Lithium ion battery module disaster monitoring platform in operation state

Abstract

The utility model provides a lithium ion battery module disaster monitoring platform in a running state, which comprises a sealing test cabin, a flue gas analyzer, an infrared thermal imager and a camera, a heating coil is arranged on the inner wall of the box to ensure the consistency of the initial temperature in the box body and reduce test errors, and two lifting frames are arranged in the sealing test cabin to ensure the consistency of the initial temperature in the box body. A lithium battery module and a current sensor are arranged on the two lifting frames respectively, the lithium battery module is connected with the current sensor, and a voltage monitoring device, a resistance monitoring device and a temperature monitoring device are arranged outside the sealing test cabin. The voltage monitoring device and the resistance monitoring device are connected to the lithium battery module and used for monitoring the cell voltage and the overall resistance of the lithium battery module. According to the utility model, various operation conditions are introduced, and measures of temperature monitoring, voltage monitoring, resistance monitoring, short-circuit current monitoring and the like are combined so as to realize omnibearing and high-precision monitoring of abnormal conditions of the module.

Description

Technical Field

[0001] The utility model relates to a test monitoring device for a lithium-ion battery module, in particular to a disaster monitoring platform for a lithium-ion battery module in an operating state. Background Technique

[0002] Lithium-ion batteries are widely used in electric vehicles, energy storage power stations and other fields due to their high energy density and excellent cycling performance. While lithium-ion batteries are representatives of advanced energy sources, there are still significant risks. Under various external abuse inductions, they are prone to a large release of their own energy, leading to thermal runaway and then forming a thermal disaster. In addition, thermal runaway of lithium-ion batteries frequently occurs during operation. According to the statistics of "Research Progress on Power Battery Safety", in 2020, the proportion of new energy vehicles in the driving state during the fire state was the highest at 40%, and 60% of the new energy vehicles with fire accidents were equipped with ternary lithium-ion batteries. To meet the requirements of multiple scenarios, while increasing its own energy density, multiple single cells are combined into a module in series and parallel to meet the requirements for voltage and capacity. In this scenario, such as battery control system failures, battery management system degradation, and short circuits in module connection components, if a single battery in the module undergoes thermal runaway, it will cause the thermal runaway of the module to spread, ultimately resulting in the fire and explosion of the battery system.

[0003] At present, the monitoring and early warning platforms for lithium-ion batteries are mainly applied to single cells in an open-circuit state, and the monitored parameters are mostly temperature and gas monitoring, while ignoring the monitoring of relevant electrical parameters such as voltage and resistance, thus unable to meet the requirements of early warning. The existing module monitoring and early warning platforms only monitor temperature and voltage, and are mainly applied to series modules. When a thermal runaway occurs in the internal battery cells of a parallel module, a large short-circuit current will instantaneously appear inside the module, thereby promoting the process of internal heat diffusion in the module. To sum up, the thermal runaway of parallel modules is more aggressive, but there is still a lack of an electrothermal monitoring and early warning platform for ternary lithium battery parallel modules in an operating state. Content of the Utility Model

[0004] The technical problem to be solved by the utility model is to provide a disaster monitoring platform for a lithium-ion battery module in an operating state in view of the above-mentioned deficiencies of the prior art. This device platform introduces various operating conditions and combines means such as temperature monitoring, voltage monitoring, resistance monitoring, and short-circuit current monitoring to aim at achieving all-round and high-precision monitoring of abnormal conditions of the module.

[0005] To solve the above technical problems, the technical solution adopted by the present utility model is: a disaster monitoring platform for a lithium-ion battery module in an operating state, characterized in that it includes a sealed test chamber, a flue gas analyzer, an infrared thermal imager, and a camera. Two lifting frames are installed in the sealed test chamber, and a lithium battery module and a current sensor are respectively arranged on the two lifting frames. The lithium battery module is connected to the current sensor. A voltage monitoring device, a resistance monitoring device, and a temperature monitoring device are arranged outside the sealed test chamber. The voltage monitoring device and the resistance monitoring device are connected to the lithium battery module to monitor the cell voltage and the overall resistance of the lithium battery module.

