Generation method of OCV curve of battery mixed electrode

Abstract

The invention provides a method for generating an OCV curve of a battery mixed electrode. The method comprises the following steps: testing half-battery open-circuit voltage OCP and specific capacity Q corresponding to a single raw material corresponding to a to-be-tested mixed electrode; interpolating an open circuit voltage (OCP) of the half-cell into a function of a state of lithium insertion (SOL); calculating an SOL sequence under a target open-circuit voltage OCV sequence of a single raw material of the mixed electrode and a corresponding specific capacity sequence; adding the specific capacity sequence according to the weight of the mixed weight ratio to obtain the specific capacity sequence of the mixed electrode; and calculating the SOC sequence of the mixed electrode. Based on the thermodynamic principle, a more stable and reliable hybrid electrode OCV prediction result is obtained through mathematical model calculation.

Description

Technical Field

[0001] This application relates to the technical field of battery electrodes, and particularly to a method for generating an OCV curve of a battery hybrid electrode. Background Art

[0002] In the fields of lithium-ion batteries, sodium-ion batteries, especially in the field of lithium-ion battery chemical power sources, the selection and optimization of electrode materials are key links in improving battery performance. To comprehensively utilize the advantages of different materials, such as high capacity, high rate performance, high safety, etc., the concept of hybrid electrodes has been increasingly emphasized. A hybrid electrode is usually composed of two or more active materials mixed in a certain proportion, and each material has its unique properties. Therefore, the advantages of various materials can be fully utilized, and the hybrid electrode battery can have characteristics such as higher energy density and high power density through synergy.

[0003] Open circuit voltage (OCV), as one of the important parameters for evaluating the thermodynamic state and working characteristics of a battery, directly reflects the thermodynamic characteristics of the positive and negative electrode materials of the battery, and is the basis for understanding the battery energy storage mechanism, predicting the battery energy density, evaluating the battery health state, and designing the battery management system. Therefore, accurately obtaining the OCV characteristics of electrode materials, especially the OCV characteristics of hybrid electrodes, is crucial for battery material research and development and battery performance optimization.

[0004] In the related art, when adjusting the mixing ratio of each material in the hybrid electrode, it is necessary to re-conduct the OCV experimental test, which will lead to the following problems: it is difficult to quickly screen and optimize the hybrid electrode ratio, restricting the R & D progress. At the same time, a large amount of raw material cost and time cost are required, and it is difficult to cover all possible mixing ratios in actual tests. The test results are also affected by various factors and have certain deviations, making it difficult to ensure the accuracy and reliability of each test data.

[0005] In summary, how to quickly and accurately obtain the OCV of the hybrid electrode is an urgent problem in the field. Summary of the Invention

[0006] Based on this, this application aims to provide a brand-new method for generating an OCV curve of a battery hybrid electrode based on thermodynamic principles and calculated through a mathematical model. There is no need to repeat the experimental test for each mixing ratio of the hybrid electrode. Only by pre-testing and obtaining the OCV curves of each constituent raw material in the hybrid electrode, the OCV curve of the hybrid electrode at any mixing ratio can be accurately predicted through a specific calculation method, and it is applicable to both the positive electrode and the negative electrode including the mixing of two or more active materials.

[0007] This application provides a method for generating an OCV curve of a battery hybrid electrode, including:

[0008] Fabricate half-cells of each constituent raw material in the composite electrode;

[0009] Test the open-circuit voltage OCP and the corresponding specific capacity Q of the half-cells of each constituent raw material;

[0010] Interpolate the open-circuit voltage OCP of the half-cells corresponding to the single raw materials in the composite battery into a function of the lithium intercalation state SOL;

[0011] Calculate the SOL sequence and the corresponding specific capacity sequence under the target open-circuit voltage OCV sequence for the single raw materials in the composite electrode;

[0012] Add the specific capacity sequences according to the mixing weight ratio weights to obtain the specific capacity sequence of the composite electrode;

[0013] Calculate the state of charge SOC sequence of the composite electrode.

[0014] In some embodiments, the function of the lithium intercalation state SOL includes two steps.

[0015] In the first step, extract the maximum specific capacity Q max , and obtain the SOL sequence.

[0016] Further, when it is in the discharge state, the SOL is calculated using the discharge data at this time, and the formula for the SOL sequence is,

[0017]

[0018] where Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity.

