Sodium transition metal oxide positive electrode material with expanded structure, preparation method and battery

Abstract

The invention discloses a sodium transition metal oxide positive electrode material with an expanded structure, a preparation method and a battery. The general formula of a sodium transition metal oxide of the positive electrode material is NaxLyNiaMnbMcNdO2, wherein 0.6 < = x < = 0.8, 0 < y < = 0.2, 0.4 > = a > = 0.1, 0.8 > = b > = 0.5, 0.1 > = c > 0, 0.1 > = d > = 0, and a + b + c + d = 1; l is an element with the same chemical valence as Na, the atomic radius of L is larger than that of Na, M is a transition metal element with the same chemical valence as Ni, and N is an inert transition metal element with the same chemical valence as Mn. According to the positive electrode material disclosed by the embodiment of the invention, a high sodium potassium (or sodium rubidium) P2 phase with a multi-element doped expanded structure is taken as a main phase, and compared with a traditional P2-phase nickel-manganese positive electrode material (Na is less than or equal to 0.67), a potassium element (or rubidium element) with a relatively large atomic radius and an expandable sodium layer structure is introduced, so that the interlayer distance of the material is increased; the structural stability of the material is ensured by multi-element doping, and the material shows higher gram volume and extremely strong rate capability in a lower voltage range.

Description

Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a sodium transition metal oxide positive electrode material with an expanded structure, a method for preparing the sodium transition metal oxide positive electrode material with an expanded structure, and a sodium ion battery. Background Art

[0002] Based on the successful application of layered lithium transition metal oxide LiTMO2, layered sodium transition metal oxide Na x TMO2 has become a hot topic in the field of sodium-ion battery research due to its high theoretical specific capacity, low cost, and easy processing. x The crystal structure of TMO2 positive electrode material mainly includes two structures: P2 and O3. The sodium ion nickel-manganese layered metal oxide with P2 structure has been widely studied as a rate-type sodium battery positive electrode material.

[0003] However, the sodium content in traditional P2 structural materials is low (Na≤0.67), and the spacing between the nickel-manganese interlayer structures is narrow. During high-rate charge and discharge, the rapid entry and exit of sodium ions makes it impossible to effectively activate and control the redox active sites of nickel, and easily induces redox reactions at the manganese sites, causing structural collapse. At the same time, the low sodium content of traditional P2 sodium-based positive electrode materials cannot meet the demand for rapid sodium ion deintercalation at high rates. Therefore, when assembled into a full battery with a hard carbon negative electrode, the energy density, rate performance and cycle performance are all poor, which makes it difficult to meet actual use needs and is not conducive to the large-scale promotion and application of P2-type sodium-based layered oxide positive electrode materials in rate-based scenarios. Summary of the invention

[0004] The present application provides a sodium transition metal oxide positive electrode material with an extended support structure, a preparation method and a sodium ion battery. The positive electrode material of the embodiment of the present application is mainly a high sodium potassium (or sodium rubidium) P2 phase with a multi-doped extended support structure. Compared with the traditional P2 phase nickel-manganese positive electrode material (Na≤0.67), a potassium element (or rubidium element) with a large atomic radius and an expandable sodium layer structure is introduced. While increasing the distance between the material layers, the multi-doping also ensures the structural stability of the material, and within a relatively low voltage range (2-3.95V), it exhibits a relatively high gram capacity and extremely strong rate performance, expanding the use scenarios of P2-type sodium positive electrode materials at high rates and long cycles. The positive electrode material of the present application has the effects of narrow voltage range, high capacity, ultra-high stability, ultra-long cycle and ultra-high rate. The prepared sodium ion battery has a relatively high specific capacity and extremely strong rate performance and cycle performance, which provides a solution for the development of new categories of rate-type and long-cycle sodium ion batteries.

[0005] In a first aspect, the present application provides a sodium transition metal oxide cathode material with a dilation structure, and the general formula of the sodium transition metal oxide of the cathode material is Na x L y Ni a Mn b M c N d O2; wherein, 0.6 ≤ x ≤ 0.8, 0 < y ≤ 0.2, 0.4 ≥ a ≥ 0.1, 0.8 ≥ b ≥ 0.5, 0.1 ≥ c > 0, 0.1 ≥ d ≥ 0, and a + b + c + d = 1; L is an element with the same valence as Na and the atomic radius of L is greater than that of Na, M is a transition metal element with the same valence as Ni, and N is an inert transition metal element with the same valence as Mn.

[0006] In a second aspect, the present application provides a preparation method of a sodium transition metal oxide cathode material with a dilation structure, including the following steps:

[0007] According to the stoichiometric ratio, nickel salt and manganese salt are mixed and dissolved in water to obtain a corresponding first transition metal salt aqueous solution. The obtained first transition metal salt aqueous solution is precipitated by the co-precipitation method, the pH value is controlled, and after spray drying, a first transition metal hydroxide precipitate precursor is obtained; according to the stoichiometric ratio, the sodium-containing compound, the first transition metal hydroxide precipitate precursor, and the L-containing compound, M-containing compound, and N-containing compound are mixed, ball-milled, tableted, and sintered to obtain the sodium transition metal oxide cathode material with a dilation structure.

[0008] In a third aspect, the present application provides another preparation method of a sodium transition metal oxide cathode material with a dilation structure, including the following steps:

[0009] According to the stoichiometric ratio, the sodium-containing compound, the nickel-containing compound, the manganese-containing compound, and the L-containing compound, M-containing compound, and N-containing compound are mixed, ball-milled, refined, tableted, and sintered to obtain the sodium transition metal oxide cathode material with a dilation structure.

[0010] In a fourth aspect, the present application provides a sodium ion battery, including a cathode material, and the cathode material includes the sodium transition metal oxide cathode material with a dilation structure described in the first aspect above or the sodium transition metal oxide cathode material with a dilation structure prepared by the preparation method described in the second aspect or the third aspect above.

[0011] The technical effects of this application are as follows: For traditional P2-phase nickel-manganese transition metal oxide cathode materials, the channels for sodium ion migration are relatively narrow, and the sodium ions mainly enter and exit the structure by means of the redox active sites and valence state changes of nickel. However, during charge and discharge at high rates, the rapid entry and exit of sodium ions can easily activate the redox active sites of manganese at the same time, resulting in changes in the valence state of manganese, leading to the occurrence of the Jahn-Teller effect, causing the rapid collapse and cyclic decay of the interlayer structure of the transition metal oxide, and inhibiting the capacity performance at high rates. Compared with the prior art, a P2-phase sodium transition metal oxide cathode material with a propped structure provided by an embodiment of this application:

[0012] In the first aspect, this propped structure design first uses a monovalent doping element with a larger atomic radius (such as K, Rb, etc.) to dope and replace some traditional Na sites to play a role in propping up the Na layer, expanding the spatial channels for sodium ions to enter and exit the Na layer, increasing the ability of Na to enter and exit quickly, and improving the rate performance of the material.

[0013] In the second aspect, this propped structure design is conducive to forming a dislocation structure to increase the movement space of Na ions. It can dope and replace some traditional nickel sites with divalent transition metal elements (such as Mg, Ca, Cu, Zn, Sr, etc.), and can also optionally dope traditional manganese sites with tetravalent inert transition metal elements (such as Ti, Zr, Si, Ge, Sn, etc.).

