Positive electrode lithium supplement additive and its preparation method and application

Abstract

The present application relates to the field of battery technology, and more particularly to a positive electrode lithium replenishing additive, its preparation method, and application. A positive electrode lithium replenishing additive is provided, comprising a lithium-containing material and a doping phase present in the bulk phase of the lithium-containing material, wherein the positive electrode lithium replenishing additive has a water absorption rate of 0 to 50 ppm / s. A lithium-containing material containing a doping phase with a water absorption rate of 0 to 50 ppm / s is selected as the positive electrode lithium replenishing additive to ensure that the resulting positive electrode lithium replenishing additive has good moisture resistance and a good doping effect of the doping phase, thereby achieving excellent battery properties and preventing the entire battery from being scrapped.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a positive electrode lithium supplement additive and a preparation method and application thereof. Background Art

[0002] Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive electrode and the negative electrode to work. + Insertion and deinsertion back and forth between the two electrodes: During charging, Li + Lithium is released from the positive electrode and then re-entered into the negative electrode through the electrolyte, leaving the negative electrode in a lithium-rich state. The opposite is true during discharge. Lithium-ion batteries strive for high energy density, and increasing capacity is one way to achieve this.

[0003] A common problem with lithium-ion batteries is that during the initial charge, a large amount of lithium ions released from the positive electrode are consumed to form the SEI film on the negative electrode surface. This results in irreversible consumption of over 10% of the positive electrode's lithium source during the initial charge, and the initial coulombic efficiency is less than 90%. Furthermore, lithium-ion batteries also continuously consume active lithium during normal use. This can lead to a reduction in the initial capacity of the battery cell and a shortened battery life. Consequently, a variety of positive electrode lithium supplementation additive materials are currently available that are mixed with the positive electrode materials to assemble the battery.

[0004] In batteries using positive-electrode lithium-supplementing additives, the ability to meet requirements can only be determined after assembly. This degradation is primarily due to the lithium-supplementing material's tendency to absorb moisture during use, resulting in poor moisture resistance and ultimately, failure. However, this degradation can only be detected after the battery is assembled, rendering the entire battery useless and increasing the number of scrapped batteries. Furthermore, it is currently difficult to determine the doping status by measuring water absorption without assembling the battery. Summary of the Invention

[0005] The purpose of the present application is to provide a positive electrode lithium supplement additive and its preparation method and application, aiming to solve the problem in the prior art that it is impossible to measure the water absorption rate of the lithium supplement material to determine the doping state without assembling it into a battery.

[0006] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0007] In a first aspect, the present application provides a positive electrode lithium replenishing additive, which includes a lithium-containing material and a doped phase layer present in the bulk phase of the lithium-containing material, wherein the water absorption rate of the positive electrode lithium replenishing additive is 0 to 50 ppm / s.

[0008] In a second aspect, the present application provides a method for preparing a positive electrode lithium supplement additive, comprising the following steps:

[0009] providing a lithium-containing material comprising a doped phase;

[0010] The lithium-containing material containing the doped phase is laid loosely and flatly on an analytical balance, and the mass at different time points from 0 to 60 minutes is recorded to calculate the water absorption rate of the lithium-containing material containing the doped phase;

[0011] A lithium-containing material containing a doped phase and having a water absorption rate of 0 to 50 ppm / s is selected as a positive electrode lithium supplement additive.

[0012] In a third aspect, the present application provides a positive electrode plate, which comprises a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a binder, a conductive agent and a positive electrode lithium replenishing additive, wherein the positive electrode lithium replenishing additive is selected from a positive electrode lithium replenishing additive or prepared by a preparation method of a positive electrode lithium replenishing additive.

[0013] In a fourth aspect, the present application provides a secondary battery, which includes a positive electrode plate.

[0014] The first aspect of the present application provides a positive electrode lithium replenishing additive, which includes a lithium-containing material and a doped phase present in the bulk phase of the lithium-containing material. After the lithium-containing material containing the doped phase is prepared, a water absorption rate test is also carried out, and a lithium-containing material containing the doped phase with a water absorption rate of 0 to 50 ppm / s is selected as the positive electrode lithium replenishing additive, ensuring that the obtained positive electrode lithium replenishing additive has good moisture resistance and that the doping effect of the doped phase is good, so that the obtained battery has excellent properties and the entire battery will not be scrapped.

[0015] The second aspect of the present application provides a method for preparing a positive electrode lithium supplement additive. In this preparation method, the prepared lithium-containing material containing a doped phase is laid flat on an analytical balance, the mass at different time points within 0 to 60 minutes is recorded, the water absorption rate of the lithium-containing material containing the doped phase is calculated, and the lithium-containing material containing the doped phase with a water absorption rate of 0 to 50 ppm / s is further selected as the positive electrode lithium supplement additive. In this preparation method, the water absorption rate of the lithium-containing material containing the doped phase can be measured for the positive electrode lithium supplement additive material without assembling it into a battery to determine the doping effect of the doped phase, thereby ensuring that the obtained positive electrode lithium supplement additive has good moisture resistance. After it is assembled and packaged to form a battery, the proportion of the lithium supplement additive material that is prone to moisture absorption reaction is reduced due to bulk doping of the doping element, and the doping element can reduce the activity of the lithium supplement additive material, thereby increasing the stability of the lithium supplement additive material in the outdoor environment. In addition, it can also improve the activity of the lithium supplement additive material during charging and discharging, thereby ensuring that the entire battery will not be scrapped and improving the battery life.

