Layered oxide material with nano woven net interface structure as well as preparation method and application of layered oxide material

Abstract

The invention provides a layered oxide material with a nanometer woven net interface structure and a preparation method and application thereof, and belongs to the field of electrode materials, a dilute acid solution is used as a reaction medium, and a spray pyrolysis mode is combined to enable dilute acid to fully react with a residual alkali compound on the surface of layered oxide, so that the layered oxide material is obtained. And synchronously converting into a uniform nano woven net interface structure in situ. A uniform nano interface structure can be prepared, belongs to a flexible film structure and has a relatively strong bonding effect, and the interface structure can persistently and stably exist in a charging and discharging process, so that the structural strain is reduced; the nano woven net interface structure has a relatively large specific surface area, so that the contact area and the liquid retention amount of the layered oxide material and an electrolyte are increased, and the diffusion of Li < + > and the migration of electrons are accelerated; the uniform knitted net interface structure can inhibit the surface oxidation of the material and the reaction with water and carbon dioxide in the air, improve the air tolerance of the matrix material, and also can greatly inhibit the erosion effect of the electrolyte on the matrix material.

Description

Layered oxide materials with nanowoven interface structure, their preparation methods and applications Technical Field

[0001] This invention relates to the field of electrode materials, and more particularly to layered oxide materials with nanowoven interface structures, their preparation methods, and applications. Background Technology

[0002] The surge in battery production has spurred the diversification of battery chemistry to ensure the resilience of the battery supply chain. In battery components, the cathode material determines both cost and performance. While lithium iron phosphate (LiFePO4) remains the mainstream cathode material for power batteries, layered oxide materials are still considered ideal. For layered oxide materials, the redox reaction of nickel or oxygen contributes the majority of the capacity. As the charging cutoff voltage increases, the capacity provided by layered oxide materials also increases, resulting in higher energy density. However, while providing high capacity, layered oxide materials also compromise durability; the resulting limited battery life is a major challenge for their commercial application.

[0003] Studies have shown that the performance degradation mechanisms of layered oxide materials mainly include irreversible phase transitions, oxygen evolution, and transition metal dissolution. These degradation mechanisms are all related to unfavorable interfacial reactions between the electrode and electrolyte under high voltage. At higher cutoff voltages, layered oxide materials release more Li+ ions, leading to greater structural instability. The surface phase of the layered oxide material after Li-removal spontaneously transforms into a rock salt phase. First, the rock salt phase hinders Li+ diffusion. Second, unstable Ni4+ spontaneously transforms into stable Ni2+, resulting in capacity and lattice oxygen loss. Finally, both Ni4+ and reactive oxygen species can cause oxidative decomposition of the electrolyte solvent, leading to interfacial side reactions, electrolyte depletion, gas generation, and increased battery impedance. Furthermore, the anisotropic expansion and contraction of the cell during cycling generates microcracks. The electrolyte gradually penetrates into these microcracks and reacts with the layered oxide material. An inert rock salt phase forms on the crack surface, adding an additional barrier to Li+ diffusion and causing capacity loss.

[0004] Based on the above discussion, the unstable interface between highly deLi-degraded layered oxides and the electrolyte is the main factor leading to irreversible phase transitions, resulting in capacity decay and increased impedance. To address the interface problem, coatings and surface modification have proven to be effective methods for stabilizing the cathode / electrolyte interface, mitigating the formation of defect layers and space charge layers to some extent. To date, carbon-based materials, metal oxides, metal fluorides, metal phosphates, and fast ion conductors have been applied to coatings and have been shown to effectively suppress interfacial side reactions and improve the electrochemical performance of layered oxide materials. Typically, coating materials grow on the surface of cathode particles and, after high-temperature calcination, are in a crystalline state, compatible with the cathode. However, coatings are prone to brittle fracture during long-term cycling, leading to continuous electrolyte decomposition and low coulombic efficiency. Therefore, traditional coating structures cannot perfectly stabilize the interface. In conclusion, there is a need to develop a universally applicable special interface structure to solve the interfacial stability problem of layered oxide materials, thereby leveraging their inherent advantages. Summary of the Invention

