Manganese-based sodium-ion battery positive electrode material, preparation method thereof and sodium-ion battery

Abstract

The application provides a preparation method of a manganese-based sodium ion battery positive electrode material, comprising the following steps: uniformly mixing a layered manganese-based sodium ion battery positive electrode material, a sodium source and a phosphorus source to obtain a mixture; performing low-temperature heat treatment on the mixture in a reducing atmosphere; changing the reducing atmosphere into a nitrogen atmosphere and / or an inert atmosphere, increasing the heat treatment temperature, and performing a reaction, and the manganese-based sodium ion battery positive electrode material is obtained. The preparation method can convert part of the surface of the layered manganese-based sodium ion battery positive electrode material into a polyanion type coating layer in situ together with the sodium source and the phosphorus source, thereby effectively inhibiting the evolution of the phase transition of the material at high voltage, preventing the accumulation of internal stress and the nucleation of intracrystalline cracks. Compared with a traditional coating method, the modification effect of the layered manganese-based positive electrode material obtained by the method is better, the adhesion between the coating layer and the substrate is stronger, the compatibility is better, the specific capacity can be improved, and the storage performance is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery materials, and particularly relates to modification of a manganese-based sodium ion battery layered positive electrode material. BACKGROUND

[0002] With the low-carbon clean transformation, the energy consumption mode is constantly changing, and new energy storage materials have attracted widespread attention from academia and industry. Lithium ion secondary batteries as an effective energy storage technology have been commercialized, but the shortage and uneven distribution of lithium resources have prompted us to accelerate the development of low-cost alternatives. Sodium ion batteries, as the most promising alternative technology, have attracted much attention. Transition metal oxides are one of the most promising sodium ion battery cathode materials due to their excellent energy density, high discharge specific capacity and environmental friendliness.

[0003] However, there are two major obstacles to the commercialization of layered transition metal oxides: first, poor air stability. Even brief exposure to ambient air, water and carbon dioxide molecules will be absorbed into the layered structure, and through Na + / H + exchange to form basic substances such as NaOH, NaHCO3 and Na2CO3. These chemical reactions accelerate the extraction of Na + from Na x TMO2. At the same time, the residual base formed on the surface will cause the slurry to gel and the current collector to corrode, which is extremely harmful to the subsequent electrode manufacturing process. The other problem is that the capacity of sodium battery layered oxides is lower than that of lithium batteries. High energy is an effective way to make up for the low capacity of sodium batteries. However, high cut-off voltage will produce irreversible phase transition, resulting in the generation of micro-cracks at the grain boundaries. Micro-cracks accompanied by the occurrence of interface side reactions will lead to structural collapse and rapid capacity decline, so inhibiting or reducing these micro-cracks is the key to improving the electrochemical performance of sodium battery layered oxides. These two major problems are due to the poor surface / interface stability of sodium battery layered materials.

[0004] So far, many strategies have been developed to improve its surface / interface stability. A representative method is to build a protective layer on the surface of sodium battery layered oxides. However, the common coating methods such as wet coating, solid phase coating, etc. are difficult to form a uniform and complete coating layer on the surface of the positive electrode, and the protective effect of the coating layer is poor; if ALD, CVD and other methods are used, the cost will be too high and it will be difficult to implement engineering. Therefore, in-situ construction of continuous, stable and electrochemically active coating layer is the key to improving the performance of layered oxides. Improve the air stability of the material, reduce the hygroscopicity of the sodium ion material, and improve the cycle stability of the material. SUMMARY

[0005] In order to solve the above technical problems, the application provides a modified manganese-based sodium ion battery layered positive electrode material, a preparation method thereof and a sodium ion battery.

