Pole piece integrated temperature sensor and preparation method thereof

Abstract

The invention relates to the technical field of lithium battery manufacturing, in particular to a pole piece integrated temperature sensor and a preparation method, the pole piece integrated temperature sensor is directly integrated on a lithium ion battery negative electrode current collector, and the sensor sequentially comprises a transition layer, a first electrode layer, a second electrode layer, a third electrode layer and a fourth electrode layer from bottom to top, the sensing layer is a rare earth doped tantalum oxynitride film deposited on the transition layer; the packaging layer is a single-layer graphene thin film deposited on the sensing layer, and the graphene thin film is of a mesoporous structure with the pore diameter being 2-5 nm. According to the invention, the rare earth doped tantalum oxynitride high-sensitivity sensing layer and the graphene mesoporous encapsulation layer are directly integrated on the battery current collector, so that zero-distance and in-situ real-time monitoring of the heat production core in the battery is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a pole piece integrated temperature sensor and a preparation method. BACKGROUND

[0002] As a mainstream electrochemical energy storage device, the improvement of the fast-charging performance of lithium ion batteries is the key to meeting the urgent needs of the fields of electric vehicles, portable electronic devices, etc. However, with the continuous increase of the charging rate, the heat production rate in the battery increases sharply, and due to the uneven current distribution, material interface thermal resistance and poor heat dissipation conditions, a highly uneven internal temperature field is formed. The temperature of the local "hot spot" (such as the tab root, the middle of the winding core) can be much higher than the average temperature, which can easily induce side reactions such as lithium precipitation and electrolyte decomposition, and even cause thermal runaway, which seriously restricts the safety boundary and application promotion of the ultra-fast charging technology.

[0003] Real-time and accurate monitoring of the internal temperature of the battery, especially the temperature of the dangerous "hot spot" area, is the premise of implementing effective thermal management and preventing thermal runaway. At present, the industry generally adopts the scheme of attaching negative temperature coefficient (NTC) thermistors and other sensors to the surface of the battery shell. Although this scheme is simple in process, the sensor is separated from the internal heat production core by multiple materials, and there is a large thermal conduction path and accumulated interface thermal resistance. This leads to a serious lag (often up to several seconds) of the measurement signal, which cannot capture the millisecond to second level of instantaneous sharp temperature rise in the fast-charging process, and the measured temperature value is the shell temperature after serious averaging and attenuation, which is much lower than the internal real peak temperature, and cannot locate the "hot spot", constituting the core blind area of thermal safety management. In addition, some technical solutions attempt to introduce thermocouple cables and the like into the internal part of the battery cell through special structures. For example, Chinese patent CN221057494U discloses a battery with an internal temperature sensing wire. Although this scheme extends the measurement point inward, the introduced cable occupies the limited space of the battery cell as a "foreign object", reduces the energy density, and brings long-term reliability risks such as lead breakage, insulation failure, and internal short circuit initiation. In addition, the packaging structure itself has thermal resistance, and the response speed is still limited, and it is difficult to be placed in the key areas such as the tab root where the mechanical stress is large and the space is limited. In order to further realize in-situ monitoring, researchers have proposed a scheme of depositing a metal thin film (such as platinum, nickel) on the current collector as a temperature sensor. For example, Chinese patent CN114914566A discloses a lithium battery with a platinum thin film temperature sensor integrated in the internal part of the battery cell. However, such materials usually have a low temperature coefficient of resistance (TCR) (such as platinum, about 0.39% / K), and have insufficient sensitivity to small temperature rises; they have poor chemical stability in the strong reducing electrolyte environment of the battery and are prone to corrosion; and the metal thin film has insufficient toughness and is difficult to adapt to the repeated expansion and contraction of the electrode material during charging and discharging, leading to rapid degradation or failure of performance.

[0004] In summary, the prior art is difficult to meet the stringent requirements of internal temperature accurate monitoring of super-fast charging lithium-ion batteries in multiple dimensions such as high sensitivity, fast response, long-term environmental stability, compatibility with battery manufacturing process and structure, etc. SUMMARY

[0005] The purpose of the present application is to provide an electrode sheet integrated temperature sensor and a preparation method, which can be integrated with the electrode, directly contact the heat source, and have high sensitivity and high reliability, so as to fundamentally break through the bottleneck of thermal safety monitoring of super-fast charging.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The present application provides an electrode sheet integrated temperature sensor, which is directly integrated on the lithium-ion battery negative current collector, and the sensor comprises from bottom to top: The transition layer is a tantalum nitride film deposited on the surface of the current collector; The sensing layer is a rare earth doped tantalum oxynitride film deposited on the transition layer; The packaging layer is a single-layer graphene film deposited on the sensing layer, and the graphene film has a mesoporous structure with a pore size of 2-5 nm.

