Battery capacity characteristics calculation method

Abstract

The present invention relates to a method for calculating battery capacity characteristics, and provides a method for calculating parameters related to the capacity characteristics of a battery including a negative electrode containing a SiO-based material.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0116792 dated September 16, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated by reference into this specification.

[0002] The present invention relates to a method for calculating battery capacity characteristics, and more particularly to a method for calculating parameters related to the capacity characteristics of a battery including a negative electrode containing a SiO-based material. [Background technology]

[0003] Battery energy density is the most important characteristic of secondary batteries. High energy density is expected to increase the operating time of portable devices and extend the driving range of electric vehicles.

[0004] Lithium-ion batteries have surpassed other batteries with which they previously competed (for example, lead-acid batteries, nickel-metal hydride batteries, etc.), but despite this, there is still a demand for even higher energy density.

[0005] One of the developments to increase the energy density of batteries is to increase the capacity of the negative electrode. This can be achieved by mixing silicon monoxide (SiO) with graphite. However, silicon monoxide forms lithium silicate, a lithium depletion product with little reactivity, and has a very large initial irreversible capacity. [ka]

[0006] To improve this, efforts are being made to increase efficiency on a material-by-material basis by chemically doping silicon monoxide (SiO) with substances such as lithium (Li) and magnesium (Mg).

[0007] However, there is no standard for whether highly efficient silicon monoxide has a stable lifespan in a mixed application cell when it has certain characteristics, and a technology that can define this is needed. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention relates to a method for calculating battery capacity characteristics, and provides a method for calculating parameters related to the capacity characteristics of a battery including a negative electrode containing a SiO-based material.

[0009] The technical problems that the present invention aims to solve are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] The method for calculating the battery capacity characteristics of the present invention includes a negative electrode preparation step of preparing a negative electrode in which graphite and a test SiO-based material are mixed; a charging step of charging a battery including the negative electrode; and a step of measuring the peak value of Li by observing the negative electrode with XRD, C Li , Li2C 12 The peak values ​​of C6(t) and LiC 12 The peak value of C 12 A data collection step of collecting time series data for C6(t); and 12 When the time differential value with respect to (t) is 0, Li , said C6(t) and said C 12 (t) includes a parameter calculation step of calculating K, which is a parameter for the battery capacity characteristic, based on the value of K. Effect of the Invention

[0011] The method for calculating battery capacity characteristics of the present invention quantifies the reaction speed of graphite and SiO with Li to select SiO-based materials.

[0012] The method for calculating battery capacity characteristics of the present invention provides parameters indicating battery capacity characteristics related to the actual usage rate of SiO, which has low durability, and can contribute to the design of batteries with long life and stable cycle performance. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a block diagram showing a battery capacity characterization method of the present invention. [Diagram 2] 13 is a graph showing time series data for C6(t) and C12(t) of battery sample 1. [Diagram 3] 1 is a graph showing the structural changes over time of the negative electrodes of battery sample 1(a) and battery sample 2(b). [Figure 4] 1 is a graph showing the remaining capacity retention according to cycles of battery sample 1 and battery sample 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The method for calculating the battery capacity characteristics of the present invention includes a negative electrode preparation step of preparing a negative electrode in which graphite and a test SiO-based material are mixed; a charging step of charging a battery including the negative electrode; and a step of measuring the peak value of Li, C, by observing the negative electrode by XRD. Li , Li2C 12 The peak values ​​of C6(t) and LiC 12 The peak value of C 12 A data collection step of collecting time series data for C6(t); and 12 When the time differential value with respect to (t) is 0, Li , said C6(t) and said C 12 (t) includes a parameter calculation step of calculating K, which is a parameter for the battery capacity characteristic, based on the value of K.

[0015] In the negative electrode preparation step of the battery capacity characteristic calculation method of the present invention, the negative electrode is prepared so that the weight fraction of the test SiO-based material in the negative electrode is 0.15 or less.

[0016] In the negative electrode preparation step of the method for calculating battery capacity characteristics of the present invention, the SiO-based material is SiO doped with Li, Mg or a mixture thereof.

[0017] In the charging step of the method for calculating battery capacity characteristics of the present invention, the battery is fully charged so that the SOC (state of charge) becomes 100%.

[0018] In the data collection step of the method for calculating battery capacity characteristics of the present invention, the state of charge of the battery is maintained at an SOC of 50% or more.

