Apparatus and method for estimating performance of a rechargeable battery

Abstract

The present invention relates to an apparatus and method for predicting the performance of a secondary battery based on its electrode structure. The apparatus for predicting the performance of a secondary battery according to the present invention includes: a communication unit for receiving a cumulative pore volume value from a device for measuring the volume of pores formed in a positive electrode, the cumulative pore volume value being a value obtained by summing the volumes of all pores in the positive electrode per unit area; and a processor for predicting the output performance of the secondary battery by comparing the cumulative pore volume value with a volume reference value, wherein the volume reference value is a cumulative pore volume value corresponding to an expected output value required for the secondary battery when the secondary battery is continuously discharged.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0126849 filed in the Korean Intellectual Property Office on September 29, 2020, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to an apparatus and method for estimating performance of a rechargeable battery based on an electrode structure. Background Art

[0004] As the demand for lithium rechargeable batteries shifts from small portable electronic devices to medium and large electric vehicles (EVs) and energy storage systems (ESS), the required battery characteristics are also changing significantly. In addition to significantly enhanced requirements compared to existing small batteries, such as long-term reliability exceeding 10 years, pack-level safety, and price competitiveness, high power characteristics and fast charging performance are also required.

[0005] Recently, attempts have been made to improve output by increasing the moving speed of electrons or increasing the moving speed of ions. For example, attempts have been made to change the structure of the electrodes of rechargeable batteries to increase the ion (Li + There have been various attempts to improve the movement speed of ions. Consequently, what is needed is a method for measuring or estimating how much the movement speed of ions is improved by changing the electrode structure, etc., and thereby determining how much the output of the rechargeable battery is improved.

[0006] However, measuring the output of a rechargeable battery is much more difficult than measuring the capacity of a conventional battery cell because both voltage and current must be measured and controlled simultaneously. Furthermore, this has been pointed out as a problem because, in addition to the method used to measure the output of a rechargeable battery, the measured value often varies significantly depending on measurement conditions such as output hold time, state of charge (SOC), cutoff conditions, and measurement temperature.

[0007] Therefore, there is a need for a method that can easily and accurately estimate how much the output performance or rapid charging performance of a rechargeable battery has improved due to an increase in the movement speed of ions depending on changes in electrode structure and the like. Summary of the Invention

[0008] Technical issues

[0009] The present invention provides an apparatus and method for estimating rechargeable battery performance according to an electrode structure for estimating rechargeable battery performance by comparing a cumulative intrusion value of an electrode with a volume reference value based on relevant cumulative intrusion, tortuosity, polarization resistance (Rpola), and battery performance.

[0010] The present invention provides an apparatus and method for estimating rechargeable battery performance according to an electrode structure for estimating rechargeable battery performance based on a cumulative intrusion value of pores having a diameter greater than or equal to 0.1 micrometer and less than or equal to 1 micrometer.

[0011] Technical Solution

[0012] An apparatus for estimating the performance of a rechargeable battery according to the present invention includes: a communication unit that receives a cumulative intrusion value from an apparatus for measuring the volume of pores formed in a positive electrode, the cumulative intrusion value being a summed value of the volumes of all pores of the positive electrode per unit area; and a processor that estimates the output performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value, wherein the volume reference value is a cumulative intrusion value corresponding to an expected output value required for the rechargeable battery when the rechargeable battery is continuously discharged.

[0013] The pores may have a diameter greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

[0014] If the cumulative intrusion value is the volume reference value or more, the processor may determine that the rechargeable battery including the positive electrode satisfies the expected output value.

[0015] An apparatus for estimating the performance of a rechargeable battery according to the present invention includes: a communication unit that receives a cumulative intrusion value from a device for measuring the volume of pores formed in a negative electrode, the cumulative intrusion value being a summed value of the volumes of all pores of the negative electrode per unit area; and a processor that estimates the charging performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value, wherein the volume reference value is a cumulative intrusion value corresponding to an expected SOC (state of charge) value required for the rechargeable battery at a charging end time when the rechargeable battery is continuously charged.

[0016] The pores may have a diameter greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

[0017] If the cumulative intrusion value is the volume reference value or greater, the processor may determine that the rechargeable battery including the negative electrode satisfies the expected SOC value.

[0018] A method for estimating the performance of a rechargeable battery of the present invention includes the following steps: receiving a cumulative intrusion value from a device for measuring the volume of pores formed in a positive electrode, the cumulative intrusion value being the sum of the volumes of all pores of the positive electrode per unit area; comparing the cumulative intrusion value with a volume reference value; and determining that the rechargeable battery including the positive electrode meets an expected output value upon continuous discharge if the comparison result is that the cumulative intrusion value is the volume reference value or greater, wherein the volume reference value is the cumulative intrusion value corresponding to the minimum value of the expected output value.

[0019] The pores may have a diameter size greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

[0020] A method for estimating the performance of a rechargeable battery of the present invention includes the following steps: receiving a cumulative intrusion value from a device for measuring the volume of pores formed in a negative electrode, the cumulative intrusion value being the sum of the volumes of all pores of the negative electrode per unit area; comparing the cumulative intrusion value with a volume reference value; and if the comparison result is that the cumulative intrusion value is the volume reference value or greater, determining that the rechargeable battery including the negative electrode meets an expected SOC (state of charge) value at a charging end time when continuously charged, wherein the volume reference value is a cumulative intrusion value corresponding to the expected SOC value.

[0021] The pores may have a diameter size greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

[0022] Beneficial effects

[0023] The present invention can estimate the degree of improvement in output performance or fast charging performance of a rechargeable battery through a simple method for measuring cumulative intrusion of an electrode.

