Method for analyzing quality of lithium sulfide in lithium-sulfur electrode

Abstract

The present invention relates to a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, which is a method for analyzing residual lithium compounds in a lithium-sulfide active material, and comprises the steps of: preparing an electrode including a positive electrode active material; charging and discharging the electrode to obtain first data on voltage according to capacity (specific capacity); and obtaining data according to an area value calculated by integrating a value (dQ / dV) obtained by differentiating a battery capacity (Q) according to the voltage (V) by the voltage (V) from the first data, and analyzing the data.

Description

Method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode

[0001] The present invention relates to a method for analyzing impurities, and more particularly, to a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode.

[0002] Lithium secondary batteries are widely used in everything from small electronic devices like mobile phones and laptops to larger devices like electric vehicles (EVs) and energy storage systems (ESS). As lithium secondary batteries' applications expand across all aspects of daily life, there is a growing demand for batteries that not only deliver high energy density and long lifespan, but also ensure stability. However, lithium secondary batteries have a theoretical capacity of only about 250 mAh / g, making them difficult to use in devices that require high energy densities, such as electric vehicles and large-capacity power storage systems.

[0003] To overcome these limitations, lithium-sulfur (Li-S) batteries, which can achieve a high theoretical capacity density of 2,600 mAh / kg, are attracting attention. These lithium-sulfur batteries use sulfur-based compounds with disulfide bonds as the positive electrode active material and materials containing lithium metal or lithium ions as the negative electrode active material.

[0004] However, the electrolytes used in these batteries were mostly liquid electrolytes using organic solvents. However, these liquid electrolytes constantly raised safety issues, such as electrolyte leakage and fire hazards. Therefore, strict packaging was required, limiting the ability to increase energy density beyond a certain level.

[0005] This has led to the need for all-solid-state batteries, which utilize solid electrolytes rather than liquid ones. Because all-solid-state batteries eliminate the need for organic solvents (liquid electrolytes), they enable safer cell production.

[0006] In addition, since inorganic solid electrolytes do not decompose and are stable over a wide voltage range, they enable the use of high-voltage electrode materials that were difficult to use in existing liquid electrolytes.

[0007] These solid electrolytes are divided into oxide-based solid electrolytes and sulfide-based solid electrolytes. Since sulfide-based solid electrolytes have higher ionic conductivity than oxide-based solid electrolytes, interest in sulfide-based solid electrolytes is increasing.

[0008] The main raw material of sulfide-based solid electrolytes is lithium sulfide (Li2S). In lithium-sulfur batteries, the quality of lithium sulfide affects the production yield and performance of the solid electrolyte. Specifically, it was confirmed that when the Li2CO3 content in lithium sulfide increased from 1 to 10 wt%, the production yield of the solid electrolyte decreased from 97% to 80%. Furthermore, it was confirmed that the type of compound (Li2O / Li2CO3) related to the oxygen content in Li2S affected the performance of the solid electrolyte.

[0009] However, the specific quantification of trace impurities within lithium sulfide (Li2S) is difficult. Each substance within lithium sulfide exhibits capacity within a specific voltage range, and among the impurities, Li2O exhibits capacity around 3.5 V. Therefore, research is needed on methods for analyzing the quality of lithium sulfide by determining the content of trace impurities based on this.

[0010] According to one embodiment of the present invention, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode provides a method for quantifying the amount of trace impurities in lithium sulfide (Li2S).

[0011] According to one embodiment of the present invention, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode is a method for analyzing a residual lithium compound in a lithium-sulfur active material, and may include a step of preparing an electrode including a positive electrode active material, a step of charging and discharging the electrode to obtain first data on voltage (Voltage) according to capacity (Specific Capacity), and a step of obtaining and analyzing data according to an area value calculated by integrating a value (dQ / dV) obtained by differentiating a battery capacity (Q) according to the voltage (V) with respect to the voltage (V) from the first data.

[0012] In one embodiment, the step of obtaining and analyzing the data may include a step of first processing the first data to obtain second data for a value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) of the electrode with respect to the voltage (V), and a step of second processing the second data to obtain third data for an area value calculated by integrating a value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V).

[0013] In one embodiment, the method may include calculating the content of the residual lithium compound from the third data according to Equation 1 below.

[0014] <Formula 1>

[0015] 0.00665 < Y = aX + b < 0.00744

[0016] (In the above equation 1, a is 2.88689 × 10 -4 , b can be 0.00563, Y means the dQ / dV area of ​​the Li2O electrode, and X means the amount of Li2O in lithium sulfide.)

