Battery management system, battery pack including the same, and method for establishing charging protocol of lithium secondary battery

Abstract

A method for establishing a charging protocol of a lithium secondary battery and a battery management system according to the present invention measure a closed-circuit voltage (CCV x ) and an open-circuit voltage (OCV SOCx ) corresponding to a state of charge (SOC SOCx ) during charging at each charging current (I) for a two-electrode battery cell, substitute the measured CCV SOCx and OCV SOCx into the following formula (1) to calculate an internal resistance value (R SOCx ) corresponding to the state of charge, collect an internal resistance profile obtained by plotting (plotting) the internal resistance values (R SOCx ) corresponding to the state of charge for each charging current (I), and determine a limiting state of charge corresponding to each charging current from the internal resistance profile. [Formula (1)] Internal resistance value (R SOCx ) corresponding to the state of charge = (CCV SOCx - OCV SOCx ) / I

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0147912, filed on November 8, 2022.

[0002] The present invention relates to a method for establishing a rapid charging protocol that reflects heat generation and internal resistance associated with charging and discharging of a large-capacity battery cell, a battery management system capable of establishing such a rapid charging protocol, and a battery pack including the same.

Background Art

[0003] In recent years, with the rapid increase in the demand for portable electronic products such as notebook computers and mobile phones, and the increasing demand for electric carts, electric wheelchairs, electric bicycles, etc., research on high-performance batteries capable of repeated charging and discharging has been actively conducted. Also, recently, carbon energy has been gradually depleted, environmental awareness has increased, and the global demand for hybrid electric vehicles (HEVs) and electric vehicles (EVs) has been gradually increasing. As a result, more attention and research have been focused on vehicle batteries, which are core components of HEVs and EVs, and the development of rapid charging technology that can rapidly charge the battery has been urgently needed. In particular, the performance of rapid charging is very important in EVs that do not have an additional energy source.

[0004] The process of charging a battery includes introducing a current into the battery to accumulate charge and energy, and such a process must be carefully controlled. Generally, an excessive charging current (C-rate) or charging voltage can permanently degrade the performance of the battery, ultimately induce complete failure, or induce sudden failures such as leakage of highly corrosive chemicals or explosion.

[0005] In the constant-current charging of a battery, when the current rate of the charging current is low, a very long time is required to fully charge the battery. On the other hand, when the current rate of the charging current is excessively high, there is a side effect that the battery rapidly degrades. Therefore, it is necessary to gradually adjust the current rate of the charging current according to the state of the battery during constant-current charging.

[0006] To gradually adjust the current rate during constant-current charging, a charging map with a "multi-stage constant-current charging protocol" is mainly utilized. The charging map includes at least one data array in which the relationship between a plurality of current rates and a plurality of conversion conditions is recorded. Each time a conversion condition is met, the next sequential current rate can be supplied to the battery as the charging current. The current rate (which can also be referred to as the "C-rate") is the value obtained by dividing the charging current by the maximum capacity of the battery, and the unit "C" is used.

[0007] Conventionally, in order to derive such a multi-stage constant-current charging protocol, a three-electrode cell of the single-cell type at the 50 mAh level was fabricated, and the state of charge (SOC; state of charge; charging state, hereinafter referred to as the "state of charge") at which lithium plating occurs at the negative electrode for each charging current was determined as the charging limit.

[0008] However, since it is difficult to fabricate a three-electrode cell and it is necessary to perform charging and discharging with a dedicated charger and discharger, there are many constraints such as the degree of completion of the fabrication of the three-electrode cell, the fabrication time of the three-electrode cell, and the preparation of the dedicated charger and discharger. And in the process of applying the limited charging depth confirmed with such a three-electrode cell to a large-capacity battery cell having a capacity of 40 to 200 Ah, there was no technology to reflect the resistance of the large-capacity battery cell and the heat generation during rapid charging.

[0009] In addition, in the method for establishing a charging protocol using a three-electrode cell, as the charging current decreases and the negative electrode composition is more advantageous for rapid charging, the lithium plating section is not clearly demarcated, and the subjectivity of the experimenter intervenes. As a result, when there are deviations in the battery cell, it has been difficult to establish a charging protocol showing a similar voltage profile.

[0010] Therefore, it is not necessary to fabricate a three-electrode cell, and it is necessary to develop a technology to derive a charging protocol that can show a similar voltage profile even when there are deviations in the battery cell while considering the resistance of the large-capacity battery cell and the heat generation state during rapid charging. This is the actual situation.