[0016] The third aspect of the present application provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode lithium replenishing additive. Based on the provided positive electrode lithium replenishing additive, the water absorption rate is limited to 0-50ppm / s. It has good moisture resistance, can isolate harmful components such as water and carbon dioxide in the air and has a certain conductivity. After being assembled to form a battery, it can replenish lithium for the positive electrode of the battery, thereby increasing the service life of the battery, maintaining the abundance of lithium ions in the battery system, improving the initial efficiency and overall electrochemical performance of the battery, and realizing efficient lithium replenishment.

[0017] The secondary battery provided in the fourth aspect of the present application comprises a provided positive electrode plate, and the positive electrode plate comprises a positive electrode lithium replenishing additive prepared by a method for preparing a positive electrode lithium replenishing additive, ensuring that the positive electrode lithium replenishing additive in the positive electrode plate has good moisture resistance before being packaged to form a secondary battery, and is not affected by water vapor and carbon dioxide in the air, so that the lithium ions in the assembled secondary battery system are stable, the overall electrochemical performance of the battery is improved, and the battery has good cycle performance and lithium replenishing performance, which is conducive to wide use. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0019] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0020] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0021] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0022] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0023] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass in the examples of this application may be μg, mg, g, kg, etc., which are mass units known in the chemical industry.

[0024] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. For example, a first XX could also be referred to as a second XX, and similarly, a second XX could also be referred to as a first XX, without departing from the scope of the embodiments of this application. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0025] In a first aspect, an embodiment of the present application provides a positive electrode lithium replenishing additive, which includes a lithium-containing material and a doping phase present in the bulk phase of the lithium-containing material, wherein the water absorption rate of the positive electrode lithium replenishing additive is 0 to 50 ppm / s.

[0026] The positive electrode lithium replenishing additive provided in the first aspect of the embodiment of the present application includes a lithium-containing material and a doped phase present in the bulk phase of the lithium-containing material. After the lithium-containing material containing the doped phase is prepared, a water absorption rate test is also carried out, and a lithium-containing material containing the doped phase with a water absorption rate of 0 to 50 ppm / s is selected as the positive electrode lithium replenishing additive, ensuring that the obtained positive electrode lithium replenishing additive has good moisture resistance and that the doping effect of the doped phase is good, so that the obtained battery has excellent properties and the entire battery will not be scrapped.

[0027] In some embodiments, the water absorption rate of the positive electrode lithium supplement additive is 0 to 50 ppm / s. If the water absorption rate of the positive electrode lithium supplement additive is high, it means that the sample is easy to deteriorate during the battery processing and cannot function normally.

[0028] In some specific embodiments, the water absorption rate of the positive electrode lithium supplement additive includes but is not limited to 0 ppm / s, 5 ppm / s, 10 ppm / s, 15 ppm / s, 20 ppm / s, 25 ppm / s, 30 ppm / s, 35 ppm / s, 40 ppm / s, 45 ppm / s, and 50 ppm / s.

[0029] In some embodiments, the positive electrode lithium supplement additive includes a lithium-containing material and a doping phase present in the bulk of the lithium-containing material.

[0030] In some embodiments, the lithium-containing material includes Li x M y O z 、Li w At least one of A; wherein, 0<x≤8, 0<y≤3, 0<z≤6, 0<w≤5; M is at least one element selected from Fe, Co, Ni, Mn, Si, Sn, Cu, Mo, Al, and Ti, and A is at least one element selected from C, N, O, P, S, F, B, and Se.

[0031] In some embodiments, the doping element in the positive electrode lithium supplement additive includes at least one element selected from the group consisting of Al, Zr, Si, C, Co, Ni, Ti, Mn, and Cu. By doping with the doping element, the activity of the material can be reduced, thereby alleviating its stability in the air. At the same time, a certain amount of Ni is added. 2+ , Ni 2+ It is relatively stable at room temperature and increases in value to Ni during recharging. 3+ After that, it has higher catalytic activity, which is beneficial to the release of Li.

[0032] In some embodiments, the content of doping elements in the positive electrode lithium replenishing additive is 1% to 10%. If the content of doping elements is too high, the material's gram capacity will be reduced, the charging voltage platform will be increased, and the constant current charging ratio will be reduced. If the doping content is too low, the stabilizing effect of doping on the material will be weakened, and the positive electrode lithium replenishing additive with the required water absorption rate cannot be obtained. Specifically, it can be 1%, 3wt%, 5wt%, 6wt%, 9wt%, and 10wt%.

[0033] In some embodiments, in the positive electrode lithium supplement additive, the covalent bonds containing doping elements exist inside the lithium-containing material, which can further provide the crystal structure of the positive electrode lithium supplement additive, thereby facilitating the acquisition of a positive electrode lithium supplement additive with better water absorption.

