Layered oxide positive electrode material of P2 / P3 mixed-phase sodium-ion battery and preparation method of layered oxide positive electrode material

Abstract

The invention discloses a P2 / P3 mixed phase layered oxide sodium ion battery positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. A positive electrode material body is a P2 / P3 mixed phase layered oxide, and the chemical formula is NaxLiyNiaMnbMcO2 (M is one or more than two of Ti, Mg, Co, Cu, Al, Sn, Zn and Li, x is more than or equal to 0.67 and less than or equal to 0.9, y is more than 0 and less than or equal to 0.05, a is more than 0 and less than or equal to 0.33, b is more than 0 and less than or equal to 0.67, c is more than 0 and less than or equal to 0.2, and a + b + c + y is equal to 1 and meets charge balance); an inorganic salt and an oxide are used as raw materials, wet ball milling, mixing and drying are performed to obtain a precursor, and then high-temperature solid-phase calcination is performed to prepare the catalyst. The problems that a pure P2-phase nickel-manganese positive electrode is small in alkali metal layer spacing and low in specific capacity under the voltage of 2.0-4.0 V are solved, the positive electrode has the advantages of P2-phase high-rate performance and P3-phase high capacity, the specific capacity can be increased to 122 mAh g <-1 > or above, circulation is stable, the preparation process is simple and convenient, mass production is easy, the positive electrode is used as a sodium-ion battery positive electrode, and technical support is provided for commercialization of the positive electrode.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, specifically relating to a P2 / P3 mixed-phase layered oxide cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, sodium-ion batteries have become an important research direction in the field of stationary energy storage due to the advantages of abundant sodium resources and low cost. The electrochemical performance of the cathode material directly affects the practical value of the battery. Among sodium-ion layered cathode materials, P2 phase nickel-manganese-based cathode materials have shown certain application potential in the conventional voltage window of 2.0–4.0V due to the synergistic effect of nickel and manganese elements and the relatively stable layered framework. However, they have a key defect of low specific capacity in this voltage range. The core reason is that the interlayer spacing of Na in the P2 phase structure is small and the stability is insufficient. During the sodium ion intercalation and deintercalation process of 2.0–4.0V, the interlayer spacing is prone to irregular shrinkage due to lattice stress, which limits the reversible intercalation of sodium ions.

[0003] To address this issue, researchers discovered that modifying the P2 / P3 mixed-phase structure through elemental doping can effectively optimize the specific capacity of P2-phase nickel-manganese cathode materials. The P3-phase layered structure has a larger interlayer spacing of Na layers, providing more ample space for sodium ions to intercalate; while the P2 phase retains good structural toughness. The mixed-phase structure formed by the two achieves a synergistic effect of "increased interlayer spacing" and "structural stability." Furthermore, doping elements (such as Ti, Al, and Mg) can regulate interlayer forces by occupying lattice sites, stabilizing the Na layer spacing of the P2 / P3 mixed phase, reducing interlayer shrinkage during sodium ion insertion / extraction, and lowering the sodium ion migration barrier. This promotes the reversible participation of more sodium ions in electrochemical reactions, thereby significantly improving the specific capacity of P2-type nickel-manganese cathode materials at 2-4V, laying the foundation for their efficient application in sodium-ion batteries. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes an innovative P2 / P3 mixed-phase layered oxide cathode material for sodium-ion batteries, along with its preparation method and applications. This material effectively incorporates elements such as lithium (Li), aluminum (Al), and cobalt (Co) into the P2 / P3 mixed-phase layered oxide cathode through a carefully designed doping ratio. The material is prepared using inorganic salts and oxides as raw materials via ball milling and a high-temperature solid-state method. Compared to traditional wet processes such as co-precipitation, this method is simpler, more efficient, and more conducive to large-scale mass production, providing solid technical support for the commercialization of sodium-ion battery cathode materials.

[0005] The above-mentioned objectives can be achieved through the following technical solutions.

