Method and apparatus for the formation of electrochemical cells for batteries

Abstract

The present invention relates to a method for the formation of a plurality of groups of electrochemical cells (30) for batteries comprising supplying direct current electrical energy to the plurality of groups of electrochemical cells (30) by respective power devices (20) of a plurality of bidirectional transmission power devices, the power devices (20) apply to the respective group of electrochemical cells (30) a variable voltage or current, wherein the power devices (20) are configured to exchange direct current power with one another; executing a formation cycle (42a-42f) on each group of cells of the plurality of groups of cells (30), wherein each formation cycle (42a-42f) comprises a plurality of charging steps (43), a plurality of discharging steps (44) and a plurality of pause steps (45), wherein any one charging step (43) has a non-zero current intensity and a first duration time, any one discharging step (44) has a non-zero current intensity of opposite direction with respect to the charging step (43) and a second duration time and any one pause step (45) is at zero current and has a third duration time; wherein executing a respective formation cycle (42a-42f) on each group of cells of the plurality of groups of cells (30) comprises: executing formation cycles at a respective initial execution time, wherein the initial execution times of at least two formation cycles (42a-42f) are temporally offset with respect to each other and / or lengthening the third duration time of at least one pause step (45) of at least one formation cycle (42a-42f). The present invention also relates to an apparatus for the formation of groups of electrochemical cells (30).

Description

[0001] METHOD AND APPARATUS FOR THE FORMATION OF ELECTROCHEMICAL CELLS FOR BATTERIES

[0002] DESCRIPTION

[0003] The present invention finds particular application in the production of secondary batteries, preferably rechargeable lithium batteries.

[0004] In the production of lithium electrochemical cells, after mechanical assembly operations of the electrochemical cells, the electrochemical cells must undergo electrical operations that lead to electrochemical phenomena inside the electrochemical cells such that a film is gradually built up that forms on the surface of the electrodes (anodes). This film is called "Solid Electrolyte Interphase" (SEI). These operations are known in the technical sector by the term "formation" of electrochemical cells. The formation cycle is the process of consecutively charging and discharging a cell after it has been assembled. During this process, a relatively low direct current is used.

[0005] Typically, the electrochemical cell formation cycle is carried out by applying currents of 0.1 -0.2 C for predetermined time intervals separated by predetermined time intervals in which the cell does not receive current. The magnitude "C", or cell capacity, indicates the magnitude of electrical energy expressed in Ampere-hours (Ah). For example, for a cell capacity of 2 Ah, the magnitude C is 2 A. The values of the applied currents, the charging / discharging times and the number of repetitions of the various formation cycles depend on the type of battery and each battery manufacturer has developed its own "recipe" defined by the formation cycle.

[0006] In view of the time needed for the formation operations which typically require a sequence of charging / discharging cycles of relatively long duration (e.g. of the order of 5-24 hours), such operations are executed simultaneously on multiple groups of cells. Typically, in a formation plant, groups of electrochemical cells are arranged in formation units configured to accommodate a plurality of groups of cells, for example 6 to 12, in respective housings. In the formation units, each group of cells is arranged on a respective tray housing a plurality of cells typically arranged in a matrix pattern. The group of cells is connected, for example through electrical cables, to electronic devices suitable for implementing the charging / discharging cycles of the electrochemical cells.

[0007] Figure 1 schematically illustrates a portion of a formation cycle 29 of an electrolytic cell to indicate certain parts that define the cycle. The formation cycle 29 is represented by a variable direct current whose direction of the current varies over time. The current values can be positive, negative or zero. The zero of the current, i.e. the value of zero current, is represented by the dotted line 58.

[0008] The formation cycle 29 comprises a sequence of charging-discharging cycles 59. Each charging-discharging cycle of the formation cycle comprises a charging step 54 followed by a discharging step 55, wherein the charging step and the discharging step have opposite current intensity. In the example, a positive current above the zero line and a negative current below the zero line are assumed in a non-limiting manner. The current, positive or negative, intercepts the zero at current reversal points.

[0009] In a charging-discharging cycle, the charging step 54 is temporally separated from the next neighbouring discharging step 55 by a pause step 57 at zero current. In turn, the discharging step 57 is temporally separated from the charging step 55 of the subsequent charging-discharging cycle by a pause step at zero current. In particular, the charging and discharging steps are arranged in sequence and are interspersed with a respective pause step. During the pause step 57, no voltage or current is applied to the cells of the group of electrochemical cells.

[0010] The charging step 54 and the discharging step 55 have a respective first and second time duration defined by the width of the step 51 , which is referred to below as the charging duration (or first time duration) and the discharging duration (or second time duration) respectively. The charging duration or discharging duration of a step can be indicated as a completion percentage from 0% to 100%. The pause steps have a third duration (or third time duration).

[0011] In the Applicant's experience, the energy management of the formation operations uses AC / DC electrical power supplies which are connected at the input to the service power grid and at the output to respective power devices that supply, in direct current, respective groups of cells. In order to reduce the dissipation of a part of the electrical energy, the Applicant has considered a sizing of the voltages / currents by using bidirectional AC / DC electrical power supplies in communication upstream with the AC power grid and downstream with respective DC power devices in a number equal to the AC / DC power supplies. The Applicant has however noted that, although such a configuration simplifies the layout of the system, the use of a plurality of bidirectional AC / DC electrical power supplies, typically in a number equal to the groups of electrochemical cells to be formed, considerably increases the cost of the apparatus for the formation of the electrochemical cells.

[0012] Typically, the same charging / discharging formation cycle is applied to electrochemical cells so that all the cells are formed in the same way following a particular, predefined formation recipe.

[0013] The Applicant noted that the electrical sizing for the formation of a plurality of groups of cells housed in the formation unit must take into account a possible synchrony or near-synchrony between the charging phases applied to the cells of the respective cell trays, e.g. all cell trays start the formation cycle at the same time. Therefore, the electrical dimensioning should be such that it supplies and / or absorbs the current of the entire group of cells.

