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

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 the heat generation and internal resistance associated with charging and discharging of large-capacity battery cells, a battery management system capable of establishing such a rapid charging protocol, and a battery pack including the same. [Background technology]

[0003] In recent years, with the rapid increase in demand for portable electronic products such as laptops and mobile phones, as well as the growing demand for electric carts, electric wheelchairs, and electric bicycles, research into high-performance batteries that can be repeatedly charged and discharged is being actively conducted. Furthermore, with the gradual depletion of carbon energy and growing concern for the environment, demand for hybrid electric vehicles (HEVs) and electric vehicles (EVs) is gradually increasing worldwide. As a result, much attention and research is being focused on vehicle batteries, a core component of HEVs and EVs, and there is an urgent need to develop fast-charging technology that can rapidly charge batteries. Fast-charging performance is particularly important for EVs, which do not have an additional energy source.

[0004] The process of charging a battery involves applying current to the battery to store charge and energy, and such a process must be carefully controlled. In general, excessive charging current (C-rate) or charging voltage can permanently degrade battery performance, ultimately leading to complete failure, or catastrophic failure such as leakage of highly corrosive chemicals or explosion.

[0005] In constant current charging of a battery, if the charging current rate is small, it takes a very long time to fully charge the battery. On the other hand, if the charging current rate is too high, it can have the side effect of rapidly degrading the battery. Therefore, it is necessary to gradually adjust the charging current rate according to the battery condition 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 that records the relationship between multiple current rates and multiple transition conditions. Each time a transition condition is satisfied, the next sequential current rate can be supplied to the battery as the charging current. The current rate (which may also be referred to as "C-rate") is the value obtained by dividing the charging current by the maximum capacity of the battery, and is expressed in units of "C."

[0007] Previously, to derive such a multi-stage constant current charging protocol, a 50mAh mono-cell type three-electrode cell was manufactured and the charging limit was determined by the state of charge (SOC) at which lithium plating occurs at the negative electrode depending on the charging current.

[0008] However, three-electrode cells are difficult to manufacture and require a dedicated charger / discharger for charging and discharging, which means there are many constraints, such as the degree of completion of the three-electrode cell manufacturing, the time required to manufacture the three-electrode cell, and the preparation of the dedicated charger / discharger. Furthermore, in the process of applying the limit depth of charge confirmed with such three-electrode cells to large-capacity battery cells with capacities of 40 to 200 Ah, there was no technology that could reflect the resistance of large-capacity battery cells or heat generation during fast charging.

[0009] Furthermore, when establishing a charging protocol using a three-electrode cell, the lithium plating zone becomes less clearly defined as the charging current decreases and the negative electrode composition becomes more favorable for fast charging, and the experimenter's subjectivity becomes an issue. This makes it difficult to establish a charging protocol that shows a similar voltage profile when there is a deviation in the battery cell.

[0010] Therefore, there is a need to develop technology to derive a charging protocol that does not require the fabrication of three-electrode cells, and that can show a similar voltage profile even when there is a deviation in the battery cells, while taking into account the resistance of large-capacity battery cells and the heat generation state during fast charging. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been devised to solve the above problems, and aims to provide a method for deriving a charging protocol that takes into account the resistance of large-capacity battery cells and the heat generation state during fast charging, without the need to previously fabricate three-electrode cells to derive the limit depth of charge for each charging current, as well as a battery management system that can establish such a charging protocol and a battery pack equipped with the same. [Means for solving the problem]

[0012] According to one embodiment of the present invention, a battery management system is provided, which is configured to calculate a state of charge (SOC) during charging at each charging current (I) when charging a two-electrode battery cell having a positive electrode and a negative electrode with different charging currents. x ) according to the closed circuit voltage (CCV SOCx ) and open circuit voltage (OCV SOCx ) and a measuring unit configured to measure the measured CCV. SOCx and OCV SOCx Substituting this into the following formula 1, the internal resistance value (R SOCx ) and calculate the internal resistance (RSOCx a memory unit configured to collect and store an internal resistance profile obtained by plotting the internal resistance of the battery and the charge current; and a control unit configured to determine a limiting depth of charge corresponding to each charging current from the internal resistance profile and establish a charging protocol based thereon.

