Battery provided with a discharge during thermal runaway and corresponding control method.

Abstract

Battery (1) comprising electrochemical cells (2), comprising a temperature sensor configured to measure the temperature in the battery (1), a memory comprising a temperature threshold, a means for comparing the temperature measurement with the temperature threshold, an energy consumer (3) and a controlled switch (4) connecting the cells to the energy consumer (3), the switch (4) being controlled to be on when the measurement of the temperature sensor is greater than the stored temperature threshold, so that the energy included in the electrochemical cells (2) is consumed by the energy consumer (3). Figure for abstract: Fig 1

Description

Title of the invention: Battery provided with a discharge during thermal runaway and corresponding control method. Technical field

[0001] The technical field of the invention is battery management, and more particularly, such management during thermal runaway. Previous techniques

[0002] A battery generally comprises several electrochemical cells, each cell being subject to thermal runaway. This runaway phenomenon is particularly prevalent for Li-ion type cells and can be triggered by three types of initiations:

[0003] - thermal via an increase in temperature,

[0004] - electrical via a short circuit or overvoltage, or

[0005] - mechanical via deformation or perforation.

[0006] In addition to these initiations, a runaway can also result from an internal defect in the cell.

[0007] Thermal runaway, particularly for Li-ion technology, can cause flames, outgassing, explosions and projections of material within the battery.

[0008] Currently, technical solutions for limiting the spread of runaway are being implemented. These solutions are based on the use of physical barriers such as materials resistant to high temperatures or fire resistant. Patent application FR 3095895 in the name of the applicant illustrates such a solution.

[0009] There is a need for a battery provided with a device for limiting thermal runaway per se. Statement of the invention

[0010] The subject of the invention is a battery comprising electrochemical cells, as well as a temperature sensor configured to measure the temperature in the battery, a memory comprising a thermal runaway temperature threshold, a means for comparing the temperature measurement with the thermal runaway temperature threshold, an energy consumer and a controlled switch connecting the electrochemical cells to the energy consumer, the switch being controlled to turn on when the measurement of the temperature sensor is greater than the stored temperature threshold, so that the energy included in the electrochemical cells is consumed by the energy consumer.

[0011] An energy consumer can be chosen from a resistor, a heating system, a load balancing system, the consumed energy being dissipated in the form of heat by the Joule effect.

[0012] Alternatively, an energy consumer may be an ultracapacitor, with consumed energy being stored in the ultracapacitor.

[0013] An energy consumer can be arranged as close as possible to the electrochemical cells.

[0014] An energy consumer may be arranged in a part of the battery separate from the part comprising the electrochemical cells.

[0015] The battery may comprise an outer covering, an energy consumer being arranged on the outside of the covering, the electrochemical cells being arranged inside the covering.

[0016] The battery may comprise an outer covering, an energy consumer being arranged at a distance from the covering, the electrochemical cells being arranged inside the covering.

[0017] The temperature sensor may be configured to measure the temperature in the battery in the vicinity of a first group of cells, the battery comprising a second temperature sensor configured to measure the temperature in the battery in the vicinity of a second group of cells, a second means for comparing the temperature measurement of the second sensor to the temperature threshold, a second energy consumer and a second controlled switch connecting the cells to the second energy consumer, the second switch being controlled to turn on when the measurement of the second temperature sensor is greater than the stored temperature threshold, so that the energy included in the second group of electrochemical cells is consumed by the second energy consumer,the control of the second switch being independent of the control of the first switch so as to be able to discharge groups of cells depending on the location of the thermal runaway in the battery.

[0018] Another object of the invention is an aircraft equipped with a battery as described above.

[0019] The invention also relates to a method for controlling a battery as described above, in which the temperature in the battery is determined, the temperature is compared to a thermal runaway temperature threshold, and the consumption of the energy stored in the electrochemical cells of the battery is controlled when the temperature measurement is greater than the thermal runaway temperature threshold so as to reduce the reactivity of the cells. Brief description of the drawings

[0020] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0021] - figure [Fig. 1] illustrates a first embodiment of a battery according to invention,

[0022] - figure [Fig.2] illustrates a second embodiment of a battery according to invention, and

[0023] - figures [Fig.3] to [Fig.5] illustrate the arrangement of energy consumers in a battery according to the invention. Detailed description

[0024] Solutions for limiting the propagation of thermal runaway involving physical barriers (such as flame-resistant materials) do not make it possible to reduce the reactivity of the runaway but only its propagation. However, it is necessary, in addition to reducing the speed of propagation of thermal runaway, to make it possible to reduce its reactivity.