[0014] The Applicant noted that a power exchange between a plurality of DC electrical power devices supplying respective groups of cells would make possible a redistribution of current between the groups of cells, minimizing energy exchanges between the groups of cells and the power grid.

[0015] In particular, the Applicant realised that the provision of a plurality of DC power devices with bi-directional transmission of energy flow would make it possible to supply power to respective groups of cells by exchanging energy between these groups of cells which may be at different stages of the formation cycle. In particular, the Applicant thus realised that the provision of a time offset in the execution of formation cycles between groups of electrochemical cells by the power devices would allow for optimization of the redistribution of exchanged power. In other words, an optimization of the redistribution of the exchanged power makes it possible to minimize energy exchanges between the groups of cells and the power grid.

[0016] For example, a time offset between formation cycles could make a discharge phase of the formation cycle of one group of cells at least partially overlap in time with a charge phase of the formation cycle of another group of cells, thus reducing energy consumption.

[0017] In accordance with a first aspect of the present invention, a method is provided for the formation of a plurality of groups of electrochemical cells for batteries.

[0018] Preferably, the method comprises providing direct current electrical power to the plurality of groups of electrochemical cells by respective power devices of a plurality of bidirectionally transmitting power devices, the power devices being configured to apply a variable voltage or current to the respective group of electrochemical cells, wherein the power devices are configured to exchange direct current power with each other.

[0019] Preferably, the method comprises executing a respective formation cycle on each group of cells of the plurality of groups of cells.

[0020] Preferably, each formation cycle comprises a plurality of charging steps, a plurality of discharging steps and a plurality of pause steps, wherein any one charging step has non-zero current intensity and a first time duration, any one discharging step has non-zero current intensity and opposite direction to the charging step and a second time duration and any one pause step is zero current and has a third time duration.

[0021] Preferably, executing a respective formation cycle on each group of cells of the plurality of groups of cells comprises executing the formation cycles at a respective initial execution time, wherein the initial execution times of at least two formation cycles are temporally offset with respect to each other. Alternatively, or in combination with the initial offsetting of at least two formation cycles, preferably the third duration time of at least one pause step of at least one formation cycle is lengthened in time.

[0022] In accordance with a second aspect of the present invention, there is provided an apparatus for the formation of a plurality of groups of electrochemical cells for batteries.

[0023] Preferably, the apparatus comprises a plurality of bidirectional transmission power devices, wherein each power device is configured to electrically couple to a respective group of cells of a plurality of groups of electrochemical cells and to apply to the group of electrochemical cells a variable voltage or current.

[0024] Preferably, an electronic controller is connected to the plurality of power devices and programmed to cause each power device to execute a respective formation cycle on a respective group of cells of the plurality of groups of cells, wherein each formation cycle comprises a plurality of charging steps, a plurality of discharging steps and a plurality of pause steps, wherein any one charging step has a non-zero current intensity and a first duration time, any one discharging step has a non-zero current intensity of opposite direction with respect to the charging step and a second duration time and any one pause step is at zero current and has a third duration time.

[0025] Preferably, the initial execution times of the respective formation cycles are temporally offset with respect to each other.

[0026] Alternatively or in combination, preferably the third duration time of at least one pause step of at least one formation cycle is temporally lengthened.

[0027] In an embodiment, the offset between the respective initial execution times of the formation cycles can be implemented by starting the execution of formation cycles, different from a first formation cycle that is executed at an initial execution time (by convention at time zero), at a respective initial delay time interval, where the delay time intervals are different in value from each other. In particular, the initial delay time intervals can be selected in such a way as to achieve a reduction in the energy consumption of electrical loads during the execution of at least an initial portion of the formation cycles.

[0028] A pause step at zero current means that the current at the step is essentially zero.

[0029] In an embodiment, the initial delay time intervals are selected in such a way that the algebraic sum of the absorbed powers does not exceed a threshold value of charge current intensity or a threshold value of discharge current intensity.

[0030] The first duration times of the charging steps of the same formation cycle are not necessarily equal to each other but depend on the particular formation recipe being executed.

[0031] The second duration times of the discharging steps of the same formation cycle are not necessarily equal to each other but depend on the particular formation recipe being executed.

[0032] The third duration times of the pause time steps of the same formation cycle are not necessarily equal to each other but depend on the particular formation recipe being executed.

[0033] Preferably, each formation cycle executed on a respective group of cells of the plurality of groups of electrochemical cells comprises a plurality of chargedischarge cycles executed in sequence.

[0034] Preferably, the power devices of the plurality of power devices are electrically coupled to each other in parallel at the input and are configured to exchange direct current power with each other.

[0035] Preferably, a direct current distribution bus is provided and it is configured to transport direct current voltage and is electrically coupled at the input to each power device of the plurality of power devices.

[0036] Preferably, the distribution bus is electrically coupled at the output to at least one power supply.

[0037] Preferably, the at least one electrical power supply is electrically coupled at the input to an electrical source and at the output to the direct current distribution bus, wherein the at least one electrical power supply is configured to convert an electrical current at the input, having a first voltage, into an electrical current at the output, having a second voltage lower than said first voltage.

[0038] Preferably, the at least one power supply is configured to convert an electrical current at the input, having a first voltage, into an electrical current at the output, having a second voltage lower than said first voltage.

[0039] Preferably, the power devices are DC / DC converter devices, wherein a direct current at the input at a second voltage is converted to a direct current at the output at a third voltage directly applicable to electrochemical cells to operate a formation cycle.

[0040] The second voltage, i.e. the direct current voltage at the input to the power devices, is provided by AC / DC power supplies.

[0041] The bidirectional transmission between the direct current distribution bus and the respective power devices allows both absorption and transfer of power between the power devices. In general, the energy needed to supply the groups of cells associated with each direct current power device approximately corresponds to the algebraic sum of the powers absorbed and transferred by each power device of the plurality.

