A sodium-ion battery positive electrode material, a preparation method thereof, a positive electrode sheet and a sodium-ion battery

Abstract

The application discloses a sodium ion battery positive electrode material and a preparation method, a positive electrode sheet and a sodium ion battery. (2 / 3+a) Ni (1 / 3‑x‑y) Cu x Mg y Mn (2 / 3‑a‑b‑c) Fe a Ti b Zr c O2, wherein x+y<1 / 3, a+b+c<2 / 3, 0 The positive electrode material has the characteristics of high capacity, good stability, good rate performance and good cycle performance, effectively plays the characteristics of the material, the application also adopts relatively cheap conventional elements, reduces the cost, improves the overall performance-price ratio of the material, and is beneficial to the popularization and application of the material in the energy storage field and the power field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a sodium ion battery positive electrode material, a preparation method thereof, a positive electrode sheet and a sodium ion battery. BACKGROUND

[0002] Compared with lithium ion batteries, sodium ion batteries have the advantages of low cost, cheap and easy-to-obtain raw materials, because they do not contain lithium, a rare metal. However, the current sodium ion positive electrode materials generally have low capacity, and the oxide-based positive electrode materials have relatively good comprehensive performance, but have low capacity, low working voltage and poor cycle performance.

[0003] Sodium ion layered oxide-based positive electrode materials are one of the core materials of sodium ion secondary batteries, and the material composition can be expressed as Na x M y O z wherein M is a transition metal element, the main working principle of which is that Na elements repeatedly deintercalate and intercalate in the form of ions in the metal layered oxide to provide charge and discharge capacity, and charge compensation in the charge and discharge process is performed through the variable valence of the transition metal M. M can be a single element such as Cu, Mg, Ni, Fe, Co, Mn and Ti, or a combination of multiple metal elements, i.e. a multi-element material. Current multi-element materials mainly focus on binary materials and ternary materials, and the research on more multi-element systems such as quaternary and quinary materials is relatively less, and often in the form of trace doping into the material. Different element types and different element combinations result in the diversity of layered oxides, and are also the fundamental reason for the performance of the material. Different elements play different roles in the material system. Due to the small number of element types, the performance cannot be considered, and the current multi-element system research is less, and the performance of the material needs to be further improved, or the developed multi-element system contains noble metals or rare metals, which limits the industrialization and popularization.

[0004] In order to solve the problem of low capacity of oxide-based sodium ion positive electrode materials, researchers have developed a series of high-capacity O3 structure sodium ion positive electrode materials. The performance of the existing material system cannot be considered, for example, the ternary material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 0.4 Fe 0.2 Mn 0.4 O2, NaNi 0.5 Fe 0.2 Mn 0.3O2, etc., such materials have high capacity, and have a discharge specific capacity of 160-190 mAh / g in a voltage range of 2.5-4.2 V, but such materials have poor stability, poor rate performance and poor cycle performance, and have high nickel content, which leads to high cost.

[0005] In order to solve the problems of poor cycle performance and poor rate performance of sodium ion cathode materials, researchers have developed a series of high-rate, long-cycle and stable P2 structure sodium ion cathode materials, but the initial charge capacity of the P2 structure is low, and the average voltage is less than 3.2 V, and when charged to a higher voltage, the P2 structure will undergo a phase transition to O2 or OP4 / Z', which will lead to a decrease in cycle stability. For example, Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, Na 2 / 3 Cu 1 / 3 Mn 2 / 3 O2, etc., such materials are commonly binary, and the main disadvantage is that the capacity is small, but the problem of how to improve the overall performance and further improve the performance-price ratio still exists. In addition, the P2 structure of the pure nickel-manganese binary system has good cycle and rate performance, but the discharge specific capacity of the material is low, which limits the practical application of the material.

[0006] Therefore, in order to improve the stability, rate and cycle performance of sodium ion cathode materials, and reduce the cost of raw materials, it is necessary to provide a technical solution to solve the above problems. SUMMARY

[0007] The purpose of the present application is to provide a sodium ion battery cathode material, which corrects the sodium element and performs multi-element doping, and uses relatively inexpensive conventional elements, which not only improves the rate performance and cycle performance of the cathode material, but also reduces the cost and improves the overall performance-price ratio of the material.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A sodium ion battery cathode material, the chemical formula of the sodium ion battery cathode material is Na (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, wherein x+y<1 / 3, a+b+c<2 / 3, 0

[0010] Preferably, the sodium ion battery positive electrode material has a sodium element content satisfying the relationship: 0.677 < 2 / 3 + a < 0.757, and the positive electrode material has a P2 phase structure.

