Preparation method and application of porous structure additive-coated ternary material

Abstract

A preparation method and application of a porous structure additive-coated ternary material. The present invention belongs to the field of lithium-ion battery positive electrode materials, and in particular relates to a synthesized nickel-doped strontium carbonate additive-coated ternary material, a preparation method thereof, and its application in lithium-ion batteries. The porous structure Ni@SrTiO synthesized by the present invention 3‑x The nickel doping induces the formation of oxygen vacancies, making the surface coordination of strontium titanate unsaturated, generating more lone pairs of electrons, and improving the conductivity of the material. The porous structure is coated on the surface of the ternary material, effectively inhibiting the side reaction between the ternary material and the electrolyte. The stable structure can form a stable ion channel, reducing the lattice rupture of the ternary material during the discharge process. In addition, the present invention is based on the synthesized Ni@SrTiO 3‑x The additives were coated with ternary materials of different systems and subjected to a charge-discharge test, which showed stable electrochemical properties and effectively proved the feasibility of the coating scheme.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials for lithium-ion batteries, and in particular relates to the synthesis of a porous structure additive-coated ternary material, and further discloses its preparation method and use for preparing lithium-ion batteries. Background Art

[0002] Since the commercialization of lithium-ion batteries, they have shone brightly in the new energy industry due to their advantages such as high voltage, high specific energy, pollution-free, low self-discharge, and good safety performance. Lithium has also been honored as an energy element. The cathode material in a lithium-ion battery is the most costly component and also the most crucial material for the electrochemical performance of the lithium battery, playing a decisive role in the capacity, cycle performance, and safety of the battery.

[0003] Currently, the main cathode materials for lithium-ion batteries are olivine-type and transition metal oxides, such as LiFePO4, LiCoO2, LiNiO2, LiMnO2, etc. Among them, LiFePO4 occupies the main position in the material market with its stable cycling ability and high safety, but its low theoretical specific capacity has been unable to meet the development needs of high energy consumption and high power. The lithium nickel cobalt manganese ternary material combines the advantages of LiCoO2, LiNiO2, and LiMnO2. Due to its high energy density and high discharge specific capacity, it can effectively meet the energy needs of future high-power and high-consumption devices. However, there are lithium-nickel mixing and side reactions between Ni 4+ and the electrolyte during the charge and discharge process of the ternary material, and with the decrease of the cobalt content in the ternary material, the problem of poor conductivity also begins to emerge.

[0004] Therefore, the problem to be solved by the present invention is the poor conductivity of the low-cobalt ternary material. A porous structure additive-coated low-cobalt ternary material is synthesized, which can effectively improve the conductivity of the cathode material and enhance the rate performance of the material. Strontium carbonate has the characteristics of rich reserves, low price, non-toxicity, good chemical stability, etc., and is a low-bandgap semiconductor oxide. Oxygen defects are easily formed through element doping, making the electron coordination unbalanced and thus improving the conductivity. The porous structure can provide stable ion channels and can also effectively support the ion transport between interfaces for solid-state batteries. Summary of the Invention

[0005] The porous structure additive synthesized by the present invention has the following Ni@SrTiO 3-x characteristics, where 0 < x < 3; the SEM image of the additive has an obvious porous structure.

[0006] The present invention also discloses a synthesis method of the porous structure additive Ni@SrTiO 3-x which includes the following steps:

[0007] (1) Add strontium carbonate to deionized water containing citric acid, and stir (e.g., stir by ultrasonic wave) until it is completely dissolved. Then add nickel basic carbonate to the solution, denoted as solution A;

[0008] (2) Mix tetrabutyl titanate and glacial acetic acid, stir, and then slowly add deionized water, and keep stirring, denoted as solution B;

[0009] (3) Slowly drip solution A into solution B under continuous stirring. After continuous stirring, add the surfactant polyethylene glycol, continue stirring, heat it in a closed state, then open it to remove water, and then dry it to prepare a powder sample;

[0010] (4) After grinding the above-prepared powder sample evenly, calcine it under a nitrogen atmosphere, and then switch to an oxygen atmosphere for calcination to prepare a porous structure of Ni@SrTiO 3-x ;

[0011] (5) The above-prepared Ni@SrTiO 3-x and the ternary material LiNi x Co y Mn<00利用本发明的方法制备的Ni@SrTiO 1-x-y O2 (where 0 < x < 1, 0 < x + y < 1), mix them evenly and then calcine and coat them under an air atmosphere.

