CN115548312A - A kind of preparation method and application of porous structure additive coating ternary material - Google Patents

Abstract

A preparation method and application of a porous structure additive-coated ternary material. The invention belongs to the field of lithium-ion battery cathode materials, and in particular relates to the synthesis of a nickel-doped strontium carbonate additive-coated ternary material, its preparation method and its use in lithium-ion batteries. In the porous structure Ni@SrTiO _3‑x synthesized by the present invention, the doping of nickel induces the formation of oxygen vacancies, which makes the surface coordination of strontium titanate unsaturated, generates more lone pairs of electrons, improves the conductivity of the material, and the porous structure includes Covering the surface of the ternary material effectively suppresses the side reaction between the ternary material and the electrolyte, and the stable structure can form a stable ion channel, reducing the lattice breakage of the ternary material during the discharge process, and the present invention is based on the synthesized Ni@SrTiO _3‑x additives were coated with different systems of ternary materials, and the electrochemical tests were performed on them, which showed stable electrochemical performance, which effectively proved the feasibility of the coating scheme.

Description

A kind of preparation method and application of porous structure additive coating ternary material

technical field

The invention belongs to the technical field of lithium-ion battery cathode materials, in particular, designing and synthesizing a porous structure additive-coated ternary material, and further disclosing its preparation method and application for preparing lithium-ion batteries.

Background technique

In recent years, the greenhouse effect caused by global warming has caused a series of environmental problems, such as rising sea levels and melting glaciers. It has become an international consensus to develop new energy sources and replace fuel vehicles with electric vehicles. Since the commercialization of lithium-ion batteries, the advantages of high voltage, high specific energy, no pollution, small self-discharge and good safety performance have made it shine in the new energy industry. Lithium has also been honored as an energy element. In lithium-ion batteries, the cathode material is the most costly component and the most critical material for the electrochemical performance of lithium-ion batteries, which plays a decisive role in the capacity, cycle performance and safety of the battery.

At present, the anode materials of lithium-ion batteries mainly include pointed polyanions and transition metal oxides, such as LiFePO ₄ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , etc. Among them, LiFePO ₄ occupies the material due to its stable cycle ability and high safety. The dominant position in the market, but the low theoretical specific capacity has been unable to meet the development needs of high energy consumption and high power. Nickel-cobalt lithium manganese oxide ternary material combines the advantages of LiCoO ₂ , LiNiO ₂ , and LiMnO ₂ . Because of its high energy density and high discharge specific capacity, it can effectively meet the energy needs of future high-power and high-power consumption devices. However, ternary materials have lithium-nickel mixed discharge during charge and discharge, side reactions between Ni ⁴⁺ and electrolyte, and as the ternary material decreases with the cobalt content, the problem of poor conductivity is also beginning to be exposed.

For this reason, the problem to be solved by the present invention lies in the poor electrical conductivity of the low-cobalt ternary material. Synthesizing a porous structure additive coated low-cobalt ternary material can effectively improve the conductivity of the positive electrode material and increase the rate of the material. performance. Strontium carbonate has the characteristics of abundant reserves, low price, non-toxicity, and good chemical stability, and low-bandgap semiconductor oxides are easy to form oxygen vacancies through element doping, which makes the electronic coordination imbalance and improves conductivity. The porous structure can provide stable ion channels, and can also provide effective support for solid-state batteries to solve ion transport between interfaces.

Contents of the invention

The porous structure additive synthesized by the present invention has the following characteristics of Ni@SrTiO _3-x , wherein 0<x<3; the SEM image of the additive has obvious porous structure.

The present invention also discloses a synthesis method of porous structure additive Ni@SrTiO _3-x , including the following steps:

(1) Add strontium carbonate to deionized water containing citric acid, stir (such as ultrasonic stirring) until completely dissolved, and then add basic nickel carbonate to the solution, which is designated as solution A;

(2) Mix butyl titanate with glacial acetic acid, slowly add deionized water after stirring, and keep stirring as solution B;

(3) Slowly add solution A dropwise to continuously stirring solution B, after continuously stirring, add surfactant polyethylene glycol, continue stirring, after airtight heating, open to remove water, and then dry to prepare a powder sample;

(4) After the powder sample prepared above is ground evenly, it is calcined under a nitrogen atmosphere, and then switched to oxygen calcination to prepare Ni@SrTiO _3-x with a porous structure;

(5) The Ni@SrTiO _3-x prepared above and the ternary material LiNi _x Co _y Mn _1-xy O ₂ (where 0<x<1, 0<x+y<1) are mixed uniformly and then placed in the air atmosphere Carry out calcined coating.