[0042] It is therefore possible to size the one or more electrical power supplies of the plurality of electrical power supplies at a lower output voltage (e.g. the second voltage), resulting in a reduction in equipment costs and consumption.

[0043] In accordance with the common meaning of the term, "algebraic sum" of power (or current or voltage) values means a sum that takes into account the sign of values that can be both positive and negative. The positive power values have flow of electrical energy in a direction going from the one or more power supplies towards the plurality of power devices and / or from the power devices towards the groups of cells. The negative power values have flow of electrical energy in a direction from the power devices towards the one or more power supplies and / or from the groups of cells towards the power devices.

[0044] The direct currents of the plurality of power devices circulate in the common DC distribution bus, allowing the plurality of DC power devices to communicate with each other without the need for a conversion of direct currents to alternating currents, i.e. without the need to redistribute power at the level of the AC / DC power supplies, e.g. at the connection of the power supplies with the AC power source.

[0045] Preferably, the input stages of the respective power devices are connected on the distribution bus.

[0046] In this way, and according to an embodiment, a bidirectional communication between the distribution bus and the AC / DC power supplies ensures that the power supplied to the AC / DC power supplies essentially corresponds to the algebraic sum of the powers received by the power devices.

[0047] For example, and according to an embodiment, it is possible to size one or more AC / DC power supplies of the plurality of power supplies at a lower voltage, resulting in lower costs and consumption.

[0048] In the event that the algebraic sum of the powers received by the distribution bus is positive, the “excess” power can be introduced into the AC power grid that supplies the apparatus for the formation of electrochemical cells.

[0049] For the purposes of redistributing excess power to the grid, it is sufficient that the DC distribution bus, in which the direct currents of the DC power modules flow in and out, is connected with at least one bidirectional transmission AC / DC power supply. The other AC / DC power supplies of the plurality of power supplies can be with unidirectional transmission.

[0050] According to an embodiment, at least one of the plurality of AC / DC power supplies is a bidirectional transmission power converter configured to supply and receive direct current to / from the DC distribution bus.

[0051] According to an embodiment, the DC distribution bus is a bar made of metal material that connects DC power devices in parallel. In one example, the distribution bus comprises a first and second bar with opposite polarities.

[0052] The Applicant observed that, during the execution of the plurality of formation cycles on the corresponding groups of cells, at a time interval following the initial execution times, the algebraic sum of the absorbed powers may exceed a threshold value of charge current intensity or a threshold value of discharge current intensity. The Applicant has therefore considered that it might be advantageous to introduce a time offset in one or more formation cycles such that an algebraic sum of power values less than or equal to the threshold value of charge or discharge current intensity is produced.

[0053] The Applicant considered that the formation cycle follows a predetermined pattern with reference to the number of charge-discharge cycles, the current intensity of each charging step and each discharging step and the width of each step (i.e. time duration of charge or discharge current). A time offset between different formation cycles could therefore not change the values and duration of the charging or discharging steps. The Applicant therefore understood that an offset during the execution of the plurality of formation cycles can be introduced, in at least one formation cycle, at the pause steps arranged between the charging and discharging steps of said at least one formation cycle. In this way, it is possible to optimize the redistribution of the exchanged power by minimising energy exchanges between the groups of cells and the power grid.

[0054] According to an embodiment, lengthening the third time duration of a pause step of a formation cycle of at least one group of cells is provided to optimize a redistribution of electric powers exchanged in direct current between the power devices.

[0055] According to an embodiment, lengthening the third time duration of a pause step of a formation cycle of at least one group of cells can be implemented as an alternative to temporally offsetting the initial execution times of at least two formation cycles with respect to each other.

[0056] The Applicant has also perceived that it would be useful, for the purpose of monitoring the exceeding of threshold values of the power absorbed or released by power devices during the execution of formation cycles, to monitor current intensity values over time.

[0057] Preferably, the plurality of power devices is housed in a drawer comprising a support structure.

[0058] Preferably, each power device of the plurality of power devices is connected to a respective contact group configured to establish an electrical connection between the power device and a respective group of cells of the plurality of electrochemical cells.

[0059] Preferably, each group of electrochemical cells is housed in a respective cell tray of a corresponding plurality of cell trays.

[0060] Preferably, the cell trays are transportable into and out of a plurality of drawer housings.

[0061] According to an embodiment, it is provided to detect the presence of one or more cell trays arranged at respective housings other than a first housing and electrically connected to respective power devices that are executing respective formation cycles.

[0062] According to an embodiment, it is provided to detect the presence of a new tray within the first housing operatively connected to a respective power device.

[0063] According to an embodiment, it is provided to determine the initial execution time of the formation cycle of the group of cells of the new tray as a function of the formation cycles being executed in the other cell trays.

[0064] An “electrochemical cell” is defined as an assembly composed of at least one anode, one cathode, a possible dielectric material separator interposed between the anode and cathode, and an electrolyte. A battery comprises at least one electrochemical cell.

[0065] "Formation” means a process in which an electrochemical cell is subjected to charging / discharging / recharging cycles. The currents applied during charging / discharging cycles, measured in Ampere, are numerically one order of magnitude less than the number expressing the total capacity in Ah of the electrochemical cell. For example, when an electrochemical cell has a capacity of 1 Ah, the maximum currents applied are about 0.1 - 0.2 Ampere. The charging / discharging / recharging cycles are implemented for a time (e.g., 12-24 hours) such that to reach maximum voltage, minimum voltage, and then bring back the electrochemical cell to a known state of charge, typically 80%.

[0066] "Drawer" means any support structure capable of supporting one or more bodies and inserted into a housing compartment, not necessarily closed on the sides and not necessarily slidable on guides or the like in order to be extracted from the housing compartment.

[0067] “Bi-directional transmission” of an electrical device, such as a power supply or power converter, means that the electrical device allows energy to flow in both directions, i.e. at the input or output to / from a further electrical device. Conventionally, transmission is defined by a direction between a “source” node (e.g. power device) and a “destination” node (e.g. group of electrochemical cells) via a line on which flows are bidirectional, i.e. they can be positive or negative. Positive energy flows are defined from the source node to the destination node, while negative flows are defined from the destination node to the source node. Energy or power can be transmitted and received along the line between the two electrical devices, but not simultaneously.