[0019] Further, when it is in the charge state, the SOL is calculated using the charge data at this time, and the formula for the SOL sequence is,

[0020]

[0021] where Q is the charge specific capacity, with the unit of mAh / g, and Q max is the maximum charge specific capacity.

[0022] In the second step, interpolate the calculated SOL sequence into a function of the open-circuit voltage OCP of the half-cell, denoted as SOL(OCP).

[0023] In some embodiments, the above interpolation method includes one of linear interpolation, nearest-neighbor interpolation, and Lagrange interpolation.

[0024] In some embodiments, calculating the SOL sequence under the target open circuit voltage OCV sequence of the single raw material of the hybrid electrode includes substituting the target open circuit voltage OCV of the single raw material of the hybrid electrode into the aforementioned lithium insertion state SOL function to obtain SOL object ,

[0025] SOL object =SOC(OCV).

[0026] In some embodiments, the corresponding specific capacity sequence Q under the SOL sequence is calculated interp , and its calculation formula is,

[0027] Q interp =SOL objet *Q max ,

[0028] Among them, the Q max is the maximum specific capacity.

[0029] In some embodiments, the specific capacity sequence under the SOL sequence is added according to the mixing weight ratio to obtain the specific capacity sequence Q of the mixed electrode. mix , and its calculation formula is,

[0030]

[0031] Among them, w i is the weight proportion of the i-th raw material, Indicates the SOL corresponding to the i-th raw material object Specific capacity sequence Q under the sequence interp , the unit is mAh / g, n is the sum of the number of types of single raw materials in the mixed electrode, Q mix is the specific capacity of the hybrid electrode at the target OCV, in mAh / g.

[0032] In the present application, the mixed electrode refers to an electrode formed by mixing two or more active materials in a certain proportion, and is not limited to a positive electrode or a negative electrode.

[0033] The positive electrode includes two or more positive electrode active materials, and further, the positive electrode active materials include at least two of lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and ternary materials (nickel cobalt manganese oxide NCM and nickel cobalt aluminum oxide NCA), preferably ternary nickel cobalt manganese oxide and lithium manganese oxide, or ternary nickel cobalt manganese oxide, lithium manganese oxide and lithium iron phosphate, wherein the ternary nickel cobalt manganese oxide is further preferably LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0034] The negative electrode comprises more than two kinds of negative electrode active materials. Further, the negative electrode active materials include at least two of graphite, silicon, hard carbon, and soft carbon, preferably graphite and silicon.

[0035] In some embodiments, the state of charge (SOC) of the hybrid electrode is calculated. mix Sequence, and the calculation formula is

[0036]

[0037] where max is the function to find the maximum value of Q. mix Maximum value function.

[0038] In some embodiments, during the process of testing the open circuit voltage (OCP) and specific capacity (Q) of the half-cell corresponding to a single raw material of the hybrid electrode of the battery under test, the test is divided into a negative electrode test method and a positive electrode test method.

[0039] Further, the negative electrode test method includes: constant current discharge to the lower limit voltage and then static, constant current and constant voltage charge to the upper limit voltage. Wherein, the current of the constant current discharge is 0.02C, the lower limit voltage is 5mV, the static time is 30min, the charging current of the constant current and constant voltage charge is 0.02C, and the upper limit voltage is 1.5V.

[0040] Further, the positive electrode test method includes: constant current and constant voltage charge to the upper limit voltage and then static, constant current discharge to the lower limit voltage. Wherein, the charging current of the constant current and constant voltage charge is 0.02C, the upper limit voltage is 4.3V, the static time is 30min, the current of the constant current discharge is 0.02C, and the lower limit voltage is 2.8V.

[0041] In this application, the number of target interpolation calculation data points is N, and N>50. Further, N≥100, for example, 100 - 300.

[0042] In this application, the following calculation formula is used to calculate the root mean square error between the open circuit voltage curve and the curve obtained from actual test under the same conditions to evaluate the effect of this method.

[0043]

[0044] where exp i is the data obtained from the experimental test OCV corresponding to the i-th raw material, and modeli i is the calculated OCV data corresponding to the i-th raw material. N is the number of target interpolation calculation data points. Generally, N>50. Further, N≥100, for example, 100 - 300.

[0045] In this application, the value of the root mean square error is less than 0.005V.