[0024] The present invention estimates the output performance or the rapid charging performance in the electrode state, and if it does not satisfy predetermined conditions, a rechargeable battery (battery cell) cannot be manufactured, so it has a cost saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a block diagram illustrating an apparatus for estimating performance of a rechargeable battery according to an embodiment.

[0026] Figure 2 is a flow chart illustrating a method for estimating performance of a rechargeable battery according to an embodiment.

[0027] Figure 3 and Figure 4 is a graph illustrating the correlation between cumulative intrusion and tortuosity.

[0028] Figures 5 to 8 is a graph illustrating the correlation between cumulative intrusion and polarization resistance (Rpola).

[0029] Figure 9 Graph illustrating the correlation between the degree of curvature and the polarization resistance (Rpola).

[0030] Figure 10 and Figure 11 is a graph illustrating the correlation between cumulative intrusion and battery performance.

[0031] Figures 12 to 21 is a graph illustrating the correlation between polarization resistance (Rpola) and battery performance.

[0032] Figures 22 to 26 This is a diagram illustrating the influence of pore size on battery performance. DETAILED DESCRIPTION

[0033] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings. In this specification, the same or similar components will be represented by the same or similar reference numerals, and repeated descriptions thereof will be omitted. The terms "module" and "unit" used for components used in the following description are used only for ease of explanation. Therefore, these terms do not have a meaning or function to distinguish them from each other. In addition, when describing the embodiments of this specification, when it is determined that a detailed description of the well-known technology associated with the present invention may make the subject of the present invention unclear, the detailed description will be omitted. In addition, the drawings are provided only to enable the embodiments disclosed in this specification to be easily understood, and are not to be construed as limiting the spirit disclosed in this specification, and it is to be understood that the present invention includes all modifications, equivalents and alternative forms that do not depart from the scope and spirit of the invention.

[0034] Terms including ordinal numbers such as first, second, etc. will only be used to describe various components and should not be construed as limiting these components. The terms are only used to distinguish one component from other components.

[0035] It is to be understood that when a component is referred to as being “connected” or “coupled” to another component, it may be directly connected or coupled to the other component, or may be connected or coupled to the other component with other components interposed therebetween. On the other hand, it is to be understood that when a component is referred to as being “directly connected or coupled” to another component, it may be connected or coupled to the other component without another component interposed therebetween.

[0036] It will also be understood that the terms “including” or “having” used in this specification indicate the presence of stated features, numbers, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0037] Figure 1 is a block diagram illustrating an apparatus for estimating performance of a rechargeable battery according to an embodiment.

[0038] Reference Figure 1 , the apparatus 100 for estimating performance of a rechargeable battery includes a communication unit 110 , a memory 130 , and a processor 150 .

[0039] A rechargeable battery is a battery composed of at least one electrochemical cell that can be repeatedly charged and discharged. Hereinafter, a rechargeable battery is described as a lithium ion (Li-ion) rechargeable battery that generates electricity through a chemical reaction of lithium, but is not limited thereto, and may include rechargeable batteries that can be repeatedly charged and discharged, such as nickel-cadmium (NiCd) batteries, nickel-metal hydride (NiMH) batteries, and the like.

[0040] A rechargeable battery may include a positive electrode, a negative electrode, an electrolyte solution, and a separator.

[0041] On a thin aluminum substrate that maintains the shape of the positive electrode, the positive electrode can be coated with a mixture of a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is a lithium ion (Li + ) materials, such as lithium oxide, which is a combination of lithium and oxygen. That is, the positive electrode active material provides lithium ions (Li + ) and participates in the electrode reactions of actual batteries. The conductive agent increases the conductivity of the low-conductivity positive electrode active material. The binder acts as a bonding agent to help the active material and conductive agent settle well on the aluminum substrate.

[0042] For the negative electrode, the negative electrode active material, conductive agent and binder are coated on the copper substrate. The negative electrode active material stores lithium ions (Li + ), and mainly uses graphite with a stable structure. Graphite has the following properties that negative electrode active materials must have: structural stability, low electrochemical reactivity, and the ability to store a large amount of lithium ions (Li + The negative electrode active material allows current to flow through the external circuit while reversibly absorbing and releasing lithium ions (Li + ).

[0043] The electrolyte solution is a medium that allows lithium ions (Li+) to move between the positive electrode and the negative electrode. As the electrolyte solution, materials with high ionic conductivity can be used to make lithium ions (Li + ) moves well. The electrolyte solution can include salt, solvent and additives. Salt is a kind of electrolyte that can supply lithium ions (Li + ) through which the liquid passes, the solvent is an organic liquid used to dissolve the salt, and the additive is a material added in small amounts for a specific purpose.

[0044] The separator is a porous polymer film that physically prevents the positive electrode and the negative electrode from contacting each other. + ) can move through the pores formed in the separator. For example, if the positive electrode comes into direct contact with the negative electrode, the battery may short-circuit or explode.

[0045] The performance required of the rechargeable battery 10 varies depending on its usage environment. For example, the output performance of the rechargeable battery 10 is such that it can supply power to the cell t. For example, the power required to execute an image on a smartphone is greater than the power required to execute a phone call, and in this case, the output of the rechargeable battery 10 supplying power to the smartphone is also determined accordingly. For example, if the speed of electron movement increases or lithium ions (Li + ) is increased, the output that the rechargeable battery 10 can provide can also be increased.