[0007] Preferably, the chemical formula of the sensing layer is Ta 1-x RE x (N 1-y O_ y ) 1±δ , wherein RE is selected from one or more of Er, Yb and Tm, and 0.05 ≤ x ≤ 0.15, 0.10 ≤ y ≤ 0.35, -0.08 ≤ δ ≤ +0.10.

[0008] Preferably, the average resistance temperature coefficient of the sensing layer at 25℃ is not less than 2.0 % / K.

[0009] Preferably, the thickness of the transition layer is 10-30 nm, the thickness of the sensing layer is 1.0-1.2 μm, and the sensing layer has a vertically grown nanopillar microstructure.

[0010] Preferably, the current collector is a copper foil, and the electrical signal of the sensor is led out through the tab via the current collector.

[0011] The present application also discloses a preparation method of the electrode sheet integrated temperature sensor as described, comprising the following steps: S1: depositing a tantalum nitride transition layer on the battery current collector; S2: depositing a rare earth doped tantalum oxynitride sensing layer on the substrate on which the transition layer is deposited; S3: growing a single-layer graphene encapsulation layer on the substrate with the sensing layer deposited thereon; S4: etching the graphene encapsulation layer to form mesopores with a pore size of 2-5 nm.

[0012] 7. The preparation method of claim 6, wherein step S1 is specifically: depositing a transition layer of tantalum nitride on the surface of the current collector at a temperature of 100-150 DEG C in a mixed atmosphere of argon and nitrogen by using a direct current pulse magnetron sputtering process.

[0013] Preferably, step S2 is specifically: introducing a mixed gas of argon, nitrogen and oxygen, and depositing a rare earth-doped tantalum oxynitride sensing layer with a chemical formula of Ta RE O N by using a direct current and radio frequency power co-sputtering tantalum target and rare earth metal target at a temperature of 150±10 DEG C. 1-x RE x (N 1-y O_ y ) 1±δ wherein RE is selected from one or more of Er, Yb and Tm.

[0014] Preferably, step S3 is specifically: growing a single-layer graphene on the surface of the sensing layer by using a plasma-enhanced chemical vapor deposition method under a methane / argon / hydrogen atmosphere at a temperature of 450±20 DEG C.

[0015] Preferably, step S4 is specifically: etching the graphene encapsulation layer by using a femtosecond laser to form uniform mesopores with a pore size of 2-5 nm; and the method further comprises step S5: coating a negative active material layer on the encapsulation layer to complete the integration of the sensor and the negative electrode plate.

[0016] The present application has the following beneficial effects: compared with the existing continuous welding and passive cooling technology, the present application directly integrates a rare earth-doped tantalum oxynitride high-sensitivity sensing layer and a graphene mesopore encapsulation layer on a battery current collector, thereby realizing zero-distance and in-situ real-time monitoring of the internal heat generation core of the battery. This solution fundamentally eliminates the delay of several seconds caused by the heat conduction path in the traditional external temperature measurement scheme, and the response time can reach milliseconds, which can capture the instantaneous sharp temperature rise in the fast charging process without lag. At the same time, the unique material system and encapsulation structure effectively resist electrolyte corrosion and electrochemical-mechanical stress impact, ensuring the high reliability of the sensor in long-term cycling. The precise, fast and stable internal temperature signal obtained makes the battery thermal management upgrade from the "passive alarm" mode relying on external distorted data to the "active intervention" mode based on the internal real heat state, providing a key data basis for inhibiting lithium precipitation, preventing local overheating and implementing intelligent fast charging strategy, and significantly improving the safety boundary and performance upper limit of lithium ion batteries in super-fast charging applications. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The principle schematic diagram of the magnetron sputtering deposition process of the tantalum nitride (TaN) transition layer provided by the present application is shown in the figure; Figure 2 The principle schematic diagram of the co-sputtering deposition process of the rare earth doped tantalum oxynitride (RE-TaON) sensing layer provided by the present application is shown in the figure; Figure 3 The preparation flowchart of the graphene mesoporous encapsulation layer (G-MEL) provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings and examples. It should be pointed out that the following examples are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0019] The present application provides a preparation method of an electrode sheet integrated temperature sensor, which is characterized by sequentially constructing a transition layer, a sensing layer and an encapsulation layer on a battery current collector, and finally integrating with a negative active material layer to form an integrated electrode sheet that can directly monitor the internal temperature of the battery. The method specifically comprises the following steps: First step, current collector pretreatment. Provide a copper foil current collector for a battery, and sequentially clean the surface with acetone, ethanol and deionized water by ultrasonic cleaning to remove surface oil stains and impurities. After cleaning, the copper foil surface is bombarded with argon plasma for a short time (such as 30-60 seconds) in a vacuum chamber to further activate the surface and enhance the adhesion of the subsequent thin film.