[0006] Preferably, the volume of the sealed test chamber is 1 m 3 , and the thickness is 5 cm. Double flanges are installed on the hatch door of the sealed test chamber to improve safety. Heating coils are installed on the inner wall of the sealed test chamber to maintain the internal temperature of the chamber in a constant state and reduce test errors. A pressure relief valve and a flue gas probe are installed on the top of the sealed test chamber. The pressure relief valve is used to prevent gas combustion and explosion. The flue gas probe is a telescopic flue gas probe, and the probe length is adjusted according to the selected cell size to realize early monitoring and warning of gas. The flue gas probe is connected to the flue gas analyzer. A plurality of wire passing holes are opened on the side wall of the sealed test chamber. A transparent observation window is embedded on one side surface of the sealed test chamber, and an optical glass window is embedded on the transparent observation window. The camera is arranged outside the sealed test chamber and is directly opposite the transparent observation window. The infrared thermal imager is arranged outside the sealed test chamber and is directly opposite the optical glass window.

[0007] Preferably, a display platform, a discharge platform, and a DC power supply are also arranged outside the sealed test chamber. The temperature monitoring device includes a temperature sensor and a temperature display device. The temperature sensor is arranged inside the lithium battery module to monitor the temperature of the cells. The discharge platform is connected to the lithium battery module through a 60A test line. The DC power supply is connected to the current sensor to supply power to the current sensor.

[0008] Preferably, the lithium battery module is composed of multiple cells connected in parallel. The current sensor is a fluxgate current sensor. The lithium battery module is fixed on the lifting frame by a 10 mm thick steel plate. An asbestos heat insulation layer is arranged between the lithium battery module and the steel plate. A 300W PI film heating sheet is attached to the surface of the lithium battery module. The temperature sensor includes two types: K-type thermocouple and ring thermocouple. Two K-type thermocouples with a diameter of 1 mm are symmetrically attached to the center of the large surface of each cell, and M6 ring thermocouples are arranged at the positive and negative electrodes of the cell.

[0009] Preferably, the current sensor is connected to a current data acquisition card, and the display platform is connected to the current data acquisition card, the voltage monitoring device, the resistance monitoring device, and the temperature monitoring device to display the monitoring data in real time.

[0010] Preferably, the flue gas analyzer can monitor and analyze the concentrations of O2, CO, CO2, and CH4.

[0011] Preferably, the current sensor is fixed in an acrylic box, and an asbestos heat insulation layer is provided on the outer layer of the acrylic box.

[0012] The utility model has the following advantages compared with the prior art:

[0013] 1. The utility model couples three key monitoring data of heat, electricity, and gas, can monitor the parameters during the normal operation of the module, and judge whether there are abnormal phenomena in the module according to temperature, voltage, resistance, and short-circuit current. If there are abnormal phenomena, the operating circuit can be cut off in time to minimize the damage to other modules. At the same time, heat, electricity, gas, and video under abnormal conditions are recorded for subsequent analysis of the accident cause.

[0014] 2. The utility model introduces various operating conditions, and combines means such as temperature monitoring, voltage monitoring, resistance monitoring, and short-circuit current monitoring to achieve all-round and high-precision monitoring of the abnormal conditions of the module. In addition, according to the thermal runaway mechanism and relevant test data, the catastrophic process of the parallel modules in the operating state is divided into stages, and the thresholds of temperature, voltage, and short-circuit current in each stage are set as early warning signals.

[0015] The following further describes the present utility model in detail with reference to the drawings and embodiments. Description of the Drawings

[0016] Figure 1 is the overall architecture schematic diagram of the present utility model.

[0017] Figure 2 is the connection structure schematic diagram of the lithium battery module and the current sensor in the present utility model.