[0034] A second aspect of the present invention provides a method for preparing a positive electrode lithium supplement additive, comprising the following steps:

[0035] S01 provides a lithium-containing material containing a doped phase;

[0036] S02. The lithium-containing material containing the doped phase is loosely laid on an analytical balance, and the mass is recorded at different time points within 0 to 60 minutes to calculate the water absorption rate of the lithium-containing material containing the doped phase;

[0037] S03. Select a lithium-containing material containing a doped phase with a water absorption rate of 0 to 50 ppm / s as a positive electrode lithium supplement additive.

[0038] The second aspect of the embodiment of the present application provides a method for preparing a positive electrode lithium replenishing additive. In this preparation method, the prepared lithium-containing material containing a doped phase is laid flat on an analytical balance, the mass at different time points within 0 to 60 minutes is recorded, the water absorption rate of the lithium-containing material containing the doped phase is calculated, and the lithium-containing material containing the doped phase with a water absorption rate of 0 to 50 ppm / s is further selected as the positive electrode lithium replenishing additive. In this preparation method, the water absorption rate of the lithium-containing material containing the doped phase can be measured for the positive electrode lithium replenishing additive material without assembling it into a battery to determine the doping state of the doped phase, thereby ensuring that the obtained positive electrode lithium replenishing additive has good moisture resistance. After it is assembled and packaged to form a battery, the doping elements are bulk-doped, thereby increasing the stability of the lithium replenishing additive material in the outdoor environment atmosphere, thereby ensuring that the obtained battery has excellent properties, and the entire battery will not be scrapped, thereby improving the battery life.

[0039] In step S01 , a lithium-containing material containing a doped phase is provided.

[0040] In some embodiments, the lithium-containing material includes Li x M y O z 、Li w At least one of A; wherein, 0<x≤8, 0<y≤3, 0<z≤6, 0<w≤5; M is at least one element selected from Fe, Co, Ni, Mn, Si, Sn, Cu, Mo, Al, and Ti, and A is at least one element selected from C, N, O, P, S, F, B, and Se.

[0041] In some embodiments, a method for preparing a lithium-containing material containing a doped phase comprises:

[0042] S011. Provide lithium-containing materials;

[0043] S012. The doping phase material is dispersed in an organic solvent to obtain a doping phase solution;

[0044] S013. The doping phase solution and the lithium-containing material are uniformly mixed by ball milling / stirring, and then sintered under an inert atmosphere to obtain a lithium-containing material containing a doping phase.

[0045] In some embodiments, the lithium-containing material containing the doped phase is placed in a glove box, and one sample is taken at a time. After the test, another sample is taken out of the glove box to avoid contamination that may cause inaccurate data.

[0046] In step S02 , the lithium-containing material containing the doped phase is placed flat on an analytical balance, the mass at different time points from 0 to 60 minutes is recorded, and the water absorption rate of the lithium-containing material containing the doped phase is calculated.

[0047] In some embodiments, the analytical balance is placed under the following conditions: standard atmospheric pressure, temperature of 25-26° C., and relative humidity of 10%-50%. Only by measuring the water absorption rate under these conditions can the data be guaranteed to be correct.

[0048] In some embodiments, the relative humidity varies by less than 5%.

[0049] In some embodiments, the relative humidity is selected from between 20-25% or between 30-35%.

[0050] In some embodiments, the analytical balance is selected from a 100,000 precision analytical balance.

[0051] In some embodiments, in the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the weight of the lithium-containing material containing the doped phase is 0.1 to 1 gram. In some specific embodiments, the weight of the lithium-containing material containing the doped phase is 0.17 to 0.19 grams. Providing an appropriate amount of lithium-containing material containing the doped phase for measurement is conducive to analyzing the water absorption rate of the material. In some specific embodiments, the weight of the lithium-containing material containing the doped phase includes but is not limited to 0.17 grams, 0.175 grams, 0.18 grams, 0.185 grams, and 0.19 grams.

[0052] Furthermore, the lithium-containing material containing the doped phase is spread flat on an analytical balance. The material is spread as thinly and evenly as possible to ensure that the test area does not affect the water absorption rate of the material.

[0053] In some embodiments, during the step of calculating the water absorption rate of the lithium-containing material containing a doped phase, the thickness of the layered lithium-containing material containing a doped phase is 0.01 to 3 cm. In some specific embodiments, the thickness of the layered lithium-containing material containing a doped phase is 0.1 to 0.3 cm. Ensure that the layered area is as thin and uniform as possible to ensure that the test area does not affect the water absorption rate of the material.

[0054] In some specific embodiments, the tile thickness of the lithium-containing material containing the doped phase includes, but is not limited to, 0.1 cm, 0.15 cm, 0.2 cm, 0.25 cm, and 0.3 cm.

[0055] Furthermore, the mass at different time points within 0 to 60 minutes was recorded to calculate the water absorption rate of the lithium-containing material containing the doped phase.

