Preparation method of positive electrode material with stable layered structure, positive electrode plate and sodium ion battery

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a preparation method of a positive electrode material with a stable layered structure, a positive electrode plate and a sodium ion battery. The general formula of the positive electrode material is Na < x > Ni Mn J < c > G < d > Q < e > O < y > Pz, j comprises Ca and / or Ti; g comprises Co and / or Cu; q comprises Mg and / or Al. In the O3-P3-O3'transformation process, J can balance electron arrangement of a high-oxidation-state transition metal layer under high voltage, the covalence of TM-O is maintained, TM is prevented from being dissolved out of a bulk phase in an ionic state, and a layered structure is maintained; transition metal of G is reduced in the discharging process, the stability of external electrons of the transition metal in arrangement of a 3d track is maintained, and the ginger-Taylor effect caused by Mn < 3 + > is reduced; o-Na-O and O-TM-O layers can be stabilized by doping Q, and volume change caused by complex phase change is reduced; p provides additional e-to maintain the electron energy density of the layered structure.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular, to a preparation method of a cathode material with a stable layered structure, a cathode sheet and a sodium ion battery. Background Art

[0002] In the field of modern battery technology, sodium oxide cathode materials have attracted much attention due to their potential cost advantages and rich resources.

[0003] However, in an application environment with a high voltage (greater than 4.1V), such cathode materials face severe challenges. A complex phase change process occurs inside. That is, when charging below 4.1V, it changes from the O3 phase to the P3 phase, and this phase is stable and reversible. When charging above 4.1V, there is a shortage of sodium ions between the layers. In order to avoid the oxygen ions facing each other, the transition metal layer will slip, resulting in a more complex phase change. This phase change process causes a large number of structural defects inside the material, seriously damaging the original stable crystal structure of the material. At the same time, during the phase change process, transition metal elements migrate, and in subsequent cycling processes, these transition metals will dissolve out. The dissolution of transition metals further exacerbates the damage to the material structure, resulting in a significant decline in the performance of sodium oxide cathode materials, including problems such as capacity attenuation and poor cycling stability.

[0004] This series of problems severely restricts the effective application of sodium oxide cathode materials in a high-voltage environment, becoming a technical problem that urgently needs to be solved. Therefore, it is urgent to develop corresponding improvement technologies or solutions to overcome the above defects, improve the performance of sodium oxide cathode materials under high-voltage working conditions, and meet the ever-developing energy storage technology requirements.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a cathode material with a stable layered structure. During the O3-P3-O3' phase transition process, the electronic arrangement of J ions, that is, the 3d empty orbitals, is not electrochemically active, which can balance the electronic arrangement of the high-oxidation-state transition metal layer under high voltage, maintain the covalency of TM-O, avoid the dissolution of TM (transition metal) in the form of ions from the bulk phase, and maintain the layered structure; G ions are electrochemically active. During the discharging process, the transition metal is reduced, maintaining the stability of the 3d orbit of the outer electrons of the transition metal and reducing the 3+ Jahn-Teller effect caused by Mn -, maintaining the electronic energy density of the layered structure; doping Q, which has no electrochemical activity, can stabilize the O-Na-O and O-TM-O layers, and reduce the volume change caused by complex phase transitions. Therefore, by adopting the cathode material with a specific general formula in the present invention, the four elements J, G, Q, and P work together synergistically, which can significantly improve its capacity, cycle retention rate, and constant current charge ratio at high voltages (greater than 4.1V).

[0007] The second object of the present invention is to provide a preparation method for a cathode material with a stable layered structure, which has the advantages of simple operation, short process, and easy large-scale production.

[0008] The third object of the present invention is to provide a cathode sheet.

[0009] The fourth object of the present invention is to provide a sodium-ion battery, which has a high capacity, a high constant current charge ratio, and excellent cycling performance.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] The present invention first provides a cathode material with a stable layered structure, and the general formula of the cathode material is Na x Ni a Mn b J c G d Q e O y P z ; wherein, J includes at least one of Ca and Ti elements; G includes at least one of Co and Cu elements; Q includes at least one of Mg and Al elements; 0.85 ≤ x < 0.95, 0.35 < a < 0.45, 0.3 < b < 0.5, 0.01 < c < 0.15, 0.05 ≤ d < 0.2, 0.01 ≤ e < 0.1, 1.75 ≤ y < 1.90, 0.01 < z ≤ 0.1, and a + b + c + d + e = 1.

[0012] Furthermore, the cathode material is an O3-type layered oxide cathode material.

[0013] Furthermore, in the X-ray diffraction pattern of the cathode material, the diffraction angle 2θ of the 003 characteristic peak is 16.5° - 17°, and the diffraction angle 2θ of the 104 characteristic peak is 41.5° - 42.5°.