[0014] Compared with the prior art, a sodium transition metal oxide cathode material with a propped structure provided by an embodiment of this application expands the spatial structure of the sodium layer while introducing more Na sources; at the same time, the doping of multiple inert elements also expands the spacing of the nickel-manganese framework structure. While activating the redox active sites of nickel, it also inhibits the Jahn-Teller effect of manganese, reducing the Jahn-Teller distortion of the Mn element as a structural support point, making the overall structure less damaged during the insertion and extraction of sodium ions. While providing higher capacity and rate performance, it ensures the stability of the structure, making the material of this application have characteristics such as high capacity, ultra-long cycle life, and extremely high rate performance, providing a solution idea for the development of new types of rate-type and long-cycle sodium-ion batteries.

[0015] The preparation method of the sodium transition metal oxide cathode material with an expanded support structure provided by the embodiments of the present application can be obtained by coprecipitation combined with calcination, or by mixing, ball milling, refining, tabletting, and sintering treatment. It has the characteristics of cheap and easily available raw materials and simple preparation process. The obtained sodium transition metal oxide cathode material with an expanded support structure has a complete crystal form and high purity. In specific implementation, by adjusting the sodium content and the content of monovalent doping elements (such as K, Rb, etc.), especially controlling the total amount of monovalent elements (such as the sum of Na, K, Rb, etc. ≥ 0.67), and at the same time introducing a small amount of inert doping elements (such as the sum of divalent Mg, Ca, Cu, Zn, Sr, etc. and tetravalent Ti, Zr, Si, Ge, Sn, etc.) into the nickel-manganese framework structure to play the role of expanding the support system and stabilizing the structure; by doping elements to overall regulate the cation potential energy, a relatively pure-phase P2-type sodium-ion battery cathode material can be effectively synthesized, making the P2 phase purity in the prepared cathode material higher, thereby further increasing the structural stability, air stability, charge-discharge capacity, rate performance, and long-cycle ability of the cathode material. At the same time, during the synthesis process, by adjusting the gas flow (air / oxygen ratio) and controlling the gas flow rate, the sintering atmosphere can be maintained in a range of a relatively high air intake concentration, which can further effectively sinter a relatively pure-phase expanded support structure of P2-phase sodium transition metal oxide sodium-ion battery cathode material.

[0016] The sodium-ion battery provided by the embodiments of the present application uses the sodium transition metal oxide cathode material with an expanded support structure as the cathode material, providing a relatively high specific capacity, extremely high structural stability, and high-rate performance for the sodium-ion battery of the present application; compared with the traditional P2-phase nickel-manganese-based cathode material (Na ≤ 0.67), potassium element (or rubidium element) with a relatively large atomic radius and capable of expanding the sodium layer structure is introduced. While increasing the interlayer distance of the material, multi-element doping also ensures the structural stability of the material, and in a relatively low voltage range (2 - 3.95 V), it shows a relatively high specific capacity and extremely strong rate performance, expanding the application scenarios of P2-type sodium-ion battery cathode materials at high rates and during long cycles. The cathode material of the present application has the effects of narrow voltage range use, relatively high capacity, ultra-high stability, ultra-long cycle, and ultra-high rate. The prepared sodium-ion battery has a relatively high specific capacity, extremely strong rate performance, and cycle performance.

[0017] In order to more clearly show the technical means of the present application and ensure the smooth implementation of the content of the specification, some typical embodiments of the present application will be listed below in conjunction with the drawings and detailed descriptions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD patterns of the sodium transition metal oxide cathode material with an expanded support structure prepared in Examples 1 - 10 of the present application and the traditional nickel-manganese-based sodium transition metal oxide prepared in Comparative Example 1;

[0019] Figure 2 SEM and TEM images of the expanded sodium transition metal oxide cathode material prepared in Example 1 of this application;

[0020] Figure 3 Schematic diagram of the first charge-discharge curves of the sodium-ion half-cell assembled with the material of the expanded sodium transition metal oxide cathode material in Example 1 of this application at 2.0 - 3.95 V, 0.1 C and 5 C;

[0021] Figure 4 Schematic diagram of the first charge-discharge curves of the sodium-ion half-cell assembled with the material of the traditional nickel-manganese-based sodium transition metal oxide cathode material in Comparative Example 1 of this application at 2.0 - 3.95 V, 0.1 C and 5 C;

[0022] Figure 5 Schematic diagram of the long cycle of the sodium-ion half-cells assembled with the materials of Example 1 and Comparative Example 1 of this application at 2.0 - 3.95 V and 5 C. Detailed Description of the Invention

[0023] In order to make the invention purpose and technical solution of this application clearer and easier to understand, the content of this application will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be clear that the specific embodiments described herein are only used to explain this application and are not used to limit this application. Without departing from the spirit and essence of this application, any modification and replacement made to the methods, preparation steps or conditions of this application belong to the scope of this application.

[0024] The embodiments of this application provide an expanded sodium transition metal oxide cathode material. The sodium transition metal oxide of the cathode material has the following general formula:

[0025] Na x L y Ni a Mn b M c N d O2;

[0026] Among them, 0.6 ≤ x ≤ 0.85, 0 < y ≤ 0.2, 0.4 ≥ a ≥ 0.1, 0.8 ≥ b ≥ 0.5, 0.1 ≥ c > 0, 0.1 ≥ d ≥ 0, and a + b + c + d = 1. L is an element with the same valence as Na, and the atomic radius of L is greater than that of Na. M is an element with the same valence as Ni, and N is an element with the same valence as Mn.

[0027] For example: x is 0.6, 0.7, 0.8, 0.85, etc.; y is 0.01, 0.05, 0.1, 0.2, etc.; a is 0.1, 0.2, 0.3, 0.4, etc.; b is 0.5, 0.6, 0.7, 0.8, etc.; c is 0.01, 0.05, 0.1, etc.; d is 0, 0.01, 0.05, 0.1, etc.

[0028] Exemplarily, d can be equal to 0, that is, the sodium transition metal oxide of the positive electrode material does not contain N element. At this time, only divalent transition metal elements (such as Mg, Ca, Cu, Zn, Sr, etc.) can be doped to replace part of the traditional nickel sites, so as to form a dislocation structure to increase the migration space of Na ions. At this time, the sodium transition metal oxide of the positive electrode material has the following general formula:

[0029] Na x L y Ni a Mn b M c O2.

[0030] Among them, 0.6 ≤ x ≤ 0.85, 0 < y ≤ 0.2, 0.4 ≥ a ≥ 0.1, 0.8 ≥ b ≥ 0.5, 0.1 ≥ c > 0, a + b + c = 1.

[0031] Preferably, d is greater than 0. Thus, on the basis of being able to dope divalent transition metal elements (such as Mg, Ca, Cu, Zn, Sr, etc.) to replace part of the traditional nickel sites, tetravalent inert transition metal elements (such as Ti, Zr, Si, Ge, Sn, etc.) can also be doped to replace the traditional manganese sites, which is beneficial to forming a dislocation structure to increase the migration space of Na ions.

[0032] In some embodiments, the atomic radius of M is greater than that of Ni, and / or the atomic radius of N is greater than that of Mn. By controlling the atomic radii of M and N, it is beneficial to form more dislocation structures to increase the migration space of Na ions.

[0033] Preferably, the atomic radius of M is greater than that of Ni, and the atomic radius of N is greater than that of Mn.