[0056] In some embodiments, the step of recording the mass at different times within 0 to 60 minutes includes: recording the mass at every 5-minute interval within 0 to 60 minutes.

[0057] In some embodiments, the mass at different times within 0 to 20 minutes is recorded, including: recording the mass at 0 minutes, 5 minutes, 10 minutes, 15 minutes, and 20 minutes, and calculating the water absorption rate of the lithium-containing material containing the doped phase.

[0058] In some embodiments, in the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the calculation formula of the water absorption rate is:

[0059] V=(w t2 -w t1 ) / w0*(t2-t1);

[0060] Among them, w0 is the mass of sample added, w t1 is the mass of the sample after the placement time t1, w t2 is the mass of the sample after the placement time t2, t1 and t2 are the placement time.

[0061] In some embodiments, t1 and t2 need to be greater than 600 seconds.

[0062] A third aspect of an embodiment of the present application provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material, a binder, a conductive agent and a positive electrode lithium replenishing additive, wherein the positive electrode lithium replenishing additive is selected from a positive electrode lithium replenishing additive or prepared by a preparation method of a positive electrode lithium replenishing additive.

[0063] The positive electrode plate provided in the third aspect of the embodiment of the present application comprises a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode lithium replenishing additive. Based on the provided positive electrode lithium replenishing additive, the water absorption rate is limited to 0 to 50 ppm / s. It has good moisture resistance, can isolate harmful components such as water and carbon dioxide in the air and has a certain conductivity. After being assembled to form a battery, it can replenish lithium for the positive electrode of the battery, thereby increasing the service life of the battery, maintaining the abundance of lithium ions in the battery system, improving the initial efficiency and overall electrochemical performance of the battery, and realizing efficient lithium replenishment.

[0064] In some embodiments, the mass percentage of the lithium supplement additive in the positive electrode active layer is 0.5 wt % to 20 wt %.

[0065] In some specific embodiments, the mass percentage of the lithium supplement additive in the positive electrode active layer includes but is not limited to 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 10.0wt%, 11.0wt%, 12.0wt%, 13.0wt%, 14.0wt%, 15.0wt%, 16.0wt%, 17.0wt%, 18.0wt%, 19.0wt%, 20.0wt%, 21.0wt%, 22.0wt%, 23.0wt%, 24.0wt%, 25.0wt%, 26.0wt%, 27.0wt%, 28.0wt%, 29.0wt%, 30.0wt%, 31.0wt%, 32.0wt%, 33.0wt%, 34.0wt%, 35.0wt%, 36.0wt%, 37.0wt%, 38.0wt%, 39.0wt%, 40.0wt%, 41.0wt%, 42.0wt%, 43.0wt%, 44.0wt%, 45.0wt%, 46.0wt%, 47.0wt%, 48.0wt%, 49.0wt%, 50.0wt%, 51.0wt%, 52.0wt%, 53.0wt%, 54.0wt%, 55.0wt%, 56.0wt%, 57.0wt%, 58.0wt%, 59.0wt%, 60.0wt%, 61.0wt%, 62.0wt%, 63.0wt%, t%, 9.5wt%, 10.0wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5w t%, 15wt%, 15.5wt%, 16wt%, 16.5wt%, 17wt%, 17.5wt%, 18wt%, 18.5wt%, 19wt%, 19.5wt%, 20wt%.

[0066] In some embodiments, the mass percentage of the conductive agent in the positive electrode active layer is 0.5 wt % to 15 wt %.

[0067] In some specific embodiments, the mass percentage of the conductive agent in the positive electrode active layer includes but is not limited to 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt%, 10.0wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, and 15wt%.

[0068] In some embodiments, the binder content in the positive electrode active layer is 0.5 wt % to 15 wt %.

[0069] In some specific embodiments, the mass percentage of the binder in the positive electrode active layer includes but is not limited to 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt%, 10.0wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, and 15wt%.

[0070] A fourth aspect of an embodiment of the present application provides a secondary battery, which includes a positive electrode plate.

[0071] The secondary battery provided in the fourth aspect of the embodiment of the present application includes a provided positive electrode plate, and the positive electrode plate includes a positive electrode lithium replenishing additive prepared by a preparation method of a positive electrode lithium replenishing additive, ensuring that the positive electrode lithium replenishing additive in the positive electrode plate has good moisture resistance before being packaged to form a secondary battery, and is not affected by water vapor and carbon dioxide in the air, so that the lithium ions in the assembled secondary battery system are stable, the overall electrochemical performance of the battery is improved, and it has good cycle performance and lithium replenishing performance, which is conducive to wide use.

[0072] The following describes the details in conjunction with specific embodiments.

[0073] Example A1

[0074] Positive electrode lithium supplement additive and preparation method thereof

[0075] The preparation method comprises the following steps:

[0076] (1) providing a lithium-containing material containing a doped phase, wherein the doping elements in the doped phase are Al and Ni, and the lithium-containing material is Li5FeO4;

[0077] ① First prepare the lithium supplement material Li5FeO4. According to the ratio of Li:Fe=5.1:1, weigh a certain mass of lithium oxide and iron oxide, mix them thoroughly, sinter them at 350℃ in argon atmosphere for 5h, then heat to 750℃ and sinter for 7h. After the tube furnace cools naturally to room temperature, take it out and crush it to obtain the lithium supplement material Li5FeO4.

