Battery cell precipitate removal method and precipitate removal system using same

Abstract

The present invention relates to a method for removing a precipitate from a battery cell and a precipitate removal system using same. Provided is the battery cell precipitate removal method including a capacity recovery cycle, which discharges a battery cell in a voltage range lower than that of the normal cycle of a battery and maintains the low voltage range to allow precipitates of the battery cell to return to an ionic state, and thus the precipitates of the battery cell are removed and the capacity of a battery is recovered. According to the present invention, precipitates generated in a battery cell can be easily removed by merely adjusting the voltage, charging / discharging rate and the like without the addition of other equipment, thereby providing convenience and cost efficiency. In addition, the recovery rate of discharge energy reaches a maximum of 100% after the precipitates are removed, thereby enabling the lifespan of the battery to be remarkably improved.

Description

Method for removing precipitates from battery cells and precipitate removal system using the same

[0001] The present invention relates to secondary battery technology, and more specifically, to a method for removing precipitates from a battery cell and a precipitate removal system using the same.

[0002] There are various causes of precipitate formation in secondary batteries, and these can vary depending on the type of battery. The main causes of precipitate formation in secondary batteries are generally known to include impurities in the electrolyte, impurities in the electrodes, and improper charging and discharging conditions. Even during normal use, some degree of precipitate formation is inevitable due to repeated charging and discharging.

[0003] To mitigate the problem of these precipitates, it is generally known that it is important to operate the battery within the specified voltage and temperature ranges, avoid overcharging or overdischarging, and follow proper maintenance practices such as regular charging and discharging.

[0004] Meanwhile, vanadium liquid electrodes, which have recently been attracting attention, are used in redox batteries and are a key component in power storage technology. Redox batteries are a technology that addresses volatility issues in power grids and enables the efficient storage of renewable energy.

[0005] Vanadium liquid electrodes store electrical energy by utilizing the various oxidation states of vanadium. Vanadium has the property of being able to be converted into various oxidation states, which allows it to have a large expandability and long life in batteries.

[0006] Vanadium liquid electrodes have various oxidation states, with those in the divalent, trivalent, and tetravalent states exhibiting excellent stability. However, pentavalent vanadium exhibits the problem of precipitation occurring at high temperatures, for example, between 50 and 60°C.

[0007] In fact, these precipitates can block pump flow in vanadium redox flow batteries (VRFBs), reducing battery performance.

[0008] However, in the case of vanadium ion batteries (VIBs) utilizing microfluidic technology, which do not require a pump, the battery operates without issues under charge and discharge conditions even if precipitates form on the positive liquid electrode. However, these precipitates still cause capacity loss in vanadium ion batteries.

[0009] Therefore, there is a need to develop a new method for removing precipitates from various secondary batteries.

[0010] The present invention is intended to solve the above problems, and the inventors of the present invention have researched and developed a technology for removing precipitates generated in a battery cell in order to improve the lifespan of a secondary battery, and as a result, although over-discharge is generally known to have a negative effect on batteries, the inventors of the present invention have discovered that over-discharge controlled under specific conditions helps to remove precipitates and thus restores the performance of the battery, thereby completing the present invention.

[0011] Accordingly, one of the objects of the present invention is to provide a method and system for removing deposits from a battery cell by discharging the battery cell to a voltage range lower than a normal cycle of the battery and then maintaining the lower voltage range for a sufficient time for the deposits from the battery cell to return to an ionic state.

[0012] In addition, another object of the present invention is to provide optimized ranges including voltage range, retention time, charge / discharge rate, number of cycles, etc. for removing precipitates from the battery cell.

[0013] The problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0014] In one aspect of the present invention for solving the above-described problem, a method for removing deposits from a battery cell is provided, which includes a capacity recovery cycle in which a battery cell is discharged in a voltage range lower than a normal cycle of the battery and the deposits from the battery cell are returned to an ionic state, thereby removing the deposits from the battery cell and restoring the capacity of the battery.

[0015] In another aspect of the present invention, a method for removing deposits from a battery cell is provided, the method including a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle includes at least one of the steps of (a) charging with a constant current at a current corresponding to 0.01 C to 1.0 C until the voltage reaches 1.30 V to 1.70 V; and (b) discharging with a constant current at a current corresponding to 0.01 C to 1.0 C until the voltage reaches -1.70 V to 1.10 V, regardless of the order, wherein step (a) or (b) is repeated for at least one cycle, thereby removing the deposits from the battery cell by returning the deposits to an ionic state, thereby restoring the capacity of the battery.

[0016] In another aspect of the present invention, a battery cell deposit removal system is provided, comprising: one or more processors; and a memory coupled to the processors and including instructions executable by the processors, wherein the processor determines to discharge the battery cell to a voltage range lower than a normal cycle of the battery when deposit removal is required, and to remove the deposit by maintaining the lower voltage range.

[0017] According to the method and system for removing precipitates from a battery cell according to the present invention, precipitates generated in a battery cell can be easily removed simply by adjusting voltage, charge / discharge rate, etc. without adding any other equipment, which is convenient and economical.

[0018] In addition, according to the method and system for removing precipitates from a battery cell according to the present invention, the recovery rate of discharge energy after removing precipitates reaches up to 100%, thereby dramatically improving the lifespan of the battery and, in some cases, enabling the battery to be used semi-permanently.

[0019] In addition, when using the conditions such as voltage, charge / discharge rate, etc. according to a preferred embodiment of the present invention, the time required for removing such precipitates can be minimized, thereby enabling rapid removal of precipitates.

[0020] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0021] Figure 1 (a) is a diagram showing the relationship between voltage and current that appear during charging and discharging in a battery.

[0022] Figure 1 (b) is a diagram showing the operation window of a linear section excluding the inflection point sections at both ends.

[0023] Figure 2 is a drawing showing a circle indicating an area that is not commonly used due to high charging.

[0024] Figure 3 is a conceptual diagram for explaining some features of a constant current (CC) control method and a constant voltage (CV) control method applied to battery charging.

[0025] Figure 4 is a schematic diagram of a battery manufactured according to Manufacturing Example 1 of the present invention.

[0026] Figure 5 is a graph showing the production of a precipitate according to Manufacturing Example 2 of the present invention.

[0027] Figure 6 (a) shows a precipitate produced according to Manufacturing Example 2 of the present invention, and (b) is a drawing showing a state in which the precipitate according to at least one embodiment of the present invention has been removed.

[0028] Figure 7 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 1 of the present invention.

[0029] Figure 8 is a graph showing the capacity recovery time required when following Example 1 of the present invention.

[0030] Figure 9 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 2 of the present invention.

[0031] Figure 10 is a graph showing the capacity recovery time required when following Example 2 of the present invention.

[0032] Figure 11 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 3 of the present invention.

[0033] Figure 12 is a graph showing the capacity recovery time required when following Example 3 of the present invention.

[0034] Figure 13 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 4 of the present invention.

[0035] Figure 14 is a graph showing the capacity recovery time required when following Example 4 of the present invention.

[0036] Figure 15 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 5 of the present invention.

[0037] Figure 16 is a graph showing the capacity recovery time required when following Example 5 of the present invention.