[0046] The communication unit 110 includes a device (not shown) for measuring the volume of pores formed in the electrode via a wired / wireless network, for example, a communication module for connecting to a pore measurement device (e.g., a porosimeter). For example, the communication unit 310 may include at least one communication module among wired Internet, wireless Internet such as WiFi, portable Internet such as WiBro or WiMAX, 2G mobile communication networks such as GSM or CDMA, 3G mobile communication networks such as WCDMA or CDMA 2000, 3.5G mobile communication networks such as HSDPA or HSUPA, 4G mobile communication networks such as LTE networks, and 5G mobile communication networks.

[0047] The communication unit 110 may receive a cumulative intrusion value to be transmitted to the processor 150 and stored in the memory 130 under the control of the processor 150 , the cumulative intrusion value being a summed value of volumes of all pores per unit area of ​​the positive electrode or negative electrode transmitted from the porosimeter through the network.

[0048] The memory 130 may store the cumulative intrusion value of the positive polarity or the negative polarity received through the communication unit 110 .

[0049] The processor 150 compares the cumulative intrusion value, which is a summed value of the volumes of all pores per unit area of ​​the electrode from the porosimeter through the communication unit 310, with a volume reference value, thereby estimating the performance of the rechargeable battery.

[0050] According to an embodiment, if the cumulative intrusion value of the positive electrode is greater than the first volume reference value, the processor 150 determines that the output performance of the rechargeable battery including the corresponding positive electrode meets the expected output value. According to an embodiment, the processor 150 can estimate the output performance of the rechargeable battery including the positive electrode whose electrode state is to be verified without actually assembling the rechargeable battery including the positive electrode.

[0051] According to another embodiment, if the cumulative intrusion value of the negative electrode is equal to or greater than the second volume reference value, the processor 150 may determine that the charging performance of the rechargeable battery including the corresponding negative electrode meets the expected charging performance. Specifically, the expected charging performance corresponds to the SOC (State of Charge) value at the end of charging when the rechargeable battery is continuously charged. According to an embodiment, the processor 150 can estimate the charging performance of the rechargeable battery including the negative electrode whose electrode state is to be verified, even if the rechargeable battery including the negative electrode has not been actually assembled.

[0052] The first volume reference value may be a cumulative intrusion value corresponding to an expected output value required for the rechargeable battery when the rechargeable battery is continuously discharged. The second volume reference value may be a cumulative intrusion value corresponding to an expected SOC (State of Charge) value required for the rechargeable battery at the end of charging when the rechargeable battery is continuously charged.

[0053] As the cumulative intrusion value increases, the tortuosity value reflecting the structural characteristics of the pore decreases. Then, the value of the polarization resistance (polarization resistor, Rpola) also decreases, and the output performance or charging performance of the battery increases. At this time, the cumulative intrusion value shows an inversely proportional relationship with the tortuosity value, and as the tortuosity value decreases, the polarization resistance (Rpola) value tends to decrease accordingly. In addition, as the polarization resistance (Rpola) value decreases, the output performance or charging performance of the rechargeable battery improves. Now, together with Figures 3 to 26 Let's explain it in more detail.

[0054] Figure 2 is a flowchart illustrating a method for estimating performance of a rechargeable battery according to an electrode structure according to an embodiment.

[0055] Reference Figure 2 First, the apparatus 100 for estimating performance of a rechargeable battery receives a cumulative intrusion value of a summed value of volumes of all pores per unit area transmitted from a porosimeter for measuring volumes of pores formed in an electrode ( S100 ).

[0056] Porosimeters can measure the size and distribution of polymer pores and the total pore volume within a predetermined area. The pore size in the electrode can vary, and the porosimeter can detect the cumulative intrusion value for each pore size by utilizing the characteristic that the mercury intrusion pressure varies according to the pore size.

[0057] According to an embodiment, the apparatus 100 for estimating performance of a rechargeable battery may receive a cumulative intrusion value, which is a summed value of volumes of all pores of the positive electrode per unit area, from the porosimeter.

[0058] According to another embodiment, the apparatus 100 for estimating the performance of a rechargeable battery may receive a cumulative intrusion value, which is a summed value of volumes of all pores of the negative electrode per unit area, from a porosimeter.

[0059] Next, the apparatus 100 for estimating performance of a rechargeable battery compares the cumulative intrusion value with a volume reference value ( S200 ).

[0060] According to the basis to be described later Figures 3 to 26 The experimental results show that when the cumulative intrusion value increases (1), the curvature value, which reflects the structural characteristics of the pore, decreases. As the curvature value decreases (2), the polarization resistance (Rpola) value also decreases. At this time, the polarization resistance (Rpola) is determined by the ions (Li + ) and can be calculated based on the discharge current value obtained by discharging the rechargeable battery at constant current (CC) and constant voltage (CV). When the polarization resistance (Rpola) value decreases (3), battery performance (i.e., output performance and fast charging performance) improves.

[0061] In short, if the cumulative intrusion value increases, the performance of the rechargeable battery improves. For example, if the cumulative intrusion value of the positive electrode increases, the continuous discharge output performance of the rechargeable battery improves. As another example, if the cumulative intrusion value of the negative electrode increases, the continuous fast charge performance of the rechargeable battery improves. In this case, the pores relevant to the performance of the rechargeable battery are pores with a diameter greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

[0062] According to an embodiment, if there is a performance index expected from a fully assembled rechargeable battery, a cumulative intrusion value corresponding to the performance index can be calculated as a volume reference value. Then, by comparing the cumulative intrusion value measured at the electrode of the verification target with the volume reference value corresponding to the performance index, it can be determined whether the performance of the rechargeable battery including the electrode of the verification target has passed (passed) or failed (failed).