[0019] In the parameter calculation step of the battery capacity characteristic calculation method of the present invention, K is calculated by the following Equation 1.

[0020]

number

[0021] The method for calculating a battery capacity characteristic of the present invention further includes, after the parameter calculation step, a determination step of comparing the K value with a weight fraction value of the test target SiO-based material in the negative electrode to determine a capacity characteristic state of the battery.

[0022] The battery having the anode containing the SiO-based material of the present invention includes an anode containing graphite and an SiO-based material; an anode current collector to which the anode is applied; a cathode containing lithium; a cathode current collector to which the cathode is applied; a separator laminated between the anode and the cathode; an electrolyte impregnated in the cathode and the anode; and a case that contains the anode, the cathode, the anode current collector, the cathode current collector, the separator, and the electrolyte; wherein the anode contains an SiO-based material doped with Li, Mg, or a mixture thereof, and the K value calculated by the method for calculating battery capacity characteristics described in the above mathematical formula 1 is 12 times or more the weight fraction of the SiO-based material in the anode.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this process, the size and shape of components shown in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, terms specifically defined in consideration of the configuration and operation of the present invention may vary depending on the intention or practice of a user or operator. The definition of such terms should be based on the overall content of this specification.

[0024] In describing the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "one side," "other side," and the like are based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships typically arranged when the product of the present invention is used, and are merely for the purpose of describing or briefly explaining the present invention, and do not present or imply that the displayed devices or elements must necessarily have a specific orientation, be configured or operated in a specific orientation, and should not be understood as limiting the present invention.

[0025] FIG. 1 is a block diagram showing the battery capacity characteristic method of the present invention. FIG. 2 shows the C6(t) and C 12 FIG. 3 is a graph showing the structural changes over time of the negative electrodes of battery sample 1 and battery sample 2. FIG. 4 is a graph showing the remaining life capacity of battery sample 1 and battery sample 2 by cycling.

[0026] Hereinafter, the battery capacity characteristic calculation method of the present invention will be described in detail with reference to FIGS.

[0027] As shown in FIG. 1, the method for calculating the battery capacity characteristics of the present invention includes the steps of: preparing a negative electrode in which graphite and a test SiO-based material are mixed (step S10); charging a battery including the negative electrode (step S20); and measuring the peak value of Li by observing the negative electrode with XRD (step S21). Li , Li2C 12 The peak values ​​of C6(t) and LiC12 The peak value of C 12 A data collection step (step S30) of collecting time series data for C6(t) or C 12 When the time differential value with respect to (t) is 0, Li , said C6(t) and said C 12 A parameter calculation step (step S40) of calculating K, which is a parameter for the battery capacity characteristic, based on the (t) value.

[0028] In the method for calculating battery capacity characteristics of the present invention, the analysis target is a negative electrode containing a SiO-based material, specifically, a graphite-based material containing a SiO-based material, and more specifically, a graphite-based material containing SiO doped with Li, Mg, or the like.

[0029] In the negative electrode preparation step (step S10), the negative electrode is prepared such that the weight fraction of the SiO-based material to be tested in the negative electrode is 0.15 or less. The weight fraction of the SiO-based material to be tested in the negative electrode is 0.01 or more, 0.03 or more, or 0.05 or more, and is also 0.15 or less, 0.12 or less, or 0.10 or less.

[0030] The method for calculating battery capacity characteristics of the present invention can provide parameters that can determine the stability of a battery's life, which varies depending on the characteristics (doping material, doping degree, etc.) of the SiO-based material contained in the negative electrode, for example, the rate of change in remaining life capacity depending on the number of cycles.

[0031] The battery capacity characteristic calculation method of the present invention can determine whether the test SiO-based material can guarantee the life stability of the battery by analyzing a battery equipped with a negative electrode containing the test SiO-based material. More specifically, the effect of the SiO-based material on the life stability of the battery can be provided as a parameter that is quantified. For example, the battery capacity characteristic calculation method of the present invention is performed on a lithium secondary battery equipped with a negative electrode containing the test SiO-based material.

[0032] In the negative electrode preparation step (step S10), the SiO-based material may be SiO doped with Li, Mg, or a mixture thereof. The method for calculating battery capacity characteristics of the present invention can provide a guaranteed degree of battery life stability as a numerical parameter even for SiO-based materials whose doping state is unknown.