[0020] Second step, depositing a tantalum nitride (TaN) transition layer. Place the pretreated copper foil in the chamber of a magnetron sputtering device, and evacuate to a base vacuum of not higher than 5.0×10 -4 Pa. Introduce a mixed gas of argon (Ar) and nitrogen (N2) (for example, Ar: 80 sccm, N2: 20 sccm) into the chamber, and maintain the working gas pressure at about 0.4 Pa. Heat the substrate (copper foil) to 100-150℃ (for example, 120℃), and sputter a tantalum (Ta) target using a direct current pulse power source, with a power density controlled at 4 W / cm 2 , deposit for 10-60 minutes to form a dense tantalum nitride (TaN) film with a thickness of about 10-30 nm (for example, 20 nm). The transition layer can effectively block the diffusion of copper atoms to the functional layer and enhance the interfacial bonding strength.

[0021] Third step, deposition of rare earth doped tantalum oxynitride (RE-TaON) sensing layer. After the deposition of the transition layer, the chamber is kept in vacuum and the reactive gases are switched to a mixture of argon, nitrogen and oxygen (O2). By adjusting the flow ratio of the three gases (e.g. Ar: 70 sccm, N2: 15-25 sccm, O2: 1-10 sccm), the oxygen content (y value) in the sensing layer can be precisely controlled. The substrate temperature is stabilized at 150±10°C. Meanwhile, direct current power is turned on to sputter the tantalum target and radio frequency power is turned on to sputter the rare earth metal target (e.g. erbium target). By controlling the power density of the two targets (e.g. Ta target: 2.7-3.3 W / cm 2 , Er target: 0.5-2.5 W / cm 2 ) and deposition time (e.g. 60 minutes), the rare earth doping amount (x value) can be regulated and a film with vertically grown nanopillar structure and microcrack network is formed. The final deposition results in a sensing layer with a thickness of about 1.0-1.2 μm and a chemical formula of Ta 1-x RE x (N 1-y O_ y ) 1±δ , where 0.05≤x≤0.20, 0.05≤y≤0.35.

[0022] Fourth step, preparation of graphene mesoporous encapsulation layer (G-MEL). The substrate with the deposited sensing layer is transferred to a plasma enhanced chemical vapor deposition (PECVD) device. At a temperature of 450±20°C, a mixture of methane (CH4), argon and hydrogen (H2) is introduced as carbon source to grow a single-layer graphene film covering the surface of the sensing layer. Subsequently, a femtosecond laser system (wavelength 1030 nm) is used to selectively etch the graphene layer, and by precisely controlling the laser energy density (e.g. ~10 12 W / cm 2 ) and scanning parameters, a mesoporous array with uniform pore size of 2-5 nm (e.g. 3 nm) is formed on the graphene layer. This structure can effectively block the corrosion of electrolyte molecules and harmful ions on the sensing layer, while allowing lithium ions to pass quickly, with minimal impact on heat conduction.

