Method for rapidly evaluating high-temperature gas production performance of lithium ion battery cathode material

Abstract

The present application relates to the technical field of lithium battery, in particular to a method for rapidly evaluating high-temperature gas production performance of lithium ion battery cathode material. The method comprises: defining the high-temperature gas production performance index as P, P=X1+X2+X3+X4; wherein, X1=(R*d) / 100, R is the metal dissolution rate, d is the number of days for the cathode material to stand in electrolyte; X2=D / 5, D is the primary particle size of the cathode material, the unit of D is μm; X3=B, B is the specific surface area of the cathode material, the unit of B is m 2 / g; X4=1000 / C, C is the total amount of coating elements of the cathode material, the unit of C is ppm; if P<3, the gas production performance of the lithium ion battery cathode material meets the standard; if P≥3, the gas production performance of the lithium ion battery cathode material does not meet the standard. The method has the advantages of short development cycle, low development cost, high accuracy of judging the high-temperature gas production performance of the cathode material, etc.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials. Background Technology

[0002] Since 2018, the application of single-crystal nickel-cobalt-manganese lithium cathode materials in high-voltage systems has become increasingly mature, and the charging cut-off voltage has gradually increased. Currently, 4.35V and 4.40V have been mass-produced, and 4.45V is under development. It is expected that large-scale mass production can be achieved in 2024. With high charging cut-off voltage and high test temperature, the gas production of the battery will increase exponentially. The current mainstream characterization method is to perform charge-discharge cycles in a high-temperature chamber and periodically use the water displacement method to measure the volume. The overall measurement accuracy is high, but it is time-consuming.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials. This method has the advantages of short development cycle, low development cost, and high accuracy in judging the high-temperature gas generation performance of cathode materials.

[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0006] One aspect of the present invention relates to a method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials, comprising the following steps:

[0007] (a) Define the high-temperature gas production performance index as P, P = X1 + X2 + X3 + X4;

[0008] Where X1=(R*d) / 100, R is the metal dissolution rate, and d is the number of days the positive electrode material is left to stand in the electrolyte;

[0009] X2 = D / 5, where D is the primary particle size of the cathode material, and the unit of D is μm;

[0010] X3 = B, where B is the specific surface area of ​​the positive electrode material, and the unit of B is m². 2 / g;

[0011] X4 = 1000 / C, where C is the total amount of coating elements in the cathode material, and the unit of C is ppm;

[0012] (b) If P < 3, the gas generation performance of the lithium-ion battery cathode material meets the standard; if P ≥ 3, the gas generation performance of the lithium-ion battery cathode material does not meet the standard.

[0013] The method described above adds together factors that are strongly correlated with gas production; it rapidly characterizes high-temperature gas production performance using short-term available material information, thereby shortening the development cycle and reducing development costs; and it facilitates operation by introducing several highly correlated indicators, classifying the indicators and assigning corresponding coefficients.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] The present invention provides a method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials. This method rapidly characterizes high-temperature gas generation performance using material information that is available in a short period of time, thereby shortening the development cycle and reducing development costs. By introducing several highly correlated indicators, which are categorized and assigned corresponding coefficients, the method facilitates operation. At the same time, it reserves an uncertain factor X, which can be added according to the actual situation in subsequent development, thereby continuously improving the accuracy of the judgment. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 The graph shows the high-temperature gas production results at different settling times provided by this invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] One aspect of the present invention relates to a method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials, comprising the following steps:

[0020] (a) Define the high-temperature gas production performance index as P, P = X1 + X2 + X3 + X4;

[0021] Where X1=(R*d) / 100, R is the metal dissolution rate, and d is the number of days the positive electrode material is left to stand in the electrolyte;

[0022] X2 = D / 5, where D is the primary particle size of the cathode material, and the unit of D is μm;

[0023] X3 = B, where B is the specific surface area of ​​the positive electrode material, and the unit of B is m². 2 / g;

[0024] X4 = 1000 / C, where C is the total amount of coating elements in the cathode material, and the unit of C is ppm;

[0025] (b) If P < 3, the gas generation performance of the lithium-ion battery cathode material meets the standard; if P ≥ 3, the gas generation performance of the lithium-ion battery cathode material does not meet the standard.