[0014] Furthermore, the morphology of the cathode material is a single crystal morphology.

[0015] Furthermore, the particle size D50 of the cathode material is 6 - 9μm.

[0016] The present invention further provides a method for preparing the cathode material of the above-mentioned stable layered structure, comprising the following steps: mixing a sodium source, a nickel-manganese precursor, an additive containing J, an additive containing G, an additive containing Q, and an additive containing phosphorus, and then performing a first calcination and a second calcination in sequence.

[0017] Further, the temperature of the first calcination is 930-980 °C.

[0018] Further, the temperature of the second calcination is 850-900 °C.

[0019] The present invention also provides a cathode sheet, comprising the cathode material of the above-mentioned stable layered structure.

[0020] The present invention further provides a sodium-ion battery, comprising the above-mentioned cathode sheet.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] During the O3-P3-O3' phase transition, the electron arrangement of J ions, that is, the 3d empty orbitals, is not electrochemically active, which can balance the electron arrangement of the high-oxidation-state transition metal layer at high voltages, maintain the covalency of TM-O, avoid the dissolution of TM in the form of ions from the bulk phase, and maintain the layered structure; G ions are electrochemically active. During the discharge process, the transition metal is reduced, maintaining the stability of the 3d orbitals of the outer electrons of the transition metal, and reducing the Jahn-Teller effect caused by Mn 3+ The addition of the anion P provides additional e - , maintaining the electron energy density of the layered structure; doping Q that is not electrochemically active can stabilize the O-Na-O and O-TM-O layers, reducing the volume change caused by complex phase transitions. Therefore, by using a cathode material with a specific general formula, the present invention can significantly improve its capacity, cycle retention rate, and constant current charge ratio at high voltages (greater than 4.1 V) through the synergistic effect of J, G, Q, and P. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 SEM image of the cathode material prepared in Example 1 provided by the present invention;

[0025] Figure 2 SEM image of the cathode material prepared in Comparative Example 1 provided by the present invention;

[0026] Figure 3 Comparison chart of the first - week charge - discharge curves of the batteries prepared from the positive electrode materials of Example 1 and Comparative Example 1 provided by the present invention;

[0027] Figure 4 Comparison chart of the 300 - week cycle curves of the batteries prepared from the positive electrode materials of Example 1 and Comparative Example 1 provided by the present invention. Detailed implementation manners

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and detailed implementation manners. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present invention, not all of them. They are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0029] If there is no special indication, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non - exhaustive listing and description, and it should be understood that they do not constitute a closed - type limitation on quantity.

[0030] If there is no special indication, the "including" and "comprising" mentioned in the present invention mean open - type, and can also be closed - type. For example, the "including" and "comprising" can mean that other components not listed can also be included, or it can only include or comprise the listed components.

[0031] If there is no special indication, in the present invention, "one or more" or "at least one" refers to any one, any two or any two or more of the listed items. Among them, "several" refers to any two or any two or more.

[0032] In the first aspect, the present invention provides a positive electrode material for a high - voltage sodium - ion battery with a stable layered structure. The general formula of the positive electrode material is Na x Ni a Mn b J c G d Q e O y P z 。

[0033] Among them, J includes at least one of Ca and Ti elements.

[0034] G includes at least one of Co and Cu elements.

[0035] Q includes at least one of Mg and Al elements.

[0036] 0.85 ≤ x < 0.95, including point values of any one of 0.85, 0.86, 0.87, 0.88, 0.90, 0.92, 0.94 and range values between any two of them.

[0037] 0.35 < a < 0.45, including point values of any one of 0.36, 0.37, 0.38, 0.40, 0.41, 0.42, 0.44 and range values between any two of them.

[0038] 0.3 < b < 0.5, including point values of any one of 0.32, 0.33, 0.34, 0.35, 0.36, 0.38, 0.40, 0.42, 0.43, 0.45, 0.46, 0.48 and range values between any two of them.

[0039] 0.01 < c < 0.15, including point values of any one of 0.02, 0.03, 0.05, 0.06, 0.08, 0.10, 0.12, 0.14 and range values between any two of them.

[0040] 0.05 ≤ d < 0.2, including point values of any one of 0.05, 0.06, 0.08, 0.10, 0.12, 0.13, 0.15, 0.16, 0.18 and range values between any two of them.

[0041] 0.01 ≤ e < 0.1, including point values of any one of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 and range values between any two of them.

[0042] 1.75 ≤ y < 1.90, including point values of any one of 1.75, 1.76, 1.78, 1.80, 1.82, 1.83, 1.85, 1.88, 1.90 and range values between any two of them.

[0043] 0.01 < z ≤ 0.1, including point values of any one of 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 and range values between any two of them.

[0044] And a + b + c + d + e = 1.