[0078] ② According to the mass of the lithium-replenishing material Li5FeO4 prepared in ①, weigh 8% aluminum nitrate and 2% nickel nitrate and place them in anhydrous ethanol. The amount of anhydrous ethanol added is sufficient to evenly disperse the aluminum nitrate and nickel nitrate. Ultrasonic dispersion is performed for 3 hours to obtain a uniform solution. The obtained uniform solution can play a key role in the subsequent process of doping lithium-replenishing materials.

[0079] ③ The mixed solution prepared in ② is evenly mixed with the lithium supplement material Li5FeO4 prepared in ① by ball milling / stirring, thereby further ensuring that Al and Ni can be evenly doped in the lithium supplement material during the subsequent sintering process to reduce the water absorption rate of the lithium supplement material in the air. The evenly mixed solution / lithium supplement material Li5FeO4 is placed in a tubular furnace, argon is introduced, and the temperature is increased to 600°C at a heating rate of 2-5°C / min and sintered for 5 hours to obtain the Li5FeO4-doped Ni / Al composite lithium supplement material.

[0080] ④ Confirm the presence of doped phase on the surface of the doped lithium supplement material; in the EDS characterization, it can be seen that Al and Ni are doped on the Li5FeO4 lithium supplement material, which shows that the use of the above-mentioned doping process can make 8% Al and 2% Ni uniformly doped in the lithium supplement material.

[0081] (2) placing the lithium-containing material containing the doped phase flat on an analytical balance, recording the mass at different time points from 0 to 60 minutes, and calculating the water absorption rate of the lithium-containing material containing the doped phase;

[0082] ① Under standard atmospheric pressure, control the room humidity at 25℃ and relative humidity at 20-25%;

[0083] ② Take out 0.3-0.5g of sample from the glove box, one sample at a time, and take out the next sample from the glove box after the test;

[0084] ③ Place the weighing bottle in a 1 / 100,000 precision analytical balance, close the hatch, and reset to zero;

[0085] ④ Weigh 0.17-0.19 grams of the sample to be tested into a container. Use a spoon to spread the material as thinly and evenly as possible to ensure that the test area does not affect the material's water absorption rate. Close the hatch, wait for 3-5 seconds for the sample to stabilize, then start the timer and record the mass of the analytical balance as the value at 0 minutes. Next, record the values ​​at 5, 10, 15, and 20 minutes. Calculate the average absorption data for 10-20 minutes to calculate the water absorption rate of the lithium-containing material containing the doped phase.

[0086] (3) A lithium-containing material containing a doped phase with a water absorption rate of 0 to 50 ppm / s is selected as a positive electrode lithium supplement additive.

[0087] Example A2

[0088] Positive electrode lithium supplement additive and preparation method thereof

[0089] The preparation method comprises the following steps:

[0090] (1) providing a lithium-containing material containing a doped phase, wherein the doping element in the doped phase is Si and the lithium-containing material is Li5FeO4;

[0091] ① First prepare the lithium supplement material Li5FeO4. According to the ratio of Li:Fe=5.1:1, weigh a certain mass of lithium oxide and iron oxide, mix them thoroughly, sinter them at 350℃ in argon atmosphere for 5h, then heat to 750℃ and sinter for 7h. After the tube furnace cools naturally to room temperature, take it out and crush it to obtain the lithium supplement material Li5FeO4.

[0092] ② According to the mass of the lithium-replenishing material Li5FeO4 prepared in ①, weigh 2% nano-silica and place it in anhydrous ethanol. The amount of anhydrous ethanol added can make the nano-silica evenly dispersed. Ultrasonic dispersion is performed for 5 hours to obtain a uniform suspension. The obtained suspension can play a key role in the subsequent process of doping lithium-replenishing materials.

[0093] ③ The suspension prepared in ② is evenly mixed with the lithium supplement material Li5FeO4 prepared in ① by ball milling / stirring, thereby further ensuring that Si can be evenly doped in the lithium supplement material during the subsequent sintering process to reduce the water absorption rate of the lithium supplement material in the air. The evenly mixed suspension / lithium supplement material Li5FeO4 is placed in a tubular furnace, argon is introduced, and the temperature is increased to 750°C at a heating rate of 3°C / min and sintered for 6 hours to obtain a Li5FeO4-doped Si composite lithium supplement material.

[0094] ④ Confirm the presence of doped phase in the doped lithium supplement material; in the EDS characterization, it can be seen that Si is uniformly doped in the Li5FeO4 lithium supplement material. After ICP testing, the Si content is 1.99%, which shows that the use of the above-mentioned doping process can make 2% doping element Si uniformly doped in the lithium supplement material.