[0034] Exemplarily, the atomic radius of M can be greater than that of Ni. This expanded support structure design simultaneously dopes divalent transition metal elements with larger atomic radii (such as Mg, Ca, Cu, Zn, Sr, etc.) to replace part of the traditional nickel sites, so as to further expand and activate the nickel redox channel, inhibit the manganese redox caused by the rapid redox of nickel, and improve the rate performance and cycling performance of the material.

[0035] Exemplarily, the atomic radius of N can also be greater than that of Mn. For this expanded structure design, further, a traditional manganese site is doped with a tetravalent inert transition metal element with a larger atomic radius and higher stability (such as Ti, Zr, Si, Ge, Sn, etc.), so as to further inhibit the redox change of manganese and the Jahn-Teller effect, thereby increasing the stability of the interlayer structure and improving the cycling performance of the material.

[0036] In some embodiments, L is at least one element of K and Rb, M is at least one element of Mg, Ca, Cu, Zn, and Sr, and N is at least one element of Ti, Zr, Si, Ge, and Sn.

[0037] Specifically, considering factors such as cost performance, sintering difficulty, radioactivity, and structural fusion, L is generally selected as at least one element of K and Rb, M is generally selected as at least one element of Mg, Ca, Cu, Zn, and Sr, and N is generally selected as at least one element of Ti, Zr, Si, Ge, and Sn.

[0038] In the embodiments of the present application, the sodium transition metal oxide cathode material with an expanded structure refers to the cathode material of a sodium ion battery with a main phase of P2 phase. It should be noted that the cathode material of a sodium ion battery with a main phase of P2 phase can be a pure P2 phase sodium ion battery cathode material, or a mixed phase sodium ion battery cathode material, that is, a sodium ion battery cathode material with a main phase of P2 phase but also containing P3 phase and / or O3 phase, etc., which is not specifically limited herein.

[0039] The sodium transition metal oxide cathode material with an expanded structure prepared in the embodiments of the present application has a high sodium potassium (or sodium rubidium) P2 phase with a multi-doped expanded structure as the main phase. By using multi-doping and the element stacking effect, and by controlling the value range of multiple elements, the prepared sodium transition metal oxide with an expanded structure is a P2 phase transition metal oxide layered structure. Compared with the traditional P2 phase nickel manganese-based cathode material (Na≤0.67), the material of the embodiments of the present application introduces a potassium element (or rubidium element) with a larger atomic radius and an expandable sodium layer structure. While increasing the interlayer distance of the material, multi-doping also ensures the structural stability of the material. And in a lower voltage range (2-3.95V), it exhibits a high specific capacity and extremely strong rate performance, expanding the application scenarios of P2-type sodium battery cathode materials at high rates and during long cycling. The cathode material of the present application has the effects of narrow voltage range use, high capacity, ultra-high stability, ultra-long cycling, and ultra-high rate. The prepared sodium ion battery has a high specific capacity and extremely strong rate performance and cycling performance.

[0040] In some embodiments, 0.6 ≤ x ≤ 0.75, 0 < y ≤ 0.1, 0.35 ≥ a ≥ 0.2, 0.7 ≥ b ≥ 0.55, 0.1 ≥ c > 0, 0.1 ≥ d ≥ 0. For example, x is 0.6, 0.7, 0.75, etc.; y is 0.01, 0.05, 0.1, etc.; a is 0.2, 0.3, 0.35, etc.; b is 0.55, 0.6, 0.65, 0.7, etc.; c is 0.01, 0.05, 0.1, etc.; d is 0, 0.01, 0.05, 0.1, etc.

[0041] The sodium transition metal oxide cathode material with a propping structure prepared in the embodiments of the present application can control and adjust the sodium content and the content of monovalent doping elements (such as K, Rb, etc.), especially control the total amount of monovalent elements (such as the sum of Na, K, Rb, etc. ≥ 0.67), and introduce a small amount of inert doping elements (such as the sum of divalent Mg, Ca, Cu, Zn, Sr, etc. and tetravalent Ti, Zr, Si, Ge, Sn, etc.) into the nickel-manganese framework structure to play the role of propping the system and stabilizing the structure. At the same time, the cation potential energy can be overall regulated by element doping, and a relatively pure-phase P2-type structure sodium-ion battery cathode material can be effectively synthesized, making the P2-phase purity in the prepared cathode material higher, thereby further increasing the structural stability, air stability, charge-discharge capacity, rate performance, and long cycle ability of the cathode material.

[0042] In some embodiments, (x + y) ≥ 0.67.

[0043] Specifically, this propping structure design simultaneously adopts the design principle of high sodium. While using partial monovalent doping elements (such as K, Rb, etc.) to prop open the Na layer, more Na sources are further introduced (the total amount of monovalent elements such as the sum of Na, K, Rb, etc. ≥ 0.67), enabling more Na to participate in the deintercalation and intercalation reactions at high rates, and further improving the energy retention rate and rate performance of the material of the present application at high rates.

[0044] In some embodiments, the sodium transition metal oxide may be

[0045] Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2, Na 0.7 K 0.05 Ni 0.3 Mn 0.6 Mg 0.075 Zr 0.025 O2,

[0046] Na 0.72 K 0.03 Ni0.35 Mn 0.6 Ca 0.025 Ge 0.025 O2, Na 0.6 K 0.1 Ni 0.3 Mn 0.6 Zn 0.05 Si 0.05 O2,

[0047] Na 0.6 K 0.1 Ni 0.3 Mn 0.55 Sr 0.05 Sn 0.1 O2, Na 0.65 K 0.05 Ni 0.3 Mn 0.65 Mg 0.05 ,

[0048] Na 0.65 K 0.05 Ni 0.25 Mn 0.65 Cu 0.1 , Na 0.75 K 0.05 Ni 0.2 Mn 0.6 Cu 0.1 Mg 0.1 ,

[0049] Na 0.7 Rb 0.05 Ni 0.3 Mn 0.6 Cu 0.075 Ti 0.025 O2, Na 0.6 Rb 0.02 Ni 0.28 Mn 0.7 Mg 0.02

[0050] at least one of.

[0051] Such as Figure 1 shown, Figure 1 is based on

[0052] Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2, Na 0.7 K 0.05 Ni 0.3 Mn 0.6 Mg0.075 Zr 0.025 O2,

[0053] Na 0.72 K 0.03 Ni 0.35 Mn 0.6 Ca 0.025 Ge 0.025 O2, Na 0.6 K 0.1 Ni 0.3 Mn 0.6 Zn 0.05 Si 0.05 O2,

[0054] Na 0.6 K 0.1 Ni 0.3 Mn 0.55 Sr 0.05 Sn 0.1 O2, Na 0.65 K 0.05 Ni 0.3 Mn 0.65 Mg 0.05 ,

[0055] Na 0.65 K 0.05 Ni 0.25 Mn 0.65 Cu 0.1 , Na 0.75 K 0.05 Ni 0.2 Mn 0.6 Cu 0.1 Mg 0.1 ,

[0056] Na 0.7 Rb 0.05 Ni 0.3 Mn 0.6 Cu 0.075 Ti 0.025 O2, Na 0.6 Rb 0.02 Ni 0.28 Mn 0.7 Mg 0.02 ,

[0057] For example, the XRD (X-ray diffraction) pattern has the twice of the incident angle (θ) of the X-ray (2θ, unit: degree) on the horizontal axis and the diffraction intensity (in the figure, a.u. is the abbreviation of absorbance unit) on the vertical axis; According to Figure 1It can be known that this type of sodium transition metal oxide has a P2-phase transition metal oxide layered structure and has a relatively high sodium-potassium (or sodium-rubidium) content. While maintaining a relatively high capacity, it also maintains excellent structural stability.