[0026] This method adds together factors that are strongly correlated with gas production; it rapidly characterizes high-temperature gas production performance using short-term available material information, shortening the development cycle and reducing development costs; and it facilitates operation by introducing several highly correlated indicators, classifying the indicators and assigning corresponding coefficients.

[0027] Over time, the coating elements of the cathode material will dissolve and undergo side reactions with the electrolyte, resulting in gas production. When there are many side reactions in the electrolyte, the size of the primary particles and the specific surface area will be greatly affected. The metal dissolution rate and coating amount will affect the stability of the material. Changes in the metal dissolution rate and coating amount will increase oxygen release and also cause gas production.

[0028] The P-value predicts the likelihood of gas production, but does not represent the specific gas production value. The larger the P-value, the greater the risk of high gas production. Before mass production, the material ratio and formula should be adjusted in a timely manner.

[0029] Preferably, the step of calculating the metal dissolution rate R includes:

[0030] The metal element content of the positive electrode material is detected; the positive electrode material is dissolved in the electrolyte and then allowed to stand; the metal element content of the positive electrode material after standing is detected; and the metal dissolution rate R is calculated.

[0031] Preferably, the ambient temperature for the static setting is 58–62°C.

[0032] In some specific embodiments, the ambient temperature for resting can be, for example, but not limited to, 58°C, 59°C, 60°C, 61°C, or 62°C.

[0033] Preferably, the mass ratio of the positive electrode material to the electrolyte is (1-10):(5-30).

[0034] In some specific embodiments, the mass ratio of the positive electrode material to the electrolyte can be, for example, but not limited to, 1:30, 3:25, 5:20, 7:15, 9:10 or 10:5.

[0035] Preferably, the working voltage of the electrolyte is 4.3 to 5V.

[0036] Preferably, the value of R is between 1% and 20%.

[0037] In some specific implementations, the value of R can be, for example, but not limited to, 1%, 4%, 7%, 10%, 13%, 17%, or 20%.

[0038] Preferably, the value of d is 7 to 100 days.

[0039] In some specific implementations, the value of d can be, for example, but not limited to, 7 days, 20 days, 30 days, 40 days, 50 days, 60 days, 70 days, 80 days, 90 days or 100 days.

[0040] Preferably, the value of D is 0.5 to 3 μm.

[0041] In some specific implementations, the value of D can be, for example, but not limited to, 0.5, 1μm, 1.5μm, 2μm, 2.5μm or 3μm.

[0042] If the primary particle size D is too large, it will affect the capacity utilization; if it is too small, there will be more interfacial side reactions, which will affect long-term performance.

[0043] Preferably, the value of B is <1m 2 / g.

[0044] In some specific implementations, the value of B can be, for example, but not limited to, 0.1m. 2 / g, 0.3m 2 / g, 0.5m 2 / g, 0.7m 2 / g or 0.9m 2 / g.

[0045] Preferably, the value of B is 0.6-0.8m. 2 / g.

[0046] If the specific surface area B of the cathode material is too small, the cathode material particles will be large and the impedance will be high. If B is too large, the cathode material particles will be small, resulting in more side reactions with the electrolyte and affecting the processing performance.

[0047] Preferably, the value of C is <5000ppm.

[0048] In some specific implementations, the value of C can be, for example, but not limited to, 2000, 2300, 2500, 2800, 3000, 3300, 3500, 3800, 4000, 4300, 4500 or 4800.

[0049] Preferably, the value of C is between 2000 and 4000 ppm.

[0050] If the total amount of coating elements (C) in the cathode material is too large, it will affect lithium-ion conduction, increase impedance, and cause side reactions with the electrolyte, resulting in structural instability and excessive gas production; if the amount of C is too small, it will not improve the material and will affect long-term performance.

[0051] If R, D, B, and C all meet the above-defined ranges, the method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials provided by this invention can be used; if one or more of R, D, B, and C do not meet the above-defined ranges, the method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials provided by this invention cannot be used.

[0052] The method for testing the primary particle size of cathode materials includes the following steps:

[0053] A 5Kx electron microscope was used, and Image software was used to calibrate the major and minor axes of all intact particles in the field of view. The average value was then taken.

