Device for forming a plurality of batteries and related method of controlling a forming process

Abstract

The device of this disclosure allows the formation process to be performed on multiple batteries (5) simultaneously due to an auxiliary board (8) comprising a plurality of output connectors (9), wherein each output connector (9) is configured to be directly connected to a respective charging connector (7) of each battery (5), as well as a plurality of bidirectional switches (10a, 10b) that may be individually opened / closed to define electrical conduction paths between the output terminal (6) of each power supply (2) of the formation board and a charging connector (7) of each battery (5) to be subjected to the formation process. In addition, the same control unit (4) of the formation board is also configured to individually close / open each of the bidirectional switches (10a, 10b) of the auxiliary board (8) in order to close / open a respective electrical conduction path.

Description

[0001] “Device for forming a plurality of batteries and related control method of a forming process”

[0002] TECHNICAL FIELD

[0003] This disclosure relates to devices for carrying out the so-called battery forming process, arranged in such a way that it can be reconfigured while the process is being carried out, as well as a related control method of process for forming a plurality of batteries.

[0004] BACKGROUND

[0005] Rechargeable secondary batteries, such as lithium-ion batteries, are currently used for a wide variety of applications. Once manufactured, these batteries undergo a so-called “formation” process, in which the newly manufactured batteries undergo cycles in which they are subjected to appropriately modulated voltages or currents. During the formation process of a newly manufactured battery, due to the administration of modulated voltages or currents, electrochemical phenomena occur within the battery itself, whereby the anode is covered by the so-called “Solid Electrolyte Interphase” (or SEI for short) and the cathode is covered by the so-called “Cathode Electrolyte Interface” (or CEI for short). If the formation process of a battery is performed properly, these electrode surface interface layers (SEI, CEI) are deposited on the battery electrodes with the battery electrolyte, optimising the properties of the battery in terms of charging capacity and uniformity of charge / discharge cycles.

[0006] SUMMARY

[0007] The formation process is therefore a critical aspect in battery production because it has a major influence on the properties of the batteries. The electrode interface surface layers SEI, CEI are to be formed in a controlled manner by administering for a relatively long time modulated voltages or currents using a special device to form rechargeable batteries, whereby the device has at least one formation board of the type illustrated in Figure 1 comprising: an input terminal A on which a supply voltage is made available; a plurality of controlled bidirectional power supplies 2, which may for example be buck converters, or boost converters, or converters that may operate as buck or boost depending on the direction of the current, or converters of another type, suitable for generating a modulated voltage or current to perform a formation process, wherein each bidirectional power supply 2:

[0008] - can be supplied via the input terminal A,

[0009] - has at least one respective output terminal 6, which can be connected to a charging connector 7 of each battery 5,

[0010] - is configured to generate, on the respective output terminal 6, a respective modulated voltage or current suitable for forming such a battery, i.e. to generate an interface electrode surface layer (SEI or CEI) on at least one electrode of the battery 5; a control unit 4, which may for example be a microprocessor unit, configured to control the operation of the plurality of controlled power supplies 2 so as to generate for each battery 5 the respective modulated voltage or current required for the formation process.

[0011] In the example of the formation board shown in Figure 1 , there are four controlled power supplies 2 which are supplied by their respective input terminals on which a supply voltage is made available, which can be either a mains voltage or a regulated DC voltage. The output terminal 6 of each power supply 2 is connected to the charging connector 7 of a respective battery 5 to be formed, so each power supply 2 is connected to only one respective battery 5. In an optional aspect, the power supplies 2 are coupled to their respective inputs through the interposition of upstream switches, whose function is to disconnect the respective power supply 2 from the input terminal A in order not to introduce unacceptable electrical disturbances on the upstream network, and to disconnect the downstream part in the event of an electrical fault. Similarly, the batteries 5 to be formed can optionally be connected to the controlled power supplies 2 via the interposition of downstream switches, in the event of a risk to the integrity of the power supplies 2 or batteries 5.

[0012] In accordance with a first aspect of the invention, an improved device for forming a plurality of rechargeable batteries is defined in claim 1 . The applicant noted that it is advantageous to be able to connect more than one power supply to each battery to be formed, and to be able to change how many and which power supplies are connected to which batteries even while the battery formation process is in progress.

[0013] According to an aspect, the device of this disclosure can be used to allow the formation of batteries in different formats (and thus requiring different amperages) by varying only the configuration of the bidirectional switches on the auxiliary board.