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been devised to solve the above problems, and it is not necessary to fabricate a three-electrode cell in advance for deriving the limiting charging depth according to the charging current. An object is to provide a method for deriving a charging protocol considering the resistance of a large-capacity battery cell and the heat generation state during rapid charging, a battery management system capable of establishing such a charging protocol, and a battery pack equipped with the same.

Means for Solving the Problems

[0012] According to an embodiment of the present invention, a battery management system is provided. When charging a two-electrode battery cell having a positive electrode and a negative electrode with different charging currents, the battery management system measures the closed-circuit voltage (CCV x ) and the open-circuit voltage (OCV SOCx ) corresponding to the state of charge (SOC SOCx ) during charging for each charging current (I). A measurement unit configured to perform the measurement, and the measured CCV SOCx and OCV SOCx are substituted into the following formula (1) to calculate the internal resistance value (R SOCx ) corresponding to the state of charge, and the internal resistance value (R) corresponding to the state of charge for each charging current (I).SOCx A memory unit configured to collect and store an internally resistant profile obtained by plotting SOCx ; and a control unit configured to determine a limiting depth of charge corresponding to each charging current from the internally resistant profile and establish a charging protocol based thereon.

[0013] [Equation 1] Internally resistant value (R SOCx ) corresponding to depth of charge = (CCV SOCx - OCV SOCx ) / I

[0014] In an exemplary embodiment, the control unit may be configured to determine the depth of charge (SOC x ) value at a point where the graphical profile of the internally resistant profile corresponding to the depth of charge changes from flat to a downward trend as the limiting depth of charge.

[0015] In an exemplary embodiment, the control unit may be configured to periodically re-derive the limiting depth of charge corresponding to each charging current while repeatedly charging and discharging the battery cell and re-establish the charging protocol.

[0016] In an exemplary embodiment, the battery management system further includes a connection unit configured to be connected to a charging device to supply a charging current to the battery cell according to the charging protocol established by the control unit.

[0017] In an exemplary embodiment, the measuring unit is configured to measure state information of the battery cell including at least one or more of the voltage and depth of charge of the battery cell.

[0018] In an exemplary embodiment, the charging current (I) is selected from the range of 0.33C to 6.0C.

[0019] According to another embodiment of the present invention, a battery pack is provided. The battery pack includes the battery management system described above.

[0020] In an exemplary embodiment, the battery pack may include a plurality of battery cells having a capacity of 40 to 200 Ah.

[0021] According to another embodiment of the present invention, a method for establishing a charging protocol for a lithium secondary battery is provided. The method for establishing a charging protocol for the lithium secondary battery includes: (a) when charging a two-electrode battery cell including a positive electrode and a negative electrode with different charging currents, the closed-circuit voltage (CCV x ) and the open-circuit voltage (OCV SOCx ) corresponding to the state of charge (SOC SOCx ) during charging at each charging current (I) are measured respectively; (b) substituting the measured CCV SOCx and OCV SOCx into the following formula 1 to calculate the internal resistance value (R SOCx ) corresponding to the state of charge, and collecting an internal resistance profile obtained by plotting the internal resistance value (R SOCx ) corresponding to the state of charge for each charging current (I); (c) determining a limiting state of charge corresponding to each charging current from the collected internal resistance profile.

[0022] [Formula 1] Internal resistance value (R SOCx ) corresponding to the state of charge = (CCV SOCx -OCV SOCx ) / I

[0023] In an exemplary embodiment, in the above step (c), the limiting state of charge is determined as the state of charge (SOC) value at the point where the graph profile of the internal resistance profile changes from flat to a downward trend.

[0024] In an exemplary embodiment, the capacity of the two-electrode battery cell is 40 to 200 Ah.

[0025] In an exemplary embodiment, in the above process (a), the charging current (I) is selected from the range of 0.33C to 6.0C.

[0026] In an exemplary embodiment, in the above process (a), the charging current (I) is set at intervals of 0.1C to 1.0C.

[0027] The method for establishing a charging protocol according to an exemplary embodiment further includes a process of mapping the charging protocol based on the limiting charging depth for each charging current. The mapping process may charge at the charging current up to the limiting charging depth for each charging current and map such that the charging current decreases as the charging depth increases.