[0017] In one embodiment, the electrode includes lithium sulfide, a conductive material, and a binder, and the content of the lithium sulfide may be 55 to 75 wt% based on 100 wt% of the total amount of the lithium sulfide, the conductive material, and the binder. In one embodiment, the step of obtaining the first data may include charging and discharging the electrode under charge and discharge conditions in a range of 1.5 V to 3.9 V at a charge and discharge rate of 0.01 C-rate, thereby obtaining data on voltage according to capacity.

[0018] In one embodiment, the step of obtaining the second data may include a step of differentiating the first data by the battery capacity (Q) into the voltage (V), and converting the first data into a value (dQ / dV) obtained by differentiating the X-axis with the voltage (Voltage) and the Y-axis with the battery capacity (Q) into the voltage (V). In one embodiment, the step of obtaining the second data may include a step of extracting a value (dQ / dV) obtained by differentiating the battery capacity (Q) into the voltage (V) when the voltage (Voltage) of the electrode is in the range of 3.4 to 3.7 Voltage.

[0019] In one embodiment, the step of obtaining the third data may include a step of processing the second data by obtaining a graph for the section of 3.4 V to 3.7 V of the second data using an Origin program, and integrating the graph to obtain the absolute area of ​​each graph. In one embodiment, the residual lithium compound may be lithium oxide.

[0020] In one embodiment, the lithium oxide may be Li2O. In one embodiment, the content of the residual lithium compound may be 0 to 10 wt% based on 100 wt% of lithium sulfide.

[0021] According to another embodiment of the present invention, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode is a method for analyzing a residual lithium compound in a lithium-sulfur active material, comprising the steps of: preparing an electrode including a positive electrode active material; charging and discharging the electrode to obtain first data on voltage (Voltage) according to capacity (Specific Capacity); processing the first data primarily to obtain second data on a value (dQ / dV) obtained by differentiating a battery capacity (Q) according to voltage (V) of the electrode with respect to voltage (V); and processing the second data secondary to obtain third data on an area value calculated by integrating a value (dQ / dV) obtained by differentiating a battery capacity (Q) according to voltage (V) with respect to voltage (V), and calculating a content of a residual lithium compound from the third data according to Equation 2 below.

[0022] <Formula 2>

[0023] 0.00300 < Y = aX + b < 0.00800

[0024] (In the above equation 2, a is 4.71536 × 10 -4 , b is 0.00534, Y represents the dQ / dV area of ​​the Li2O electrode, and X represents the amount of Li2O in lithium sulfide.)

[0025] In one embodiment, the content of the residual lithium compound may be 0 to 5 wt% based on 100 wt% of lithium sulfide. In one embodiment, the residual lithium compound may be lithium oxide. In one embodiment, the lithium oxide may be Li2O.

[0026] According to one embodiment of the present invention, a method for analyzing the quality of lithium sulfide for a lithium-sulfur secondary battery provides a method for quantifying the amount of trace impurities in lithium sulfide (Li2S) through an electrochemical characteristic evaluation method.

[0027] Figure 1 shows a charge / discharge graph of a lithium-sulfur electrode according to one embodiment of the present invention.

[0028] Figure 2 is a processed graph of the charge / discharge graph of the lithium-sulfur electrode of Figure 1.

[0029] Figure 3 is an enlarged graph of the dQ / dV area around 3.4 to 3.7 Voltage in the charge / discharge graph of Figure 2.

[0030] Figure 4 is a graph showing the calibration curve for the integral value for the dQ / dV area range from 3.4 to 3.7 V of Figure 3 calculated using the method below.

[0031] Figures 5a and 5b are graphs showing the calibration curve according to the content of lithium oxide, a residual lithium compound, based on the measured values ​​of Figure 4.

[0032] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0034] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0035] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0036] In one embodiment of the present invention, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode may be a method for analyzing a residual lithium compound, which is an impurity in a lithium-sulfur material. Specifically, the method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode includes the steps of preparing an electrode including a positive electrode active material, obtaining first data on voltage (Voltage) according to capacity (Specific Capacity) by charging and discharging the electrode, and obtaining and analyzing data according to an area value calculated by integrating a value (dQ / dV) obtained by differentiating a battery capacity (Q) according to the voltage (V) with respect to the voltage (V) from the first data.

