Method for recovering capacity from an electrochemical energy storage device, including the corresponding device and computer program.

Abstract

A method for recovering the capacity of an electrochemical energy storage device comprises alternating steps of: full charging (S1) of the device to a maximum charging voltage (Umax); relaxation (S2) of the device for a relaxation time, TREL; the alternation being repeated for an unavailability time, TIND, of the electrochemical device and carried out at a cycling current, CCyc, less than or equal to the maximum current supported by the electrochemical device during normal operation. Abstract figure: Figure 1

Description

Title of the invention: Method for recovering the capacity of an electrochemical energy storage device, corresponding device and computer program Technical field

[0001] The present disclosure relates to the field of energy storage in electrochemical devices of the battery type in particular. More specifically, the present disclosure relates to extending the lifetime of such energy storage devices.

[0002] It finds applications for all devices and systems in which such electrochemical energy storage devices are located, such as rechargeable batteries, and in particular, for example, a lithium-ion battery, a solid-state lithium battery, a sodium-ion battery, a solid-state sodium battery, etc.

[0003] The present disclosure aims in particular to increase the lifespan of such storage systems, in particular systems requiring the cycling of batteries over a reduced state of charge (or SOC) range (this is the case, for example, of storage systems used to operate frequency regulation on an electrical network), or at high current (this is the case, for example, of storage systems requiring rapid charging). Prior art

[0004] The operation of a rechargeable electrochemical energy storage device is based on a set of reversible electrochemical reactions at the cathode (positive electrode) and the anode (negative electrode). To achieve high reversibility during the battery charge / discharge cycles, a so-called "intercalation" reaction is used, which allows the target ions (e.g., Li+ or Na+ ions) to move in the "ionic" state between the cathode and the anode during operation of the device, with a low rate of parasitic reaction.

[0005] More specifically, taking the example of the lithium ion, its small size allows it to be reversibly intercalated in host materials such as those with a lamellar structure (for example, graphite or LiMO2, where M is chosen from Mn, Co and Ni), with a spinel structure (for example LiMn2O4) or with an olivine structure (LiFePO4), by filling the vacant interstitial sites, while preserving their structure. The intercalation of the Li+ ion, then its extraction, forms a reversible “breathing movement” of the structure. Thus, in the case of a lithium-ion battery under charge, the Li+ ions are released from the cathode (deintercalation or deinsertion reaction) and are inserted at the anode (intercalation or insertion reaction). During discharge, the reaction opposite occurs at the cathode (intercalation) and at the anode (deintercalation). Such a reaction in the ion state ensures its reversibility and the proper functioning of the rechargeable electrochemical device.

[0006] Certain irreversible parasitic reactions, for example due to the consumption of electrolyte or to a localized deposit of metallic lithium on the anode, can nevertheless occur, and lead to a reduction in the recharging capacity of the battery. The degradation, and therefore the loss of capacity of electrochemical storage systems, is generally slow and linear up to 80-70% of the state of health (or SOH for the English "State Of Health") (capacity loss of 20 to 30%).

[0007] Under certain operating conditions, this loss of capacity is sometimes accelerated by the appearance of inhomogeneities within the electrochemical cell. This is particularly the case for systems operating over reduced SOC ranges (typically a SOC range of 40-60%) and in particular if they are composed of LFP / Graphite Li-ion cells (where LFP denotes Lithium Iron Phosphate, or LiFePO4). These include storage systems used for the frequency regulation of electrical networks (or LFC, for "Load Frequency Control"), which must be able to operate rapid switching between charging and discharging, with time scales of 30 seconds to 30 minutes at relatively high rates (for example, 2C). Consequently, the resulting operational SOC range is relatively narrow due to the rapid reversal of polarity.