[0018] Description of the Reference Numerals:

[0019] 1 - Sealing test chamber; 2 - Flue gas analyzer; 3 - Infrared thermal imager;

[0020] 4 - Camera; 5 - Lifting frame; 6 - Lithium battery module;

[0021] 7 - Current sensor; 8 - Voltage monitoring device; 9 - Resistance monitoring device;

[0022] 10 - Flue gas probe; 11 - Threading hole; 12 - Transparent observation window;

[0023] 13 - Optical glass window; 14 - Display platform; 15 - Discharge platform;

[0024] 16 - DC power supply; 17 - Temperature monitoring device; 18 - Current data acquisition card. Detailed implementation mode

[0025] As Figure 1 and Figure 2 shown, the utility model includes a sealing test chamber 1, a flue gas analyzer 2, an infrared thermal imager 3 and a camera 4. Two lifting frames 5 are installed in the sealing test chamber 1. A lithium battery module 6 and a current sensor 7 are respectively arranged on the two lifting frames 5. The lithium battery module 6 is connected to the current sensor 7. A voltage monitoring device 8, a resistance monitoring device 9 and a temperature monitoring device 17 are arranged outside the sealing test chamber 1. The voltage monitoring device 8 and the resistance monitoring device 9 are connected to the lithium battery module 6 to monitor the cell voltage and the overall resistance of the lithium battery module 6. The voltage monitoring device 8 and the resistance monitoring device 9 are a voltage sensor and a resistance sensor respectively.

[0026] In this embodiment, the volume of the sealing test chamber 1 is 1m 3 , and the thickness is 5 cm. Double flanges are installed on the cabin door of the sealing test chamber 1 to improve safety. Heating coils are installed on the inner wall of the sealing test chamber to maintain a constant temperature inside the chamber and reduce test errors. A pressure relief valve and a flue gas probe 10 are installed on the top of the sealing test chamber 1. The pressure relief valve is used to prevent gas explosion. The flue gas probe 10 is a telescopic flue gas probe, and the probe length is adjusted according to the selected cell size to realize early monitoring and warning of gas. The flue gas probe 10 is connected to the flue gas analyzer 2. A plurality of wire passing holes 11 are opened on the side wall of the sealing test chamber 1 for passing wires. A transparent observation window 12 is embedded on one side of the sealing test chamber 1. An optical glass window 13 is embedded on the transparent observation window 12. The camera 4 is arranged outside the sealing test chamber 1 and is directly opposite to the transparent observation window 12. The infrared thermal imager 3 is arranged outside the sealing test chamber 1 and is directly opposite to the optical glass window 13.

[0027] In this embodiment, a display platform 14, a discharge platform 15 and a ±15V DC power supply 16 are further arranged outside the sealing test chamber 1. The temperature monitoring device 17 includes a temperature sensor and a temperature display device. The temperature sensor is arranged inside the lithium battery module 6 to monitor the temperature of the cell. The discharge platform 15 is connected to the lithium battery module 6 through a 60A test line. The DC power supply 16 is connected to the current sensor 7 to supply power to the current sensor 7.

[0028] In this embodiment, the lithium battery module 6 is composed of three battery cells connected in parallel. The current sensor 7 is a fluxgate current sensor. The lithium battery module 6 is fixed on the lifting frame 5 by a 10-mm thick steel plate. An asbestos heat insulation layer is provided between the lithium battery module 6 and the steel plate. A 300-W PI film heating sheet is attached to the surface of the lithium battery module 6. The temperature sensor includes two types: K-type thermocouple and M6 ring thermocouple. Two K-type thermocouples with a diameter of 1 mm are symmetrically attached to the center of the large surface of each battery cell, and M6 ring thermocouples are provided at the positive and negative electrodes of the battery cell.

[0029] In this embodiment, the current sensor 7 is connected to a current data acquisition card 18. The display platform is connected to the current data acquisition card 18, the voltage monitoring device 8, the resistance monitoring device 9, and the temperature monitoring device 17 to display the monitoring data in real time.

[0030] In this embodiment, the flue gas analyzer 2 can monitor and analyze the concentrations of O2, CO, CO2, and CH4.