[0013] [Formula 1] The internal resistance (R SOCx )=(CCV SOCx -OCV SOCx ) / I

[0014] In an exemplary embodiment, the control unit may determine a state of charge (SOC) at which a graph of the internal resistance profile according to the state of charge changes from a flat to a downward trend. x ) value as the limiting depth of charge.

[0015] In an exemplary embodiment, the control unit may be configured to periodically derive a new limiting state 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 coupling unit configured to couple with a charging device to supply a charging current to the battery cells according to a charging protocol established by the control unit.

[0017] In an exemplary embodiment, the measurement unit is configured to measure state information of the battery cell, including at least one of a voltage and a charge depth 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, there is provided a battery pack, the battery pack including the battery management system described above.

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

[0021] According to another embodiment of the present invention, there is provided a method for establishing a charging protocol for a lithium secondary battery, which comprises: (a) determining the state of charge (SOC) at each charging current (I) when a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents; x ) according to the closed circuit voltage (CCV SOCx ) and open circuit voltage (OCV SOCx ) and the process of measuring (b) The CCV measured above is calculated using the following formula 1: SOCx and OCV SOCx Substituting the internal resistance value (R SOCx ) and calculate the internal resistance (R SOCx ) and collecting an internal resistance profile by plotting the (c) determining the limit depth of charge corresponding to each charging current from the collected internal resistance profile.

[0022] [Formula 1] The internal resistance (R SOCx )=(CCV SOCx -OCV SOCx ) / I

[0023] In an exemplary embodiment, in the step (c), the limit state of charge is determined as a state of charge (SOC) value at which the graph outline of the internal resistance profile changes from a 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 step (a), the charging current (I) is selected from the range of 0.33C to 6.0C.

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

[0027] The method for establishing a charging protocol according to an exemplary embodiment may further include a step of mapping a charging protocol based on a limiting depth of charge for each charging current, and the mapping step may map the charging protocol so that charging is performed at the corresponding charging current until the limiting depth of charge is reached for each charging current, and the charging current decreases as the depth of charge increases. [Effects 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 that immediately reflects the resistance and heat generated from a large-capacity battery cell without manufacturing a three-electrode cell, which is complicated to manufacture.

[0029] In addition, the battery management system and charging protocol setting method according to the present invention have the advantage of being able to non-destructively grasp the degree of deterioration of the battery cells even while the battery cells are in operation, and to update the charging protocol to reflect the deterioration of the battery cells.

[0030] Furthermore, the battery management system and the method for setting a charging protocol according to the present invention can derive the limiting depth of charge even with a low charging current of the 1.0 C level, and can provide a charging protocol that is advantageous for fast charging. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a diagram illustrating an example configuration of a battery pack including a battery management system according to an embodiment of the present invention. [Figure 2] 1 is a diagram schematically illustrating a battery pack including a battery management system according to an embodiment of the present invention. [Figure 3] 1 is a profile of internal resistance as a function of charging current (I) collected according to an embodiment of the present invention. [Figure 4] 1 is a graph showing the limiting depth of charge for each charging current derived by the present invention and a conventional method for establishing a charging protocol. [Figure 5] 1 shows the SOC-OCV profiles of battery cells charged using charging protocols established by the present invention and conventional methods. [Figure 6] 1 is a flowchart of a method for establishing a charging protocol for a lithium secondary battery according to an embodiment of the present invention. [Figure 7] 1 is a diagram showing internal resistance profiles for various charging currents (I) collected according to an embodiment of the present invention for a degraded battery cell that has been charged and discharged 500 times. [Figure 8] 8 is a graph showing the limit state of charge according to the charging current (I) of FIG. 4 and the limit state of charge according to the charging current (I) of the degraded battery cell of FIG. 7; DETAILED DESCRIPTION OF THE INVENTION

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

[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 the entire technical idea of ​​the present invention, and there may be various equivalents and modifications that can replace them at the time of this application.