[0095] (2) placing the lithium-containing material containing the doped phase flat on an analytical balance, recording the mass at different time points from 0 to 60 minutes, and calculating the water absorption rate of the lithium-containing material containing the doped phase;

[0096] ① Under standard atmospheric pressure, control the room humidity at 25℃ and relative humidity at 20-25%;

[0097] ② Take out 0.3-0.5g of sample from the glove box, one sample at a time, and take out the next sample from the glove box after the test;

[0098] ③ Place the weighing bottle in a 1 / 100,000 precision analytical balance, close the hatch, and reset to zero;

[0099] ④ Weigh 0.17-0.19 grams of the sample to be tested into a container. Use a spoon to spread the material as thinly and evenly as possible to ensure that the test area does not affect the material's water absorption rate. Close the hatch, wait for 3-5 seconds for the sample to stabilize, then start the timer and record the mass of the analytical balance as the value at 0 minutes. Next, record the values ​​at 5, 10, 15, and 20 minutes. Calculate the average absorption data for 10-20 minutes to calculate the water absorption rate of the lithium-containing material containing the doped phase.

[0100] (3) A lithium-containing material containing a doped phase with a water absorption rate of 0 to 50 ppm / s is selected as a positive electrode lithium supplement additive.

[0101] Example A3

[0102] Positive electrode lithium supplement additive and preparation method thereof

[0103] The preparation method comprises the following steps:

[0104] (1) providing a lithium-containing material containing a doped phase, wherein the doping elements in the doped phase are Zr and Mn, and the lithium-containing material is Li5FeO4;

[0105] ① First prepare the lithium supplement material Li5FeO4. According to the ratio of Li:Fe=5.1:1, weigh a certain mass of lithium oxide and iron oxide, mix them thoroughly, sinter them at 350℃ in argon atmosphere for 5h, then heat to 750℃ and sinter for 7h. After the tube furnace cools naturally to room temperature, take it out and crush it to obtain the lithium supplement material Li5FeO4.

[0106] ② Based on the mass of the lithium-supplementing material Li5FeO4 prepared in ①, weigh 5% zirconium hydroxide and 1% manganese monoxide and place them in anhydrous ether. The amount of anhydrous ether added should be sufficient to evenly disperse the additives. Ultrasonic dispersion is performed for 5 hours to obtain a uniform suspension. This suspension plays a key role in the subsequent doping process of the lithium-supplementing material.

[0107] ③ The solution prepared in ② is evenly mixed with the lithium supplement material Li5FeO4 prepared in ① by ball milling / stirring, thereby further ensuring that Zr and Mn can be evenly doped in the lithium supplement material during the subsequent sintering process to reduce the water absorption rate of the lithium supplement material in the air. The evenly mixed suspension / lithium supplement material Li5FeO4 is placed in a tubular furnace, argon is introduced, and the temperature is increased to 100°C at a heating rate of 2°C / min and sintered for 2 hours to obtain the Li5FeO4 doped Zr and Mn composite lithium supplement material.

[0108] ④ Confirm the presence of doped phase in the doped lithium supplement material; in the EDS characterization, it can be seen that Zr and Mn are uniformly doped on the Li5FeO4 lithium supplement material. After ICP testing, the Zr content is 5% and the Mn content is 1%, which shows that the use of the above-mentioned doping process can make Zr and Mn uniformly doped on the surface of the lithium supplement material.

[0109] (2) placing the lithium-containing material containing the doped phase flat on an analytical balance, recording the mass at different time points from 0 to 60 minutes, and calculating the water absorption rate of the lithium-containing material containing the doped phase;

[0110] ① Under standard atmospheric pressure, control the room humidity at 25℃ and relative humidity at 20-25%;

[0111] ② Take out 0.3-0.5g of sample from the glove box, one sample at a time, and take out the next sample from the glove box after the test;

[0112] ③ Place the weighing bottle in a 1 / 100,000 precision analytical balance, close the hatch, and reset to zero;

[0113] ④ Weigh 0.17-0.19 grams of the sample to be tested into a container. Use a spoon to spread the material as thinly and evenly as possible to ensure that the test area does not affect the material's water absorption rate. Close the hatch, wait for 3-5 seconds for the sample to stabilize, then start the timer and record the mass of the analytical balance as the value at 0 minutes. Next, record the values ​​at 5, 10, 15, and 20 minutes. Calculate the average absorption data for 10-20 minutes to calculate the water absorption rate of the lithium-containing material containing the doped phase.

[0114] (3) A lithium-containing material containing a doped phase with a water absorption rate of 0 to 50 ppm / s is selected as a positive electrode lithium supplement additive.

[0115] Comparative Example A1

[0116] The comparative example provides a lithium-supplementing material, which is different from Examples 1-3, that is, a lithium-supplementing material that has not been doped.

[0117] Example B1 to Example B3

[0118] positive electrode

[0119] The lithium-supplementing materials provided in Examples A1 to A3 were mixed with polyvinylidene fluoride and SP in a mass ratio of 80:12:8 and stirred by ball milling to obtain a lithium-supplementing slurry. The lithium-supplementing slurry was coated on the surface of aluminum foil, rolled, and vacuum-dried at 110° C. overnight to obtain the positive electrode sheets of Examples B1 to B3, respectively.