[0005] The purpose of this invention is to provide layered oxide materials with nano-woven interface structures, their preparation methods, and applications, thereby solving the technical problem that existing layered oxide materials in batteries have poor interface stability and cannot fully utilize the inherent advantages of layered oxide materials.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] Layered oxide materials with a nanowoven interface structure, wherein the layered oxide materials comprise nickel-rich and lithium-rich materials, and have the general structural formula Li x TM y O2@Li u NM v O w Wherein, 1.0≤x≤1.2, 0.8≤y≤1.0, 0≤u≤15, 1≤x≤15, 1≤w≤15, TM is one or more of nickel, cobalt, manganese and aluminum, and NM is one of boron, phosphorus, sulfur and selenium.

[0008] A method for preparing a layered oxide material with a nanowoven interface structure, the method comprising the following steps:

[0009] Step 1: Add a certain amount of layered oxide material and dilute acid solution to a stirred reactor and stir for a certain time to obtain a suspension;

[0010] Step 2: Transfer the suspension to the spray dryer using a peristaltic pump, set a certain feeding rate, inlet air temperature, and outlet air temperature, and collect the dried precursor material at the outlet;

[0011] Step 3: Transfer the dried precursor material to a vacuum furnace, set a certain calcination temperature and time, and after calcination, a layered oxide material with a nano-woven interface structure can be obtained.

[0012] Furthermore, in step 1, the layered oxide material is one or more of the following: lithium-rich manganese-based materials, nickel-rich cathode materials, nickel-rich multi-element materials, and salt rock disordered materials.

[0013] Further, in step 1, the dilute acid is one or more of boric acid and phosphoric acid, the mass ratio of the solid dilute acid to the layered oxide material is 1:100-3:100; the solid-liquid ratio of the layered oxide material to the dilute acid is 0.1-1.0 g / ml; and the ultrasonic stirring time is 30 min-120 min.

[0014] Furthermore, in step 2, the feeding rate is 1-6 L / min, and the inlet air temperature is 200 °C. o C, outlet air temperature is 100 o C.

[0015] Furthermore, the calcination temperature is 300-600℃. o C, calcination time is 2-6 hours, and the calcination atmosphere is air.

[0016] Application of layered oxide materials with nano-woven interface structure, wherein the layered oxide materials are used as positive electrode active materials for batteries.

[0017] Furthermore, the battery preparation process of applying the layered oxide material to the positive electrode active material is as follows: the layered oxide material is used as the positive electrode active material, PVDF is used as a binder, SP and KS-6 are used as conductive agents, and NMP is used as a solvent. The mixture is stirred and mixed to a uniform slurry state according to the mass ratio of active material: binder: conductive agent of 85:5:10. The prepared positive electrode slurry is uniformly coated on aluminum foil using a preparation device, and then transferred to a vacuum drying oven at 120°C for vacuum drying for 12 hours. The thickness to be achieved by rolling the electrode sheet is calculated according to the compaction density, and the rolling process is performed. The rolled electrode sheet is cut into uniformly thick electrode sheets with a diameter of 12mm using a cutting machine, and assembled into a button battery in a vacuum glove box. Lithium sheet is used as the counter electrode, and LiFP6-based electrolyte is used.

[0018] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0019] (1) This invention utilizes the inherent disadvantage of residual alkali compounds on the surface of layered oxide materials, combined with processes such as ultrasonic atomization, to transform them in situ into a nano-woven interface structure. The nano-woven interface structure is a flexible material, and the interface structure and the matrix structure have strong bonding and interaction, achieving 100% surface coverage. This method is simple, low-cost, and has universal applicability;

[0020] (2) A uniform nano-interface structure can be prepared. It is a flexible film structure with strong bonding effect. The interface structure can exist stably and permanently during charging and discharging, reducing structural strain. The nano-woven interface structure has a large specific surface area, which increases the contact area between the layered oxide material and the electrolyte and the liquid retention, accelerates the diffusion of Li+ and the migration of electrons. The uniform woven interface structure can inhibit the oxidation of the material surface and the reaction with water and carbon dioxide in the air, improve the air tolerance of the matrix material, and also greatly inhibit the erosion effect of the electrolyte on the matrix material. Attached Figure Description

[0021] Figure 1 is a SEM image of Embodiment 1 of the present invention;