[0068] In its broadest meaning, "electronic controller" or "controller" is intended to include an electronic device or system that comprises one or more controllers and / or microprocessors that can be associated with the apparatus to cooperate with each other in controlling various functions and operations of the apparatus that can be based on hierarchical control logic. The electronic controller can be part of the CPU of a computer or other systems that require complex digital control logic.

[0069] In known ways, the electronic controller may include one or more electronic processors executing a software programme, one or more areas of processor- readable or executable memory, in which executable programmes, data, functions, look-up tables or other are stored. The software programme comprises programme code instructions for the execution of the method and system when the programme is executed on the electronic controller, e.g. a computer.

[0070] Further characteristics and advantages of the present invention will become clearer from the following detailed description of a preferred embodiment thereof, with reference to the appended drawings and provided by way of indicative and non-limiting example, wherein:

[0071] Figure 1 schematically illustrates a portion of an electrolytic cell formation cycle to indicate certain parts that define the cycle;

[0072] Figure 2 is a schematic representation of an apparatus for the formation of electrochemical cells for batteries in accordance with an embodiment;

[0073] Figure 3 schematically illustrates the formation cycles executed on cells of a respective plurality of groups of cells, in accordance with an embodiment;

[0074] Figure 4 illustrates the formation cycles of Figure 3 in a subsequent step with respect to the step of Figure 3;

[0075] Figure 5 schematically illustrates a plurality of formation cycles executed starting from the same cycle execution time;

[0076] Figure 6 is a schematic representation of a side view of a drawer configured to house a plurality of groups of electrochemical cells in accordance with an embodiment, and

[0077] Figure 7 illustrates the drawer of Figure 6 at a later point in time.

[0078] The representations in the accompanying figures do not necessarily have to be understood in scale and do not necessarily respect the proportions between the various parts. In the figures, the same or similar elements of different embodiments will be indicated with the same reference numbers.

[0079] Figure 2 is a block diagram of an apparatus 10 for the formation of electrochemical cells for batteries, in particular for rechargeable batteries, in accordance with an embodiment.

[0080] The apparatus 10 comprises at least one electrical power supply 36-39 electrically connected to an electrical energy source 15, for example an external source, such as an industrial power grid operating at a substantially constant voltage of 400 V to 800 V. The at least one electrical power supply 36-39 is configured to convert an electrical current at the input, having a first voltage (for example corresponding to the voltage of the power grid), into an electrical current at the output, having a second voltage, lower than said first voltage. For example, the second voltage is between 12V and 48V, for example 12V.

[0081] In the embodiment of Figure 2, a plurality of electrical power supplies 36-39 are connected, at the input, to the external electrical source 15, each electrical power supply being configured to convert electrical energy at the input having the first voltage into the second voltage. For example, each electrical power supply 36- 39 is electrically connected at the input to an alternating-current power supply line 13 connected to the external electrical source 15. Preferably, the power supplies 36-39 receive electrical energy at a same voltage.

[0082] The apparatus 10 further comprises a plurality of direct current (DC) power devices 20, hereinafter also referred to as power devices. Each power device 20 is configured to supply electrical power to a group of cells 30 of a corresponding plurality of groups of electrochemical cells. In particular, each power device 20 is electrically coupled at the output to a respective group of electrochemical cells 30.

[0083] Each power device 20 is further configured to apply to the respective group of electrochemical cells 30 a voltage or current such as to allow the partial formation of the cells of the group of cells.

[0084] In the non-limiting example, 6 power devices 20 configured to be electrically coupled to 6 respective groups of electrochemical cells 30 are depicted.

[0085] In embodiments, the number of power devices 20 is comprised from 2 to 12, in particular from 4 to 12, for the formation of corresponding groups of electrochemical cells. In embodiments, the electrochemical cells are lithium-ion electrochemical cells, typically cylindrical cells.

[0086] The power devices 20 of the plurality are electrically coupled to each other in parallel and are configured to exchange direct current power with each other. In particular, the power devices of the plurality of power devices 20 are electrically coupled to each other in parallel input and are configured to exchange direct current input power with each other.

[0087] The direct electric current at the output from the electrical power supplies 36-39 is such as to be usable by the power devices 20. In an embodiment, each electrical power supply 36-39 is an AC / DC converter configured to convert an AC voltage received from the power grid into a DC voltage.

[0088] However, in a different embodiment, it may be foreseen that the one or more electrical power supplies 36-39 receive a first direct current voltage from a direct current source. In such an embodiment, the electrical power supplies 36-39 are configured for DC / DC conversion and for providing at the output direct current power at the second voltage.

[0089] In the following description, reference will be made, in a non-limiting way, to AC / DC electrical power supplies 36-39.

[0090] The one or more electrical power supplies 36-39 are electrically connected at the output to a direct current (DC) distribution bus 16. In particular, the respective output stage of the one or more electrical power supplies 36-39 is electrically connected to the direct current distribution bus 16 configured to receive direct current at the second voltage. The distribution bus 16 "transports" the electrical energy received at the input from the electrical power supplies 36-39 and distributes it at the output to the plurality of power devices 20.

[0091] Each power device 20 is a bidirectional transmission device of the electrical energy flow, the flow being conceptually indicated with the bidirectional arrows 21. In particular, the input stages of the power devices 20 connected to the distribution bus 16 are configured both to receive input power and to transmit output power to / from the distribution bus 16.

[0092] The distribution bus 16 puts the power devices 20 in communication with each other allowing an exchange of power at the input. In this way, the power needed to supply the plurality of cells 30 substantially correspond to the algebraic sum of the powers absorbed by each power device 20 of the plurality.