[0033] In the charging step (step S20), the battery is fully charged so that the SOC becomes 100%. When a lithium secondary battery is charged, lithium ions move to the negative electrode and are reduced to lithium atoms from the negative electrode. By analyzing the state at this time, the battery capacity characteristic calculation method of the present invention can calculate the K.

[0034] In the data collection step (step S30), the state of charge of the battery is maintained at an SOC of 50% or more. In the data collection step (step S30), it is most preferable to perform the XRD measurement in a fully charged state, but depending on the analysis conditions, the XRD measurement is performed with the state of charge maintained at an SOC of 50% or more. During the XRD measurement, even if the battery is simply fixed to the XRD stage, if self-discharge is fast, the battery is attached to the XRD stage with a charging module connected. The XRD measurement is performed in-situ to observe changes in the battery.

[0035] In the data collection stage (step S30), the XRD measurement is performed at set time intervals. The set time is 2 to 8 hours. Preferably, the set time is 4 to 6 hours. For example, the set time is about 4 hours. That is, in the data collection stage (step S30), the XRD measurement is performed approximately every 4 hours. A battery having a negative electrode containing a SiO-based material is stabilized in about 60 hours. Therefore, the XRD measurement is performed at set time intervals for a period of 40 to 100 hours. That is, the XRD measurement is repeatedly performed at set time intervals until the negative electrode is stabilized.

[0036] The data collected in the data collection step (step S30) is fitted and calculated as a function of time t. 12 The peak values ​​of C6(t) and LiC 12 The peak value of C 12 (t) and are fitted with a function.

[0037] In the parameter calculation step (step S40), K is the reversible reaction of the negative electrode. [ka] Based on this, it is calculated by the following formula 1. 12 For convenience, it may be expressed as LiC6, and in the following formula 1, C6 is Li2C 12 , C 12 LiC 12 Refers to the concentration of.

[0038]

number

[0039] In the parameter calculation step (step S40), C6(t) and C 12 The (t) value is the value when sufficient time has passed and the value converges to a specific value. 12 C6(t) and C at t when the time derivative of (t) is 0 12 The (t) value is applicable to Equation 1.

[0040] As shown in Fig. 1, after the parameter calculation step (step S40), a determination step (step S50) is further included in which the K value is compared with the weight fraction value of the SiO-based material to be tested in the negative electrode to determine the capacity characteristic state of the battery. Specifically, the greater the value obtained by dividing the weight fraction value of the SiO-based material to be tested in the negative electrode by the K value, the better the life stability of the battery is (e.g., the less the decrease in remaining life capacity with the increase in the number of cycles). For example, when the value obtained by dividing the weight fraction value of the SiO-based material to be tested in the negative electrode by the K value is 12 or more, 20 or more, 30 or more, or 40 or more, it can be determined that the life stability of the battery is ensured.

[0041] The battery having the anode containing the SiO-based material of the present invention includes an anode containing graphite and an SiO-based material; an anode current collector to which the anode is applied; a cathode containing lithium; a cathode current collector to which the cathode is applied; a separator laminated between the anode and the cathode; an electrolyte impregnated in the cathode and the anode; and a case that contains the anode, the cathode, the anode current collector, the cathode current collector, the separator, and the electrolyte; wherein the anode contains an SiO-based material doped with Li, Mg, or a mixture thereof, and the K value calculated by the method for calculating battery capacity characteristics is 12 times or more, 20 times or more, 30 times or more, or 40 times or more of the weight fraction of the SiO-based material in the anode.

[0042] The negative electrode is a mixture of a negative electrode active material, a conductive material, and a binder. The negative electrode active material may include graphite and a SiO-based material.

[0043] The positive electrode is a mixture of a positive electrode active material, a conductive material, and a binder. The positive electrode active material may contain lithium.

[0044] For example, the negative electrode current collector is a Cu foil and the positive electrode current collector is an Al foil.

[0045] Working Example Two types of SiO-based materials with unknown compositions were prepared, and two types of negative electrodes were prepared so that the weight fraction of each SiO-based material was 0.1. Batteries were fabricated for each negative electrode, and battery sample 1 and battery sample 2 were prepared.

[0046] After battery sample 1 and battery sample 2 were fully charged to an SOC of 100%, XRD measurements were performed at a temperature of 60° C. every 4 hours, and data was collected for each battery.

[0047] From the XRD measurement data for each of battery sample 1 and battery sample 2, the peak value of Li, C Li , Li2C 12 The peak values ​​of C6(t) and LiC 12 The peak value of C 12 (t) was calculated respectively.