[0046] Compared with the prior art, the present application has the following advantages:

[0047] (1) The method for generating the open circuit voltage (OCV) curve of the battery hybrid electrode provided by the present application is calculated based on a mathematical model. The result is not affected by the fluctuations of experimental conditions, and can provide a more stable and reliable OCV prediction result. The calculated curve coincides with the measured curve, and the root mean square error < 0.005V, which helps to more accurately evaluate the performance of the hybrid electrode.

[0048] (2) The present application can theoretically predict the OCV of the hybrid electrode at any mixing ratio, enabling researchers to more comprehensively evaluate the performance potential of different mixing ratio schemes, providing a more powerful tool for optimizing the mixing ratio of the hybrid electrode, while reducing the experimental cost and improving the R & D efficiency. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments of the present application will be briefly introduced below.

[0050] Figure 1 It is a flowchart of the method for generating the open circuit voltage curve of the battery hybrid electrode according to an embodiment of the present application.

[0051] Figure 2 It is a diagram of Embodiment 1 showing the SOC-OCV curve of a battery cell using a hybrid electrode (mix) of graphite (C) and silicon (Si). The horizontal axis is SOC, and the vertical axis is OCV (V). The dotted line marked with circles is the calculated SOC-OCV curve of the hybrid electrode, the solid line is the SOC-OCV curve of the hybrid electrode obtained by experimental testing, the dashed line represents the SOC-OCV of graphite in the hybrid electrode, and the dotted line represents the SOC-OCV curve of silicon in the hybrid electrode.

[0052] Figure 3 It is a diagram of Embodiment 2 showing the SOC-OCV curve of a battery cell using a hybrid electrode (mix) of ternary lithium nickel cobalt manganese oxide (NCM) and lithium manganese oxide (LMO). The horizontal axis is SOC, and the vertical axis is OCV (V). The dotted line marked with circles is the calculated SOC-OCV curve of the hybrid electrode, the solid line is the SOC-OCV curve of the hybrid electrode obtained by experimental testing, the dashed line represents the SOC-OCV of NCM in the hybrid electrode, and the dotted line represents the SOC-OCV curve of LMO in the hybrid electrode.

[0053] Figure 4FIG. 3 is a graph showing the SOC-OCV curve of a battery cell with a mixed electrode (mix) using lithium nickel cobalt manganese oxide (NCM) and lithium manganese oxide (LMO) in Example 3. The horizontal axis is SOC, and the vertical axis is OCV (V). The dotted line with circular markers is the calculated SOC-OCV curve of the mixed electrode, the solid line is the experimentally measured SOC-OCV curve of the mixed electrode, the dashed line represents the SOC-OCV of NCM in the mixed electrode, and the dotted line represents the SOC-OCV curve of LMO in the mixed electrode.

[0054] Figure 5 FIG. 4 is a graph showing the SOC-OCV curve of a battery cell with a mixed electrode (mix) using lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide (LMO), and lithium iron phosphate (LFP) in Example 4. The horizontal axis is SOC, and the vertical axis is OCV (V). The dotted line with circular markers is the calculated SOC-OCV curve of the mixed electrode, the thick solid line is the experimentally measured SOC-OCV curve of the mixed electrode, the dashed line represents the SOC-OCV of NCM in the mixed electrode, the dotted line represents the SOC-OCV curve of LMO in the mixed electrode, and the thin solid line represents the SOC-OCV curve of LFP in the mixed electrode. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application. It should be understood that the specific embodiments described are only used to explain the present application and are not used to limit the present application.

[0056] To facilitate the understanding of the embodiments of the present application, the terms involved in the embodiments of the present application will be explained below.

[0057] A mixed electrode means that the positive electrode and / or the negative electrode uses a mixed electrode material. For example, the positive electrode includes two or more positive electrode active materials, and / or the negative electrode includes two or more negative electrode active materials. The positive electrode active materials include, but are not limited to, lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and ternary materials (lithium nickel cobalt manganese oxide NCM and lithium nickel cobalt aluminum oxide NCA). The negative electrode active materials include, but are not limited to, graphite, silicon, hard carbon, and soft carbon. The battery core of the mixed electrode battery can be a sodium ion battery core, a lithium ion battery core, or other types of secondary battery cores.