Advantages of the Invention

[0028] The battery management system and the method for setting a charging protocol according to the present invention have the effect of providing a charging protocol in which resistance and heat generation are immediately reflected from a large-capacity battery cell without manufacturing a three-electrode cell that is complicated to manufacture.

[0029] In addition, the battery management system and the method for setting a charging protocol according to the present invention have the effect of non-destructively grasping the degree of degradation of the battery cell even during driving of the battery cell and being able to update the charging protocol reflecting the degradation of the battery cell.

[0030] In addition, the battery management system and the method for setting a charging protocol according to the present invention can derive the limiting charging depth even at a low charging current of 1.0C level and can provide a charging protocol advantageous for rapid charging.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0032] The terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts that conform to the technical idea of the present invention based on the principle that the inventor can appropriately define the concept of the terms in order to explain his own invention in the best way.

[0033] Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, there may be various equivalents and modifications that can replace them at the time of this application.

[0034] Also, in the description of the present invention, when it is determined that a specific description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

[0035] Throughout the specification, when a part "includes" a certain component, this does not exclude other components unless otherwise stated to the contrary, meaning that it may further include other components.

[0036] Also, terms such as the control unit described in the specification mean a unit that processes at least one function or operation, which can be embodied by hardware, software, or a combination of hardware and software.

[0037] Throughout the specification, when a part is "connected" to another part, this includes not only the case of being "directly connected", but also the case of being "indirectly connected" with other elements interposed in between.

[0038] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0039] FIG. 1 is a drawing exemplarily showing the configuration of a battery pack including a battery management system according to an embodiment of the present invention. FIG. 2 is a drawing schematically showing a battery pack including a battery management system according to an embodiment of the present invention.

[0040] Referring to FIG. 1, the battery pack 1 may include a battery cell 10 and a battery management system 100. The battery management system 100 is a battery management system that monitors the voltage, current, temperature, etc. of the battery cell 10 and controls and manages to prevent overcharging, over-discharging, etc.

[0041] Here, the battery cell 10 is a two-electrode battery cell having a negative electrode and a positive electrode, meaning one physically separable independent cell. As an example, one pouch-type lithium polymer cell may be regarded as the battery cell 10. And the above battery cell 10 may be a high-capacity battery cell having a capacity in the range of 40 to 200 Ah.

[0042] In addition, the battery pack 1 can also include a battery module in which one or more battery cells 10 are connected in series and / or in parallel.

[0043] As the positive electrode active material constituting the positive electrode of the battery cell 10, a lithium-containing transition metal oxide can be used. For example, LiCoC 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li(Ni a Co b Mn c )O 2 (0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li x (Ni a Co b Mn c Al d )O 2 (0.5 < x < 1.3, 0.6 < a < 1, 0 < b < 0.2, 0 < c < 0.1, 0 < d < 0.1, a + b + c + d = 1), LiNi 1-y Co y O 2 , LiCo 1-y Mn y O 2 , LiNi 1-y Mn y O 2 (0 ≦ y < 1), Li(Ni a Co b Mn c )O 4 (0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O 4 , LiMn 2-z Co z O 4 (0 < z < 2), LiCoPO 4 , LiFePO 4 , or two or more of these. In addition to such oxides, sulfides, selenides, and halides can be mentioned.

[0044] As the negative electrode active material constituting the negative electrode, carbon-based materials such as graphite or activated carbon, or substances such as silicon oxide (SiO x ) are used.

[0045] In the case of a negative electrode active material using a carbon-based material, the potential is very low, about the same as that of Li, and lithium plating (Li-plating) that forms a metal plating film due to the characteristics of lithium ions at the negative electrode occurs due to an increase in resistance or an increase in current. Therefore, a safe charging protocol is established by a method of determining the depth of charge at which lithium plating occurs at the negative electrode as the limiting depth of charge.

[0046] In the establishment of a rapid charging protocol, the present invention derives the lithium plating point serving as a reference for setting the limiting depth of charge from an internal resistance profile in which the internal resistance values corresponding to the depth of charge of the battery cell are plotted.

[0047] Referring to FIG. 1, the battery management system 100 according to the present invention may include a measurement unit 110, a memory unit 120, and a control unit 130.

[0048] In the embodiment of FIG. 2, the battery management system 100 according to the present invention may further include a connection unit 140 configured to be connected to a charging device 200 that can supply a charging current to the battery cell according to the charging protocol established by the control unit 130.