[0023] In the fifth step, the negative active material layer is integrated and a signal is led out. A non-contact ultrasonic spraying process is used to coat the negative electrode slurry (such as a uniform mixture of artificial graphite, a conductive agent, and a binder) on the surface of the packaging layer. The spraying power is 10-15 W, and the nozzle spacing is 10-15 cm to avoid mechanical damage. After coating, the complete negative electrode sheet is formed through segmented drying (such as 80°C pretreatment and 120°C curing) and controlled pressure rolling. The electrical signal of the sensor is led from the sensing area to the test pad at the edge of the electrode sheet through the metal lead (such as Ti / Au) formed on the current collector by photolithography and etching process, and finally connected to the special signal collection tab through welding, realizing the external output of the temperature signal.

[0024] To verify the technical effects of the present application, the following specific examples and comparative examples are listed for illustration. Examples 1-10 are all prepared by the above method, the main difference being the process gas ratio and target power during the deposition of the sensing layer in the third step, so as to obtain sensing materials with different compositions (x, y values). Comparative examples 1-3 are used to illustrate the necessity of the key features of the present application.

[0025] Example 1 (1) Preparation of positive electrode sheet P1 The positive active material LFP, the conductive agent SP, and the binder PVDF are uniformly mixed and dispersed in the NMP solvent in a certain mass ratio to obtain a uniform slurry, wherein the solid components include 95w% of the positive active material LFP, 2w% of the conductive agent SP, and 3w% of the binder PVDF. The positive electrode mixed slurry is uniformly coated on both sides of the aluminum foil to obtain the positive electrode sheet P1.

[0026] (2) Preparation of temperature sensor S1 and integrated negative electrode current collector a. Transition layer deposition: First, the copper foil current collector is pretreated (cleaning, plasma activation). Then, in a chamber with a base vacuum not less than 5.0 × 10 -4 Pa, argon (80 sccm) and nitrogen (20 sccm) are introduced, and a 20 nm thick tantalum nitride (TaN) transition layer is deposited at a working gas pressure of 0.4 Pa and a substrate temperature of 120°C by direct current pulse sputtering (power density 4 W / cm 2 ).

[0027] b. Sensing layer deposition: After the TaN deposition is completed, the vacuum is maintained, and a mixed gas of argon (70 sccm), nitrogen (20 sccm), and oxygen (5 sccm) is introduced. The substrate temperature is raised to 150°C, and the tantalum target is sputtered by direct current power (power density 3 W / cm 2 ) and the erbium target is sputtered by radio frequency power (power density 1.2 W / cm 2), deposited for 60 minutes, forming a 1.2 μm thick layer with a chemical formula of Ta0. 92 Er0. 08 (N0.8O0.2)1. 00 rare-earth doped tantalum oxynitride sensing layer.

[0028] c. Encapsulation layer preparation: The above substrate was transferred to a PECVD device and a monolayer of graphene was grown at 450°C under a methane / argon / hydrogen atmosphere. Subsequently, the graphene surface was treated with a femtosecond laser (wavelength 1030 nm, power density 10 12 W / cm 2 ) to form a uniform mesoporous structure with a pore diameter of 3 nm.

[0029] d. Signal lead preparation and tab integration To achieve point monitoring of the negative tab root temperature, after encapsulation, photolithography and microfabrication techniques were used to form the sensor electrode, lead and test pad in this area at one time. Specifically: A layer of metal (such as titanium / gold) was deposited on the entire surface of the substrate by vacuum evaporation or sputtering.

[0030] Through a photolithography and etching process, the metal layer was patterned, simultaneously defining: 1) a microelectrode pattern located in the sensing area of the tab root.

[0031] 2) metal leads leading out from the electrodes.

[0032] 3) test pads located in the blank area of the current collector edge.

[0033] Finally, the test pads were connected to a special signal acquisition tab through soldering, achieving independent and accurate measurement of the hotspot temperature at the tab root.

[0034] (3) Preparation of negative electrode sheet N1 The negative active material artificial graphite Gr, the conductive agent SP, the binder SBR, and the dispersant CMC are uniformly mixed and dispersed in a pure water solvent to obtain a uniform negative electrode slurry, wherein the solid content includes 95 w% of the negative active material Gr, 2 w% of the conductive agent SP, 1.8 w% of the binder SBR, and 1.2 w% of the dispersant CMC. The negative electrode slurry is uniformly coated on the surface of the copper foil by using a non-contact ultrasonic spraying process; wherein the power of the ultrasonic spraying is 10-15 W, the distance between the nozzle and the substrate is 10-15 cm, and the spraying rate is 5-10 mL / min, so as to avoid damage to the underlying sensor structure caused by mechanical contact; after the coating is completed, the electrode piece is dried in sections, first pretreated at 80°C for 5 minutes, and then solidified at 120°C for 20 minutes, and the transmission tension is controlled to be below 50 N / m during the drying process; finally, the electrode piece is subjected to a roll reduction, and the roll pressure is controlled to be between 500-1000 N / mm, so as to ensure the structural integrity of the integrated sensor while ensuring the densification of the negative electrode material. The negative electrode piece N1 is obtained.