[0022] Figure 2 is a SEM image of Comparative Example 1 of the present invention;

[0023] Figure 3 is a SEM cross-sectional view of Embodiment 1 of the present invention;

[0024] Figure 4 is an EDS cross-sectional view (P element) of Embodiment 1 of the present invention;

[0025] Figure 5 is a comparison of the discharge specific capacity of Example 1 and Comparative Example 1 for the first 200 cycles (2.0-4.8V, 1C). Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0027] A method for preparing a layered oxide material with a nanowoven interface structure, the method comprising the following steps:

[0028] Step S1: Add 10g of lithium-rich manganese-based cathode material (Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Add O2, 0.2g of phosphoric acid (H3PO4) and 100ml of deionized water to the ultrasonic device and sonicate for 30 minutes;

[0029] Step S2: The above suspension is continuously fed into the spray drying equipment using a peristaltic pump. The preset feeding rate is 200 ml / h, and the inlet air temperature is 200 °C. o C, outlet air temperature is 100 o C, to prepare the precursor;

[0030] Step S3: Transfer the above-mentioned precursor to a vacuum furnace and set the calcination temperature to 400°C. o C, calcination time of 2 h, to prepare lithium-rich manganese-based cathode material (Li) with nano-woven interface structure. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2@2%Li3PO4);

[0031] Comparative Example 1 is the original lithium-rich manganese-based cathode material (Li). 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2);

[0032] Example 2

[0033] Step S1: Add 10g of nickel-rich ternary cathode material (LiNi) 0.8 Co 0.1 Mn 0.1 Add O2), 0.3g boric acid (H3BO3) and 100ml deionized water to the ultrasonic device and sonicate for 30 minutes;

[0034] Step S2: The above suspension is continuously fed into the spray drying equipment using a peristaltic pump. The preset feeding rate is 200 ml / h, and the inlet air temperature is 200 °C. o C, outlet air temperature is 100 o C, to prepare the precursor;

[0035] Step S3: Transfer the above precursor to a vacuum furnace, set the calcination temperature to 400°C, and the calcination time to 2 hours to prepare a lithium-rich manganese-based cathode material (LiNi) with a nano-woven interface structure. 0.8 Co 0.1 Mn 0.1 O2@3%Li3BO3);

[0036] Comparative Example 2 is the original nickel-rich ternary cathode material (LiNi). 0.8 Co 0.1 Mn 0.1 O2);

[0037] Performance testing

[0038] All tests in this experiment were conducted using a 2025 model coin cell as a benchmark. First, the prepared composite material was used as the positive electrode active material, PVDF (model 5130) as the binder, SP and KS-6 as conductive agents, and NMP as the solvent. The materials were mixed in a mass ratio of active material: binder: conductive agent of 85:5:10 until a homogeneous slurry was formed. The prepared positive electrode slurry was then uniformly coated onto aluminum foil using a preheating apparatus, and subsequently transferred to a vacuum drying oven at 120°C for 12 hours. The required thickness for electrode rolling was calculated based on the compaction density, and the rolled electrodes were then cut into uniform thicknesses with a diameter of 12 mm using a cutting machine. These were then assembled into coin cells in a vacuum glove box. A lithium foil was used as the counter electrode, a Celgard 2300 separator was used, and a LiFP6-based electrolyte was employed.

[0039] As shown in Figures 1-4, the modified lithium-rich manganese-based material has a nano-woven interface structure on its surface, and the main component of the interface structure is lithium phosphate.

[0040] Figure 5 shows the cycling performance of the products obtained in Comparative Example 1 and Example 1 of the present invention, respectively. As can be seen from the figure, at a 1C rate, the initial discharge capacity of the material in Comparative Example 1 is 228.6 mAh·g⁻¹, and the capacity retention rate after 200 cycles is only 69.8%; while the initial discharge capacity of the product obtained in Example 1 of the present invention is 230.1 mAh·g⁻¹, and the capacity retention rate after 200 cycles is as high as 95.8%, indicating that the cycling stability of the lithium-rich manganese-based material with the nano-woven interface structure is improved.

