:

1.

3. The dual-mode MEMS sensor for thermal runaway detection of a lithium battery as claimed in claim 1, characterized in that: In step 1, a planetary ball mill is used for grinding for 10 to 24 hours at a rotation speed of 400 to 600 rpm; the obtained medium-entropy alloy powder is heat treated at a temperature of 400 to 600° C. for 2 to 4 hours to obtain a gas-sensitive functional powder.

4. The dual-mode MEMS sensor for detecting thermal runaway of a lithium battery as claimed in claim 1, characterized in that: In step 2, the mixed gas-sensitive functional powder, glass powder, ethyl cellulose, and ethylene glycol are preliminarily ground, and then loaded into a ball mill together with zirconia ball milling beads and ground for 4 to 6 hours using a planetary ball mill at a rotation speed of 200 to 400 rpm; the mass ratio of the gas-sensitive functional powder to the zirconia ball milling beads is 1:

15.

5. The dual-mode MEMS sensor for thermal runaway detection of a lithium battery as claimed in claim 1, characterized in that: The mass ratio of the gas-sensitive functional powder, glass powder, ethyl cellulose and ethylene glycol is 10:(0.5-2):(4-6):

100.

6. The dual-mode MEMS sensor for detecting thermal runaway of a lithium battery as claimed in claim 1, characterized in that: The dispensing pressure of the pneumatic dispensing machine is controlled at 0.4~0.5k Pa, the inner diameter of the dispensing needle is 150~160 mm, the outer diameter is 280~320 mm, and the dispensing time for each time is 0.2~0.3 s.

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