[0045] For the cathode material with a stable layered structure provided by the present invention, during the O3-P3-O3' phase transition, the electron arrangement of J ions, that is, the 3d empty orbitals, is electrochemically inactive, which can balance the electron arrangement of the high-oxidation-state transition metal layer at high voltages, maintain the covalency of TM-O, prevent TM (transition metal) from dissolving out of the bulk phase in an ionic state, and maintain the layered structure.

[0046] Meanwhile, G ions are electrochemically active. During the discharge process, the transition metal is reduced to maintain the stability of the 3d orbitals of the outer electrons of the transition metal and reduce the 3+ Jahn-Teller effect caused by Mn.

[0047] Moreover, the addition of anion P provides extra e - to maintain the electron energy density of the layered structure.

[0048] In addition, doping with Q, which is electrochemically inactive, can stabilize the O-Na-O and O-TM-O layers and reduce the volume change caused by complex phase transitions.

[0049] Therefore, by using the cathode material with a specific chemical formula, the present invention enables J, G, Q, and P to work synergistically, significantly improving its capacity and cycling performance at high voltages (greater than 4.1 V). Moreover, this cathode material has small polarization, good reversibility, and large rate capacity.

[0050] In some specific embodiments, the cathode material is an O3-type layered oxide cathode material.

[0051] In some specific embodiments, in the X-ray diffraction pattern of the cathode material, the diffraction angle 2θ of the 003 characteristic peak is 16.5° to 17°, such as 16.6°, 16.7°, 16.8°, 16.9°, or 17.0°.

[0052] In some specific embodiments, in the X-ray diffraction pattern of the cathode material, the diffraction angle 2θ of the 104 characteristic peak is 41.5° to 42.5°, such as 41.7°, 41.8°, 41.9°, 42.0°, 42.1°, 42.2°, 42.3°, 42.4°, or 42.5°.

[0053] In some specific embodiments, the morphology of the cathode material is a single crystal morphology.

[0054] In some specific embodiments, the particle size D50 of the cathode material is 6 to 9 μm, including but not limited to the point values of any one of 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or the range values between any two of them.

[0055] In a second aspect, the present invention provides a method for preparing the cathode material of the stable layered structure, comprising the following steps:

[0056] After uniformly mixing a sodium source, a nickel-manganese precursor, an additive containing J, an additive containing G, an additive containing Q, and a phosphorus-containing additive, first calcination and second calcination are carried out in sequence.

[0057] This preparation method has the advantages of simple operation, short process, and being capable of realizing large-scale production.

[0058] Among them, the purpose of the first calcination is: preliminary decomposition, releasing CO2, H2O, etc. in the raw materials, forming the material unit cell, and crystallizing and growing. However, the release of decomposition products will generate defects and pores, resulting in the affected crystallinity. The purpose of the second calcination is: completing the remaining solid-phase reaction, continuing the crystallization reaction, and promoting grain growth and densification.

[0059] Among them, the sodium source includes sodium-containing compounds, such as sodium carbonate and sodium hydroxide.

[0060] Among them, the nickel-manganese precursor includes, but is not limited to, carbonates of nickel and manganese and hydroxides of nickel and manganese.

[0061] It can be understood that the additive containing J refers to an additive containing J, such as a compound containing J, where J includes at least one of the elements Ca and Ti.

[0062] It can be understood that the additive containing G refers to an additive containing G, such as a compound containing G, where G includes at least one of the elements Co and Cu.

[0063] It can be understood that the additive containing Q refers to an additive containing Q, such as a compound containing Q, where Q includes at least one of the elements Mg and Al.

[0064] Among them, the phosphorus-containing additive includes phosphorus-containing compounds, such as disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, ammonium phosphate, etc.

[0065] In some specific embodiments, the temperature of the first calcination is 930 - 980 °C, including, but not limited to, any point value among 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C or the range value between any two of them.

[0066] In some specific embodiments, the heat preservation time of the first calcination is 12 - 18 h, but is not limited thereto.

[0067] In some specific embodiments, the first calcination is carried out in an air atmosphere or an oxygen atmosphere.

[0068] In some specific embodiments, the temperature of the second calcination is 850-900 °C, including but not limited to the point values of any one of 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C or the range values between any two of them.

[0069] In some specific embodiments, the heat preservation time of the second calcination is 10-15 h, but not limited thereto.

[0070] In some specific embodiments, the second calcination is carried out in an air atmosphere or an oxygen atmosphere.

[0071] In some specific embodiments, the steps of pulverization are respectively included after the first calcination and the second calcination.

[0072] In a third aspect, the present invention provides a positive electrode sheet, which includes the positive electrode material with the stable layered structure.

[0073] In some specific embodiments, the positive electrode sheet further includes a binder and a conductive agent, and the present invention does not limit this.

[0074] In a fourth aspect, the present invention provides a sodium ion battery, which includes the positive electrode sheet.