[0034] Furthermore, in the description of the present invention, if it is determined that a detailed description of related publicly known structures or functions may obscure the gist of the present invention, the detailed description will be omitted.

[0035] Throughout the specification, when a part is said to "comprise" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless specifically stated to the contrary.

[0036] Furthermore, the term "controller" or the like used in the specification means a unit that processes at least one function or operation, and this may be embodied in hardware, software, or a combination of hardware and software.

[0037] Furthermore, throughout this specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with another element in between.

[0038] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] 1 is a diagram illustrating an example of a configuration of a battery pack including a battery management system according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a battery pack including a battery management system according to an embodiment of the present invention.

[0040] 1, a battery pack 1 may include battery cells 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 cells 10 and controls and manages them to prevent overcharging, over-discharging, etc.

[0041] Here, the battery cell 10 refers to a two-electrode battery cell having a negative electrode and a positive electrode, and is a physically separable independent cell. As an example, a pouch-type lithium polymer cell can be considered as the battery cell 10. The battery cell 10 can be a large-capacity battery cell having a capacity of 40 to 200 Ah.

[0042] In addition, the battery pack 1 may 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, LiCoC2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni a Co b Mn c )O2 (0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li x (Ni a Co b Mn c Al d )O2 (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 O2, LiCo 1-y Mn y O2, LiNi 1-y Mn y O2 (0 ≤ y < 1), Li(Ni a Co b Mn c )O4 (0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O4, LiMn 2-z Co z O4 (0 < z < 2), LiCoPO4, LiFePO4, or two or more of these may be used. In addition to such oxides, sulfides, selenides, and halides can be mentioned.

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

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

[0046] In the present invention, in establishing a fast charging protocol, the lithium plating point, which is the standard for setting the limit depth of charge, is derived from an internal resistance profile obtained by plotting the internal resistance value according to the depth of charge of the battery cell.

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

[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 cells according to a charging protocol established by the control unit 130.

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

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

[0051] The measurement unit 110 is configured to measure state information of the battery cell 10, which includes at least one of the voltage and the state of charge of the battery cell 10. The measurement unit 110 according to the embodiment of the present invention measures the state of charge (SOC) in order to calculate the internal resistance value of the battery cell 10.x ) according to the closed circuit voltage (CCV SOCx ) and Depth of Charge (SOC x ) according to the open circuit voltage (OCV SOCx ) measured by the measurement unit 110. SOCx ) and open circuit voltage (OCV SOCx The value of the SOC x ) is the basic data for calculating the internal resistance value.

[0052] The measurement unit 110 measures the closed circuit voltage (CCV) corresponding to the charging depth by varying the charging current (I) for the battery cell 10. SOCx ) and open circuit voltage (OCV SOCx ) are measured. In an exemplary embodiment, the charging current (I) may be selected from a plurality of values ​​within a range of 0.2C to 6C, specifically 0.33C to 6C, and more specifically 0.5C to 5C. The intervals of the charging current (I) may be set at intervals of 0.1C to 1.0C. For example, the battery cell 10 is charged to SOC 100% at various values ​​of charging current (I) set at intervals of 0.25C, such as 0.25C-0.5C-0.75C...-2.75C-3.0C, and the measuring unit 110 measures the state of charge (SOC) at each charging current (I). x ) according to the closed circuit voltage (CCV SOCx ) and open circuit voltage (OCV SOCx ) and is configured to measure the closed circuit voltage (CCV SOCx ) and open circuit voltage (OCV SOCx ) measurement points can be set at intervals of SOC 2.5%, SOC 5%, or SOC 10%.