[0038] Figure 17 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 6 of the present invention.

[0039] Figure 18 is a graph showing the capacity recovery time required when following Example 6 of the present invention.

[0040] Figure 19 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Comparative Example 1 of the present invention.

[0041] Figure 20 is a graph showing the capacity recovery time required when following Comparative Example 1 of the present invention.

[0042] Figure 21 is a graph showing the discharge energy reduction (%) after precipitate generation and the recovery (%) after precipitate removal in Examples 1-6 and Comparative Example 1.

[0043] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0044] Technical or scientific terms used in the present invention are as defined by those skilled in the art unless otherwise specified.

[0045] Any tool, equipment, method or material named in the present invention refers to a tool, equipment, method or chemical substance commonly used by those skilled in the art, unless otherwise stated to be a specific tool, equipment, method or material only in the present invention.

[0046] In this specification, unless the context clearly dictates otherwise, the terms "comprises," "comprising," and "comprising" will be understood to mean including a stated step, component, or group of steps or components, but not excluding any other step, component, or group of steps or components. Thus, the use of the term "comprising" and the like indicates that the stated components are essential or mandatory, but other components are optional and may or may not be present. The term "consisting of" and the like indicates including and limiting only the item preceding the expression "consisting of." Thus, the expression "consisting of" indicates that the stated components are essential or mandatory and that no other components are present.

[0047] Throughout this specification, the terms “about,” “approximately,” and the like, mean within a range of ±20%, ±19%, ±18%, ±17%, ±16%, ±15%, ±14%, ±13%, ±12%, ±11%, ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1% of the value, more preferably within a range of ±15%, ±10%, or ±5% of the value, and most preferably within a range of ±10% of the value.

[0048] Throughout the specification, when we refer to “A and / or B”, this means A, B or A and B, unless otherwise stated, and when we refer to “C through D”, this means C or more and D or less, unless otherwise stated.

[0049] The following embodiments are presented without the intention of limiting the scope of the present invention.

[0050] As described above, in one aspect of the present invention, a method for removing deposits from a battery cell is proposed, which includes a capacity recovery cycle in which a battery cell is discharged in a voltage range lower than a normal cycle of the battery and the deposits from the battery cell are maintained in the low voltage range so that they return to an ionic state, thereby removing the deposits from the battery cell and recovering the capacity of the battery.

[0051] Fig. 1 (a) is a diagram showing the relationship between voltage and current that appear during charging and discharging in a battery, and Fig. 1 (b) is a diagram showing the operation window of a linear section excluding the inflection point sections at both ends.

[0052] In general, for redox batteries, for example, vanadium-based batteries, the electromotive force due to the ion couple inside the battery can be expressed as the ratio of the concentration of ions before the reaction to the concentration of ions after the reaction according to Nernst's equation as follows.

[0053]

[0054] According to the above equation, there is a positive correlation between OCV and SOC, and as can be seen in (a) of Fig. 1, the slope of the curve increases at both ends. Here, OCV means open circuit voltage, and it means the voltage between the plus and minus two poles when there is no load on the battery, that is, when no current is discharged to the outside, and the maximum value of the open circuit voltage is theoretically equal to the value of the electromotive force of the battery. In addition, SOC represents the state of charge of the battery and is an indicator of the remaining capacity of the battery.

[0055] In this way, since the slope of the curve increases at both ends, in the case of a general battery, the linear section rather than the inflection point section at both ends as in Fig. 1 (b) is set as the operation window (this is usually expressed as the "rated voltage range"), and the SOC (state of charge) is defined based on this. For reference, Fig. 1 is based on CC (Constant Current) charge and discharge, and each number represents an example value rather than an exact value, and although the left and right sides are expressed as if they are symmetrical based on the point where the SOC is 100%, when actually measured, the discharge time is measured to be slightly shorter.

[0056] Figure 2 is a drawing showing a circle indicating an area that is not commonly used due to high charging.

[0057] Typically, battery manufacturers narrow the operating voltage of their batteries to the operating range of the linear section above, because battery response becomes unbalanced near the extreme ends of the graph.

[0058] In particular, for vanadium-based batteries, vanadium has oxidation states of 2, 3, 4 and 5, of which the pentavalent ion (i.e. V 5+ ) tends to precipitate easily because of poor high-temperature stability, which leads to an increase in ions that do not participate in the reaction, indicating a decrease in battery capacity. Therefore, V, such as the area indicated by the circle in the graph of Fig. 2 5+ Areas that have too much charge, or in other words areas that are heavily charged, are generally not used.

[0059] Conversely, below a certain voltage, OCV is also sensitive to changes in SOC, and thus, deviations due to slight performance differences between batteries become large, so it is not generally used.

[0060] However, the inventors of the present invention have researched and developed the above V5+ The inventors have discovered a cycle that restores the performance of a battery cell that has been degraded by precipitation, and this is surprisingly based on a concept that is contrary to conventional wisdom. Specifically, the inventors have discovered that when a battery cell is discharged to a lower voltage than in a normal cycle of a battery, the V dissolved in the electrolyte within the battery cell is released. 5+ It was confirmed that the ions almost disappeared. That is, the V that was precipitated probabilistically 5+ It was confirmed that there is a high possibility that it will dissolve again in the electrolyte and return to ions.

[0061] This is believed to be based, in part, on the following principle, but not limited to: when a battery cell is forcibly discharged, electrons move from the negative electrode to the positive electrode, and at this time, the V present in the negative electrode 2+ is V 3+ , and at the anode, V excluding the precipitated ions 5+ All ions are V 4+ It changes to . However, the negative V 2+ Ions of the positive electrode V 5+ Since the electrons will still outnumber the ions, they will continue to try to move towards the anode, which will cause the precipitated vanadium to dissolve back into the electrolyte and form V 5+ It becomes a forced power that tries to balance the ions between the positive and negative electrodes by being oxidized. That is, the present invention is partly based on the principle of restoring the performance of a battery by forcibly discharging the battery to a voltage range slightly lower than the normal cycle of the battery.

[0062] The concepts and features described herein may be applicable to other types of batteries, but are more preferably applied to vanadium-based batteries.

[0063] Accordingly, the method for removing precipitates from battery cells of the present invention includes a step of discharging a battery cell in a voltage range lower than a normal cycle of the battery, and a capacity recovery cycle in which the low voltage range is maintained so that the precipitates from the battery cell return to an ionic state, thereby removing the precipitates from the battery cell and recovering the capacity of the battery.

[0064] In the present invention, the step of discharging the battery cell to a voltage range lower than a normal cycle of the battery includes discharging to a voltage of 1.70 V or lower. For example, the low voltage range may include 1.70 V, 1.60 V, 1.50 V, 1.40 V, 1.30 V, 1.20 V, 1.10 V, 1.00 V, 0.90 V, 0.80 V, 0.70 V, 0.60 V, 0.50 V, 0.40 V, 0.30 V, 0.20 V, 0.10 V, 0.00 V, or any value or range therebetween.