[0008] Indeed, when the cell remains permanently at an average state of charge close to 50%, the potential curve of the LFP cathode is almost flat, with two phases coexisting for a large part of the charge or discharge. No potential difference therefore forces the homogenization of the lithium ions at the surface of the electrode. The appearance of local inhomogeneity will therefore increase over time and lead to the creation of areas rich and areas poor in Li+ ions. These inhomogeneities will then greatly accelerate the loss of capacity of the device (capacity based on the areas weaker in Li+ ions).

[0009] A similar phenomenon is also observed for electrochemical cells cycling at high current (typically a C-rate higher than IC). Indeed, since not all the ions have time to move from one electrode to another, the appearance of a slight inhomogeneity also increases over the cycles.

[0010] However, it has been observed that these inhomogeneities are reversible.

[0011] It has thus been observed in particular that it is possible to rehomogenize the distribution of lithium ions by placing the electrochemical cell at rest with a significant pause time (of several months for example), which allows time for the lithium ions to rehomogenize, or by carrying out complete charge / discharge cycles which make it possible to alternately empty each electrode of all its ions and to "reset" the distribution of ions, or even with the realization of low current cycles for a high current cycling device.

[0012] These mechanisms of appearance of inhomogeneities within the electrochemical cell, and of recovery of cell capacity by rehomogenizing the distribution of lithium ions, have notably been studied by Kobayashi et al. in the article “Unexpected capacity fade and recovery mechanism of LiFePO4 / graphite cells for grid operation”, Journal of Power Sources, 449, 227502 (2020).

[0013] In this article, Kobayashi et al. study more particularly two protocols allowing capacity recovery for batteries in which such inhomogeneities have appeared due to non-uniform ionic conduction of Lithium ions between the anode and the cathode.

[0014] A first protocol consists of placing the battery at complete rest, in a state of charge of 20%, for a long period of approximately 40 days.

[0015] A second protocol, allowing a greater capacity recovery, is based on cycling in the full SOC range (0%-100%), over a succession of 450 cycles, with a 30-minute break between successive cycles, for a period of 40 days. This succession of total charges and discharges ("full SOC"), aimed at homogenizing the diffusion of ions in the cell, allowed the greatest capacity recovery obtained, namely 20% for a 40-day protocol.

[0016] While these results are promising, the protocols studied all have the disadvantage of requiring long-term immobilization of the electrochemical storage devices. Thus, while the observed capacity recovery is interesting in that it increases the lifetime of the storage devices, their unavailability over a wide time range causes a significant financial loss for the operators of such storage devices.

[0017] There is therefore a need for a capacity recovery technique for electrochemical energy storage devices which does not have these drawbacks of the prior art, and which improves the situation. Summary

[0018] The present disclosure meets this need by proposing a method for recovering the capacity of an electrochemical energy storage device, comprising an alternation of steps of: - fully charge the device to a maximum charging voltage; - relaxation of the device during a relaxation time, TREL; the alternation being repeated during a period of unavailability, T1ND, of the electrochemical device and carried out at a cycling current, CCyc, less than or equal to the maximum current supported by the electrochemical device. Such a maximum current corresponds for example to the current indicated by the manufacturer of the electrochemical device in its technical data sheet.

[0019] Thus, the present disclosure is based on a completely new and inventive approach to extending the lifetime of rechargeable batteries, which makes it possible to obtain a boost in the capacity of the storage system, and therefore an increase in its lifetime, for a reduced downtime T1ND compared to the solutions of the prior art. To do this, such a method advantageously relies on alternating periods of full charging and relaxation of the battery, the parameters of which are optimized to achieve a satisfactory compromise between capacity gain and downtime of the electrochemical storage device. Under the experimental conditions, a capacity gain of 15% was thus achieved in a reduced time of only eight days.

[0020] Unlike the solutions of the prior art, such a capacity recovery method advantageously exploits the combined effect of the pause and the complete charge up to a SOC of 100%, and makes it possible to avoid the long discharge phase and the long charging times (the battery in fact remains substantially in a charged state during the relaxation period), which makes it possible to considerably reduce the unavailability time (TIXI) of the electrochemical energy storage device for its operator. Indeed, relaxation makes it possible to eliminate the concentration gradients generated by the passage of the current and only induces a slight reduction in the cell voltage, in particular linked to diffusion.