[0054] The method for testing the specific surface area of ​​cathode materials includes the following steps:

[0055] The BET method was used, and the surface area was measured using a specific surface area meter.

[0056] The method for testing the total amount of coating elements in cathode materials includes the following steps:

[0057] After acid digestion, the samples were tested using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0058] The formula for calculating the metal dissolution rate is as follows:

[0059] R / % = Total dissolved coating elements / Total initial coating elements × 100%.

[0060] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0061] Examples 1-3

[0062] Examples 1-3 provided by the present invention respectively detect the primary particle size D, specific surface area B, and total amount of coated elements C of the positive electrode material of lithium-ion battery, and test the metal dissolution rate R of the positive electrode material at different stages of standing in the electrolyte. According to the formula: P=X1+X2+X3+X4, the P value is calculated respectively. Detailed information is shown in Table 1 and Table 2.

[0063] Comparative Examples 1-2

[0064] The comparative examples 1-2 provided by this invention respectively tested the primary particle size D, specific surface area B, and total amount of coated elements C of the positive electrode material of lithium-ion battery, and tested the metal dissolution rate R of the positive electrode material at different stages of standing in the electrolyte. According to the formula: P=X1+X2+X3+X4, the P value was calculated respectively. Detailed information is shown in Table 1 and Table 2.

[0065] Table 1

[0066]

[0067]

[0068] Table 2

[0069]

[0070] Experimental Example

[0071] The positive electrode material obtained in the examples, under the same environment and testing regime, can be used to predict the gas production at high temperature after being left to stand for different times. The specific detection method includes: fabricating the obtained positive electrode material into a 3Ah small soft-pack battery cell, leaving it to stand at high temperature for a certain time, and then measuring the volume using the water displacement method. The increase in weight represents the volume of gas produced. The results are as follows... Figure 1 As shown in Table 3.

[0072] Table 3

[0073]

[0074]

[0075] The test results show that the amount of gas produced increases with the increase of the resting time. Within the same time period, the larger the P value, the greater the risk of gas production. The amount of gas produced in the embodiment is less than that in the comparative example, and the P value of the embodiment is smaller than that in the comparative example. This indicates that the formulation range of the cathode material in the embodiment is reasonable. When evaluating new materials, the long-term gas production performance can be assessed based on the physicochemical test results to determine whether it is worthwhile to conduct further evaluation and whether the formulation needs to be adjusted to improve the sample, thereby shortening the development cycle and reducing development costs.

[0076] In summary, the method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials provided by this invention can accurately evaluate the high-temperature gas generation performance of lithium-ion battery cathode materials.

[0077] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials, characterized in that, Includes the following steps: (a) Define the high-temperature gas production performance index as P, P=X1+X2+X3+X4; Where X1 = (R*d) / 100, R is the metal dissolution rate, and d is the number of days the positive electrode material is left to stand in the electrolyte; X2 = D / 5, where D is the primary particle size of the cathode material, and the unit of D is μm; X3 = B, where B is the specific surface area of ​​the positive electrode material, and the unit of B is m². 2 / g; X4 = 1000 / C, where C is the total amount of coating elements in the cathode material, and the unit of C is ppm; (b) If P < 3, the gas generation performance of the lithium-ion battery cathode material meets the standard; if P ≥ 3, the gas generation performance of the lithium-ion battery cathode material does not meet the standard. The steps for calculating the metal dissolution rate R include: The metal element content of the positive electrode material is detected; the positive electrode material is dissolved in the electrolyte and then allowed to stand; the metal element content of the positive electrode material after standing is detected; the metal dissolution rate R is calculated. The ambient temperature for static placement is 58~62℃; The mass ratio of the positive electrode material to the electrolyte is (1~10):(5~30).

2. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The working voltage of the electrolyte is 4.3~5V.

3. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The value of R is between 1% and 20%.

4. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The value of d is 7 to 100 days.

5. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The value of D is 0.5~3μm.

6. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The value of B is <1m 2 / g.

7. The method for rapidly evaluating the high-temperature gas generation performance of lithium-ion battery cathode materials according to claim 1, characterized in that, The value of C is <5000ppm.

Images