High-voltage stable AlO4 zeolite coating modified NCM622 positive electrode material and preparation method thereof

Abstract

The invention relates to the technical field of battery electrode materials, in particular to a high-voltage stable type AlO4 zeolite coating modified NCM622 positive electrode material and a preparation method thereof, and the positive electrode material comprises NCM622 coated AlPO4 formed by wrapping NCM622 with AlPO4, a conductive agent and a binder; the preparation method of the NCM622-coated AlPO4 comprises the following steps: mixing and stirring NCM622, AlOOH, phosphoric acid and triethylamine in deionized water; removing the solvent by using a vacuum pump and then collecting powder; and annealing and the like. Compared with the prior art, the high-voltage stable AlO4 zeolite coating modified NCM622 positive electrode material and the preparation method disclosed by the invention have the advantage that the stability of the positive electrode material can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrode materials, and in particular to a high-voltage stable AlO4 zeolite coating modified NCM622 positive electrode material and a preparation method thereof. Background Art

[0002] In recent years, lithium-ion batteries, especially those using NCM622 as the positive electrode, have shown great market potential and application value in the fields of electric vehicles, energy storage systems and portable electronic devices. While lithium-ion batteries have many advantages, they also have many disadvantages, specifically: (1) Under high-voltage operating conditions, the structural stability of NCM622 materials becomes a key factor restricting their performance. Although high-voltage operation can significantly improve the energy density of the battery and meet the needs of electric vehicles and energy storage systems for high energy output, it also increases the risk of phase change and structural collapse of the material. This structural instability will lead to a decrease in battery cycle stability and affect the battery's service life and safety. (2) The interface reaction between NCM622 materials and electrolytes is also a problem that needs to be solved urgently. The interface reaction not only leads to the loss of active substances, reduces the capacity and energy density of the battery, but also generates an interface layer that is not conducive to lithium ion transmission. These interface layers will hinder the diffusion and migration of lithium ions, further affecting the performance and cycle stability of the battery.

[0003] To solve the above problems, common strategies include: (1) improving the charge cut-off voltage through material modification and electrolyte optimization; (2) increasing the interface stability through surface passivation treatment, improving the electrode structure, or using a new type of diaphragm.

[0004] The above-mentioned solutions have their own advantages and disadvantages. Among them, material modification through surface coating technology is one of the commonly used technical means. Surface coating technology forms a protective layer by covering the surface of the main electrode material with a layer of stable oxide or fluoride or other materials. This protective layer can effectively reduce the direct contact between the active material and the electrolyte under high voltage, thereby reducing the occurrence of interfacial side reactions and improving the cycle stability and safety of the material. In addition, the coating layer can also inhibit the growth of lithium dendrites to a certain extent and reduce the risk of battery short circuit. Although surface coating technology has many advantages, the uniformity and density of the coating layer are difficult to control. If the coating layer is uneven or defective, it may cause the electrolyte to penetrate into the material and trigger interfacial side reactions. In addition, the coating layer may also affect the diffusion rate of lithium ions, thereby affecting the charge and discharge performance of the battery.

[0005] Therefore, how to prepare a uniform, dense coating that does not affect the diffusion of lithium ions is one of the difficulties in current research. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, a high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material and a preparation method thereof are provided.

[0007] A high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material, comprising:

[0008] NCM622, NCM622 is LiNi 0.6 Co 0.2 Mn 0.2 O2;

[0009] AlPO4, AlPO4 is coated on the outer surface of NCM622 material in the form of zeolite coating. The name of NCM622 material coated with AlPO4 is defined as NCM622@AlPO4;

[0010] Conductive agent;

[0011] Binder;

[0012] The mass percentage of NCM622 and AlPO4 in the positive electrode material is defined as x%, where 90≤x≤96.

[0013] Furthermore, the conductive agent includes Super P and CNT, the mass percentage of Super P in the positive electrode material is defined as y%, the mass percentage of CNT in the positive electrode material is defined as z%, wherein x+y=97.5, z=0.5.