[0041] Using a dilute acid solution as the reaction medium, combined with spray pyrolysis, the dilute acid reacts fully with the residual alkaline compounds on the surface of the layered oxide, and is simultaneously converted in situ into a uniform nano-woven interface structure. This method has significant advantages: (1) It can prepare a uniform nano-interface structure, which is a flexible film structure with strong bonding. The interface structure can exist stably and permanently during charging and discharging, reducing structural strain; (2) The nano-woven interface structure has a large specific surface area, which increases the contact area between the layered oxide material and the electrolyte and the liquid retention, accelerating the diffusion of Li+ and the migration of electrons; (3) The uniform woven interface structure can inhibit the oxidation of the material surface and the reaction with water and carbon dioxide in the air, improve the air tolerance of the matrix material, and also greatly inhibit the erosion of the matrix material by the electrolyte; (4) The preparation process in this invention is simple, saves energy, is low in cost, and is conducive to industrial production.

[0042] Matters not covered in this invention are common knowledge.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A layered oxide material with a nanowoven interface structure, characterized in that: The layered oxide material comprises nickel-rich and lithium-rich materials, with the general structural formula Li. x TM y O2@Li u NM v O w Wherein, 1.0≤x≤1.2, 0.8≤y≤1.0, 0≤u≤15, 1≤x≤15, 1≤w≤15, TM is one or more of nickel, cobalt, manganese and aluminum, and NM is one of boron, phosphorus, sulfur and selenium.

2. A method for preparing layered oxide materials with a nanowoven interface structure, characterized in that: The method includes the following steps: Step 1: Add a certain amount of layered oxide material and dilute acid solution to a stirred reactor and stir for a certain time to obtain a suspension; Step 2: Transfer the suspension to a spray drying device through a peristaltic pump, set a certain feeding rate, inlet air temperature, and outlet air temperature, and collect the dried precursor material at the outlet; Step 3: Transfer the dried precursor material to a vacuum furnace, set a certain calcination temperature and time, and after calcination, a layered oxide material with a nano-woven interface structure can be obtained.

3. The method for preparing layered oxide materials with a nanowoven interface structure according to claim 2, characterized in that: In step 1, the layered oxide material is one or more of the following: lithium-rich manganese-based materials, nickel-rich cathode materials, nickel-rich multi-element materials, and salt rock disordered materials.

4. The method for preparing layered oxide materials with a nanowoven interface structure according to claim 2, characterized in that: In step 1, the dilute acid is one or more of boric acid and phosphoric acid, and the mass ratio of the solid dilute acid to the layered oxide material is 1:100-3:100; the solid-liquid ratio of the layered oxide material to the dilute acid is 0.1-1.0 g / ml; and the ultrasonic stirring time is 30 min-120 min.

5. The method for preparing layered oxide materials with a nanowoven interface structure according to claim 2, characterized in that: In step 2, the feeding rate is 1-6 L / min, and the inlet air temperature is 200 °C. o C, outlet air temperature is 100 o C.

6. The method for preparing layered oxide materials with a nanowoven interface structure according to claim 2, characterized in that: Calcination temperature is 300-600 o C, calcination time is 2-6 hours, and the calcination atmosphere is air.

7. The application of the layered oxide material with a nanowoven interface structure according to claim 1, characterized in that: The layered oxide material is used as a positive electrode active material in batteries.

8. The application of the layered oxide material with a nanowoven interface structure according to claim 7, characterized in that: The battery preparation process of the layered oxide material used as the positive electrode active material is as follows: the layered oxide material is used as the positive electrode active material, PVDF is used as the binder, SP and KS-6 are used as the conductive agents, and NMP is used as the solvent. The active material: binder: conductive agent are stirred and mixed in a mass ratio of 85:5:10 to form a uniform slurry. The prepared positive electrode slurry is uniformly coated on aluminum foil using a preparation device, and then transferred to a vacuum drying oven at 120°C for vacuum drying for 12 hours. The thickness to be achieved by rolling the electrode sheet is calculated based on the compaction density, and the rolling process is performed. The rolled electrode sheet is cut into uniformly thick electrode sheets with a diameter of 12 mm using a cutting machine, and assembled into a button cell in a vacuum glove box. Lithium foil is used as the counter electrode, and LiFP6-based electrolyte is used.

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