CN110085828A - A kind of anode material for lithium-ion batteries and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field related to lithium-ion battery cathode materials, and discloses a lithium-ion battery cathode material and a preparation method thereof, the method comprising the following steps: (1) using a ternary precursor Ni _x Co _y Mn _{1-x-x y} (OH) ₂ and lithium salt are mixed and roasted as raw materials to obtain the ternary positive electrode material LiNi _x Co _y Mn _1‑x‑y O ₂ , 0.5≤x≤0.8, 0.1≤y≤0.2; the cobalt salt will be dissolved and the methanol solution of zinc salt are poured into the methanol solution of dimethylimidazole and processed to obtain a bimetallic organic framework structure containing cobalt and zinc; (2) the ternary positive electrode material LiNi _x Co _y Mn _1‑x‑y O ₂ is uniformly mixed with the bimetal organic framework structure and then calcined to obtain the positive electrode material of the lithium ion battery, and the positive electrode material of the lithium ion battery is coated with the double metal oxide. The invention has stable structure, good electrical conductivity, and improves the rate performance and cycle performance of the material.

Description

A kind of positive electrode material of lithium ion battery and preparation method thereof

technical field

The invention belongs to the technical field related to lithium-ion battery cathode materials, and more specifically relates to a lithium-ion battery cathode material and a preparation method thereof.

Background technique

In recent years, lithium-ion batteries have been widely used in all aspects of life, from portable electronic devices to electric vehicles and large-scale energy storage systems are inseparable from their existence. Therefore, in order to meet people's requirements for higher energy density, high safety and long life of batteries, how to develop new electrode materials and modify original commercial materials has become a research hotspot. At present, lithium cobalt oxide, lithium iron phosphate, and ternary materials are commonly used as cathode materials for lithium-ion batteries. The ternary materials NCM and NCA are expected to replace lithium cobalt oxide and NCA due to their higher discharge specific capacity and lower cost. Lithium iron phosphate has become the next widely used cathode material for power batteries. However, because of the high content of nickel in high-nickel ternary materials, and the ionic radii of nickel ions and lithium ions are relatively close, the phenomenon of lithium-nickel mixing is prone to occur in the process of material preparation and electrochemical cycling, resulting in The instability of the material structure makes the material break and pulverize. In addition, during the charge-discharge cycle, due to the direct contact between the electrolyte and the electrode material, a series of side reactions occur on the contact surface, resulting in the occurrence of surface phase transition, resulting in a gradual decline in the capacity of the battery.

In order to alleviate the above problems, the conventional approach is to coat the surface of the ternary cathode material. In terms of coating, wet chemical methods such as sol-gel and co-precipitation methods often introduce some impurities into the raw materials and cause some particles to aggregate. and irregular cracks, which affect the integrity of the coating; other methods such as chemical vapor deposition and atomic layer deposition can make the coating dense and continuous, but often the resulting coating is not porous and conductive It is also poor, which hinders the transfer of lithium ions from the cladding layer to the inner active material. Correspondingly, there is a technical demand for developing a lithium-ion battery cathode material with better conductivity and a preparation method thereof in the art.

SUMMARY OF THE INVENTION

Aiming at the above defects or improvement needs of the prior art, the present invention provides a lithium-ion battery positive electrode material and a preparation method thereof. Based on the working characteristics of the existing lithium-ion battery positive electrode materials, a kind of better conductivity is researched and designed. Lithium-ion battery cathode material and preparation method thereof. The coating precursor selected in this preparation method is a bimetallic ZIF containing metal cobalt and metal zinc. ZIF is a crystalline porous material with a periodic network structure formed by self-assembly of transition metal ions and organic ligand organic imidazolate. , and through simple and easy mechanical mixing and heat treatment methods, the amorphous double metal oxide is coated on the ternary positive electrode material, and the coating layer protects the positive electrode material and the electrolyte without inhibiting the transmission of lithium ions. Direct contact keeps the structure stable, so that the material rate and cycle performance after coating modification are greatly improved, and the conductivity is better.

In order to achieve the above object, according to one aspect of the present invention, a kind of preparation method of lithium-ion battery cathode material is provided, and this preparation method comprises the following steps:

(1) Mix and roast the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt as raw materials to obtain the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ , where, 0.5≤ x≤0.8, 0.1≤y≤0.2; at the same time, the methanol solution dissolved with cobalt salt and zinc salt is poured into the methanol solution of dimethylimidazole and treated to obtain a bimetallic organic framework structure containing cobalt and zinc;

(2) mixing the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ with the bimetallic organic framework structure and then calcining to obtain a modified lithium ion battery positive electrode material, the lithium ion battery positive electrode material Coated with double metal oxide.