[0006] A sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material with the chemical formula Na x Li y Ni a Mn b M c O2, where M is one or more of Ti, Mg, Co, Cu, Al, Sn, Zn, and Li; 0.67≤x≤0.9, 0<y≤0.05, 0<a≤0.33, 0<b≤0.67, 0<c≤0.2, a+b+c+y=1; the values ​​of x, y, a, b, and c satisfy the charge balance of the chemical formula, and the value of c is the sum of the atomic ratios of the elements in M.

[0007] This technical solution introduces a small amount of P3 phase into the P2 phase by controlling the sodium content, so that the cathode material combines the high rate performance of the P2 phase material and the high capacity of the P3 phase material, thus giving it both high specific capacity and good rate performance, as well as good cycle stability.

[0008] The method for preparing the sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material includes the following steps:

[0009] (1) According to the atomic percentage composition of the positive electrode material, each raw material is weighed by stoichiometry and mixed evenly by wet ball milling to form a slurry; the solvent in the slurry is removed by vacuum drying oven to obtain a powdered precursor; wherein: the mass ratio of grinding balls to raw materials is 1:2-1:5, the ball milling speed is 800r / min-1200r / min, the ball milling time is 12h-24h, and the solvent is anhydrous ethanol.

[0010] (2) The precursor is calcined at a constant temperature of 700℃-1000℃ for 10-15h at a heating rate of 5-10℃ / min, and then cooled to 80-150℃ in the furnace to obtain the sodium-ion battery P2 / P3 mixed phase layered oxide cathode material.

[0011] The raw materials include sodium source, lithium source, nickel source, manganese source and M source;

[0012] The sodium source includes at least one of sodium hydroxide, sodium carbonate, sodium acetate, sodium nitrate, sodium oxalate, and sodium citrate, with sodium carbonate being the preferred sodium source.

[0013] The lithium source is at least one selected from lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate; preferably, the lithium source is lithium carbonate.

[0014] The nickel source includes at least one selected from nickel oxide, nickel acetate, nickel nitrate, nickel sulfate, and nickel carbonate; preferably, the nickel source is nickel oxide.

[0015] The manganese source is at least one selected from manganese trioxide, manganese tetroxide, manganese carbonate, manganese nitrate, and manganese sulfate; preferably, the manganese source is manganese trioxide.

[0016] The M source is one or more of the following: oxide M, hydroxide M, carbonate M, sulfuric acid M, nitric acid M, and acetic acid M;

[0017] The aforementioned sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material is used as the cathode of a sodium-ion battery.

[0018] The negative electrode of the sodium-ion battery is sodium metal; the electrolyte is 1M NaClO4 in DEC:EC = 1:1 Vol% with 5% FEC; the separator is a glass fiber membrane GF-F separator.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) This invention effectively controls the interlayer spacing of Na layers by doping and inducing the formation of a P2 / P3 mixed-phase structure in sodium-ion battery cathode materials. In layered oxide cathode materials, the interlayer spacing of Na layers is crucial to the reversible insertion behavior of sodium ions. The interlayer spacing of Na layers in pure P2 phase nickel-manganese cathode materials is small, which limits the number of sodium ions inserted and the migration efficiency at a voltage of 2.0–4.0V, resulting in a low specific capacity. On the other hand, the P3 phase has interlayer structure characteristics that are more conducive to sodium ion storage. Combined with the regulating effect of doping elements (such as Ti, Al, Li, Mg, Co, etc.) on interlayer forces, the interlayer spacing of Na layers can be significantly expanded, providing more space for sodium ions to be inserted and removed. At the same time, the interlayer structure is stabilized, allowing more sodium ions to be reversibly inserted and removed in the 2-4V voltage range, thereby improving the specific capacity of the material.

[0021] (2) The P2 / P3 mixed phase structure formed by the present invention combines the advantages of both phases: the P2 phase retains good sodium ion transport kinetics characteristics, ensuring rapid sodium ion migration; the P3 phase has higher sodium ion storage potential due to the expanded interlayer spacing of the Na layers. The two phases work together, and the doping modification optimizes the electronic structure of the material, further enhancing the reversibility of the redox reaction. This results in a significant improvement in specific capacity compared to pure P2 nickel-manganese cathode material in the voltage range of 2.0 to 4.0 V (for example, the specific capacity can be increased from about 90 mAh / g of pure P2 to more than 120 mAh / g), effectively solving the problem of low capacity of pure P2 phase at this voltage.

