Battery monitoring system for measuring hydrogen concentration to detect battery cell overtemperature and predict thermal runaway

Abstract

Battery monitoring system, comprising: a hydrogen sensor system configured to selectively measure a plurality of hydrogen concentrations in a plurality of battery cells; and a controller configured to detect battery cell overtemperature in at least one of the plurality of battery cells in response to a corresponding one of the plurality of measured hydrogen concentrations of the plurality of battery cells; characterized in that (i) the control system is designed in such a way that it: causing the hydrogen sensor system to measure a first hydrogen concentration in one of the plurality of battery cells; when hydrogen is detected, calculate the rate of increase of the hydrogen concentration; if the rate of increase of the hydrogen concentration is greater than a predetermined rate, a thermal runaway event is diagnosed for a corresponding cell of the plurality of battery cells; and if the rate of increase of the hydrogen concentration is less than a predetermined rate, an overtemperature event is diagnosed for a corresponding one of the plurality of battery cells; or that (ii) the control system is designed in such a way that it: comparing the measured hydrogen concentration with a predetermined hydrogen concentration if the rate of increase of the hydrogen concentration is less than a predetermined rate; and if the measured hydrogen concentration is greater than the predetermined hydrogen concentration, diagnoses an overtemperature in a corresponding one of the plurality of battery cells; or that (iii) the controller is configured to change at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the excess temperature; or (iv) the control system is designed in such a way that it: causing the hydrogen sensor system to measure a first hydrogen concentration in one of the plurality of battery cells; when hydrogen is detected in one of the plurality of battery cells, comparing the measured hydrogen concentration with a predetermined hydrogen concentration; if the measured hydrogen concentration is not greater than the predetermined hydrogen concentration, a monitoring frequency is increased; and if the measured hydrogen concentration is greater than the predetermined hydrogen concentration, diagnoses an overtemperature in a corresponding one of the plurality of battery cells; or that (v) the hydrogen sensor system comprises hydrogen sensors arranged in each of the plurality of battery cells; or that (vi) the hydrogen sensor system comprises a hydrogen sensor multiplexed to detect the plurality of battery cells.

Description

INTRODUCTION

[0001] The present disclosure relates to battery cells and, in particular, to a battery monitoring system according to the preamble of claim 1 for monitoring the temperature of battery cells, as is essentially known from US 2021 / 0 245 627 A1.

[0002] Systems of a similar nature are described in the documents CN 1 14 613 932 A and US 2011 / 0 059 341 A1.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric machines and a battery system with one or more battery modules, each comprising multiple battery cells. A power control system is used to control the charging and / or discharging process of the battery system during charging and / or driving. A battery monitoring system monitors various parameters of the battery system and controls the operation of the battery system based on these parameters. SUMMARY

[0004] According to the invention, a battery monitoring system is presented which is characterized by the features of claim 1.

[0005] In other features, the controller is configured to change at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the overtemperature.

[0006] In other features, the hydrogen sensor system includes a plurality of valves, a first plurality of gas lines fluidly connecting the plurality of battery cells to the inlets of the plurality of valves, and a second plurality of gas lines fluidly connecting the outlets of the plurality of valves.

[0007] In another feature, the hydrogen sensor system further comprises a hydrogen sensor selectively connected to one of the plurality of battery cells through the plurality of valves, the first plurality of gas lines, and the second plurality of gas lines.

[0008] Ferber describes a method for monitoring an overtemperature in a battery module comprising a plurality of battery cells. The method includes selectively measuring a plurality of hydrogen concentrations in each of a plurality of battery cells; and detecting a battery cell overtemperature in at least one of the plurality of battery cells in response to a corresponding one of the plurality of measured hydrogen concentrations of the plurality of battery cells.

[0009] In other features, the method comprises measuring a first hydrogen concentration of one of the plurality of battery cells; if hydrogen is detected, calculating a rate of increase in the hydrogen concentration; if the rate of increase in the hydrogen concentration is greater than a predetermined rate, diagnosing a thermal runaway event for a corresponding one of the plurality of battery cells; and if the rate of increase in the hydrogen concentration is less than a predetermined rate, diagnosing an overtemperature event for a corresponding one of the plurality of battery cells.