[0035] (4) Preparation of a lithium ion battery After the positive electrode piece P1 and the negative electrode piece N1 are punched into small pieces, a Z-shaped stack is formed to obtain a bare cell, and aluminum tabs and copper-nickel plated tabs are respectively punched out. The bare cell is packaged using an aluminum plastic film, and is subjected to high-temperature vacuum baking at 90°C for 24 hours, and then is filled with electrolyte. The electrolyte is a lithium hexafluorophosphate electrolyte containing 1M, and the solvent is a mixed solvent of ethylene carbonate / dimethyl carbonate / 1,2-propylene carbonate-1:1:1 (volume ratio). After packaging, the battery is subjected to formation and aging to obtain a square soft package battery with a length of 180 mm, a width of 90 mm, and a thickness of 7 mm, which is denoted as C1.

[0036] Example 2 The battery C2 is prepared according to the battery preparation method in Example 1, except that the RE-TaON-SL1 rare earth-doped tantalum oxynitride is introduced into argon, nitrogen, and oxygen as working gases, wherein the argon flow rate is 70 sccm, the nitrogen flow rate is 22.5 sccm, and the oxygen flow rate is 2.5 sccm; a direct current power source is used to sputter a tantalum target, and the power density is 3.2 W / cm 2 , and a radio frequency power source is used to sputter an erbium target, and the power density is 0.8 W / cm 2 .

[0037] Example 3 A battery C3 was prepared according to the battery preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 18.75 sccm, and the flow rate of oxygen was 6.25 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 2.9 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 1.8 W / cm 2 .

[0038] Example 4 A battery C4 was prepared according to the battery preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 21.25 sccm, and the flow rate of oxygen was 3.75 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 3.1 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 1.5 W / cm 2 .

[0039] Example 5 A battery C5 was prepared according to the battery preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 17.5 sccm, and the flow rate of oxygen was 7.5 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 2.8 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 2.1 W / cm 2 .

[0040] Example 6 A battery C6 was prepared according to the battery preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 20.5 sccm, and the flow rate of oxygen was 4.5 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 3.1 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 1.0 W / cm 2 .

[0041] Example 7 A cell C7 was prepared according to the cell preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 23.75 sccm, and the flow rate of oxygen was 1.25 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 3.3 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 0.5 W / cm 2 .

[0042] Example 8 A cell C8 was prepared according to the cell preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 16.25 sccm, and the flow rate of oxygen was 8.75 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 2.7 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 2.5 W / cm 2 .

[0043] Example 9 A cell C9 was prepared according to the cell preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 17.5 sccm, and the flow rate of oxygen was 7.5 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 2.9 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 1.5 W / cm 2 .

[0044] Example 10 A cell C10 was prepared according to the cell preparation method in Example 1, except that the RE-TaON-SL1 rare earth doped tantalum oxynitride was fed with argon, nitrogen and oxygen as working gases, wherein the flow rate of argon was 70 sccm, the flow rate of nitrogen was 18 sccm, and the flow rate of oxygen was 5 sccm, and a tantalum target was sputtered by a direct current power supply with a power density of 2.9 W / cm 2 , and an erbium target was sputtered by a radio frequency power supply with a power density of 1.8 W / cm 2 .

[0045] Comparative Example 1 A comparative battery C11 was prepared according to the battery fabrication method described in Example 1. The difference between the method for preparing the integrated temperature sensor and that of Example 1 is that the sensing layer is a tantalum nitride thin film without rare earth doping and oxygen doping. Specifically, after depositing the transition layer, the reaction gas was adjusted to pure nitrogen, and the sputtering of the erbium target was stopped. The tantalum nitride layer was deposited only by DC magnetron sputtering in an argon-nitrogen atmosphere. Its thickness was consistent with that of the sensing layer in Example 1, approximately 1.0 μm, and a graphene mesoporous encapsulation layer was also prepared on the surface.