[0058] SOC, short for State of Charge, which is the state of charge of the battery. The fully discharged state is when the battery discharges to the cut-off voltage, and at this time, SOC = 0%; the fully charged state is when the battery charges to the cut-off voltage, and at this time, SOC = 100%.

[0059] OCV, short for open circuit voltage, which is the open circuit voltage of the battery, referring to the potential difference between the positive and negative electrodes of the battery in a non-working state. OCP is the open circuit potential of a single electrode.

[0060] SOL, short for State of Lithiation, which is the state of lithium intercalation of the battery and describes the degree of lithium ion intercalation in the positive or negative electrode material.

[0061] The OCV curve is usually expressed as a function of the state of lithium intercalation SOL or the state of charge SOC of the electrode.

[0062] Based on the problems of high experimental cost and low efficiency in the OCV prediction results of battery hybrid electrodes in the related art, this application particularly proposes an OCV prediction method for hybrid electrodes based on the principle of thermodynamics, which is calculated through a mathematical model and the results are not affected by fluctuations in experimental conditions, and is stable and reliable. At the same time, it can also improve the evaluation accuracy of SOC.

[0063] Based on this, this application provides a method for generating an OCV curve of a battery hybrid electrode, including the following steps:

[0064] Fabricate half-cells of each constituent raw material in the hybrid electrode.

[0065] In this application, the fabrication of half-cells usually adopts conventional process operations in the art, including mixing different active materials, binders, and conductive agents in proportion to form a slurry, coating the slurry on the surface of the current collector to form an active material layer, drying to obtain a dry electrode film, compacting the electrode through a roll press, and then assembling it into a half-cell.

[0066] Test the open circuit potential OCP and specific capacity Q of the half-cells corresponding to the respective single raw materials in the hybrid electrode.

[0067] In some embodiments, the positive electrode includes two or more positive electrode active materials, preferably lithium nickel cobalt manganese oxide and lithium manganate, or lithium nickel cobalt manganese oxide, lithium manganate, and lithium iron phosphate, wherein the lithium nickel cobalt manganese oxide is further preferably LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0068] In some embodiments, the negative electrode includes two or more negative electrode active materials, preferably graphite and silicon.

[0069] Interpolate the open circuit voltage OCP of the half-cell corresponding to a single raw material in the hybrid battery into a function of the state of lithium insertion SOL.

[0070] In this application, interpolation is used in its conventional sense in the art, referring to a mathematical method for obtaining the value of an unknown point through estimation between known data points.

[0071] In some embodiments, the function of interpolating into the state of lithium insertion SOL includes two steps.

[0072] The first step is to extract the maximum specific capacity Q max , and obtain the SOL sequence.

[0073] In some embodiments, when it comes to the charging state, the charging data is used to calculate SOL at this time, and the formula for the SOL sequence is

[0074]

[0075] where Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity.

[0076] In some embodiments, when it comes to the charging state, the charging data is used to calculate SOL at this time, and the formula for the SOL sequence is

[0077]

[0078] where Q is the charge specific capacity, with the unit of mAh / g, and Q max is the maximum charge specific capacity.

[0079] The second step is to interpolate the calculated SOL sequence into a function of the open circuit voltage OCP of the half-cell, denoted as SOL(OCP).

[0080] Among them, the interpolation method includes one of linear interpolation, nearest neighbor interpolation, and Lagrange interpolation.

[0081] Calculate the SOL sequence and the corresponding specific capacity sequence under the target open circuit voltage OCV sequence for the single raw material in the hybrid electrode.

[0082] In some embodiments, calculating the SOL sequence under the target open circuit voltage OCV sequence for the single raw material in the hybrid electrode includes substituting the target open circuit voltage OCV of the single raw material of the hybrid electrode into the aforementioned state of lithium insertion SOL function to obtain SOL object ,

[0083] SOL object = SOL(OCV)

[0084] In some embodiments, the specific capacity sequence Q interp , and its calculation formula is

[0085] Q interp = SOL objet *Q max ,

[0086] wherein, the Q max is the maximum specific capacity.

[0087] The specific capacity sequence of the mixed electrode is obtained by adding the specific capacity sequences under the SOL sequence according to the weight ratio weights.

