Composite layered oxide positive electrode material and preparation method thereof

Abstract

This invention provides a composite layered oxide cathode material and its preparation method, comprising the following steps: S1, mixing sodium prussiate of Taurine with the layered oxide material, adding water for ball milling, and dehydrating the ball-milled mixture; S2, adding Prussian blue precursor or metal salt M... x N y The material processed in step S1 is mixed with the material after ball milling; S3, the material after ball milling in step S2 is post-processed to obtain the composite layered oxide cathode material. This invention involves Prussian blue coating synthesis on the surface of the layered oxide material, resulting in good coating effect, large coating amount, and a battery with a large specific capacity.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode materials, and in particular to a composite layered oxide cathode material and its preparation method. Background Technology

[0002] Currently, the application of lithium-ion batteries in electric vehicles, 3C products, and energy storage is growing rapidly. However, global available lithium resources are expected to be insufficient to meet demand in the future, necessitating the search for battery technologies that are not limited by resources. Sodium is abundant in the Earth's crust and does not face resource depletion limitations. Furthermore, sodium-ion batteries operate on similar principles to lithium-ion batteries, utilizing the same manufacturing equipment, and offer the advantage of low material costs. Therefore, sodium-ion batteries are among the most promising new battery technologies for industrial application, with broad prospects in areas such as large-scale energy storage and low-speed vehicles.

[0003] The cathode material is the most crucial component of a sodium-ion battery, directly determining its capacity. Currently, layered oxide cathode materials (NaM1) are the most common type used in sodium-ion batteries. x M2 y M3 1-x-y O2 has a wide range of applications. This material has the advantages of easy synthesis, stable cycling performance, excellent low-temperature performance, and excellent rate performance. When charged to 4.0V, the specific capacity can reach 140mAh / g, and when the voltage exceeds 4.2V, the specific capacity reaches 170mAh / g. However, layered oxides are extremely unstable above 4V, and their capacity is prone to rapid decay, leading to a rapid decline in performance. Furthermore, layered oxide materials have extremely high residual alkali on their surface, often with a pH value exceeding 12.5, even reaching 13. This causes the material to easily absorb water during the slurry coating process, resulting in coating failure, powder shedding during rolling, and a corresponding decrease in electrochemical performance. Surface treatment is usually performed on layered oxide materials to solve the problem of excessive residual alkali on the material surface. However, most existing technologies achieve this by coating the surface with carbon materials or using Al2O3 or TiO2. These materials do not have electrochemical activity, and the process is complicated. The coating thickness should not be too large, otherwise the specific capacity will be greatly reduced. Moreover, the coating layer will crack or even fail under long-term use. The impact on the specific capacity of the material leads to a significant negative impact of the coating, which is counterproductive. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite layered oxide cathode material and its preparation method.

[0005] This invention provides the following technical solution:

[0006] This invention provides a method for preparing a composite layered oxide cathode material, comprising the following steps:

[0007] S1. Mix sodium ferrocyanide with layered oxide materials, add water and ball mill, and dehydrate the mixture after ball milling.

[0008] S2. Prussian blue precursor or metal salt M x N y After mixing with the material processed in step S1, the mixture is ball-milled.

[0009] S3. Post-process the material after ball milling in step S2 to obtain the composite layered oxide cathode material.

[0010] The mass ratio of layered oxide material to sodium prussiate blue is 90-98:2-10, and the mass ratio of layered oxide material to Prussian blue precursor or metal salt M is... x N y The mass ratio of added components is 92-99:1-8.

[0011] Furthermore, the layered oxide material is NaM1. x M2 y M3 1-x-y O2, M1, M2, and M3 are Fe 2+ Ni 2+ Mn 2+ Cu + Co 2+ Ti + or V + One of them.

[0012] Furthermore, the Prussian blue precursor is Fe4[Fe(CN)6]3.

[0013] Furthermore, the metal salt M x N y In this context, M represents one or more of Fe, Mn, Cu, Ni, Co, Ti, and V, and N represents one of sulfate, oxalate, citrate, carbonate, nitrate, bicarbonate, and acetate.

[0014] Further, in step S1, the dehydration treatment is: drying at 100-160°C for 4 hours.

[0015] Furthermore, in step S2, the Prussian blue precursor or metal salt M x N y After dehydration.

[0016] Further, in step S3, the post-processing is as follows: when using Prussian blue precursor in step S2, the material after ball milling in step S2 is subjected to drying heat treatment at 150°C for 6 hours; when using metal salt M in step S2... x N yThen, the material after ball milling in step S2 is washed to remove excess impurities, and then vacuum dried at 170℃ for 12 hours.