[0011] The application further provides a preparation method of the sodium ion battery positive electrode material. (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, and the method comprises the steps of mixing, calcining and crushing the elements to obtain the sodium ion battery positive electrode material.

[0012] Preferably, the sodium source is at least one of sodium carbonate, sodium bicarbonate and sodium hydroxide; the nickel source is at least one of nickel protoxide and nickel hydroxide; the copper source is at least one of copper oxide, cuprous oxide and copper carbonate; the magnesium source is at least one of magnesium carbonate and magnesium hydroxide; the manganese source is at least one of trimanganese tetroxide, dimanganese trioxide and manganese dioxide; the iron source is at least one of magnetite and wustite; the titanium source is titanium dioxide; and the zirconium source is zirconium dioxide.

[0013] Preferably, the calcination temperature is 800-1100 DEG C, and more preferably, the calcination temperature is 900-1000 DEG C.

[0014] Preferably, the calcination time is 10-24 hours, and more preferably, the calcination time is 15-24 hours.

[0015] The application further provides a positive electrode sheet comprising the sodium ion battery positive electrode material.

[0016] The application further provides a sodium ion battery comprising a positive electrode sheet, a negative electrode sheet and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet.

[0017] Compared with the prior art, the application has at least the following beneficial effects:

[0018] (1) The positive electrode material has the characteristics of high capacity, good stability, high rate performance and cycle performance, effectively plays the characteristics of the material, and the application further adopts conventional elements which are relatively inexpensive, thereby reducing the cost and improving the overall performance-price ratio of the material.

[0019] (2) The positive electrode material of the application has good air stability, which is specifically manifested in that the material can still maintain a low pH value, pH < 12, after long-term exposure to air.

[0020] (3) Compared with conventional sodium ion positive electrode materials, the positive electrode material of the application has better rate performance and long cycle performance, and the long cycle performance is conducive to the popularization and application of the material in the energy storage field, and the high rate is conducive to the application of the material in the power field. DETAILED DESCRIPTION

[0021] In order to make the technical solutions and advantages of the application clearer, the technical solutions of the application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0022] In the first aspect according to the application, the application provides a sodium ion battery positive electrode material, and the chemical formula of the sodium ion battery positive electrode material is Na (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, wherein x+y < 1 / 3, a+b+c < 2 / 3, 0 < a < 0.1, 0 < c < 0.1, x > 0, y > 0, a > 0, and b > 0.

[0023] The sodium ion battery positive electrode material of the application has a synergistic effect between various elements, and the lack of one of the elements will affect the electrochemical performance of the sodium ion battery. The sodium ion battery positive electrode material uses relatively inexpensive conventional elements, which is conducive to reducing the cost and improving the overall performance-price ratio of the material.

[0024] The sodium ion positive electrode material of the application has a surface pH < 12 after long-term exposure to air, and a low pH value indicates that the material has good stability. The main reason for the good stability of the positive electrode material is the synergistic effect of multiple elements, which overcomes the problem of poor structural stability of binary materials and ternary materials.

[0025] In an embodiment according to the present application, the content of sodium element in the sodium ion battery positive electrode material satisfies the relationship: 0.677 < 2 / 3 + a < 0.757, and the positive electrode material is a P2 phase structure. When the content of sodium element is within the above range, the sodium ion battery positive electrode material can better maintain electrical neutrality, thereby not hindering the redox reaction of the sodium ion battery positive electrode material, and satisfying the normal sodium ion accommodation of such material. The content of sodium element in the above range is 3% excessive, which is to compensate for the volatilization amount of sodium element in the calcination process, so as to ensure that the sodium element can better be repeatedly deintercalated and intercalated in the form of ions in the positive electrode material, thereby improving the charge and discharge capacity of the positive electrode material.

[0026] The present application expands the sodium ion interlayer spacing by utilizing the doping of multiple elements, which plays a certain supporting role when cycling, so that the transmission coefficient of sodium ions in the positive electrode material is significantly improved, and the P2-O2 phase transition is inhibited, thereby improving the stability of the material when cycling.

[0027] In the second aspect according to the present application, the present application further provides a preparation method of the above-mentioned sodium ion battery positive electrode material, which comprises the following steps: mixing sodium source, nickel source, copper source, magnesium source, manganese source, iron source, titanium source and zirconium source according to the content ratio of each element of the chemical formula Na (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, calcining, and crushing, to obtain the sodium ion battery positive electrode material.