[0031] In this embodiment, the current sensor 7 is fixed in an acrylic box, and an asbestos heat insulation layer is provided on the outer layer of the acrylic box.

[0032] This embodiment is mainly aimed at the disaster monitoring of lithium-ion battery modules in the operating state, meeting the requirements of actual engineering applications. The test platform mainly triggers the parallel modules in the operating state through an external heat source and monitors the electrothermal parameters, and proposes a three-level early warning mode based on the electrothermal parameter indicators. The operating methods are mainly divided into four modes: constant current discharge, constant voltage discharge, constant resistance discharge, and constant power discharge, and the test standards of electric vehicles such as NEDC, WLTP, and CLTC can be introduced as operating conditions, aiming to fit the real application scenarios. During operation, an external 300W heat source is introduced to trigger an orderly thermal runaway inside the module. The entire disaster process will be recorded by a high-speed camera and an infrared thermal imager, combined with the dynamic coupling relationship of temperature, voltage, resistance, and short-circuit current, and the self-generated heat temperature of the battery is calibrated by an adiabatic accelerated calorimeter to divide the thresholds of the three-level early warning. The electrothermal thresholds set in each stage are shown in Table 1. The level III early warning is the thermal runaway gestation stage, where the temperature threshold is 77°C, the voltage drop = 25%, the resistance increase ≥ 0.2%, and the current transferred between modules = total discharge current / 2; the level II early warning is the single-cell thermal runaway stage, where the temperature threshold is 130°C, the voltage drop > 25%, the resistance decrease ≥ 8%, and the current transferred between modules > total discharge current / 2; the level I early warning is the module thermal diffusion stage, where the temperature threshold is 130°C, the voltage drop = 100%, and the current transferred between modules = 0. In addition, electrothermal physical models are built in each stage to quantitatively analyze the electrochemistry heat. The electrochemical-thermal physical model is embedded in the thermal runaway gestation stage, i.e., the level III early warning, to quantify the electrochemistry heat. The above heat generation data mainly serves the power management of this platform and can adjust the operating current and cut-off voltage. The electro-thermal physical model is embedded in the single-cell thermal runaway stage to quantify the Joule heat generated by the intervention of the short-circuit current to evaluate the importance of the short-circuit current in the single-cell thermal runaway process. The power management platform adjusts the initial state of charge SOC of the battery according to the Joule heat data, thereby minimizing the short-circuit current between the batteries and reducing the role of the electrochemistry heat in this stage.

[0033] Table 1 Electrothermal Thresholds for Each Early Warning Level

[0034]

[0035] Thermal runaway incubation stage: Based on the thermal runaway mechanism and experimental tests with an adiabatic accelerating calorimeter, the SEI film will decompose and reshape at 77°C, and the lithium battery enters the self-heating stage. At the same time, the voltage will show a small fluctuation during this stage. When the temperature is between 77°C and 130°C, the negative electrode reacts with the electrolyte to generate a series of reducing gases. These gases penetrate through the separator and enter the positive electrode side, which can damage the crystal structure of the positive electrode. At the same time, the low-boiling-point solvents DMC and EMC in the electrolyte evaporate in this temperature range to increase the internal pressure of the battery. At 130°C, the separator will collapse under the action of high temperature and internal pressure, and the battery is about to enter the thermal runaway stage, that is, the temperature rise > 1°C / s and the instantaneous pressure drop value > 25%. Therefore, the temperature threshold is set at 77°C, and the pressure drop value, short-circuit current characteristic value, and resistance characteristic value are coupled as the threshold for level III warning. In terms of temperature monitoring at this stage, a K-type thermocouple with a diameter of 1 mm is selected to monitor the surface temperature of the battery. At the same time, an M6 ring-shaped K-type thermocouple is used to monitor the positive and negative electrode temperatures, which can accurately locate abnormal batteries. The accuracy of the above temperature sensors is 0.4% to achieve full-range and high-precision monitoring. The sensors are connected to the temperature monitoring terminal, and 77°C is set as the level III alarm value. In terms of voltage monitoring at this stage, to reduce the influence of the connection component resistance on the parallel module, the voltage of each battery cell in the module is monitored on this platform to accurately locate the position of the abnormal battery cell. Since the voltage of the module is monitored in the operating state on this platform, and it has been experimentally verified that the voltage will show a slow downward trend with a downward amplitude of 23.9%. To distinguish the voltage abnormality at this stage, the instantaneous voltage drop amplitude = 25% is used as the warning index. The voltage sensor is connected to the terminal monitoring, and the pressure drop value = 25% is set as the level III alarm value. In terms of short-circuit current monitoring at this stage, due to the existence of a certain resistance in the connection components, the short-circuit current at this stage < total discharge current / 2. Therefore, the short-circuit current = total discharge current / 2 is set as the level III alarm value. In terms of resistance monitoring at this stage, due to the evaporation of the electrolyte and the increase in the positive electrode impedance, the overall resistance of the module shows an upward trend. It has been experimentally verified that the maximum resistance increase = 0.2%. The resistance sensor is connected to the terminal monitoring, and the resistance increase ≥ 0.2% is set as the level III alarm value.