[0037] The step of preparing an electrode including a positive electrode active material may include lithium sulfide (Li2S), a conductive material, and a binder. In one embodiment, the lithium sulfide (Li2S) may be a material including a residual lithium compound. Specifically, the lithium sulfide (Li2S) utilized in the electrode may include a predetermined range of impurities. Depending on the content of the impurities in the lithium sulfide (Li2S), when applied to a secondary battery, a significant difference may occur in the efficiency of the battery. Accordingly, it is necessary to quantify and measure the content of the residual lithium compound, which is an impurity included in the lithium sulfide (Li2S).

[0038] In one embodiment, the content of lithium sulfide (Li2S) may be 55 to 75 wt% based on 100 wt% of the total amount of lithium sulfide (Li2S), the conductive material, and the binder. Specifically, the content of lithium sulfide may be 60 to 70 wt%. By manufacturing an electrode in which the content of lithium sulfide (Li2S) satisfies the above-described range, a positive electrode applicable to a lithium sulfur battery can be manufactured.

[0039] In one embodiment, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode can be performed using an electrochemical method. Specifically, the electrochemical method can calculate the content of lithium compounds remaining in the lithium sulfide based on data obtained by charging and discharging the electrode.

[0040] The step of obtaining and analyzing data according to the area value calculated by integrating the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V) from the first data includes the step of first processing the first data to obtain second data for the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V) of the electrode, and the step of obtaining third data for the area value calculated by integrating the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V).

[0041] The step of obtaining first data on voltage according to specific capacity by charging and discharging the electrode may be a step of generating a charge and discharge graph after charging and discharging the electrode. Specifically, the first data may be data on voltage according to the capacity by charging and discharging the electrode under charge and discharge conditions in the range of 1.5 V to 3.9 V at a charge and discharge rate of 0.01 C-rate.

[0042] In one embodiment, in the step of obtaining the first data, the voltage may satisfy a range of 2.8 to 4.0 V. More specifically, the second data may satisfy a range of 3.0 to 3.9 V.

[0043] In the step of obtaining the first data, when the voltage satisfies the aforementioned range, quantitative data for quality analysis of lithium sulfide in the lithium-sulfur electrode can be prepared. If the voltage exceeds the upper limit of the aforementioned range, excessive overvoltage is applied, which is expected to result in the development of capacity of impurities, resulting in reduced analysis accuracy and potential electrolyte decomposition issues.

[0044] The step of first processing the first data to obtain second data for the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) of the electrode may be a step of differentiating the first data to obtain second data. Specifically, the first data, which is a result value for the charge / discharge graph of the electrode, may be differentiated by differentiating the micro-battery capacity (Q) with respect to the voltage (V), and the second data may be obtained by converting the X-axis to voltage (V) and the Y-axis to a value (dQ / dV) obtained by differentiating the battery capacity (Q) with respect to the voltage (V).

[0045] In one embodiment, the step of obtaining the second data may be a step of obtaining the first data by processing the charge / discharge graph into a dQ / dV graph, and then processing the data using an automatic calculation provided by the charge / discharge program. Specifically, the step of processing the second data may be a step of obtaining the voltage according to the capacity in the charge / discharge program, and then providing the value obtained by differentiating the capacity by the voltage through calculation within the program.

[0046] In one embodiment, the step of obtaining the second data may include a step of extracting a value (dQ / dV) obtained by differentiating the battery capacity (Q) with respect to the voltage (V) when the voltage (Voltage) of the electrode is in the range of 3.4 to 3.7 Voltage. In the step of obtaining the second data, when the voltage of the electrode satisfies the above-described range, it can be confirmed that the residual lithium compound in the lithium sulfide, for example, Li2O, reacts and the area value of the residual lithium compound in the lithium sulfide increases as the content of the residual lithium compound increases.

[0047] In the step of obtaining the second data, when extracting data in a region where the voltage of the electrode is outside the lower or upper limit of the aforementioned range, there is a problem in that quantifiable data cannot be extracted according to the change in the content of residual lithium compounds in lithium sulfide.

[0048] The step of obtaining third data for the area value calculated by integrating the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V) by secondary processing the second data means data derived by integrating the data for the differential value of the second data and deriving the area value for the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage with respect to the voltage (V) within the second data.

[0049] In one embodiment, the step of obtaining the third data may be a step of obtaining the second data by processing the second data using an Origin program to obtain a graph for the section of 3.4 V to 3.7 V of the second data, and integrating the graph to obtain the absolute area of ​​each graph.

[0050] In one embodiment, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode may include a step of calculating the content of a residual lithium compound from third data according to Equation 1 below.