[0012] Among them, in step (1), the molar concentration of citric acid in deionized water is 0.05 - 1 mol / L; the doping amount of nickel basic carbonate is controlled at 1% - 5% of the mass of strontium carbonate.

[0013] Among them, in step (2), the dosage of strontium carbonate and the dosage of tetrabutyl titanate in step (2) are in a metal element molar ratio of 1:1; the dosage of glacial acetic acid is controlled at 60 - 120 ml; stir for 1 - 3 hours; the added amount of deionized water is 10 - 100 ml.

[0014] Among them, in step (3), in step (3), slowly drip solution A into solution B under continuous stirring, and the continuous stirring time is 1 - 3 hours; the surfactant polyethylene glycol is PEG6000, and the mass ratio of the dosage of PEG6000 to the mass of citric acid is between 1:2 - 4; the closed heating temperature is between 60 - 80 °C, and the heating time is controlled at 4 - 8 h; the drying temperature of the final powder sample is controlled between 110 - 150 °C.

[0015] Among them, in step (4), the flow rate of the nitrogen atmosphere is controlled at 1 - 10 L / min, the calcination temperature is controlled at 700 - 900 °C, and the calcination time is controlled at 5 - 9 h; the flow rate of the oxygen atmosphere is controlled at 1 - 10 L / min, the calcination temperature is controlled at 300 - 450 °C, and the calcination time is controlled at 1 - 5 h.

[0016] Among them, in step (5), Ni@SrTiO3-x With the ternary material LiNi x Co y Mn 1-x-y O2 (where 0 < x < 1, 0 < x + y < 1), the coating dosage mass ratio is between 0.01% and 1%, the flow rate of the air atmosphere is controlled at 1 - 6 L / min, the calcination temperature is controlled at 300 - 500 °C, and the calcination time is controlled at 3 - 6 h.

[0017] The present invention also relates to the application of a nickel-doped strontium titanate additive-coated ternary material or a porous structure additive-coated ternary cathode material obtained by the above preparation method as a cathode electrode of a lithium-ion battery in a button cell. Specifically, the present invention also discloses the use of the synthesized porous structure additive-coated ternary cathode material for preparing a cathode electrode of a lithium-ion battery and testing with a button cell.

[0018] Preferably, the button cell model of the lithium-ion battery is selected as CR2032. The prepared porous structure additive-coated ternary cathode material, binder (PVDF), and conductive carbon black are accurately weighed according to a certain mass ratio (such as a ratio of 9.5:0.5:0.5), mixed evenly, and then NMP (N-methylpyrrolidone) is added dropwise to prepare a viscous slurry, which is coated on the aluminum foil, vacuum dried (such as vacuum drying at 60 °C for 24 hours), punched into a pole piece with a diameter of 10 mm, for example, and stored in a glove box to assemble a button cell.

[0019] Advantages of the present invention:

[0020] The porous structure additive-coated ternary material of the present invention has stable structural characteristics, which is conducive to the rapid transmission of lithium ions and reduces battery polarization; coated on the surface of the ternary material, it effectively reduces the occurrence of side reactions and improves the initial efficiency and cycle performance of the battery; and the porous structure has an obvious effect on solving the interfacial ion transport in the solid-state battery and reducing polarization, and also has good reference value for the subsequent development of solid-state batteries. Brief Description of the Drawings

[0021] To make the content of the present invention more vivid and easy to understand, the following further describes the present invention in detail in combination with specific embodiments of the present invention and with reference to the drawings, where

[0022] Figure 1 Figure is the SEM micrograph of the porous structure additive prepared in Example 1. Detailed Embodiments

[0023] To facilitate the understanding of the present invention, various exemplary embodiments of the present invention are now described in detail. This detailed description should not be regarded as a specific limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0024] Example 1

[0025] 230g of 60wt% citric acid was added to 500ml of deionized water and stirred evenly. Then, 29.23g of strontium carbonate was added to the solution and dispersed evenly. Then, 0.25g of basic nickel carbonate was added and stirred evenly, which was recorded as solution A. 68.76g of butyl titanate was mixed with 20ml of glacial acetic acid, stirred for 3h, and then slowly added dropwise to 30ml of deionized water and stirred for 2 hours, which was recorded as solution B. Solution A was slowly poured into the stirred solution B, and after continuous stirring for 1h, 115g of PEG6000 was added to the solution, and continuous stirring was continued for 2h. After continuous stirring, it was heated to 65°C, kept sealed for 8h, and then opened to remove most of the moisture. The sample was dried in a vacuum drying oven at 120°C and ground into a powder.