[0021] According to one aspect, such a capacity recovery method comprises a choice of the relaxation time TREL and the cycling current CCyc as a function of a maximum unavailability time desired by a manager of the electrochemical device.

[0022] Indeed, by varying the charging current and the relaxation time, it is possible to vary the unavailability time for a given target capacity recovery. Thus, by reducing for example the relaxation time TreL from 1h to 30 minutes, the efficiency of the capacity recovery is slightly reduced, but the unavailability time T1ND of the electrochemical device is also considerably reduced, since the capacity recovery protocol can be carried out in only 100 hours, or approximately 4 days, instead of 200 hours (or approximately 8 days).

[0023] Indeed, according to one aspect, for an electrochemical device whose maximum possible current indicated by the manufacturer is equal to IC, the cycling current CCyc during the alternation is equal to C / 2, the relaxation time TreL is equal to one hour and the unavailability time T1ND corresponds to the duration of fifty complete equivalent cycles, FEC, of ​​the electrochemical device.

[0024] Such a duration, equivalent to 50 FEC, corresponds to approximately 200 hours, or 8 days. The results obtained show a high efficiency of the protocol based on these parameters, with a capacity gain of 15%.

[0025] More generally, according to one aspect, for an electrochemical device whose maximum possible current indicated by the manufacturer is equal to IC, the cycling current CCyc during the alternation is preferably between C / 2 and C / 4.

[0026] According to another aspect, such a capacity recovery method is implemented when the capacity of said electrochemical device decreases by a value greater than a determined threshold. For example, such a determined threshold corresponds to a loss of capacity of the electrochemical device greater than or equal to 5%, preferably greater than or equal to 10%.

[0027] Thus, such a capacity recovery method can advantageously be applied at a regular frequency during the lifetime of the electrochemical storage device, for example each time it has lost 10% of its capacity. By varying the frequency of implementation of such a capacity recovery method, it is also possible to adjust the duration of unavailability of the electrochemical device.

[0028] Alternatively, or in addition, such a capacity recovery method is implemented at regular time intervals during the lifetime of the storage device, regardless of the measured capacity of the device.

[0029] According to another aspect, such a capacity recovery method is implemented during a scheduled maintenance period of the electrochemical device.

[0030] This advantageously reduces the period of immobilization of the electrochemical device. In addition, during such maintenance periods, the operator of the device generally carries out a complete cycling, at the end of which he measures the residual capacity of the electrochemical device. By comparison with the nominal capacity of the cell, he deduces the value of the capacity loss of the cell, and can then decide, depending on this loss, whether or not to launch a capacity recovery process for this electrochemical device.

[0031] According to another aspect, such an electrochemical device is integrated into a stationary storage system, for example configured to carry out frequency regulation of an electrical distribution network, or in a storage system configured to cycle at a high C-rate, preferably greater than IC.

[0032] Indeed, these storage systems are particularly subject to the appearance of reversible inhomogeneities in the circulation of ions within the cell, and therefore particularly suitable for capacity recovery according to the capacity recovery method which is the subject of the present disclosure. A rapid loss of capacity is indeed generally observed for these storage systems after a certain number of cycles, therefore a certain duration of operation in these conditions of low depth of discharge (or DOD, for the English "Depth Of Discharge" which is the ratio expressed as a percentage between the already discharged capacity and the nominal capacity of the battery) or high current.

[0033] According to yet another aspect, the electrochemical device is a lithium-ion battery comprising a graphite anode and a cathode composed of LiFePO4. The experimental results obtained for such an electrochemical device have indeed been particularly interesting in terms of capacity recovery. The method of the present disclosure, however, applies to all battery technologies.