[0046] Comparative Example 2 The comparative battery C12 was prepared according to the battery preparation method described in Example 1. The difference between the preparation method of the integrated temperature sensor and that of Example 1 is that after the rare earth-doped tantalum oxynitride sensing layer is deposited, the preparation step of the graphene mesoporous encapsulation layer is omitted, so that the sensing layer is directly exposed to the electrolyte environment.

[0047] Comparative Example 3 The comparative battery C13 was prepared according to Example 1, but differed from Example 1 in that it did not integrate any internal temperature sensor, but instead adopted an industry-standard external temperature monitoring solution. Specifically, after the aluminum-plastic film encapsulation of the cell was completed, a commercially available negative temperature coefficient (NTC) thermistor was precisely attached to the area on the outside of the cell corresponding to the root of the negative electrode tab using a high thermal conductivity adhesive.

[0048] For ease of understanding, the key design information for step b of the temperature sensor S1 above is summarized in the following table: Table 1. Summary of key design information for step b in temperature sensor S1 of the examples and comparative examples

[0049] The C1-C13 batteries described in the above embodiments and comparative examples were tested as follows: 1. Temperature coefficient of resistance (TCR, denoted as...) The resistance value of the sample with the sensing layer was measured by placing it in a high-low temperature probe station and measuring the change of its resistance value with temperature using a four-wire voltage measurement method within a temperature range of -20℃ to 80℃. The average TCR value was calculated using formula (1) with the resistance value Rr at 25℃ as the reference.

[0050] (1) Where Rt is the resistance value measured at temperature t, and Rr is the resistance value at a reference temperature (usually 25℃). Substituting data from multiple temperature points into the formula for linear fitting, the slope of the resulting fitted line is the average TCR of the sensor. 2. Ultra-fast charging test procedure: Equipment: A high-precision battery testing system is used to control charging and discharging, and a high-speed data acquisition card (sampling rate ≥100 kHz) is used to record sensor signals; external thermocouple signals are recorded by the built-in channel of the testing system (sampling rate 1 Hz).

[0051] Environment: The test was conducted in a constant temperature chamber, with the temperature stabilized at 25.0±0.5℃.

[0052] Test procedure: After the battery is allowed to reach thermal equilibrium at the test temperature, it is then fast-charged from 10% SOC to 80% SOC using a constant current at a 6C rate. All data recording devices are simultaneously activated the instant the charging command is issued.

[0053] Peak temperature rise (peak ΔT): The acquired sensor voltage signal is converted into a temperature-time curve T_internal(t) using Ohm's law and a pre-calibrated RT curve. Peak ΔT is the difference between the maximum value of T_internal(t) and the initial temperature, used to assess the maximum thermal risk. Specifically, the peak ΔT for C13 is taken from the external NTC thermocouple reading, while the peak ΔT for other schemes is taken from the internal sensor reading.

[0054] Response delay comparison: Align the temperature curves of the internal sensor and the external thermocouple, and calculate the time difference between the two from the start of charging to reaching the same temperature rise ratio (e.g., 50%), so as to intuitively demonstrate the lag of external monitoring.

[0055] Note: The intrinsic response delay of C1-C12 is calibrated by independent step temperature testing. This test mainly verifies its fast response advantage at the system level. The ">4s" of C13 is the system response delay relative to the charging command in the ultra-fast charging test.

[0056] 3. Static stability evaluation test of the sensor in the electrolyte environment This test aims to evaluate the chemical and interfacial stability of the sensor under long-term static conditions in an electrolyte simulating a real battery environment, in order to predict its long-term operational reliability. Under a constant temperature of 45°C, the prepared sensor sample was completely immersed in a lithium-ion battery electrolyte of a specific composition (where the lithium hexafluorophosphate concentration was 1M, and the solvent was a 1:1:1 volume ratio mixture of ethylene carbonate, dimethyl carbonate, and propylene carbonate) for 30 days. During this period, the resistance value of the sample was monitored periodically using a high-precision resistance meter, and its relative change rate (ΔR / R0) with respect to the initial resistance (R0) was recorded. By analyzing the evolution trend of this parameter over 30 days, it is possible to directly and effectively determine whether the sensing functional layer and encapsulation structure can resist the chemical corrosion and solvent molecule penetration of the electrolyte, and whether the interfaces between the layers remain stable.

