Magnesium-doped sodium ion battery positive electrode material, preparation method and application

Abstract

The invention belongs to the technical field of sodium ion battery positive electrode material manufacturing, particularly provides a magnesium-doped sodium ion battery positive electrode material, a preparation method and application, and aims to solve the problem that sodium ion transmission is not facilitated due to the fact that sodium layer spacing of a sodium ion battery positive electrode material in the prior art is too small. The general chemical formula of the magnesium-doped sodium ion battery positive electrode material is NaNi < 0.6-x > Fe < 0.25 > Mn < 0.15 > Mg < x > O < 2 >, x is smaller than or equal to 0.05; a co-precipitation method is utilized, magnesium is doped in a precursor preparation stage, so that magnesium can smoothly enter a transition metal layer, in the frequent deintercalation process of sodium, the effect of stabilizing a layered structure is achieved, the change of the layered structure can be reduced, the cycle life of the material is ensured, the interlayer spacing of sodium can be enlarged through doping of magnesium, transmission of sodium ions is facilitated, and the service life of the material is prolonged. The rate capability of the material is improved, so that the material has excellent electrochemical performance at normal temperature and low temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing positive electrode materials for sodium ion batteries, and specifically provides a magnesium-doped positive electrode material for sodium ion batteries, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries have many advantages such as high energy density and long cycle life, and are one of the main means of electrochemical energy storage. With the continuous development of technology, lithium-ion batteries not only basically cover the portable product market, but also enter the fields of automobiles and large-scale energy storage at a very fast speed; however, the development and promotion of lithium-ion battery technology also face severe resource problems. From the perspective of global resource reserves, the abundance of lithium resources is insufficient (0.0065%), and the uneven distribution of lithium resources has caused local shortages. The rapid growth of lithium demand and the local shortage of lithium resources have gradually caused difficult-to-adjust contradictions. For example, the cost of battery-grade lithium carbonate has increased exponentially, and the high cost has seriously hindered the promotion and application of lithium-ion battery technology in the fields of automobiles and large-scale energy storage. Therefore, it is an important idea to achieve the comprehensive promotion of new energy technologies to build a diversified electrochemical energy storage technology map, develop an advanced energy storage battery system with rich resources and low costs, and form a situation of "complementary advantages and staggered development" with lithium-ion batteries.

[0003] Compared with the scarcity and uneven distribution of lithium resources, sodium resources are more abundant (2.83%), widely distributed, and easy to extract. The structure and working principle of sodium-ion batteries are highly similar to those of lithium-ion batteries. The key materials for the positive / negative electrodes, the industrial structure required for the production of electrolytes, and the design ideas for battery cells are highly compatible with lithium-ion batteries, and the technology conversion is relatively easy. In addition, sodium-ion batteries have a wide variety of positive electrode materials, with low dependence on resources such as nickel and cobalt. The negative electrode can use cheaper aluminum foil as the current collector, and the potential cost advantage is huge. The raw material cost of sodium-ion battery cells will be much lower than that of ternary lithium-ion batteries, and even lower than that of lithium iron phosphate batteries. Therefore, the development and promotion of sodium-ion battery technology to replace lithium-ion batteries in some application scenarios has important social and economic value.

[0004] At present, sodium-ion battery cathode materials are mainly divided into three categories: layered oxides, Prussian blue / white, and polyanionic compounds; among them, layered oxides have the advantages of low cost, high vibration / compaction density, and compatibility of production lines with lithium battery ternary cathodes, and are the most promising sodium-ion battery cathode materials for industrialization. However, sodium-ion layered oxides generally have problems such as irreversible phase change during sodium insertion / extraction, poor electrode / electrolyte interface stability, and poor air stability, which not only affect the storage of materials and the preparation of battery pole pieces, but also seriously affect battery capacity and cycle life. Summary of the invention