[0017] The present invention also provides a composite layered oxide cathode material prepared by the above preparation method.

[0018] The composite layered oxide cathode material has a core-shell structure, including a core and a coating layer. The core is a layered oxide material, and the coating layer is a Prussian blue-based material, with the coating layer accounting for 5-10% of the total mass.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention involves the coating synthesis of Prussian blue on the surface of layered oxide materials, with coating occurring simultaneously with the reaction. The surface coating is uniform and the coating thickness is controllable. Appropriate coating of Prussian blue materials can improve the transfer rate of sodium ions due to their large spatial channels. At the same time, Prussian blue materials have the characteristic of high specific capacity. By doping and coating at the above mass ratio, the specific capacity of the composite material can be increased by 4-8%.

[0021] 2. Prussian blue materials have good metal containment and adsorption properties, which can effectively alleviate the problems of jelly-like appearance and decreased circulation caused by water absorption in layered oxides during processing; on the other hand, layered oxides have a more stable spatial structure, which can provide effective support in the core and improve circulation performance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a SEM image of the material provided in Embodiment 2 of the present invention;

[0024] Figure 2 This is the first charge-discharge curve provided in Embodiment 1 of the present invention;

[0025] Figure 3 This is the first charge-discharge curve provided in Embodiment 2 of the present invention;

[0026] Figure 4 This is the first charge-discharge curve provided in Embodiment 3 of the present invention;

[0027] Figure 5 This is the first charge-discharge curve provided in Embodiment 4 of the present invention;

[0028] Figure 6 This is the first charge-discharge curve provided in Embodiment 5 of the present invention;

[0029] Figure 7 This is the first charge-discharge curve provided in Embodiment 6 of the present invention;

[0030] Figure 8 This is a first charge-discharge curve provided for Comparative Example 1 of the present invention;

[0031] Figure 9 The first charge-discharge curve is provided for Comparative Example 2 of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0035] 1. Take 0.25g of sodium chlorophyll (Na₄Fe(CN)₆) and 10g of material (NaTi). 0.4 Fe 0.2 Mn 0.4 O2 is mixed and a small amount of water is added. The mixture is ball-milled for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. The ball-milled material is then dried and dehydrated. Finally, the material is placed in a vacuum oven at 100-160℃ for 4 hours for deep dehydration.

[0036] 2. Take 0.23g of Prussian blue precursor Fe4[Fe(CN)6]3 after dehydration treatment (drying and dehydration treatment in a vacuum oven at 80-120℃ for 4h) and mix it with the material after ball milling in step 1. Place it in a ball mill, add ball milling beads, and carry out a rapid ball milling reaction at 450rpm. Sodium ferrocyanide material and Prussian blue precursor will undergo a solid-phase reaction to obtain product Na2Fe[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 5%.

[0037] 3. The product after ball milling in step 2 is heat-treated in a vacuum oven at 150°C for 6 hours to remove water and optimize the material lattice structure, thereby obtaining a composite layered oxide cathode material.

[0038] Example 2

[0039] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0040] 1. Take 0.5g of sodium chlorophyll and 10g of material NaNi 0.3 Fe 0.3 Mn 0.3 O2 is mixed and a small amount of water is added. The mixture is ball-milled for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. The ball-milled material is then dried and dehydrated. Finally, the material is placed in a vacuum oven at 100-160℃ for 4 hours for deep dehydration.

[0041] 2. Take 0.46g of Prussian blue precursor Fe4[Fe(CN)6]3 after dehydration treatment (drying and dehydration treatment in a vacuum oven at 80-120℃ for 4h) and mix it with the material after ball milling in step 1. Place it in a ball mill, add ball milling beads, and carry out a rapid ball milling reaction at 450rpm. Sodium ferrocyanide and Prussian blue precursor will undergo a solid-phase reaction to obtain the product Na2Fe[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 10%.

[0042] 3. The product after ball milling in step 2 is heat-treated in a vacuum oven at 150°C for 6 hours to remove water and optimize the material lattice structure, thereby obtaining a composite layered oxide cathode material.

[0043] Example 3

[0044] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0045] 1. Take 0.485g of sodium chlorophyll and 10g of NaCu. 0.1 Ni 0.2 Fe 0.3 Mn 0.3 O2 is mixed and a small amount of water is added. The mixture is ball-milled for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. The ball-milled material is then dried and dehydrated. Finally, the material is placed in a vacuum oven at 100-160℃ for 4 hours for deep dehydration.