[0026] The prepared sample was transferred to a sagger and heated in a muffle furnace. Nitrogen was introduced at a rate of 5 L / min, and the temperature was raised at a rate of 5 °C / min. The sample was heated to 850 °C and kept warm for 6 hours. The sample was then cooled to 450 °C and switched to an oxygen atmosphere and kept warm for 2 hours to prepare a porous Ni@SrTiO 3-x , where the nickel doping amount is 1%. SEM micrograph is shown as Figure 1 As shown, it can be seen that the structure is obviously porous with many pores distributed, and the pore size is about 300 to 400 nm. Element mapping also confirms the incorporation of nickel.

[0027] The ternary material used in this embodiment is LiNi 0.65 Co 0.15 Mn 0.2 O2, the coating additive is Ni@SrTiO prepared as above 3-x The nickel doping content is 1%. The mass ratio of the coating additive to the ternary material is 0.4%. After accurate weighing and mixing, put it into a sagger and place it in an atmosphere muffle furnace at 470℃ under air atmosphere for 6 hours.

[0028] Coin-type half-cell testing: The aforementioned ternary material, binder (PVDF), and conductive carbon black were accurately weighed in a mass ratio of 9.5:0.5:0.5, mixed thoroughly, and NMP (N-methylpyrrolidone) was added dropwise to form a viscous slurry. The slurry was then coated onto aluminum foil and vacuum-dried at 60°C for 24 hours. Electrodes with a diameter of 10 mm were then punched out and assembled into button-type cells in a glove box. Charge and discharge tests were conducted at a constant temperature of 25°C, with a discharge voltage of 3.0 to 4.3 V and a charge / discharge rate of 0.1C.

[0029] Comparative Example 1: Except for the different ternary materials, other conditions remain the same. The comparative example uses the uncoated ternary material LiNi 0.65 Co 0.15 Mn 0.2O2.

[0030] The button-type half-cells prepared in Example 1 and Comparative Example 1 were tested respectively, and the test results are shown in Table 1.

[0031] Table 1 Charge and discharge test results

[0032]

[0033] It can be seen that the porous structure Ni@SrTiO synthesized by the present invention 3-x The doping of nickel induces the formation of oxygen vacancies, which is due to the unsaturated coordination of the strontium titanate surface, producing more lone pairs of electrons, thereby improving the conductivity of the material. The porous structure is coated on the surface of the ternary material, which effectively inhibits the side reaction between the ternary material and the electrolyte. The stable structure can form a stable ion channel, reducing the lattice rupture of the ternary material during the discharge process; it improves the first efficiency of the battery. It can be seen from the capacity after 100 cycles that the cycle performance has been significantly improved.

[0034] Example 2

[0035] 230g of 60wt% citric acid was added to 500ml of deionized water and stirred evenly. Then, 29.23g of strontium carbonate was added to the solution and dispersed evenly. Then, 0.25g of basic nickel carbonate was added and stirred evenly, which was recorded as solution A. 68.76g of butyl titanate was mixed with 20ml of glacial acetic acid, stirred for 3h, and then slowly added dropwise to 30ml of deionized water and stirred for 2 hours, which was recorded as solution B. Solution A was slowly poured into the stirred solution B, and after continuous stirring for 1h, 115g of PEG6000 was added to the solution, and continuous stirring was continued for 2h. After continuous stirring, it was heated to 65°C, kept sealed for 8h, and then opened to remove most of the moisture. The sample was dried in a vacuum drying oven at 120°C and ground into a powder.

[0036] The prepared sample was transferred to a sagger and heated in a muffle furnace. Nitrogen was introduced at a rate of 5 L / min, and the temperature was raised at a rate of 5 °C / min. The sample was heated to 850 °C and kept warm for 6 hours. The sample was then cooled to 450 °C and switched to an oxygen atmosphere and kept warm for 2 hours to prepare a porous Ni@SrTiO 3-x , where the nickel doping amount is 1%.

[0037] The ternary material used in this embodiment is LiNi 0.72 Co 0.05 Mn 0.23 O2, the coating additive is Ni@SrTiO prepared as above 3-x The nickel doping content is 1%. The mass ratio of the coating additive to the ternary material is 0.3%. After accurate weighing and mixing, put it into a sagger and place it in an atmosphere muffle furnace at 470℃ under air atmosphere for 6 hours.