[0120] Comparative Example B1

[0121] positive electrode

[0122] The lithium supplement material provided in Comparative Example A1 was mixed with polyvinylidene fluoride and SP in a mass ratio of 80:12:8 and ball-milled to obtain a lithium supplement slurry. The lithium supplement slurry was coated on the surface of aluminum foil, rolled, and vacuum-dried at 110° C. overnight to obtain the positive electrode sheets of Comparative Example B1.

[0123] Example C1 to Example C3

[0124] lithium-ion batteries

[0125] Lithium-ion battery assembly: Lithium-ion batteries are assembled in an inert atmosphere glove box in the order of lithium metal sheet-diaphragm-electrolyte-positive electrode sheet.

[0126] Positive electrode: the positive electrode sheets provided in Examples B1 to B3 respectively;

[0127] Negative electrode: lithium metal sheet;

[0128] Electrolyte: Ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7, and LiPF6 was added to form an electrolyte. The concentration of LiPF6 was 1 mol / L.

[0129] Diaphragm: Polypropylene microporous separator.

[0130] Comparative Example C1

[0131] lithium-ion batteries

[0132] Lithium-ion battery assembly: Lithium-ion batteries are assembled in an inert atmosphere glove box in the order of lithium metal sheet-diaphragm-electrolyte-positive electrode sheet.

[0133] Positive electrode: the positive electrode sheet provided in Comparative Example B1;

[0134] Negative electrode: lithium metal sheet;

[0135] Electrolyte: Ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7, and LiPF6 was added to form an electrolyte. The concentration of LiPF6 was 1 mol / L.

[0136] Diaphragm: Polypropylene microporous separator.

[0137] Property Test

[0138] (1) The water absorption rate of the positive electrode lithium supplement additives of Examples A1 to A3 and Comparative Example B1 was analyzed.

[0139] (2) The positive electrode plates of Examples B1 to B3 and Comparative Example B1 were placed in an environment with a humidity of 25%, and the specific capacity of the corresponding plates was tested from 0 h to 24 h. The water absorption weight gain rate of the plates after 24 h was recorded. At the same time, the state of the positive electrode slurry in each example was observed and recorded.

[0140] (III) The button batteries obtained in Examples C1 to C3 and Comparative Example C3 were charged at a constant current and constant voltage rate of 0.05 C to 4.3 V, with a cutoff current of 0.01 C, left for 5 min, and discharged at a rate of 0.05 C to 3.0 V. The relevant performance tests of the lithium-ion batteries were then performed.

[0141] Result Analysis

[0142] (1) The water absorption rate of the positive electrode lithium replenishing additives of Examples A1 to A3 and Comparative Example B1 was analyzed. As shown in Table 1, it can be seen that the preparation method of the positive electrode lithium replenishing additive provided by the present application is that the prepared lithium-containing material containing a doped phase is laid flat on an analytical balance, the mass at different time points from 0 to 60 minutes is recorded, and the water absorption rate of the lithium-containing material containing a doped phase is calculated. Further, lithium-containing materials containing a doped phase with water absorption rates of 1 to 15 ppm / s, 1-20 ppm / s, and 1-10 ppm / s are selected as positive electrode lithium replenishing additives; while the water absorption rate of the lithium-containing material provided in the comparative example is 55-65 ppm / s.

[0143] Table 1

[0144]

[0145] (2) The positive electrode plates of Examples B1 to B3 and Comparative Example B1 were placed in an environment with a humidity of 25%, and the specific capacity of the corresponding plates was tested from 0h to 24h. The water absorption weight gain rate of the plates was recorded after 24h. The state of the positive electrode slurry in each example was observed and recorded. As shown in Table 2, the plates obtained from Examples B1 to B3 were uniformly doped, the positive electrode slurry state was a normal mixture, and the 24h plate weight gain rates were 0.2%, 0.24%, and 0.1%, respectively. In contrast, the plate provided by Comparative Example B1 had a jelly-like positive electrode slurry state and a 24h plate weight gain rate of 20%. It can be seen that the plates obtained in the comparative example absorb a large amount of water, which is not conducive to assembly into a battery.

[0146] Table 2

[0147]

[0148] (III) The button batteries obtained in Examples C1 to C3 and Comparative Example C3 were charged to 4.3 V at a constant current and constant voltage rate of 0.05 C, with a cut-off current of 0.01 C, left for 5 min, and discharged to 3.0 V at a rate of 0.05 C. The relevant performance tests of the lithium-ion batteries were measured as shown in Table 3. It can be seen that the batteries obtained in Examples C1 to C3 had an initial charge capacity of 640 mAh / g, 630 mAh / g, and 645 mAh / g at 0 h, respectively; and an initial charge capacity of 637 mAh / g, 622 mAh / g, and 641 mAh / g at 24 h, respectively; while the battery obtained in Comparative Example C1 had an initial charge capacity of 252 mAh / g at 0 h, and an initial charge capacity of 113 mAh / g at 24 h. It can be seen that the secondary battery provided in the present application includes the provided positive electrode plate, and the positive electrode plate includes the positive electrode lithium replenishing additive prepared by the preparation method of the positive electrode lithium replenishing additive, ensuring that before being packaged to form a secondary battery, the positive electrode lithium replenishing additive in the positive electrode plate has good moisture resistance and is not affected by water vapor and carbon dioxide in the air, so that the lithium ions in the assembled secondary battery system are stable, the overall electrochemical performance of the battery is improved, and it has good cycle performance and lithium replenishing performance, which is conducive to wide use.