[0022] (3) The preparation process of the present invention (such as using inorganic salts and oxides as raw materials, and then synthesizing them in a high-temperature solid phase after ball milling) is simple to operate, has excellent process stability and repeatability, can realize continuous and large-scale production, and is easy to industrialize. It provides strong technical support for the commercialization of sodium-ion battery cathode materials with high specific capacity requirements at 2-4V voltage, and has good application prospects in the field of sodium-ion batteries. Attached Figure Description

[0023] Figure 1 The XRD pattern of the target product obtained in Example 1;

[0024] Figure 2 The XRD pattern of the target product obtained in Comparative Example 1;

[0025] Figure 3 The image shows a transmission electron microscope image and mapping of the target product obtained in Example 1.

[0026] Figure 4 The image shows a transmission electron microscope image and mapping of the target product obtained in Comparative Example 1.

[0027] Figure 5 The charge-discharge curves of the target product obtained in Example 1 at a rate of 0.1C are shown.

[0028] Figure 6 The charge-discharge curves of the target product obtained in Comparative Example 1 at a rate of 0.1C are shown.

[0029] Figure 7 The target product obtained in Example 1 is shown as the cycle stability curve at a 1C rate.

[0030] Figure 8 The cycling stability curve of the target product obtained in Comparative Example 1 at 1C rate; Detailed Implementation

[0031] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0032] The purity of sodium carbonate, lithium carbonate, nickel oxide, manganese trioxide, aluminum oxide, and cobalt tetroxide used in the examples and comparative examples is not less than 99%.

[0033] Example 1:

[0034] This embodiment synthesizes a P2 / P3 mixed-phase cathode material and investigates its sodium-ion battery performance. The cathode active material is a layered metal oxide Na. 0.8 Li 0.02 Ni 0.33 Mn 0.57 Al 0.04 Co0.04 O2(a+b+c+y=1), the synthesis method is as follows:

[0035] Set 1 mol Na 0. 8Li 0.02 Ni 0.33 Mn 0.57 Al 0.04 Co 0.04 O2, in the form of Na2CO3 and Li2CO 3、 NiO, Mn2O3, Al2O3, and Co3O4 were weighed according to the molar ratio Na:Li:Ni:Mn:Al:Co = 0.8:0.02:0.33:0.57:0.04:0.04 (with Na and Li sources in 5% excess). The mixture was then dispersed in anhydrous ethanol and uniformly mixed. The mixture was then ball-milled in a ball mill at 800 r / min for 12 h. The slurry was placed in a forced-air drying oven and dried at 80℃ for 4 h to obtain the precursor. One g of the ground sample was placed in a muffle furnace and heated to 900℃ at a rate of 5℃ / min, and held at that temperature for 12 h. The sample was then cooled to 100℃ in the furnace and quickly removed to obtain a P2 / P3 biphase layered metal oxide.

[0036] The target product prepared above was mixed with Super P and the binder polyvinylidene fluoride at a mass ratio of 8:1:1, and N-methylpyrrolidone was added as a solvent. After steps such as slurry preparation, coating, and drying, a positive electrode sheet containing the target product was obtained. The prepared target product positive electrode sheet and a metallic sodium negative electrode were assembled into a sodium-ion battery, with GF / F as the battery separator and carbonate electrolyte (1M NaClO4 in DEC:EC = 1:1 Vol% with 5% FEC).

[0037] Figure 1 The image shows the XRD pattern of the target product obtained in Example 1. As can be seen from the image, the synthesized material has good crystallinity and is a P2 / P3 mixed phase structure.

[0038] Figure 3 The image shows a TEM image of the target product obtained in Example 1. As can be seen from the image, the synthesized material has a blocky morphology, with a particle size of 400-600 nm, and the doping elements are uniformly distributed in the material.