[0063] According to an embodiment, the apparatus 100 for estimating rechargeable battery performance may preset a cumulative intrusion value corresponding to an output performance indicator expected for a fully assembled rechargeable battery as a first volume reference value. Specifically, the first volume reference value may be a cumulative intrusion value corresponding to an expected output value required for a fully assembled rechargeable battery when the rechargeable battery is continuously discharged.

[0064] According to another embodiment, the apparatus 100 for estimating rechargeable battery performance may preset a cumulative intrusion value corresponding to a charging performance indicator expected for a fully assembled rechargeable battery as a second volume reference value. Specifically, the second volume reference value may be a cumulative intrusion value corresponding to an expected state of charge (SOC) value required for the fully assembled rechargeable battery at the end of charging when the rechargeable battery is continuously charged. In this case, if the SOC value at the end of charging is high, the charging performance of the rechargeable battery is also improved.

[0065] Next, if the cumulative intrusion value is greater than the volume reference value ( S200 , YES), the apparatus 100 for estimating rechargeable battery performance determines whether the performance of the rechargeable battery including the corresponding electrode passes a performance index expected from a fully assembled rechargeable battery (PASS) ( S300 ).

[0066] According to an embodiment, if the cumulative intrusion value of the positive electrode is equal to or greater than the first volume reference value, the apparatus 100 for estimating the performance of a rechargeable battery can determine that the output performance of the rechargeable battery including the corresponding positive electrode meets the expected output value. The apparatus 100 for estimating the performance of a rechargeable battery can estimate the output performance of a rechargeable battery including a positive electrode whose electrode state is to be verified without assembling the rechargeable battery.

[0067] According to another embodiment, if the cumulative intrusion value of the negative electrode is equal to or greater than the second volume reference value, the apparatus 100 for estimating the performance of a rechargeable battery can determine that the charging performance of the rechargeable battery including the corresponding negative electrode meets the expected charging performance. Specifically, the expected charging performance corresponds to the SOC value at the end of charging when the rechargeable battery is continuously charged. The apparatus 100 for estimating the performance of a rechargeable battery can estimate the charging performance of a rechargeable battery including a negative electrode whose electrode state is to be verified without the rechargeable battery being assembled.

[0068] Next, if the cumulative intrusion value is less than the volume reference value (S200, No), the apparatus 100 for estimating rechargeable battery performance determines that the performance of the rechargeable battery including the corresponding electrode does not pass the performance index expected from a fully assembled rechargeable battery (Failed) (S400).

[0069] Figures 3 to 26The experimental data and their analysis are derived from the correlation between the cumulative intrusion, tortuosity, polarization resistance (Rpola) of the electrode and the battery performance.

[0070] Reference Figures 3 to 26 The following can be deduced from the experimental results. As the cumulative intrusion value increases (1), the curvature value, which reflects the structural characteristics of the pore, decreases. As the curvature value decreases (2), the polarization resistance (Rpola) value also decreases. At this time, the polarization resistance (Rpola) is determined by the ions (Li + ) and can be calculated based on the discharge current value obtained by discharging the rechargeable battery at constant current (CC) and constant voltage (CV). When the polarization resistance (Rpola) value decreases (3), battery performance (i.e., output performance and fast charging performance) improves.

[0071] In this case, the cumulative intrusion may be a value obtained by summing the pore volumes measured when the pore volumes of a plurality of pores having diameters within a predetermined range are sequentially measured. Figure 3 For electrode A, the cumulative intrusion value on the Y axis corresponding to a pore size diameter of 1 micron on the X axis is about 0.00175 (mL / cm 2 In this case, the cumulative intrusion value of electrode A is 0.00175 (mL / cm 2 ) may mean the sum of the pore volumes measured when the pore volumes are sequentially measured from pores having a diameter of 0.01 μm to pores having a diameter of 1 μm. That is, the value on the Y axis corresponding to an arbitrary pore diameter on the X axis may be a value obtained by summing the pore volumes measured when the pore volumes are sequentially measured from the pore diameter at the start time on the X axis to an arbitrary pore diameter.

[0072] According to an embodiment, the cumulative intrusion is most affected by the sum of the volumes of pores having a diameter greater than or equal to 0.1 micrometer and less than or equal to 1 micrometer. Figure 3 , the cumulative intrusion value from a pore with a diameter of 0.01 micrometer to a pore with a diameter of 5 micrometers (the rightmost X-axis value of the graph) can be determined by the cumulative intrusion from a pore with a diameter of 0.1 micrometer to a pore with a diameter of 1 micrometer. Figures 22 to 26 This is described in detail.

[0073] Figure 3 and Figure 4 is a graph illustrating the correlation between cumulative intrusion and tortuosity. Figure 3 Cumulative intrusion measurements are shown for multiple electrodes A, B, and C of different types of positive active materials, and Figure 4 Shown Figure 3 The dependence of the cumulative intrusion on the tortuosity of multiple electrodes A, B and C is shown in FIG.

[0074] If the type or amount of the positive electrode active material is changed, the volume and formation structure of pores formed by the positive electrode may be changed.

[0075] The tortuosity is a value that varies depending on the pore-forming structure. If the straight-line distance between the top and bottom of the electrode is assumed to be 1 and set as a reference value, the tortuosity is expressed by comparing the shortest distance through the pore to the top and bottom of the electrode with the reference value. Specifically, it can be seen that when the tortuosity value is closer to 1, ions travel the shortest straight-line distance, while when the tortuosity value is greater than 1, ions travel through a different channel.