[0058] In some embodiments, the main phase of the cathode material is the P2 phase and further contains at least one of the P3 phase transition metal oxide and the O3 phase transition metal oxide.

[0059] It should be noted that the main phase of the cathode material prepared in the embodiments of the present application is the P2 phase and may further contain the P3 phase transition metal oxide or the O3 phase transition metal oxide, etc. For example, the cathode material may contain the P2 phase transition metal oxide and the P3 phase transition metal oxide, may also contain the P2 phase transition metal oxide and the O3 phase transition metal oxide, or may simultaneously contain the P2 phase transition metal oxide, the P3 phase transition metal oxide, and the O3 phase transition metal oxide, which is not specifically limited herein. Preferably, the nickel-manganese-based cathode material prepared in the embodiments of the present application only contains the P2 phase, which can make the P2 phase of the prepared cathode material have a higher purity, thereby further increasing the structural stability, air stability, charge-discharge capacity, rate performance, and long cycle ability of the cathode material.

[0060] The embodiments of the present application provide a preparation method for the above-expanded sodium transition metal oxide cathode material, which includes the following steps:

[0061] According to the stoichiometric ratio, nickel salt and manganese salt are mixed and dissolved in water to obtain a corresponding first transition metal salt aqueous solution. The obtained first transition metal salt aqueous solution is precipitated by the coprecipitation method, the pH value is controlled, and after spray drying, a first transition metal hydroxide precipitate precursor is obtained;

[0062] According to the stoichiometric ratio, the sodium-containing compound, the first transition metal hydroxide precipitate precursor, the L-containing compound, the M-containing compound, and the N-containing compound are mixed, ball-milled, tableted, and sintered to obtain the expanded sodium transition metal oxide cathode material.

[0063] The embodiments of the present application provide another preparation method for the above-expanded sodium transition metal oxide cathode material, which includes the following steps: According to the stoichiometric ratio, the sodium-containing compound, the nickel-containing compound, the manganese-containing compound, the L-containing compound, the M-containing compound, and the N-containing compound are mixed, ball-milled, refined, tableted, and sintered to obtain the expanded sodium transition metal oxide cathode material.

[0064] The following is a detailed explanation of this preparation method.

[0065] According to the stoichiometric ratio, mix nickel salt and manganese salt and dissolve them in water to obtain the corresponding aqueous solution of the first transition metal salt. Use the co-precipitation method to precipitate the obtained aqueous solution of the first transition metal salt, control the pH value, and obtain the first transition metal hydroxide precipitate precursor after spray drying; according to the stoichiometric ratio, mix the sodium-containing compound, the first transition metal hydroxide precipitate precursor, the L-containing compound, the M-containing compound, and the N-containing compound, and perform ball milling, tabletting, and sintering treatments to obtain the expanded sodium transition metal oxide cathode material with a supported structure.

[0066] In some embodiments, the feeding ratio of the nickel salt and the manganese salt for the co-precipitation reaction is (0.25 - 0.5):(0.5 - 1).

[0067] In some embodiments, the sodium-containing compound is at least one of sodium carbonate, sodium acetate, sodium bicarbonate, and sodium hydroxide. The nickel salt is at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate; the manganese salt is at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate; before the co-precipitation reaction, it is necessary to make the nickel salt and the manganese salt into corresponding aqueous solutions to improve the reaction efficiency of the co-precipitation reaction.

[0068] In some embodiments, when performing the co-precipitation reaction, a precipitant needs to be added to the solution, and the precipitant adjusts the pH value of the reaction system. In some embodiments, the precipitant used can be a mixed solution of sodium hydroxide and ammonia water.

[0069] In some embodiments, according to the molar ratio, sodium and L in the sodium-containing compound and the L-containing compound: nickel and manganese in the first transition metal hydroxide precipitate precursor: M and N in the M-containing compound and the N-containing compound = (0.6 - 0.85):(0.6 - 1.0):(0 - 0.2), and then perform ball milling, tabletting, and sintering treatments.

[0070] Alternatively, in some embodiments, according to the stoichiometric ratio, mix the sodium-containing compound, the nickel-containing compound, the manganese-containing compound, the L-containing compound, the M-containing compound, and the N-containing compound, and perform ball milling, refinement, tabletting, and sintering treatments to obtain the expanded sodium transition metal oxide cathode material with a supported structure.

[0071] In some embodiments, according to the molar ratio, the feeding ratio of sodium and L in the sodium-containing compound and the L-containing compound: nickel in the nickel-containing compound: manganese in the manganese-containing compound: M and N in the M-containing compound and the N-containing compound is (0.6 - 0.85):(0.1 - 0.4):(0.5 - 0.8):(0 - 0.2).

[0072] In some embodiments, the nickel-containing compound is at least one of nickelous oxide, nickel sesquioxide, nickel hydroxide, nickel carbonate, nickel oxalate; the manganese-containing compound is at least one of manganese monoxide, manganese dioxide, manganese tetroxide, manganese hydroxide, manganese carbonate, manganese oxalate; and the sodium-containing compound is at least one of sodium carbonate, sodium acetate, sodium bicarbonate, sodium hydroxide.

[0073] The L-containing compound is at least one of L-containing carbonate, acetate, bicarbonate, hydroxide; the M-containing compound is at least one of M-containing metal oxide, M-containing oxide, M-containing carbonate, M-containing hydroxide; and the N-containing compound is at least one of N-containing metal oxide, N-containing oxide, N-containing carbonate, N-containing hydroxide.

[0074] In some embodiments, when mixing the sodium-containing compound with the first transition metal hydroxide precipitation precursor and the L-containing compound, M-containing compound, and N-containing compound, or when mixing the sodium-containing compound, nickel-containing compound, manganese-containing compound, and L-containing compound, M-containing compound, and N-containing compound, mechanical grinding can be used, or they can be made into a solution, mixed and processed by ultrasonic vibration to form a slurry, and then dried and ball milled, etc. The purpose of mixing is to make the sodium-containing compound, the first transition metal hydroxide precipitation precursor, and the L-containing compound, M-containing compound, and N-containing compound mix evenly, or to make the sodium-containing compound, nickel-containing compound, manganese-containing compound, and L-containing compound, M-containing compound, and N-containing compound mix evenly, facilitating sintering into a sodium transition metal oxide cathode material with an expanded structure.

[0075] In some embodiments, the sintering conditions are to first sinter at a constant temperature of 400 - 550 °C for 1 - 5 h, then raise the temperature to 800 - 1100 °C and sinter at a constant temperature for 10 - 24 h, and the sintering atmosphere is oxygen or air or a mixed gas of oxygen and air.

[0076] The preparation method of the sodium transition metal oxide cathode material with an expanded structure provided by the embodiments of the present application can be obtained by coprecipitation combined with calcination, or by mixing, ball milling, refining, tabletting, and sintering treatment. It has the characteristics of cheap and easily available raw materials and a simple preparation process. The obtained sodium transition metal oxide cathode material with an expanded structure has a complete crystal form and high purity. At the same time, during the synthesis process, by adjusting the gas flow (air / oxygen ratio) and controlling the gas flow rate, the sintering atmosphere can be maintained within a range of a relatively high inlet gas concentration, which can effectively sinter a relatively pure-phase sodium transition metal oxide cathode material with an expanded structure, facilitating the improvement of the P2-phase purity of the cathode material.

