Preparation method of Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material

Abstract

The present invention relates to a method for preparing a positive electrode material for a sodium ion battery of a P2-type layered oxide doped with Li and Cu, belonging to the technical field of sodium ion batteries. 0.66 Ni a Li b Cu c Mn d O2; wherein 0.1≤a≤0.14, 0.03≤b≤0.07, 0.08≤c≤0.12, and 0.70≤d≤0.74. The present invention uses NiC4H6O4·4H2O, MnC4H6O4·4H2O, and Na2CO3 as raw materials to prepare a carbonate precursor. The carbonate precursor, Na2CO3, Li2CO3, and CuO are ball-milled and mixed, followed by calcination to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material. The Li and Cu dual-element doped P2-type layered oxide material of the present invention, as a positive electrode for a sodium ion battery, exhibits excellent rate capability and good cycle performance.

Description

Technical Field

[0001] The invention relates to a preparation method of a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, belonging to the technical field of sodium ion batteries. Background Art

[0002] Sodium metal has similar physical and chemical properties to lithium metal. Compared with the natural reserves of lithium resources (0.0017wt%) in the earth's crust, the natural reserves of sodium resources (2.36wt%) are abundant and widely distributed. In addition, Na + / Na(-2.71V) and Li + / Li (-3.04V) has a similar standard electrode potential; secondly, Na + The Stokes radius is smaller than Li + ions, giving it higher conductivity; finally, sodium-ion batteries can use aluminum foil as a current collector, which is cheaper than the copper foil used in lithium-ion batteries, which is conducive to commercialization. Therefore, in large-scale energy storage systems, sodium-ion batteries are most likely to replace lithium-ion batteries and become the next generation of commercial secondary rechargeable batteries. However, since the ionic radius of sodium ions (r = 0.113nm) is larger than the ionic radius of lithium ions (r = 0.076nm), the slow reaction kinetics and Na + The large volume change during the extraction / intercalation process limits its cycle performance and rate performance, so it is crucial to develop suitable sodium-ion battery positive electrode materials.

[0003] At present, the most likely cathode material for sodium-ion batteries to be commercialized is layered oxide. The most commonly used crystal structures in layered oxides are O3 and P2 phases. O3-type layered oxides have a high theoretical capacity, but due to the complex phase transitions that occur during the charge and discharge process, the structure is unstable, resulting in low reversible capacity and poor cycle capacity retention. Compared with O3-type layered oxides, P2-type layered metal oxides allow Na + Direct migration through the adjacent triangular prism Na site, resulting in faster Na + However, the sodium-deficient P2 phase limits its capacity, and during the charge and discharge process, phase transitions easily occur in the high voltage region, causing volume and stress changes, affecting the stability of the electrode material structure and resulting in poor rate and cycle performance. Summary of the Invention

[0004] Aiming at the technical problems of poor rate performance and cycle performance in the positive electrode materials of sodium ion batteries, the present invention proposes a preparation method of a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material. The chemical formula of the layered oxide of the present invention is Na0.66 Ni a Li b Cu c Mn d O2; wherein 0.1≤a≤0.14, 0.03≤b≤0.07, 0.08≤c≤0.12, and 0.70≤d≤0.74. The present invention uses NiC4H6O4·4H2O, MnC4H6O4·4H2O, and Na2CO3 as raw materials to prepare a carbonate precursor. The carbonate precursor, Na2CO3, Li2CO3, and CuO are ball-milled and mixed, followed by calcination to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material. The Li and Cu dual-element doped P2-type layered oxide material of the present invention, as a positive electrode for a sodium ion battery, exhibits excellent rate capability and good cycle performance.