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

Wherein, in step (2), the amount of strontium carbonate and the amount of butyl titanate in the step (2) are 1:1 according to the molar ratio of metal elements; the amount of glacial acetic acid is controlled at 60-120ml; stir for 1-3 hours ; The amount of deionized water added is 10-100ml.

Wherein, in the step (3), in the step (3), the solution A is slowly added dropwise to the continuously stirred solution B, and the continuous stirring time is 1 to 3 hours; the surfactant polyethylene glycol is PEG6000, and the amount of PEG6000 is the same as The mass ratio of citric acid is 1:2-4; the closed heating temperature is between 60-80°C, and the heating time is controlled at 4-8h; the final drying temperature of the powder sample is controlled between 110-150°C.

Wherein, 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 hours; the flow rate of the oxygen atmosphere is controlled at 1-10 L/min, and the calcination temperature The temperature is controlled at 300-450°C, and the calcination time is controlled at 1-5 hours.

Wherein, in step (5), the coating mass ratio of Ni@SrTiO _3-x to ternary material LiNi _x Co _y Mn _1-xy O ₂ (wherein 0<x<1, 0<x+y<1) is between 0.01%-1%, the flow rate of the air atmosphere is controlled at 1-6L/min, the calcination temperature is controlled at 300-500°C, and the calcination time is controlled at 3-6h.

The present invention also relates to the application of the above-mentioned nickel-doped strontium titanate additive-coated ternary material or the porous-structure additive-coated ternary positive electrode material obtained by the above-mentioned preparation method as a lithium-ion battery positive pole piece in a button battery . Specifically, the present invention also discloses that the synthetic porous structure additive coated ternary positive electrode material is used for preparing lithium ion battery positive pole pieces and button batteries for testing.

Preferably, the lithium-ion battery button battery model is selected from CR2032, and the prepared porous structure additive coats the ternary positive electrode material, binder (PVDF), and conductive carbon black according to a certain mass ratio (for example, the ratio of 9.5:0.5:0.5 ) is accurately weighed, mixed evenly, and NMP (N-methylpyrrolidone) is added dropwise to prepare a viscous slurry, which is coated on an aluminum foil, vacuum-dried (for example, 60°C vacuum-dried for 24 hours), and punched into a diameter of It is a 10mm pole piece, which is stored in the glove box to assemble the button battery.

Beneficial effects of the present invention:

The porous structure additive of the present invention coats the ternary material, has stable structural characteristics, facilitates the rapid transmission of lithium ions, and reduces battery polarization; coats the surface of the ternary material, effectively reduces the occurrence of side reactions, and improves the first effect of the battery And cycle performance; and the porous structure has an obvious effect on solving the interface ion transport of solid-state batteries and reducing polarization, and it also has a good reference value for the subsequent development of solid-state batteries.

Description of drawings

In order to make the content of the present invention more vivid and easy to understand, the present invention will be further described in detail below in conjunction with specific embodiments of the present invention and in conjunction with the accompanying drawings, wherein,

FIG. 1 is a schematic SEM microscopic view of the porous structure additive prepared in Example 1.

detailed description

In order to facilitate the understanding of the present invention, various exemplary embodiments of the present invention are now described in detail. The detailed description should not be regarded as a specific limitation of the present invention, but should be understood as a description of certain aspects, characteristics and embodiments of the present invention. A more detailed description.

Example 1

Add 230g of 60wt% citric acid into 500ml deionized water, stir evenly, then add 29.23g strontium carbonate to the solution and disperse evenly, add 0.25g basic nickel carbonate, stir evenly and record it as solution A; 68.76g butyl titanate and After mixing 20ml of glacial acetic acid, stir it for 3 hours and slowly add it dropwise to 30ml of deionized solution. After stirring for 2 hours, it will be recorded as solution B; slowly pour solution A into solution B that has been stirring continuously, and after stirring continuously for 1 hour, add 115g of PEG6000 into the solution , continue to stir for 2 hours, continue to stir and heat to 65 ° C, keep it sealed for 8 hours, then open it to remove most of the water, dry it in a vacuum oven at 120 ° C, and grind the powder sample.