Further, the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and the lithium salt are mixed according to a predetermined molar ratio, then ball milled, and then fired under a predetermined atmosphere to obtain the ternary positive electrode material LiNi _x Co _y Mn _{1 -xy} O ₂ .

Further, the predetermined molar ratio is 1:1.5˜1:1.

Further, the ball milling time adopted during the ball milling is 0.5h-2h, and the ball milling speed is 200r/min-400r/min.

Further, the calcination temperature adopted during calcination is 700°C-900°C, and the calcination time is 10h-20h.

Further, the concentration ratio of preparation cobalt salt and zinc salt is the methanol solution of (1～5):1, and the methanol solution obtained is poured into the methanol solution of dimethylimidazole whose concentration is 0.2mol/L～0.6mol/L solution, the obtained mixed solution is left to stand for 12h to 24h, and then centrifuged, washed and dried in sequence to obtain a bimetallic organic framework containing metal cobalt and metal zinc.

Further, the ratio of the volume of the methanol solution in which the cobalt salt and the zinc salt are dissolved to the volume of the methanol solution of dimethylimidazole is (0.5-2):1.

Further, the lithium salt is one or more of lithium titanate, lithium hydroxide monohydrate, lithium oxalate, lithium acetate, lithium chloride and lithium sulfate; the cobalt salt is cobalt nitrate, cobalt chloride, One or more of cobalt acetate; the zinc salt is one or more of zinc nitrate, zinc chloride and zinc acetate.

According to another aspect of the present invention, a kind of positive electrode material of lithium ion battery is provided, and this positive electrode material of lithium ion battery is prepared by adopting the preparation method of positive electrode material of lithium ion battery as above; The positive electrode material of lithium ion battery comprises A ternary positive electrode material and a cladding layer, the cladding layer is clad on the ternary positive electrode material; the cladding layer includes uniformly distributed zinc oxide and cobalt oxide.

Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the lithium ion battery positive electrode material and preparation method thereof provided by the present invention mainly have the following beneficial effects:

1. The present invention selects ZIF as the coating precursor. The precursor has the advantages of high porosity, low density, large specific surface area, and regular pores. It can be fully and uniformly mixed with the ternary cathode material, and it can be obtained on the surface after heat treatment in the later stage. Uniform amorphous oxide coating.

2. The preparation method coats the amorphous double metal oxide on the ternary positive electrode material through simple and easy mechanical mixing and heat treatment methods. The coating layer protects the positive electrode material without inhibiting the transmission of lithium ions. Direct contact with the electrolyte maintains structural stability and improves electrical conductivity.

3. The present invention has prepared a bimetallic ZIF containing zinc and cobalt. Zinc oxide and cobalt oxide are both excellent coating layers. The two are combined, and ions are doped with each other, and the obtained oxide coating layer has better conductivity. Well, the rate performance of the battery is even better.

4. The preparation method provided by the present invention is simple and easy to implement, and has good repeatability, and the prepared lithium ion battery positive electrode material has higher reversible specific capacity and better cycle stability.

Description of drawings

Fig. 1 is the schematic flow sheet of the preparation method of lithium ion battery cathode material provided by the present invention;

Fig. 2 is the scanning electron micrograph of the bimetallic ZIF that adopts the preparation method of lithium-ion battery cathode material in Fig. 1 to prepare;

Fig. 3 is the scanning electron micrograph of the sample that adopts the preparation method of lithium-ion battery cathode material in Fig. 1 to prepare;

Fig. 4 is the X-ray diffractogram of the sample of the different components that adopts the preparation method of lithium-ion battery cathode material in Fig. 1 to prepare, and wherein, NCM622/Co-2%, represents to add the ZIF that contains Co, and the quality of ZIF67 is 2% of NCM622; NCM622/Zn-2%, means adding ZIF containing Zn, the mass of ZIF8 is 2% of NCM622; NCM622/Co: Zn=1:5-2%, means adding bimetallic containing Co and Zn The mass of ZIF and BMZIF (Bi-metal Zeolitic Imidazolate Frameworks: BMZIF) is 2% of NCM622, and the molar ratio of Co and Zn is 5:1;

Figure 5 is a rate performance diagram of samples of different components prepared by the preparation method of the lithium ion battery positive electrode material in Figure 1;

Fig. 6 is a cycle performance graph of samples with different components prepared by the method for preparing the positive electrode material of the lithium ion battery in Fig. 1 .