[0075] The sodium ion battery has a high capacity, a high constant current charge ratio, and excellent cycle performance.

[0076] In some specific embodiments, the sodium ion battery further includes a negative electrode sheet, a separator and an electrolyte, and the present invention does not limit this.

[0077] Hereinafter, the embodiments of the present invention will be described in detail in conjunction with the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0078] Example 1

[0079] The preparation method of the positive electrode material Na 0.9 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.02 Al 0.03 O 1.84 P 0.07 with a stable layered structure provided in this example includes the following steps:

[0080] Calculated according to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni0.4 Mn 0.4 The nickel-manganese precursor of (OH)2, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3, and NH4H2PO4 (containing phosphorus additive). The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0081] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 15 h. The product after the first calcination is subjected to primary air flow pulverization to obtain a semi-finished product.

[0082] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 900 °C and held for 10 h. The product after the second calcination is subjected to secondary air flow pulverization, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 6.3 μm.

[0083] The cathode material prepared in this example is an O3-type layered oxide cathode material. The SEM image of the cathode material prepared in this example is shown in Figure 1 as follows, and Figure 1 it can be seen that it has a single crystal morphology.

[0084] Example 2

[0085] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.92 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.05 Cu 0.02 Co 0.05 Mg 0.06 O 1.875 P 0.04 is as follows:

[0086] Calculated according to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive) are weighed in sequence. The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0087] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 12 h. The product after the first calcination is subjected to primary air flow pulverization to obtain a semi-finished product.

[0088] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 890 °C and held for 15 h. The product after the second calcination is subjected to secondary air flow pulverization, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 7.6 μm.

[0089] Example 3

[0090] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.88 Ni 0.4 Mn 0.4 Ti 0.05 Cu 0.05 Co 0.05 Mg 0.02 Al 0.03 O 1.795 P 0.09 is as follows:

[0091] Calculated according to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.4 Mn 0.4 CO3 nickel-manganese precursor, TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive) are weighed in sequence. The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0092] The uniformly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 12 h. The product after the first calcination is subjected to primary air flow pulverization to obtain a semi-finished product.

[0093] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 890 °C and held for 14 h. The product after the second calcination is subjected to secondary air flow pulverization, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 8.4 μm.

[0094] Example 4

[0095] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.88 Ni 0.4 Mn 0.4 Ti 0.03 Cu 0.05 Co 0.1 Al 0.0 2O 1.885 P 0.03 is as follows:

[0096] Calculated according to the stoichiometric ratio, sodium carbonate (sodium source), Ni0.4 Mn 0.4 (OH)2 nickel-manganese precursor, TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0097] Load the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 970 °C and hold for 14 h. Conduct primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0098] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 850 °C and hold for 10 h. Conduct secondary air jet milling on the product after the second calcination and control the milling parameters to obtain a cathode material with a particle size D50 = 6.1 μm.

[0099] Example 5

[0100] The preparation method of the cathode material with a stable layered structure provided in this example is Na 0.85 Ni 0.38 Mn 0.42 Ca 0.01 Ti 0.01 Cu 0.05 Co 0.1 Mg 0.01 Al 0.02 O 1.825 P 0.06 includes the following steps:

[0101] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), Ni 0.38 Mn 0.42 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0102] Load the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 930 °C and hold for 13 h. Conduct primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0103] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 890 °C and hold for 14 h. Conduct secondary air jet milling on the product after the second calcination and control the milling parameters to obtain a cathode material with a particle size D50 = 8.6 μm.

[0104] Example 6

[0105] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.94 Ni 0.42 Mn 0.38 Ti 0.05 Cu 0.05 Co 0.03 Mg 0.0 2Al 0.05 O 1.805 P 0.09 is as follows:

[0106] According to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.42 Mn 0.38 (OH)2 nickel-manganese precursor, TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive) are weighed in sequence. The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0107] The uniformly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 940 °C and held for 12 h. The product after the first calcination is subjected to primary air flow pulverization to obtain a semi-finished product.

[0108] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 900 °C and held for 10 h. The product after the second calcination is subjected to secondary air flow pulverization, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 7.6 μm.

[0109] Example 7

[0110] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.94 Ni 0.42 Mn 0.35 Ca 0.03 Ti 0.03 Cu 0.05 Co 0.0 5Mg 0.02 Al 0.05 O 1.75 P 0.1 is as follows:

[0111] According to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.42 Mn 0.35Nickel-manganese precursor of (OH)2, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive). The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0112] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 980 °C and held for 14 h. The product after the first calcination is subjected to airflow crushing once to obtain a semi-finished product.

[0113] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 890 °C and held for 14 h. The product after the second calcination is subjected to airflow crushing twice, and the crushing parameters are controlled to obtain a cathode material with a particle size D50 = 7.2 μm.