[0051] <Formula 1>

[0052] 0.00665 < Y = aX + b < 0.00744

[0053] (In the above equation 1, a is 2.88689 × 10 -4 , b can be 0.00563, Y means the dQ / dV area of ​​the Li2O electrode, and X means the amount of Li2O in lithium sulfide.)

[0054] The above equation 1 represents an index for the amount of Li2O in lithium sulfide. Specifically, the lower limit of the equation 1 may refer to the dQ / dV area of ​​a 3 wt% Li2O electrode, and the upper limit of the equation 1 may correspond to the dQ / dV area of ​​a 4 wt% Li2O electrode. Accordingly, it can be confirmed that the amount of Li2O in the lithium sulfide used in the electrode of the present invention is approximately between 3 wt% and 4 wt%. In this way, the concentration of Li2O in lithium sulfide can be predicted through the equation 1.

[0055] The above equation 1 may be an indicator for determining the content of residual lithium compounds in lithium sulfide when the content of residual lithium compounds in lithium sulfide is 0 to 10 wt%. The above equation 1 may satisfy 0.00454 to 0.00916. Specifically, the above Y value may represent the minimum and maximum values ​​of the dQ / dV area. If the above equation 1 is outside the above-mentioned range, the reliability may be reduced.

[0056] In one embodiment, a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode may include a step of calculating the content of a residual lithium compound from third data according to Equation 2 below.

[0057] <Formula 2>

[0058] 0.00300 < Y = ax + b < 0.00800

[0059] (In the above equation 2, a is 4.71536 × 10 -4 , b is 0.00534, Y represents the dQ / dV area of ​​the Li2O electrode, and X represents the amount of Li2O in lithium sulfide.)

[0060] The above equation 2 may be an indicator for determining the content of residual lithium compounds in lithium sulfide when the content of residual lithium compounds in lithium sulfide is 0 to 5 wt%. The above equation 2 may satisfy 0.00300 to 0.00800, specifically 0.00454 to 0.00760. Specifically, the Y value may represent the minimum and maximum values ​​of the dQ / dV area. If the above equation 2 is outside the above-mentioned range, the reliability may be reduced.

[0061]

[0062] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0063]

[0064] <Experimental Example>

[0065] 1. Manufacturing of Li-S electrodes

[0066] A positive electrode was manufactured with an active material layer containing lithium sulfide (Li2S), a conductive material, and a binder in a ratio of 65:30:5, totaling 0.1 g. Super C was used as the conductive material, and polytetrafluoroethylene (PTEE) was used as the binder. In addition, a lithium metal negative electrode with a thickness of 200 μm was used as the negative electrode. The positive electrode size was 14 pi, and the negative electrode size was 16 pi.

[0067] A Li-S cathode was prepared using an electrolyte solution containing 1.0 M concentration of bis(trifuloromethane) sulfonamide lithium salt (LiTFSI) dissolved in a solvent containing dimethoxyethane / 1,3-dioxolane (DME / DOL) mixed in a volume ratio of 1:1 and 2.0 wt% of LiNO3 added.

[0068]

[0069] 2. Derivation of charge-discharge graph of Li-S electrode

[0070] The lithium-sulfur electrode was charged once at 0.01 C in the voltage range of 1.5 V to 3.9 V. Thereafter, the graph shape was derived through charging alone without a separation process. Figure 1 shows a charge-discharge graph of a lithium-sulfur electrode according to an embodiment of the present invention.

[0071] Referring to Fig. 1, a charge-discharge graph is shown when a lithium-sulfur electrode is charged at 0.01 C in a voltage range of 1.5 V to 3.9 V. Specifically, it is a graph of voltage according to the specific capacity of the lithium-sulfur electrode.

[0072] In the charge / discharge graph modification above, a tendency for quantification in the overvoltage tendency or capacity expression section was observed, but it was confirmed that there was no one-to-one matching as the Li2O concentration increased. However, since a specific tendency was confirmed to exist around 3.4 to 3.7 V in the charge / discharge graph above, the graph was further processed as shown below.

[0073]

[0074] 3. Primary processing of the charge-discharge graph of the Li-S electrode

[0075] Figure 2 is a processed graph of the charge / discharge graph of the lithium-sulfur electrode of Figure 1.