[0065] Additionally, in the present invention, discharging the battery cell to a voltage range lower than the normal cycle of the battery may include discharging to a negative value, i.e., including a reverse voltage. The voltage ranges accordingly are -0.10V, -0.20V, -0.30V, -0.40V, -0.50V, -0.60V, -0.70V, -0.80V, -0.90V, -1.00V, -1.10V, -1.20V, -1.30V, -1.40V, -1.50V, -1.6V, -1.70V, -1.80V, -1.90V, -2.00V, and may include, but are not limited to, values ​​or ranges therebetween, and may also lower the voltage to a lower value if the device permits.

[0066] Thus, in one embodiment of the present invention, the low voltage range may include, for example, -2.0 V to 1.7 V, -1.9 V to 1.60 V, -1.80 V to 1.55 V, -1.75 V to 1.50 V, or -1.70 V to 1.45 V.

[0067] Since the above voltage range corresponds to a lower range than the cycle of a typical battery, the discharge is preferably performed through forced discharge.

[0068] The method according to the present invention has the advantage of being able to reliably remove precipitates from battery cells in a shorter period of time than when using reverse voltage. However, from the standpoint of ease of implementation, the use of a positive voltage is more preferable. Therefore, those skilled in the art can select and use the appropriate voltage range, depending on the type and purpose of the system.

[0069] In the present invention, discharging to the low voltage range includes discharging with a current corresponding to 0.001 C to 2.0 C, for example, the discharging may include a current corresponding to 0.001 C, 0.005 C, 0.01 C, 0.05 C, 0.1 C, 0.2 C, 0.3 C, 0.4 C, 0.5 C, 0.6 C, 0.7 C, 0.8 C, 0.9 C, 1.0 C, 1.1 C, 1.2 C, 1.3 C, 1.4 C, 1.5 C, 1.6 C, 1.7 C, 1.8 C, 1.9 C, 2.0 C, or a value or range therebetween. In one embodiment of the present invention, the discharge comprises less than 2.0C, less than 1.9C, less than 1.8C, less than 1.5C, less than 1.0C, less than 0.5C, less than 0.1C, or less than 0.01C.

[0070] In the present invention, C-rate is an abbreviation for Current Rate, and is a value indicating the speed of charging, discharging, or both charging and discharging the battery. This is also called the "charge / discharge rate," and the unit is "C," which is an abbreviation for Capacity. The C-rate is the charge / discharge current (A) divided by the rated capacity (Ah) of the battery, and the standard value is 1.0C, and can be calculated as follows.

[0071] C-rate = charge / discharge current (A) / rated capacity of battery (Ah)

[0072] In other words, 1.0C can be seen as the battery output when the battery is depleted in 1 hour.

[0073] The method according to the present invention comprises a cycle in which the low voltage range described above is maintained for a sufficient period of time for the precipitates in the battery cell to return to an ionic state. In the present invention, the charge / discharge cycle maintained in this low voltage range is a cycle for removing the precipitates, and is referred to herein as a "capacity recovery cycle."

[0074] In one embodiment of the present invention, the low voltage range can be maintained continuously, intermittently, periodically, intermittently, or a combination thereof, and can also be maintained in an irregular pattern. In the present invention, the time for which this low voltage state is maintained affects the removal of precipitates, and for efficient removal of precipitates, a fully discharged state, for example, V in the positive electrolyte, is required. 5+ It is important to determine how long the state of almost no voltage is maintained. Accordingly, in the present invention, maintenance of a low voltage state and charge / discharge rate are important factors.

[0075] In one embodiment of the present invention, the low voltage range is maintained by maintaining a discharge state or by repeating charging and discharging. This includes cases where the voltage rises to a range exceeding the low voltage range defined in the present invention through charging and then falls back to the low voltage range according to the present invention.

[0076] In the case of maintaining the above discharge state, it includes maintaining it in a low voltage range for a certain period of time, which may be, for example, 200 hours or less, 150 hours or less, 100 hours or less, 90 hours or less, 80 hours or less, 70 hours or less, 60 hours or less, 50 hours or less, 40 hours or less, 30 hours or less, 20 hours or less, or 10 hours or less, and may include values ​​and ranges therebetween.

[0077] In the case of the above repetition of charging and discharging, it includes performing it with a current corresponding to 0.001C to 2.0C, which may include, for example, 0.001C, 0.005C, 0.01C, 0.05C, 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1.0C, 1.1C, 1.2C, 1.3C, 1.4C, 1.5C, 1.6C, 1.7C, 1.8C, 1.9C, 2.0C, or a value or range therebetween.

[0078] In one embodiment of the present invention, the charge / discharge rate is, for example, less than 2.0C, 1.9C or less, 1.8C or less, 1.5C or less, 1.0C or less, 0.5C or less, 0.1C or less, or 0.01C or less. The current corresponding to each charge / discharge rate is different for each battery, and therefore, the charge / discharge current suggested by the manufacturer of the battery can be used. That is, the current corresponding to the charge / discharge rate is applied according to the specifications set by the battery manufacturer. For example, in the case of a vanadium ion battery (VIB), which is a redox battery used in an embodiment of the present invention, considering the electrochemical characteristics of the vanadium material, the current corresponding to 1.0C is 2.2A, but is not limited thereto.

[0079] In a preferred embodiment of the present invention, the selection of the charge / discharge rate used for the charge / discharge is determined in consideration of the voltage value used, and is preferably selected as a combination to minimize the time required for removing the precipitate. For example, when a relatively low value (e.g., 0.1 C or less) among the charge / discharge rate values ​​defined in the present invention is selected, that is, when the charge / discharge is performed slowly, efficient removal of the precipitate is possible even when a relatively high range of voltage values ​​is used. However, when a relatively high value (e.g., 1.0 C or more) among the charge / discharge rate values ​​defined in the present invention is selected, that is, when the charge / discharge is performed quickly, efficient removal of the precipitate is possible only when a relatively low range of voltage values ​​is selected.

[0080] That is, in the present invention, for efficient removal of precipitates, it is important to maintain a completely discharged state, and for this purpose, it is necessary to maintain slow discharge or charging / discharging in a low voltage range or reverse voltage range for a certain period of time.

[0081] In one embodiment of the present invention, the charging and discharging may be repeated for 1 to 1000 cycles, including values ​​and ranges therebetween. For example, this may be 1 to 100 cycles, 1 to 10 cycles, or 1 to 5 cycles.

[0082] In one embodiment of the present invention, the repetition of charge and discharge in the capacity recovery cycle is maintained for a certain period of time, which is, for example, 200 hours or less, 150 hours or less, 100 hours or less, 90 hours or less, 80 hours or less, 70 hours or less, 60 hours or less, 50 hours or less, 40 hours or less, 30 hours or less, 20 hours or less, or 10 hours or less, and may include values ​​and ranges therebetween.

[0083] In one embodiment of the present invention, the present invention may additionally utilize a standard cycle (reference cycle) according to the standard specifications of the Korea Battery Industry Association to perform battery capacity verification. This may also be referred to as a "capacity verification cycle" from the perspective of battery capacity verification of the present invention. However, in the following description, the "capacity verification cycle" may be defined differently from the charge / discharge rate and voltage / current conditions specified in the standard specifications of the Korea Battery Industry Association to enhance capacity verification efficiency.