[0053] The memory unit 120 stores the CCV measured by the measurement unit 110. SOCx and OCV SOCx Substitute this into the following formula 1 to obtain the depth of charge (SOC x ) according to the internal resistance (R SOCx ) and calculate the internal resistance (R SOCx) and collects and stores the internal resistance profile.

[0054] [Formula 1] The internal resistance (R SOCx )=(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 across 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 (fast) charging current.

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

[0057] The control unit 130 is configured to determine a limit state of charge corresponding to each charging current from the internal resistance profile for each charging current (I) stored in the memory unit, and establish a charging protocol based thereon.

[0058] The control unit 130 of the present invention determines the state of charge (SOC) at which the shape of the graph in the internal resistance profile changes from a flat to a downward trend. x ) value as the limiting depth of charge.

[0059] FIG. 3 shows the state of charge (SOC) for each charging current (I) according to an embodiment of the present invention. x ) according to the closed circuit voltage (CCV SOCx ) and Depth of Charge (SOC x ) according to the open circuit voltage (OCV SOCx ) and measure the internal resistance (R SOCx ) and calculate the depth of charge (SOC x ) according to the internal resistance (R SOCx) is plotted to show the internal resistance profile according to the depth of charge.

[0060] Referring to FIG. 3, an internal resistance profile is shown, which plots internal resistance values ​​according to the depth of charge for various charging currents (I) set at intervals of 0.25C in the range of 0.5C to 3C.

[0061] Looking at these internal resistance profiles, it is possible to identify a point where the graph goes from flat to a steep drop. That is, it can be observed that the internal resistance has a constant value of about 1.4 mΩ over almost the entire range of charging current (1 C to 3 C), and then the internal resistance starts to decrease. The point where the internal resistance starts to drop sharply can be considered the point where lithium plating occurs.

[0062] When lithium plating occurs, lithium ions are inserted into the black smoke layer of the negative electrode during the rest period of charging, and simultaneously bond to the lithium plating portion. That is, in the depth of charge section before lithium plating occurs, lithium ions are inserted into the negative electrode and exist as a series resistance. However, in the depth of charge section after lithium plating occurs, the total resistance decreases as a result of the parallel resistance between the lithium ions being inserted into the negative electrode and the lithium plating. Therefore, in the internal resistance profile according to the depth of charge, a decrease in internal resistance is an indicator of the occurrence of lithium plating.

[0063] Therefore, the control unit 130 of the present invention determines the state of charge (SOC) at which the graph changes from a flat to a downward trend in the internal resistance profile for each charging current. x After determining the limit SOC corresponding to each charging current (I) as described above, the control unit 130 can establish a charging protocol based on the limit SOC.

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

[0065] Meanwhile, the control unit 130 may be configured to periodically derive a new limit state of charge corresponding to each charging current while repeatedly charging and discharging the battery cell, and re-establish the charging protocol, in order to reflect deterioration of the battery cell due to repeated charging and discharging.

[0066] For example, when the measurement unit 110 charges the battery cell with different charging currents every 100 cycles, the control unit 130 measures the state of charge (SOC) at each charging current (I). x ) according to the closed circuit voltage (CCV SOCx ) and Depth of Charge (SOC x ) according to the open circuit voltage (OCV SOCx ) and the memory unit 120 calculates the measured CCV in the following formula 1. SOCx and OCV SOCx Substituting the internal resistance value (R SOCx ) is calculated, and an internal resistance profile is collected by plotting the internal resistance value according to the depth of charge for each charging current (I), and the system is controlled to store this.A new limiting depth of charge corresponding to each charging current is derived from the internal resistance profile stored in the memory unit, and a new charging protocol that reflects degradation is established based on this.

[0067] As a result, the battery management system according to the present invention has the advantage of being able to non-destructively determine the degree of deterioration of the battery cells even while the battery cells are in operation, and to update the charging protocol to reflect the deterioration of the battery cells.