[0088] In some embodiments, the calculation formula of the specific capacity sequence of the mixed electrode is

[0089]

[0090] where w i is the weight percentage of the i-th raw material, represents the specific capacity sequence Q object under the SOL corresponding to the i-th raw material interp , the unit is mAh / g, n is the sum of the types of single raw materials in the mixed electrode, and Q mix is the specific capacity at the target OCV of the mixed electrode, and the unit is mAh / g.

[0091] Calculate the state of charge SOC mix sequence of the mixed electrode.

[0092] In some embodiments, the calculation formula of the SOC sequence is

[0093]

[0094] where max is the function to find the maximum value of Q mix .

[0095] In some embodiments, during the process of testing the open circuit voltage OCP and specific capacity Q of the half-cell of the single raw material corresponding to the mixed electrode of the battery under test, the test is divided into a negative electrode applicable test method and a positive electrode applicable test method.

[0096] Furthermore, the negative electrode applicable test method includes: constant current discharging to the lower limit voltage and then standing still, constant current and constant voltage charging to the upper limit voltage, wherein, the current of the constant current discharging is 0.02C, the lower limit voltage is 5mV, the standing still time is 30min, the charging current of the constant current and constant voltage is 0.02C, and the upper limit voltage is 1.5V.

[0097] Further, the applicable test method for the positive electrode includes: constant current and constant voltage charging to the upper limit voltage followed by standing, and constant current discharging to the lower limit voltage. Wherein, the charging current for constant current and constant voltage is 0.02C, the upper limit voltage is 4.3V, the standing time is 30 min, the current for constant current discharging is 0.02C, and the lower limit voltage is 2.8V.

[0098] In this application, the number of data points for target interpolation calculation is N > 50, and further N ≥ 100, for example, 100 - 300.

[0099] In this application, the following calculation formula is used to calculate the root mean square error between the open circuit voltage curve and the curve obtained from actual tests under the same conditions to evaluate the effect of this method.

[0100]

[0101] where exp i is the data obtained from experimental test OCV for the i-th raw material, and model i is the calculated OCV data for the i-th raw material. N is the number of data points for target interpolation calculation. Generally, N > 50, and further N ≥ 100, for example, 100 - 300.

[0102] In this application, the value of the root mean square error is less than 0.005V.

[0103] The following continues to further explain this application with examples.

[0104] The raw materials used in the embodiments of this application are all commercially available.

[0105] Example 1

[0106] As Figure 1 shown, the OCV calculation method for the hybrid electrode provided in this embodiment mainly includes the following steps:

[0107] S101. Make half-cells of graphite and silicon respectively.

[0108] Among them, the counter electrode of the half-cell uses a lithium sheet.

[0109] S102. Test the open circuit potential OCP and specific capacity Q of the half-cells of graphite and silicon respectively.

[0110] The method for testing the half-cell is as follows: constant current discharging to the lower limit voltage, then standing, and constant current and constant voltage charging to the upper limit voltage. Wherein, the magnitude of the constant current discharging current is 0.02C, the lower limit voltage is 5 mV, the constant current and constant voltage charging current is 0.02C, the upper limit voltage is 1.5V, and the standing time is 30 min.

[0111] S103. Interpolate the corresponding SOL into a function of OCP using the discharge data.

[0112] In the first step, extract the maximum discharge specific capacity Q max , and calculate the SOL sequence through the following formula.

[0113]

[0114] where Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity.

[0115] In the second step, linearly interpolate the calculated SOL into a function of OCP, SOL(OCP).

[0116] S104. Calculate the SOL sequence under the target OCV voltage sequence of a single raw material respectively, and substitute the OCV into the above interpolation function to obtain SOL object .

[0117] SOL object = SOL(OCV)

[0118] S105. Calculate the specific capacity sequence Q under the target OCV voltage sequence of a single raw material respectively interp .

[0119] Q interp = SOL objet * Q max

[0120] S106. Add them up by weight ratio weights to obtain the specific capacity sequence Q of the mixed electrode mix .

[0121]

[0122] In this embodiment, the weight ratio of graphite is w1 = 0.85, and the weight ratio of silicon is w2 = 0.15.

[0123] S107. Calculate the SOC sequence SOC of the mixed electrode under the target OCV sequence, where max is the function to find the maximum value of Q mix , and max is the function to find the maximum value of Q mix .