[0084] The capacity check cycle is a cycle used to determine the amount of discharge energy a battery can exhibit after removing precipitates. The capacity check cycle may be repeated, for example, from 1 to 1,000 cycles, and may include values ​​and ranges therebetween. More preferably, the capacity check cycle may be repeated, for example, from 1 to 100 cycles, from 1 to 10 cycles, or from 1 to 5 cycles.

[0085] In one embodiment of the present invention, the capacity recovery cycle and the standard cycle (capacity verification cycle) may be performed alternately and repeatedly. For example, a combination of 1 to 10 capacity recovery cycles followed by 1 to 10 capacity verification cycles is possible, and such a combination may be repeated 100 times, 50 times, 30 times, 20 times, 10 times, 5 times, 4 times, 3 times, 2 times, or 1 time, and may include values ​​and ranges therebetween.

[0086] In the case of the charge / discharge rate and voltage in the capacity check cycle, a charge / discharge rate of about 1.0C and a voltage of about 1.1 to 1.7V are preferably used, but are not limited thereto, and it is possible to select and use an appropriate charge / discharge rate and voltage for checking the capacity of the battery. For example, a combination of a charge / discharge rate of 0.5C to 1.5C, 0.6C to 1.4C, 0.7C to 1.3C, 0.8C to 1.2C, or 0.9C to 1.1C and a voltage of 0.8 to 2.0V, 0.9 to 1.9V, 1.0 to 1.8V, or 1.1 to 1.7V can be used.

[0087] According to another aspect of the present invention, a method for removing deposits from a battery cell includes a capacity recovery cycle in which the battery cell is discharged to a lower voltage range than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle includes at least one of the steps of (a) charging with a constant current (CC) at a current corresponding to 0.01 C to 2.0 C until the voltage reaches 1.30 V to 1.70 V; and (b) discharging with a constant current at a current corresponding to 0.01 C to 2.0 C until the voltage reaches -1.70 V to 1.10 V, regardless of the order, wherein step (a) or (b) is repeated for at least one cycle each, thereby removing the deposits from the battery cell by returning the deposits to an ionic state, thereby recovering the capacity of the battery.

[0088] The above "including without regard to order" means that all cases where (a) is performed first and (b) is performed, or (b) is performed first and (a) is performed. Furthermore, steps (a) and (b) may each be repeated one or more cycles, and thus steps (a) and (b) may each be individually repeated as many cycles as desired. For example, steps (a) or (b) may each be repeated 1 to 10 cycles.

[0089] FIG. 3 is a conceptual diagram illustrating some features of a constant current (CC) control method and a constant voltage (CV) control method applied to battery charging according to at least one embodiment of the present invention.

[0090] Referring to Figure 3, when charging (or discharging) a battery, CC control and / or CV control are used. Since CV control maintains a fixed voltage, even at high SOCs, the voltage remains constant and the current decreases. This means it's a safe control method near full charge. Conversely, when CV is applied at low SOCs, the potential difference between the anodes is low, but the voltage is high, resulting in a large IR value, which can significantly increase the current, potentially posing a risk.

[0091] Meanwhile, CC control maintains a fixed current flow, so the same amount of charge is transferred per unit of time regardless of the SOC. This means it can be considered a safe control method even in low SOC situations. Conversely, as the SOC increases, if the response to rapid voltage changes is delayed, the safe voltage range can be temporarily exceeded.

[0092] Therefore, many batteries are charged using CC-CV linkage for safe charging.

[0093] In one embodiment of the present invention, step (a) may further include a step of performing constant voltage charging for a voltage reached after charging with a constant current. In one embodiment of the present invention, step (b) may further include a step of performing constant voltage discharging for a voltage reached after discharging with a constant current. In one embodiment of the present invention, it is also possible to include both steps (a) and (b). The additional inclusion of these steps in the present invention can further accelerate the removal of precipitates by enabling a stable extension of the residence time at a low voltage.

[0094] In one embodiment of the present invention, in steps (a), (b), or (a) and (b), it is more preferable to use a charge / discharge rate of 0.01 C to 1.0 C. If charge / discharge is performed at a high output exceeding this, the SOC range may become narrow, thereby failing to provide sufficient time and conditions for ionization of precipitates.

[0095] In one embodiment of the present invention, the selection of the charge / discharge rate used for charging / discharging should be determined in consideration of the voltage value used. For example, when a relatively high charge / discharge rate, such as 1.0 C or higher, is used in step (a), it is preferable to limit the voltage range to 1.30 V to 1.45 V for more efficient removal of battery cell deposits.

[0096] In one embodiment of the present invention, the time maintained in the low voltage range is, for example, 200 hours or less, 150 hours or less, 100 hours or less, 90 hours or less, 80 hours or less, 70 hours or less, 60 hours or less, 50 hours or less, 40 hours or less, 30 hours or less, 20 hours or less, or 10 hours or less, and may include values ​​and ranges therebetween.

[0097] The method for removing precipitates from the battery cell according to the present invention can be implemented in more specific embodiments as follows, for example.

[0098] In one embodiment, a method for removing precipitates from a battery cell according to the present invention comprises a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the lower voltage range of the battery cell, wherein the capacity recovery cycle comprises:

[0099] (a) a step of charging with a constant current until reaching about 1.70 V with a current of about 0.22 A (0.1 C);

[0100] (b) discharging at a constant current until it reaches about 1.10 V with a current of about 0.22 A (0.1 C); and

[0101] (c) a step of repeating steps (a) and (b) about 5 cycles,

[0102] This includes a method for removing precipitates from a battery cell, in which the capacity of the battery is restored by returning the precipitates from the battery cell to an ionic state.

[0103] In another embodiment, a method for removing precipitates from a battery cell according to the present invention comprises a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle comprises:

[0104] (a) Discharging at a constant current until reaching about 0 V with a current of about 2.2 A (1 C);

[0105] (b) a step of performing a constant voltage discharge of approximately 0 V until the current becomes approximately 0.22 A (0.1 C);

[0106] (c) a step of charging with a constant current until reaching about 1.30 V with a current of about 2.2 A (1 C);

[0107] (d) a step of charging at a constant voltage of about 1.3 V until the current becomes about 0.22 A (0.1 C); and

[0108] (e) a step of repeating steps (a) to (d) about 5 cycles,

[0109] This includes a method for removing precipitates from a battery cell, in which the capacity of the battery is restored by returning the precipitates from the battery cell to an ionic state.

[0110] In addition, the method includes a capacity check cycle to check the degree of recovery after the above repetition step.

[0111] (f) a step of charging with a constant current until reaching about 1.70 V with a current of about 2.2 A (1 C);

[0112] (g) discharging at a constant current until it reaches about 1.10 V with a current of about 2.2 A (1 C); and

[0113] (h) It may additionally include a step of repeating steps (f) and (g) about 5 cycles.

[0114] Additionally, steps (a) to (h) above can be performed repeatedly.