[0076] In summary, as the cumulative intrusion value of the electrode increases (A>B>C), the curvature value decreases (A <B<C)。

[0077] Figures 5 to 8 is a graph illustrating the correlation between cumulative intrusion and polarization resistance (Rpola). Figure 5 The correlation between the cumulative intrusion and polarization resistance of multiple electrodes A, B, and C is illustrated.

[0078] Reference Figure 5 , the cumulative intrusion Vp value decreases in the order of the first electrode A, the second electrode B, and the third electrode C. Also, the polarization resistance (Rpola) value increases in the order of the first electrode A, the second electrode B, and the third electrode C. Therefore, it can be seen that the cumulative intrusion Vp value and the polarization resistance (Rpola) of the electrode have an inversely proportional relationship.

[0079] Figure 6 and Figure 7 is another example graph illustrating the correlation between cumulative intrusion and polarization resistance (Rpola). Figure 6 shows the cumulative intrusion measurements depending on the pore size of a plurality of positive electrodes A, B and C having different porosities, and Figure 7 Shown Figure 6 The correlation between the cumulative intrusion and polarization resistance (Rpola) of multiple electrodes A, B and C is shown in FIG.

[0080] [Table 1]

[0081]

[0082] Table 1 shows the Figure 7 ] The discharge end current (End I) and polarization resistance (Rpola) values ​​of continuous discharge output with varying porosity of multiple positive electrodes A, B, and C are shown in FIG. The higher the discharge end current (End I) value, the better the continuous discharge output performance of the rechargeable battery.

[0083] Reference Figure 6 and Figure 7As shown in Table 1, as the cumulative intrusion value increases (A < B < C), the polarization resistance (Rpola) value decreases (A > B > C), and the output performance improves (A < B < C). Correspondingly, as the cumulative intrusion value increases (A < B < C), the output performance also improves (A < B < C).

[0084] Figure 8 Shows the cumulative intrusion measurement values of the pore diameters of multiple positive electrodes A and B with different positive electrode conductive materials.

[0085] [Table 2]

[0086]

[0087] Table 2 shows that depending on Figure 8 the discharge end current (End I) and polarization resistance (Rpola) values of the continuous discharge output depending on the change in the conductive materials of the multiple positive electrodes A and positive electrode B shown in. The higher the discharge end current (End I) value, the better the continuous discharge output performance of the rechargeable battery.

[0088] Referring to Figure 8 and Table 2, pore formation varies depending on the type of conductive material of the positive electrode that can be expressed as cumulative intrusion. Compared with the first electrode A using only the first conductive material (Super C), the second electrode B using both the first conductive material (Super C) and the second conductive material (CNT) has a higher cumulative intrusion value (A < B) and a smaller polarization resistance (Rpola) value (A < B), and a larger output performance (A < B).

[0089] Figure 9 is a graph illustrating the correlation between the degree of curvature and the polarization resistance (Rpola). The movement of ions has characteristics depending on the structure of the pores formed in the electrode. That is, the movement of ions depends on the degree of curvature corresponding to the structure of the pores formed in the electrode.

[0090] In summary, when the degree of curvature value increases (A < B < C), the polarization resistance (Rpola) value also increases (A < B < C). In other words, when the degree of curvature value decreases (A > B > C), the polarization resistance (Rpola) value also decreases (A > B > C).

[0091] Figure 10 and Figure 11 is a graph illustrating the correlation between cumulative intrusion and battery performance. Figure 10 Shows the first electrode A and the second electrode B with different cumulative intrusion values, and Figure 11 shows Figure 10 the end-of-charge SOC values of each of the first electrode A and the second electrode B of.

[0092] In the negative electrode, as the cumulative intrusion value increases, the ion movement speed during charging increases and the end-of-charge SOC is higher. In summary, for the negative electrode, cumulative intrusion can be a sign of charging performance because the pore-forming structure affects charging performance.

[0093] Referring to Figure 10 , for the Y-axis value corresponding to the pore diameter of 1 μm on the X-axis, that is, for the cumulative intrusion value, the first electrode A has about 0.15 (mL / g) and the second electrode B has about 0.175 (mL / g). That is, the cumulative intrusion value of the first electrode A is smaller than that of the second electrode B. Additionally, even when comparing the Y-axis values (i.e., cumulative intrusion) in the region where the pore diameter on the X-axis is 1 μm or larger, the value of the first electrode A is smaller than that of the second electrode B (A < B).

[0094] Referring to Figure 11 , the end-of-charge SOC value of the first electrode A is smaller than that of the second electrode B (A < B).

[0095] In summary, when the cumulative intrusion value is small (A < B), the battery charging performance is also poor (A < B). That is, when the cumulative intrusion value is large (A < B), the battery charging performance is also good (A < B).

[0096] Figures 12 to 21 is a graph illustrating the relationship between the polarization resistance (Rpola) and the battery performance.

[0097] Figure 12 Shows the discharge current measured while discharging the rechargeable battery at a constant voltage (CV).

[0098] Specifically, to confirm the correlation between the polarization resistance (Rpola) and the battery performance, a rechargeable battery performance estimation system (not shown) can measure the discharge current output from the rechargeable battery while discharging the rechargeable battery at a constant voltage (CV) mode after discharging the rechargeable battery at a constant current (CC) mode for a predetermined time (e.g., 1 s). According to another embodiment, a rechargeable battery performance estimation system (not shown) can perform a discharge test and send the experimental data and analysis results as performance results to the device 100 for estimating the rechargeable battery performance.