[0077] The embodiments of the present application also provide a cathode sheet and a sodium ion battery using the above-mentioned sodium transition metal oxide cathode material with an expanded structure.

[0078] Among them, the positive electrode sheet uses a sodium transition metal oxide positive electrode material containing a dilation structure as the positive electrode active material, and also contains a conductive agent and a binder.

[0079] Specifically, the sodium transition metal oxide positive electrode material with a dilation structure is mixed with a conductive agent, a binder, and a solvent to form a positive electrode slurry, which is coated on the surface of the positive electrode current collector, and then dried, rolled, and cut into positive electrode sheets. The mass ratio of the sodium transition metal oxide positive electrode material, the conductive agent, and the binder with a dilation structure in the positive electrode sheet is 8:1:1. When preparing the positive electrode slurry, the solvent can be N-methylpyrrolidone (NMP).

[0080] The sodium-ion battery includes the above positive electrode sheet, or the positive electrode material contains the sodium transition metal oxide positive electrode material with the dilation structure of the embodiment of the present application.

[0081] In some embodiments, in the positive electrode material of the sodium-ion battery of the embodiment of the present application, in addition to containing the sodium transition metal oxide positive electrode material with the dilation structure of the present application, it may also contain at least one of the positive electrode materials with a P3-phase structure and an O3-phase positive electrode material.

[0082] In some embodiments, for the sodium-ion battery provided by the embodiment of the present application, the negative electrode material used is metallic sodium, and the electrolyte is any one of the electrolytes of 1M NaPF6 / (EC:DMC = 1:1), 1M NaPF6 / PC, and 1M NaClO4 / (EC:PC = 1:1), where EC represents ethylene carbonate, DMC represents dimethyl carbonate, PC represents propylene carbonate, EC:DMC = 1:1 represents a solvent formed by ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1, and EC:PC represents a solvent formed by ethylene carbonate and propylene carbonate in a volume ratio of 1:1.

[0083] In some embodiments, for the sodium-ion battery provided by the embodiment of the present application, the separator used is a polyolefin microporous membrane such as polyethylene and polypropylene, such as a Celgard separator.

[0084] The sodium-ion battery provided by the embodiment of the present application uses a sodium transition metal oxide cathode material with an expanded structure as the cathode substance, providing a relatively high specific capacity, good structural stability, and extremely high rate performance for the sodium-ion battery of the present application. Compared with the traditional nickel-manganese-based P2-phase cathode material, the sodium transition metal oxide cathode material with an expanded structure provided by the embodiment of the present application introduces more Na sources while expanding the sodium layer spatial structure. At the same time, the doping of multiple inert elements also expands the nickel-manganese framework structure spacing, activating the redox active sites of nickel while suppressing the Jahn-Teller effect of manganese, reducing the Jahn-Teller distortion of the Mn element as a structural support point, making the overall structure less damaged during the insertion and extraction of sodium ions. While providing higher capacity and rate performance, it ensures the structural stability, making the material of the present application have characteristics such as high capacity, long cycle life, and extremely high rate performance.

[0085] Example 1

[0086] A preparation method of a sodium transition metal oxide cathode material with an expanded structure includes the following steps:

[0087] (a) Nickel sulfate and manganese sulfate are mixed and dissolved in water at a molar ratio of 3:6 to prepare a 1.0 mol / L mixed transition metal salt solution. A mixed aqueous solution of 1.0 mol / L sodium hydroxide and 0.10 mol / L ammonia water is used as a precipitant, and the pH value is controlled to be about 8 - 10. A nickel-manganese hydroxide precursor is prepared by coprecipitation, and the obtained precursor is spray-dried to obtain a powder.

[0088] (b) Sodium carbonate, potassium carbonate, the hydroxide precursor powder obtained in step (a), copper oxide, and titanium dioxide are mixed in a molar ratio of 0.335:0.015:0.9:0.05:0.05 and added to a ball mill tank together with grinding beads of the same weight. Ball milling is carried out at a rotation speed of 200 r / min for 2 h, and the mixed powder is taken out and mixed evenly in a mortar.

[0089] (c) The powder mixed evenly in step (b) is pressed into a 20-mm-diameter disc on a cold press, with a pressure of 100 Mpa and a pressure-holding time of 5 min.

[0090] (d) The pressed sheet mixture in step (c) is placed in a tube furnace and heated to 500 °C under a mixed atmosphere of oxygen and air (mixing ratio 2:8) for isothermal sintering for 2 h, then heated to 950 °C and isothermally sintered for 20 h, and naturally cooled to room temperature to obtain Sample 1, whose molecular formula is Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2.

[0091] The obtained sample 1 was tested by XRD and SEM (Scanning Electron Microscope), and the specific test results are shown in Figure 1 and Figure 2 , and the cycle performance is shown in Table 1.

[0092] Example 2

[0093] According to the molar ratio, sodium carbonate, potassium carbonate, nickel oxide, manganese dioxide, magnesium oxide, and zinc oxide were mixed in a molar ratio of 0.35:0.025:0.3:0.6:0.075:0.025, and together with grinding beads of the same weight, they were added into a ball milling tank. At the same time, a part of ethanol was added, and high-energy ball milling was carried out at a rotation speed of 300 r / min for 8 h. The mixed powder was taken out and dried, and then mixed evenly in a mortar. Then, referring to the treatment methods of (c)-(d) in Example 1, after pressing and sintering, a sodium transition metal oxide cathode material with an expanded structure Na 0.7 K 0.05 Ni 0.3 Mn 0.6 Mg 0.075 Zr 0.025 O2 was obtained. Its XRD pattern is as shown in Figure 1 , and the cycle performance is shown in Table 1.

[0094] Example 3

[0095] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3.5:6. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor, and calcium oxide Germanium dioxide were mixed in a molar ratio of 0.36:0.015:0.95:0.025:0.025, and then according to the treatment methods of (b)-(d) in Example 1, a sodium transition metal oxide cathode material with an expanded structure Na 0.72 K 0.03 Ni 0.35 Mn 0.6 Ca 0.025 Ge 0.025 O2 was obtained. Its XRD pattern is as shown in Figure 1 , and the cycle performance is shown in Table 1.