[0005] The purpose of the present invention is to provide a magnesium-doped sodium ion battery positive electrode material for solving the problem of charge and discharge cycle stability of the current sodium ion battery positive electrode material, so as to solve the problem that the sodium interlayer spacing of the sodium ion battery positive electrode material in the prior art is too small, which is not conducive to the transmission of sodium ions; at the same time, the present invention also provides a method for preparing the magnesium-doped sodium ion battery positive electrode material, wherein the prepared sodium ion positive electrode material has a larger interlayer spacing, which is conducive to the migration of sodium ions, and magnesium replaces the transition metal at the transition metal position to play a supporting role, and can stabilize the layered structure during the cycle process, thereby improving the cycle performance of the positive electrode material.

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

[0007] A magnesium-doped sodium-ion battery positive electrode material, characterized in that the chemical general formula of the magnesium-doped sodium-ion battery positive electrode material is: NaNi 0.6-x Fe 0.25 Mn 0.15 Mg x O 2 , where: 0 <x≤0.05。

[0008] Furthermore, the XRD spectrum of the sodium ion battery positive electrode material powder shows that it is α-NaFeO 4 Type layered structure.

[0009] Furthermore, the sodium interlayer spacing of the sodium ion battery positive electrode material is

[0010] Furthermore, the method for preparing the magnesium-doped sodium ion battery positive electrode material is characterized by comprising the following steps:

[0011] Step 1: Prepare a salt solution of manganese source, iron source, nickel source and magnesium source according to corresponding stoichiometric ratios;

[0012] Step 2: introducing the alkaline solution, ammonia solution and salt solution into the reaction kettle and stirring the reaction for 10 to 20 hours, and then obtaining the cathode material precursor by suction filtration, high temperature drying and sieving;

[0013] Step 3: After the precursor and the sodium source are evenly mixed, they are pre-sintered at a sintering temperature of 200-500° C. for 2-7 hours in a dry oxygen gas atmosphere, and then sintered at a sintering temperature of 600-1000° C. for 8-13 hours. After cooling, the mixture is sieved to obtain a magnesium-doped sodium ion battery positive electrode material.

[0014] Furthermore, in step 1, the nickel source is one or more of nickel acetate, nickel nitrate, nickel oxalate, nickel sulfate and nickel chloride; the manganese source is one or more of manganese acetate, manganese nitrate, manganese oxalate, manganese sulfate and manganese chloride; the sodium source includes but is not limited to sodium bicarbonate, sodium pyrophosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate or sodium phosphate.

[0015] Furthermore, in step 2, the introduction rate of the alkaline solution, the ammonia solution and the salt solution is 100 to 500 μL / min.

[0016] Furthermore, in step 2, the high temperature drying is performed at a temperature of 80 to 120° C. and a time of 12 to 24 hours.

[0017] Furthermore, in step 2, the alkaline solution includes but is not limited to sodium hydroxide solution, potassium hydroxide solution, and barium hydroxide solution.

[0018] At the same time, the present invention also provides an application of the above-mentioned magnesium-doped sodium ion battery positive electrode material, wherein the magnesium-doped sodium ion battery positive electrode material is used as the positive electrode active material, conductive carbon black is used as the conductive agent, and polyvinylidene fluoride is used as the binder, which are mixed in a mass ratio of 8:1:1, and an aluminum foil set is used as a fluid to form a positive electrode; glass fiber is used as a diaphragm, and a metal sodium sheet is used as a negative electrode, and the battery is assembled in an argon atmosphere glove box with an oxygen partial pressure of less than 0.1ppm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a magnesium-doped sodium ion battery positive electrode material. Magnesium is doped in the precursor preparation stage by a coprecipitation method, so that magnesium can smoothly enter the transition metal layer. In the frequent sodium intercalation and deintercalation process, the magnesium plays a role in stabilizing the layered structure, which can reduce the change of the layered structure and ensure the cycle life of the material. In addition, magnesium doping can expand the sodium interlayer spacing, facilitate the transmission of sodium ions, improve the rate performance of the material, and make the material have excellent electrochemical properties at both room temperature and low temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD spectrum of the magnesium-doped sodium ion battery positive electrode material in Example 1 of the present invention.