[0014] Furthermore, the binder is PVDF, and the mass percentage of the binder to the positive electrode material is defined as w%, wherein w=2.

[0015] A method for preparing NCM622@AlPO4 material comprises the following steps:

[0016] (S1) Material premixing: NCM622, AlOOH, phosphoric acid and triethylamine were mixed in deionized water.

[0017] (S2) Precursor preparation: stirring the above mixture under hydrothermal conditions;

[0018] (S3) collecting powder: removing the solvent from the solution obtained in step (S2) using a vacuum pump, and collecting the powder after filtration;

[0019] (S4) placing the powder obtained in step (S3) in a tube furnace and annealing it at high temperature under an argon atmosphere, and collecting the annealed material.

[0020] Furthermore, in step (S1), the mass ratio of NCM622, AlOOH, phosphoric acid and triethylamine is 2:1:2:2.

[0021] Furthermore, in step (S1), the mass concentrations of NCM622, AlOOH, phosphoric acid and triethylamine are 1 / 15%, 1 / 30%, 1 / 15% and 1 / 15% respectively.

[0022] The high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material and preparation method disclosed in the present invention have the following technical effects:

[0023] (1) Significantly improve the stability of the positive electrode material structure. By introducing the AlPO4 zeolite coating, the present invention successfully enhances the structural stability of the NCM622 positive electrode material. Figure 2 As shown in the figure, the uniform coverage of the AlPO4 zeolite coating on the surface of the positive electrode material effectively isolates the direct contact between the active material and the electrolyte, reduces the occurrence of harmful side reactions under high voltage conditions, thereby extending the cycle life of the battery, and improving the structural integrity of the positive electrode material during the charge and discharge process, providing a solid foundation for the preparation of high-performance lithium-ion batteries.

[0024] (2) Optimized lithium ion transmission path and efficiency. As a high-performance ion conductor, the AlPO4 zeolite coating significantly optimizes the lithium ion transmission path; the zeolite structure in the AlPO4 zeolite coating provides more transmission channels for lithium ions, reducing the energy loss during ion transmission. This improvement not only improves the battery's charge and discharge efficiency, but also enables the battery to maintain higher energy density and power output under high voltage operating conditions.

[0025] (3) Enhance battery cycle stability and safety. The modified AlPO4 zeolite coating effectively reduces the interfacial side reactions between the electrolyte and the positive electrode material. The coating builds a stable protective barrier at the electrode interface, inhibits the decomposition of the electrolyte and the occurrence of harmful reactions, reduces the formation of lithium dendrites, and thus avoids the occurrence of internal short circuits and safety hazards in the battery. This improvement significantly improves the cycle stability and safety of the battery, providing a strong guarantee for the widespread application of lithium-ion batteries.

[0026] (4) Improved overall battery performance. By comprehensively optimizing the surface properties of the positive electrode material, the present invention significantly improves the overall performance of the lithium-ion battery. Key indicators such as the battery's cycle life, energy density, charge and discharge efficiency, and safety have all been significantly improved. This improvement not only meets the development trend of high-performance, high-energy-density lithium-ion batteries, but also provides a more reliable and efficient battery technology solution for electric vehicles, large-scale energy storage systems, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the SEM image of NCM622;

[0028] Figure 2 This is a partial SEM enlarged image of NCM622;

[0029] Figure 3 This is a partial SEM enlarged image of NCM622@AlPO4;

[0030] Figure 4 Capacity-voltage curves of NCM622 / Li and NCM622@AlPO4 / Li during the first charging process;

[0031] Figure 5 This is the rate performance diagram of NCM622 / Gr and NCM622@AlPO4 / Gr;

[0032] Figure 6 This is the long cycle performance diagram of NCM622 / Li and NCM622@AlPO4 / Gr. DETAILED DESCRIPTION

[0033] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] A high-voltage stable AlO4 zeolite coating modified NCM622 positive electrode material comprises NCM622, AlPO4, a conductive agent and a binder, wherein: AlPO4 is coated on the outer surface of the NCM622 material in the form of a zeolite coating, and the material name of the NCM622 coated with AlPO4 is defined as NCM622@AlPO4; the conductive agent comprises Super P and CNT, i.e., conductive carbon black and carbon nanotubes; and the binder is PVDF.