[0006] In order to achieve the above-mentioned purpose, the application provides the following solutions:

[0007] The application provides a preparation method of a manganese-based sodium ion battery positive electrode material, comprising:

[0008] (1) uniformly mixing a layered manganese-based sodium ion battery positive electrode material, a sodium source and a phosphorus source to obtain a mixture;

[0009] (2) performing low-temperature heat treatment on the mixture in a reducing atmosphere;

[0010] (3) changing the reducing atmosphere into a nitrogen atmosphere and / or an inert atmosphere, increasing the heat treatment temperature, and performing reaction, and thus the manganese-based sodium ion battery positive electrode material is obtained.

[0011] Preferably, in step (2), the temperature of the low-temperature heat treatment is 150-500 DEG C; and the time of the low-temperature heat treatment is 2-10 h.

[0012] Preferably, in step (2), the reducing atmosphere is one or more of hydrogen, ammonia, carbon monoxide, sulfur dioxide, hydrogen sulfide, methane and ethylene.

[0013] Preferably, the reducing atmosphere is constructed by introducing a reducing gas into a reaction device, and the flow rate of the reducing gas is 0.1-5 mL / min.

[0014] Preferably, in step (3), the temperature of the reaction is 300-900 DEG C.

[0015] Preferably, in step (3), the time of the reaction is 2-10 h.

[0016] Preferably, the chemical formula of the layered manganese-based sodium ion battery positive electrode material is Na x Mn y M z O2, wherein M is selected from one or more of Ni, Co, Fe, Cu, Cr and Ti, wherein 0

[0017] Preferably, the sodium source is one or more of NaOH, NaHCO3, Na2CO3 and NaH2PO4.

[0018] Preferably, the phosphorus source is one or more of NH4H2PO4, (NH4)2HPO4, (NH4)3PO4, Na3PO4·12H2O and sodium metaphosphate.

[0019] As a preference, the molar ratio of sodium to phosphorus in the sodium source and the phosphorus source is 1.1:1~1:1.

[0020] As a preference, the molar ratio of the positive electrode material to the phosphorus in the sodium source and the phosphorus source is 10:1~100:1.

[0021] As a general inventive concept, the present application also provides a manganese-based sodium ion battery positive electrode material prepared by the aforementioned preparation method.

[0022] As a general inventive concept, the present application also provides a sodium ion battery comprising the aforementioned manganese-based sodium ion battery positive electrode material.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1、The present application can convert part of the surface of the layered manganese-based sodium ion battery positive electrode material and the sodium source and the phosphorus source into a polyanion-type coating layer in situ by mixing the layered manganese-based sodium ion battery positive electrode material with the sodium source and the phosphorus source, then performing low-temperature heat treatment in a reducing atmosphere, and then performing higher-temperature treatment in a protective atmosphere. On the one hand, this can reduce the surface residual alkali, and on the other hand, it can effectively inhibit the evolution of material phase transition at high voltage, prevent the accumulation of internal stress and the nucleation of intracrystalline cracks. Compared with traditional coating methods, the modification effect of the layered manganese-based positive electrode material obtained by this method is better, the adhesion of the coating layer to the substrate is stronger, the compatibility is better, and thus the modification effect is better. This method can prepare a dual-phase composite sodium ion battery positive electrode material. The positive electrode material can provide a higher capacity, and the polyanion-type structure on the surface can isolate the corrosion of wet air on the positive electrode material, enhance the stability of the material surface / interface, and significantly improve the storage performance of the battery.

[0025] 2、The preparation method of the present application is simple and easy to implement, and can realize continuous, stable, and in-situ construction of an electrochemically active coating layer. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 XRD pattern of the manganese-based sodium ion battery positive electrode material prepared for Example 1 and exploration experiment.

[0028] Figure 2 Structure schematic diagram of the composite dual-phase sodium battery positive electrode material prepared by the method of the present application. DETAILED DESCRIPTION

[0029] Some embodiments of the present application provide a method for preparing a manganese-based sodium-ion battery cathode material, comprising:

[0030] (1) mixing a layered manganese-based sodium-ion battery cathode material with a sodium source and a phosphorus source uniformly to obtain a mixture;

[0031] (2) performing low-temperature heat treatment on the mixture under a reducing atmosphere;

[0032] (3) changing the reducing atmosphere to a nitrogen atmosphere or an inert atmosphere, increasing the heat treatment temperature, and performing a reaction, thereby obtaining the manganese-based sodium-ion battery cathode material.