[0114] Example 8

[0115] The preparation method of the cathode material with a stable layered structure provided in this example, Na 0.91 Ni 0.38 Mn 0.45 Ti 0.01 Cu 0.05 Co 0.1 Al 0.0 1O 1.85 P 0.08 includes the following steps:

[0116] Calculated according to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.38 Mn 0.45 (OH)2 nickel-manganese precursor, TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive). The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0117] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 13 h. The product after the first calcination is subjected to airflow crushing once to obtain a semi-finished product.

[0118] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 850 °C and held for 12 h. The product after the second calcination is subjected to airflow crushing twice, and the crushing parameters are controlled to obtain a cathode material with a particle size D50 = 7.5 μm.

[0119] Comparative Example 1

[0120] The preparation method of the cathode material Na 0.8 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.02 Al 0.03 O 1.79 P 0.07 (i.e., x = 0.8) includes the following steps:

[0121] According to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive) are weighed in sequence. The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0122] The uniformly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 990 °C and held for 11 h. The product after the first calcination is subjected to primary air jet milling to obtain a semi-finished product.

[0123] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 830 °C and held for 13 h. The product after the second calcination is subjected to secondary air jet milling, and the milling parameters are controlled to obtain a cathode material with a particle size D50 = 5.5 μm.

[0124] The SEM image of the cathode material prepared in this comparative example is shown in Figure 2 as follows.

[0125] Comparing Figure 1 and Figure 2 it can be seen that Figure 1 the particles of the material in Figure 2 are regular, the particle size distribution is concentrated, the particle surface is smooth, and no obvious structural defects are found. On the contrary, there are many flaky particles in the material in Figure 2 , the particle surface is rough, and micron-scale stepped protrusions appear. The difference between Example 1 and Comparative Example 1 lies in the Na content, indicating that the Na content has a great influence on the morphology of the material and will directly affect the crystal growth of the material, that is, the crystal growth kinetics.

[0126] Comparative Example 2

[0127] The cathode material Na1Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.05 Mg0.02 Al 0.03 O 1.89 P 0.07 (i.e., x = 1) The preparation method comprises the following steps:

[0128] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0129] Load the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 930 °C and keep it warm for 21 h. Conduct primary air flow pulverization on the product after the first calcination to obtain a semi-finished product.

[0130] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 940 °C and keep it warm for 20 h. Conduct secondary air flow pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 11.8 μm.

[0131] Comparative Example 3

[0132] The cathode material Na 0.9 Ni 0.32 Mn 0.55 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.02 Al 0.03 O 2.06 P 0.07 (i.e., a + b + c + d + e = 1.07) The preparation method comprises the following steps:

[0133] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.32 Mn 0.55 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive) and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0134] Load the uniformly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 940 °C and hold for 20 h. Conduct primary air pulverization on the product after the first calcination to obtain a semi-finished product.

[0135] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 910 °C and hold for 9 h. Conduct secondary air pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 7.7 μm.

[0136] Comparative Example 4

[0137] The cathode material Na 0.9 Ni 0.5 Mn 0.28 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.02 Al 0.03 O 1.7 P 0.07 (i.e., a = 0.5, b = 0.28) The preparation method includes the following steps:

[0138] Calculate according to the stoichiometric ratio, and sequentially weigh sodium carbonate (sodium source), Ni 0.5 Mn 0.28 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0139] Load the uniformly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 1000 °C and hold for 18 h. Conduct primary air pulverization on the product after the first calcination to obtain a semi-finished product.

[0140] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 840 °C and hold for 19 h. Conduct secondary air pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 11.4 μm.

[0141] Comparative Example 5

[0142] The cathode material Na 0.9 Ni 0.4 Mn 0.4 Ca 0.04 Ti 0.16 Cu 0.05 Mg 0.02 Al 0.03O 2.02 P 0.07 (i.e., a + b + c + d + e = 1.1) The preparation method includes the following steps:

[0143] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0144] Put the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 940 °C and keep it warm for 16 h. Conduct primary air flow pulverization on the product after the first calcination to obtain a semi-finished product.

[0145] Put the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 950 °C and keep it warm for 7 h. Conduct secondary air flow pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 7.2 μm.

[0146] Comparative Example 6

[0147] The cathode material Na 0.9 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.1 Co 0.15 Mg 0.02 Al 0.03 O 2.115 P 0.07 (i.e., a + b + c + d + e = 1.2) The preparation method includes the following steps:

[0148] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0149] Load the uniformly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 930 °C and hold for 21 h. Perform primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0150] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 900 °C and hold for 20 h. Perform secondary air jet milling on the product after the second calcination and control the milling parameters to obtain a cathode material with a particle size D50 = 7.0 μm.