[0034] The characteristics set out in the paragraphs above may, optionally, be implemented independently of one another or in combination with one another.

[0035] The present disclosure also relates to a device for recovering the capacity of an electrochemical energy storage device, comprising at least one processing circuit connected to the electrochemical device for implementing the method as described previously.

[0036] The present disclosure also relates to a computer program comprising instructions for implementing all or part of a method as defined herein when this program is executed by a processing circuit.

[0037] It also relates to a non-transitory recording medium, readable by a computer, on which such a program is recorded. Such a recording medium may be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a USB key or a hard disk.

[0038] On the other hand, such a recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means, so that the computer program it contains is remotely executable. The program according to the invention may in particular be downloaded over a network, for example the Internet.

[0039] Alternatively, the recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the aforementioned capacity recovery method.

[0040] The aforementioned capacity recovery device, computer program and recording medium have at least the same characteristics and advantages as the capacity recovery method described above. Brief description of the drawings

[0041] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0042] [Fig.l] illustrates a pattern of alternating charging and relaxation periods of an electrochemical energy storage device according to an embodiment of a method for recovering the capacity of this device. Fig. 2

[0043] [Fig.2] presents in the form of a flowchart the different stages of the re process capacity recovery according to one embodiment. Fig. 3

[0044] [Fig.3] shows in schematic form the structure of a recovery device of capacity according to one embodiment. Description of the embodiments

[0045] The general principle of the present disclosure is based on a full charge (maximum voltage indicated in the technical data sheet of the device) / relaxation (pause) alternation applied to an electrochemical energy storage device, which makes it possible to obtain a capacity recovery of the storage device and therefore an increase in its lifetime for a reduced unavailability time. This is a method to be applied during the life of the battery to limit its degradation, this method being optimized to maximize capacity recovery while limiting the unavailability time of the device.

[0046] In the following, the terms battery, cell, electrochemical energy storage device or electrochemical device will be used interchangeably to designate a rechargeable device subject to a reversible loss of capacity, and to which the capacity recovery method presented here can advantageously be applied.

[0047] During its operation, also called cycling in reference to the succession of total or partial charge and discharge cycles of the battery, the capacity of the battery decreases over time. A part of this loss of capacity is irreversible, and linked to the aging of its components induced by certain parasitic reactions or to various degradation mechanisms. Another part of this loss of capacity is on the contrary reversible, because it results from the appearance of inhomogeneities within the electrodes of the electrochemical cell.

[0048] This reversible portion of capacity loss is particularly observable for rechargeable batteries composed of LFP on the cathode side, and it increases for energy storage systems operating over reduced SOC ranges, between 40% and 60% for example.

[0049] This is typically the case for stationary storage systems, used for example to complement renewable sources of electrical energy production, which are configured to maintain the power grid frequency within an acceptable operating range. Such systems are also called frequency regulation systems.

[0050] This is also the case for cycling storage systems with a high C-rate, or high charging current, greater than IC for example. It is recalled that the (dis)charge rate or C-rate, expressed as a multiple of C, corresponds to the ratio of the current i applied (i.e. the (dis)charge rate) to the capacity C of the battery: C-rate =-^

[0051] The capacity recovery protocol proposed according to one embodiment makes it possible to erase these inhomogeneities and thus provide a capacity boost to the storage device or system. It can be applied at a regular frequency (for example each time the system loses 10% of its capacity or at each scheduled maintenance) during its lifetime.

[0052] Reference is now made to [Fig. 1] which shows the general pattern of alternation of the charging and relaxation periods according to one embodiment. The curve of [Fig.l] represents the voltage at the terminals of the battery, expressed in Volts (V), as a function of time t.