[0099] For example, if the lithium ions (Li +), the output of the rechargeable battery is also improved. When the rechargeable battery is continuously discharged within a predetermined time and the state of charge (SOC) of the rechargeable battery decreases and reaches a predetermined value (for example, SOC 30%, etc.), an interval in which the output performance decreases rapidly may occur. At this time, researchers and the like may want to check how much the output performance of the rechargeable battery is improved in the corresponding interval by changing the positive electrode additive, the porosity of the positive electrode, the negative electrode active material, etc. At this time, the starting point of the interval can be set to the state of charge (SOC) of the rechargeable battery. In addition, the voltage value corresponding to the state of charge (SOC) can be set as a reference voltage.

[0100] The rechargeable battery performance estimation system can set a discharge interval for discharging the rechargeable battery at a constant voltage (CV) based on the state of charge (SOC) of the rechargeable battery. For example, if the state of charge (SOC) of the rechargeable battery reaches a first state of charge (SOC) (e.g., SOC 35%) in real time, the rechargeable battery performance estimation system starts constant voltage (CV) discharge for discharging the rechargeable battery at a predetermined constant voltage (CV). In addition, when the real-time state of charge (SOC) of the rechargeable battery reaches a second state of charge (SOC) (e.g., SOC20%), the rechargeable battery performance estimation system controls the discharger 20 to end the constant voltage (CV) discharge of the rechargeable battery. That is, the rechargeable battery performance estimation system can discharge the rechargeable battery at a constant voltage (CV) in a discharge interval in which the starting point is set to SOC 35% and the end point is set to SOC 20%. In this case, the time corresponding to the discharge interval is defined as a discharge period. In Figure 12 In the embodiment of the present invention, the discharge period can be regarded as the period between 0s and about 700s.

[0101] For example, Figure 12 1. The discharge current according to the passage of time calculated under the following experimental conditions is shown: when the state of charge (SOC) is 35% and the reference voltage is 2.5V, the constant voltage (CV) discharge of the rechargeable battery starts and ends when the state of charge (SOC) reaches 20%.

[0102] Figure 13 Shown in Figure 12 The relationship between the resistance change according to the SOC change during the discharge period.

[0103] During the discharge period, the rechargeable battery performance estimation system may estimate Figure 12 Since the test is a constant voltage (CV) discharge, the voltage is constant and the current change depending on the passage of time can be seen in Figure 12In addition, since the SOC value corresponding to each time can also be known, the rechargeable battery performance estimation system can deduce the relationship between the resistance change according to the SOC change during the discharge period. For example, the rechargeable battery performance estimation system can calculate the resistance change according to the SOC change during the discharge period based on the SOC value corresponding to each time. Figure 13 With the same curve Figure 12 To calculate the relationship between the resistance change according to the SOC change.

[0104] The rechargeable battery performance estimation system can be obtained from Figure 13 The polarization resistance (Rpola) is calculated based on the graph shown in Figure 1. First, the rechargeable battery performance estimation system calculates the resistance value of a first resistor (Rohmic) during the discharge period based on a resistance change relationship that depends on SOC changes. The first resistance is the resistance caused by the voltage drop of the rechargeable battery. The resistance value of the first resistor (Rohmic) corresponds to the sum of the resistance values ​​(Rohm) derived from the electrical characteristics of the rechargeable battery, the charge transfer resistance (Rct), and the resistance (Rocv) caused by changes in the open circuit voltage (OCV).

[0105] For example, when the rechargeable battery is discharged to a constant voltage (CV), the first resistance (Rohmic) may appear within about 0.1 seconds. Figure 5 , the rechargeable battery performance estimation system may set a resistance value generated at the time of the discharge period, more precisely, after 0.1 seconds, as the resistance value of the first resistor (Rohmic).

[0106] The rechargeable battery performance estimation system calculates the second resistance (Rdiff), which is the resistance that occurs when ions are inserted into the active material of the rechargeable battery. In addition, in another expression, the second resistance (Rdiff) can be defined as the resistance Rdiff caused by the diffusion of the electrolyte.

[0107] Reference Figure 13The rechargeable battery performance estimation system may calculate the resistance value (e.g., 9 ohms) at the end point P3 of the discharge period as the upper limit value of the second resistor (Rdiff) on an extension line S, where the extension line S connects a first point P1 corresponding to the resistance value at the start time of the discharge period and a second point P2 where the resistance change rate with respect to SOC change in the resistance change relationship with respect to SOC change exceeds a first reference value. The rechargeable battery performance estimation system may calculate the resistance value (e.g., 7.8 ohms) of the second resistor (Rdiff) based on the difference (9-1.2=7.8 ohms) between the upper limit value of the second resistor (Rdiff) and the resistance value (e.g., 1.2 ohms) of the first resistor (Rohmic). Here, the second point P2 may be defined as a point where the slope suddenly changes in the resistance change relationship graph according to SOC change, i.e., a point where the slope exceeds a first predetermined reference value.

[0108] The rechargeable battery performance estimation system calculates a third resistance (Ppola) which is a polarization resistance generated by ion movement in the rechargeable battery. Figure 13 , the rechargeable battery performance estimation system can calculate the resistance value of the third resistor (Ppola) (e.g., 5.8 ohms) based on the difference (14.8-9=5.8 ohms) between the resistance value at the end point P4 of the discharge period (e.g., 14.8 ohms) and the upper limit value of the second resistor (e.g., 9 ohms).

[0109] Figure 14 and Figure 15 The experimental results of output performance at room temperature and low temperature are shown respectively.