[0076] Referring to Fig. 2, this is a graph that is differentiated from the charge / discharge graph of the lithium-sulfur electrode of Fig. 1 using a charge / discharge program. Specifically, Fig. 2 shows the dQ / dV area according to the voltage of the lithium-sulfur electrode. dQ / dV refers to a value obtained by differentiating the battery capacity (Q) with respect to the voltage (V), and the dQ / dV area according to the voltage may refer to the capacity at which Li2O in lithium sulfide reacts by integrating the differential value.

[0077] According to Fig. 2, it was confirmed that a tendency was observed around 3.4 to 3.7 Voltage where Li2O is expected to react, depending on the Li2O content.

[0078] Figure 3 is an enlarged graph of the dQ / dV area around 3.4 to 3.7 Voltage in the charge / discharge graph of Figure 2.

[0079] Referring to Figure 3, it was confirmed that the dQ / dV area increased around the voltage of 3.4 to 3.7, where Li2O is expected to react, depending on the Li2O content. In this regard, a linear calibration curve was confirmed using the method below.

[0080]

[0081] 4. Secondary processing of the charge-discharge graph of the first-processed Li-S electrode

[0082] Figure 4 is a graph showing the calibration curve for the integral value for the dQ / dV area range from 3.4 to 3.7 V of Figure 3 calculated using the method below.

[0083] Referring to Fig. 4, the integral value for the dQ / dV area according to the Li2O content was measured. Specifically, a linear trend can be confirmed when the Li2O content is 0 to 5 wt%, but it can be confirmed that it has a saturated value at a concentration above a certain level. More specifically, Fig. 4 is a graph according to each Li2O concentration of Fig. 3, which uses the integration function among the Origin program functions to express the dQ / dV area as an absolute value.

[0084] Figures 5a and 5b are graphs showing the calibration curve according to the content of lithium oxide, a residual lithium compound, based on the measured values ​​of Figure 4.

[0085] Figure 5a is a calibration curve graph when the content of residual lithium compound is 0 to 10 wt%, and Figure 5b is a calibration curve graph when the content of residual lithium compound is 0 to 5 wt%.

[0086] Referring to Figures 5a and 5b, the integral value for the dQ / dV area according to the Li2O content was measured. Specifically, a linear trend can be confirmed in the Li2O content range of 0 to 5 wt%, but it can be confirmed that the value is saturated at a concentration above a certain level.

[0087] Reliability value R1 according to data for each when the content of residual lithium compound is 0 to 10 wt% 2 Looking at it, it can be confirmed that it is high at 0.79463. The reliability value R2 according to the data for each when the content of residual lithium compound is 0 to 5 wt% 2 If we look at it, we can see that it is very high at 0.97691.

[0088] Like this, R1 2 R2 than the value 2 As can be seen from this high value, it was confirmed that the reliability was higher when the content of residual lithium compounds was 0 to 5 wt% than when it was 0 to 10 wt%.

[0089]

[0090] Table 1 below shows the absolute value of the area according to the content of lithium sulfide and Li2O. In Table 1 below, the content of lithium sulfide and Li2O, the absolute value of the area, R 2 The values ​​were measured using the following method.

[0091] Li2S + Li2O content analysis: Li2S was mixed with Li2O at a certain concentration, and for unknown samples, the Li2O content was predicted by comparing the area values.

[0092] Absolute value of area: The area of ​​the dQ / dV graph was expressed as an absolute value using the integration function in the Origin program.

[0093] R1 2 Value and R2 2 Value: R1 2 The values ​​are calculated from the Li2O content in the range of 0 to 10 wt%, and R2 2 The values ​​represent the reliability of the values ​​calculated in the range of 0 to 5 wt% of Li2O content. R1 2 Value and R2 2 The values ​​were obtained by plotting the area according to Li2O concentration in a scatter graph using the Origin program and using the linear fitting function.

[0094] Number Component Li2O Content [wt%] dQ / dV Area [unit: mAh] R1 2 Satisfies equation 1R2 2 Formula 2 Satisfies 1 Li2S 0 0.005 26 0.79 43 4 O 0.97 7 4 3 O 2 Li2S + Li2O < 10.005 67 OO 3 Li2S + Li2O 10.005 8 6 OO 4 Li2S + Li2O 20.006 2 1 OO 5 Li2S + Li2O 30.006 6 5 OO 6 Li2S + Li2O 40.007 4 OO 7 Li2S + Li2O 50.007 6 0 OO 8 Li2S + Li2O 70.006 8 1 OX 9 Li2S + Li2O 100.008 5 4 OX * Formula 1 : y = (2.88689 * 10 -4 )x + 0.00563**Equation 2: y=(4.71536*10 -4 )x + 0.00534

[0095] Looking at Table 1 above, looking at the dQ / dV area according to the Li2O content in addition to lithium sulfide in the anode, R1 is observed when the Li2O content is in the range of 0 to 10 wt%. 2 It was confirmed that the value was approximately 0.79434, and R2 was in a trace range such as 0 to 5 wt% of Li2O content. 2It was confirmed that the reliability value was higher when the Li2O content was trace, with a value of approximately 0.97743. In this way, the method for analyzing the quality of lithium sulfide according to the embodiment of the present invention more easily confirmed the quality of the electrode when the content of Li2O in lithium sulfide was trace, such as 5 wt% or less.