[0014] According to an aspect, the device of this disclosure allows the formation process to be performed using multiple power supplies simultaneously on a single battery, possibly modifying the number of power supplies connected to each battery as it is being formed, due to an auxiliary board comprising a plurality of output connectors, wherein each output connector is configured to be directly connected to a respective charge connector of each battery, as well as a plurality of bidirectional switches that can be individually opened / closed to define electrical conduction paths between the output terminal of each power supply of the formation board and a charge connector of each battery to be subjected to the formation process.

[0015] According to an aspect, the auxiliary board may also comprise an additional connector configured to be connected to an electrical component external to the auxiliary board. Preferably, the auxiliary board comprises third bidirectional switches defining respective test electrical conduction paths to connect each of the output terminals or each charging connector of the plurality of batteries to the additional connector.

[0016] According to an aspect, the formation board and the auxiliary board can be made in an integrated form on a common board.

[0017] According to an aspect, the electrical component external to the auxiliary board may be, for example, another auxiliary board of another similar device so that two or more auxiliary boards are connected in parallel to one and the same formation board, or this external electrical component may even be a battery testing device to monitor the evolution of the formation process. In accordance with a second aspect of the invention, a formation method of a plurality of batteries uses the formation device of the first aspect of the present disclosure, and comprises the operations of: connecting one charging connector of each battery to a respective output connector of the device's auxiliary board so that the auxiliary board's bidirectional switches define electrical conduction paths between the output terminals of the formation board's power supplies and the charging connector; before or during the implementation of the formation process and using the formation board control unit, individually closing or opening each bidirectional switch of the auxiliary board so as to close or open a respective electrical conduction path.

[0018] According to an aspect, the method of this disclosure may also comprise a step of measuring an internal resistance of a battery to be tested, wherein the measurement is obtained through the following operations: closing a first bidirectional switch connecting the output connector, connected to the charging connector of the battery to be tested, to the respective output terminal of a power supply called the main power supply, and at least a second bidirectional switch connecting said respective output terminal of the main power supply to at least one other output terminal of at least one other power supply, called the auxiliary power supply, so that the respective output terminals of the at least one main power supply and the at least one auxiliary power supply are shorted to each other, wherein the at least one second bidirectional switch is chosen so that the sum of a maximum current deliverable by the at least one auxiliary power supply and a maximum current deliverable by the main power supply is not less than a test current value required to measure the internal resistance of the battery to be tested; with the main power supply and at least one auxiliary power supply, supplying the battery to be tested with a current with a time profile starting from a base current value and increasing to the test current value over a time interval; detecting an increase in charge voltage of the battery to be tested that occurred over that time Interval; measuring the internal resistance as the ratio of the voltage increase to the difference between the test current value and the base current value.

[0019] The first switch and the second switch can be closed in any time order.

[0020] According to an aspect, the batteries on which the methods of this disclosure are performed are lithium batteries.

[0021] The term battery or lithium battery refers to an assembly consisting of at least one anode, one cathode, a possible dielectric separator interposed between the anode and cathode, and an electrolyte, to be subjected to a formation process. The term formation process refers to a process in which a battery is subjected to charge / discharge / recharge cycles. This process is necessary to activate internal electrochemical phenomena within the batteries such that the anodes are covered by the so-called “Solid Electrolyte Interphase” (SEI), which is necessary for the correct electrical operation of the battery itself, and is carried out after the mechanical assembly of the battery and before its standard use. The currents applied during charge / discharge / recharge cycles, measured in amperes, are numerically of a lower order of magnitude than the number expressing the total capacity in Ah of the battery. For example, when a battery has a capacity of 1 Ah, the maximum currents applied are about 0.1 to 0.2 amperes. Charge / discharge / recharge cycles are implemented for such a time (e.g. 12-24 hours) to reach maximum voltage, minimum voltage, and then return the battery to a known state of charge, typically 80%.

[0022] Further embodiments are defined in the appended claims.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 shows a known formation board for a plurality of rechargeable batteries having a plurality of power supplies controlled by the same control unit.

[0025] Figure 2 shows a device of this disclosure for forming a plurality of rechargeable batteries, comprising a formation board and an auxiliary board controlled by the formation board control unit.

[0026] Figure 3 shows an auxiliary board for a device of this disclosure, having an additional connector configured to be connected to a battery testing device subjected to a formation process.

[0027] Figure 4 shows example time graphs of a battery voltage and current during a DC / IR test.