[0115] In another embodiment, a method for removing precipitates from a battery cell according to the present invention comprises a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle comprises:

[0116] (a) discharging at a constant current until reaching about 0 V with a current of about 2.2 A (1 C); and

[0117] (b) a step of discharging with a constant current until it reaches about 0 V with a current of about 0.022 A (0.01 C), or performing a constant voltage discharge of about 0 V until the current becomes about 0.022 A (0.01 C),

[0118] This includes a method for removing precipitates from a battery cell, in which the capacity of the battery is restored by returning the precipitates from the battery cell to an ionic state.

[0119] In addition, the above method includes a capacity check cycle to check the degree of recovery after the above step (b).

[0120] (c) a step of charging with a constant current until it reaches about 1.70 V with a current of about 2.2 A (1 C);

[0121] (d) discharging at a constant current until it reaches about 1.10 V with a current of about 2.2 A (1 C); and

[0122] (e) It may additionally include a step of repeating steps (c) and (d) about 5 cycles.

[0123] Additionally, steps (a) to (e) above can be performed repeatedly.

[0124] In another embodiment, a method for removing precipitates from a battery cell according to the present invention comprises a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle comprises:

[0125] (a) discharging at a constant current until it reaches about 1.10 V with a current of about 2.2 A (1 C); and

[0126] (b) a step of discharging at a constant current of about 0.022 A (0.01 C) until the voltage reaches about 1.1 V, or a step of performing a constant voltage discharge of about 1.1 V until the current reaches about 0.022 A (0.01 C),

[0127] This includes a method for removing precipitates from a battery cell, in which the capacity of the battery is restored by returning the precipitates from the battery cell to an ionic state.

[0128] In addition, the above method includes a capacity check cycle to check the degree of recovery after the above step (b).

[0129] (c) may additionally include a step of repeating the cycle of charging with a constant current until reaching about 1.70 V with a current of about 2.2 A (1 C) and discharging with a constant current until reaching about 1.10 V with a current of about 2.2 A (1 C) about 10 times.

[0130] Additionally, steps (a) to (c) above can be performed repeatedly.

[0131] In another embodiment, a method for removing precipitates from a battery cell according to the present invention comprises a capacity recovery cycle in which the battery cell is discharged to a voltage range lower than a normal cycle of the battery, thereby maintaining the low voltage range of the battery cell, wherein the capacity recovery cycle comprises:

[0132] (a) a step of repeating the cycle of charging with a constant current until reaching about 1.45 V with a current of about 2.2 A (1 C) and discharging with a constant current until reaching about 1.10 V with a current of about 2.2 A (1 C) approximately 5 times,

[0133] This includes a method for removing precipitates from a battery cell, in which the capacity of the battery is restored by returning the precipitates from the battery cell to an ionic state.

[0134] In addition, the method includes a capacity check cycle to check the degree of recovery after the step (a).

[0135] (b) may additionally include a step of repeating the cycle of charging with a constant current until reaching about 1.70 V with a current of about 2.2 A (1 C) and discharging with a constant current until reaching about 1.10 V with a current of about 2.2 A (1 C) about 5 times.

[0136] Additionally, steps (a) and (b) above can be performed repeatedly.

[0137] The method for removing deposits from a battery cell according to the present invention can be used in various redox (i.e., oxidation-reduction) batteries, including batteries using a liquid electrode. The liquid electrode contains ions in which a redox reaction occurs. The first liquid electrode is an electrolyte in which a cathode redox couple is dissolved. The cathode redox couple can be implemented with a material including at least one of transition metals such as titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), or zinc (Zn), bromine (Br), and cesium (Cs), and the electrolyte of embodiments of the present invention includes vanadium (V) as the V 2+ / V 3+ The redox couple can be dissolved. The first liquid electrode can be an acidic aqueous solution that conducts current through ionization, preferably containing sulfuric acid. In the present embodiment, the first liquid electrode can be prepared by dissolving VOSO4 (vanadylsulfate), V2O5 (vanadium pentoxide), or another suitable substance in an H2SO4 aqueous solution.

[0138] The first liquid electrode initiates the first half-reaction. The first half-reaction is as follows, where the right arrow (->) indicates the direction of the discharge reaction and the left arrow (<-) indicates the direction of the charge reaction.

[0139] V 2+ <-> V 3+ + e -

[0140] During discharge, vanadium 2 ions are oxidized to vanadium 3 ions, and during charge, vanadium 3 ions are reduced to vanadium 2 ions.

[0141] The second liquid electrode is an electrolyte in which an anode redox couple is dissolved. The anode redox couple can be implemented with a material including at least one of transition metals such as titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), or zinc (Zn), bromine (Br), and cesium (Cs), and in embodiments of the present invention, V 4+ / V 5+ A redox couple exists. The second liquid electrode may be an acidic aqueous solution that conducts current through ionization, and a representative example is sulfuric acid. In the present embodiment, the second liquid electrode may be manufactured by dissolving VOSO4 (vanadylsulfate) or V2O5 (vanadium pentoxide) or another suitable substance in an H2SO4 aqueous solution.

[0142] The second liquid electrode initiates the second half-reaction. The second half-reaction is as follows, where the right arrow (->) indicates the direction of the discharge reaction and the left arrow (<-) indicates the direction of the charge reaction.

[0143] V 5+ + e - <-> V 4+

[0144] During discharge, vanadium pentavalent ions are reduced to vanadium tetravalent ions, and during charge, vanadium tetravalent ions are oxidized to vanadium pentavalent ions.

[0145] As previously discussed, the first liquid electrode and the second liquid electrode are composed of the same components or materials. The first liquid electrode and the second liquid electrode contain vanadium ions in an electrolyte of the same components. Hereinafter, the first liquid electrode and the second liquid electrode are collectively referred to as the liquid electrode.

[0146] Examples of vanadium-based batteries include vanadium redox batteries (VRBs), vanadium redox flow batteries (VRFBs or VFRBs), vanadium flow batteries (VFBs), and vanadium ion batteries (VIBs). These redox batteries are being applied or are expected to be utilized in various energy storage systems (ESS / EES) and various related fields of the battery industry. Vanadium-based batteries have the advantages of conventional redox flow batteries (RFBs), but compared to conventional non-vanadium-based RFBs, they have a lower risk of fire and are less likely to break due to the inherent properties of vanadium.

[0147] In particular, in the case of a vanadium ion battery (VIB), which is a water-based battery developed by the inventors of the present invention, including a vanadium liquid electrode, when the battery cell is forcibly discharged according to the method for removing precipitates according to the present invention, electrons move from the negative electrode to the positive electrode, and at this time, V present in the negative electrode 2+ is V 3+ is oxidized, and V excluding the precipitated ions at the anode 5+ All ions are V 4+ is reduced to V of the cathode 2+ Ions of the positive electrode V 5+ Since the electrons will still outnumber the ions, they will continue to try to move towards the anode, which will cause the precipitated vanadium to dissolve back into the electrolyte and form V 5+ It is oxidized to become a driving force to balance the ions between the positive and negative electrodes. As a result, at the positive liquid electrode, the precipitated vanadium dissolves again in the electrolyte and forms V 5+ It is oxidized to enable removal of precipitates (V2O5).

[0148] When the method for removing precipitates according to the present invention is used, the discharge energy of the battery is recovered by 95 to 100%, more preferably 99 to 100%, by removing the precipitates.