[0124]

[0125] Use the following formula to evaluate the error between the calculated curve and the curve obtained through experimental tests under the same conditions:

[0126]

[0127] where exp iData obtained from the experimental test of OCV for graphite and silicon with the above weight ratios, model i Calculated OCV data for graphite and silicon with the above weight ratios. N is the number of target interpolation calculation data points, and N is 200.

[0128] The mean square error between the calculated OCV and the measured OCV of the above mixed electrode is 0.0031V, and the final generated curve effect is as shown Figure 2 shown.

[0129] Example 2

[0130] As Figure 1 shown, the OCV calculation method for the mixed electrode provided in this example mainly includes the following steps:

[0131] S101. Prepare half-cells of lithium nickel cobalt manganese oxide (LiNi 0.9 Co 0.05 Mn 0.05 O2) and lithium manganate respectively, where lithium nickel cobalt manganese oxide is abbreviated as NCM and lithium manganate is abbreviated as LMO.

[0132] Among them, the counter electrode of the half-cell uses a lithium sheet.

[0133] S102. Test the open circuit potential OCP and specific capacity Q of the half-cells of NCM and LMO respectively.

[0134] The method for testing the half-cell is to charge at a constant current and constant voltage to the upper limit voltage and then stand still, and discharge at a constant current to the lower limit voltage. Among them, the charging current of the constant current and constant voltage is 0.02C, the upper limit voltage is 4.3V, the discharging current of the constant current is 0.02C, the lower limit voltage is 2.8V, and the standing time is 30min.

[0135] S103. Interpolate the corresponding SOL into a function of OCP and use the charging data.

[0136] The first step is to extract the maximum charging specific capacity Q max , and calculate the SOL sequence through the following formula.

[0137]

[0138] Among them, Q is the charging specific capacity, with the unit of mAh / g, and Q max is the maximum charging specific capacity.

[0139] The second step is to linearly interpolate the calculated SOL into a function of OCP, SOL(OCP).

[0140] S104. Calculate the SOL sequence under the target OCV voltage sequence of a single raw material respectively, and substitute OCV into the above interpolation function to obtain SOLobject 。

[0141] SOL object = SOL(OCV)

[0142] S105. Calculate the specific capacity sequence Q under the target OCV voltage sequence of a single raw material respectively interp 。

[0143] Q interp = SOL objet * Q max

[0144] S106. Add by weight ratio weights to obtain the specific capacity sequence Q of the mixed electrode mix 。

[0145]

[0146] In this embodiment, the weight ratio of NCM is w1 = 0.5, and the weight ratio of LMO is w2 = 0.5.

[0147] S107. Calculate the SOC sequence SOC of the mixed electrode under the target OCO sequence mix , max is the function to find the maximum value of Q mix Maximum value function.

[0148]

[0149] Use the following formula to evaluate the error between the calculated curve and the curve obtained through experimental tests under the same conditions

[0150]

[0151] where, exp i is the data obtained from the experimental test of OCV of NCM and LMO with the above weight ratio, and model i is the calculated OCV data of NCM and LMO with the above weight ratio, and N is the number of target interpolation calculation data points, and N is 200.

[0152] The mean square error between the calculated OCV and the measured OCV of the above mixed electrode is 0.0011V, and finally the generated curve effect is as Figure 3 shown.

[0153] Example 3

[0154] As Figure 1 shown, the OCV calculation method of the mixed electrode provided in this embodiment mainly includes the following steps

[0155] S101. Fabricate lithium nickel cobalt manganese oxide (LiNi 0.9 Co 0.05 Mn0.05 The half-cells of O2) and lithium manganese oxide, where ternary nickel cobalt manganese oxide is abbreviated as NCM and lithium manganese oxide is abbreviated as LMO.

[0156] Among them, the counter electrode of the half-cell uses a lithium sheet.

[0157] S102. Respectively test the open circuit voltage OCP and specific capacity Q of the half-cells of NCM and LMO.

[0158] The method for testing the half-cell is to charge at a constant current and constant voltage to the upper limit voltage and then stand still, discharge at a constant current to the lower limit voltage. Among them, the charging current of the constant current and constant voltage is 0.02C, the upper limit voltage is 4.3V, the discharging current of the constant current discharge is 0.02C, the lower limit voltage is 2.8V, and the standing time is 30 min.

[0159] S103. Interpolate the corresponding SOL into a function of OCP and use the discharge data.