[0093] For example, if in a time interval, a first power device 20 is supplying a first group of cells 30 with a positive energy balance (power transfer) while a second power device is supplying a second group of cells 30 with a negative energy balance (power absorption), it is possible for the first power device to provide the excess power to the second power device thereby reducing the overall energy requirement that must be delivered for the formation of the plurality of groups of cells 30.

[0094] In an embodiment, each power device 20 has a single input stage (not indicated in the figures) that is electrically connected with the distribution bus 16 and an output stage comprising a plurality of output channels (not indicated) for electrical connection with each cell of a respective group of cells 30.

[0095] Each power device 20 comprises a plurality of electrical energy flow bidirectional transmission DC / DC converters (not depicted in the figures) in a number corresponding to the plurality of cells of each group of electrochemical cells 30. Each DC / DC converter is configured to convert an electrical current received at the input at the second voltage into an electrical current at the output at a third voltage, lower than the second voltage and usable by each cell of the group of electrochemical cells 30.

[0096] Each bidirectional DC / DC converter of a power device 20 is electrically connected to a respective cell of the respective group of electrochemical cells 30. In particular and in ways known per se, each DC / DC converter of the power device 20, is configured to inject variable voltage into the respective cell in accordance with the values set by the formation cycle.

[0097] In one embodiment, each bidirectional transmission DC / DC converter of the power device 20 is a two-quadrant bidirectional converter, that is, it is configured to reverse the current injected into the cell in the two directions, without power reversal.

[0098] By way of example, each group of cells 30 comprises 64 electrochemical cells and the power device 20, connected to the group of cells, comprises 64 output channels for supplying the individual cells with a variable voltage (third voltage).

[0099] The variable voltage corresponds to a positive and negative variable current that defines a sequence of charging-discharging cycles according to a pattern defined by the formation cycle and in particular by the formation cycle which can be repeated so as to execute a formation pattern comprising one or more formation cycles executed in sequence. A formation protocol may, for example, consist of one formation cycle or comprise the repetition of 2-4 formation cycles. In the examples shown in the figures, reference will be made to a formation cycle for simplicity's sake.

[0100] Typically, the cells of the same electrochemical group of cells 30 synchronously execute the same formation cycle for each cell of the same group of cells. In this way, all the cells of a group of cells 30 start and finish the formation protocol substantially at the same time and can therefore be taken and transported to the subsequent steps of the process, for example to an "aging" phase.

[0101] If the algebraic sum of the powers received by the distribution bus 16 is positive at an interval of time, the "excess" power can be introduced into the AC power grid that supplies the apparatus 10. Thus, for the purposes of redistributing excess power to the grid, it is sufficient that the DC distribution bus 16, in which the direct currents of the direct current power devices 20 flow in and out, is connected with a single bidirectional transmission electrical power supply.

[0102] In one embodiment, an electrical power supply 39 of the plurality of electrical power supplies 36-39 has bidirectional transmission, indicated by double arrows 17 indicating energy exchange from / to the distribution bus 16 and from / to the electrical source 15. The other electrical power supplies 36-38 have unidirectional transmission, as indicated by arrows 19. In this way, it is possible to introduce the excess power into the power grid, conceptually indicated with the double arrow 12, without considerably increasing the costs of the apparatus.

[0103] The electrical connection between a power device 20 and the respective group of cells 30 may be implemented in ways known per se, for example by means of electrical cables connecting each cell of a group of cells 30 to the output channels of the respective power device 20.

[0104] In an embodiment, each power device 20 is electrically connected to a respective electrical contact group 25, hereinafter also referred to as a contact group, and configured to establish an electrical connection between the power device 20 and the respective group of cells 30. The contact group 25 is electrically connected to a respective power device 20. In particular, the contact group is connected to the plurality of bidirectional DC / DC converters of the power device 20 to establish an electrical connection between each cell of a group of electrochemical cells and a respective DC / DC converter.

[0105] As described in more detail below, and in accordance with an embodiment, the contact group 25 is integrally connected to the respective power device 20.

[0106] Each power device 20 comprises a control unit (not indicated in the figures) operatively connected to the electronic controller 50 and is configured to execute the formation cycles. The control unit can also execute functions of checking the integrity of the different electronic components and cells. Temperature detectors and / or meters of derived magnitudes such as the capacity may be present in each power device 20.

[0107] The electronic controller 50 is connected to the plurality of power devices 20 and is programmed to have each power device execute the formation cycle on the cells of the respective group of cells 30. In particular, the electronic controller 50 is connected to the respective control units of each power device 20. The information collected by the control units of the power devices is transmitted to the electronic controller 50 for the purpose of general supervision of the apparatus.

[0108] In an embodiment, the electronic controller 50 is further connected to the distribution bus 16 for a control of the voltage circulating within the bus and is connected to one or more electrical power supplies 36-39 (only the control line to the power supply 36 is indicated in the Figure).

[0109] In one embodiment, the plurality of power devices 20 is housed in a drawer 40 (Figures 6 and 7). The drawer 40 comprises a support structure 27 having a length along a longitudinal direction Y.

[0110] The drawer 40 may be arranged in a compartment of a more complex structure (not illustrated), for example a formation rack, comprising a plurality of compartments for housing respective drawers. The drawer 40 comprises a plurality of housings 24a-24f equal to the number of the power devices 20 of the apparatus 10.

[0111] The plurality of power devices 20 are housed in a corresponding plurality of housings 24a-24f. Each power device 20 is electrically connected to a respective electrical contact group 25, hereinafter also referred to as a contact group, of a corresponding plurality of contact groups 25 configured to connect each cell of a group of cells 30 to the respective power devices 20.

[0112] The groups of electrochemical cells 30 are housed on respective cell trays 35, wherein each cell tray 35 is transportable into and out of the drawer 40. The cell trays 35 are arranged at a respective housing 24a-24f of the drawer 40. In particular, the cell trays 35 are arranged near a respective electrical contact group 25, for the electrical coupling of the group of cells 30 with a respective power device 20. For example, the cell trays 35 are arranged on two side guides 32 connected to the support structure 27.