[0151] Comparative Example 7

[0152] The cathode material Na 0.9 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.04 Al 0.1 O 1.965 P 0.07 (i.e., a + b + c + d + e = 1.09) The preparation method includes the following steps:

[0153] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive) in sequence. Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0154] Load the uniformly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace. Conduct the first calcination at 930 °C and hold for 14 h. Perform primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0155] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Conduct the second calcination at 840 °C and hold for 18 h. Perform secondary air jet milling on the product after the second calcination and control the milling parameters to obtain a cathode material with a particle size D50 = 7.8 μm.

[0156] Comparative Example 8

[0157] The cathode material Na 0.9 Ni 0.4 Mn 0.4 Ca 0.02 Ti 0.08 Cu 0.05 Mg 0.02 Al0.03 O 1.765 P 0.12 (i.e., z = 0.12) The preparation method includes the following steps:

[0158] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0159] Put the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace for the first calcination at 930 °C and hold for 21 h. Perform primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0160] Put the semi-finished product into a ceramic crucible and place it in a high-temperature furnace for the second calcination at 900 °C and hold for 13 h. Perform secondary air jet milling on the product after the second calcination and control the milling parameters to obtain a cathode material with a particle size D50 = 8.3 μm.

[0161] Comparative Example 9

[0162] The cathode material Na 0.95 Ni 0.42 Mn 0.45 Cu 0.05 Co 0.05 Mg 0.01 Al 0.02 O 1.93 P 0.02 (i.e., without J) The preparation method includes the following steps:

[0163] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CuO (containing G additive), Co3O4 (containing G additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0164] Put the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace for the first calcination at 950 °C and hold for 15 h. Perform primary air jet milling on the product after the first calcination to obtain a semi-finished product.

[0165] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace for the second calcination at 900 °C and hold for 12 h. Perform secondary air flow pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 10.9 μm.

[0166] Comparative Example 10

[0167] The cathode material Na 0.95 Ni 0.42 Mn 0.45 Ca 0.05 Ti 0.05 Mg 0.01 Al 0.02 O 1.955 P 0.02 (i.e., without G) The preparation method includes the following steps:

[0168] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), MgCO3 (containing Q additive), Al(OH)3 (containing Q additive), and NH4H2PO4 (containing phosphorus additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0169] Load the evenly mixed raw materials into a ceramic crucible and place it in a high-temperature furnace for the first calcination at 950 °C and hold for 15 h. Perform primary air flow pulverization on the product after the first calcination to obtain a semi-finished product.

[0170] Load the semi-finished product into a ceramic crucible and place it in a high-temperature furnace for the second calcination at 900 °C and hold for 12 h. Perform secondary air flow pulverization on the product after the second calcination, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 8 μm.

[0171] Comparative Example 11

[0172] The cathode material Na 0.95 Ni 0.42 Mn 0.45 Ca 0.05 Ti 0.05 Cu 0.05 Co 0.05 O 2.04 P 0.02 (i.e., without Q) The preparation method includes the following steps:

[0173] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), Ni 0.4 Mn 0.4Nickel-manganese (OH)2 precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), Co3O4 (containing G additive), and NH4H2PO4 (containing phosphorus additive). The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0174] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 15 h. The product after the first calcination is subjected to airflow pulverization once to obtain a semi-finished product.

[0175] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 900 °C and held for 12 h. The product after the second calcination is subjected to airflow pulverization twice, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 9.2 μm.

[0176] Comparative Example 12

[0177] The cathode material Na 0.95 Ni 0.42 Mn 0.45 Ca 0.05 Ti 0.05 Cu 0.05 Co 0.05 Mg 0.01 Al 0.02 O 2.11 (i.e., without P) is prepared by the following steps:

[0178] According to the stoichiometric ratio, sodium carbonate (sodium source), Ni 0.4 Mn 0.4 (OH)2 nickel-manganese precursor, CaO (containing J additive), TiO2 (containing J additive), CuO (containing G additive), CoO (containing G additive), MgCO3 (containing Q additive), and Al(OH)3 (containing Q additive) are weighed in sequence. The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature calcination reaction.

[0179] The evenly mixed raw materials are loaded into a ceramic crucible and placed in a high-temperature furnace for the first calcination at 950 °C and held for 15 h. The product after the first calcination is subjected to airflow pulverization once to obtain a semi-finished product.

[0180] The semi-finished product is loaded into a ceramic crucible and placed in a high-temperature furnace for the second calcination at 900 °C and held for 12 h. The product after the second calcination is subjected to airflow pulverization twice, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 10.2 μm.

[0181] The cathode materials prepared in Examples 2-8 are all O3-type layered oxide cathode materials, and their morphologies are all single-crystal morphologies. The diffraction angles 2θ of the 003 characteristic peak and the diffraction angle 2θ of the 104 characteristic peak in the X-ray diffraction (XRD) patterns of the cathode materials prepared in each example and each comparative example are shown in Table 1.