[0068] FIG. 6 is a flowchart of a method for establishing a charging protocol for a lithium secondary battery according to one 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) determining the state of charge (SOC) at each charging current (I) when a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents; x ) according to the closed circuit voltage (CCV SOCx ) and open circuit voltage (OCV SOCx ) and the process of measuring (b) The CCV measured above is calculated using the following formula 1: SOCx and OCV SOCx Substituting the internal resistance value (R SOCx ) and calculate the internal resistance (R SOCx ) and collecting an internal resistance profile by plotting the (c) determining the limit depth of charge corresponding to each charging current from the collected internal resistance profile.

[0070] [Formula 1] The internal resistance (R SOCx )=(CCV SOCx -OCV SOCx ) / I

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

[0072] In the step (a), the charging current (I) may be set at regular intervals within a range of 0.2 C to 6 C, specifically 0.33 C to 6 C, and more specifically 0.5 C to 5 C. In this case, the intervals may be 0.1 C to 1.0 C.

[0073] In the conventional method for establishing a charging protocol, a three-electrode cell with a capacity of 50 mAh was fabricated in advance to derive the limiting depth of charge, and the lithium plating point corresponding to the negative electrode potential was derived as the limiting depth of charge. However, the present invention does not require fabricating a three-electrode cell, and can directly derive the limiting depth of charge for a large-capacity two-electrode battery cell with a capacity of 40 to 200 Ah by calculating the internal resistance value.

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

[0075] The mapping process may be performed by mapping each charging current so that charging is performed at the corresponding charging current until the SOC reaches a limit, and the charging current decreases as the SOC increases. For example, if the SOC limit corresponding to a 3.0C charging current is SOC 40%, the SOC limit corresponding to a 2.5C charging current is SOC 45%, the SOC limit corresponding to a 2.0C charging current is SOC 55%, and the SOC limit corresponding to a 1.5C charging current is SOC 65%, the mapping may be performed so that charging is performed at a 3.0C charging current until the SOC reaches 40%, at a 2.5C charging current until the SOC reaches 45%, at a 2.0C charging current until the SOC reaches 55%, and at a 1.5C charging current until the SOC reaches 65%.

[0076] Hereinafter, the battery management system and the method for establishing a charging protocol according to the present invention for deriving a limit state of charge corresponding to a charging current and establishing a charging protocol will be described in detail with specific examples.

[0077] Example 1

[0078] While charging a battery cell with a capacity of 40Ah and SOC 2.5% at a charging current of 0.5C, the measurement unit measures the closed circuit voltage (CCV) of the battery cell at charging depth intervals of SOC 2.5%. SOCx ) and open circuit voltage (OCV SOCx) are measured, and the measured values ​​are substituted into the following formula 1 to calculate the internal resistance value at that state of charge.

[0079] [Formula 1] The internal resistance (R SOCx )=(CCV SOCx -OCV SOCx ) / I

[0080] Then, the charge depth is plotted on the x-axis and the corresponding relationship between the internal resistance value on the y-axis, and an internal resistance profile plotting the internal resistance value according to the charge depth as shown in Figure 3 is saved in the memory unit.

[0081] Then, 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, and 3.0C, and the internal resistance profile for each charging current is stored in the memory unit.

[0082] Then, the control unit determines the SOC at the point where the shape of the graph changes from flat to a downward trend in the internal resistance profile according to the SOC of FIG. 3 stored in the storage unit as the limit SOC for each charging current, and the results are shown in FIG. 4 and Table 1.

[0083] [Table 1]

[0084] <Comparative Example 1>

[0085] Using a three-electrode cell, which is the conventional method for establishing a charging protocol, charging and discharging were performed at a temperature of 25°C, and the limiting depth of charge (SOC) was calculated for each charging current. The results are shown in Table 2 and Figure 4. The limiting depth of charge was determined by measuring the negative electrode potential (CCV) according to the SOC (state of charge) of the three-electrode cell while charging a 50mAh mono cell at a charging current set in 0.25C increments in the range of 1.0C to 2.75C. The SOC at which the negative electrode potential begins to stabilize without decreasing was determined as the limiting SOC.