[0149] According to another aspect of the present invention, there is provided a battery cell deposit removal system comprising: one or more processors; and a memory connected to the processors and including instructions executable by the processors, wherein the processor determines to remove deposits by discharging the battery cells to a voltage range lower than a normal cycle of the battery when removal of deposits is required, and maintaining the lower voltage range for a predetermined period of time.

[0150] In the present invention, when removal of precipitates is required, the processor determines to remove the precipitates by discharging the battery cell to a voltage range lower than the normal cycle of the battery and maintaining the lower voltage range for a predetermined period of time.

[0151] In one embodiment of the present invention, the removal of the precipitate is set based on a certain cycle, for example, a one-year cycle, a six-month cycle, a three-month cycle, a one-month cycle, a two-week cycle, or a one-week cycle.

[0152] In one embodiment of the present invention, removal of the precipitate is determined by detecting a certain amount of the precipitate by one or more sensors.

[0153] In one embodiment of the present invention, the removal of the precipitate is determined by measuring the decrease in discharge energy of the battery. The decrease may be greater than 0% and less than or equal to 100%, and may include any value or range therebetween. For example, the decrease may be greater than or equal to 40%, greater than or equal to 50%, or greater than or equal to 60%.

[0154] The precipitate removal system according to the present invention can be included as a part of a power management system (PMS) or an energy management system (EMS), and can be used to control a power conversion system (PCS).

[0155]

[0156] Hereinafter, the present invention will be described in more detail through examples. The following examples are intended to more specifically illustrate the present invention, and the scope of the present invention is not limited by these examples.

[0157]

[0158] Example

[0159] Manufacturing Example 1: Manufacturing of a Battery

[0160] Figure 4 is a schematic diagram of a battery manufactured according to Manufacturing Example 1 of the present invention.

[0161] The battery to be used in the example was manufactured through the following process. After preparing the frame, a metal current collector / carbon current collector / solid electrode / separator / solid electrode / carbon current collector / metal current collector were sequentially stacked. At this time, a current collector containing aluminum was used as the metal current collector, a separator containing carbon was used as the carbon current collector, carbon felt was used as the solid electrode, and an ion-selective separator was used as the separator. After the battery was sealed and manufactured, a liquid electrode was injected through a vacuum post-injection process. The liquid electrode was manufactured by dissolving V2O5 (vanadium pentoxide) in an H2SO4 aqueous solution and used at a concentration of 2.1 M. Through this, a vanadium ion battery (VIB) having a structure as shown in Fig. 4 was manufactured. Subsequent tests were conducted using the battery.

[0162]

[0163] Manufacturing Example 2: Formation of precipitate

[0164] FIG. 5 is a graph showing the production of a precipitate according to Manufacturing Example 2 of the present invention, FIG. 6 (a) shows a precipitate produced according to Manufacturing Example 2 of the present invention, and FIG. 6 (b) is a drawing showing a state in which a precipitate has been removed according to at least one embodiment of the present invention.

[0165] Using the vanadium ion battery (VIB) manufactured in the above Manufacturing Example 1, the temperature of the fully charged battery cell was increased to induce precipitation. To this end, the following steps were performed.

[0166] 1. The VIB Layer was charged with a constant current of 2.2A (1C) at 25℃ in a warm room until it reached 1.70V.

[0167] 2. Discharged at a constant current of 2.2A (1C), the same as charging, until it reached 1.1V.

[0168] 3. Charging and discharging were repeated twice under the above conditions.

[0169] 4. In the third cycle, the battery was charged again with a constant current of 2.2 A (1 C) until it reached 1.70 V.

[0170] 5. When charging was completed by reaching 1.70 V, the temperature of the storage tank was increased to 50°C and a 50-hour rest period was allowed to induce the formation of precipitates on the positive liquid electrode (the section indicated by the left and right arrows in Fig. 5). Through this, the formation of precipitates as shown in Fig. 6 (a) was confirmed.

[0171] 6. The discharge energy value after the precipitate was generated was confirmed by discharging at a constant current until it reached 1.1 V with a current of 2.2 A (1 C).

[0172] Below, tests were conducted using various conditions to find a cycle that removes the precipitate generated in the above manufacturing example 2 in the shortest time.

[0173]

[0174] Example 1: Reverse voltage conditions

[0175] Figure 7 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 1 of the present invention.

[0176] In this example, a method was used to lower the voltage of the battery cell to -1.7 V (reverse voltage) and then return it to its original state (Fig. 7), and the specific experimental conditions are as follows.

[0177] 1. To prepare for the experiment after precipitation (1.1 V), the cathode wire was connected to the VIB Layer metal collector by exchanging the cathode wire with the anode wire (corresponding to point A in the left drawing of Fig. 7).

[0178] 2. For forced discharge to -1.7V, it was charged with constant current until it reached 1.70V with a current of 2.2A (1C) (therefore, the 1.7V shown on the graph is actually -1.7V).

[0179] 3. After charging was completed, a rest period of 1 hour was performed (waiting in OC (Open Circuit) state near -1.5V).

[0180] 4. To prepare for the experiment (-1.5 V), the positive wire was again connected to the negative wire and the negative wire was again connected to the VIB Layer metal collector by swapping them (corresponding to point B in the left drawing of Fig. 7).

[0181] 5. Charged with a constant current until reaching 1.70 V with a current of 2.2 A (1 C), and discharged with a constant current until reaching 1.10 V with a current of 2.2 A (1 C).

[0182] 6. Charging and discharging were repeated by applying the above 5 experimental conditions (1.1~1.7 V cycle repetition).

[0183] At this time, the above numbers 2 to 5 correspond to capacity recovery cycles for removing precipitates, and number 6 corresponds to capacity confirmation cycles for performance confirmation.

[0184] Figure 8 is a graph showing the capacity recovery time required when following Example 1 of the present invention.

[0185] As a result of the experiment according to this example, the vanadium pentavalent electrolyte was discharged until it became tetravalent, trivalent, and divalent, and during this process, the vanadium precipitates adsorbed on the solid electrode (carbon felt) were removed through an electrochemical reaction, thereby recovering 100% of the discharge energy. As shown in Fig. 8, the time taken for the pure capacity recovery cycle was 4 hours, and the time taken for the standard cycle for capacity confirmation was 126 hours. Therefore, the total time taken for the capacity recovery including these was 130 hours.

[0186]

[0187] Example 2: 1.1~1.7V(0.1C) charge / discharge conditions

[0188] Figure 9 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 2 of the present invention.

[0189] As shown in Fig. 9, in this embodiment, a charge / discharge condition of 1.1 to 1.7 V (0.1 C) was used, and the specific experimental conditions are as follows.

[0190] 1. Charged with a constant current of 0.22 A (0.1 C) until reaching 1.70 V, and discharged with a constant current of 0.22 A (0.1 C) until reaching 1.10 V.

[0191] 2. Five cycles of charging and discharging were repeated by applying the experimental conditions of No. 1 above.

[0192] 3. Charged with a constant current until reaching 1.70 V with a current of 2.2 A (1 C), and discharged with a constant current until reaching 1.10 V with a current of 2.2 A (1 C).

[0193] 4. Five cycles of charge and discharge were repeated by applying the three experimental conditions above.