[0113] The cell trays 25 are configured so as to allow to the respective contact groups 25 an electrical connection with the respective groups of cells 30.

[0114] In one embodiment, each electrical contact group 25 is integral with a respective power device of the plurality of power devices 20.

[0115] Each electrical contact group 25, together with the integral power device 20, is configured to move in a direction transverse, in particular in a direction perpendicular Z, to the longitudinal axis Y, between a first operating position and a second operating position. In the first operating position, the contact group 25 is not electrically coupled to a group of electrochemical cells 30 and in the second operational operation the contact group is electrically coupled to the cells of the group of electrochemical cells. Figures 6 and 7 show the contact groups 25 housed in the respective housings 24a-24e in the second operating condition, while the contact group 25 in the housing 24f is in the first operating condition (a cell tray is absent).

[0116] To this end, a lifting mechanism, not illustrated and indicated in Figure 6 with a double arrow 34, can be provided at each housing 24a-24f for moving the contact group 25 along the axis Z.

[0117] Each power device 20 is electrically coupled to the distribution bus 16. The distribution bus 16 is mounted lengthwise on the support structure 27 of the drawer along the longitudinal axis Y so as to extend along the plurality of power devices 20.

[0118] The distribution bus 16 comprises at least one busbar made of metallic material configured to transport current and extending along the longitudinal axis Y.

[0119] In the embodiment of Figures 6 and 7 the distribution bus comprises a positive polarity busbar and a negative polarity busbar 16a, 16b, wherein the busbars are mounted parallel to each other lengthwise on the support structure 27 of the drawer 40.

[0120] The busbars 16a, 16b are for example made of aluminium.

[0121] In the non-limiting example of the figures, the busbars 16a, 16b are arranged on a first side (along the axis Y) of the drawer 40.

[0122] An arrangement of the power devices 20 side by side can promote a power exchange between the devices 30 without significant voltage losses.

[0123] In an embodiment, each power device 20 is connected to the busbars 16a, 16b by means of a respective electrical cable 23a, 23b configured to supply the input of each power device.

[0124] The provision of a common distribution bus arranged near the power devices allows a simplification of the arrangement of the apparatus as the power devices are supplied through an electrical connection with the busbars.

[0125] The distribution bus 16 is electrically connected to the one or more electrical power supplies 36-39 (not illustrated in Figures 6 and 7). The power supplies 36- 39 can be arranged near the drawer 40, for example at the compartment housing the drawer, and be connected, by means of an AC plug (not illustrated), to the socket of a service power grid supplying AC voltage as an external electrical source 15.

[0126] Figure 3 schematically illustrates the formation cycles executed on the respective groups of cells of a plurality of groups of cells 30, in accordance with an embodiment. The plurality of groups of cells 30 are indicated by V1 -V6 and the respective formation cycles by 42a-42f.

[0127] Each formation cycle 42a-42f comprises the same plurality of chargingdischarging cycles executed in sequence. Each charging-discharging cycle comprises a charging step 43 having a first time duration and a discharging step 44 having a second time duration, wherein the charging step and the discharging step have opposite current intensities (positive and negative). The charging step 43 is temporally separated from the discharging step by a pause step 45 at zero current having a third time duration. Neighbouring charging-discharging cycles are separated temporally by a respective pause step 45 at zero current. In particular, a pause step 45 is interposed between two subsequent neighbouring charging and discharging steps 43, 44 and between two discharging and charging steps 44, 43. In a non-limiting way, it is assumed that the charging step has positive current (above zero) and the discharging step has negative current. The current, positive or negative, intercepts the zero at current reversal points.

[0128] The electronic controller 50 is programmed to cause each power device 20 to execute a formation cycle on a respective group of cells of the plurality of groups of cells V1 -V6 at respective initial execution times in which at least two initial execution times are temporally offset with respect to each other.

[0129] The electronic controller 50 is further or alternatively programmed to cause each power device 20 to execute a formation cycle on a respective group of cells of the plurality of groups of cells V1 -V6 such that the third time duration of a pause step 45 of a formation cycle of at least one group of cells 30 (not illustrated in Figure 3) is lengthened.

[0130] The extent of the temporally lengthening of the third pause step 45 can be any length of time.

[0131] The pause step 45 by which the third time duration is lengthened with respect to the duration of the formation recipe can be any and of any formation cycle.

[0132] The number of pause steps 45 by which the third time durations are lengthened in relation to the duration of the formation recipe can be any and of any formation cycle. The choice of the pause step 45, their number, the formation cycle and the extent of the third time duration are chosen to optimize the redistribution of electrical power exchanged in DC between the power devices 20.

[0133] A possible embodiment of the electrochemical cell formation method may provide that prior to initiating the execution of the formation cycles of the respective groups of cells 42a-42f, the electronic controller 50 is configured to store a respective nominal formation cycle associated with the respective group of cells V1 -V6 of the plurality. Each nominal formation cycle comprises nominal formation cycle data associated with respective successive instants of time, wherein the instants of time comprise an initial nominal execution time. In particular, the electronic controller 50 is also configured to store a respective initial execution time associated with each formation cycle 42a-42f.

[0134] The nominal formation cycle data comprise a value and direction of current intensity, a step width of each charging step 43 or discharging step 44 (corresponding to the first and second duration time), and a width of each pause step (corresponding to the third duration time) between two neighbouring charging and discharging steps.

[0135] In the embodiment of Figure 3, after storing the formation cycles 42a-42f and their respective initial execution times, the electronic controller 50 is configured to execute the formation cycles 42a-42f at different initial execution times.

[0136] In the non-limiting example in the figure, the formation cycle 42a of a first group of cells V1 has an initial execution time to which can be taken as a reference, to = 0. The formation cycle 42b of the second group of cells V2 has an initial execution time temporally offset by a delay time interval Ato, i.e. the second group of cells V2 begins to execute the formation cycle at a time to + Ato. More generally, the formation cycles 42a-42f from the first to the sixth group of cells V2-V6 have respective initial execution times temporally offset with respect to each other by a respective value of delay time from Ato to 5Ato. The vertical dotted lines indicate the time position corresponding to the initial execution time of the respective groups of cells V1 -V6.