[0028] DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0029] An illustrative embodiment of a device of this disclosure for forming a plurality of rechargeable batteries 5 is shown in Figure 2, wherein the same elements present in the known formation board of Figure 1 are designated by the same numerical references. In addition to having a formation board, the formation device of this disclosure also has an auxiliary board 8, comprising:

[0030] - a plurality of output connectors 9, wherein each output connector 9 of the output connectors 9 is configured to be connected directly to a respective charge connector 7 of each battery 5,

[0031] - a plurality of bidirectional switches 10a, 10b, configured to be individually opened / closed to define electrical conduction paths between the output terminal 6 of each power supply 2 and each output connector 9. In addition, the control unit 4 of the formation board is programmed so that each of the bidirectional switches 10a, 10b, of the auxiliary board 8 can individually close / open a respective electrical conduction path. The fact that the same control unit 4 of the formation board also controls the bidirectional switches 10a, 10b of the auxiliary board 8, allows the formation device of this disclosure to determine whether the same battery 5 is to be formed by two or more power supplies 2 at the same time.

[0032] According to an aspect, illustrated in the example in Figure 3, the auxiliary board 8 has first bidirectional switches 10a connecting respective output terminals 6 to corresponding output connectors 9, as well as second bidirectional switches 10b connecting two respective output terminals 6 to each other. In Figure 3, the second switches 10b are connected upstream of the first switches 10a, but could optionally also be connected downstream of the first switches 10a, i.e. between the switches 10a and the output connectors 9.

[0033] Thanks to the presence of the second bidirectional switches 10b, it is possible to connect the output terminals 6 of two or more power supplies 2 together so that they cooperate to supply current to form the same battery 5. In the illustrative and non-limiting form of Figure 3, for simplicity's sake only three second bidirectional switches 10b are shown for connecting the output terminals 6, which in the example considered are only four. More generally, the auxiliary board 8 can conveniently comprise as many separate second bidirectional switches 10b as there are different possible pairs of output terminals 6, so that each output terminal 6 can be short-circuited to another output terminal by closing only a respective second bidirectional switch 10b.

[0034] A significant advantage of the configuration of the control unit 4 is that it can also implement the so-called DC / IR (“Direct Current Internal Resistance”) test. As illustrated in the exemplifying time diagrams in Figure 4, to perform the DC / IR test on a battery, a charging current is increased, for example, by a relatively large amount ΔVrelative to a formation current (from an initial value Lbeforestep to a final value Lafterstep) over a relatively short measurement time interval, and the resulting voltage increase ΔV at the terminals of the battery to be tested is measured at the end of this measurement time interval. The voltage increase during the measurement time interval is substantially proportional to the current increase because, as illustrated in the graphs, the electrochemical phenomena triggered by the current increase have longer response times, so the internal resistance can be measured as the ratio of the voltage increase ΔV (between the final value V_afterstep and the initial value V_oeforestep) to the charge current increase A / . By using broad signals, it is possible to detect problems with the batteries 5 that would otherwise go unnoticed. For example, to carry out the DC / IR test of a battery 5, it may be necessary to supply the battery 5 to be tested with a current Lafterstep equal to three times a current that can be delivered for one hour by the battery (i.e. “3C” in technical jargon, where the quantity “C” is determined by the electrical capacity of the battery expressed in Ah). If, however, the power supplies 2 of a formation board are configured to deliver a maximum current of 1 C, then each of them alone cannot perform the DC / IR test. In fact, in the known devices of Figure 1 , it is necessary to disconnect the batteries 5 from the formation board to perform the DC / IR test.

[0035] Otherwise, In the device of this disclosure illustrated in Figure 2, the control unit 4 can reconfigure the bidirectional switches 10a, 10b of the auxiliary board 8 so that all four power supplies 2 cooperate in parallel to supply the required Lafterstep current to a battery 5 to be tested, allowing the control unit 4 itself to perform the DC / IR test. According to a process of this disclosure of performing the DC / IR test on a battery 5 using the device described above, the foliowing steps are performed: a first bidirectional switch 10a is closed which connects the output connector 9 connected to the charging connector 7 of the battery 5, to the respective output terminal 6 of a power supply 2 known as the main power supply 2, at least a second bidirectional switch 10b is closed which connects this respective output terminal 6 of the main power supply 2 to another output terminal 6 of another power supply 2, known as the auxiliary power supply 2, so that the output terminals 6 of the main power supply and the secondary power supply are shorted to each other, wherein the at least a second bidirectional switch 10b is chosen so that the sum of a maximum current deliverable by the auxiliary power supply and a maximum current deliverable by the main power supply is not less than a maximum current required to perform the DC / IR test on that battery 5.

[0036] It Is therefore understood that the fact that it is the control unit 4 that reconfigures the bidirectional switches allows the device of this disclosure to not only perform the forming process, but also to perform the DC / IR test to check its progress without being forced to disconnect the batteries 5 to connect them to a dedicated device.