[0025] A reduction in cell reactivity makes it possible to reduce not only the extent and intensity of thermal runaway but also to reduce the constraints imposed on the solutions for physical containment of thermal runaway since the violence of the reaction is reduced. Thus, gains in mass and volume are expected at the level of the protective barriers to be put in place.

[0026] The state of charge is a factor in the reactivity of cells during thermal runaway. Indeed, experiments show that the mass of material lost is lower when the cells are discharged compared to the mass lost when the cells are charged.

[0027] The battery according to the invention uses means of consuming the energy stored in the cells to discharge them and reduce their reactivity with respect to thermal runaway. Such a reduction in reactivity has the advantage of limiting the propagation of thermal runaway in the battery. The cells of the battery, adjacent to the cells subject to thermal runaway, thus have a low or even zero state of charge and are less prone to thermal runaway. The propagation of thermal runaway is thus reduced.

[0028] This results in a control method in which it is detected that thermal runaway is taking place in the battery through a temperature measurement. A controlled switch is then controlled in order to close the electrical circuit between the connected cells and the energy consumers. To achieve this, the battery advantageously comprises an electronic control means comprising a memory and a means for comparing a value stored in the memory with a measurement of a temperature sensor. The memory includes a temperature threshold value from which the consumption of cell energy must be triggered.

[0029] All or part of the cells located around at least one cell subject to thermal runaway are thus discharged. This is particularly the case if several discharge means are provided and connected to different sets of cells within the same battery.

[0030] [Fig.l] illustrates a first embodiment, in which cells 2 of a battery 1 are connected in parallel to each other and to an energy consumer 3. A controlled switch 4 makes it possible to activate the energy consumption of the cells 2 by the energy consumer 3.

[0031] It will be understood that by circulating a current between one or more cells to be discharged and a resistance, the state of charge of the connected cells is reduced by the Joules effect. The same is true with a heating system.

[0032] Examples of energy consumers 3 include dedicated resistors, a heating system, a load balancing system, or ultracapacitors.

[0033] A load balancing system makes it possible to move the load from at least one cell to be discharged to at least one other cell.

[0034] During thermal runaway, such a charge balancing system can also be diverted from its primary function in order to transform the consumed energy into heat by the Joule effect as in the case of a resistor or a heating system. The electronic balancing card then consumes the energy of the cells using the electronic components that it comprises normally allowing the balancing of the cells. Such a switching is normally triggered by the comparison of the measurement of a voltage value or state of charge SOC (acronym for "State of Charge") of one of the cells of the battery with a stored threshold value. When the measured value is lower than the threshold value, an energy transfer between cells is carried out.The switching of energy from the cells to the electronic components of the charge balancing system is also triggered by comparing the temperature measurement of at least one of the cells connected to the charge balancing system with a stored threshold value. When the measured value is above a threshold, the energy from the cells is discharged into the charge balancing system's own electronic components in order to dissipate it by the Joule effect.

[0035] Finally, an ultracapacitor makes it possible to store a large quantity of energy very quickly so that several cells can see their state of charge significantly significantly reduced in a short time.

[0036] [Fig.2] illustrates an alternative embodiment in which several groups 2a, 2b of cells are simultaneously connected to an energy consumer 3. The groups of cells 2a, 2b are then connected in series with each other and with the energy consumer 3, while the cells 2 are connected in parallel within each group. This makes it possible to create a larger area around cells, subject to thermal runaway.

[0037] The energy consumers may be arranged in the battery, in the same environment as the cells, as in the embodiments illustrated by Figures 1 and 2. In other embodiments, the energy consumer 3 is not arranged as close as possible to the cells. The energy consumers may also be arranged in the battery but in a different environment than that in which the cells are located. [Fig. 3] illustrates such an embodiment, the energy consumer 3 being arranged in a zone 1a distinct from the battery, isolated for example by an internal partition (not illustrated).