[0036] Single thermal runaway stage: The diaphragm collapse leads to large-area short circuit, oxygen release from the positive electrode, and reaction of active lithium on the negative electrode surface being in the same dimension, which serves as the internal inducement for triggering thermal runaway. Combining the characteristic temperatures of the above three reactions, this platform sets 130°C as the thermal runaway trigger temperature, i.e., the threshold temperature for level II warning. At the temperature monitoring level in this stage, a 1-mm K-type thermocouple and an M6 ring thermocouple are used as temperature monitoring devices to monitor the large-area center temperature and the positive and negative electrode temperatures respectively, so as to obtain the trigger temperature and the thermal runaway peak temperature when the single cell undergoes thermal runaway in this stage, and then determine the severity of the single cell thermal runaway. The temperature sensor is connected to the monitoring terminal, and 130°C is set as the level II alarm value. At the voltage monitoring level in this stage, when the instantaneous voltage drop amplitude > 25%, it means that large-area short circuit occurs inside, so the voltage drop amplitude > 25% is set as the level II alarm value. When the operating load device senses through the built-in voltage sensor that the current voltage ≤ the set discharge cut-off voltage of the module, the operating load will cut off all operating conditions, making the module in an open circuit state to reduce the damage to other modules and load devices. At the resistance monitoring level in this stage, due to the dissolution of transition metals and the decomposition of lithium salts, the overall resistance of the module shows a downward trend and the maximum decrease = 8%, so the resistance decrease amplitude ≥ 8% is set as the level II alarm value. At the short-circuit current monitoring level in this stage, to accurately monitor the short circuit of abnormal battery cells inside the module, this platform introduces a fluxgate current sensor with an accuracy as high as 50 ppm, which can achieve dynamic response within 4 μs, and then can realize the early monitoring of internal short circuit of abnormal batteries. The fluxgate current sensor is matched with an NI high-precision acquisition card, and the maximum value, minimum value, and average value of the current collected per second can be displayed on the short-circuit current monitoring terminal to obtain the activity range of the short-circuit current. Due to large-area short circuit inside the battery cell, at this time the short-circuit current > total discharge current / 2, and the current monitoring terminal will give an alarm. In addition, the current monitoring terminal in this stage is built with an ampere-hour integration module, which can estimate the current SOC of adjacent battery cells according to the short-circuit current magnitude and the short-circuit duration, and then can predict in advance the severity when adjacent battery cells undergo thermal runaway caused by thermal diffusion. At the gas monitoring level in this stage, the platform is equipped with gas sensors to monitor the concentrations of O2, CO, CO2, and CH4 during thermal runaway, and the monitoring data will be presented on the gas monitoring terminal.