[0086] <Comparative Example 2>

[0087] The limit state of charge for each charging current was calculated in the same manner as in Comparative Example 1, except that the temperature was set to 35° C. The results are shown in Table 2 and FIG.

[0088] [Table 2]

[0089] Comparing the results of Tables 1 and 2 with those of Figure 4, it can be seen that the values ​​of the limit state of charge (SOC) for each charging current according to the present invention are consistent with or similar to the values ​​of the limit state of charge for each charging current derived using a conventional three-electrode cell at 35°C. This confirms that the limit state of charge for each charging current derived according to the present invention adequately reflects the resistance of the large-capacity battery cell and the heat generated during fast charging.

[0090] <Experimental Example 1>

[0091] The battery cell used in Example 1 (Production Example 1) and a battery cell (Production Example 2) in which the composition of the negative electrode in the battery cell of Production Example 1 was changed to improve rapid charging capability were prepared.

[0092] The limiting depth of charge for each charging current was derived and a charging protocol was established for each of the battery cells of Manufacturing Example 1 and Manufacturing Example 2 in the same manner as in the above examples. As a result, a charging protocol (first charging protocol) that takes 28.4 minutes for charging was established for the battery cell of Manufacturing Example 1, and a charging protocol (second charging protocol) that takes 21.7 minutes for charging was established for the battery cell of Manufacturing Example 2.

[0093] The battery cell of Manufacturing Example 1 was charged according to the first charging protocol, and the open circuit voltage was measured according to the depth of charge, and the results are shown in Figure 5. The battery cell of Manufacturing Example 2 was also charged according to the second charging protocol, and the open circuit voltage was measured according to the depth of charge, and the results are shown in Figure 5.

[0094] 5, it can be seen that the battery cell of Manufacturing Example 1 and the battery cell of Manufacturing Example 2 exhibit similar voltage profiles. This demonstrates that the method for establishing a charging protocol according to the present invention is effective in enabling the establishment of protocols that use similar depths of charge for battery cells with different electrode compositions.

[0095] <Experimental Example 2>

[0096] The same battery cell as used in Example 1 was subjected to 500 charge / discharge cycles to obtain an internal resistance profile according to the depth of charge (SOC) for a degraded battery cell (capacity: 40 Ah) under the same conditions and by the same method, and the results are shown in Figure 7. In the internal resistance profile shown in Figure 7, the SOC at which the graph changes from flat to a decreasing shape was determined as the limiting SOC for each charging current, and Figure 8 shows a graph in which the limiting SOC for each charging current of the degraded battery cell was added to the graph shown in Figure 4.

[0097] Comparing FIG. 7 and FIG. 3, the internal resistance of the battery cell (aged cell) that has degraded after 500 charge / discharge cycles increases from approximately 1.4 mΩ to approximately 1.6 mΩ compared to the BOL (Begin of Life) battery cell (Example 1) that has not been charged / discharged. This is thought to be a reflection of degradation due to repeated charge / discharge cycles. It can also be seen that the rate of increase in internal resistance differs depending on the charging current. Furthermore, in FIG. 7, the x-axis coordinate (SOC) at which the graph begins to flatten and then decline is shifted to the left of the x-axis coordinate at which the graph begins to flatten and then decline in FIG. 3. It can also be seen that the critical depth of charge (SOC) for degraded cells decreases depending on the charging current.

[0098] Therefore, the method for establishing a charging protocol of the present invention and the battery management system of the present invention are expected to be effective in enabling updating of a new charging protocol that reflects the degradation of battery cells during operation.

[0099] <Example 2>

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

[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 was connected to an electrochemical charger / discharger and fully charged to 100% SOC at a constant current of 0.33 C. The fully charged battery cell was then fully discharged to 0% SOC at a constant current of 0.33 C.