[0053] According to one embodiment, the method for recovering the capacity of an electrochemical energy storage device consists of carrying out an alternation of periods of complete charging Sl(CCyc) at the charging current CCyc, making it possible to reach a state of charge of the battery SOC=100%, and periods of pause or relaxation S2(TREL), during which the battery is left at rest for a relaxation time TREL. This alternation of charging steps Sl(CCyc) and relaxation S2(TREL) is repeated for a time T1ND, which corresponds to a period of unavailability of the battery for effective operation.

[0054] Charging SI(CCyc) ends when the voltage across the storage device reaches a value Umax corresponding to the maximum operating voltage of the device, which reflects a full state of charge SOC=100%.

[0055] Depending on the initial state of charge of the battery, the first full charge period Sl(CCyc) may be longer than the following charge steps. Indeed, during the relaxation periods S2, the battery is left at rest without imposing any charge or discharge on it: the voltage at its terminals therefore decreases only slightly. The return to a full state of charge SOC=100% during the following charge period Sl(CCyc) is therefore faster than during the first full charge period.

[0056] The charge / relaxation alternation pattern illustrated in [Fig.l] was applied experimentally to a 200 Ah class LFP / Prismatic Graphite cell (nominal battery capacity) whose maximum current given by the manufacturer is equal to IC, and having cycled at room temperature according to a frequency regulation type profile. Such a cell therefore generally operates in a SOC range between 40% and 60%, which causes the appearance of inhomogeneities within the cell.

[0057] The capacity recovery protocol illustrated in [Fig.l] was applied to it, at room temperature, with the following parameters: ■ TREL=lh ; - CCyc=C / 2 ; - T1ND=200h, or approximately 8 days, which corresponds to the duration of 50 complete cycles (or 50 FEC for "Full Equivalent Cycles"). Remember that a cycle refers to the set consisting of a discharge period and a charge period of the battery.

[0058] The table below shows the results obtained in terms of capacity recovery for this cell after application of such a protocol. These performances are measured by carrying out a charge and discharge cycle of the battery, before and after application of the capacity recovery protocol, with a charge / discharge current at C / 5.

[0059] [Tables 1] C / 5 Discharged capacity (in Ah) Discharged energy (in Wh) Before protocol 78.52 236.8 After protocol 92.85 283.1 Gain (in %) 18.25 19.55

[0060] As can be seen from Table 1, the gain obtained at the end of the charge / discharge cycle between the capacity discharged before application of the capacity recovery protocol and after application of the protocol amounts to 18.25%. In this embodiment, the capacity recovery protocol therefore makes it possible, in only 8 days, to achieve a capacity recovery greater than 15%.

[0061] Such a capacity recovery protocol is therefore particularly optimized, in that, in comparison with the methods of the prior art, the duration of unavailability T 1ND (i.e. the time lost, and therefore the financial loss for the manager of the system of storage) is minimal, while the capacity recovery is significant.

[0062] Depending on the use case, the parameters (cycling current, pause time, temperature, etc.) can be adapted according to the type of cell (energy vs. power) or load (frequency adjustment, peak shaving, etc.). It is also possible to vary the downtime by varying the charging current, relaxation time, duration and frequency of the proposed method.

[0063] For the cell model considered, it is thus possible to reduce the relaxation time Trel from 1 h to 30 min, which will slightly reduce the efficiency of the capacity recovery but will allow the protocol to be carried out in only 100 hours, or approximately 4 days.

[0064] Similarly, for the cell used for the construction of Table 1, by multiplying the cycling current CCyc by two, it is possible to approximately halve the unavailability time T1ND of the cell. Conversely, the charging current CCyc during the charging step SI could be reduced to C / 3, which would increase the capacity recovery, but would increase the unavailability time T^d of the cell. For the particular cell model used in this embodiment, it therefore appeared that a charging current of C / 2 was optimal, in that it allowed a significant capacity recovery in an unavailability time acceptable to the operator, and therefore constituted an interesting compromise.

[0065] It is also possible to vary the frequency of application of this recovery protocol over the lifetime of a battery.

