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 capacity from an electrochemical energy storage device, corresponding device and computer program technical field

[0001] This disclosure relates to the field of energy storage in electrochemical devices such as batteries. More specifically, this disclosure concerns extending the lifespan of such energy storage devices.

[0002] It finds applications for all devices and systems in which such electrochemical energy storage devices are found, 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 battery cycling 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). Previous technique

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

[0005] More specifically, taking the example of the lithium ion, its small size allows it to reversibly intercalate into host materials such as those with a lamellar structure (e.g., graphite or LiMO2, where M is chosen from Mn, Co, and Ni), a spinel structure (e.g., LiMn2O4), or an olivine structure (LiFePO4), filling vacant interstitial sites while preserving their structure. The intercalation of the Li+ ion, followed by its extraction, constitutes a reversible "breathing motion" of the structure. Thus, in the case of a lithium-ion battery during charging, Li+ ions are released from the cathode (deintercalation or disinsertion reaction) and insert themselves at the anode (intercalation or insertion reaction). During discharge, the reaction Opposite reactions occur at the cathode (intercalation) and at the anode (disintercalation). Such a reaction in the ionic state ensures its reversibility and the proper functioning of the rechargeable electrochemical device.

[0006] Certain irreversible side reactions, for example due to electrolyte consumption or localized deposit of metallic lithium on the anode, may nevertheless occur and lead to a decrease in the battery's recharge capacity. Degradation, and therefore the loss of capacity of electrochemical storage systems, is generally slow and linear up to 70-80% of the state of health (SOH) (capacity loss of 20 to 30%).

[0007] Under certain operating conditions, this capacity loss is sometimes accelerated by the appearance of inhomogeneities within the electrochemical cell. This is particularly the case for systems operating within narrow SOC ranges (typically a 40-60% SOC range), especially if they are composed of Li-ion LFP / Graphite cells (where LFP stands for Lithium Iron Phosphate, or LiFePO4). This includes energy storage systems used for load frequency control (LFC) of electrical grids, which must be able to switch rapidly between charging and discharging, with timescales of 30 seconds to 30 minutes at relatively high rates (e.g., 2C). Consequently, the resulting operating SOC range is relatively narrow due to the rapid polarity reversal.

[0008] Indeed, when the cell remains constantly at an average charge level close to 50%, the cathode potential curve in LFP is almost flat, with two phases coexisting for a large part of the charging or discharging process. Therefore, no potential difference forces the homogenization of lithium ions on the electrode surface. The appearance of local inhomogeneity will thus increase over time and lead to the creation of areas rich and poor in Li+ ions. These inhomogeneities will then significantly accelerate the loss of capacity of the device (capacity based on areas with lower Li+ ion concentrations).

[0009] A similar phenomenon is also observed for electrochemical cells cycling at high current (typically a C-rate greater than IC). Indeed, since not all ions have time to move from one electrode to the other, the appearance of a slight inhomogeneity also increases over the course of 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 re-homogenize 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 re-homogenize, or by carrying out complete charge / discharge cycles which makes 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 re-homogenizing the distribution of lithium ions, have notably been studied by Kobayashi et al. in the article "Unexpected capacityfade 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 for greater capacity recovery, is based on cycling through the full SOC range (0%-100%), over a series of 450 cycles, with 30-minute breaks between successive cycles, for a period of 40 days. This series of total charges and discharges ("full SOC"), designed to homogenize ion diffusion within the cell, resulted in the highest capacity recovery achieved, namely 20% for a 40-day protocol.

[0016] While these results are promising, the protocols studied all have the drawback of requiring prolonged downtime of the electrochemical storage devices. Thus, while the observed capacity recovery is interesting in that it increases the lifespan of the storage devices, their unavailability over a wide time period results in 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 disadvantages of the prior art, and which improves the situation. Summary

[0018] The present disclosure addresses this need by proposing a method for recovering capacity from an electrochemical energy storage device, comprising alternating steps of: - fully charge the device to a maximum charging voltage; - relaxation of the device for a relaxation period, TREL; The alternation is 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 lifespan of rechargeable batteries, which makes it possible to obtain a capacity boost in the storage system, and therefore an increase in its lifespan, with a reduced downtime (T1ND) compared to prior art solutions. To achieve this, such a process advantageously relies on alternating periods of full charging and battery relaxation, the parameters of which are optimized to achieve a satisfactory compromise between capacity gain and downtime of the electrochemical storage device. Under experimental conditions, a capacity gain of 15% was thus achieved in a reduced time of only eight days.

[0020] Unlike prior art solutions, such a capacity recovery process advantageously exploits the combined effect of pause and full charging up to a 100% state of charge (SOC), and eliminates the need for a long discharge phase and long charging times (the battery remains essentially in a charged state during the relaxation period). This significantly reduces the downtime of the electrochemical energy storage device for its operator. Indeed, relaxation eliminates the concentration gradients generated by the current flow and induces only a slight decrease in cell voltage, mainly due to diffusion.