[0049] The charging device 200 may be connected to the battery pack 1. And the charging device 200 connected to the battery pack 1 can supply a charging current to the battery cell 10 according to the charging protocol established by the control unit 130.

[0050] Then, the battery management system 100 may control the operation of the switching unit (SW) to control the charging and discharging of the battery cell 10 and / or the battery module.

[0051] The measurement unit 110 is configured to measure the state information of the battery cell including at least one of the voltage and the state of charge with respect to the battery cell 10. The measurement unit 110 according to an embodiment of the present invention calculates the internal resistance value of the battery cell 10, and the closed circuit voltage (CCV x ) corresponding to the state of charge (SOC SOCx ) and the open circuit voltage (OCV x ) corresponding to the state of charge (SOC SOCx ) are each configured to be measured. The values of the closed circuit voltage (CCV SOCx ) and the open circuit voltage (OCV SOCx ) measured by the measurement unit 110 are the basic data for calculating the internal resistance value at the state of charge (SOC x ).

[0052] The measurement unit 110 is configured to measure the closed circuit voltage (CCV SOCx ) and the open circuit voltage (OCV SOCx ) corresponding to the state of charge with different charging currents (I) for the battery cell 10. In an exemplary embodiment, the charging current (I) may be selected in a plurality within the range of 0.2C to 6C, specifically 0.33C to 6C, more specifically 0.5C to 5C. Also, the interval of the charging current (I) may be set at an interval of 0.1C to 1.0C. For example, the battery cell 10 is charged up to 100% SOC with various values of the charging current (I) set at an interval of 0.25C, such as 0.25C - 0.5C - 0.75C… - 2.75C - 3.0C. Each time the measurement unit 110 charges with each charging current (I), it is configured to measure the closed circuit voltage (CCV x ) and the open circuit voltage (OCV SOCx ) corresponding to the state of charge (SOC SOCx ), and the closed circuit voltage (CCV SOCx ) and the open circuit voltage (OCV SOCxEach measurement point of can be set at intervals of SOC 2.5%, SOC 5%, or SOC 10%.

[0053] The memory unit 120 substitutes the CCV SOCx and OCV SOCx into the following formula 1 to calculate the internal resistance value (R x ) corresponding to the state of charge (SOC SOCx ), collects the internal resistance profiles obtained by plotting the internal resistance values (R SOCx ) according to the state of charge for each charging current (I), and is configured to store them.

[0054] [Formula 1] Internal resistance value (R SOCx ) corresponding to the state of charge = (CCV SOCx - OCV SOCx ) / I

[0055] Since the difference between the closed - circuit voltage and the open - circuit voltage is caused by the voltage drop in the internal resistance, the actual internal resistance value of the battery cell can be calculated by dividing the difference between the closed - circuit voltage and the open - circuit voltage by the (rapid) charging current.

[0056] At this time, the open - circuit voltage (OCV SOCx ) can be measured within 1 second to 30 seconds, within 1 second to 15 seconds, within 1 second to 10 seconds, or within 2 seconds to 9 seconds from the measurement time point of the closed - circuit voltage (CCV SOCx ).

[0057] The control unit 130 is configured to determine the limiting state of charge corresponding to each charging current from the internal resistance profiles stored in the memory unit by charging current (I), and establish a charging protocol based on it.

[0058] The control unit 130 of the present invention can be configured to determine the state of charge (SOC x ) value at the point where the general shape of the graph in the internal resistance profile changes from flat to a downward trend as the limiting state of charge.

[0059] Figure 3 shows the closed circuit voltage (CCV x ) according to the state of charge (SOC SOCx ) and the open circuit voltage (OCV x ) according to the state of charge (SOC SOCx ) measured separately for each charging current (I) according to an embodiment of the present invention, and calculates the internal resistance value (R SOCx ). The internal resistance value (R x ) according to the state of charge (SOC SOCx ) is plotted (Plotting) to show the internal resistance profile according to the state of charge derived.

[0060] Referring to Figure 3, in the charging current (I) range of 0.5C to 3C, an internal resistance profile is shown in which the internal resistance values according to the state of charge are plotted for various values of charging current set at intervals of 0.25C.

[0061] Looking at these internal resistance profiles, a point where the general shape of the graph drops sharply from flat can be confirmed. That is, in almost all ranges of charging current (1C to 3C), it can be observed that after having a constant internal resistance value of about 1.4 mΩ, the internal resistance value starts to decrease. The point where the sharp drop in the internal resistance value starts can be regarded as the point where lithium plating occurs.