[0066] For stationary applications (network service type), the operator generally carries out a performance check of its stationary storage systems once a year ("check-up"), during which it measures the capacity of these storage systems, and can therefore assess the loss of capacity compared to the nominal capacity of the system.

[0067] In an advantageous embodiment, the capacity recovery protocol can be applied at the end of this check-up: depending on the evolution of the capacity measured at each check-up, this could be for example twice a year, once a year or once every two years...

[0068] For example, the capacity recovery protocol can be applied at the end of this check-up if the operator measures a capacity loss greater than 10%.

[0069] A flowchart of the steps implemented by the operator in such a scenario is presented below in relation to [Fig.2].

[0070] During a step referenced E0, the operator of the stationary storage system evaluates the capacity C of a battery, and the loss of capacity compared to the nominal capacity. This measurement MES(C) is for example carried out at the end of a phase of battery check-up, as part of a scheduled maintenance operation.

[0071] During a step referenced E1, this measured capacity C is compared to a capacity threshold CTH below which the operator does not wish to fall (as a variant, the loss of capacity relative to the nominal capacity is expressed as a percentage, and this percentage is compared to a maximum loss tolerated by the operator, or to a threshold loss beyond which it seems necessary to implement a capacity recovery protocol for this battery).

[0072] If the measured capacity C is greater than the capacity threshold CTH, the battery can be put back into service, and its maintenance and unavailability phase ends (step S4).

[0073] On the other hand, if the capacity loss is for example greater than 5 or 10%, the operator can choose to launch the capacity recovery protocol, which is initialized during a step INIT S0. Depending on the type of battery, and the type of use he makes of it, he chooses the appropriate parameters of this capacity recovery protocol, in particular the value of the cycling current CCyc and the duration of the relaxation time TREL, so that they are compatible with the maximum unavailability time T1ND of the battery to which he can consent.

[0074] The battery then undergoes a charging phase SI at a charging current CCyc, until reaching a state of charge SOC=100%.

[0075] It is then left to rest S2 for a relaxation time TREL.

[0076] At the end of each alternation of phases S1+S2, it is checked during a step S3 whether the maximum duration of unavailability set by the operator has been reached. If not, the alternation of the full charge phases SI and relaxation S2 continues. If so, the capacity recovery protocol is terminated, and the battery can be put back into service by the operator (step S4 FIN_IND).

[0077] Optionally, the operator can, before putting the battery back into service, carry out a new measurement of its capacity (step E0 MES(C)), to verify the effectiveness of the capacity recovery protocol that he has just applied.

[0078] Similarly, it will be noted that steps E0 and E1 are optional (dotted lines). Indeed, the operator can choose to implement the capacity recovery protocol at regular time intervals, for example once a year, regardless of the possible loss of capacity of the battery.

[0079] [Fig. 3] schematically illustrates the structure of a DIS device for recovering the capacity of an electrochemical energy storage device B ATT. Such a DIS device comprises a processing circuit connected to the electrochemical device BATT for implementing the capacity recovery method presented above.

[0080] With reference to [Fig.3], this processing circuit may comprise: - an input interface IN for signals from the electrochemical device BATT, during its charging or discharging, these signals including the voltage V (in volts) at terminals of the electrochemical device BATT and the charge / discharge Q (in ampere-hours), - a MEM memory capable of storing at least temporarily voltage and charge / discharge values, as well as instruction data of a computer program for implementing the above method. The MEM memory can be of the ROM (Read Only Memory) or RAM (Random Access Memory) type or even Flash, - a processor PROC capable of cooperating with the memory MEM and in particular of reading the instructions stored in the memory to execute in particular the steps necessary for the implementation of the method defined above. Thus, the processor PROC can calculate a state of charge SOC of the battery, or control the measurement of the capacity C. And - an output interface OUT cooperating with the processor PROC to possibly deliver the result of a measurement of the capacity C of the battery, intended to be restored on a human / machine interface (display on a screen or broadcasting of an audio signal), and to send commands CMD for executing the alternation of the complete charge phases SI and relaxation S2 of the battery BATT.