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

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

[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 process is implemented when the capacity of said electrochemical device decreases by a value exceeding a predetermined threshold. For example, such a predetermined threshold corresponds to a capacity loss of the electrochemical device greater than or equal to 5%, preferably greater than or equal to 10%.

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

[0028] Alternatively, or in addition, such a capacity recovery process 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 process is implemented during a period of scheduled maintenance of the electrochemical device.

[0030] This advantageously reduces the downtime of the electrochemical device. Furthermore, during such maintenance periods, the device operator generally performs a complete cycle, after which they measure the residual capacity of the electrochemical device. By comparing this to the nominal capacity of the cell, they deduce the value of the cell's capacity loss and can then decide, based on this loss, whether or not to initiate a capacity recovery process for the electrochemical device.

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

[0032] Indeed, these storage systems are particularly prone to the appearance of reversible inhomogeneities in ion circulation within the cell, and are therefore particularly suited to capacity recovery according to the capacity recovery process that is the subject of this disclosure. A rapid loss of capacity is generally observed for these storage systems after a certain number of cycles, and therefore a certain duration of operation under these shallow depth of discharge (or DOD) conditions. ratio expressed as a percentage between the capacity already discharged 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 LiFePO4 cathode. The experimental results obtained for such an electrochemical device have indeed been particularly interesting in terms of capacity recovery. The process of the present disclosure, however, applies to all battery technologies.

[0034] The features described in the preceding paragraphs may optionally be implemented independently of each other or in combination with each other.

[0035] This disclosure also relates to a capacity recovery device of an electrochemical energy storage device, comprising at least one processing circuit connected to the electrochemical device for implementing the process as described above.

[0036] This disclosure further relates to a computer program comprising instructions for the implementation of all or part of a process as defined herein when this program is executed by a processing circuit.

[0037] It also relates to a non-transient, computer-readable recording medium on which such a program is recorded. Such a recording medium can be any entity or device capable of storing the program. For example, the medium may include 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 flash drive or a hard drive.

[0038] On the other hand, such a recording medium can be a transmissible medium such as an electrical or optical signal, which can be transmitted via an electrical or optical cable, by radio, or by other means, so that the computer program it contains is executable remotely. The program according to the invention can, in particular, be uploaded to 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 process.

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

[0041] Other features, details and advantages will become apparent from reading the detailed description below, and from analyzing the accompanying drawings, on which: Fig. 1

[0042] [Fig.1] illustrates a pattern of alternating periods of charging and relaxing an electrochemical energy storage device according to an embodiment of a process for recovering the capacity of this device. Fig. 2

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

[0044] [Fig.3] presents in schematic form the structure of a recovery device capacity according to a mode of embodiment. Description of the implementation methods

[0045] The general principle of this disclosure is based on alternating full charge (maximum voltage indicated in the device's datasheet) and relaxation (pause) cycles applied to an electrochemical energy storage device. This cycle allows for a capacity recovery of the storage device and thus an increase in its lifespan with reduced downtime. This method is to be applied throughout the battery's life to limit its degradation, and is optimized to maximize capacity recovery while minimizing device downtime.

[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 reversible capacity loss, and on which the capacity recovery process 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 battery's capacity decreases over time. Part of this capacity loss is irreversible and linked to the aging of its components induced by certain parasitic reactions or various degradation mechanisms. Another part of this capacity loss, on the contrary, is reversible, as 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 on reduced SOC ranges, between 40% and 60% for example.

[0049] This is typically the case for stationary storage systems, used for example as a complement to renewable electricity generation sources, which are configured to maintain the frequency of the electrical grid 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 should be noted that the discharge rate or C-rate, expressed as a multiple of C, corresponds to the ratio of the applied current i (i.e., the discharge rate) to the battery capacity C: C-rate =-^

[0051] The capacity recovery protocol proposed in one embodiment makes it possible to eliminate these inhomogeneities and thus restore capacity to the storage device or system. It can be applied at regular intervals (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 alternating charging and relaxation periods according to one embodiment. The curve in [Fig. 1] represents the voltage across the battery terminals, expressed in Volts (V), as a function of time t.

[0053] According to one embodiment, the capacity recovery process for an electrochemical energy storage device consists of alternating periods of full charging Sl(CCyc) at the charging current CCyc, allowing the battery to reach a state of charge SOC=100%, and periods of rest or relaxation S2(TREL), during which the battery is left at rest for a relaxation time TREL. This alternation of charging Sl(CCyc) and relaxation S2(TREL) stages is repeated for a time T1ND, which corresponds to a period of battery unavailability for effective operation.

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

[0055] Depending on the initial state of charge of the battery, the first full charge period Sl(CCyc) may be longer than subsequent charging stages. This is because, during the relaxation periods S2, the battery is left at rest without being subjected to any charging or discharging: the voltage across its terminals therefore decreases only slightly. The return to a full state of charge SOC=100% during the following Sl(CCyc) charging period is thus faster than during the first full charge period.