[0182] Table 1 Diffraction angles 2θ of the 003 characteristic peak and the 104 characteristic peak of each cathode material

[0183]

[0184]

[0185] Experimental example

[0186] Preparation of coin cells: Using the cathode materials prepared in each example and each comparative example as active substances, 0.45 g of active substance, 0.025 g of SP (SP is specifically Super P, a conductive carbon black from TIMCAL, Switzerland), and 0.25 g of polyvinylidene fluoride colloidal solution (mass percentage 10%, solute is SOLVAY PVDF5130, solvent is NMP) are uniformly mixed, and then NMP is added to make a viscous colloidal solution. The colloidal solution is coated on an aluminum foil with a thickness of 16 μm, and then baked in a vacuum drying oven at 120 °C for 12 h to obtain a cathode electrode sheet with an active substance areal density of 5 mg / cm 2 ². Using a 300-μm-thick sodium metal sheet (Aladdin) as the counter electrode, a 675-μm-thick glass fiber (Waterman) as the separator, and a 1 mol / L NaPF6 solution (the solvent is a 1:1 volume ratio mixture of EC and DMC) as the electrolyte, 2032 coin cells are assembled in an Ar atmosphere-protected glove box. Then, at 25 °C, each cell is charged at a constant current of 0.1C (nominal specific capacity 100 mAh / g) to 4.5 V, then charged at a constant voltage until the current is less than or equal to 0.01 mA, then left standing for 5 minutes, and then discharged at a constant current of 0.1C to 1.5 V. This is the activation process of the battery, and subsequent tests are carried out after activation.

[0187] The first-cycle discharge specific capacities of each coin cell are tested respectively, and the test method is as follows: At 25 °C, the cell is charged at a constant current of 0.1C to 4.2 V, then charged at a constant voltage until the current is less than or equal to 0.01 mA, then left standing for 5 minutes, and then discharged at a constant current of 0.1C to 2.5 V. The discharge specific capacity at this time is the first-cycle discharge specific capacity.

[0188] Preparation of full cells: Using the cathode materials prepared in each example and each comparative example as the positive electrode active substances, sodium-ion batteries are made according to the following method:

[0189] Preparation of the positive electrode slurry: Weigh accurately the positive electrode active material, SP, and PVDF using an electronic balance according to a specific mass ratio (positive electrode active material:SP:PVDF = 95:3:2). First, dissolve PVDF in N-methylpyrrolidone (NMP), and stir with a vacuum planetary mixer until it is completely dissolved; then add the conductive agent SP to the above solution, and stir well to mix and disperse; then add the positive electrode active material and continue to stir until a uniform and agglomerate-free positive electrode slurry is formed.

[0190] Preparation of the negative electrode slurry: Weigh accurately the negative electrode active material, SBR, SP, and CMC using an electronic balance according to a specific mass ratio (negative electrode active material:SBR:SP:CMC = 94:3:1.5:1.5).

[0191] First, dissolve CMC in deionized water, and stir with a vacuum planetary mixer until it is completely dissolved. Then add SBR and SP to the above solution, and stir well to mix and disperse; then add the negative electrode active material and continue to stir until a uniform and agglomerate-free negative electrode slurry is formed.

[0192] Preparation of the electrode sheet: Use a coater to uniformly coat the positive / negative electrode slurry on the aluminum foil current collector, with the surface density designed as N / P = 1.15, and the control range is ±0.3 g / m 2 . (N / P = (specific capacity of the negative electrode active material × negative electrode surface density × negative electrode active material content ratio) ÷ (specific capacity of the positive electrode active material × positive electrode surface density × positive electrode active material content ratio)). Dry the current collector coated with the slurry to remove the solvents NMP / deionized water. After drying, roll the electrode sheet with a rolling press, and then use a slitter to slit the electrode sheet into the required width, and use a punching machine to punch it into electrode sheets of the required length.

[0193] Preparation of the electrolyte: Dissolve NaPF6 in a mixed solvent of EC, DMC, and FEC to prepare a 1 mol / L solution.

[0194] Battery assembly: Wind the positive electrode sheet, separator, and negative electrode sheet in sequence into a cylindrical battery core, put the battery core into a cylindrical battery case, inject the electrolyte, and then seal the battery.

[0195] Battery formation: Conduct the first charge and discharge process on the packaged battery, that is, formation. The formation regime is to first charge at a constant current of 0.05C to 50% SOC, and then charge at a constant current of 0.1C to 100% SOC to form a stable solid electrolyte interface (SEI) film on the electrode surface.