[0104] <Experimental Example 2: Measurement of charge / discharge time>

[0105] The time required for charging was measured for each of the cases where charging was performed according to the method of Example 2 and the method of Comparative Example 3. The results are shown in Table 4.

[0106] <Experimental Example 3: Evaluation of capacity retention rate>

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

[0108] Equation 1: (discharge capacity at 200 cycles x 100) / discharge capacity at first cycle

[0109] [Table 4]

[0110] Referring to Table 4, when charging according to the charging protocol of Example 2, the time required for charging was significantly reduced compared to when charging and discharging according to the charging method of Comparative Example 3. Furthermore, when charging according to the charging protocol of Example 2, the capacity retention rate was at the same level as when charging and discharging according to the charging method of Comparative Example 3, and 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 symbols]

[0111] 1: Battery pack 10: Battery cell 100: Battery Management System 110: Measuring part 120: Memory section 130: Control unit 200: Charging device

Claims

1. When a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents, the state of charge (SOC) during charging at each charging current (I) is ｘ ) according to the closed circuit voltage (CCV ＳＯＣｘ ) and open circuit voltage (OCV ＳＯＣｘ a measuring unit configured to measure the The measured CCV ＳＯＣｘ and OCV ＳＯＣｘ is substituted into the following formula 1 to obtain the internal resistance value (R ＳＯＣｘ ) and calculate the internal resistance value (R ＳＯＣｘ a memory unit configured to collect and store an internal resistance profile plotted from the measured resistance value; a controller configured to determine a limiting depth of charge corresponding to each charging current from the internal resistance profile, and to establish a charging protocol based on the limiting depth of charge. [Formula 1] Internal resistance value according to the charging depth (R ＳＯＣｘ ) = (CCV ＳＯＣｘ -OCV ＳＯＣｘ ) / I

2. The control unit determines the state of charge (SOC) at which the graph shape of the internal resistance profile changes from a flat to a downward trend. ｘ 2. The battery management system of claim 1, configured to determine a value of .times. ...

3. 3. The battery management system according to claim 1, wherein the control unit is configured to periodically derive a new limit state of charge corresponding to each charging current while repeatedly charging and discharging the two-electrode battery cell, and reestablish a charging protocol.

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

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

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

7. A battery pack comprising the battery management system of claim 1.

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

9. (a) When a two-electrode battery cell having a positive electrode and a negative electrode is charged with different charging currents, the state of charge (SOC) during charging at each charging current (I) is ｘ ) according to the closed circuit voltage (CCV ＳＯＣｘ ) and open circuit voltage (OCV ＳＯＣｘ ) and (b) The measured CCV is calculated by the following formula 1: ＳＯＣｘ and OCV ＳＯＣｘ Substituting the internal resistance value (R ＳＯＣｘ ) and calculate the internal resistance value (R ＳＯＣｘ collecting an internal resistance profile by plotting the (c) determining a limiting depth of charge corresponding to each charging current from the collected internal resistance profiles. [Formula 1] Internal resistance value according to the charging depth (R ＳＯＣｘ ) = (CCV ＳＯＣｘ -OCV ＳＯＣｘ ) / I

10. 10. The method for establishing a charging protocol for a lithium secondary battery according to claim 9, wherein in step (c), the limiting depth of charge is determined as a depth of charge (SOC) value at a point where a graph outline of the internal resistance profile changes from a 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. 10. The method for establishing a charging protocol for a lithium secondary battery according to claim 9, wherein in the step (a), the charging current (I) is selected from the range of 0.33 C to 6.0 C.

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

14. The method further includes mapping a charging protocol based on a limiting depth of charge for each charging current; 10. The method of claim 9, wherein the mapping step includes mapping the charging protocol such that charging is performed at a corresponding charging current until the charging current reaches a limiting depth of charge or less, and the charging current decreases as the depth of charge increases.

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