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Please refer to Fig. 1 and Fig. 2, the preparation method of lithium ion battery cathode material provided by the present invention mainly comprises the following steps:

Step 1, mixing and calcining the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt as raw materials to obtain the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ .

Specifically, the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt are mixed according to a predetermined molar ratio, then ball milled, and then fired under a predetermined atmosphere to obtain the ternary cathode material LiNi _x Co _y Mn _{1 -xy} O ₂ . Among them, 0.5≤x≤0.8, 0.1≤y≤0.2.

More specifically, Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt are added to the ball mill at a molar ratio of 1:1.5 to 1:1 for ball milling for 0.5h to 2h, and the speed of the ball mill is 200r/min to 400r /min. After ball milling, put the obtained product into a muffle furnace and sinter at 700°C to 900°C for 10h to 20h to obtain the _ternary cathode material _{LiNixCoyMn1 -xyO2 .}

In this embodiment, the lithium salt may be one or more of lithium titanate, lithium hydroxide monohydrate, lithium oxalate, lithium acetate, lithium chloride and lithium sulfate.

In step 2, the methanol solution in which the cobalt salt and the zinc salt are dissolved is poured into a methanol solution of dimethylimidazole and treated to obtain a bimetallic organic framework structure containing cobalt and zinc.

Specifically, prepare a methanol solution with a concentration ratio of cobalt salt and zinc salt of (1-5):1, and pour the resulting methanol solution into methanol with a concentration of 0.2mol/L-0.6mol/L dimethylimidazole Solution, the obtained mixed solution is left to stand for 12h to 24h, and then centrifuged, washed and dried in sequence to obtain a bimetallic ZIF (BMZIF) containing metal cobalt and metal zinc, wherein ZIF is a zeolite imidazolate framework material.

In this embodiment, the ratio of the volume of the methanol solution with cobalt salt and zinc salt to the volume of the methanol solution of dimethylimidazole is (0.5-2): 1; the cobalt salt is cobalt nitrate, cobalt chloride, One or more of cobalt acetate; the zinc salt is one or more of zinc nitrate, zinc chloride and zinc acetate. Of course, step 1 and step 2 are in no particular order, and the two can be carried out at the same time.

Step 3, mixing the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ with the bimetallic organic framework structure and then calcining to obtain a modified lithium ion battery positive electrode material, the lithium ion battery positive electrode material Coated with double metal oxide.

Specifically, the obtained ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ and the obtained BMZIF are fully mixed according to the mass ratio of 100: (1-5), and then placed in a predetermined atmosphere for sintering for 0.5h-2h, In order to obtain a lithium-ion battery ternary cathode material coated with a double metal oxide. In this embodiment, the calcination temperature used is 500° C. to 700° C.; the mixing method used is one of ball milling, grinding and wet mixing.

Please refer to Fig. 3, Fig. 4, Fig. 5 and Fig. 6, the present invention also provides a kind of positive electrode material of lithium ion battery, and this positive electrode material of lithium ion battery comprises ternary positive electrode material and coating layer, and described coating layer coats on the ternary cathode material. The diameter of the ternary positive electrode material is 5 μm-10 μm; the coating layer includes uniformly distributed zinc oxide and cobalt oxide, and its thickness is 10 nm-30 nm.

The present invention will be further described in detail with several specific examples below.

Example 1

The preparation method of the lithium-ion battery cathode material provided by Example 1 of the present invention mainly includes the following steps:

S1, add Ni ₆ Co ₂ Mn ₂ (OH) ₂ and lithium salt into the ball mill at a molar ratio of 1:1, the ball milling time is 1h, the ball mill speed is 300r/min, after the ball milling is completed, the obtained product is put into the muffle Sintering in a furnace at 900°C for 10h to obtain a ternary cathode material;

S2, configure the concentration of zinc nitrate and cobalt nitrate to be 50ml of methanol solution of 0.05mol/L and 0.01mol/L respectively, and pour 50ml of methanol solution of dimethylimidazole with a concentration of 0.2mol/L to obtain the mixed After standing for 24 hours, the bimetallic ZIF (BMZIF) containing metal cobalt and zinc was obtained by centrifugation, washing and drying.