[0081] [Fig. 3] illustrates only one particular way, among several possible ways, of producing a capacity recovery device of an electrochemical energy storage device, so that it carries out the steps of the method detailed above, in relation to Figures 1 and 2 (in any one of the different embodiments, or in a combination of these embodiments). Indeed, these steps can be carried out indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module).

[0082] The battery capacity recovery protocol described above can be used by all managers of electrochemical storage systems likely to exhibit rapid reversible capacity loss. This is particularly the case for companies in the energy sector operating storage systems for frequency regulation or storage of production from intermittent energy. The procedure can be carried out during scheduled maintenance periods for the devices.

[0083] This protocol can also be useful to any user of a battery subject to rapid charges.

[0084] Different protocols were carried out in the laboratory with different parameter values ​​(different relaxation times, charging currents, durations unavailability...) on different types of batteries and electrochemical cells that have suffered a reversible loss of capacity. The results show that the presented procedure is particularly effective in increasing the lifetime of electrochemical storage systems. This procedure can be easily developed for industrial purposes. List of cited documents Non-patent literature

[0085] For all useful purposes, the following non-patent element is cited: - Kobayashi et al. “Unexpected capacity fade and recovery mechanism of LiFePO4 / graphite cells for grid operation”, Journal of Power Sources, 449, 227502 (2020).

Claims

Claims

1. Method for recovering the capacity of an electrochemical energy storage device, comprising an alternation of steps of: a. full charge (SI) of said device at a maximum charge voltage (Umax); b. relaxation (S2) of said device during a relaxation time, TreL; said alternation being repeated during an unavailability time, T1ND, of said electrochemical device and carried out at a cycling current, CCyc, less than or equal to the maximum current supported by said electrochemical device.

2. A capacity recovery method according to claim 1, further comprising a choice of said relaxation time TreL and said cycling current CCyc as a function of a maximum unavailability time desired by a manager of said electrochemical device.

3. A method of recovering capacity according to any one of claims 1 and 2, characterized in that, for an electrochemical device whose maximum supported current is equal to IC, said cycling current CCyc during said alternation is between C / 2 and C / 4.

4. A capacity recovery method according to any one of claims 1 to 3, characterized in that, for an electrochemical device whose maximum supported current is equal to IC, said cycling current CCyc during said alternation is equal to C / 2, said relaxation time TreL is equal to one hour and said unavailability time T1ND corresponds to the duration of fifty complete equivalent cycles, FEC, of said electrochemical device.

5. A method of recovering capacity according to any one of claims 1 to 4, characterized in that it is implemented when the capacity of said electrochemical device decreases by a value greater than a determined threshold.

6. Capacity recovery method according to claim 5, characterized in that said determined threshold corresponds to a capacity loss greater than or equal to 5% of said electrochemical device, preferably greater than or equal to 10%.

7. A method of recovering capacity according to any one of the claims- indications 1 to 6, characterized in that it is implemented during a scheduled maintenance period of said electrochemical device.

8. A capacity recovery method according to any one of claims 1 to 7, characterized in that said electrochemical device is integrated into a stationary storage system configured to carry out frequency regulation of an electrical distribution network.

9. Capacity recovery method according to any one of claims 1 to 7, characterized in that said electrochemical device is integrated into a storage system configured to cycle at a high C-rate, preferably greater than IC.

10. A capacity recovery method according to any one of claims 1 to 9, characterized in that said electrochemical device is a Lithium-ion battery comprising a graphite anode and a cathode composed of LiFePO4.

11. Device for recovering the capacity of an electrochemical energy storage device, comprising at least one processing circuit connected to the electrochemical device for implementing the method according to one of the preceding claims.

12. Computer program comprising instructions for implementing the method according to one of claims 1 to 10, when said instructions are executed by a processing circuit.

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