[0194] At this time, the above numbers 1 and 2 correspond to capacity recovery cycles for removing precipitates, and numbers 3 and 4 correspond to capacity confirmation cycles for performance confirmation.

[0195] Figure 10 is a graph showing the capacity recovery time required when following Example 2 of the present invention.

[0196] According to the experimental results of this example, it was confirmed that the capacity was 100% recovered after only 3 cycles of 1.1~1.7V charge / discharge at a current of 0.1C (0.22A). Therefore, as illustrated in Fig. 10, the time taken for the capacity recovery cycle was 66 hours, and a separate standard cycle for capacity confirmation was not performed. Therefore, the total time taken for capacity recovery was 66 hours.

[0197]

[0198] Example 3: 0~1.3V, 1C to 0.1C CC-CV charge / discharge conditions

[0199] Figure 11 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 3 of the present invention.

[0200] As shown in Fig. 11, in this embodiment, 0 to 1.3 V, 1 C to 0.1 C CC-CV charge / discharge conditions were used, and the specific experimental conditions are as follows.

[0201] 1. Discharge with a constant current until it reaches 0 V with a current of 2.2 A (1 C), and then discharge with a constant voltage of 0 V until the current becomes 0.22 A (0.1 C).

[0202] 2. Constant current charging was performed until the voltage reached 1.30 V with a current of 2.2 A (1 C), and then constant voltage charging was performed at 1.3 V until the current reached 0.22 A (0.1 C).

[0203] 3. Five cycles of charge and discharge were repeated by applying the experimental conditions 1 and 2 above.

[0204] 4. It was charged with a constant current until it reached 1.70 V with a current of 2.2 A (1 C), and discharged with a constant current until it reached 1.10 V with a current of 2.2 A (1 C).

[0205] 5. Five cycles of charge and discharge were repeated by applying the above four experimental conditions.

[0206] At this time, the above numbers 1 to 3 correspond to capacity recovery cycles for removing precipitates, and numbers 4 and 5 correspond to capacity confirmation cycles for performance confirmation.

[0207] Figure 12 is a graph showing the capacity recovery time required when following Example 3 of the present invention.

[0208] As a result of the experiment according to this example, the potential difference between the positive and negative electrodes became negligible by performing charge and discharge at a low voltage, and the oxidation numbers of the positive and negative electrolytes were readjusted to between 3.4 and 3.6. Accordingly, the vanadium pentavalent ions in the electrolyte were almost removed, and the vanadium precipitates adsorbed on the solid electrode for ion balance were ionized and removed, recovering 100% of the discharge energy. At this time, the time taken for the pure capacity recovery cycle was 33 hours, and the time taken for the standard cycle for capacity confirmation was 100 hours. Therefore, the total time taken for capacity recovery including these was 133 hours.

[0209]

[0210] Example 4: 0 V CV discharge conditions

[0211] Figure 13 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 4 of the present invention.

[0212] As shown in Fig. 13, in this embodiment, 0 V CV discharge conditions were used, and the specific experimental conditions are as follows.

[0213] 1. Discharge with a constant current until it reaches 0 V with a current of 2.2 A (1 C), and then discharge with a constant voltage of 0 V until the current becomes 0.022 A (0.01 C).

[0214] 2. Afterwards, the cycle of charging with a constant current until reaching 1.70 V with a current of 2.2 A (1C) and discharging with a constant current until reaching 1.10 V with a current of 2.2 A (1C) was repeated 5 times.

[0215] 3. Experiments 1 and 2 were repeated thereafter.

[0216] At this time, No. 1 above corresponds to a capacity recovery cycle for removing precipitates, and No. 2 corresponds to a capacity confirmation cycle for performance confirmation.

[0217] Figure 14 is a graph showing the capacity recovery time required when following Example 4 of the present invention.

[0218] According to the experimental results of this example, the precipitate of the pentavalent liquid electrode was completely removed when the composition changed from trivalent to tetravalent when discharged at 0 V. The time taken for the capacity recovery cycle was 45 hours, and the time taken for the standard cycle for capacity confirmation was 325 hours. Therefore, the total time taken for capacity recovery was 370 hours.

[0219]

[0220] Example 5: 1.1 V CV discharge conditions

[0221] Figure 15 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 5 of the present invention.

[0222] As shown in Fig. 15, in this embodiment, 1.1 V CV discharge conditions were used, and the specific experimental conditions are as follows.

[0223] 1. Discharge with a constant current of 2.2A (1C) until it reaches 1.10V, and then discharge with a constant voltage of 1.1V until the current becomes 0.022A (0.01C).

[0224] 2. Afterwards, the cycle of charging with a constant current until reaching 1.70 V with a current of 2.2 A (1 C) and discharging with a constant current until reaching 1.10 V with a current of 2.2 A (1 C) was repeated 10 times.

[0225] 3. Experiments 1 and 2 were repeated thereafter.

[0226] At this time, No. 1 above corresponds to a capacity recovery cycle for removing precipitates, and No. 2 corresponds to a capacity confirmation cycle for performance confirmation.

[0227] Figure 16 is a graph showing the capacity recovery time required when following Example 5 of the present invention.

[0228] The experimental results of this example showed that the vanadium precipitates adsorbed on the solid electrode were removed through an electrochemical reaction, resulting in a 99.4% recovery of discharge energy. The capacity recovery cycle took 27 hours, and the standard cycle for capacity verification took 223 hours. Therefore, the total capacity recovery time, including these two cycles, was 250 hours.

[0229]

[0230] Example 6: 1.1~1.45V(1C) charge / discharge conditions

[0231] Figure 17 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Example 6 of the present invention.

[0232] As shown in Fig. 17, in this embodiment, a charge / discharge condition of 1.1 to 1.45 V (1 C) was used, and the specific experimental conditions are as follows.

[0233] 1. Charged with a constant current until reaching 1.45 V with a current of 2.2 A (1 C), and discharged with a constant current until reaching 1.10 V with a current of 2.2 A (1 C).

[0234] 2. Five cycles of charging and discharging were repeated by applying the experimental conditions of No. 1 above.

[0235] 3. Charged with a constant current until reaching 1.70 V with a current of 2.2 A (1 C), and discharged with a constant current until reaching 1.10 V with a current of 2.2 A (1 C).

[0236] 4. Five cycles of charge and discharge were repeated by applying the three experimental conditions above.

[0237] 5. Afterwards, the experimental conditions 1 to 4 were applied again and repeated.

[0238] At this time, the above 1 and 2 correspond to capacity recovery cycles for removing precipitates, and 3 and 4 correspond to capacity confirmation cycles for performance confirmation.

[0239] Figure 18 is a graph showing the capacity recovery time required when following Example 6 of the present invention.

[0240] According to the experimental results of this example, the vanadium precipitates adsorbed on the solid electrode were removed through an electrochemical reaction, resulting in 99.9% recovery of the discharge energy. The capacity recovery cycle took 117 hours, and the standard cycle for capacity verification took 326 hours. Therefore, the total capacity recovery time, including these two cycles, was 443 hours.