[0005] A preparation method of a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, wherein the layered oxide has the chemical formula Na 0.66 Ni a Li b Cu c Mn d O2; where 0.1≤a≤0.14, 0.03≤b≤0.07, 0.08≤c≤0.12, 0.70≤d≤0.74;

[0006] The specific steps of the preparation method are as follows:

[0007] (1) Dissolve NiC4H6O4·4H2O and MnC4H6O4·4H2O in deionized water to obtain solution A;

[0008] (2) dissolving Na2CO3 in deionized water to obtain solution B, and adding solution B to solution A and mixing evenly to obtain solution C;

[0009] (3) Solution C is reacted at a temperature of 20-30°C for 10-14 hours, the solid-liquid separation is carried out, the solid is washed with deionized water and ethanol, and dried to obtain a carbonate precursor;

[0010] (4) mixing the carbonate precursor, Na2CO3, Li2CO3 and CuO and ball milling for 8-16 h to obtain powder D;

[0011] (5) Powder D is calcined at a temperature of 400-600°C for 8-12 hours, then the temperature is uniformly increased to a temperature of 800-1000°C and calcined at a constant temperature for 10-14 hours to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material.

[0012] Preferably, in step (1), the solid-to-liquid ratio of NiC4H6O4·4H2O, MnC4H6O4·4H2O and deionized water in mmol:mmol:mL is 10-14:70-74:80-88.

[0013] Preferably, in step (2), the solid-liquid ratio of Na2CO3 to deionized water is 80-88:80-88 in mmol:mL.

[0014] Preferably, the molar ratio of the carbonate precursor, Na2CO3, Li2CO3 and CuO in step (4) is 10:3.5:0.15~0.35:0.8~1.2.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention dopes Li and Cu into the bulk structure of the material, utilizing their synergistic effect to suppress the unfavorable P2-O2 phase transition and the irreversible oxygen redox and transition metal migration and dissolution, thereby improving the material's cycle performance and rate performance;

[0017] (2) The Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material of the present invention has good cycle performance. -1 ) current density, its first discharge capacity reached 113.5 mAh g -1 , after 100 cycles, the capacity retention rate is 65.61%, which has high cycle stability;

[0018] (3) The Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material of the present invention has a large interplanar spacing and a low diffusion energy barrier, providing a fast diffusion channel for ion migration, thereby achieving excellent rate performance. At a high current density of 5C, its discharge capacity reaches 80.1mAhg -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of the Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material in Example 2;

[0020] Figure 2 This is an SEM image of the Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material of Example 2;

[0021] Figure 3 This is the charge and discharge curve of the Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material in Example 2;

[0022] Figure 4This is the cycle performance curve of the sodium ion battery in Example 2;

[0023] Figure 5 The figure shows the cycle performance curves of the sodium ion battery of Example 2 at different rates. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0025] Example 1: The chemical formula of the layered oxide in this example is Na 0.66 Ni a Li b Cu c Mn d O2; wherein a=0.10, b=0.03, c=0.08, d=0.70;

[0026] A method for preparing a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, comprising the following steps:

[0027] (1) Dissolve 10 mmol of NiC4H6O4·4H2O and 70 mmol of MnC4H6O4·4H2O in 80 mL of deionized water to obtain solution A;

[0028] (2) 80 mmol of Na2CO3 was dissolved in 80 mL of deionized water to obtain solution B. At room temperature, solution B was added to solution A and mixed evenly to obtain solution C;

[0029] (3) Solution C was reacted at 20°C for 10 h, solid-liquid separation was performed, and the solid was washed three times with deionized water and ethanol, and dried at 80°C to obtain a carbonate precursor (Ni 0.10 Mn 0.70 CO3);

[0030] (4) 10 mmol carbonate precursor, 3.5 mmol Na2CO3, 0.15 mmol Li2CO3 and 0.8 mmol CuO were mixed and ball-milled for 8 h to obtain powder D;

[0031] (5) Powder D was calcined at 400°C for 8 h, then the temperature was uniformly raised to 800°C and calcined at a constant temperature for 10 h to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material;

[0032] The Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material of this embodiment has a large interplanar spacing and a low diffusion energy barrier, providing a fast diffusion channel for ion migration, thereby improving ion mobility and quantity;

[0033] A sodium ion battery comprising a positive electrode, a negative electrode, a separator (glass fiber), and an electrolyte, wherein the positive electrode comprises a positive electrode current collector aluminum foil and a positive electrode material layer coated on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent (SP), and a binder (PVDF), wherein the positive electrode active material is a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material; in terms of mass percentage, the positive electrode active material (Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material) accounts for 80%, the conductive agent (SP) accounts for 10%, and the binder (PVDF) accounts for 10% in the positive electrode material layer;

[0034] At a current density of 0.1C, the first discharge capacity of the sodium-ion battery reached 102 mAh g -1 The capacity retention rate is 55% after 100 cycles, which shows high cycle stability. The larger interplanar spacing in the material structure provides a channel for rapid diffusion of ions, thereby improving the ion mobility and quantity.