[0037] It is to be understood that the DC / IR test can be repeated several times during the formation process.

[0038] Another test, which can be performed on batteries 5 with the auxiliary board 8 of this disclosure, is the so-called AC / IR for measuring the internal resistance of batteries 5 in AC. Typically, this test is conducted by injecting an alternating current lac with an amplitude of approximately 100mA into a battery to be tested and detecting Vac voltage fluctuations on the battery at the same frequency. Representing the current lac and the voltage fluctuations Vac by respective phasors, the value of the battery's internal resistance is provided by the real part of the Vac / lac complex impedance. Due to the fact that the auxiliary board has a plurality of output connectors 9 and the control unit 4 of the auxiliary board can individually open / close the bidirectional switches 10, the control unit 4 can activate electrical conduction paths to connect to the output terminals 6 of the power supplies 2 only those output connectors 9 that are effectively connected to respective charging connectors 7 of the batteries 5, leaving the output connectors 9 that are not connected to any charging connectors 7 disconnected. In addition, the bidirectional switches 10a, 10b, of the auxiliary board 8 can be configured so that several power supplies 2 can cooperate to perform the process of forming the same large-capacity battery 5, each power supply 2 supplying a portion of the current to be delivered to the battery 5.

[0039] According to an aspect illustrated in Figure 3, the auxiliary board 8 also comprises an additional connector 11 connected to at least one of the output terminals 6 via a respective third bidirectional switch 10c and configured to be connected to an electrical component external to the auxiliary board. For simplicity, only a third bidirectional switch 10c has been shown in the example in Figure 3, but the auxiliary board 8 could comprise a plurality of separate third bidirectional switches 10c to connect the additional connector 11 selectively with each output terminal 6.

[0040] According to an aspect, this external electrical component can be another auxiliary board, so that two or more auxiliary boards can be connected in parallel to the same formation board. According to another aspect, this external electrical component can even be a test equipment (not shown) of batteries 5 subjected to a formation process. In the illustrated embodiment, the bidirectional switches 10 of the auxiliary board 8 also define electrical conduction paths and can be activated / deactlvated by the same control unit 4 of the formation board, to connect each output connector 9, which is connected to a respective charging connector 7 of the batteries 5, to the additional connector 11. With this configuration, the control unit 4 can temporarily reconfigure the auxiliary board 8 so that each battery 5 is accessible via the additional connector 1 1 , e.g. to allow it to receive power from a different power supply from those on the respective formation board.

[0041] Obviously, the bidirectional switches 10a, 10b, 10c, must be suitably dimensioned so that they can conduct currents with the required intensity without damage.

[0042] According to an aspect illustrated in Figure 2, the formation board and auxiliary board 8 are made in an integrated form on the same common electronic board.

[0043] In the illustrative embodiment of Figure 2, the formation board of the device of this disclosure optionally also comprises first protection switches 1 controlled by the control unit 4, wherein each first protection switch 1 is configured to connect / disconnect a respective power supply 2 controlled by the power supplies 2 controlled to / from the input terminal A of the formation board.

[0044] According to an aspect illustrated in Figure 2, second protection switches 3 controlled by the control unit 4 are optionally installed on the formation board, wherein each second protection switch 3 is configured to connect / disconnect the respective controlled power supply 2 to / from the auxiliary board 8.

Claims

CLAIMS1 . Device for forming a plurality of rechargeable batteries (5), comprising: a formation board comprising: an input terminal (A) on which a supply voltage is made available; a plurality of bidirectional controlled power supplies (2), each power supply (2):- being able to be supplied through said input terminal (A),- having at least one respective output terminal (6), which can be connected to a charging connector (7) of each battery (5) of said batteries (5),- being configured to generate, on said respective output terminal (6), a respective modulated voltage or current suitable for forming said battery (5); a control unit (4) configured to control the operation of said plurality of bidirectional controlled power supplies (2) so as to generate for each batter (5) of said batteries (5) said respective modulated voltage or current; the device also comprising: an auxiliary board (8), comprising:- a plurality of output connectors (9), wherein each output connector (9) of said output connectors (9) is configured to be connected directly to a respective charge connector (7) of each battery (5) of said plurality of batteries (5),- a plurality of bidirectional switches (10a, 10b), configured to be individually opened / closed to define electrical conduction paths between said output terminal (6) of each bidirectional controlled power supply (2) of said bidirectional controlled power supplies (2) and each connector of said output connectors (9); wherein the control unit (4) of the formation board is also configured to individually close / open each of said bidirectional switches (10a, 10b) so as to close / open a respective electrical conduction path of said electrical conduction paths.