[0010] In other features, when the rate of increase of the hydrogen concentration is less than a predetermined rate, the measured hydrogen concentration is compared with a predetermined hydrogen concentration. If the measured hydrogen concentration is greater than the predetermined hydrogen concentration, the overtemperature is diagnosed in a corresponding one of the plurality of battery cells.

[0011] In other features, the method includes changing at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the overtemperature. The method includes causing the hydrogen sensor system to measure a first hydrogen concentration of one of the plurality of battery cells; if hydrogen is detected in the one of the plurality of battery cells, comparing the measured hydrogen concentration to a predetermined hydrogen concentration; and if the measured hydrogen concentration is not greater than the predetermined hydrogen concentration, increasing a monitoring frequency; and if the measured hydrogen concentration is greater than the predetermined hydrogen concentration, diagnosing an overtemperature in a corresponding one of the plurality of battery cells.

[0012] In other features, the method includes changing at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the excess temperature. The method includes disposing hydrogen sensors in each of the plurality of battery cells. The method includes multiplexing a hydrogen sensor to sense the plurality of battery cells.

[0013] Further areas of applicability of the present invention will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are provided for illustrative purposes only. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be more fully understood from the detailed description and the accompanying drawings, in which: Fig. Figure 1 is a side cross-sectional view of an example of a battery cell; Fig. 2 is a functional block diagram of an example of a battery module having a plurality of battery cells and a temperature sensor; Fig. 3A to 3C illustrate examples of battery monitoring systems with hydrogen sensor systems according to the present invention; Fig. Figure 4 is a graph showing the measured hydrogen concentrations as a function of the temperature of the battery cell; Fig. 5 is a flowchart of an example of a method for monitoring a battery system to detect an overtemperature of the battery cells based on measured hydrogen concentrations and a rate of increase of the hydrogen concentrations in each battery cell according to the present invention; and Fig. 6 is a flowchart of an example method for monitoring a battery system to detect overtemperature of the battery cells based on the measured hydrogen concentrations in each battery cell according to the present invention.

[0015] Reference symbols may be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0016] Although the battery monitoring system is described here in the context of electric vehicles, the battery monitoring system may also be used to monitor battery systems in stationary applications and / or in other applications.

[0017] The battery monitoring system of the present invention detects overtemperature in the battery cells of a battery system by monitoring the hydrogen concentration in each battery cell. In some examples, the battery cells comprise lithium-ion battery cells. Hydrogen concentrations and rates of increase may be used to predict and detect thermal runaway or other overtemperature events in the battery cells that would otherwise go undetected in other battery monitoring systems.

[0018] As described above, a battery system can comprise one or more battery modules, each containing multiple battery cells. Often, a single temperature sensor is used to monitor the temperature of the battery module, but not that of the individual battery cells. Therefore, one of the battery cells may experience an overtemperature without being detected by the battery module's temperature sensor. The battery cell may thermally run away and / or cause neighboring battery cells to heat up before the temperature sensor detects a change. By the time the overtemperature is detected in these systems, it may already be too late to prevent thermal runaway or other damage.

[0019] The battery monitoring system of the present invention monitors molecular hydrogen gas (H2) generated in a lithium-ion battery cell when the temperature exceeds a temperature threshold (e.g., ~70°C). Battery cell operating temperatures typically range from 0°C to 55°C (and preferably 0°C to 35°C) during operation.

[0020] Higher-than-normal battery cell temperatures may occur due to thermal runaway or during otherwise normal operation due to temperature gradients within the battery cells (i.e., heating near tabs, locally high resistance, and / or thermal control strategies). The battery monitoring system according to the present invention monitors the molecular hydrogen gas concentration and rate of rise within the battery cell casings to determine when the battery cells are operating above the temperature threshold. The battery monitoring system is therefore capable of predicting and detecting thermal runaway or other malfunctions of the cells or the thermal control system so that corrective measures can be taken to attempt to prevent these types of events.

[0021] The battery monitoring system continuously and / or intermittently samples gas from each battery cell. If the H2 concentration is above a predetermined threshold, it is likely that the battery cell has been exposed to temperatures above a temperature threshold (e.g., ~70°C). With continuous monitoring, the rate of rise and the H2 concentration can be used to predict thermal runaway or other excessive cell temperature. With intermittent monitoring, the concentration can be used to detect excessive cell temperature.