[0022] Figure 2 It is the XRD spectrum of the sodium ion positive electrode material in Comparative Example 1 of the present invention.

[0023] Figure 3 1 is a charge and discharge curve diagram of the magnesium-doped sodium ion battery positive electrode material in Example 1 of the present invention.

[0024] Figure 4 It is a charge and discharge curve diagram of the sodium ion positive electrode material in Comparative Example 1 of the present invention.

[0025] Figure 5 This is a cycle curve diagram of the magnesium-doped sodium ion battery positive electrode material at room temperature in Example 1 of the present invention.

[0026] Figure 6 It is a cycle curve diagram of the sodium ion positive electrode material at room temperature in Comparative Example 1 of the present invention.

[0027] Figure 7 This is a cycle curve diagram of the magnesium-doped sodium ion battery positive electrode material at low temperature in Example 1 of the present invention.

[0028] Figure 8 It is a cycle curve diagram of the sodium ion positive electrode material at low temperature in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention. All raw materials of the present invention are not particularly limited in their sources, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0030] Example 1

[0031] This embodiment provides a magnesium-doped sodium ion battery positive electrode material, a preparation method and an application thereof. The chemical formula of the magnesium-doped sodium ion battery positive electrode material is: NaNi 0.6-x Fe 0.25 Mn 0.15 Mg x O 2 , wherein: x=0.025; the magnesium-doped sodium ion battery positive electrode material is prepared by the following steps:

[0032] Step 1: manganese sulfate, nickel sulfate, iron sulfate, and magnesium sulfate are prepared into a sulfate solution with a concentration of 1 M / L according to the chemical formula of molar ratio of Ni:Fe:Mn:Mg=0.575:0.25:0.15:0.025;

[0033] Step 2: Add 0.5M / L ammonia solution into the reactor, connect the reactor to 50℃ circulating water, pass the sulfate solution prepared in step 1, 0.5M / L ammonia solution and 10M / L alkaline solution into the reactor at 250μL min-1, flush nitrogen into the reactor to prevent oxidation of the material, filter the obtained material until the pH of the filtrate is neutral, then put it into an oven at 120℃ for 24h, and after cooling, pass it through an 800-mesh sieve to obtain a cathode material precursor;

[0034] Step 3: Place the precursor and sodium hydroxide powder in a ball mill in a glove box according to the chemical formula stoichiometric molar ratio TM:Na=1:1.05, add 20 5mm ball mill beads, seal and ball mill for 3 hours to mix the materials evenly, then place the mixed material in a tubular furnace and pre-burn at 400℃ for 6 hours, then heat to 700℃ and keep warm for 12 hours, cool down and sieve with 400 mesh to obtain the positive electrode material.

[0035] The magnesium-doped sodium ion battery positive electrode material prepared in steps 1 to 3 of Example 1 is used as the positive electrode active material, conductive carbon black is used as the conductive agent, polyvinylidene fluoride is used as the binder, and they are mixed in a mass ratio of 8:1:1, and the current collector is aluminum foil to form the positive electrode; glass fiber is used as the diaphragm, and the metal sodium sheet is used as the negative electrode. The battery is assembled in an argon atmosphere glove box with an oxygen partial pressure of less than 0.1 ppm.

[0036] Example 2

[0037] This embodiment provides a magnesium-doped sodium ion battery positive electrode material, a preparation method and an application thereof. The chemical formula of the magnesium-doped sodium ion battery positive electrode material is: NaNi 0.6-x Fe 0.25 Mn 0.15 Mg x O 2 , wherein: x=0.05; the preparation process is the same as that in Example 1, the only difference is that in step 1, the molar ratio of manganese sulfate, nickel sulfate, iron sulfate and magnesium sulfate is Ni:Fe:Mn:Mg=0.55:0.25:0.15:0.05, and the other steps are exactly the same.