[0137] The values of the delay time between different formation cycles may not have a specific mathematical relationship as in the example described above, but be selected on the basis of a criterion aimed at producing a reduction in the energy consumption of electrical loads during the execution of at least an initial portion of the formation cycles of the groups of cells.

[0138] During the execution of the plurality of formation cycles on the corresponding groups of cells, at a time interval following the initial execution times, the algebraic sum of the absorbed powers may exceed a threshold value of charge current intensity or a threshold value of discharge current intensity.

[0139] For the purpose of controlling the exceeding of the threshold values of the algebraic sum of power in the execution of the formation cycles, a control of the relative current intensity values of the plurality of formation cycles over time is provided for in embodiments. In particular, the electronic controller 50 is configured to retrieve current intensity values and direction of each formation cycle of the plurality of stored nominal formation cycles, and is configured to determine whether the sum of the relative current intensity values at a time that is later than the initial execution time of each formation cycle, is greater than the charge current intensity threshold value or the discharge intensity threshold value.

[0140] With reference to Figure 3, it is assumed that, at a time ti, referred to hereafter as control time, following the respective initial execution times (t=0 to t=5Ato) of the formation cycles 42a-42f, the algebraic sum of the current intensity values of the formation cycles exceeds the predetermined threshold value of charge current intensity.

[0141] With reference to Figure 4, subsequent to having stored that at ti, subsequent to the respective initial execution times, the charge current intensity value is greater than the charge current intensity threshold value, the electronic controller 50 is configured to retrieve the current intensity values each formation cycle 42a-42f at the control time ti and to determine whether at least one formation cycle of the plurality of formation cycles has zero current intensity, i.e. is positioned at a pause step 45.

[0142] In the example, in the formation cycle 42d, the control time ti is arranged at a pause step 45. The electronic controller 50 is configured to modify at least one formation cycle of the plurality of formation cycles by inserting, at the control time ti, a zero-current stop time interval S1 . The duration of the stop time interval S1 defines the extent of the lenghtening of the pause step. The stop time interval S1 at zero current is selected so as to temporally offset the formation cycle 42d from the remaining formation cycles of the plurality of formation cycles 42a, 42b, 42c, 42e and 42f.

[0143] Thus, during the execution of the formation cycles 42a-42f, at control time ti, the algebraic sum of the current intensities has a value less than or equal to the threshold value of charge current intensity. The electronic controller 50 is configured, during the temporary stop S1 of the formation cycle 42d, to continue to execute the remaining formation cycles 42a, 42b, 42c, 42e and 42f.

[0144] At the end of the stop time interval S1 , the electronic controller 50 is configured to resume executing the formation cycle 42d.

[0145] In the example in Figures 3 and 4, the execution of each formation cycle 42a-42f started at different initial execution times so as to have an initial offset between the charge-discharge sequences.

[0146] However, irrespective of whether or not there is an initial offset of the start of the cycles and in accordance with an embodiment, a control on the current intensity values of the formation cycles can be provided. Figure 5 illustrates the plurality of formation cycles 42a-42f that are executed from the same initial execution time, t=0. At a control time ti>0, the algebraic sum of the current intensities exceeds the threshold value of charge current intensity. The electronic controller 50 is configured to include in the formation cycle 42f a stop time interval S2 at a pause step in order to bring the algebraic sum of the current intensities to a value less than or equal to the threshold value of charge current intensity. The stop time value S2 defines the value of the lengthening of the pause.

[0147] In the non-limiting example of Figures 6 and 7, five of the six housings, i.e. the housings 24a-24f, of the drawer 40 are occupied by respective cell trays 35. Figure 6 depicts a non-limiting configuration in which the drawer 40 receives a respective cell tray 35 in the housings 24a-24e, operatively coupled to the respective contact group 25 (second operating condition). In the housing 24f, which will be referred to in the following as first housing 24f, the contact group 25 is in the first operating condition as there is no cell tray. For example, the apparatus is waiting to receive a tray of cells 35.

[0148] The electronic controller 50 is configured to detect the absence of a cell tray in a first housing 24f of the plurality of housings 24a-24f of the drawer 40 and to cause a new cell tray 35a to be transported within the first cell housing 24f.

[0149] Figure 7 depicts a situation in which a new cell tray 35a has been transported to the housing 24f and has been connected to the respective contact group 25, i.e. in the second operating position. The electronic controller 50 is configured to detect the presence of the new tray 35a within the first housing 24f and to operatively connect the contact group 25 of the first housing 24f with the new tray 35a, in particular with the group of cells 30a of the new tray 35a. In the example in Figure 7, at the time of inserting the new tray 35a, the groups of cells 30 housed in the respective housings 24a-24e are executing respective formation cycles. The electronic controller 50 is configured to receive data on the presence of cell trays 35 housed in respective housings 24a-24e of the drawer 40 other than the first housing 24f.

[0150] After the contacting of the new cell tray 35a with the power device 20 of the first housing 24f, the electronic controller 50 is configured to receive, at a second control time t2, formation cycle information data of the one or more groups of cells 30 other than the group of cells 35a of the new tray 35a. The formation cycle information data of the groups of cells 30 housed in the trays 35 comprise a value and a direction of current intensity for each group of cells 35. Preferably, the formation cycle information data includes, in addition to the value and direction of current intensity, a step width of each charging or discharging step, and a duration of each pause step between two charging and discharging steps next to each other.