[0056] The charge / relaxation alternation pattern illustrated in [Fig. 1] was applied experimentally to a 200 Ah class prismatic LFP / 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 profile. Such a cell therefore generally operates within a SOC range of between 40% and 60%, which causes inhomogeneities to appear within the cell.

[0057] The capacity recovery protocol illustrated in [Fig.1] 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"). It is worth noting that a cycle refers to the set of one discharge period and one charge period of the battery.

[0058] The table below presents 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 of 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 discharged capacity 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 just 8 days, to achieve a capacity recovery of more than 15%.

[0061] Such a capacity recovery protocol is therefore particularly optimized, in that, compared with prior art methods, the downtime T1ND (i.e., the lost time, and therefore the financial loss for the system manager) is significantly reduced. storage) is minimal, while the capacity gain is significant.

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

[0063] For the cell model considered, it is therefore possible to reduce the relaxation time Trel from Ih 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 about 4 days.

[0064] Similarly, for the cell used in the construction of Table 1, doubling the cycling current CCyc makes it possible to approximately halve the cell downtime T1ND. Conversely, the charging current CCyc during the SI charging step could be reduced to C / 3, which would increase capacity recovery but would also increase the cell downtime T^d. For the particular cell model used in this embodiment, a charging current of C / 2 was therefore found to be optimal, as it allowed for significant capacity recovery within a downtime acceptable to the operator, and thus constituted a good compromise.

[0065] It is also possible to play with the frequency of application of this recovery protocol during the life of a battery.

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

[0067] In an advantageous embodiment, the capacity recovery protocol can be applied after 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 following 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 case 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 capacity loss relative 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 El, this measured capacity C is compared to a capacity threshold CTH below which the operator does not wish to go (alternatively, the capacity loss 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 an INIT S0 step. Depending on the type of battery, and the type of use to which it is put, the operator 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 the operator can agree.

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

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

[0076] At the end of each S1+S2 phase alternation, a check is performed during step S3 to determine whether the maximum unavailability period set by the operator has been reached. If not, the alternation of the full charge phase S1 and the relaxation phase S2 continues. If so, the capacity recovery protocol is complete, and the battery can be put back into service by the operator (step S4 FIN_IND).

[0077] Optionally, the operator may, 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 should be noted that steps E0 and El are optional (dashed lines). Indeed, the operator may choose to implement the capacity recovery protocol at regular time intervals, for example once a year, regardless of any potential battery capacity loss.

[0079] Figure 3 schematically illustrates the structure of a DIS (Dispositif d'Insertion) device for capacity recovery from an electrochemical energy storage device BATT. Such a DIS device includes a processing circuit connected to the electrochemical device BATT for implementing the capacity recovery process described above.

[0080] With reference to [Fig. 3], this processing circuit may include: - 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 for a computer program to implement the above process. The MEM memory can be of the ROM (Read Only Memory) or RAM (Random Access Memory) type, or even Flash. - a PROC processor capable of cooperating with the MEM memory and, in particular, of reading the instructions stored in memory to execute the steps necessary for implementing the process defined above. Thus, the PROC processor can calculate the battery's state of charge (SOC) or control the measurement of capacity (C). And - an output interface OUT cooperating with the processor PROC to possibly deliver the result of a capacity measurement C of the battery, intended to be displayed on a human / machine interface (display on a screen or broadcasting of an audio signal), and to send CMD commands to execute the alternation of the full charge phase SI and relaxation phase S2 of the battery BATT.

[0081] Figure 3 illustrates only one particular way, among several possible ways, of implementing a capacity recovery device for an electrochemical energy storage device, so that it performs the steps of the process detailed above, in relation to Figures 1 and 2 (in any one of the different embodiments, or in a combination thereof). Indeed, these steps can be performed interchangeably on a reprogrammable computing machine (a PC, a DSP processor, or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example, an array 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 that may experience a rapid, reversible loss of capacity. This is particularly relevant for energy companies operating storage systems for frequency regulation or for storing power generated from intermittent energy sources. The procedure can be carried out during scheduled maintenance periods for the devices.

[0083] This protocol may also be useful to any battery user subjected to rapid charging.

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

[0085] For the sake of clarity, 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

Demands

1. A method for recovering the capacity of an electrochemical energy storage device, comprising alternating steps of: a. full charging (S1) of said device to a maximum charging voltage (Umax); b. relaxation (S2) of said device for a relaxation time, TreL; said alternation being repeated for 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 capacity recovery method 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 capacity recovery method 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. A 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. Capacity recovery method according to any one of the claims indications 1 to 6, characterized in that it is implemented during a period of scheduled maintenance 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 perform frequency regulation of an electrical distribution network.

9. A 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 LiFePO4 cathode.

11. Capacity recovery device of an electrochemical energy storage device, comprising at least one processing circuit connected to the electrochemical device for implementing the process according to one of the preceding claims.

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