[0033] In some preferred embodiments, in step (2), the temperature of the low-temperature heat treatment is 150-500°C, and is further preferably 300-500°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, and the like.

[0034] In some preferred embodiments, in step (2), the time of the low-temperature heat treatment is 2-10 h, and is further preferably 3-6 h, including 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, and the like.

[0035] In some preferred embodiments, in step (2), the reducing atmosphere is one or more of hydrogen, ammonia, carbon monoxide, sulfur dioxide, hydrogen sulfide, methane, and ethylene.

[0036] In some preferred embodiments, the reducing atmosphere is constructed by introducing a reducing gas into the reaction equipment, and the introduction speed of the reducing gas is 0.1-5 mL / min, and is further preferably 1-4 mL / min, such as 1 mL / min, 1.5 mL / min, 2 mL / min, 2.5 mL / min, 3 mL / min, 3.5 mL / min, 4 mL / min, and the like.

[0037] In some embodiments, steps (2) and (3) can be performed in a conventional furnace body, such as a muffle furnace, a tube furnace, or other atmosphere furnaces, and a reducing gas is introduced in step (2) and nitrogen and / or inert gas is introduced in step (3).

[0038] In some preferred embodiments, in step (3), the temperature of the reaction is 300-900°C, and is further preferably 500-650°C, such as 500°C, 550°C, 600°C, 650°C, and the like.

[0039] In some preferred embodiments, in step (3), the reaction time is 2-10 h, further preferably 6-10 h, for example 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, etc.

[0040] In some preferred embodiments, the layered manganese-based sodium-ion battery cathode material has a chemical formula of Na x Mn y M z O2, wherein M is selected from one or more of Ni, Co, Fe, Cu, Cr, Ti, wherein 0

[0041] In some preferred embodiments, the sodium source is one or more of NaOH, NaHCO3, Na2CO3, NaH2PO4.

[0042] In some preferred embodiments, the phosphorus source is one or more of NH4H2PO4, (NH4)2HPO4, (NH4)3PO4, Na3PO4·12H2O, sodium metaphosphate.

[0043] In some preferred embodiments, the molar ratio of sodium to phosphorus in the sodium source and the phosphorus source is 1.1:1-1:1, for example 1.1:1, 1.05:1, 1:1, etc.

[0044] The molar ratio of the cathode material to phosphorus in the sodium source and the phosphorus source is 10:1-100:1, further preferably 50:1-100:1, further preferably 80:1-100:1, for example 80:1, 85:1, 90:1, 95:1, 100:1, etc.

[0045] In some embodiments, in step (1), the uniform mixing is achieved by solid-phase mixing.

[0046] In some embodiments, in step (3), the inert atmosphere is one or more of argon, helium, neon, krypton, xenon.

[0047] In some preferred embodiments, in step (3), the cooling method after the reaction can be furnace cooling.

[0048] In some embodiments, a manganese-based sodium-ion battery cathode material is also provided, which is prepared by the above preparation method.

[0049] Some embodiments also provide a sodium-ion battery comprising the aforementioned manganese-based sodium-ion battery cathode material.

[0050] For the purpose of facilitating the understanding of the present application, the present application will be described in further detail below with reference to the accompanying drawings and preferred embodiments. However, the scope of protection of the present application is not limited to the following specific embodiments.