[0028] In an embodiment according to the present application, the sodium source is at least one of sodium carbonate, sodium bicarbonate and sodium hydroxide, preferably sodium carbonate; the nickel source is at least one of nickel protoxide and nickel hydroxide, preferably nickel hydroxide; the copper source is at least one of copper oxide, cuprous oxide and copper carbonate, preferably copper oxide; the magnesium source is at least one of magnesium carbonate and magnesium hydroxide, preferably magnesium hydroxide; the manganese source is at least one of trimanganese tetroxide, dimanganese trioxide and manganese dioxide, preferably manganese dioxide; the iron source is at least one of triiron tetroxide and diiron trioxide, preferably diiron trioxide; the titanium source is titanium dioxide; and the zirconium source is zirconium dioxide.

[0029] In an embodiment according to the present application, the calcination temperature is 800-1100°C, preferably 900-1000°C. Specifically, the calcination temperature can be 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C or 1100°C. When the calcination temperature is controlled within the above range, the uniformity of the sodium ion battery positive electrode material obtained by calcination is better. If the calcination temperature is too high, the particles will be too large, which will increase the difficulty of reduction.

[0030] In an embodiment according to the present application, the calcination time is 10-24h, preferably 15-24h. Specifically, it can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h. When the calcination time is controlled within the above range, better fusion between raw materials can be ensured, and the obtained sodium-ion battery cathode material has better uniformity.

[0031] In a third aspect according to the present application, the present application further provides a cathode sheet comprising the above-mentioned sodium-ion battery cathode material.

[0032] In a fourth aspect according to the present application, the present application further provides a sodium-ion battery comprising a cathode sheet, an anode sheet and a separator interposed between the cathode sheet and the anode sheet, wherein the cathode sheet is the above-mentioned cathode sheet.

[0033] The separator can be selected from various separators known to those skilled in the art for use in sodium-ion batteries, such as polypropylene microporous membrane, polyethylene felt, glass fiber felt or ultra-fine glass fiber paper.

[0034] The sodium-ion battery provided by the present application further comprises an electrolyte, which is composed of an organic solvent and an electrolyte sodium salt. The organic solvent can be selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and methyl tert-butyl ether; and the electrolyte sodium salt can be selected from one or more of sodium hexafluorophosphate, sodium bisfluorosulfonylimide, sodium bis(trifluoromethanesulfonyl)imide, sodium triflate, sodium tetrafluoroborate, sodium difluorophosphate and sodium perchlorate.

[0035] The present application will be further described below through specific examples.

[0036] Example 1

[0037] The preparation steps of the sodium-ion battery cathode material of the present example are as follows: sodium carbonate, nickel hydroxide, copper oxide, magnesium carbonate, manganese dioxide, diiron trioxide, titanium dioxide and zirconium dioxide are weighed according to the content ratio of each element in the chemical formula Na 0.677 Ni 0.313 Cu 0.01 Mg 0.01 Mn 0.637 Fe 0.01 Ti 0.01 Zr 0.01 O2, mixed and calcined at 900℃ for 15h to obtain a sodium-ion battery cathode material Na0.677 Ni 0.313 Cu 0.01 Mg 0.01 Mn 0.637 Fe 0.01 Ti 0.01 Zr 0.01 O2.

[0038] In the batching process, the sodium element content in sodium carbonate is excessive by 3%, so as to compensate for the volatilization amount of sodium element during high-temperature calcination.

[0039] Example 2

[0040] The preparation steps of the sodium ion battery positive electrode material of the embodiment are as follows: sodium carbonate, nickel hydroxide, copper oxide, magnesium carbonate, manganese dioxide, diiron trioxide, titanium dioxide, and zirconium dioxide are weighed according to the element content ratio in the chemical formula Na 0.757 Ni 0.153 Cu 0.09 Mg 0.09 Mn 0.397 Fe 0.09 Ti 0.09 Zr 0.09 O2, and then mixed and calcined at 800 DEG C for 24 h to obtain the sodium ion battery positive electrode material Na 0.757 Ni 0.153 Cu 0.09 Mg 0.09 Mn 0.397 Fe 0.09 Ti 0.09 Zr 0.09 O2.

[0041] In the batching process, the sodium element content in sodium carbonate is excessive by 3%, so as to compensate for the volatilization amount of sodium element during high-temperature calcination.