[0096]

[0097] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A method for analyzing residual lithium compounds in lithium-sulfur active materials, A step of preparing an electrode including a positive electrode active material; A step of obtaining first data on voltage according to capacity (Specific Capacity) by charging and discharging the above electrode; and A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, comprising a step of obtaining data according to an area value calculated by integrating a value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) from the first data with respect to the voltage (V).

2. In paragraph 1, The steps of obtaining and analyzing the above data are: A step of first processing the first data to obtain second data for the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage of the electrode by the voltage (V); and A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, comprising a step of obtaining third data for an area value calculated by integrating a value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V) by performing secondary processing on the second data.

3. In paragraph 2, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, comprising a step of calculating the content of residual lithium compound from the third data according to the following Equation 1. <Formula 1> 0.00665 < Y = aX + b < 0.00744 (In the above equation 1, a is 2.88689 × 10 -4 , b can be 0.00563, Y means the dQ / dV area of ​​the Li2O electrode, and X means the amount of Li2O in lithium sulfide.) 4. In paragraph 1, The above electrode comprises lithium sulfide, a conductive material, and a binder, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the content of lithium sulfide is 55 to 75 wt% based on 100 wt% of the total amount of lithium sulfide, conductive material, and binder.

5. In paragraph 1, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the step of obtaining the first data comprises a step of charging and discharging the electrode under charge and discharge conditions in the range of 1.5 V to 3.9 V at a charge and discharge rate of 0.01 C-rate, thereby obtaining data on voltage according to capacity.

6. In paragraph 2, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the step of obtaining the second data includes the step of differentiating the first data by differentiating the microcapacity (Q) by the voltage (V), and converting the first data into a value (dQ / dV) in which the X-axis is voltage and the Y-axis is the battery capacity (Q) differentiated by the voltage (V).

7. In paragraph 2, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the step of obtaining the second data includes a step of extracting a value (dQ / dV) obtained by differentiating the battery capacity (Q) by the voltage (V) when the voltage of the electrode is in the range of 3.4 to 3.7 Voltage.

8. In paragraph 2, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the step of obtaining the third data comprises a step of obtaining the second data by processing the second data using an Origin program to obtain a graph for a section of 3.4 V to 3.7 V of the second data, and integrating the graph to obtain the absolute area of ​​each graph.

9. In paragraph 1, The above residual lithium compound is a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode which is lithium oxide.

10. In paragraph 9, The above lithium oxide is a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the lithium oxide is Li2O.

11. In paragraph 1, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the content of the residual lithium compound is 0 to 10 wt% based on 100 wt% of lithium sulfide.

12. A method for analyzing residual lithium compounds in lithium-sulfur active materials, A step of preparing an electrode including a positive electrode active material; A step of obtaining first data on voltage according to capacity (Specific Capacity) by charging and discharging the above electrode; A step of first processing the first data to obtain second data for the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage of the electrode by the voltage (V); and It includes a step of obtaining third data for the area value calculated by integrating the value (dQ / dV) obtained by differentiating the battery capacity (Q) according to the voltage (V) with respect to the voltage (V) by performing secondary processing on the second data, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, comprising a step of calculating the content of residual lithium compound from the third data according to the following Equation 2. <Formula 2> 0.00300 < Y = ax + b < 0.00800 (In the above equation 2, a is 4.71536 × 10 -4 , b is 0.00534, Y represents the dQ / dV area of ​​the Li2O electrode, and X represents the amount of Li2O in lithium sulfide.) 13. In paragraph 12, A method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the content of the residual lithium compound is 0 to 5 wt% based on 100 wt% of lithium sulfide.

14. In paragraph 12, The above residual lithium compound is a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode which is lithium oxide.

15. In paragraph 12, The above lithium oxide is a method for analyzing the quality of lithium sulfide in a lithium-sulfur electrode, wherein the lithium oxide is Li2O.

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