[0046] 2. Take 0.23g of dehydrated manganese oxalate (dried in a vacuum oven at 100-160℃ for 4h) and mix it with the material after ball milling in step 1. Place the mixture in a ball mill, add ball milling beads, and perform a rapid ball milling reaction at 450rpm. Sodium ferrous sulfate and manganese oxalate will undergo a solid-phase reaction to obtain the product Na2Mn[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 5%.

[0047] 3. Wash the product after ball milling in step 2 with deionized water and anhydrous ethanol to remove excess impurities, and then vacuum dry it at 170℃ for 12 hours to obtain the composite layered oxide cathode material.

[0048] Example 4

[0049] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0050] 1. Take 0.97g of sodium chlorophyll and 10g of NaCl. 0.2 Fe 0.4 Mn 0.4 O2 is mixed and a small amount of water is added. The mixture is ball-milled for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. The ball-milled material is then dried and dehydrated. Finally, the material is placed in a vacuum oven at 100-160℃ for 4 hours for deep dehydration.

[0051] 2. Take 0.37g of dehydrated manganese carbonate (dried in a vacuum oven at 100-160℃ for 4h) and mix it with the material after ball milling in step 1. Place the mixture in a ball mill, add ball milling beads, and perform a rapid ball milling reaction at 450rpm. Sodium ferrous sulfate and manganese carbonate will undergo a solid-phase reaction to obtain the product Na2Mn[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 10%.

[0052] 3. Wash the product after ball milling in step 2 with deionized water and anhydrous ethanol to remove excess impurities, and then vacuum dry it at 170℃ for 12 hours to obtain the composite layered oxide cathode material.

[0053] Example 5

[0054] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0055] 1. Take 0.97g of sodium cyanide and 10g of material NaNi. 0.2 Fe 0.4 Mn 0.4 Mix with O2, add a small amount of water and ball mill for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. After ball milling, dry the material to remove water, and then place the material in a vacuum oven at 100-160 degrees Celsius for 4 hours to remove water for deep dehydration.

[0056] 2. Take 0.46g of dehydrated ferric oxalate (dried in a vacuum oven at 100-160℃ for 4h) and mix it with the material after ball milling in step 1. Place the mixture in a ball mill, add ball milling beads, and perform a rapid ball milling reaction at 450rpm. Sodium ferric oxalate and ferric oxalate will undergo a solid-phase reaction to obtain the product Na2Fe[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 10%.

[0057] 3. Wash the product after ball milling in step 2 with deionized water and anhydrous ethanol to remove excess impurities, and then vacuum dry it at 170℃ for 12 hours to obtain the composite layered oxide cathode material.

[0058] Example 6

[0059] The specific process for preparing the composite layered oxide cathode material in this embodiment is as follows:

[0060] 1. Take 0.485g of sodium chlorophyll and 10g of material NaV 0.1 Ni 0.1 Fe 0.4 Mn 0.4 O2 is mixed and a small amount of water is added. The mixture is ball-milled for 4 hours to make sodium ferrocyanide evenly coat the surface of the layered oxide material. The ball-milled material is then dried and dehydrated. Finally, the material is placed in a vacuum oven at 100-160℃ for 4 hours for deep dehydration.

[0061] 2. Take 0.745g of dehydrated titanium oxalate (dried in a vacuum oven at 100-160℃ for 4h) and mix it with the material after ball milling in step 1. Place the mixture in a ball mill, add grinding balls, and perform a rapid ball milling reaction at 450rpm. Sodium ferrocyanide and titanium oxalate will undergo a solid-phase reaction to obtain the product Na2Ti[Fe(CN)6]. This material coats the surface of the layered oxide material, forming a core-shell structure with a coating layer, and the coating content is 10%.

[0062] 3. Wash the product after ball milling in step 2 with deionized water and anhydrous ethanol to remove excess impurities, and then vacuum dry it at 170℃ for 12 hours to obtain the composite layered oxide cathode material.

[0063] Comparative Example 1

[0064] 1. Take 2g of sucrose and 10g of Ni 0.1 Fe 0.4 Mn 0.4 O2(OH )2 Mixing, the Ni 0.1 Fe 0.4 Mn 0.4 O2(OH )2As a precursor material for ternary layered oxide materials, 4.9181 g of sodium carbonate material in the corresponding stoichiometric ratio was added and ball-milled for 4 hours.

[0065] 2. Place the ball-milled material in a tube furnace and heat it under a nitrogen atmosphere for 12 hours. Then take it out and crush and ball-mill it. Wash the ball-milled product with deionized water and anhydrous ethanol to remove excess impurities. Then vacuum dry it at 170°C for 12 hours to obtain the composite carbon-coated layered oxide cathode material.