[0035] Define the mass percentage of NCM622 and AlPO4 in the positive electrode material as x%, define the mass percentage of Super P in the positive electrode material as y%, define the mass percentage of CNT in the positive electrode material as z%, and define the mass percentage of the binder in the positive electrode material as w%, wherein x+y=97.5, z=0.5, and w=2.

[0036] A method for preparing NCM622@AlPO4 material comprises the following steps:

[0037] (S1) Material premixing: NCM622, AlOOH, phosphoric acid, and triethylamine are mixed in deionized water, wherein the mass ratio of NCM622, AlOOH, phosphoric acid, and triethylamine is 2:1:2:2. In this embodiment, the deionized water is 1.5 L, and the mass concentrations of NCM622, AlOOH, phosphoric acid, and triethylamine are 1 / 15%, 1 / 30%, 1 / 15%, and 1 / 15%, respectively, that is, the mass of NCM622 is 100 g, AlOOH is 50 g, phosphoric acid is 100 g, triethyl is 100 g, and amine is 100 g.

[0038] (S2) Precursor preparation: The above mixture is stirred under hydrothermal conditions, wherein the water temperature is 155° C. and the stirring speed is 2000 r / min.

[0039] (S3) Collecting powder: using a vacuum filter pump to remove the solvent and collect the filtered powder.

[0040] (S4) placing the powder in a tube furnace and annealing it at 550° C. for 2 h in an argon atmosphere.

[0041] (S5) Collect the annealed material to obtain NCM622@AlPO4 material.

[0042] The SEM images of NCM622 and NCM622@AlPO4 were obtained by scanning electron microscopy. The SEM partial magnified images of NCM622 and NCM622@AlPO4 are shown in the attached figure. Figure 2 and attached Figure 3 As shown: It can be seen that the surface of NCM622 particles is relatively smooth, and AlPO4 particles are evenly distributed on the surface of NCM622@AlPO4 material particles, which provides a basis for improving the performance of NCM622@AlPO4 under high pressure.

[0043] In order to verify the superiority of this product, NCM622@AlPO4 is used as the main material of the positive electrode (all positive electrode materials and their contents are shown in Table 1 below) and graphite (Gr) is used as the negative electrode material as an example; NCM622 is used as the main material of the positive electrode (all positive electrode materials and their contents are shown in Table 2 below) and graphite (Gr) is used as the negative electrode material as a comparative example. The negative electrode materials and their contents in the examples and comparative examples are shown in Table 3 below.

[0044] Table 1 Positive electrode materials and contents in various embodiments (unit: kg)

[0045]

[0046]

[0047] Table 2 Positive electrode materials and contents in comparative examples (unit: kg)

[0048]

[0049] Table 3 Negative electrode materials and contents in the examples and comparative examples (unit: kg)

[0050] Graphite (Gr) SuperP CMC SBR 2.865 0.045 0.039 0.051

[0051] According to the following preparation method, the positive and negative electrode materials in the corresponding embodiments and comparative examples are made into corresponding battery soft packs.

[0052] (A1) Preparation of electrolyte: Prepare 1000 mL of a mixed solvent of EC / EMC / DMC (1:1:1 vol%), weigh 151.905 g of LiPF6, 30 mL of VC and 10 mL of FEC and add them to the mixed solvent.

[0053] (A2) Soft-pack battery injection: Add electrolyte to the finished soft-pack battery (NCM622 / Gr and NCM622@AlPO4 / Gr) with an injection coefficient of 3.5 g / Ah.

[0054] (A3) High temperature soaking: After the injection, place the soft pack battery at 45°C for 24 hours to ensure that the electrolyte fully soaks the battery cell.