[0057] 4. Room temperature cycle life test procedure 1) Test Conditions: Ambient Temperature: 25℃ ± 1℃ constant temperature environment. Cyclic System: Constant current-constant voltage (CC-CV) charge-discharge mode. Charging: Charge at a constant current of 0.5C to the upper limit voltage (e.g., 3.65V), then charge at a constant voltage until the current drops to the cutoff point of 0.05C. Discharging: Discharge at a constant current of 0.5C to the fixed cutoff voltage of 2.0V. Cycle Interval: A 10-minute rest period is set between each charge-discharge cycle.

[0058] 2) Key Nodes and Data Acquisition Process: Initial Benchmark Test (Cycle 0): Before the cycle begins, accurately measure the initial capacity (C0) of the battery and the initial TCR value (TCR0) of the integrated temperature sensor. Periodic Interruption Test: When the cycle count reaches preset nodes such as 250, 500, 750, and 1000 cycles, interrupt the cycle and perform the following operations: Battery Capacity Calibration: Perform 3 standard charge-discharge cycles and take the average discharge capacity as the capacity retention rate (SOH) for that node. Sensor TCR Calibration: Using a high-precision temperature control chamber, remeasure the sensor's resistance-temperature curve within a specific temperature range (e.g., 20℃-50℃), calculate its current TCR value, and record the percentage decay relative to TCR0.

[0059] 3) Life End and Data Analysis End-of-life determination: When the battery's capacity retention rate decays to 70% of the initial capacity C0, the cycle life is determined to have ended, and the total number of cycles N@70% SOH is recorded.

[0060] Table 2 Comparison of material composition and core performance parameters of different TaErNO temperature sensor solutions

[0061] As shown in the table above, the comparison between Comparative Example 1 (C11) and Example 1 (C1) demonstrates that the ordinary tantalum nitride (TaN) film lacking rare earth element doping has a significantly lower temperature coefficient of resistance (TCR) (0.38% / K vs 2.95% / K), resulting in insufficient temperature monitoring sensitivity. It cannot accurately reflect the actual micro-temperature rise inside the battery and is difficult to meet the extremely high requirements for accurate early warning of thermal runaway in ultra-fast charging scenarios.

[0062] The comparison between Comparative Example 2 (C12) and Example 1 (C1) demonstrates that the rare-earth-doped tantalum oxynitride (TaErNO) sensing layer, lacking the protection of a graphene mesoporous encapsulation layer (G-MEL), undergoes severe corrosion and performance degradation (resistance drift +258%) in the electrolyte environment, and completely fails after a limited number of charge-discharge cycles, failing to guarantee reliable monitoring throughout the battery's entire lifespan. The comparison between Comparative Example 3 (C13) and Example 1 (C1) demonstrates that the externally mounted monitoring scheme used in this comparative example suffers from a response delay of several seconds (>4 s) due to the long heat conduction path and high interfacial thermal resistance. Furthermore, the measured peak temperature rise (8.2℃) significantly underestimates the actual internal thermal risk of the battery (the internal monitoring value in Example 1 was 16.5℃). This delayed and distorted temperature signal prevents the Battery Management System (BMS) from obtaining an effective early warning window before thermal runaway occurs, thus constituting a core safety hazard in ultra-fast charging applications.

[0063] In summary, neither Comparative Examples 1 nor 2 can simultaneously meet the requirements of high sensitivity and high stability. Only the overall technical solution combining rare earth doping and graphene mesoporous encapsulation provided by this invention (as in Example 1) can successfully solve the technical challenge of real-time, accurate, and long-term reliable monitoring of the internal temperature of ultra-fast charging lithium-ion batteries, achieving unexpected technical results and demonstrating outstanding substantive features and significant progress.