Transfer the sample prepared above to a sagger, heat in an atmosphere muffle furnace, first pass 5L/min of nitrogen, control the temperature rise at 5°C/min, heat to 850°C and keep it for 6 hours, then cool down to 450°C to switch to oxygen The atmosphere was kept warm for 2 hours to prepare a porous structure Ni@SrTiO _3-x , wherein the nickel doping amount was 1%. The SEM microscopic schematic diagram is shown in Figure 1. It can be seen that there is an obvious porous structure with many pores distributed, and the pore size is about 300-400nm. Elemental mapping also confirms the incorporation of nickel.

The ternary material used in this embodiment is LiNi _0.65 Co _0.15 Mn _0.2 O ₂ , the coating additive is Ni@SrTiO _3-x prepared above, and the nickel doping amount is 1%. The mass ratio of coating dosage additive to ternary material is 0.4%. After accurate weighing and mixing, put it into a sagger, put it into an atmosphere muffle furnace at 470°C, and keep it warm for 6 hours in an air atmosphere.

Button half-cell test: The above-mentioned coated ternary material, binder (PVDF), and conductive carbon black are accurately weighed according to the ratio of mass ratio 9.5:0.5:0.5, and NMP (N-formazan) is added dropwise after mixing evenly. Base pyrrolidone) was prepared into a viscous slurry, coated on the aluminum foil, dried in vacuum at 60°C for 24 hours, punched into pole pieces with a diameter of 10mm, and stored in a glove box to assemble a button battery. In a constant temperature environment of 25°C, the discharge voltage is 3.0-4.3V, and the charge-discharge test is carried out under the conditions of 0.1C.

In comparative example 1, the deduction test was carried out except that the ternary material was different, and the other conditions were kept the same. In the comparative example, the uncoated ternary material LiNi _0.65 Co _0.15 Mn _0.2 O ₂ was used.

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

Table 1 Charge and discharge test results

It can be seen that in the porous structure Ni@SrTiO _3-x synthesized by the present invention, the doping of nickel induces the formation of oxygen vacancies, because the surface coordination of strontium titanate is unsaturated, more lone pair electrons are generated, and the conductivity of the material is improved. 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, and the stable structure can form a stable ion channel, reducing the lattice breakage of the ternary material during the discharge process; improving the performance of the battery It can be seen from the capacity after 100 cycles that the cycle performance has been significantly improved.

Example 2

Add 230g of 60wt% citric acid into 500ml deionized water, stir evenly, then add 29.23g strontium carbonate to the solution and disperse evenly, add 0.25g basic nickel carbonate, stir evenly and record it as solution A; 68.76g butyl titanate and After mixing 20ml of glacial acetic acid, stir it for 3 hours and slowly add it dropwise to 30ml of deionized solution. After stirring for 2 hours, it will be recorded as solution B; slowly pour solution A into solution B that has been stirring continuously, and after stirring continuously for 1 hour, add 115g of PEG6000 into the solution , continue to stir for 2 hours, continue to stir and heat to 65 ° C, keep it sealed for 8 hours, then open it to remove most of the water, dry it in a vacuum oven at 120 ° C, and grind the powder sample.

Transfer the sample prepared above to a sagger, heat in an atmosphere muffle furnace, first pass 5L/min of nitrogen, control the temperature rise at 5°C/min, heat to 850°C and keep it for 6 hours, then cool down to 450°C to switch to oxygen The atmosphere was kept warm for 2 hours to prepare a porous structure Ni@SrTiO _3-x , wherein the nickel doping amount was 1%.

The ternary material used in this example is LiNi _0.72 Co _0.05 Mn _0.23 O ₂ , the coating additive is Ni@SrTiO _3-x prepared above, and the nickel doping amount is 1%. The mass ratio of coating dosage additive to ternary material is 0.3%. After accurate weighing and mixing, put it into a sagger, put it into an atmosphere muffle furnace at 470°C, and keep it warm for 6 hours in an air atmosphere.