[0039] Figure 5 The target product obtained in Example 1 was subjected to a temperature of 0.1C (1C = 100 mAh g) -1 The charge-discharge curves at different rates show that the synthesized material has a high specific capacity of 122 mAh g when applied to sodium-ion batteries. -1 .

[0040] Figure 7The graph shows the cycling stability of the target product obtained in Example 1 at a 1C rate. As can be seen from the graph, the capacity retention is 85% after 300 cycles at a 1C rate.

[0041] Example 2

[0042] Set 1 mol Na 0.8 Li 0.02 Ni 0.33 Mn 0.61 Al 0.02 Co 0.02 O2 was weighed with Na2CO3, Li2CO3, NiO, Mn2O3, Al2O3, and Co3O4 in a molar ratio of Na:Li:Ni:Mn:Al:Co = 0.8:0.02:0.33:0.61:0.02:0.02 (with Na and Li sources in 5% excess). The mixture was then dispersed in anhydrous ethanol and uniformly mixed. The mixture was then ball-milled in a ball mill at 800 r / min for 12 h. The slurry was then dried in a forced-air drying oven at 80 °C for 4 h to obtain the precursor. A dried sample was ground, and 1 g of the ground sample was placed in a muffle furnace and heated to 900 °C at a heating rate of 5 °C / min, and held at that temperature for 12 h. The sample was then cooled to 100 °C in the furnace and quickly removed to obtain a P2 / P3 two-phase layered metal oxide.

[0043] The target product prepared above was mixed with Super P and the binder polyvinylidene fluoride at a mass ratio of 8:1:1, and N-methylpyrrolidone was added as a solvent. After steps such as slurry preparation, coating, and drying, a positive electrode sheet containing the target product was obtained. The prepared target product positive electrode sheet and a metallic sodium negative electrode were assembled into a sodium-ion battery, with GF / F as the battery separator and carbonate electrolyte (1M NaClO4 in DEC:EC = 1:1, Vol% with 5% FEC).

[0044] Example 3

[0045] Set 1 mol Na 0.8 Li 0.02 Ni 0.33 Mn 0.63 Al 0.01 Co 0.01O2 was weighed with Na2CO3, Li2CO3, NiO, Mn2O3, Al2O3, and Co3O4 in a molar ratio of Na:Li:Ni:Mn:Al:Co = 0.8:0.02:0.33:0.63:0.01:0.01 (with Na and Li sources in 5% excess). The mixture was then dispersed in anhydrous ethanol and uniformly mixed. The mixture was then ball-milled in a ball mill at 800 r / min for 12 h. The slurry was then dried in a forced-air drying oven at 80 °C for 4 h to obtain the precursor. A dried sample was ground, and 1 g of the ground sample was placed in a muffle furnace and heated to 900 °C at a heating rate of 5 °C / min, and held at that temperature for 12 h. The sample was then cooled to 100 °C in the furnace and quickly removed to obtain a P2 / P3 two-phase layered metal oxide.

[0046] The target product prepared above was mixed with Super P and the binder polyvinylidene fluoride at a mass ratio of 8:1:1, and N-methylpyrrolidone was added as a solvent. After steps such as slurry preparation, coating, and drying, a positive electrode sheet containing the target product was obtained. The prepared target product positive electrode sheet and a metallic sodium negative electrode were assembled into a sodium-ion battery, with GF / F as the battery separator and carbonate electrolyte (1M NaClO4 in DEC:EC = 1:1, Vol% with 5% FEC).

[0047] Comparative Example 1

[0048] Set 1 mol Na 0.8 Ni 0.33 Mn 0.67 O2, Na2CO3, NiO, and Mn2O3 were weighed according to the molar ratio Na:Ni:Mn = 0.8:0.33:0.67 (with 5% excess Na source), then dispersed in anhydrous ethanol and mixed evenly. The mixture was then placed in a ball mill jar and ball-milled at 800 r / min for 12 h. The slurry was placed in a forced-air drying oven and dried at 80 °C for 4 h to obtain the precursor. The dried sample was ground, and 1 g of the ground sample was placed in a muffle furnace and heated to 900 °C at a heating rate of 5 °C / min, and held at that temperature for 12 h. The sample was then cooled to 100 °C in the furnace and quickly removed to obtain the P2 phase layered metal oxide.