[0096] Example 4

[0097] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3:6. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor, zinc oxide, and silicon dioxide were mixed in a molar ratio of 0.3:0.05:0.9:0.025:0.05. Then, according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure, Na 0.6 K 0.1 Ni 0.3 Mn 0.6 Zn 0.025 Si 0.05 O2, whose XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0098] Example 5

[0099] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3:5.5. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor, strontium carbonate, and tin oxide were mixed in a molar ratio of 0.3:0.05:0.85:0.05:0.1. Then, according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure, Na 0.6 K 0.1 Ni 0.3 Mn 0.55 Sr 0.05 Sn 0.1 O2, whose XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0100] Example 6

[0101] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3:6.5. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor, and magnesium oxide were mixed in a molar ratio of 0.325:0.025:0.95:0.05. Then, according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure, Na 0.65 K 0.05 Ni 0.3 Mn 0.65 Mg 0.05 , whose XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0102] Example 7

[0103] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 2.5:6.5. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor and copper oxide were mixed in a molar ratio of 0.325:0.025:0.9:0.1, and then according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure Na 0.65 K 0.05 Ni 0.25 Mn 0.65 Cu 0.1 was obtained. Its XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0104] Example 8

[0105] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3:5.5. Sodium carbonate, potassium carbonate, the prepared hydroxide precursor, copper oxide and magnesium oxide were mixed in a molar ratio of 0.375:0.025:0.8:0.1:0.1, and then according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure Na 0.75 K 0.05 Ni 0.2 Mn 0.6 Cu 0.1 Mg 0.1 was obtained. Its XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0106] Example 9

[0107] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 3:6. Sodium carbonate, rubidium carbonate, the prepared hydroxide precursor, copper oxide and titanium dioxide were mixed in a molar ratio of 0.35:0.025:0.9:0.075:0.025, and then according to the treatment methods in (b)-(d) of Example 1, a sodium transition metal oxide cathode material with an expanded structure Na 0.7 Rb 0.05 Ni 0.3 Mn 0.6 Cu 0.075 Ti 0.025 O2 was obtained. Its XRD pattern is as shown in Figure 1 and the cycling performance is shown in Table 1.

[0108] Example 10

[0109] Referring to Example 1, nickel sulfate and manganese sulfate were used to prepare a hydroxide precursor in a molar ratio of 2.8:7. Sodium carbonate, rubidium carbonate, the prepared hydroxide precursor, and magnesium oxide were mixed in a molar ratio of 0.3:0.01:0.98:0.02, and then processed according to the methods in (b)-(d) of Example 1 to obtain an expanded sodium transition metal oxide cathode material Na 0.6 Rb 0.02 Ni 0.28 Mn 0.7 Mg 0.02 , and its XRD pattern is as shown in Figure 1 , and the cycle performance is shown in Table 1.

[0110] Comparative Example 1

[0111] A nickel-manganese-based P2-type layered sodium transition metal oxide cathode material:

[0112] (a) Nickel sulfate and manganese sulfate were mixed and dissolved in water in a molar ratio of 1:2 to prepare a mixed transition metal salt solution of 1.0 mol / L nickel sulfate and manganese sulfate. A mixed aqueous solution of 1.0 mol / L sodium carbonate and 0.10 mol / L ammonia water was used as a precipitant, and the pH value was controlled at about 8.0 to prepare a nickel-manganese hydroxide precursor by coprecipitation.

[0113] (b) Sodium carbonate and the hydroxide precursor obtained in step (a) were mixed in a molar ratio of 0.335:1, added to a ball mill jar and ball mill balls, and ball milled at a rotation speed of 200 r / min for 2 h. The mixed powder was taken out and mixed evenly in a mortar.

[0114] (c) The above-mentioned uniformly mixed precursor powder was pressed into a 20-mm-diameter disc on a cold press, with a pressure of 100 Mpa and a pressure holding time of 5 min.

[0115] (d) The pressed sheet precursor in step (c) was placed in a tubular furnace and heated to 500 °C for 2 h under a mixed atmosphere of oxygen and air (mixing ratio 2:8), then heated to 950 °C and held for 20 h, and naturally cooled to room temperature to obtain a comparative example sample Na 0.67 Ni 0.33 Mn 0.67 O2, and its XRD pattern is as shown in Figure 1 .

[0116] Application Example 1

[0117] A sodium-ion battery, and its preparation method includes the following steps:

[0118] (1) Take the sample obtained in Example 1 as the positive electrode active material, mix it with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, dissolve it in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, and coat it on aluminum foil. After drying and cutting, a positive electrode sheet is obtained.

[0119] (2) Assemble the positive electrode sheet obtained in step (1) with metallic sodium and Celgard separator into a sodium-ion battery. The electrolyte of this sodium-ion battery is an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (EC:DMC = 1:1 by volume ratio). After assembly, let it stand for 24 hours, and then conduct charge-discharge activation tests on it.

[0120] Specifically, the test method is as follows: Perform three charge and discharge cycles at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95V; then perform rate performance tests on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0121] Application Example 2

[0122] A sodium-ion battery, and its preparation method includes the following steps:

[0123] (1) Take the sample obtained in Example 2 as the positive electrode active material, mix it with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, dissolve it in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, and coat it on aluminum foil. After drying and cutting, a positive electrode sheet is obtained.

[0124] (2) Assemble the positive electrode sheet obtained in step (1) with metallic sodium and Celgard separator into a sodium-ion battery. The electrolyte of this sodium-ion battery is an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (EC:DMC = 1:1 by volume ratio). After assembly, let it stand for 24 hours, and then conduct charge-discharge activation tests on it.

[0125] Specifically, the test method is as follows: Perform three charge and discharge cycles at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95V; then perform rate performance tests on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0126] Application Example 3

[0127] A sodium-ion battery, and its preparation method includes the following steps:

[0128] (1) The sample obtained in Example 3 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, which was coated on aluminum foil and dried and cut to obtain a positive electrode sheet.

[0129] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery, and the electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0130] Specifically, the test method was as follows: charging and discharging were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; afterwards, rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0131] Application Example 4

[0132] A sodium-ion battery, the preparation method thereof comprising the following steps:

[0133] (1) The sample obtained in Example 4 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, which was coated on aluminum foil and dried and cut to obtain a positive electrode sheet.

[0134] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery, and the electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0135] Specifically, the test method was as follows: charging and discharging were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; afterwards, rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0136] Application Example 5

[0137] A sodium-ion battery, the preparation method thereof comprising the following steps:

[0138] (1) The sample obtained in Example 5 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode paste. The paste was coated on aluminum foil, dried and cut to obtain a positive electrode sheet.

[0139] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery. The electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0140] Specifically, the test method was as follows: charging and discharging were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; then rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0141] Application Example 6

[0142] A sodium-ion battery, the preparation method of which comprises the following steps:

[0143] (1) The sample obtained in Example 6 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode paste. The paste was coated on aluminum foil, dried and cut to obtain a positive electrode sheet.

[0144] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery. The electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0145] Specifically, the test method was as follows: charging and discharging were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; then rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0146] Application Example 7

[0147] A sodium-ion battery, the preparation method of which comprises the following steps:

[0148] (1) Use the sample obtained in Example 7 as the positive electrode active material, mix it with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, dissolve it in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, and coat it on aluminum foil, then dry and cut to obtain a positive electrode sheet.

[0149] (2) Assemble the positive electrode sheet obtained in step (1) with metallic sodium and Celgard separator to form a sodium-ion battery. The electrolyte of this sodium-ion battery is an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, let it stand for 24 hours, and then conduct charge-discharge activation tests on it.

[0150] Specifically, the test method is as follows: perform three charge and discharge cycles at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95V; then perform rate performance tests on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0151] Application Example 8

[0152] A sodium-ion battery, the preparation method of which includes the following steps:

[0153] (1) Use the sample obtained in Example 8 as the positive electrode active material, mix it with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, dissolve it in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry, and coat it on aluminum foil, then dry and cut to obtain a positive electrode sheet.

[0154] (2) Assemble the positive electrode sheet obtained in step (1) with metallic sodium and Celgard separator to form a sodium-ion battery. The electrolyte of this sodium-ion battery is an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, let it stand for 24 hours, and then conduct charge-discharge activation tests on it.