[0022] With reference now to Fig. 1, a battery cell 100 includes cathode electrodes 110-1, 110-2, ..., and 110-C (collectively or individually, cathode electrodes 110) and anode electrodes 120-1, 120-2, ..., and 120-A (collectively or individually, anode electrodes 120). In some examples, the cathode electrodes 110 and the anode electrodes 120 are arranged in an alternating arrangement with separators 118-1, ..., and 118-S (collectively or individually, separators 118) disposed therebetween.

[0023] The cathode electrodes 110-1, 110-2, ..., and 110-C include cathode active material 112-11, 112-12, ..., 112-C1, and 112-C2, each disposed on opposite sides of the cathode current collectors 114-1, ..., and 114-C. In some examples, the cathode current collectors are made of aluminum. The anode electrodes 120-1, 120-2, ..., and 120-C include anode active material 122-11, 122-12, ..., 122-C1, and 122-C2, each disposed on opposite sides of the anode current collectors 124-1, ..., and 124-C. In some examples, the anode current collectors 124 are made of copper. Fig. 1, A, C, and S are integers greater than one. In some examples, the battery cells comprise lithium-ion battery cells, and the active cathode material comprises metal oxide cathode active material.

[0024] With reference now to Fig. 2, a battery module 200 comprises a plurality of battery cells 100-1, 100-2, ..., and 100-C (where C is an integer greater than one) arranged in a housing of the battery module 200. A temperature sensor 206 measures the temperature of all battery cells 100-1, 100-2, ..., and 100-C in the battery module 200. The battery cells are connected in series and / or parallel.

[0025] A controller 210 is configured to monitor the temperature of the battery module 200, but not that of the individual battery cells. Therefore, one of the battery cells 100-1, 100-2, ..., and 100-C may have an overtemperature without being detected by the temperature sensor 206 for the battery module 200.

[0026] A battery monitoring system according to the present invention takes gas samples from inside each battery cell. If the H2 concentration is above a predetermined threshold, it is likely that the battery cell has been exposed to temperatures above a temperature threshold (e.g., ~70°C). With continuous monitoring, the rate of increase and the H2 concentration can be used to predict thermal runaway or other excessive cell temperature. With intermittent monitoring, the concentration can be used to detect excessive cell temperature.

[0027] There are several ways to sample the H2 concentration in the battery cells. With reference to Fig. 3A, a plurality of battery cells 340-1, 340-2, ..., and 340-C are selectively connected to a hydrogen sensor 310 and a pressure sensor 314 through gas lines 342 and valves 330-1, 330-2, ..., and 330-C. In other words, the hydrogen sensor 310 is multiplexed (connected sequentially to the selected battery cells through the corresponding valve and gas lines).

[0028] A vacuum pump 318 creates a vacuum in the gas lines 342 to sample the gases in the battery cell casings. Upon detection of H2, one of the valves 330 corresponding to the battery cell 340 under investigation is opened, the gas in the battery cell 340 is sampled, and the H2 concentrations are detected. A controller 341 controls the valves 330, the vacuum pump 318, the hydrogen sensor 310, and the pressure sensor 314 to sample the H2 concentrations in each of the battery cells 340. The controller 341 may also control the charging and / or discharging of the battery cells or communicate with another controller that controls the charging and / or discharging of the battery cells.

[0029] With reference now to Fig. 3B, a plurality of battery cells 350-1, 350-2, ..., and 350-C include an electrode stack 354-1, 354-2, ..., and 354-C, and hydrogen sensors 358-1, 358-2, ..., and 358-C in battery cell housings 359. A controller 370 receives H2 concentrations from the battery cells 350-1, 350-2, ..., and 350-C in a wired or wireless manner. When wireless communication is used, the plurality of battery cells 350-1, 350-2, ..., and 350-C include wireless transmitters 374, and the controller 370 communicates with a receiver 378.

[0030] With reference now to Fig. 3C, a battery cell 380 includes an electrode stack 384 disposed within a housing 382. In some examples, the housing 382 includes a pouch cell, a prismatic cell, or another type of battery cell format. A hydrogen sensor 388 is attached to the housing 382 and samples gas from the battery cell 380 through an opening 390 in the housing 382.

[0031] With reference now to Fig. 4, the H2 concentration in the battery cell casing can be used to detect temperature increases in the battery cell. Fig. 4 the measured H2 concentrations increase as a function of temperature.