[0037] Module thermal diffusion stage: When thermal runaway of one cell triggers thermal runaway of adjacent cells, it is a thermal diffusion phenomenon. In terms of temperature monitoring at this stage, except for the thermally runaway cell, the K-type thermocouple monitors the temperature of adjacent cells up to 130°C, which is the thermal diffusion stage, i.e., the level-I warning. Since there is a short-circuit current inside the parallel module, which in turn reduces the SOC of adjacent cells, the peak temperature of each cell in the module is mainly monitored during the thermal diffusion stage, and the peak temperature should show an overall downward trend. In terms of voltage monitoring at this stage, since thermal diffusion causes all cells in the module to experience thermal runaway, the voltage drop amplitude of each cell = 100%, so the voltage drop amplitude = 100% is set as the level-I alarm value. In terms of current monitoring at this stage, all cells inside the module have experienced thermal runaway, the electrical performance has been damaged, the transfer of the short-circuit current inside the module is terminated, and the fluxgate current sensor monitors a current value of 0, reaching the level-I alarm state.

[0038] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A disaster monitoring platform for a lithium-ion battery module in an operating state, characterized in that, It includes a sealed test chamber (1), a flue gas analyzer (2), an infrared thermal imager (3) and a camera (4). Two lifting frames (5) are installed in the sealed test chamber (1). A lithium battery module (6) and a current sensor (7) are respectively arranged on the two lifting frames (5). The lithium battery module (6) is connected to the current sensor (7). A voltage monitoring device (8), a resistance monitoring device (9) and a temperature monitoring device (17) are arranged outside the sealed test chamber (1). The voltage monitoring device (8) and the resistance monitoring device (9) are connected to the lithium battery module (6) to monitor the cell voltage and the overall resistance of the lithium battery module (6).

2. The disaster monitoring platform for a lithium-ion battery module in an operating state according to claim 1, wherein The volume of the sealed test chamber (1) is 1 m 3 , and its thickness is 5 cm. A double flange is installed on the hatch of the sealed test chamber (1). Heating coils are installed on the inner wall of the sealed test chamber (1). A pressure relief valve and a flue gas probe (10) are installed on the top of the sealed test chamber (1). The flue gas probe (10) is connected to a flue gas analyzer (2). A plurality of wire passing holes (11) are provided on the side wall of the sealed test chamber (1). A transparent observation window (12) is embedded on one side surface of the sealed test chamber (1). An optical glass window (13) is embedded on the transparent observation window (12). The camera (4) is arranged outside the sealed test chamber (1) and is directly opposite to the transparent observation window (12). The infrared thermal imager (3) is arranged outside the sealed test chamber (1) and is directly opposite to the optical glass window (13).

3. The disaster monitoring platform for a lithium-ion battery module in an operating state according to claim 1, characterized in that A display platform (14), a discharge platform (15) and a DC power supply (16) are also arranged outside the sealed test chamber (1). The temperature monitoring device (17) includes a temperature sensor and a temperature display device. The temperature sensor is arranged in the lithium battery module (6) to monitor the temperature of the cells. The discharge platform (15) is connected to the lithium battery module (6) through a 60A test line. The DC power supply (16) is connected to the current sensor (7) to supply power to the current sensor (7).

4. A disaster monitoring platform for a lithium-ion battery module in an operating state according to claim 3, wherein The lithium battery module (6) is composed of multiple cells connected in parallel. The current sensor (7) is a fluxgate current sensor. The lithium battery module (6) is fixed on the lifting frame (5) by a 10mm thick steel plate. An asbestos heat insulation layer is arranged between the lithium battery module (6) and the steel plate. A 300W PI film heating sheet is attached to the surface of the lithium battery module (6). The temperature sensor includes two types, namely a K-type thermocouple and a ring thermocouple. Two K-type thermocouples with a diameter of 1mm are symmetrically attached to the center of the large surface of each cell, and ring thermocouples are arranged at the positive and negative electrodes of the cell.

5. The disaster monitoring platform for a lithium-ion battery module in an operating state according to claim 3, wherein, The current sensor (7) is connected to a current data acquisition card (18). The display platform is connected to the current data acquisition card (18), the voltage monitoring device (8), the resistance monitoring device (9) and the temperature monitoring device (17) to display the monitoring data in real time.

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