[0151] After receiving the formation cycle information data for the groups of cells 30, the electronic controller 50 is configured to determine whether, based on the formation cycle information data received from the groups of cells 30, the algebraic sum of the current intensity values of the formation cycles of the respective groups of cells 30 is greater than a charge current intensity threshold value or is greater than a discharge current intensity threshold value, and if said algebraic sum is greater than a charge current intensity threshold value or is greater than a discharge current intensity threshold value, execute the formation cycle of the group of cells of the new cell tray 35a at an instant of initial execution time subsequent to the second control control time t2 and selected such that the algebraic sum of the current intensity values of the groups of cells 30a of the new cell tray 35a and the groups of cells 30 of the one or more of the cell trays 35 housed in respective housings 24a-24e of the drawer 40 is less than or equal to the charge current intensity threshold value or the discharge current intensity threshold value.

[0152] The arrangement of the power devices 20 inside the drawer 40 represented in Figures 6 and 7 is not to be considered as limiting. For example, the power devices 20 could be arranged inside a respective housing 24a-24f upside down with respect to what is shown in the aforementioned Figures so as to have the respective contact group 25 below the power device 20. In this alternative configuration, the trays 35 enter and exit the drawer 40 in proximity to the respective contact groups 25, in a space of the housing 24a-24f arranged below the contact group 25. Similarly, whether the contact groups 25 face upwards or downwards, with reference to the direction Z, the distribution bus 16 can be arranged in a different position of the support structure 27 of the drawer 40 or not be part of the drawer structure, but be mounted near the drawer 40 inside the compartment housing the latter.

[0153] The person skilled in the art will recognize that it is possible to combine the various features of the above-described embodiments to obtain further embodiments, all falling within the scope of the present invention as defined by the following claims.

Claims

CLAIMS1 . Method for the formation of a plurality of groups of electrochemical cells (30) for batteries comprising supplying direct current electrical energy to the plurality of groups of electrochemical cells (30) by respective power devices (20) of a plurality of bidirectional transmission power devices, the power devices (20) being configured to apply to the respective group of electrochemical cells (30) a variable voltage or current, wherein the power devices (20) are configured to exchange direct current power with one another; executing a respective formation cycle (42a-42f) on each group of cells of the plurality of groups of cells (30), wherein each formation cycle (42a-42f) comprises a plurality of charging steps (43), a plurality of discharging steps (44) and a plurality of pause steps (45), wherein any one charging step (43) has a non-zero current intensity and a first duration time, any one discharging step (44) has a non-zero current intensity of opposite direction with respect to the charging step (43) and a second duration time and any one pause step (45) is at zero current and has a third duration time; wherein executing a respective formation cycle (42a-42f) on each group of cells of the plurality of groups of cells (30) comprises: executing the formation cycles at a respective initial execution time, wherein the initial execution times of at least two formation cycles (42a-42f) are temporally offset with respect to each other; or or in combination lengthening the third time duration by at least one pause step (45) of at least one formation cycle (42a-42f).

2. Method according to claim 1 , wherein the power devices (20) of the plurality of power devices (20) are electrically coupled one to another in parallel at the input and are configured to exchange direct current power with one another at the input.

3. Method according to claim 1 or 2, wherein the power devices of the plurality of power devices (20) are electrically coupled in parallel via a direct current distribution bus (16) configured to transport direct current electrical energy.

4. Method according to claim 3, comprising supplying direct current electrical power by at least one electrical power supply (36-39) electrically coupled at the input to an electrical source (15) and at the output to the direct current distributionbus (16), wherein the at least one electrical power supply (36-39) is configured to convert an electrical current at the input having a first voltage into an electrical current at the output having a second voltage lower than said first voltage.

5. Method according to one of the preceding claims, wherein lengthening the third time duration of a pause step (45) of a formation cycle of at least one group of cells (30) is to optimize a redistribution of electric powers exchanged in direct current among the power devices (20).

6. Method according to one of the preceding claims, wherein the plurality of power devices (20) are housed in a drawer (40) comprising a support structure (27), wherein each power device of the plurality of power devices (20) is connected to a respective contact group (25) configured to establish an electrical connection between the power device (20) and a respective group of cells of the plurality of electrochemical cells (30).

7. Method according to claim 6, wherein each group of electrochemical cells (30, 30a) is housed in a respective cell tray of a corresponding plurality of cell trays (35, 35a) that are transportable in and out to / from a housing of a plurality of housings (24a-24f) of the drawer (40), the method comprising- detecting the presence of one or more cell trays (35) arranged at respective housings (24a-24e) other than a first housing (24f) and electrically connected to respective power devices (20), wherein the groups of cells (30) are executing respective formation cycles;- detecting the presence of a new tray (35a) inside the first housing (24f) operatively connected to a respective power device (20);- determining the initial execution time of the formation cycle of the group of cells of the new tray (35a) as a function of the formation cycles being executed in the other cell trays (35).

8. Apparatus (10) for the formation of a plurality of groups of electrochemical cells (30) for batteries comprising a plurality of bidirectional transmission power devices (20), wherein each power device (20) is configured to electrically couple to a respective group of cells of a plurality of groups of electrochemical cells (30) and to apply to the group of electrochemical cells (30) a variable voltage or current, and an electronic controller (50) connected to the plurality of power devices (20) and programmed to cause each power device to execute a respective formation cycle (42a-42f) on a respective group of cells of the plurality of groups of cells (30),wherein each formation cycle (42a-42f) comprises a plurality of charging steps (43), a plurality of discharging steps (44) and a plurality of pause steps (45), wherein any one charging step (43) has a non-zero current intensity and a first duration time, any one discharging step (44) has a non-zero current intensity of opposite direction with respect to the charging step (43) and a second duration time and any one pause step (45) is at zero current and has a third duration time; wherein the initial execution times of the respective formation cycles are temporally offset with respect to each other, or or in combination wherein the third duration time of at least one pause step (45) of at least one formation cycle (42a- 42f) is temporally lengthened.

9. Apparatus (10) according to claim 8, wherein the power devices of the plurality of power devices (20) are electrically coupled to each other in parallel and are configured to exchange direct current power with one another.

10. Apparatus (10) according to claim 8 or 9, wherein the power devices (20) are DC / DC converter devices, wherein a direct current input at a second voltage is converted to a direct current output at a third voltage directly applicable to electrochemical cells to operate a formation cycle.

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