[0049] Figure 2 The figure shows the XRD pattern of the target product obtained in Comparative Example 1. As can be seen from the figure, the synthesized material has good crystallinity and is a P2 phase structure.

[0050] Figure 4 The image shows a TEM image of the target product obtained in Comparative Example 1. As can be seen from the image, the synthesized material has a blocky morphology, with particle sizes of 700-1000 nm, and the doping elements are uniformly distributed in the material.

[0051] Figure 6 The target product obtained in Comparative Example 1 was subjected to a temperature of 0.1C (1C = 100 mAh g). -1 The charge-discharge curves at different rates show that the specific capacity of the synthesized material applied to sodium-ion batteries is 87 mAh g. -1 .

[0052] Figure 8 The graph shows the cycling stability of the target product obtained in Comparative Example 1 at a 1C rate. As can be seen from the graph, the capacity retention is 81% after 300 cycles at a 1C rate.

[0053] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A P2 / P3 mixed-phase layered oxide cathode material for sodium-ion batteries, with the chemical formula Na x Li y Ni a Mn b M c O2, where, M is one or more of Ti, Mg, Co, Cu, Al, Sn, Zn, and Li; 0.67 ≤ x ≤ 0.9, 0 < y ≤ 0.05, 0 < a ≤ 0.33, 0 < b ≤ 0.67, 0 < c ≤ 0.2, a + b + c + y = 1; the values of x, y, a, b, and c satisfy the charge balance of the chemical formula, and the value of c is the sum of the atomic ratios of the elements in M.

2. The sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material according to claim 1, wherein M is one or more of Ti, Mg, Co, Cu, Al, Sn, Zn, and Li.

3. The method for preparing the sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material as described in claim 1, characterized in that: It includes the following steps: (1) Weigh the masses of each raw material according to the atomic percentage composition of the cathode material, and use wet ball milling to mix them evenly to form a slurry; then dry the slurry in a vacuum drying oven to remove the solvent, and obtain a powdery precursor; wherein: the mass ratio of the grinding balls to the raw materials is 1:2 - 1:5, the ball milling speed is 800 r / min - 1200 r / min, the ball milling time is 12 h - 24 h, and the solvent is anhydrous ethanol; (2) Heat the precursor prepared in (1) to 700°C - 1000°C at a heating rate of 5 - 10°C / min and calcine it at a constant temperature for 10 - 15 h, and then cool it to 80 - 150°C with the furnace to obtain the sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material.

4. The method for preparing the high-entropy O3 / P2 mixed-phase layered oxide cathode material for sodium-ion batteries as described in claim 3, characterized in that: The raw materials are a sodium source, a lithium source, a nickel source, a manganese source, and an M source; The sodium source includes one or more of sodium hydroxide, sodium carbonate, sodium acetate, sodium nitrate, sodium oxalate, and sodium citrate; The lithium source is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate; The nickel source includes one or more of nickel oxide, nickel acetate, nickel nitrate, nickel sulfate, and nickel carbonate; The manganese source is one or more of manganese dioxide, manganese tetroxide, manganese carbonate, manganese nitrate, and manganese sulfate; The M source is one or more of oxide M, hydroxide M, carbonate M, sulfate M, nitrate M, and acetate M.

5. The preparation method according to claim 3, characterized in that, The preparation method of the sodium-ion layered material includes: mixing the metal source precursor with the sodium source and then performing a calcination reaction to obtain the sodium-ion layered material.

6. The application of the sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material according to claim 1, wherein it is used as the cathode of a sodium-ion battery.

7. A positive electrode sheet for a sodium-ion battery, prepared from a positive electrode material, a conductive agent, a binder, and a solvent, characterized in that: The sodium-ion battery P2 / P3 mixed-phase layered oxide cathode material according to claim 4.

8. A sodium-ion battery, comprising a positive electrode, a separator, an organic electrolyte, and a negative electrode of metallic sodium, characterized in that, The positive electrode plate in the battery is the positive electrode plate of the sodium-ion battery described in claim 7.

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