[0042] Example 3

[0043] The preparation steps of the sodium ion battery positive electrode material of the embodiment are as follows: sodium carbonate, nickel hydroxide, copper oxide, magnesium carbonate, manganese dioxide, diiron trioxide, titanium dioxide, and zirconium dioxide are weighed according to the element content ratio in the chemical formula Na 0.717 Ni 0.323 Cu 0.05 Mg 0.05 Mn 0.517 Fe 0.05 Ti 0.05 Zr 0.05 O2, and then mixed and calcined at 1000 DEG C for 10 h to obtain the sodium ion battery positive electrode material Na 0.717 Ni 0.323 Cu 0.05 Mg0.05 Mn 0.517 Fe 0.05 Ti 0.05 Zr 0.05 O2.

[0044] In the batching process, the sodium element content in sodium carbonate is excessive by 3%, so as to compensate for the volatilization amount of sodium element during high-temperature calcination.

[0045] Comparative Example 1

[0046] The difference between the present comparative example and Example 1 is that the present comparative example does not dope copper source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.677 Ni 0.323 Mg 0.01 Mn 0.637 Fe 0.01 Ti 0.01 Zr 0.01 O2.

[0047] Comparative Example 2

[0048] The difference between the present comparative example and Example 1 is that the present comparative example does not dope magnesium source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.677 Ni 0.323 Cu 0.01 Mn 0.637 Fe 0.01 Ti 0.01 Zr 0.01 O2.

[0049] Comparative Example 3

[0050] The difference between the present comparative example and Example 1 is that the present comparative example does not dope iron source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.667 Ni 0.313 Cu 0.01 Mg 0.01 Mn 0.647 Ti 0.01 Zr 0.01 O2.

[0051] Comparative Example 4

[0052] The difference between the present comparative example and Example 1 is that the present comparative example does not dope titanium source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.677 Ni 0.313 Cu 0.01 Mg 0.01 Mn 0.647 Fe 0.01 Zr 0.01 O2.

[0053] Comparative Example 5

[0054] The difference between this comparative example and Example 1 is that this comparative example does not dope a zirconium source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.677 Ni 0.313 Cu 0.01 Mg 0.01 Mn 0.637 Fe 0.01 Ti 0.01 O2.

[0055] Comparative Example 6

[0056] The difference between this comparative example and Example 1 is that this comparative example does not dope a copper source, a magnesium source, a titanium source, a zirconium source, and the chemical formula of the obtained sodium ion battery positive electrode material is Na 0.667 Ni 0.333 Mn 0.667 O2.

[0057] The pH of the sodium ion battery positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-6 was measured after the materials were exposed to air for 24 hours, and the prepared positive electrode materials were used in positive electrode sheets, and the positive electrode sheets were used in sodium ion batteries, the capacity of the sodium ion batteries was tested at a voltage of 2.5-4.2 V, and the rate performance test was carried out at 1C / 0.1C, and the 100-week charge-discharge cycle was carried out at 1C, and the performance test results are shown in Table 2. The content of each element in the positive electrode materials of Examples 1-3 and Comparative Examples 1-6 is shown in Table 1:

[0058] Table 1

[0059] No. Na Ni Cu Mg Mn Fe Ti Zr Example 1 2 / 3+0.01 1 / 3-0.02 0.01 0.01 2 / 3-0.03 0.01 0.01 0.01 Example 2 2 / 3+0.09 1 / 3-0.18 0.09 0.09 2 / 3-0.27 0.09 0.09 0.09 Example 3 2 / 3+0.05 1 / 3-0.1 0.05 0.05 2 / 3-0.15 0.05 0.05 0.05 Comparative Example 1 2 / 3+0.01 1 / 3-0.01 0 0.01 2 / 3-0.03 0.01 0.01 0.01 Comparative Example 2 2 / 3+0.01 1 / 3-0.01 0.01 0 2 / 3-0.03 0.01 0.01 0.01 Comparative Example 3 2 / 3+0 1 / 3-0.02 0.01 0.01 2 / 3-0.02 0 0.01 0.01 Comparative Example 4 2 / 3+0.01 1 / 3-0.02 0.01 0.01 2 / 3-0.02 0.01 0 0.01 Comparative Example 5 2 / 3+0.01 1 / 3-0.02 0.01 0.01 2 / 3-0.02 0.01 0.01 0 Comparative Example 6 2 / 3+0 1 / 3-0 0 0 2 / 3-0 0 0 0