[0062] When lithium plating occurs, during the charging pause period, lithium ions are inserted into the black smoke layer of the negative electrode and at the same time are also bonded to the lithium plating part. That is, in the state of charge section before lithium plating occurs, lithium ions are inserted into the negative electrode and exist as series resistance, but in the state of charge section after lithium plating occurs, while forming a parallel resistance between the case where lithium ions are inserted into the negative electrode and the case where lithium plating occurs, the overall resistance decreases. Therefore, in the internal resistance profile according to the state of charge, the decrease in the internal resistance value becomes an indicator indicating that lithium plating has occurred.

[0063] Therefore, in the internal resistance profile according to the charging current, the control unit 130 of the present invention determines the state of charge (SOC x ) value at the point where the general shape of the graph changes from flat to decreasing as the above-mentioned limit state of charge. Then, after determining the limit state of charge corresponding to each charging current (I) as described above, the control unit 130 can establish a charging protocol based on it.

[0064] The battery management system 100 according to the present invention has an effect that the measurement unit 110, the memory unit 120, and the control unit 130 can charge the battery cell according to a charging protocol that reflects the resistance of the large-capacity battery cell 10 and the heat generation accompanying rapid charging.

[0065] On the other hand, the control unit 130 may be configured to newly derive the limit state of charge corresponding to each charging current periodically while repeating the charge and discharge of the battery cell, and re-establish the charging protocol. This is for reflecting the degradation of the battery cell due to repeated charge and discharge.

[0066] For example, every 100 cycles, when the measurement unit 110 charges the battery cell with different charging currents, the control unit 130 controls the measurement unit 110 to measure the closed-circuit voltage (CCV x ) according to the state of charge (SOC SOCx ) during charging and the open-circuit voltage (OCV x ) according to the state of charge (SOC SOCx ) respectively. The memory unit 120 substitutes the measured CCV SOCx and OCV SOCx into the following formula 1 to calculate the internal resistance value (R SOCx ) according to the state of charge, collects the internal resistance profile obtained by plotting the internal resistance values according to the state of charge for each charging current (I), controls to save it, derives a new limit state of charge corresponding to each charging current from the internal resistance profile stored in the memory unit, and establishes a new charging protocol reflecting the degradation based on it.

[0067] As a result, the battery management system according to the present invention can non-destructively grasp the degree of degradation of the battery cell even during the driving of the battery cell, and has an effect of being able to update the charging protocol reflecting the degradation of the battery cell.

[0068] FIG. 6 is a flowchart of a method for establishing a charging protocol for a lithium secondary battery according to an embodiment of the present invention.

[0069] Referring to FIG. 6, a method for establishing a charging protocol according to an embodiment of the present invention includes: (a) when charging a two-electrode battery cell having a positive electrode and a negative electrode with different charging currents, the closed-circuit voltage (CCV x ) and the open-circuit voltage (OCV SOCx ) corresponding to the state of charge (SOC SOCx ) during charging are measured for each charging current (I); (b) substituting the measured CCV SOCx and OCV SOCx into the following formula (1) to calculate the internal resistance value (R SOCx ) corresponding to the state of charge, and collecting an internal resistance profile obtained by plotting the internal resistance value (R SOCx ) corresponding to the state of charge for each charging current (I); (c) determining a limiting state of charge corresponding to each charging current from the collected internal resistance profiles.

[0070] [Formula (1)] Internal resistance value (R SOCx ) corresponding to the state of charge = (CCV SOCx -OCV SOCx ) / I

[0071] In establishing the charging protocol according to the present invention, the limiting state of charge may be a state of charge (SOC) value at a point where the general shape of the internal resistance profile changes from flat to a downward trend.

[0072] And in the above process (a), the charging current (I) can be set at regular intervals within the range of 0.2C to 6C, specifically 0.33C to 6C, and more specifically 0.5C to 5C. At this time, the interval can be 0.1C to 1.0C.

[0073] The method for establishing a charging protocol according to the prior art is to fabricate a three - electrode cell with a capacity of 50 mAh level in advance to derive the limiting charging depth, and derive the lithium plating point corresponding to the negative electrode potential as the limiting charging depth. However, in the present invention, it is not necessary to fabricate a three - electrode cell, and the limiting charging depth can be directly derived through the calculation of the internal resistance value for a large - capacity two - electrode battery cell with a capacity of 40 to 200 Ah.