[0032] With reference now to Fig. 5, a method 400 measures the H2 to detect overtemperature faults in the battery cells. At 410, the H2 concentration in each battery cell is monitored. At 418, the method determines whether H2 is detected. If H2 is not detected, the method returns to 410. If H2 is detected, the method continues at 420. At 420, the method determines whether the rate of increase of H2 is greater than a predetermined threshold. If 420 is false, the method determines whether the H2 concentration is greater than a predetermined threshold at 424. If 424 is false, the method continues at 410. If 420 is true, the method reports the temperature increase and the potential for thermal runaway at 430.

[0033] If 424 is true, the method reports the cell overtemperature at 434 and optionally takes remedial action at 438. For example, the controller is configured to change a charging or discharging parameter of the battery cells in response to detecting the overtemperature. For example, a lower charging voltage, a lower charging current, a lower charging rate, a lower target SOC, etc. may be used. For example, a lower discharging voltage, a lower discharging current, a lower discharging rate, etc. may be used.

[0034] With reference now to Fig. 6, a method 450 measures molecular hydrogen to detect overtemperature faults. At 454, the H2 concentration in each cell is measured. At 458, the method determines whether H2 is detected. If 458 is false, the method returns to 454.

[0035] If 458 is true, the method determines whether the H2 concentration is greater than a predetermined H2 limit at 462. If 462 is false, the method continues at 464 and the H2 monitoring frequency is increased (or the predetermined sampling period between monitoring loops is decreased).

[0036] If 462 is true, the procedure reports the temperature rise and optionally takes remedial action at 470.

Claims

[1] Battery monitoring system, comprising: a hydrogen sensor system configured to selectively measure a plurality of hydrogen concentrations in a plurality of battery cells; and a controller configured to detect battery cell overtemperature in at least one of the plurality of battery cells in response to a corresponding one of the plurality of measured hydrogen concentrations of the plurality of battery cells; characterized by , that (i) the control system is designed in such a way that it: causing the hydrogen sensor system to measure a first hydrogen concentration in one of the plurality of battery cells; when hydrogen is detected, calculate the rate of increase of the hydrogen concentration; if the rate of increase of the hydrogen concentration is greater than a predetermined rate, a thermal runaway event is diagnosed for a corresponding cell of the plurality of battery cells; and if the rate of increase of the hydrogen concentration is less than a predetermined rate, an overtemperature event is diagnosed for a corresponding one of the plurality of battery cells; or that (ii) the control system is designed in such a way that it: comparing the measured hydrogen concentration with a predetermined hydrogen concentration if the rate of increase of the hydrogen concentration is less than a predetermined rate; and if the measured hydrogen concentration is greater than the predetermined hydrogen concentration, diagnoses an overtemperature in a corresponding one of the plurality of battery cells; or that (iii) the controller is configured to change at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the excess temperature; or (iv) the control system is designed in such a way that it: causing the hydrogen sensor system to measure a first hydrogen concentration in one of the plurality of battery cells; when hydrogen is detected in one of the plurality of battery cells, comparing the measured hydrogen concentration with a predetermined hydrogen concentration; if the measured hydrogen concentration is not greater than the predetermined hydrogen concentration, a monitoring frequency is increased; and if the measured hydrogen concentration is greater than the predetermined hydrogen concentration, diagnoses an overtemperature in a corresponding one of the plurality of battery cells; or that (v) the hydrogen sensor system comprises hydrogen sensors arranged in each of the plurality of battery cells; or that (vi) the hydrogen sensor system comprises a hydrogen sensor multiplexed to detect the plurality of battery cells. [2] The battery monitoring system of claim 1, wherein the controller is configured to change at least one of the charging or discharging parameters of the plurality of battery cells in response to detecting the overtemperature. [3] The battery monitoring system of claim 1, wherein the hydrogen sensor system comprises: a variety of valves; a first plurality of gas lines connecting the plurality of battery cells to the inlets of the plurality of valves; and a second plurality of gas lines fluidly connected to the outlets of the plurality of valves. [4] The battery monitoring system of claim 3, wherein the hydrogen sensor system further comprises a hydrogen sensor selectively connected to one of the plurality of battery cells via the plurality of valves, the first plurality of gas lines, and the second plurality of gas lines.

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