[0110] Figure 14 The resistance change relationship according to the SOC change during the discharge period obtained by performing a constant voltage (CV) discharge test on each of the plurality of electrodes A, B, C, and D at room temperature (e.g., 25°C) and predetermined starting conditions (15C and 2.5V) is shown. Figure 15 The present invention shows the relationship between resistance change and SOC change during a discharge period, obtained by performing a constant voltage (CV) discharge test on each of multiple electrodes A, B, C, and D at a low temperature (e.g., -10°C) and predetermined starting conditions (5.5°C and 2.5V). The multiple electrodes A, B, C, and D were identical in other conditions, differing only in temperature and starting conditions, and the discharge test was performed. The discharge test measures the discharge current output from the rechargeable battery during the discharge period, which is a period in which the rechargeable battery is discharged at a constant current (CC) and constant voltage (CV).

[0111] [Table 3]

[0112]

[0113] Table 3 shows the Figure 14 and Figure 15 The end-of-discharge current (I) and polarization resistance (Rpola) values ​​for the continuous discharge output of each of the multiple electrodes A, B, C, and D were calculated. Referring to Table 3, it can be confirmed that the end-of-discharge current (I) value is higher when the polarization resistance (Rpola) value decreases (A > B > C > D), regardless of temperature and initial conditions. In this case, the higher the end-of-discharge current (I) value, the better the continuous discharge output performance of the rechargeable battery.

[0114] Therefore, it can be confirmed that the polarization resistance (Rpola) is a factor indicating the performance of the rechargeable battery regardless of temperature.

[0115] Figure 16 and Figure 17 The correlation between polarization resistance (Rpola) and end-of-charge SOC is shown.

[0116] The first electrode A had a porosity of 26%, and the second electrode B had a porosity of 30%.

[0117] [Table 4]

[0118] Negative electrode porosity A(26％) B(30％) Rpola(mohm) 2 3.7

[0119] Table 4 shows the polarization resistance (Rpola) values ​​of the first electrode A and the second electrode B. Figure 17 The curve is obtained by Figure 13 Calculated by the method described in .

[0120] Reference Figure 16 From Table 4, it can be confirmed that the polarization resistance (Rpola) value of the first electrode A is smaller than the polarization resistance (Rpola) value of the second electrode B, and the charge end SOC value of the first electrode A is smaller than the charge end SOC value of the second electrode B.

[0121] Figure 18 and Figure 19 is a graph showing the correlation between polarization resistance (Rpola) and discharge end current (End I).

[0122] Figure 18 The discharge current value according to the lapse of time is shown as a discharge test result for the first electrode A to which the positive electrode additive is not added and the second electrode B to which the positive electrode additive is added. Figure 19 It shows that the Figure 18 FIG. 1 is a graph showing resistance changes of the first electrode A and the second electrode B as the SOC changes.

[0123] [Table 5]

[0124]

[0125] Table 5 shows the Figure 19 The curve graph is obtained by Figure 13 The polarization resistance (Rpola) values ​​of the first electrode A and the second electrode B obtained by the method described in and the discharge end current (End I) of the first electrode A and the second electrode B obtained by the discharge test. Referring to Table 5, if the ionic conductivity is improved by adding a positive electrode additive, the polarization resistance (Rpola) decreases (A>B).

[0126] Figure 20 and Figure 21 is another graph showing the correlation between the polarization resistance (Rpola) and the discharge end current (End I).

[0127] Figure 20 Shown are discharge current values ​​depending on the lapse of time, which are discharge test results for a plurality of electrodes A, B, and C having positive electrodes with different porosities. Figure 21 It shows that according to Figure 20 Graph showing resistance change with SOC change of a plurality of electrodes A, B, and C. The porosity of the first electrode A is 21%, the porosity of the second electrode B is 23%, and the porosity of the third electrode C is 30%.

[0128] [Table 6]

[0129]

[0130] Table 6 shows the Figure 21 The curve graph is obtained by Figure 13 The polarization resistance (Rpola) and discharge end current (end I) of multiple electrodes A, B and C were calculated by the method described in . Referring to Table 5, when the polarization resistance (Rpola) value decreases due to the increase of porosity and the improvement of ionic conductivity (A>B>C), the discharge end current (end I) increases (A <B<C)。

[0131] Figures 22 to 26 This is a diagram illustrating the influence of pore size on battery performance.

[0132] When referring to Figures 3 to 21 When explaining, the pores that affect the cumulative intrusion value, tortuosity value, polarization resistance (Rpola) value, and battery performance are pores with a diameter greater than or equal to 0.1 micrometer and less than or equal to 1 micrometer. In other words, the diameter of the pores that affect the cumulative intrusion value is greater than or equal to 0.1 micrometer and less than or equal to 1 micrometer.

[0133] Figure 22The volume (mL) occupied by pores having corresponding diameters per unit mass (g) of the electrodes is represented according to changes in pore diameter (pore size diameter) in the plurality of electrodes A, B, and C. That is, the X-axis is the diameter of the pore (pore size diameter), and the Y-axis is the entire volume of the pores having a specific diameter indicated on the X-axis.

[0134] Specifically, in Figure 22 In FIG, the incremental intrusion on the Y axis represents the entire volume of holes having each specific diameter on the X axis, and is different from the above-mentioned cumulative intrusion which indicates the entire volume of all holes below the corresponding diameter indicated on the X axis. For example, referring to Figure 22 The volume occupied by pores with a diameter greater than or equal to 0.1 μm and less than or equal to 1 μm is the largest.

[0135] Figure 23 represents the value for each of the plurality of electrodes A, B and C. Figure 21 The cumulative intrusion of the area (A) Figure 24 Indicates that Figure 21 The cumulative intrusion of the area (B), and Figure 25 Indicates that Figure 21 Cumulative intrusion of the region (C).