[0196] After the battery formation is completed, the battery is subjected to electrochemical performance tests according to the following methods respectively:

[0197] 1. Constant volume test:

[0198] Test with a battery charge and discharge tester, and set the conditions as follows:

[0199] a) 0.1C - DC to 1.5V;

[0200] b) Put for 10 min;

[0201] c) 0.1C - CC to 4.2V, CV to 0.05C;

[0202] d) Put for 10 min;

[0203] e) 0.1C - DC to 1.5V;

[0204] f) End.

[0205] The constant current charging ratio is obtained by dividing the capacity of the CC section in step c by the sum of the capacities of the CC section and the CV section, and the percentage of constant current charging is obtained.

[0206] 2. Cycling test:

[0207] Test with a battery charge and discharge tester, and set the conditions as follows:

[0208] a) 0.1C - DC to 1.5V;

[0209] b) Put for 10 min;

[0210] c) 1C - CC to 4.2V, CV to 0.05C;

[0211] d) Put for 10 min;

[0212] e) 1C - DC to 1.5V;

[0213] f) Set b - e as n Cycles;

[0214] g) End.

[0215] The discharge capacity mAh of different cycle numbers in step e is divided by the discharge capacity mAh in the first cycle to obtain the cycle retention rate % of the battery.

[0216] The test results are shown in Table 2.

[0217] Table 2 Electrochemical performance results

[0218]

[0219]

[0220] Among them, a high constant current charging ratio indicates that the cathode material has small polarization, good reversibility, and large rate capacity.

[0221] Among them, Figure 3 is a comparative chart of the first-week charge-discharge curves of the batteries prepared from the cathode materials of Example 1 and Comparative Example 1.

[0222] Figure 4 is a comparative chart of the 300-week cycle curves of the batteries prepared from the cathode materials of Example 1 and Comparative Example 1.

[0223] It can be seen from Table 1 that the sodium-ion batteries assembled with the cathode materials prepared in each example have high capacity, high constant-current charge ratio, and high cycle retention rate.

[0224] However, for the cathode materials prepared in each comparative example, due to the absence of doping with J, G, Q, or P, or not conforming to the specific chemical formula Na x Ni a Mn b J c G d Q e O y P z , the capacity, constant-current charge ratio, and cycle retention rate decrease.

[0225] It can be seen that by adopting the cathode material with a specific chemical formula and doping with J, G, Q, or P simultaneously, and the synergistic effect of these four, the capacity, constant-current charge ratio, and cycle stability of the cathode material at high voltage (>4.1V) can be significantly improved.

[0226] Although the present invention has been illustrated and described with specific examples, it should be realized that the above examples are only used to illustrate the technical solutions of the present invention, rather than limiting it; those of ordinary skill in the art should understand that without departing from the spirit and scope of the present invention, the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of each example of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A cathode material with a stable layered structure, characterized in that, The general formula of the positive electrode material is Na x Ni a Mn b J c G d Q e O y P z ; Among them, J includes at least one of Ca and Ti elements; G includes at least one of Co and Cu elements; Q includes at least one of Mg and Al elements; 0.85 ≤ x < 0.95, 0.35 < a < 0.45, 0.3 < b < 0.5, 0.01 < c < 0.15, 0.05 ≤ d < 0.2, 0.01 ≤ e < 0.1, 1.75 ≤ y < 1.90, 0.01 < z ≤ 0.1, and a + b + c + d + e = 1.

2. The cathode material of the stable layered structure according to claim 1, characterized in that The positive electrode material is an O3-type layered oxide positive electrode material.

3. The cathode material with a stable layered structure according to claim 2, characterized in that, In the X-ray diffraction pattern of the positive electrode material, the diffraction angle 2θ of the 003 characteristic peak is 16.5° to 17°, and the diffraction angle 2θ of the 104 characteristic peak is 41.5° to 42.5°.

4. The cathode material with a stable layered structure according to claim 1, characterized in that The morphology of the positive electrode material is a single crystal morphology.

5. The cathode material of the stable layered structure according to claim 1, characterized in that, The particle size D50 of the positive electrode material is 6 to 9 μm.

6. The preparation method of the cathode material of the stable layered structure according to any one of claims 1 to 5, characterized in that, It includes the following steps: Mix a sodium source, a nickel-manganese precursor, an additive containing J, an additive containing G, an additive containing Q, and a phosphorus-containing additive, and then perform a first calcination and a second calcination in sequence.

7. The method for preparing the cathode material with a stable layered structure according to claim 6, characterized in that, The temperature of the first calcination is 930 to 980 °C.

8. The preparation method of the cathode material with a stable layered structure according to claim 6, characterized in that, The temperature of the second calcination is 850 to 900 °C.

9. A positive electrode sheet, characterized in that, It includes the positive electrode material with a stable layered structure according to any one of claims 1 to 5.

10. A sodium-ion battery, characterized in that, It includes the positive electrode sheet according to claim 9.

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