[0241]

[0242] Comparative Example 1: 1.1~1.7V(1C) charge / discharge conditions

[0243] Figure 19 is a graph showing changes in discharge energy according to experimental conditions and cycles according to Comparative Example 1 of the present invention.

[0244] In this comparative example, 1.1 to 1.7 V (1 C) charge / discharge conditions were used, and the specific experimental conditions are as follows.

[0245] 1. Charged with a constant current until reaching 1.70 V with a current of 2.2 A (1 C), and discharged with a constant current until reaching 1.10 V with a current of 2.2 A (1 C).

[0246] 2. Charging and discharging were repeated by applying the experimental conditions in number 1 above.

[0247] Figure 20 is a graph showing the capacity recovery time required when following Comparative Example 1 of the present invention.

[0248] This comparative example is the result of performing charge and discharge under conditions corresponding to a standard cycle (i.e., a capacity verification cycle). As shown in Fig. 20, when charging and discharging at 1.1 to 1.7 V with a current of 1 C used in the standard cycle, the discharge energy recovery rate was 99.8%, and the time taken for capacity recovery was 1515 hours, which was the longest time.

[0249]

[0250] Figure 21 is a graph showing the discharge energy reduction (%) after precipitate generation and the recovery (%) after precipitate removal in Examples 1-6 and Comparative Example 1.

[0251] In addition, the results of Examples 1 to 6 and Comparative Example 1 are summarized and shown in the table below.

[0252] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Experimental Conditions Reverse Voltage (1C) 1.1~1.7 V Charge / Discharge (0.1C) 0~1.3 V Charge / Discharge (1C) 0 V CV Discharge (0.01C) 1.1 V CV Discharge (0.01C) 1.1~1.45 V Charge / Discharge (1C) 1.1~1.7 V Charge / Discharge (1C) Time for Capacity Recovery (h) 130661333702504431515b. Time corresponding to the standard cycle run to check the capacity (h) 126-1003252233261515a. Time for Pure Capacity Recovery Cycle (h) 466334527117

[0253] As confirmed in Table 1 and FIG. 21, the final discharge energy recovery rate was over 99% in all experimental conditions, but in terms of the time taken for capacity recovery, when using the conditions according to the embodiments of the present invention, the time taken for pure capacity recovery cycle was very short, 117 hours or less, and even when including the capacity confirmation cycle, it was 443 hours or less, whereas in the case where the time spent at low voltage was short, as in Comparative Example 1, it was confirmed that the time taken for capacity recovery was very long, 1515 hours.

[0254] The detailed description of the preferred embodiments of the present invention disclosed above has been provided to enable those skilled in the art to implement and practice the present invention. While the above description has been made with reference to preferred embodiments of the present invention, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the scope of the present invention. For example, those skilled in the art can utilize the individual components described in the above-described embodiments in combination with each other.

[0255] Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0256] The method for removing precipitates from a battery cell according to the present invention as described above not only enables removal of precipitates, but also provides specific conditions that enable rapid removal of such precipitates, so that it can be used in various ways for removing precipitates from various secondary batteries.

Claims

1. A method for removing precipitates from a battery cell, Discharging said battery cells to a voltage range lower than the normal cycle of the battery; applying a capacity recovery cycle that maintains the low voltage range so that the precipitates of the battery cell return to an ionic state; A method for removing precipitates from a battery cell, wherein the precipitates from the battery cell are removed thereby restoring the capacity of the battery.

2. In paragraph 1, A method for removing deposits from a battery cell, wherein the low voltage range is 1.70 V or less.

3. In paragraph 1, A method for removing deposits from a battery cell, wherein the low voltage range is -1.70 V to 1.45 V.

4. In paragraph 1, A method for removing deposits from a battery cell, wherein the above low voltage range is maintained continuously, intermittently, periodically, intermittently or a combination thereof.

5. In paragraph 1, A method for removing deposits from a battery cell, wherein the above low voltage range is maintained by maintaining a discharge state or by repeating charge and discharge.

6. In paragraph 5, A method for removing deposits from a battery cell, wherein the above charging and discharging are repeated 1 to 100 cycles.

7. In paragraph 5, A method for removing deposits from a battery cell, wherein the above charging and discharging is performed at a current corresponding to 0.01C to 1.0C.

8. In paragraph 5, A method for removing precipitates from a battery cell, wherein the above charging and discharging is performed at 0.1C or less.

9. A method for removing precipitates from a battery cell, The method comprises applying a capacity recovery cycle to maintain the low voltage range of the battery cell by discharging the battery cell to a voltage range lower than the normal cycle of the battery, The above capacity recovery cycle is (a) a step of charging with a constant current until it reaches 1.30 V to 1.70 V with a current corresponding to 0.01 C to 2.0 C; and (b) A step of discharging with a constant current until it reaches -1.70 V to 1.10 V with a current corresponding to 0.01 C to 2.0 C. Including one or more of the following in any order: Each of the above steps (a) or (b) is repeated at least once a cycle, A method for removing precipitates from a battery cell, wherein the precipitates in the battery cell are removed by returning to an ionic state, thereby restoring the capacity of the battery.

10. In paragraph 9, The above charging step additionally includes a step of performing constant voltage charging for the voltage reached after charging, or The above discharging step additionally includes a step of performing a constant voltage discharge for the voltage reached after discharging, or A method for removing deposits from a battery cell, including all of these.

11. In paragraph 9, A method for removing deposits from a battery cell, wherein a charge / discharge rate of 0.01C to 1.0C is used in steps (a), (b) or (a) and (b).

12. In paragraph 9, A method for removing deposits from a battery cell, wherein the voltage range is limited to 1.30 V to 1.45 V when 1.0 C or more is used in the above step (a).

13. In paragraph 9, A method for removing precipitates from a battery cell, wherein each of the steps (a) or (b) is repeated 1 to 10 cycles.

14. In any one of paragraphs 1 to 13, A method for removing deposits from a battery cell, further comprising a standard cycle for checking the capacity of the battery.

15. In any one of paragraphs 1 to 13, A method for removing precipitates from a battery cell, wherein the capacity recovery cycle is 150 hours or less.

16. In any one of paragraphs 1 to 13, A method for removing deposits from a battery cell, wherein the above battery is an aqueous battery.

17. In any one of paragraphs 1 to 13, A method for removing deposits from a battery cell, wherein the battery comprises a vanadium liquid electrode.

18. In any one of paragraphs 1 to 13, A method for removing deposits from a battery cell, wherein the above battery is a vanadium ion battery (VIB).

19. In any one of paragraphs 1 to 13, A method for removing precipitates from a battery cell, wherein the removal of the above precipitates is performed at a positive liquid electrode.

20. In any one of paragraphs 1 to 13, The above battery contains vanadium, and the method for removing precipitates from a battery cell is characterized in that the precipitated pentavalent vanadium is dissolved again in the electrolyte and returns to ions.

21. One or more processors; and A system for removing sediment from a battery cell, the system comprising a memory connected to the processor and including instructions executable by the processor, The above processor: If removal of precipitates is required, the battery cells are discharged to a voltage range lower than the normal cycle of the battery, A battery cell deposit removal system configured to determine to remove deposits by maintaining the above low voltage range for a predetermined period of time.

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