[0035] Example 2: The chemical formula of the layered oxide in this example is Na 0.66 Ni a Li b Cu c Mn d O2; wherein a=0.12, b=0.05, c=0.10, d=0.72;

[0036] A method for preparing a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, comprising the following steps:

[0037] (1) Dissolve 12 mmol of NiC4H6O4·4H2O and 72 mmol of MnC4H6O4·4H2O in 84 mL of deionized water to obtain solution A;

[0038] (2) 84 mmol of Na2CO3 was dissolved in 84 mL of deionized water to obtain solution B. At room temperature, solution B was added to solution A and mixed evenly to obtain solution C;

[0039] (3) Solution C was reacted at 25°C for 12 h, solid-liquid separation was performed, and the solid was washed three times with deionized water and ethanol, and dried at 80°C to obtain a carbonate precursor (Ni 0.12 Mn 0.72 CO3);

[0040] (4) 10 mmol carbonate precursor, 3.5 mmol Na2CO3, 0.25 mmol Li2CO3 and 1 mmol CuO were mixed and ball-milled for 12 h to obtain powder D;

[0041] (5) Powder D was calcined at 500°C for 10 h, then the temperature was uniformly raised to 900°C and calcined at a constant temperature for 12 h to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material;

[0042] The XRD pattern of the Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material in this embodiment is shown in FIG. Figure 1 ,Depend on Figure 1 It can be seen that the main crystal phase of the Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material does not change with the doping of Li and Cu dual elements, and the P2 phase is retained;

[0043] The SEM images of Li and Cu doped P2-type layered oxide cathode materials for sodium ion batteries are shown in Figure 2 ,Depend on Figure 2 It can be seen that the Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material is mainly composed of irregular hexagonal lamellar structures and a small amount of rod-like structures. The length of the hexagonal lamellar structure is about 0.2 to 4 μm, and the thickness is about 0.1 to 0.5 μm.

[0044] The charge and discharge curves of Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material are shown in Figure 2. Figure 3 ,Depend on Figure 3 It can be seen that the first charge capacity is as high as 173.4mAhg -1 , the discharge capacity is only 113.5mAhg -1 The reason for the capacity loss is irreversible structural changes and the formation of SEI film. The second charge capacity dropped to 141.3 mAh g -1 , and the discharge capacity is about 102.9mAhg -1 ; The specific capacity of the 10th charge is about 107.9mAhg -1 , and the discharge capacity is about 99.7mAhg -1 ; The 100th charge capacity is about 69.6 mAh g -1 , and the discharge capacity is about 66.3mAhg -1 ;

[0045] A sodium ion battery comprising a positive electrode, a negative electrode, a separator (glass fiber), and an electrolyte, wherein the positive electrode comprises a positive electrode current collector aluminum foil and a positive electrode material layer coated on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent (SP), and a binder (PVDF), wherein the positive electrode active material is a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material; in terms of mass percentage, the positive electrode active material (Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material) accounts for 80%, the conductive agent (SP) accounts for 10%, and the binder (PVDF) accounts for 10% in the positive electrode material layer;

[0046] The cycle performance curve of the sodium ion battery in this embodiment is shown in FIG. Figure 4 After 100 cycles, the capacity is about 66.3 mAh g -1 , the capacity retention rate is about 65.61%;

[0047] The cycle performance curves of sodium ion batteries at different rates are shown in Figure 5 The cycle test was carried out at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, and the corresponding discharge capacity was 107.4mAhg -1 , 98.9mAhg -1 , 95.4mAhg -1 , 92.2mAhg -1 、88.6mAhg -1 , and 80.1mAhg -1 The corresponding coulombic efficiencies are approximately 87.62%, 97.64%, 98.92%, 99.33%, 99.74%, and 100.02%. When recovered from 5C to 0.1C, the specific capacity can be almost recovered, indicating that the rate performance and cycle stability are reversible.