[0038] The magnesium-doped sodium ion battery positive electrode material prepared in Example 2 is used as the positive electrode active material, conductive carbon black is used as the conductive agent, polyvinylidene fluoride is used as the binder, and they are mixed in a mass ratio of 8:1:1. The current collector is aluminum foil to form the positive electrode; glass fiber is used as the diaphragm, and the metal sodium sheet is used as the negative electrode. The battery is assembled in an argon atmosphere glove box with an oxygen partial pressure of less than 0.1 ppm.

[0039] Comparative Example 1

[0040] This comparative example provides a sodium ion positive electrode material and a preparation method. The chemical formula of the sodium ion positive electrode material is: NaNi 0.6 Fe 0.25 Mn 0.15 O 2 The preparation process is the same as that of Example 1, except that the molar ratio of manganese sulfate, nickel sulfate and iron sulfate in step 1 is Ni:Fe:Mn=0.6:0.25:0.15, magnesium sulfate is not included, and the other steps are exactly the same.

[0041] The sodium ion battery positive electrode material prepared in Comparative Example 1 is used as the positive electrode active material, conductive carbon black is used as the conductive agent, polyvinylidene fluoride is used as the binder, and they are mixed in a mass ratio of 8:1:1. The current collector is aluminum foil to form the positive electrode; glass fiber is used as the diaphragm, and the metal sodium sheet is used as the negative electrode. The battery is assembled in an argon atmosphere glove box with an oxygen partial pressure of less than 0.1 ppm.

[0042] The above-mentioned Example 1, Example 2 and Comparative Example 1 are analyzed and tested below.

[0043] XRD test was performed on the sodium ion positive electrode materials prepared in Example 1, Example 2 and Comparative Example 1. For example, the XRD spectrum of the magnesium-doped sodium ion battery positive electrode material in Example 1 is as follows: Figure 1 As shown, the XRD spectrum of the sodium ion positive electrode material in Comparative Example 1 is as follows Figure 2 As shown in the figure, the XRD spectra of the sodium ion battery positive electrode material powder all show that it is α-NaFeO 4 Type layered structure.

[0044] In addition, the Na interlayer spacing of the sodium ion positive electrode materials prepared in Example 1, Example 2 and Comparative Example 1 is shown in Table 1. It can be seen from Table 1 that the sodium ion battery positive electrode material provided in the present application has a good Na interlayer spacing, which is conducive to the deintercalation of sodium ions from the layered structure. The layered structure of Comparative Example 1 is smaller than that of Example 1 and Example 2, indicating that magnesium is successfully incorporated into the material structure, which expands the Na interlayer spacing.

[0045] Table 1

[0046]

[0047] The sodium ion batteries obtained in Example 1, Example 2 and Comparative Example 1 were subjected to electrochemical tests, with the test interval being 2.0 to 4.0 V. The test results at room temperature are shown in Table 2, and the test results at low temperature are shown in Table 3. Exemplary: The charge and discharge curves of the magnesium-doped sodium ion battery positive electrode material in Example 1 are shown in Figure 3 As shown, the charge and discharge curve of the sodium ion positive electrode material in Comparative Example 1 is as shown Figure 4 As shown, the cycle curve of the magnesium-doped sodium ion battery positive electrode material at room temperature in Example 1 is as follows Figure 5 As shown, the cycle curve of the sodium ion positive electrode material at room temperature in Comparative Example 1 is as follows Figure 6 As shown, the cycle curve of the magnesium-doped sodium ion battery positive electrode material at low temperature in Example 1 is as follows Figure 7 As shown, the cycle curve of the sodium ion positive electrode material at low temperature in Comparative Example 1 is as follows Figure 8 shown.