[0160] The first step is to extract the maximum discharge specific capacity Q max , and the SOL sequence is calculated through the following formula.

[0161]

[0162] Among them, Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity.

[0163] The second step is to linearly interpolate the calculated SOL into a function SOL(OCP) of OCP.

[0164] S104. Respectively calculate the SOL sequence under the target OCV voltage sequence of a single raw material, and substitute OCV into the above interpolation function to obtain SOL object .

[0165] SOL object = SOL(OCV)

[0166] S105. Respectively calculate the specific capacity sequence Q under the target OCV voltage sequence of a single raw material interp .

[0167] Q interp = SOL objet * Q max

[0168] S106. Add the specific capacity sequences Q of the mixed electrodes by weight ratio weights mix .

[0169]

[0170] In this embodiment, the weight ratio of NCM is w1 = 0.7, and the weight ratio of LMO is w2 = 0.3.

[0171] S107. Calculate the SOC sequence SOC of the mixed electrode under the target OCV sequence mix , where max is the function to find the mix maximum value of Q.

[0172]

[0173] Use the following formula to evaluate the error between the calculated curve and the curve obtained through experimental tests under the same conditions

[0174]

[0175] where exp i is the data obtained from the experimental test of the OCV of NCM and LMO with the above weight ratio, and model i is the calculated OCV data of NCM and LMO with the above weight ratio. N is the number of target interpolation calculation data points, and N is 200.

[0176] The mean square error between the calculated OCV and the measured OCV of the above mixed electrode is 0.0013V, and finally the generated curve effect is the same as the measured one Figure 4 as shown.

[0177] Example 4

[0178] As Figure 1 shown, the method for calculating the OCV of the mixed electrode provided in this embodiment mainly includes the following steps:

[0179] S101. Fabricate half-cells of lithium nickel cobalt manganese oxide (LiNi 0.9 Co 0.05 Mn 0.05 O2), lithium manganese oxide, and lithium iron phosphate respectively. Among them, lithium nickel cobalt manganese oxide is abbreviated as NCM, lithium manganese oxide is abbreviated as LMO, and lithium iron phosphate is abbreviated as LFP.

[0180] Among them, the counter electrode of the half-cell uses a lithium sheet.

[0181] S102. Test the open-circuit voltage OCP and specific capacity Q of the half-cells of NCM, LMO, and LFP respectively.

[0182] The method for testing the half-cell is to charge at a constant current and constant voltage to the upper limit voltage and then let it stand, and discharge at a constant current to the lower limit voltage. Among them, the charging current of the constant current and constant voltage is 0.02C, the upper limit voltage is 4.3V, the discharging current of the constant current is 0.02C, the lower limit voltage is 2.8V, and the standing time is 30 min.

[0183] S103. Interpolate the corresponding SOL into a function of OCP using the discharge data.

[0184] In the first step, extract the maximum discharge specific capacity Q max , and obtain the SOL sequence through the following formula.

[0185]

[0186] where Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity.

[0187] In the second step, linearly interpolate the calculated SOL into a function of OCP, SOL(OCP).

[0188] S104. Calculate the SOL sequences under the target OCV voltage sequences of single raw materials respectively, and substitute the OCV into the above interpolation function to obtain SOL object .

[0189] SOL object = SOL(OCV)

[0190] S105. Calculate the specific capacity sequences Q interp .

[0191] Q interp = SOL objet * Q max

[0192] S106. Add them up according to the weight ratio weights to obtain the specific capacity sequence Q of the mixed electrode mix .

[0193]

[0194] In this embodiment, the weight ratio of NCM is w1 = 0.7, the weight ratio of LMO is w2 = 0.3, and the weight ratio of LFP is w3 = 0.2.

[0195] S107. Calculate the SOC sequence SOC of the mixed electrode under the target OCV sequence mix , where max is the function to find the maximum value of Q mix .

[0196]

[0197] Use the following formula to evaluate the error between the calculated curve and the curve obtained through experimental tests under the same conditions

[0198]

[0199] where exp iData obtained from the experimental test of OCV for NCM, LMO, and LFP with the above weight ratios, model i Calculated OCV data for NCM, LMO, and LFP with the above weight ratios. N is the number of target interpolation calculation data points, and N is 200.