[0074] The method for establishing a charging protocol according to an exemplary embodiment may further include a process of mapping the charging protocol based on the limiting charging depth for each charging current.

[0075] The above mapping process may be to charge with the charging current up to the limiting charging depth for each charging current, and map such that the charging current decreases as the charging depth increases. For example, if the limiting charging depth corresponding to a charging current of 3.0C is SOC40%, the limiting charging depth corresponding to a charging current of 2.5C is SOC45%, the limiting charging depth corresponding to a charging current of 2.0C is SOC55%, and the limiting charging depth corresponding to a charging current of 1.5C is 65%, then it can be mapped to charge with a charging current of 3.0C up to SOC40% or less, a charging current of 2.5C up to SOC45% or less, a charging current of 2.0C up to SOC55% or less, and a charging current of 1.5C up to SOC65% or less.

[0076] Hereinafter, a specific example will be given to explain in detail the battery management system and the method for establishing a charging protocol of the present invention, which derive the limiting charging depth corresponding to the charging current and establish the charging protocol according to the present invention.

[0077] <Example 1>

[0078] While charging a battery cell having a capacity of 40 Ah and an SOC of 2.5% with a charging current of 0.5C, the measuring unit measures the closed-circuit voltage (CCV SOCx ) and the open-circuit voltage (OCV SOCx ) of the battery cell at intervals of the charging depth of 2.5% SOC, respectively, and substitutes the measured values into the following formula 1 to calculate the internal resistance value at the charging depth.

[0079] [Formula 1] Internal resistance value (R SOCx ) corresponding to the charging depth = (CCV SOCx - OCV SOCx ) / I

[0080] Then, the charging depth is plotted on the x-axis, and the correspondence relationship between the internal resistance value is plotted on the y-axis, and the internal resistance profile with the internal resistance value plotted according to the charging depth as shown in FIG. 3 is stored in the memory unit.

[0081] Thereafter, the above process is repeated for each charging current of 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C, 2.75C, 3.0C, and the respective internal resistance profiles are stored in the memory unit for each charging current.

[0082] Thereafter, the control unit determines, in the internal resistance profile corresponding to the charging depth of FIG. 3 stored in the storage unit, the charging depth at the point where the general shape of the graph changes from flat to decreasing as the limit charging depth for each charging current, and shows the results in FIG. 4 and Table 1.

[0083]

Table 1

[0084] <Comparative Example 1>

[0085] Using a three - electrode cell, which is a conventional method for establishing a charging protocol, charge and discharge are performed at a temperature of 25 degrees Celsius. The limiting charging depth is derived for each charging current, and the results are shown in Table 2 and Figure 4. At this time, for the limiting charging depth, while charging is performed with charging currents set at 0.25C intervals in the range of 1.0C to 2.75C for a single - cell of 50 mAh level, the negative - electrode potential (CCV) corresponding to the charging depth (SOC) of the three - electrode cell is measured, and the charging depth at the point where the negative - electrode potential starts to become constant without decreasing is determined as the limiting charging depth.

[0086] <Comparative Example 2>

[0087] Except that the temperature was set to 35 degrees Celsius in the above Comparative Example 1, the limiting charging depth for each charging current was derived in the same manner as in the above Comparative Example 1, and the results are shown in Table 2 and Figure 4.

[0088]

Table 2

[0089] Comparing the results of Figure 4 with Table 1 and Table 2, it can be seen that the values of the limiting charging depth for each charging current according to the present invention are consistent with or similar to the values of the limiting charging depth for each charging current derived using a conventional three - electrode cell at 35 degrees Celsius. Thus, it can be confirmed that the limiting charging depth for each charging current derived by the present invention sufficiently reflects the resistance of the large - capacity battery cell and the heat generation associated with rapid charging.

[0090] <Experimental Example 1>

[0091] A battery cell (Manufacturing Example 1) used in Example 1 and a battery cell (Manufacturing Example 2) in which the composition of the negative electrode was changed to have excellent rapid - charging ability in the battery cell of the above Manufacturing Example 1 were prepared.

[0092] For each of the battery cells of Production Example 1 and Production Example 2, the limiting charge depth for each charging current is derived in the same manner as in the above Example, and a charging protocol is established. As a result, a protocol that takes 28.4 minutes for charging (First Charging Protocol) was established for the battery cell of Production Example 1, and a protocol that takes 21.7 minutes for charging (Second Charging Protocol) was established for the battery cell of Production Example 2.