[0048] Example 3: The chemical formula of the layered oxide in this example is Na 0.66 Ni a Li b Cu c Mn d O2; wherein a=0.14, b=0.07, c=0.12, d=0.74;

[0049] A method for preparing a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, comprising the following steps:

[0050] (1) Dissolve 14 mmol of NiC4H6O4·4H2O and 74 mmol of MnC4H6O4·4H2O in 88 mL of deionized water to obtain solution A;

[0051] (2) 88 mmol of Na2CO3 was dissolved in 88 mL of deionized water to obtain solution B. At room temperature, solution B was added to solution A and mixed evenly to obtain solution C;

[0052] (3) Solution C was reacted at 30°C for 14 h, solid-liquid separation was performed, and the solid was washed three times with deionized water and ethanol, and dried at 80°C to obtain a carbonate precursor (Ni 0.14 Mn 0.74 CO3);

[0053] (4) 10 mmol carbonate precursor, 3.5 mmol Na2CO3, 0.35 mmol Li2CO3 and 1.2 mmol CuO were mixed and ball-milled for 16 h to obtain powder D;

[0054] (5) Powder D was calcined at 600°C for 12 h, then the temperature was uniformly raised to 1000°C and calcined at a constant temperature for 14 h to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material;

[0055] The Li and Cu dual-element doped P2-type layered oxide sodium ion battery cathode material of this embodiment has a large interplanar spacing and a low diffusion energy barrier, providing a fast diffusion channel for ion migration, thereby improving ion mobility and quantity;

[0056] A sodium ion battery comprising a positive electrode, a negative electrode, a separator (glass fiber), and an electrolyte, wherein the positive electrode comprises a positive electrode current collector aluminum foil and a positive electrode material layer coated on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, a conductive agent (SP), and a binder (PVDF), wherein the positive electrode active material is a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material; in terms of mass percentage, the positive electrode active material (Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material) accounts for 80%, the conductive agent (SP) accounts for 10%, and the binder (PVDF) accounts for 10% in the positive electrode material layer;

[0057] At a current density of 0.1C, the first discharge capacity of the sodium-ion battery reached 105 mAh g -1 The capacity retention rate is 58% after 100 cycles, which shows high cycle stability. The larger interplanar spacing in the material structure provides a channel for rapid diffusion of ions, thereby improving the ion mobility and quantity.

[0058] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material, characterized in that: The chemical formula of the layered oxide is Na 0.66 Ni a Li b Cu c Mn d O2; where 0.1≤a≤0.14, 0.03≤b≤0.07, 0.08≤c≤0.12, 0.70≤d≤0.74; The specific steps of the preparation method are as follows: (1) Dissolve NiC4H6O4·4H2O and MnC4H6O4·4H2O in deionized water to obtain solution A; (2) dissolving Na2CO3 in deionized water to obtain solution B, and adding solution B to solution A and mixing evenly to obtain solution C; (3) Solution C is reacted at a temperature of 20-30°C for 10-14 hours, the solid-liquid separation is carried out, the solid is washed with deionized water and ethanol, and dried to obtain a carbonate precursor; (4) mixing the carbonate precursor, Na2CO3, Li2CO3 and CuO and ball milling for 8-16 h to obtain powder D; (5) Powder D is calcined at a temperature of 400-600°C for 8-12 hours, then the temperature is uniformly increased to a temperature of 800-1000°C and calcined at a constant temperature for 10-14 hours to obtain a Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material.

2. The method for preparing the Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material according to claim 1, characterized in that: In step (1), the solid-liquid ratio of NiC4H6O4·4H2O, MnC4H6O4·4H2O and deionized water is 10-14:70-74:80-88 in mmol:mmol:mL.

3. The method for preparing the Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material according to claim 1, characterized in that: In step (2), the solid-liquid ratio of Na2CO3 to deionized water is 80-88:80-88 in mmol:mL.

4. The method for preparing the Li and Cu dual-element doped P2-type layered oxide sodium ion battery positive electrode material according to claim 1, characterized in that: In step (4), the molar ratio of the carbonate precursor, Na2CO3, Li2CO3 and CuO is 10:3.5:0.15~0.35:0.8~1.2.

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