[0048] Table 2

[0049]

[0050] Table 3

[0051]

[0052] It can be seen from Tables 2 and 3 that after the addition of magnesium, which is not electrochemically active during the charge and discharge process, the first discharge specific capacity of Example 1 at 0.2C at room temperature and low temperature decreases slightly, indicating that magnesium is successfully incorporated therein; the first efficiency and capacity retention rate of Example 1 at low temperature and room temperature are much higher than those of Comparative Example 1 without magnesium doping, indicating that magnesium doping stabilizes the layered structure and improves the electrochemical properties of the material; the discharge specific capacity of Example 1 at 10C at room temperature and the discharge specific capacity at 5C at low temperature are both higher than those of Comparative Example 1, indicating that magnesium doping expands the sodium interlayer spacing, facilitates the transmission of sodium ions, and can maintain a good capacity even at high rate current.

[0053] In summary, the magnesium-doped sodium ion battery positive electrode material provided by the present invention can expand the sodium interlayer spacing and stabilize the layered structure by introducing magnesium, thereby improving the cycle life and rate performance of the material at room temperature and low temperature.

[0054] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A magnesium-doped sodium ion battery positive electrode material, characterized in that: The general chemical formula of the magnesium-doped sodium-ion battery cathode material is: NaNi 0.6-x Fe 0.25 Mn 0.15 Mg x O2, of which: 0 <x≤0.05。 2. The magnesium-doped sodium ion battery positive electrode material according to claim 1, characterized in that: The sodium ion battery positive electrode material is an α-NaFeO4 type layered structure.

3. The magnesium-doped sodium ion battery positive electrode material according to claim 1, characterized in that: The sodium interlayer spacing of the sodium ion battery positive electrode material is 4. A method for preparing a magnesium-doped sodium ion battery positive electrode material, characterized in that: The following steps are involved: Step 1: Prepare a salt solution of manganese source, iron source, nickel source and magnesium source according to corresponding stoichiometric ratios; Step 2: introducing the alkaline solution, ammonia solution and salt solution into the reactor and stirring the reaction for 10 to 20 hours, and then filtering, drying at high temperature and sieving to obtain the cathode material precursor; Step 3: After the precursor and the sodium source are evenly mixed, they are pre-sintered at a sintering temperature of 200-500° C. for 2-7 hours in a dry oxygen gas atmosphere, and then sintered at a sintering temperature of 600-1000° C. for 8-13 hours. After cooling, the mixture is sieved to obtain the magnesium-doped sodium ion battery positive electrode material according to claim 1.

5. The method for preparing the magnesium-doped sodium ion battery positive electrode material according to claim 4, characterized in that: The introduction rates of the alkaline solution, ammonia solution and salt solution are all 100 μL / min to 500 μL / min.

6. The method for preparing the magnesium-doped sodium ion battery positive electrode material according to claim 4, characterized in that: The nickel source is one or more of nickel acetate, nickel nitrate, nickel oxalate, nickel sulfate and nickel chloride; the manganese source is one or more of manganese acetate, manganese nitrate, manganese oxalate, manganese sulfate and manganese chloride; the sodium source includes but is not limited to sodium bicarbonate, sodium pyrophosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate or sodium phosphate.

7. The method for preparing the magnesium-doped sodium ion battery positive electrode material according to claim 4, characterized in that: The temperature of high temperature drying is 80-120℃ and the time is 12-24h.

8. The method for preparing the magnesium-doped sodium ion battery positive electrode material according to claim 4, characterized in that: The alkaline solution includes but is not limited to sodium hydroxide solution, potassium hydroxide solution, and barium hydroxide solution.

9. Application of a magnesium-doped sodium ion battery positive electrode material in a sodium ion battery, characterized in that: The magnesium-doped sodium ion battery positive electrode material according to claim 1 is used as the positive electrode active material, conductive carbon black is used as the conductive agent, and polyvinylidene fluoride is used as the binder, which are mixed in a mass ratio of 8:1:1, and an aluminum foil set is used as a fluid to form the positive electrode; glass fiber is used as a diaphragm and a metal sodium sheet is used as a negative electrode, and the battery is assembled in an argon atmosphere glove box with an oxygen partial pressure of less than 0.1ppm.

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