[0093] The battery cell of Production Example 1 is charged according to the First Charging Protocol, the open circuit voltage corresponding to the charge depth is measured, and the results are shown in FIG. 5. The battery cell of Production Example 2 is also charged according to the Second Charging Protocol, the open circuit voltage corresponding to the charge depth is measured, and the results are shown in FIG. 5.

[0094] Referring to FIG. 5, it can be confirmed that the battery cells of Production Example 1 and Production Example 2 exhibit similar voltage profiles. Thereby, it can be seen that the method for establishing the charging protocol according to the present invention has the effect of enabling the establishment of a protocol that uses a similar charge depth for battery cells having different electrode compositions.

[0095] <Experimental Example 2>

[0096] For the battery cell that has undergone degradation after 500 charge-discharge cycles (capacity: 40 Ah), which is the same battery cell as used in the above Example 1, the internal resistance profile corresponding to the charge depth is derived under the same conditions and in the same manner, and the results are shown in FIG. 7. Then, in the internal resistance profile shown in FIG. 7, the charge depth at the point where the general shape of the graph changes from flat to decreasing is determined as the limiting charge depth for each charging current, and FIG. 8 shows a graph in which the limiting charge depth for each charging current of the battery cell that has undergone degradation is added to the graph shown in FIG. 4.

[0097] Comparing and explaining FIGS. 7 and 3, the internal resistance value of an aged cell that has undergone degradation by repeating charge and discharge 500 times increases from about 1.4 mΩ to about 1.6 mΩ compared to a BOL (Begin of life) battery cell (Example 1) that does not repeat charge and discharge. This is considered to be the result of reflecting the degradation due to the repetition of charge and discharge cycles. And it can be confirmed that the increase rate of the internal resistance value differs depending on the charging current. Also, in FIG. 7, it can be seen that the x-axis coordinate (SOC) at the point where the general shape of the graph starts to decline from flat has moved to the left compared to the x-axis coordinate at the point where the general shape of the graph starts to decline from flat in FIG. 3. It can be seen that the limiting charge depth for each charging current decreases in a cell with advanced degradation.

[0098] Therefore, it is expected that the method for establishing a charging protocol of the present invention and the battery management system according to the present invention have the effect of being able to update a new charging protocol reflecting the degradation during the driving of a battery cell.

[0099] <Example 2>

[0100] A battery cell (capacity: 40 Ah) having the same specifications as the battery cell used in Example 1 above is connected to an electrochemical charger. Based on the limiting charge depth for each charging current described in Table 1 of Example 1 above, the charging protocol is mapped as shown in Table 3 below. After fully charging the battery cell to SOC 100% according to the mapped charging protocol, the fully charged battery cell is fully discharged to SOC 0% at a constant current of 0.33C.

[0101]

Table 3

[0102] <Comparative Example 3>

[0103] A battery cell (capacity: 40 Ah) having the same specifications as the battery cell used in Example 1 above was connected to an electrochemical charger. After being fully charged to SOC 100% at a constant current of 0.33C, the battery cell fully charged at a constant current of 0.33C was fully discharged to SOC 0%.

[0104] <Experimental Example 2: Measurement of Charge and Discharge Time>

[0105] The time taken for charging was measured for each case of charging according to the method of Example 2 and charging according to the method of Comparative Example 3, and the results are shown in Table 4.

[0106] <Experimental Example 3: Evaluation of Capacity Retention Rate>

[0107] After charging and discharging according to each method of Example 2 and Comparative Example 3 and repeating the charge and discharge 200 times, the capacity retention rate calculated according to the following formula 1 is shown in Table 4.

[0108] Formula 1: (Discharge capacity at 200 cycles × 100) / Discharge capacity at the first cycle

[0109]

Table 4

[0110] Referring to Table 4, when charging according to the charging protocol according to Example 2, the time taken for charging was significantly reduced compared to the case of charging and discharging according to the charging method according to Comparative Example 3. Also, when charging according to the charging protocol according to Example 2, the capacity retention rate is at the same level as the case of charging and discharging according to the charging method according to Comparative Example 3, but it can be confirmed that the charging protocol derived according to the present invention does not cause capacity degradation of the battery cell.