[0038] The energy consumers can be arranged outside the battery, but as close as possible to it. [Fig.4] illustrates such an embodiment, the energy consumer 3 being arranged immediately outside the battery 1, in particular on the cladding.

[0039] Finally, the energy consumers can be arranged outside the battery, at a distance. [Fig. 5] illustrates such an embodiment, the energy consumer 3 being arranged at a distance from the battery 1.

[0040] The energy consumers arranged internally to the battery have the advantage of moderating the increase in mass of the battery due to their addition, in particular by limiting the required connectors. Depending on the energy consumers chosen, the increase in mass is more moderate due to their presence outside the implementation of the invention.

[0041] Such embodiments have the advantage of releasing part of the energy of the cells before their thermal runaway by using the components already present in the battery. The mass of the battery is therefore not impacted.

[0042] Such embodiments, however, have the disadvantage of releasing the heat produced by the energy consumer inside the battery, which could have the effect of propagating the runaway by an indirect route, on cells which are nevertheless discharged and therefore much less reactive.

[0043] The energy consumers can also be arranged externally. Such an embodiment has the advantage of releasing the energy of the cells in the form of heat outside the housing at the expense of the mass (due to the addition of the energy consumers and the corresponding connection elements). The heat released cannot then contribute to the propagation or initiation of thermal runaway.

Claims

Claims

1. Battery (1) comprising electrochemical cells (2), characterized in that it comprises a temperature sensor configured to measure the temperature in the battery (1), a memory comprising a thermal runaway temperature threshold, a means for comparing the temperature measurement with the thermal runaway temperature threshold, an energy consumer (3) and a controlled switch (4) connecting the electrochemical cells (2) to the energy consumer (3), the switch (4) being controlled to be on when the measurement of the temperature sensor is greater than the stored temperature threshold, so that the energy included in the electrochemical cells (2) is consumed by the energy consumer (3), the energy consumer (3) being an ultracapacitor, the consumed energy being stored in the ultracapacitor.

2. Battery (1) according to claim 1, in which an energy consumer (3) is chosen from a resistor, a heating system, a charge balancing system, the consumed energy being dissipated in the form of heat by the Joule effect.

3. Battery (1) according to one of claims 1 or 2, in which an energy consumer (3) is arranged as close as possible to the electrochemical cells (2).

4. Battery (1) according to one of claims 1 or 2, in which an energy consumer (3) is arranged in a part of the battery (1) separate from the part comprising the electrochemical cells (2).

5. Battery (1) according to one of claims 1 or 2, wherein the battery (1) comprises an outer covering, an energy consumer (3) being arranged on the outside of the covering, the electrochemical cells (2) being arranged inside the covering.

6. Battery (1) according to one of claims 1 or 2, in which the battery (1) comprises an outer covering, an energy consumer (3) being arranged at a distance from the covering, the electrochemical cells (2) being arranged inside the covering.

7. Battery (1) according to one of claims 1 or 2, wherein the temperature sensor is configured to measure the temperature in the battery (1) in the vicinity of a first group of cells, the battery (1) comprising a second temperature sensor configured to measure the temperature in the battery (1) in the vicinity of a second group of cells, a second means for comparing the temperature measurement of the second sensor to the temperature threshold, a second energy consumer (3) and a second controlled switch (4) connecting the cells to the second energy consumer (3), the second switch (4) being controlled to be on when the measurement of the second temperature sensor is greater than the stored temperature threshold, so that the energy included in the second group of electrochemical cells (2) is consumed by the second energy consumer (3), the control of the second switch (4) being independent of the control of the first switch (4) so ​​as to be able to discharge groups of cells depending on the location of the thermal runaway in the battery (1).

8. Aircraft provided with a battery (1) according to any one of claims 1 to 7.

9. A method of controlling a battery (1) according to any one of claims 1 to 7, wherein the temperature in the battery (1) is determined, the temperature is compared to a thermal runaway temperature threshold, and the consumption of the energy stored in the electrochemical cells (2) of the battery (1) is controlled when the temperature measurement is greater than the thermal runaway temperature threshold so as to reduce the reactivity of the cells.

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