[0051] Example 1

[0052] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was mixed with Na2CO3 and NH4H2PO4 in a mortar at a molar ratio of 100:0.5:1, and then placed in a muffle furnace. Ammonia gas was introduced into the muffle furnace at a flow rate of 1 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min, and then maintained for 3 h. Subsequently, nitrogen gas was introduced into the muffle furnace, and the temperature was raised to 600°C at a rate of 3°C / min, and then maintained for 10 h. After cooling, a surface in-situ phase transition cathode material was obtained. XRD analysis of the material showed that only characteristic peaks of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 were found, and the reason for this was that the content of the coating formed on the surface was too low, and thus the composition of the coating could not be obtained through phase analysis.

[0053] In order to explore the composition of the coating formed on the surface of the NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 cathode material, the following exploratory experiment was performed by increasing the amount of coating raw material:

[0054] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was mixed with Na2CO3 and NH4H2PO4 in a mortar at a molar ratio of 10:6:6, and then placed in a muffle furnace. Ammonia gas was introduced into the muffle furnace at a flow rate of 1 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min, and then maintained for 5 h. Subsequently, the temperature was raised to 500°C at a rate of 3°C / min, and then maintained for 5 h. After cooling, a surface in-situ phase transition cathode material was obtained. XRD analysis of the obtained material showed that, as shown in FIG. 2, NaNi Figure 1 Fe Figure 1 Mn 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and Na4M3(PO4)2P2O7 were found in the material, indicating that NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3The coating formed on the surface of the O2 cathode material is mainly Na4M3(PO4)2P2O7, so it can be inferred that the material prepared in Example 1 is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2@Na4M3(PO4)2P2O7, and the thermodynamic calculation verifies that the oxides of tetravalent and trivalent Mn, the oxide of trivalent Fe, and the oxides of trivalent and tetravalent nickel can be reduced to divalent metal oxides under heating conditions. It is inferred that M can be Ni, Fe, and Mn. Analysis shows that the Na4M3(PO4)2P2O7 formed on the surface is based on the reduction of Fe, Mn, and Ni in the matrix material to form divalent oxides MO, and then the in-situ reaction of MO with Na2CO3 and NH4H2PO4 to form a polyanion phase coating layer Na4M3(PO4)2P2O7.

[0055] Example 2

[0056] Na 0.67 MnO2, Na2CO3, and NH4H2PO4 were mixed in a mortar at a molar ratio of 100:0.5:1, and then placed in a muffle furnace. Argon-hydrogen mixed gas was introduced into the muffle furnace at a flow rate of 1 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min, and then held for 3 h. Subsequently, argon was introduced, and the temperature was raised to 600°C at a rate of 3°C / min, and then held for 10 h. After cooling, the surface in-situ phase transition cathode material Na 0.67 MnO2@Na4Mn3(PO4)2P2O7.

[0057] Example 3

[0058] NaNi 0.4 Fe 0.2 Mn 0.2 Ti 0.2 O2, Na2CO3, and NH4H2PO4 were mixed in a mortar at a molar ratio of 100:0.55:1, and then placed in a muffle furnace. Argon-hydrogen mixed gas was introduced into the muffle furnace at a flow rate of 3 ml / min, and the temperature was raised to 500°C at a rate of 3°C / min, and then held for 4 h. Subsequently, argon was introduced, and the temperature was raised to 700°C at a rate of 3°C / min, and then held for 6 h. After cooling, the surface in-situ phase transition cathode material was obtained.

[0059] Example 4

[0060] NaNi 0.4 Fe 0.2 Mn 0.4O2, Na2CO3 and NH4H2PO4 were mixed in a mortar at a molar ratio of 50:0.5:1, and then placed in a muffle furnace. Argon-hydrogen mixed gas was introduced into the muffle furnace at a flow rate of 5 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min. After 3 h of heat preservation, the argon gas was introduced, and the temperature was raised to 600°C at a rate of 3°C / min. After 8 h of heat preservation, the surface in-situ phase transition positive electrode material was obtained after cooling.