In S3, the obtained ternary cathode material and the obtained BMZIF powder are fully mixed at a mass ratio of 100:1, and then placed in a predetermined atmosphere for sintering for 1 h, to obtain a lithium-ion ternary cathode material coated with a double metal oxide.

Example 2

The preparation method of the lithium-ion battery positive electrode material provided by Example 2 of the present invention mainly includes the following steps:

S1, add Ni ₆ Co ₂ Mn ₂ (OH) ₂ and lithium salt into the ball mill at a molar ratio of 1:1.3, the ball milling time is 1h, the ball mill speed is 300r/min, after the ball milling is completed, the obtained product is put into the muffle Sintering in a furnace at 800°C for 15 hours to obtain a ternary cathode material;

S2, configure the concentration of zinc nitrate and cobalt nitrate to be 25ml of methanol solution of 0.04mol/L and 0.04mol/L respectively, and pour 50ml of methanol solution of dimethylimidazole with a concentration of 0.2mol/L to obtain the mixed After standing for 24 hours, the bimetallic ZIF (BMZIF) containing metal cobalt and zinc was obtained by centrifugation, washing and drying.

In S3, the obtained ternary cathode material and the obtained BMZIF powder are fully mixed at a mass ratio of 60:1, and then placed in a predetermined atmosphere for sintering for 1.5 hours, to obtain a lithium-ion ternary cathode material coated with a double metal oxide. In this step, the sintering temperature used is 700°C.

Example 3

The preparation method of the positive electrode material of lithium ion battery provided by the embodiment of the present invention 3 mainly comprises the following steps:

S1, Ni ₆ Co ₂ Mn ₂ (OH) ₂ and lithium salt are added into the ball mill at a molar ratio of 1:1.5, the ball milling time is 0.5h, and the ball mill speed is 400r/min. After the ball milling is completed, the obtained product is put into the Sintering at 700°C for 20h in a Furnace to obtain a ternary cathode material;

S2, configure the concentration of zinc nitrate and cobalt nitrate to be 50ml of methanol solution of 0.04mol/L and 0.04mol/L respectively, and pour 100ml of methanol solution of dimethylimidazole with a concentration of 0.4mol/L to obtain the mixture After standing for 12 hours, the bimetallic ZIF (BMZIF) containing metal cobalt and zinc was obtained by centrifugation, washing and drying.

In S3, the obtained ternary cathode material and the obtained BMZIF powder are fully mixed at a mass ratio of 20:1, and then placed in a predetermined atmosphere for sintering for 0.5h to obtain a lithium-ion ternary cathode material coated with a double metal oxide. In this step, the sintering temperature used is 600°C.

Example 4

The preparation method of the positive electrode material of lithium ion battery provided by the embodiment of the present invention 4 mainly comprises the following steps:

S1, Ni ₆ Co ₂ Mn ₂ (OH) ₂ and lithium salt are added into the ball mill at a molar ratio of 1:1.1, the ball milling time is 1.5h, the ball mill speed is 300r/min, and the obtained product is put into the mill after the ball milling is completed. Sintering at 850°C for 12h in a Furnace to obtain a ternary cathode material;

S2, configure the concentration of zinc nitrate and cobalt nitrate to be 100ml of methanol solution of 0.03mol/L and 0.01mol/L respectively, and pour 50ml of methanol solution of dimethylimidazole with a concentration of 0.6mol/L to obtain the mixed solution After standing for 24 hours, bimetallic ZIF (BMZIF) containing metal cobalt and zinc was obtained by centrifugation, washing and drying.

In S3, the obtained ternary cathode material and the obtained BMZIF powder are fully mixed at a mass ratio of 100:2, and then placed in a predetermined atmosphere for sintering for 1.5 hours to obtain a lithium-ion ternary cathode material coated with a double metal oxide.

Example 5

The preparation method of the positive electrode material of lithium ion battery provided by the embodiment of the present invention 5 mainly comprises the following steps:

S1, add Ni ₆ Co ₂ Mn ₂ (OH) ₂ and lithium salt into the ball mill at a molar ratio of 1:1.1, the ball milling time is 2h, the ball mill speed is 200r/min, after the ball milling is completed, the obtained product is put into the muffle Sintering in a furnace at 850°C for 12 hours to obtain a ternary cathode material;

S2, configure the concentration of zinc nitrate and cobalt nitrate to be 50ml of methanol solution of 0.05mol/L and 0.01mol/L respectively, and pour 50ml of methanol solution of dimethylimidazole with a concentration of 0.5mol/L to obtain the mixed After standing for 24 hours, the bimetallic ZIF (BMZIF) containing metal cobalt and zinc was obtained by centrifugation, washing and drying.