[0038] In Example 2, the button-type half-cell test involved accurately weighing the aforementioned coated ternary material, binder (PVDF), and conductive carbon black in a mass ratio of 9.5:0.5:0.5. After mixing thoroughly, NMP (N-methylpyrrolidone) was added dropwise to form a viscous slurry. The slurry was then coated on aluminum foil, vacuum-dried at 60°C for 24 hours, and punched into 10mm diameter electrode pieces. The coin-type cell was assembled in a glove box. Charge and discharge tests were conducted at a constant temperature of 25°C, with a discharge voltage of 3.0-4.35V and a charge / discharge rate of 0.1C.

[0039] Comparative Example 2: Except for the different ternary materials, other conditions remain the same. The comparative example uses the uncoated ternary material LiNi 0.72 Co 0.05 Mn 0.23 O2.

[0040] The button-type half-cells prepared in Example 2 and Comparative Example 2 were tested respectively, and the test results are shown in Table 2.

[0041] Table 2 Charge and discharge test results

[0042]

[0043] It can be seen that the porous structure Ni@SrTiO synthesized by the present invention 3-x The porous structure is coated on the surface of the ternary material, which effectively inhibits the side reaction between the ternary material and the electrolyte. The stable structure can form a stable ion channel, reduce the lattice rupture of the ternary material during the discharge process, and improve the initial efficiency of the battery. It can be seen from the capacity after 100 cycles that the cycle performance has been significantly improved.

[0044] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-doped strontium titanate additive-coated ternary material, characterized in that: The method comprises the following preparation steps: (1) Strontium carbonate was added to deionized water containing citric acid and stirred until completely dissolved. Then, basic nickel carbonate was added to the solution, which was recorded as solution A. (2) Mix butyl titanate and glacial acetic acid, stir, and then slowly add deionized water, and continue stirring. This is solution B. (3) Solution A was slowly added dropwise to the continuously stirred solution B. After continuous stirring, the surfactant polyethylene glycol was added and the stirring was continued. After heating in a sealed container, the container was opened to remove moisture and then dried to obtain a powder sample. (4) The powder sample prepared above was ground evenly and calcined under nitrogen atmosphere, and then switched to oxygen calcination to prepare porous Ni@SrTiO 3-x ; (5) The prepared Ni@SrTiO 3-x and the ternary material LiNi x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < x + y < 1, are mixed evenly and then calcined and coated in an air atmosphere; Among them, in step (5), Ni@SrTiO 3-x and the ternary material LiNi x Co y Mn 1-x-y O 2， where 0 < x < 1, 0 < x + y < 1, the coating dosage mass ratio is 0.01% to 1%; The doping amount of basic nickel carbonate is 0.01% to 5% of the mass of strontium carbonate.

2. The method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that: The molar concentration of citric acid in deionized water in step (1) is 0.05~1 mol / L.

3. The method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that: The amount of strontium carbonate used in step (1) and the amount of butyl titanate used in step (2) are in a molar ratio of 1:1 according to the metal elements.

4. The method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that: In step (3), solution A is slowly added dropwise to solution B which is continuously stirred, and the stirring time is 1 to 3 hours; the surfactant polyethylene glycol is PEG6000, and the mass ratio of PEG6000 to citric acid is 1:2 to 4; the sealed heating temperature is 60 to 80°C, and the heating time is controlled at 4 to 8 hours; and finally, the drying temperature of the powder sample is controlled at 110 to 150°C.

5. The method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that: In step (4), the flow rate of the nitrogen atmosphere is controlled at 1-10 L / min, the calcination temperature is controlled at 700-900°C, and the calcination time is controlled at 5-9 h; the flow rate of the oxygen atmosphere is controlled at 1-10 L / min, the calcination temperature is controlled at 300-450°C, and the calcination time is controlled at 1-5 h.

6. The method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that: In step (5), the flow rate of the air atmosphere is controlled at 1-6 L / min, the calcination temperature is controlled at 300-500° C., and the calcination time is controlled at 3-6 h.

7. Use of the porous structure additive-coated ternary positive electrode material obtained by the preparation method according to any one of claims 1 to 6 as a positive electrode sheet for lithium-ion batteries in button batteries.

8. The use according to claim 7, wherein the button battery model is CR2032.

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