[0055] (A4) Formation: The corresponding example and comparative example batteries were placed at 25° C. for formation. The formation process was as follows: the battery was charged to 4.9 V using a constant current of 0.05 C.

[0056] (A5) Secondary packaging: Release the gas in the soft-pack battery after formation and perform secondary packaging on the side.

[0057] (A6) Aging: The soft-pack battery was placed at 45°C for 48 hours for high temperature aging.

[0058] The prepared example battery and comparative example battery were subjected to a cycle experiment: the comparative example soft-pack battery and example soft-pack battery were placed at 25°C for a long cycle test, the test voltage range was 2.5-4.9V, and the cycle rate was 0.5C.

[0059] Figure 4 The capacity-voltage curves of the battery soft pack corresponding to the positive electrode material NCM622 and the battery soft pack corresponding to the positive electrode material NCM622@AlPO4 during the first charging process are shown. It can be clearly seen that the soft pack battery corresponding to the positive electrode material NCM622@AlPO4 can use a higher charge specific capacity at a high voltage of 4.9V, and the curve shape is better, which means that the material has better stability in the charging and discharging process at a high cut-off voltage.

[0060] Figure 5 The rate performance diagram of the battery soft pack with the positive electrode material NCM622 and the battery soft pack with the positive electrode material NCM622@AlPO4 is shown. It can be clearly seen that in the same charge and discharge range (2.5-4.9V), the battery soft pack with the positive electrode material NCM622@AlPO4 can maintain a higher capacity and better rate performance.

[0061] Figure 6The long cycle performance diagrams of the battery soft pack with NCM622 as the positive electrode material and the battery soft pack with NCM622@AlPO4 as the positive electrode material are shown. In the same charge and discharge range (2.5-4.9V), the battery soft pack with NCM622@AlPO4 as the positive electrode material has a higher discharge specific capacity, and the long cycle stability has been qualitatively improved, which means that the surface AlPO4 coating can effectively stabilize the structural stability of NCM622 under high voltage.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material, characterized in that: include: NCM622, NCM622 is LiNi 0.6 Co 0.2 Mn 0.2 O2; AlPO4, AlPO4 is coated on the outer surface of NCM622 material in the form of zeolite coating. The material name of NCM622 coated with AlPO4 is defined as NCM622@AlPO4; Conductive agent; Binder; The mass percentage of NCM622 and AlPO4 in the positive electrode material is defined as x%, where 90≤x≤96.

2. The high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material according to claim 1, characterized in that: The conductive agent includes Super P and CNT, and the mass percentage of Super P in the positive electrode material is defined as y%, and the mass percentage of CNT in the positive electrode material is defined as z%, wherein x+y=97.5, z=0.

5.

3. The high voltage stable AlO4 zeolite coating modified NCM622 positive electrode material according to claim 1, characterized in that: The binder is PVDF, and the mass percentage of the binder to the positive electrode material is defined as w%, wherein w=2.

4. A method for preparing NCM622@AlPO4 material, characterized in that: The following steps are involved: (S1) Material premixing: NCM622, AlOOH, phosphoric acid and triethylamine were mixed in deionized water. (S2) Precursor preparation: stirring the above mixture under hydrothermal conditions; (S3) collecting powder: removing the solvent from the solution obtained in step (S2) using a vacuum pump, and collecting the powder after filtration; (S4) placing the powder obtained in step (S3) in a tube furnace and annealing it at high temperature under an argon atmosphere, and collecting the annealed material.

5. The method for preparing the NCM622@AlPO4 material according to claim 4, characterized in that: In step (S1), the mass ratio of NCM622, AlOOH, phosphoric acid and triethylamine is 2:1:2:

2.

6. The method for preparing the MCN622@AlPO4 material according to claim 5, characterized in that: In step (S1), the mass concentrations of NCM622, AlOOH, phosphoric acid and triethylamine are 1 / 15%, 1 / 30%, 1 / 15% and 1 / 15% respectively.

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