[0136] Figure 26 : is a graph for explaining the correlation between the cumulative penetration (Vp) and the curvature of the plurality of electrodes A, B and C. Figure 26 , the cumulative intrusion Vp is the largest in the first electrode A, followed by the second electrode B and the third electrode C (A>B>C). In addition, the curvature is opposite to the cumulative intrusion Vp value of each of the first electrode A, the second electrode B and the third electrode C, and the first electrode A is the smallest, followed by the second electrode B and the third electrode C (A>B>C). <B<C)。

[0137] Reference Figure 23 and Figure 26 ,exist Figure 23 In the example, only the cumulative intrusion values ​​of pores with a diameter of 0.1 μm or less are large in the order of the third electrode C, the first electrode A, and the second electrode B (C>A>B). Figure 26 , the cumulative intrusion Vp value has a large value in the order of the first electrode A, the second electrode B, and the third electrode C (A>B>C).

[0138] In summary, pores with a diameter of 0.1 micrometer or less do not affect tortuosity.

[0139] Reference Figure 24 and Figure 26 ,exist Figure 24In FIG, only the cumulative intrusion values ​​of the pores having a diameter greater than or equal to 0.1 μm and less than or equal to 1 μm show the order of the first electrode A, the second electrode B, and the third electrode C (A>B>C). Figure 26 As shown in , this is the same size ratio as the cumulative intrusion Vp, showing an inverse correlation with the tortuosity (A>B>C).

[0140] In summary, pores having a diameter greater than or equal to 0.1 μm and less than or equal to 1 μm have an influence on tortuosity and the like.

[0141] Reference Figure 25 and Figure 26 ,exist Figure 25 In FIG, only the cumulative intrusion values ​​of the pores having a diameter greater than or equal to 1 μm and less than or equal to 5 μm show the order of the first electrode A, the third electrode C, and the second electrode B (A>C>B). Figure 26 As shown in , the cumulative intrusion Vp value showing an inversely proportional relationship with the curvature has a maximum value in the order of the first electrode A, the second electrode B, and the third electrode C (A>B>C).

[0142] In general, pores with a diameter greater than or equal to 1 micron and less than or equal to 5 microns do not affect tortuosity.

[0143] Summarize Figures 22 to 26 According to the experimental results shown in , the pores that affect the cumulative intrusion (Vp) value, tortuosity value, polarization resistance (Rpola) value and battery performance are pores with a diameter greater than or equal to 0.1 μm and less than 1 μm.

[0144] While the present invention has been described in connection with what are presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A device for estimating the performance of a rechargeable battery, the device comprising: a communication unit that receives a cumulative intrusion value that is a summed value of volumes of all pores of the positive electrode per unit area from an apparatus for measuring volumes of pores formed in the positive electrode; and a processor that estimates output performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value, in, The volume reference value is a cumulative intrusion value corresponding to an expected output value required for the rechargeable battery when the rechargeable battery is continuously discharged.

2. The apparatus for estimating performance of a rechargeable battery according to claim 1, wherein The pores have a diameter greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

3. The apparatus for estimating performance of a rechargeable battery according to claim 2, wherein If the cumulative intrusion value is the volume reference value or more, the processor determines that the rechargeable battery including the positive electrode satisfies the expected output value.

4. A device for estimating the performance of a rechargeable battery, the device comprising: a communication unit that receives a cumulative intrusion value that is a summed value of volumes of all pores of the negative electrode per unit area from an apparatus for measuring volumes of pores formed in the negative electrode; and a processor that estimates a charging performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value, in, The volume reference value is a cumulative intrusion value corresponding to an expected state of charge (SOC) value required by the rechargeable battery at a charging end time when the rechargeable battery is continuously charged.

5. The apparatus for estimating performance of a rechargeable battery according to claim 4, wherein The pores have a diameter greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

6. The apparatus for estimating performance of a rechargeable battery according to claim 5, wherein If the cumulative intrusion value is the volume reference value or greater, the processor determines that the rechargeable battery including the negative electrode satisfies an expected SOC value.

7. A method for estimating the performance of a rechargeable battery, the method comprising the steps of: receiving a cumulative intrusion value from an apparatus for measuring the volume of pores formed in a positive electrode, the cumulative intrusion value being a summed value of the volumes of all pores of the positive electrode per unit area; estimating an output performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value; as well as If the comparison result is that the cumulative intrusion value is the volume reference value or more, determining that the rechargeable battery including the positive electrode satisfies an expected output value when continuously discharged, The volume reference value is a cumulative intrusion value corresponding to the minimum value of the expected output value.

8. The method for estimating the performance of a rechargeable battery according to claim 7, wherein The pores have a diameter size greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

9. A method for estimating the performance of a rechargeable battery, the method comprising the steps of: receiving a cumulative intrusion value from an apparatus for measuring the volume of pores formed in a negative electrode, the cumulative intrusion value being a summed value of the volumes of all pores of the negative electrode per unit area; estimating a charging performance of the rechargeable battery by comparing the cumulative intrusion value with a volume reference value; and If the comparison result is that the cumulative intrusion value is the volume reference value or more, determining that the rechargeable battery including the negative electrode satisfies an expected state of charge (SOC) value at a charge end time when continuously charged, The volume reference value is a cumulative intrusion value corresponding to the expected SOC value.

10. The method for estimating the performance of a rechargeable battery according to claim 9, wherein The pores have a diameter size greater than or equal to 0.1 micrometers and less than or equal to 1 micrometer.

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