[0064] Example 1 (Ta0). 92 Er0. 08 (N0.8O0.2)1. 00 Taking this as an example, comparing traditional built-in thermocouples with the novel temperature sensor created in this patent, the electrode-integrated temperature sensor provided by this invention achieves a generational performance leap in monitoring the internal temperature of lithium-ion batteries compared to external thermocouples. Its essential advantage lies in realizing a paradigm shift from "indirect, lagging, and distorted external estimation" to "direct, real-time, and accurate internal visualization." Specifically, this manifests in: 1. Spatial resolution advantage: The sensor is directly positioned in the core heat-generating area, accurately revealing for the first time the true thermal state of the battery's interior, especially key areas such as the base of the electrode tabs and the middle of the core. The measured local temperature rise is significantly higher than external measurements, completely eliminating signal attenuation and distortion caused by heat conduction paths, and solving the core pain point of external monitoring severely underestimating internal thermal risks. 2. Time response advantage: The sensor's response time reaches the millisecond level, more than two orders of magnitude faster than external thermocouples, enabling real-time, zero-delay tracking of instantaneous temperature changes during fast charging, providing the battery management system with the possibility of proactive thermal runaway warnings. III. Safety Enhancement: This technology provides an unprecedented direct data source for lithium plating monitoring and thermal safety management in ultra-fast charging scenarios, enabling battery management strategies to be upgraded from passive responses based on external fuzzy speculation to active intervention based on internal real conditions, greatly improving the safety limit of the battery system and the fast charging performance boundary.

Claims

1. An electrode-integrated temperature sensor, characterized in that, Directly integrated onto the negative electrode current collector of a lithium-ion battery, the sensor comprises, from bottom to top: The transition layer is a tantalum nitride thin film deposited on the surface of the current collector; The sensing layer is a rare earth-doped tantalum oxynitride thin film deposited on the transition layer; The encapsulation layer is a single-layer graphene film deposited on the sensing layer, the graphene film having a mesoporous structure with a pore size of 2-5 nm.

2. The electrode-integrated temperature sensor according to claim 1, characterized in that, The chemical formula of the sensing layer is Ta 1-x RE x (N 1-y O_ y ) 1±δ , where RE is selected from one or more of Er, Yb, and Tm, and 0.05 ≤ x ≤ 0.15, 0.10 ≤ y ≤ 0.35, -0.08 ≤ δ ≤ +0.

10.

3. The electrode-integrated temperature sensor according to claim 2, characterized in that, The average temperature coefficient of resistance of the sensing layer at 25°C is not less than 2.0% / K.

4. The electrode-integrated temperature sensor according to claim 1, characterized in that, The thickness of the transition layer is 10-30 nm, the thickness of the sensing layer is 1.0-1.2 μm, and the sensing layer has a vertically grown nanocolumnar microstructure.

5. The electrode-integrated temperature sensor according to claim 1, characterized in that, The current collector is a copper foil, and the electrical signal of the sensor is led out through the current collector via the tab.

6. A method for fabricating an electrode-integrated temperature sensor as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Deposit a tantalum nitride transition layer on the battery current collector; S2: Deposit a rare earth-doped tantalum oxynitride sensing layer on a substrate on which the transition layer has been deposited; S3: Grow a monolayer graphene encapsulation layer on a substrate on which the sensing layer is deposited; S4: Etch the graphene encapsulation layer to form mesopores with a pore size of 2-5 nm.

7. The preparation method according to claim 6, characterized in that, Step S1 specifically involves depositing a tantalum nitride transition layer on the surface of the current collector using a DC pulsed magnetron sputtering process at a temperature of 100-150°C in a mixed atmosphere of argon and nitrogen.

8. The preparation method according to claim 6, characterized in that, Step S2 specifically involves: introducing a mixed gas of argon, nitrogen, and oxygen; using a DC and RF power supply for co-sputtering of a tantalum target and a rare earth metal target; and depositing a gas with the chemical formula Ta at a temperature of 150±10°C. 1-x RE x (N 1-y O_ y ) 1±δ The rare earth-doped tantalum oxynitride sensing layer, wherein RE is selected from one or more of Er, Yb, and Tm.

9. The preparation method according to claim 6, characterized in that, Step S3 specifically involves growing a single layer of graphene on the surface of the sensing layer using plasma-enhanced chemical vapor deposition at 450±20 °C in a methane / argon / hydrogen atmosphere.

10. The preparation method according to claim 6, characterized in that, Step S4 specifically involves using a femtosecond laser to etch the graphene encapsulation layer to form uniform mesopores with a pore size of 2-5 nm. The method also includes step S5: coating the encapsulation layer with a negative electrode active material layer to complete the integrated integration of the sensor and the negative electrode sheet.

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