[0149] Table 3

[0150]

[0151] In summary, the positive electrode lithium replenishing additive provided includes a lithium-containing material and a doped phase present in the bulk phase of the lithium-containing material. After the lithium-containing material containing the doped phase is prepared, a water absorption test is also carried out, and a lithium-containing material containing a doped phase with a water absorption rate of 0 to 50 ppm / s is selected as the positive electrode lithium replenishing additive to ensure that the obtained positive electrode lithium replenishing additive has good moisture resistance and that the doping effect of the doped phase is good, so that the obtained battery properties are excellent and the entire battery will not be scrapped.

[0152] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A positive electrode lithium supplement additive, characterized in that: The positive electrode lithium supplement additive includes a lithium-containing material and a doping phase present in the bulk phase of the lithium-containing material, wherein the lithium-containing material is Li5FeO4, and the water absorption rate of the positive electrode lithium supplement additive is 0-50 ppm / s; wherein the water absorption rate is tested as follows: the positive electrode lithium supplement additive is loosely and flatly placed on an analytical balance, and the mass is recorded every 5 minutes from 0 to 60 minutes; the placement conditions of the analytical balance are controlled as follows: standard atmospheric pressure, temperature of 23-27°C, relative humidity controlled between 10% and 50%, and the relative humidity variation range is less than 5%, the weight of the positive electrode lithium supplement additive is 0.1-1 g, and the flat thickness is 0.01-0.3 cm; the water absorption rate is calculated as follows: V=(wt2-wt1) / w0*(t2-t1); Wherein, w0 is the added mass of the sample, wt1 is the mass of the sample after the standing time t1, wt2 is the mass of the sample after the standing time t2, and t1 and t2 are the standing times; The doping element in the doping phase includes any one of a combination of Al and Ni, a combination of Zr and Mn, and Si; the doping element is bulk doped; covalent bonds containing the doping element exist inside the lithium-containing material, and the content of the doping element is 1% to 10%.

2. A method for preparing a positive electrode lithium supplement additive, characterized in that: The steps include: Providing a lithium-containing material containing a doped phase; the lithium-containing material is Li5FeO4, and the doping element in the doped phase includes any one of a combination of Al and Ni, a combination of Zr and Mn, and Si; the doping element is bulk doped; The lithium-containing material containing the doped phase is placed loosely and flatly on an analytical balance, the mass at different time points from 0 to 60 minutes is recorded, and the water absorption rate of the lithium-containing material containing the doped phase is calculated; The lithium-containing material containing the doped phase and having a water absorption rate of 0-50 ppm / s is selected as the positive electrode lithium supplement additive.

3. The method for preparing the positive electrode lithium supplement additive according to claim 2, characterized in that: In the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the placement conditions of the analytical balance are controlled as follows: standard atmospheric pressure, temperature of 23-27° C., and relative humidity controlled between 10% and 50%.

4. The method for preparing the positive electrode lithium supplement additive according to claim 3, characterized in that: The relative humidity variation range is less than 5%.

5. The method for preparing the positive electrode lithium supplement additive according to claim 3, characterized in that: The relative humidity is selected from 20-25% or 30-35%.

6. The method for preparing the positive electrode lithium supplement additive according to any one of claims 2 to 5, characterized in that: In the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the weight of the lithium-containing material containing the doped phase is 0.1 to 1 gram.

7. The method for preparing the positive electrode lithium supplement additive according to any one of claims 2 to 5, characterized in that: In the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the flat thickness of the lithium-containing material containing the doped phase is 0.01 to 0.3 cm.

8. The method for preparing the positive electrode lithium supplement additive according to any one of claims 2 to 5, characterized in that: The step of recording the mass at different times from 0 to 60 minutes includes: recording the mass at every 5-minute interval from 0 to 60 minutes.

9. The method for preparing the positive electrode lithium supplement additive according to any one of claims 2 to 5, characterized in that: In the step of calculating the water absorption rate of the lithium-containing material containing the doped phase, the calculation formula of the water absorption rate is: V=(in t2 -In t1 ) / w0*(t2-t1); Among them, w0 is the mass of sample added, w t1 is the mass of the sample after the placement time t1, w t2 is the mass of the sample after the placement time t2, t1 and t2 are the placement time.

10. A positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, a binder, a conductive agent and a positive electrode lithium replenishing additive, wherein the positive electrode lithium replenishing additive is selected from the positive electrode lithium replenishing additive according to claim 1 or prepared by the preparation method of the positive electrode lithium replenishing additive according to any one of claims 2 to 9.

11. A secondary battery, characterized in that: The secondary battery comprises the positive electrode sheet according to claim 10 .

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