The test of the button half-cell, embodiment 2 is that the above-mentioned coated ternary material, binder (PVDF), and conductive carbon black are accurately weighed according to the ratio of mass ratio 9.5:0.5:0.5, and NMP is added dropwise after mixing (N-methylpyrrolidone), prepared into a viscous slurry, coated on the aluminum foil, dried in vacuum at 60°C for 24 hours, punched into pole pieces with a diameter of 10mm, and stored in a glove box to assemble a button battery. In a constant temperature environment of 25°C, the discharge voltage is 3.0-4.35V, and the charge-discharge test is carried out under the conditions of 0.1C.

In comparative example 2, except for the difference in the ternary material, other conditions were kept the same in the button-down test, in which the uncoated ternary material LiNi _0.72 Co _0.05 Mn _0.23 O ₂ was used in the comparative example.

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

Table 2 Charge and discharge test results

It can be seen that the porous structure Ni@SrTiO _3-x synthesized by the present invention is coated on the surface of the ternary material, effectively suppressing the side reaction between the ternary material and the electrolyte, and the stable structure can form a stable ion channel, reducing the three The crystal lattice of the primary material is broken during the discharge process; the first effect of the battery is improved; it can be seen from the capacity after 100 cycles that the cycle performance has been significantly improved.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (8)

1. A method for preparing a nickel-doped strontium titanate additive-coated ternary material, characterized in that it comprises the following preparation steps: (1) Add strontium carbonate to deionized water containing citric acid, stir until completely dissolved, and then add basic nickel carbonate to the solution, which is designated as solution A; (2) Mix butyl titanate with glacial acetic acid, slowly add deionized water after stirring, and keep stirring as solution B; (3) Slowly add solution A dropwise to continuously stirring solution B, after continuously stirring, add surfactant polyethylene glycol, continue stirring, after airtight heating, open to remove water, and then dry to prepare a powder sample; (4) After the powder sample prepared above is ground evenly, it is calcined under a nitrogen atmosphere, and then switched to oxygen calcination to prepare Ni@SrTiO _3-x with a porous structure; (5) The Ni@SrTiO _3-x prepared above and the ternary material LiNi _x Co _y Mn _1-xy O ₂ (where 0<x<1, 0<x+y<1) are mixed uniformly and then placed in the air atmosphere Carry out calcined coating. 2. The preparation method of a nickel-doped strontium titanate additive-coated ternary material according to claim 1, wherein the molar concentration of citric acid in deionized water in step (1) is 0.05～1mol/L; The doping amount of basic nickel carbonate is between 0.01% and 5% of the mass of strontium carbonate. 3. the preparation method of a kind of nickel-doped strontium titanate additive coating ternary material according to claim 1, is characterized in that, in the step (1), the strontium carbonate consumption is the same as that of the butyl titanate in the described step (2). The dosage is 1:1 according to the molar ratio of metal elements. 4. the preparation method of a kind of nickel-doped strontium titanate additive-coated ternary material according to claim 1, is characterized in that, in step (3), solution A is slowly added dropwise in the solution B of continuous stirring, Stir continuously for 1 to 3 hours; the surfactant polyethylene glycol is PEG6000, and the mass ratio of the amount of PEG6000 to citric acid is between 1:2 and 4; the heating temperature in an airtight environment is between 60 and 80°C, and the heating time is controlled In 4-8 hours; the drying temperature of the final powder sample is controlled between 110-150°C. 5. A method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, wherein the flow rate of the nitrogen atmosphere in step (4) is controlled at 1 to 10 L/min, and the calcination temperature is controlled At 700-900°C, the calcination time is controlled at 5-9h; the flow rate of the oxygen atmosphere is controlled at 1-10L/min, the calcination temperature is controlled at 300-450°C, and the calcination time is controlled at 1-5h. 6. A method for preparing a nickel-doped strontium titanate additive-coated ternary material according to claim 1, characterized in that in step (5), Ni@SrTiO _3-x and the ternary material LiNi _x Co _y Mn _1-xy O ₂ (wherein 0<x<1, 0<x+y<1) the mass ratio of the coating amount is between 0.01% and 1%, the flow rate of the air atmosphere is controlled at 1-6L/min, the calcination temperature The temperature is controlled at 300-500°C, and the calcination time is controlled at 3-6 hours. 7. The preparation method according to claim 1-6 obtains the application of the porous structure additive coated ternary positive electrode material as the positive pole piece of the lithium ion battery in the button battery. 8. The application according to claim 7, the model of the button battery is preferably CR2032.

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