[0155] Specifically, the test method is as follows: perform three charge and discharge cycles at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95V; then perform rate performance tests on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0156] Application Example 9

[0157] A sodium-ion battery, the preparation method of which includes the following steps:

[0158] (1) The sample obtained in Example 9 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry, which was coated on aluminum foil and dried and cut to obtain a positive electrode sheet.

[0159] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery, and the electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0160] Specifically, the test method was as follows: charge and discharge were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; then rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0161] Application Example 10

[0162] A sodium-ion battery, the preparation method of which comprises the following steps:

[0163] (1) The sample obtained in Example 10 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, and then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry, which was coated on aluminum foil and dried and cut to obtain a positive electrode sheet.

[0164] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium-ion battery, and the electrolyte of this sodium-ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0165] Specifically, the test method was as follows: charge and discharge were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95 V; then rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0166] Application Example 11

[0167] A sodium-ion battery, the preparation method of which comprises the following steps:

[0168] (1) The sample obtained in Comparative Example 1 was used as the positive electrode active material, and was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1, then dissolved in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry, which was coated on aluminum foil and dried and cut to obtain a positive electrode sheet.

[0169] (2) The positive electrode sheet obtained in step (1) was assembled with metallic sodium and a Celgard separator into a sodium ion battery, and the electrolyte of this sodium ion battery was an electrolyte mixture of 1M NaPF6 / (EC:DMC = 1:1) (in a volume ratio of EC:DMC = 1:1). After assembly, it was left standing for 24 h, and then charge-discharge activation tests were carried out on it.

[0170] Specifically, the test method was as follows: charging and discharging were carried out three times at a current density of 0.1C (1C = 100 mA / g) within a voltage range of 2.0 - 3.95V; then rate performance tests were carried out on it at 5C (1C = 100 mA / g). The results are shown in Table 1.

[0171] Figure 1 The main diffraction peaks of all samples from Example 1 to Example 10 showed a P2-type structure, and the sodium content was Na = 0.6 - 0.75, with a complete crystal form and less impurity content, proving that the obtained material was a sodium transition metal oxide positive electrode material with a P2-type expanded structure:

[0172] Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2, Na 0.7 K 0.05 Ni 0.3 Mn 0.6 Mg 0.075 Zr 0.025 O2,

[0173] Na 0.72 K 0.03 Ni 0.35 Mn 0.6 Ca 0.025 Ge 0.025 O2, Na 0.6 K 0.1 Ni 0.3 Mn 0.6 Zn 0.05 Si 0.05 O2,

[0174] Na 0.6 K 0.1 Ni 0.3 Mn 0.55 Sr0.05 Sn 0.1 O2, Na 0.65 K 0.05 Ni 0.3 Mn 0.65 Mg 0.05 ,

[0175] Na 0.65 K 0.05 Ni 0.25 Mn 0.65 Cu 0.1 , Na 0.75 K 0.05 Ni 0.2 Mn 0.6 Cu 0.1 Mg 0.1 ,

[0176] Na 0.7 Rb 0.05 Ni 0.3 Mn 0.6 Cu 0.075 Ti 0.025 O2, Na 0.6 Rb 0.02 Ni 0.28 Mn 0.7 Mg 0.02 ;

[0177] At the same time, Comparative Example 1 also shows a standard P2 crystal structure.

[0178] From Figure 2 the SEM, it can be seen that Sample 1 of Example 1 has a spherical structure. Note that Figure 2 the size marking in the lower right corner is 10 μm.

[0179] The expanded sodium transition metal oxide cathode material Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2 obtained in Example 1 was assembled with a sodium metal anode to form a sodium-ion battery and its electrochemical performance was tested. The results are as Figure 3 shown. The sodium-ion battery assembled with the sample of Example 1 had reversible initial capacities of approximately 82 mAh / g and 76 mAh / g when cycled at current densities of 0.1C (10 mA / g) and 5C (500 mA / g) in the voltage range of 2.0 - 3.95 V, respectively. Moreover, the capacity performance was within a very narrow voltage range (3.0 - 3.7 V), demonstrating excellent rate performance. In subsequent rate tests, as Figure 4As shown, during cycling at current densities of 0.1C (10 mA / g), 0.2C (20 mA / g), 0.5C (50 mA / g), 1C (100 mA / g), 2C (200 mA / g) and 5C (500 mA / g) in Example 1, the reversible initial capacities were approximately 82 mAh / g, 80 mAh / g, 79 mAh / g, 78 mAh / g, 77 mAh / g and 76 mAh / g respectively, which were significantly higher than the rate retention of Comparative Example 1 (only about 42 mAh / g at 5C); in the long cycle test, as Figure 5 shown, when cycling at 0.5C (50 mA / g), the material of Example 1 still retained a discharge specific capacity of approximately 80 mAh / g, and after 200 long cycles, the capacity retention rate was still approximately 100%, demonstrating excellent cycle stability. The reason is as follows: In Example 1 of this application, potassium element (or rubidium element) with a relatively large atomic radius and capable of expanding and supporting the sodium layer structure was introduced. This expanded structure design uses a monovalent doping element with a larger atomic radius (such as K, Rb, etc.) to dope and replace some traditional Na sites to play a role in expanding and supporting the Na layer, expanding the space channels for sodium ions to enter and exit the Na layer, increasing the ability of Na to enter and exit quickly, and improving the rate performance of the material; at the same time, this expanded structure design uses a divalent transition metal element with a larger atomic radius (such as Mg, Ca, Cu, Zn, Sr, etc.) to dope and replace some traditional nickel sites, further expanding and activating the redox channels of nickel, and suppressing the manganese redox caused by the rapid redox of nickel; further, the expanded structure of this application uses a tetravalent inert transition metal element with a larger atomic radius and greater stability (such as Ti, Zr, Si, Ge, Sn, etc.) to dope the traditional manganese sites, further suppressing the redox changes of manganese and the Jahn-Teller effect, strengthening the original nickel-manganese layer, stabilizing the expanded composite structure, and improving the rate performance and cycle performance of the material; this expanded structure design also adopts the design principle of high sodium content. While using some monovalent doping elements (such as K, Rb, etc.) to expand the Na layer, more Na sources are further introduced (the total amount of monovalent elements such as Na, K, Rb, etc. ≥ 0.67), enabling more Na to participate in the deintercalation and intercalation reactions at high rates, greatly enhancing the deintercalation ability of Na ions, and further improving the energy retention rate and rate performance of the material of this application at high rates.

[0180] In addition, Table 1 presents the materials of Examples 1-10, the charge and discharge capacity test results at 0.1C and 5C, and the rate performance test results at 5C. The results show that Examples 1-10 exhibit a relatively high high-rate discharge specific capacity and rate retention rate (energy retention rate ≥ 90% at a high rate of 5C), demonstrating extremely strong rate performance. In contrast, the material of Comparative Example 1 has poor discharge capacity and rate retention rate at high rates (the rate retention rate is only about 55% at a high rate of 5C). Therefore, the sodium transition metal oxide cathode material with a supporting structure in the embodiments of the present application overcomes the problems of poor rate performance and poor cycling of traditional P2-phase nickel-manganese-based cathode materials (Na ≤ 0.67), and exhibits a relatively high specific capacity, extremely strong rate performance, and excellent cycling stability (≈100% after 200 cycles), expanding the application scenarios of P2-type sodium battery cathode materials at high rates and under long cycling. The cathode material of the present application has the effects of being used in a narrow voltage range, having a relatively high capacity, being extremely stable, having an extremely long cycle life, and having an extremely high rate performance. The fabricated sodium-ion battery has a relatively high specific capacity, extremely strong rate performance, and cycling performance, providing a solution for the development of new types of rate-type and long-cycle sodium-ion batteries.