[0066] Comparative Example 2

[0067] 1. Take 2g of sucrose and 10g of NaNi. 0.1 Fe 0.4 Mn 0.4 O2 is mixed and ball milled for 4 hours, and then the material is placed in a tube furnace and heated in a nitrogen atmosphere for 12 hours.

[0068] 2. The material from step 1 is ball-milled. After ball milling, the product is washed once with deionized water and once with anhydrous ethanol to remove excess impurities. Then it is vacuum-dried at 170°C for 12 hours to obtain composite carbon-coated layered oxide cathode material.

[0069] The materials prepared in the above examples were dispersed with Super-P and PVdF in NMP solution at a ratio of 90:5:5, with a solid content of 60%. After dispersion, the materials were coated to obtain electrodes, which were then assembled into CR2032 half-cells. Their electrochemical performance was tested, and the charge-discharge curves are shown in the figure. Figure 2-9 The specific capacity data of the materials prepared in each example are shown in Table 1:

[0070] Table 1. Performance test data of the cathode materials prepared in each example assembled into half-cells.

[0071] Battery Charging capacity Discharge capacity Coulomb efficiency Diaphragm internal resistance Example 1 145.9 138.2 94.7％ <![CDATA[24.1 mΩ / cm 2 > Example 2 145.7 136.8 93.9％ <![CDATA[22.4 mΩ / cm 2 > Example 3 146 137.5 94.2％ <![CDATA[22.2 milliohms / cm 2 > Example 4 147.5 139.1 94.3％ 23.6 milliohms / cm Example 5 147.2 137.9 93.7％ 23.1 milliohms / cm Example 6 147.5 139.5 94.6％ 22.8 milliohms / cm Comparative Example 1 140.1 130.6 93.2％ 29.1 milliohms / cm Comparative Example 2 128.2 118.5 92.6％ 31.2 milliohms / cm

[0072] Compared to composite carbon-coated cathode materials, the Prussian blue-based cathode material coated in this invention exhibits higher specific capacity and coulombic efficiency. Because the Prussian blue coating is synthesized on the surface of the layered oxide material, the coating process occurs simultaneously with the reaction, resulting in uniform surface coating and controllable coating thickness. The larger spatial channels provided by the appropriately coated Prussian blue-based material can improve the sodium ion transfer rate. Simultaneously, the layered oxide has a more stable spatial structure, providing effective support to the core and improving cycle performance.

[0073] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a composite layered oxide positive electrode material, characterized by, Includes the following steps: S1. Mix sodium ferrocyanide with layered oxide materials, add water and ball mill, and dehydrate the mixture after ball milling. S2, mixing the prussian blue precursor or metal salt M x N y ball milling after mixing with the material treated in step S1 ; S3. Post-process the material after ball milling in step S2 to obtain the composite layered oxide cathode material. The mass ratio of layered oxide material to sodium prussiate blue is 90-98:2-10, and the mass ratio of layered oxide material to Prussian blue precursor or metal salt M is... x N y The mass ratio of addition is 92-99:1-8; The layered oxide material is NaTi 0.4 Fe 0.2 Mn 0.4 O2, NaCo 0.2 Fe 0.4 Mn 0.4 O2, NaV 0.1 Ni 0.1 Fe 0.4 Mn 0.4 One of the O2 types; The Prussian blue precursor is Fe4[Fe(CN)6]3; said metal salt M x N y is one of manganese carbonate, titanium oxalate; In step S1, the dehydration treatment is: drying at 100~160℃ for 4 hours; In step S2, the Prussian blue precursor or metal salt M x N y after the dehydration treatment; In step S3, the post-processing is as follows: when using Prussian blue precursor in step S2, the material after ball milling in step S2 is subjected to drying heat treatment at 150°C for 6 hours; when using metal salt M in step S2... x N y During this process, the material after ball milling in step S2 is washed to remove excess impurities, and then vacuum dried at 170°C for 12 hours. The composite layered oxide cathode material has a core-shell structure, including a core and a coating layer. The core is a layered oxide material, and the coating layer is a Prussian blue-based material. The mass of the coating layer is 5-10%.

2. The composite layered oxide cathode material prepared by the preparation method described in claim 1.

3. The composite layered oxide cathode material of claim 2, which is a core-shell structure, characterized in that: It includes a core and a coating layer, wherein the core is a layered oxide material and the coating layer is a Prussian blue-like material, and the mass of the coating layer is 5-10%.

Images