[0048] Calculated C Li , C6(t) and C 12 The K value was calculated for each of battery sample 1 and battery sample 2 by applying Equation 1 when t is sufficiently large with respect to C(t) (when the differential value is 0). 12 2 is a graph showing time series data for C6(t) and C 12 K was calculated at a value where (t) is parallel and t is 100 or greater.

[0049] Battery sample 1 had a calculated K value of 4.10, and battery sample 2 had a calculated K value of 1.14.

[0050] FIG. 3 is a graph showing the structural change of the negative electrodes of battery sample 1 and battery sample 2 over time. In FIG. 3, (a) is a graph for battery sample 1, and (b) is a graph for battery sample 2. In FIG. 3, the color variables refer to the peak values ​​in the XRD measurements, with red representing a large peak value and blue representing a small peak value. From FIG. 3, it can be seen that the change in LiC6 over time is slower in battery sample 2(b) than in battery sample 1(a). This means that the reaction with SiO was more successful, and the life characteristics of the electrode are not as good.

[0051] Fig. 4 is a graph showing the remaining life capacity according to cycles of battery sample 1 and battery sample 2. In Fig. 4, two each of battery sample 1 and battery sample 2 were manufactured, and the results of charging and discharging were shown.

[0052] As shown in FIG. 4, battery sample 1, which has a larger K value, exhibits a better remaining life capacity as a function of cycle number than battery sample 2.

[0053] Although the embodiment of the present invention has been described above, it is to be understood that the embodiment is merely illustrative and that various modifications and equivalent embodiments are possible. Therefore, the true technical scope of the present invention should be determined by the claims. [Industrial Applicability]

[0054] The method for calculating battery capacity characteristics of the present invention quantifies the reaction speed of graphite and SiO with Li to select SiO-based materials.

[0055] The method for calculating battery capacity characteristics of the present invention provides parameters indicating battery capacity characteristics related to the actual usage rate of SiO, which has low durability, and can contribute to the design of batteries with long life and stable cycle performance.

Claims

1. a negative electrode preparation step of preparing a negative electrode in which graphite and a test SiO-based material are mixed; a charging step of charging a battery including the negative electrode; The negative electrode was observed by XRD to determine the peak value of Li, C Ｌｉ , Li ２ C １２ The peak value of C ６ (t) and LiC １２ The peak value of C １２ A data collection step of collecting time series data for (t); Said C ６ (t) or the C １２ When the time differential value with respect to (t) is 0, Ｌｉ , said C ６ (t) and the C １２ a parameter calculation step of calculating a parameter K for a battery capacity characteristic based on the (t) value; A method for calculating battery capacity characteristics, comprising:

2. In the negative electrode preparation step, 2. The method of claim 1, wherein the negative electrode is prepared such that a weight fraction of the test subject SiO-based material in the negative electrode is 0.15 or less.

3. In the negative electrode preparation step, 2. The method for calculating battery capacity characteristics according to claim 1, wherein the test subject SiO-based material is SiO doped with Li, Mg or a mixture thereof.

4. In the charging step, 2. The method of claim 1, wherein the battery is fully charged so that the SOC is 100%.

5. In the data collection step, 5. The method of claim 4, wherein the state of charge of the battery is maintained at an SOC of 50% or more.

6. In the parameter calculation step, The method for calculating a battery capacity characteristic according to claim 1 , wherein the K is calculated by the following formula 1: [0010]

7. After the parameter calculation step, 7. The method of claim 6, further comprising: comparing the value of K with a weight fraction value of the SiO-based material to be tested in the negative electrode to determine a capacity characteristic state of the battery.

8. a negative electrode including graphite and a SiO-based material; a negative electrode current collector on which the negative electrode is applied; a positive electrode including lithium; a positive electrode current collector on which the positive electrode is applied; A separator laminated between the negative electrode and the positive electrode; an electrolyte impregnated in the positive electrode and the negative electrode; a case that accommodates the negative electrode, the positive electrode, the negative electrode current collector, the positive electrode current collector, the separator, and the electrolyte; The negative electrode includes a SiO-based material doped with Li, Mg, or a mixture thereof, and the value of K calculated by the method for calculating battery capacity characteristics according to claim 6 is 12 times or more a weight fraction of the SiO-based material in the negative electrode.

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