[0060] Table 2

[0061]

[0062] From the test results of Table 2, it can be seen that the sodium ion battery positive electrode material of the present application is used in a sodium ion battery, the sodium ion battery is tested for performance at a voltage of 2.5-4.2V 0.1C, the capacity of the sodium ion battery of Examples 1-3 is 91mAh / g, 91mAh / g, 92mAh / g respectively, 1C / 0.1C≥0.95, after 100 cycles of charging and discharging at 1C, the capacity retention rate is greater than 95%, and the surface pH of the sodium ion battery positive electrode material of the present application is less than 12 after being exposed to air for 24 hours. It can be seen that the residual alkali content on the surface of the sodium ion battery positive electrode material of the present application is low, it has good stability in air, when it is used in a sodium ion battery, it has high capacity, not only improves the rate performance, but also improves the cycle performance. Further, in Example 3, when the content of sodium element is the intermediate value, the capacity, rate performance and cycle performance are the best, which is the best ratio of each element in the sodium ion battery positive electrode material of the present application.

[0063] Compared with the test results of Comparative Examples 1-6, the capacity, rate performance and cycle performance of Comparative Example 1-5 are all decreased after doping one element, and the surface residual alkali content of the positive electrode material obtained is also higher. Therefore, the elements in the present application have a synergistic effect, and the lack of one of the elements will affect the electrochemical performance of the sodium ion battery. Further, in Comparative Example 6, only nickel and manganese elements are doped, i.e. a binary system of pure nickel and manganese P2 structure, although the cycle and rate performance is good, the specific discharge capacity of the material is low, which limits the practical application of the material, the content of pure nickel is high, which increases the cost, and the surface pH of the material is 12.5 after being exposed to air for 24 hours, which shows that it is easy to react with carbon dioxide and water in the air for a long time, increasing the residual alkali content. The existence of residual alkali reduces the actual capacity of the material and the electrical conductivity of the material.

[0064] In summary, the sodium ion battery positive electrode material of the present application has the characteristics of high capacity, good stability, good rate performance and cycle performance, effectively plays the characteristics of the material, the present application also uses relatively inexpensive conventional elements, reduces the cost, improves the overall performance-price ratio of the material, and is conducive to the popularization and application of the material in the field of energy storage and power.

[0065] Based on the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art based on the present application shall fall within the scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.

Claims

1. A sodium-ion battery cathode material, characterized in that, The chemical formula of the sodium ion battery cathode material is Na (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, wherein x+y<1 / 3, a+b+c<2 / 3, 0 The sodium ion battery cathode material has a P2 phase structure.

2. A method of preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The steps include: mixing, calcining and crushing the sodium source, nickel source, copper source, magnesium source, manganese source, iron source, titanium source and zirconium source according to the element content ratio of the chemical formula Na (2 / 3+a) Ni (1 / 3-x-y) Cu x Mg y Mn (2 / 3-a-b-c) Fe a Ti b Zr c O2, to obtain a sodium ion battery positive electrode material.

3. The method for preparing the sodium-ion battery cathode material according to claim 2, characterized in that, The sodium source is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide; the nickel source is at least one of nickel protoxide and nickel hydroxide; the copper source is at least one of copper oxide, copper protoxide, and copper carbonate; the magnesium source is at least one of magnesium carbonate and magnesium hydroxide; the manganese source is at least one of trimanganese tetraoxide, dimanganese trioxide, and manganese dioxide; the iron source is at least one of triiron tetroxide and diiron trioxide; the titanium source is titanium dioxide; and the zirconium source is zirconium dioxide.

4. The method for preparing the sodium-ion battery cathode material according to claim 2, characterized in that, The temperature of the calcination is 800-1100℃.

5. The method for preparing the sodium-ion battery cathode material according to claim 4, characterized in that, The temperature of the calcination is 900-1000℃.

6. The method for preparing the sodium-ion battery cathode material according to claim 2, characterized in that, The time of the calcination is 10-24h.

7. The method for preparing the sodium-ion battery cathode material according to claim 6, characterized in that, The time of the calcination is 15-24h.

8. A positive electrode sheet characterized by comprising: The sodium-ion battery cathode material of claim 1.

9. A sodium-ion battery, characterized in that, The sodium-ion battery cathode material of claim 1. The sodium-ion battery cathode material of claim 1.

Images