In S3, the obtained ternary cathode material and the obtained BMZIF powder are fully mixed at a mass ratio of 100:2, and then placed in a predetermined atmosphere for sintering for 2 hours to obtain a lithium-ion ternary cathode material coated with a double metal oxide. In this step, the sintering temperature used is 500°C.

The lithium ion battery positive electrode material and its preparation method provided by the present invention, the preparation method is simple and easy mechanical mixing and heat treatment method, the amorphous double metal oxide is coated on the ternary positive electrode material, the coating layer is not Under the premise of inhibiting the transmission of lithium ions, the direct contact between the positive electrode material and the electrolyte is protected, the structure is maintained stable, and the electrical conductivity is improved.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. a preparation method of lithium ion battery positive electrode material, is characterized in that, this preparation method comprises the following steps: (1) Mix and roast the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt as raw materials to obtain the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ , where, 0.5≤ x≤0.8, 0.1≤y≤0.2; at the same time, the methanol solution dissolved with cobalt salt and zinc salt is poured into the methanol solution of dimethylimidazole and treated to obtain a bimetallic organic framework structure containing cobalt and zinc; (2) mixing the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ with the bimetallic organic framework structure and then calcining to obtain a modified lithium ion battery positive electrode material, the lithium ion battery positive electrode material Coated with double metal oxide. 2. the preparation method of lithium ion battery cathode material as claimed in claim 1 is characterized in that: the ternary precursor Ni _x Co _y Mn _1-xy (OH) ₂ and lithium salt carry out ball milling after mixing according to predetermined molar ratio , followed by firing under a predetermined atmosphere to obtain the ternary cathode material _LiNix Co _y Mn _1-xy O ₂ . 3. The method for preparing the positive electrode material of lithium ion battery according to claim 2, characterized in that: the predetermined molar ratio is 1:1.5˜1:1. 4 . The preparation method of lithium ion battery positive electrode material as claimed in claim 2 , characterized in that: the ball milling time adopted during ball milling is 0.5h-2h, and the ball milling speed is 200r/min-400r/min. 5 . The method for preparing the positive electrode material of lithium ion battery according to claim 2 , characterized in that: the calcination temperature used during calcination is 700° C. to 900° C., and the calcination time is 10h to 20h. 6 . 6. the preparation method of lithium-ion battery cathode material as claimed in claim 1 is characterized in that: the concentration ratio of preparation cobalt salt and zinc salt is (1～5): the methanol solution of 1, and the methanol solution obtained is poured Add a methanol solution of dimethylimidazole with a concentration of 0.2mol/L to 0.6mol/L, let the obtained mixed solution stand for 12h to 24h, then perform centrifugation, washing and drying in sequence to obtain a bismuth containing metal cobalt and metal zinc. Metal Organic Frameworks. 7. the preparation method of lithium ion battery cathode material as claimed in claim 6 is characterized in that: the ratio of the volume of the methanol solution that is dissolved with cobalt salt and zinc salt and the volume of the methanol solution of dimethylimidazole is (0.5～ 2): 1. 8. The preparation method of lithium ion battery cathode material as claimed in claim 6, is characterized in that: described lithium salt is lithium titanate, lithium hydroxide monohydrate, lithium oxalate, lithium acetate, lithium chloride and lithium sulfate one or more of them; the cobalt salt is one or more of cobalt nitrate, cobalt chloride and cobalt acetate; the zinc salt is one or more of zinc nitrate, zinc chloride and zinc acetate . 9. The preparation method of the positive electrode material of lithium ion battery as claimed in any one of claims 1-8, characterized in that: the ternary positive electrode material LiNi _x Co _y Mn _1-xy O ₂ and the double metal organic framework structure Mix according to the mass ratio of 100:(1-5), put them into a predetermined atmosphere and sinter for 0.5h-2h, so as to obtain a lithium-ion battery cathode material coated with double metal oxides. 10. A lithium-ion battery cathode material, characterized in that: the lithium-ion battery cathode material is prepared by the preparation method of the lithium-ion battery cathode material according to any one of claims 1-9; the lithium-ion battery The positive electrode material includes a ternary positive electrode material and a coating layer, and the coating layer is coated on the ternary positive electrode material; the coating layer includes uniformly distributed zinc oxide and cobalt oxide.