[0061] Example 5

[0062] NaNi l / 9 Ni 2 / 9 Fe l / 3 Mn l / 3 O2, Na2CO3 and NH4H2PO4 were mixed in a mortar at a molar ratio of 10:0.525:1, and then placed in a muffle furnace. Argon-hydrogen mixed gas was introduced into the muffle furnace at a flow rate of 1 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min. After 6 h of heat preservation, the argon gas was introduced, and the temperature was raised to 600°C at a rate of 3°C / min. After 10 h of heat preservation, the surface in-situ phase transition positive electrode material was obtained after cooling.

[0063] Comparative Example 1

[0064] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na2CO3 and NH4H2PO4 were mixed in a mortar at a molar ratio of 100:0.5:1, and then placed in a muffle furnace. Nitrogen gas was introduced into the muffle furnace at a flow rate of 1 ml / min, and the temperature was raised to 300°C at a rate of 3°C / min. After 3 h of heat preservation, the temperature was raised to 600°C at a rate of 3°C / min. After 10 h of heat preservation, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2@NaPO3.

[0065] According to the mass ratio (active material: conductive agent: binder = 8:1:1), 0.08 g of the manganese-based sodium ion battery positive electrode material obtained in Example 1, Example 2, Comparative Example 1, and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na 0.67 MnO2, and 0.01 g of acetylene black as a conductive agent and 0.01 g of polyvinylidene fluoride as a binder were weighed, mixed in a mortar, and then mixed with N-methylpyrrolidone as a dispersant. After mixing again, the positive electrode sheet was coated on an aluminum foil, and a CR2032 button cell was assembled in a glove box under an inert protective atmosphere with lithium metal as the negative electrode.

[0066] The assembled battery was rested, and then electrochemical performance test was carried out. The coin cell was subjected to first charge-discharge at 0.2C under 2-4V voltage range, and then subjected to charge-discharge cycle at 1C rate. The performance parameters are shown in Table 1.

[0067] Table 1 Electrochemical performance of the battery assembled by each positive electrode material

[0068]

[0069] As can be seen from Table 1, the capacity and cycle performance of the battery assembled by the positive electrode material of Example 1 are obviously better than those of the battery assembled by the positive electrode material of Comparative Example 1 and the unmodified material. The cycle performance of the material after in-situ phase transition of the surface sodium ion battery layered material is obviously improved. Taking Example 1, Comparative Example 1 and the unmodified material as examples, it can be found that the composite material with layered / polyanion structure has better cycle performance than the positive electrode material modified by NaPO3 coating or unmodified. Through analysis, the main reason for the improvement of the electrochemical performance of the in-situ phase transition material is that the layered material in the bulk is easy to undergo phase transition after the sodium ion is removed due to the structural instability, and after the surface of the layered oxide is reduced and the core is reacted to form the NASICON outer layer, the NASICON outer layer can stabilize the phase structure of the material and reduce the generation of microcracks, thereby improving the cycle performance of the material, and the adhesion between the in-situ formed coating layer and the substrate is stronger, and the modification effect is stronger. As can be seen from Examples 1 and 2, the surface in-situ phase transition not only has obvious effect on the electrochemical performance of the layered O3 phase structure material, but also can obviously improve the electrochemical performance of the layered positive electrode material with P2 phase structure.

[0070] The materials prepared in Examples 1-5 and Comparative Example 1, the uncoated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na 0.67 MnO2 material were assembled into batteries according to the above method. After the electrochemical performance of the batteries stored in humid air (humidity 60%RH) for 30 days was tested, the coin cell was subjected to first charge-discharge at 0.2C under 2-4V voltage range, and then subjected to charge-discharge cycle at 1C rate. The performance parameters are shown in Table 2.