[0200] The mean square error between the calculated OCV and the measured OCV of the above mixed electrode is 0.0012 V, and the final generated curve effect is as shown Figure 5 shown.

[0201] Although the embodiments of the present embodiment have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present embodiment. The scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A method for generating an OCV curve of a battery hybrid electrode, characterized in that, The generation method includes: Fabricating half-cells of each constituent raw material in the composite electrode; Testing the open-circuit voltage OCP and the corresponding specific capacity Q of the half-cells of each constituent raw material; Interpolating the open-circuit voltage OCP of the half-cell corresponding to a single raw material in the composite electrode into a function of the lithium intercalation state SOL; Calculating the SOL sequence and the corresponding specific capacity sequence at the target open-circuit voltage OCV sequence of the single raw material of the composite electrode; Adding the specific capacity sequences by weight according to the mixing weight ratio to obtain the specific capacity sequence of the composite electrode; Calculating the state of charge SOC sequence of the composite electrode.

2. The generation method according to claim 1, wherein The function of the lithium-inserted state SOL includes: extracting the maximum specific capacity Q max , obtaining the SOL sequence, and interpolating the SOL sequence into a function SOL(OCP) of the open-circuit voltage OCP of the half-cell.

3. The generating method according to claim 2, wherein The following conditions are satisfied: When it is for the discharge state, the formula of the SOL sequence is where Q is the discharge specific capacity, with the unit of mAh / g, and Q max is the maximum discharge specific capacity; When it is for the charge state, the formula of the SOL sequence is where Q is the charging specific capacity, with the unit of mAh / g, and Q max is the maximum charging specific capacity; The interpolation method includes one of linear interpolation, nearest-neighbor interpolation, and Lagrange interpolation.

4. The generation method according to claim 3, wherein Calculating the SOL sequence at the target open-circuit voltage OCV sequence of the single raw material of the mixed electrode, including substituting the target open-circuit voltage OCV of the single raw material of the mixed electrode into the function of the lithium insertion state SOL to obtain SOL object , SOL object = SOC(OCV).

5. The generation method according to claim 4, characterized in that The corresponding specific capacity sequence of the SOL sequence satisfies the following calculation method Q interp = SOL object * Q max , Among them, the Q max is the maximum specific capacity.

6. The generation method according to claim 5, characterized in that, The specific capacity sequence of the composite electrode satisfies the following calculation method Among them, w i is the weight percentage of the i-th raw material, represents the specific capacity sequence Q object under the SOL interp sequence corresponding to the i-th raw material, with the unit of mAh / g, and n is the sum of the types of single raw materials in the mixed electrode; Q mix is the specific capacity at the target OCV of the mixed electrode, with the unit of mAh / g.

7. The generation method according to claim 6, characterized in that The state of charge (SOC) of the hybrid electrode mix The sequence satisfies the following calculation method Among them, max is the function for finding the mix maximum value of Q.

8. The generation method according to claim 1, characterized in that, The raw materials of the composite electrode satisfy the following conditions: If the composite electrode is a positive electrode, the active material of the positive electrode includes at least two of lithium nickel cobalt manganese oxide, lithium manganate, lithium cobaltate, lithium iron phosphate, and lithium nickel cobalt aluminate; If the composite electrode is a negative electrode, the active material of the negative electrode includes at least two of graphite, silicon, hard carbon, and soft carbon.

9. The generation method according to claim 1, wherein When testing the open-circuit voltage OCP and the specific capacity Q, the testing is divided into a negative electrode testing method and a positive electrode testing method. The negative electrode testing method includes: constant current discharging to the lower limit voltage and then standing still, constant current and constant voltage charging to the upper limit voltage, where the current of the constant current discharging is 0.02C, the lower limit voltage is 5mV, the standing still time is 30min, the charging current of the constant current and constant voltage charging is 0.02C, and the upper limit voltage is 1.5V; The positive electrode testing method includes: constant current and constant voltage charging to the upper limit voltage and then standing still, constant current discharging to the lower limit voltage, where the charging current of the constant current and constant voltage charging is 0.02C, the upper limit voltage is 4.3V, the standing still time is 30min, the current of the constant current discharging is 0.02C, and the lower limit voltage is 2.8V.

10. The generation method according to any one of claims 1-9, characterized in that, The number of data points for target interpolation calculation is N, and N > 50.

Images