[0181] Table 1

[0182]

[0183]

[0184] It should be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0185] It should also be understood that the term " / and" used in the specification and appended claims of the present application refers to any combination and all possible combinations of one or more of the related listed items, and includes these combinations.

[0186] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A sodium transition metal oxide cathode material with a spreading structure, characterized in that, The sodium transition metal oxide of the positive electrode material has the general formula shown below: Na x L y Ni a Mn b M c N d O2; Where 0.6 ≤ x ≤ 0.85, 0 < y ≤ 0.2, 0.4 ≥ a ≥ 0.1, 0.8 ≥ b ≥ 0.5, 0.1 ≥ c > 0, 0.1 ≥ d ≥ 0, and a + b + c + d = 1; L is an element with the same valence as Na, and the atomic radius of L is greater than that of Na, M is a transition metal element with the same valence as Ni, and N is an inert transition metal element with the same valence as Mn.

2. The cathode material according to claim 1, wherein The atomic radius of M is greater than that of Ni, and / or the atomic radius of N is greater than that of Mn.

3. The cathode material according to claim 2, wherein L is at least one element of K, Rb, M is at least one element of Mg, Ca, Cu, Zn, Sr, and N is at least one element of Ti, Zr, Si, Ge, Sn.

4. The positive electrode material according to claim 1, characterized in that, 0.6 ≤ x ≤ 0.75, 0 < y ≤ 0.1, 0.35 ≥ a ≥ 0.2, 0.7 ≥ b ≥ 0.55, 0.1 ≥ c > 0, 0.1 ≥ d ≥ 0.

5. The cathode material according to claim 4, characterized in that, (x + y) ≥ 0.

67.

6. The cathode material according to claim 4, characterized in that, The sodium transition metal oxide is Na 0.67 K 0.03 Ni 0.3 Mn 0.6 Cu 0.05 Ti 0.05 O2, Na 0.7 K 0.05 Ni 0.3 Mn 0.6 Mg 0.075 Zr 0.025 O2, Na 0.72 K 0.03 Ni 0.35 Mn 0.6 Ca 0.025 Ge 0.025 O2, Na 0.6 K 0.1 Ni 0.3 Mn 0.6 Zn 0.05 Si 0.05 O2, Na 0.6 K 0.1 Ni 0.3 Mn 0.55 Sr 0.05 Sn 0.1 O2, Na 0.65 K 0.05 Ni 0.3 Mn 0.65 Mg 0.05 , Na 0.65 K 0.05 Ni 0.25 Mn 0.65 Cu 0.1 、Na 0.75 K 0.05 Ni 0.2 Mn 0.6 Cu 0.1 Mg 0.1 、 Na 0.7 Rb 0.05 Ni 0.3 Mn 0.6 Cu 0.075 Ti 0.025 O2, Na 0.6 Rb 0.02 Ni 0.28 Mn 0.7 Mg 0.02 at least one of 7. The cathode material according to any one of claims 1 to 6, characterized in that The main phase of the positive electrode material is the P2 phase, and it can also be at least one of the P3 phase transition metal oxide and the O3 phase transition metal oxide.

8. A method for preparing a sodium transition metal oxide cathode material with a expanding and supporting structure according to any one of claims 1 to 6, characterized in that, The preparation method includes: According to the stoichiometric ratio, nickel salt and manganese salt are mixed and dissolved in water to obtain the corresponding first transition metal salt aqueous solution. The obtained first transition metal salt aqueous solution is precipitated by the coprecipitation method, the pH value is controlled, and after spray drying, a first transition metal hydroxide precipitate precursor is obtained; according to the stoichiometric ratio, the sodium-containing compound, the first transition metal hydroxide precipitate precursor, the L-containing compound, the M-containing compound, and the N-containing compound are mixed, ball-milled, tableted, and sintered to obtain the expanded structure sodium transition metal oxide positive electrode material.

9. The preparation method according to claim 8, wherein the feeding ratio of the nickel salt and the manganese salt for the coprecipitation reaction is (0.25 - 0.5):(0.5 - 1); Sodium and L in the sodium-containing compound and the L-containing compound: nickel and manganese in the first transition metal hydroxide precipitate precursor: M and N in the M-containing compound and the N-containing compound = (0.6 - 0.85):(0.6 - 1.0):(0 - 0.2); The sintering conditions are to sinter at a constant temperature of 400 - 550 °C for 1 - 5 h first, then raise the temperature to 800 - 1100 °C and sinter at a constant temperature for 10 - 24 h, and the sintering atmosphere is oxygen or air or a mixed gas of oxygen and air.

10. The preparation method according to claim 8, characterized in that, The sodium-containing compound is at least one of sodium carbonate, sodium acetate, sodium bicarbonate, and sodium hydroxide; The nickel salt is at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate; The manganese salt is at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate; The L-containing compound is at least one of L-containing carbonate, acetate, bicarbonate, and hydroxide; The M-containing compound is at least one of M-containing metal oxide, oxide, carbonate, and hydroxide; The N-containing compound is at least one of N-containing metal oxide, oxide, carbonate, and hydroxide.

11. A method for preparing a sodium transition metal oxide cathode material with a spreading structure according to any one of claims 1 to 6, characterized in that, The preparation method includes: Mixing, ball milling, refining, tabletting, and sintering a sodium compound, a nickel compound, a manganese compound, a compound containing L, a compound containing M, and a compound containing N according to the stoichiometric ratio to obtain the sodium transition metal oxide cathode material with the expanded structure.

12. The preparation method according to claim 11, wherein According to the molar ratio, the feeding ratio of sodium and L in the sodium compound and the compound containing L: nickel in the nickel compound: manganese in the manganese compound: M and N in the compound containing M and the compound containing N is (0.6 - 0.85):(0.1 - 0.4):(0.5 - 0.8):(0 - 0.2); The sintering conditions are first constant-temperature sintering at 400 - 550 °C for 1 - 5 h, then heating to 800 - 1100 °C and constant-temperature sintering for 10 - 24 h, and the sintering atmosphere is oxygen or air or a mixed gas of oxygen and air; The nickel compound is at least one of nickel oxide, nickel sesquioxide, nickel hydroxide, nickel carbonate, and nickel oxalate; The manganese compound is at least one of manganese oxide, manganese dioxide, manganese tetroxide, manganese hydroxide, manganese carbonate, and manganese oxalate; The sodium compound is at least one of sodium carbonate, sodium acetate, sodium bicarbonate, and sodium hydroxide; The compound containing L is at least one of a carbonate containing L, an acetate containing L, a bicarbonate containing L, and a hydroxide containing L; The compound containing M is at least one of a metal oxide containing M, an oxide containing M, a carbonate containing M, and a hydroxide containing M; The compound containing N is at least one of a metal oxide containing N, an oxide containing N, a carbonate containing N, and a hydroxide containing N.

13. A sodium-ion battery, comprising a positive electrode material, characterized in that, The cathode material comprises the sodium transition metal oxide cathode material with the expanded structure according to any one of claims 1 - 7 or the sodium transition metal oxide cathode material with the expanded structure prepared by the preparation method according to any one of claims 8 - 12.

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