Explanation of Reference Signs

[0111] 1: Battery pack 10: Battery cell 100: Battery management system 110: Measurement unit 120: Memory unit 130: Control unit 200: Charging device

Claims

1. When charging a two - electrode battery cell having a positive electrode and a negative electrode with different charging currents, the depth of charge (SOC ｘ ), the closed - circuit voltage (CCV ＳＯＣｘ ), and the open - circuit voltage (OCV ＳＯＣｘ ) corresponding to the depth of charge during charging at each charging current (I) are measured, and a measurement unit configured to measure them. the measured CCV ＳＯＣｘ and the OCV ＳＯＣｘ are substituted into the following formula 1 to calculate the internal resistance value (R ＳＯＣｘ ) according to the depth of charge, and the internal resistance profiles plotting the internal resistance values (R ＳＯＣｘ ) according to the depth of charge for each charging current (I) are collected and stored in a memory unit configured to do so. A battery management system comprising: a control unit configured to determine a limiting charge depth corresponding to each charging current from the internal resistance profile and establish a charging protocol based on the limiting charge depth. [Equation 1] Internal resistance value (R) according to state of charge ＳＯＣｘ = (CCV ＳＯＣｘ - OCV ＳＯＣｘ ) / I

2. The control unit is configured to determine the state of charge (SOC) value at a point where the graph profile of the internal resistance profile changes from flat to a downward trend as the limiting state of charge. ｘ The battery management system according to claim 1, wherein the battery management system is configured to determine the state of charge (SOC) value at a point where the graph profile of the internal resistance profile changes from flat to a downward trend as the limiting state of charge.

3. The battery management system according to claim 1 or 2, wherein the control unit is configured to newly derive a limiting charge depth corresponding to each charging current periodically while repeating charging and discharging of the two-electrode battery cell and re-establish a charging protocol.

4. The battery management system according to claim 1, further comprising a connection unit configured to be connected to a charging device to supply a charging current to the two-electrode battery cell according to the charging protocol established by the control unit.

5. The battery management system according to claim 1, wherein the measuring unit is configured to measure state information of the battery cell including at least one of the voltage and the charge depth of the two-electrode battery cell.

6. The battery management system according to claim 1, wherein the charging current (I) is selected from the range of 0.33C to 6.0C.

7. A battery pack including the battery management system according to claim 1.

8. The battery pack according to claim 7, including a plurality of two-electrode battery cells having a capacity of 40 to 200 Ah.

9. When charging a two - electrode battery cell having a positive electrode and a negative electrode with different charging currents, the depth of charge (SOC ｘ ), the closed - circuit voltage (CCV ＳＯＣｘ ), and the open - circuit voltage (OCV ＳＯＣｘ ) corresponding to the depth of charge during charging at each charging current (I) are measured, and (b) Substitute the measured CCV into the following formula 1 ＳＯＣｘ and OCV ＳＯＣｘ to calculate the internal resistance value (R ＳＯＣｘ ) corresponding to the state of charge, and collect the internal resistance profiles obtained by plotting the internal resistance values (R ＳＯＣｘ ) corresponding to the state of charge for each charging current (I); A method for establishing a charging protocol for a lithium secondary battery, comprising: (c) a process of determining a limiting charge depth corresponding to each charging current from the collected internal resistance profile. [Equation 1] Internal resistance value (R) according to state of charge ＳＯＣｘ ) = (CCV ＳＯＣｘ - OCV ＳＯＣｘ ) / I

10. The method for establishing a charging protocol for a lithium secondary battery according to claim 9, wherein in the process (c), the limiting charge depth is determined as a charge depth (SOC) value at a point where the graph profile of the internal resistance profile changes from flat to a downward trend.

11. The method for establishing a charging protocol for a lithium secondary battery according to claim 9 or 10, wherein the capacity of the two-electrode battery cell is 40 to 200 Ah.

12. The method for establishing a charging protocol for a lithium secondary battery according to claim 9, wherein in the process (a), the charging current (I) is selected from the range of 0.33C to 6.0C.

13. The method for establishing a charging protocol for a lithium secondary battery according to claim 12, wherein in the process (a), the charging current (I) is set at intervals of 0.1 C to 1.0 C.

14. further comprising a process of mapping a charging protocol based on the limiting charging depth for each charging current, The method for establishing a charging protocol for a lithium secondary battery according to claim 9, wherein the process of mapping includes a process of charging with the charging current up to the limiting charging depth for each charging current and mapping the charging protocol such that the charging current decreases as the charging depth increases.

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