[0071] Table 2 Electrochemical performance of the battery assembled by each positive electrode material after storage in humid air (humidity 60%RH) for 30 days

[0072]

[0073] As can be seen from Table 2, the battery assembled with the positive electrode material prepared in Example 1 has obvious advantages in the electrical performance (including discharge specific capacity and cycle performance) after storage over the battery assembled with the positive electrode material prepared in Comparative Example 1 and the battery assembled with the unmodified material, indicating that the storage performance of the material prepared by the preparation method of the application is obviously improved. The possible reason for this phenomenon is that the O3 / P2-based layered manganese-based sodium-ion battery positive electrode material has strong water absorption, so it is easy to cause the battery performance to decrease obviously due to water absorption and the increase of surface residual alkali during storage. The positive electrode material prepared in Example 1 can avoid the water absorption of the material and the increase of the surface residual alkali due to the formation of the in-situ dense coating layer on the surface, and the in-situ dense coating layer has better coating modification effect, so the electrochemical performance after storage is obviously improved.

[0074] Figure 2 A schematic structural diagram of the composite two-phase sodium battery positive electrode material prepared by the method of the application, wherein the outside is a NASICON structure and the inside is a layered structure.

[0075] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A method for preparing a manganese-based sodium ion battery positive electrode material, characterized in that: The steps include: (1) uniformly mixing a layered manganese-based sodium ion battery positive electrode material with a sodium source and a phosphorus source to obtain a mixture; (2) subjecting the mixture to low-temperature heat treatment in a reducing atmosphere; (3) The reducing atmosphere is converted into a nitrogen atmosphere and / or an inert atmosphere, the heat treatment temperature is increased, and the reaction is carried out to obtain the obtained product; the preparation method converts the surface of the partially layered manganese-based sodium ion battery positive electrode material and the sodium source and phosphorus source into a polyanion coating layer in situ.

2. The method for preparing a manganese-based sodium ion battery positive electrode material according to claim 1, wherein: In step (2), the temperature of the low-temperature heat treatment is 150-500°C; the time of the low-temperature heat treatment is 2-10 h.

3. The method for preparing a manganese-based sodium ion battery positive electrode material according to claim 1, wherein: In step (2), the reducing atmosphere is one or a mixture of two or more of hydrogen, ammonia, carbon monoxide, sulfur dioxide, hydrogen sulfide, methane, and ethylene.

4. The method for preparing a manganese-based sodium ion battery positive electrode material according to claim 3, wherein: The reducing atmosphere is constructed by introducing reducing gas into the reaction device, and the flow rate of the reducing gas is 0.1-5 mL / min.

5. The method for preparing a manganese-based sodium ion battery positive electrode material according to any one of claims 1 to 4, wherein: In step (3), the reaction temperature is 300-900°C; In step (3), the reaction time is 2 to 10 h.

6. The method for preparing a manganese-based sodium ion battery cathode material according to any one of claims 1 to 4, wherein: The chemical formula of the layered manganese-based sodium ion battery positive electrode material is Na x Mn y M z O2, wherein M is selected from one or more of Ni, Co, Fe, Cu, Cr, and Ti, wherein 0<y≤1, 0≤z<1, y+z=1, and 0.6≤x≤1.

7. The method for preparing a manganese-based sodium ion battery positive electrode material according to any one of claims 1 to 4, wherein: The sodium source is one or more of NaOH, NaHCO3, Na2CO3, and NaH2PO4; The phosphorus source is one or more of NH4H2PO4, (NH4)2HPO4, (NH4)3PO4, Na3PO4·12H2O, and sodium metaphosphate.

8. The method for preparing a manganese-based sodium ion battery cathode material according to any one of claims 1 to 4, wherein: The molar ratio of sodium to phosphorus in the sodium source and the phosphorus source is 1.1:1 to 1:1; the molar ratio of the positive electrode material to the phosphorus in the sodium source and the phosphorus source is 10:1 to 100:

1.

9. A manganese-based sodium ion battery cathode material, characterized in that: The method is as described in any one of claims 1 to 8.

10. A sodium ion battery, characterized in that Comprising the manganese-based sodium ion battery positive electrode material as claimed in claim 9.

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