2. Device according to claim 1 , wherein said plurality of bidirectional switches (10a, 10b) comprises: first bidirectional switches (10a), each connecting a respective output terminal (6) of said output terminals (6) with a respective output connector (9) of said output connectors (9); second bidirectional switches (10b), each connecting a respective pair of said output terminals (6).

3. Device according to any one of the preceding claims, wherein said auxiliary board (8) further comprises an additional connector (11 ) configured tobe connected to an electrical component external to said auxiliary board, wherein said auxiliary board comprises third bidirectional switches (10c) defining respective electrical test conduction paths for connecting each of said output terminals (6) or each output terminal (9) of the plurality of batteries (5) to said additional connector (11 ).

4. Device according to one of the preceding claims, wherein which the formation board and the auxiliary board (8) are made in an integrated form on a common electronic board.

5. Device according to any one of the preceding claims, wherein the formation board comprises first protection switches (1 ) controlled by said control unit (4), wherein each first protection switch (1 ) of said first protection switches (1 ) is configured to connect / disconnect a respective controlled power supply (2) of the controlled bidirectional power supplies (2) to / from said input terminal (A) of the formation board.

6. Device according to any one of the preceding claims, wherein the formation board comprises second protection circuit breakers (3) controlled by said control unit (4), wherein each second protection circuit breaker (3) of said second protection circuit breakers (3) is configured to connect / disconnect a respective controlled power supply (2) of said controlled bidirectional power supplies (2) to / from the auxiliary board (8).

7. Method of forming a plurality of batteries (5), comprising the following operations: supplying and installing a device according to one of the preceding claims; connecting a charging connector (7) of each battery (5) of said plurality of batteries (5) to a respective output connector (9) of the auxiliary board (8) of the device so that the bidirectional switches (10) of the auxiliary board (8) define electrical conduction paths between the output terminals (6) of the bidirectional controlled power supplies (2) of the formation board and said charging connector (7); before or during the execution of said formation process and using the control unit (4) of the formation board, individually closing or opening each of said bidirectional switches (10a, 10b) so as to close or open a respective electrical conduction path of said electrical conduction paths.

8. Method according to the preceding claim, comprising the following operations: closing a first bidirectional switch (10a) connecting the output connector (9) connected to the charging connector (7) of a battery (5) to be formed, to the respective output terminal (6) of a bidirectional power supply (2) called the main power supply, and closing at least a second bidirectional switch (1 Ob) connecting said respective output terminal (6) of the main power supply (2) to at least another output terminal (6) of at least one other bidirectional power supply (2), called the auxiliary power supply, so that the output terminals (6) related to the main power supply and the auxiliary power supply are short-circuited with each other, wherein the at least one second bidirectional switch (10b) is chosen so that the sum of a maximum current deliverable by the at least one auxiliary power supply and a maximum current deliverable by the main power supply is not less than a value of a formation current required to form said battery (5); with said main power supply and said at least one auxiliary power supply, providing the battery (5) to be tested with a current suitable for performing a formation process.

9. Method according to claim 7, comprising a step of measuring an internal resistance of a battery (5) to be tested of said plurality of batteries (5) through the following operations: closing a first bidirectional switch (10a) connecting the output connector (9) connected to the charging connector (7) of the battery (5) to be tested, to the respective output terminal (6) of a bidirectional power supply (2) called the main power supply, and closing at least a second bidirectional switch (10b) connecting said respective output terminal (6) of the main power supply (2) to at least another output terminal (6) of at least one other bidirectional power supply (2), called the auxiliary power supply, so that the respective output terminals (6) of the main power supply and the auxiliary power supply are short-circuited with each other, wherein the at least one second bidirectional switch (10b) is chosen so that the sum of a maximum current deliverable by the at least one auxiliary power supply and a maximum current deliverable by the main power supply is not less than a test current value (Lafterstep) required to measure the internal resistance of said battery (5) to be tested; with said main power supply and said at least one auxiliary power supply, supplying the battery (5) to be tested with a current with a time profile startingfrom a base current value (Lbeforestep) and Increasing to the test current value (Lafterstep) over a time interval; detecting an increase in charging voltage (deltaV) of said batery (5) to be tested that occurred during said time interval; measuring said internal resistance as the ratio between said voltage increase and the difference between said test current value (Lafterstep) and said base current value (I... beforestep).

10. Method according to any one of claims 7 to 9, wherein said batteries (5) of said plurality of batteries (5) are lithium batteries.

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