Directional doping modified positive electrode material, preparation method thereof, positive plate and sodium ion battery

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a directional doping modified positive electrode material, a preparation method thereof, a positive electrode plate and a sodium ion battery. The structural formula of the positive electrode material is Na < x > A < e > Ni Mn Cu < c > Ti < d > G < f > O < 2 > F < y >, a comprises at least one of K and Ca; g comprises at least one of Mg, Al, Zn, Sr, Y and Zr. A which has an ionic radius similar to that of Na < + > and does not have electrochemical activity enters a Na layer through doping, so that a layered structure in a high sodium removal state is stabilized; the element G with the ion radius larger than that of TM and without electrochemical activity enters the TM layer through doping, the coordination environment of O in the high sodium removal state is stabilized, TM cannot break through the coordination relation of octahedrons, and then the layered structure is maintained; due to the addition of the anion F, the special F-TM can anchor TM and inhibit TM migration. Through the synergistic effect of the three components, the capacity, rate, cycle and other performances under high voltage are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular, to a cathode material modified by directional doping, a preparation method thereof, a cathode sheet and a sodium ion battery. Background Art

[0002] With the increasing energy demand and the continuous improvement of the requirements for energy storage technologies, sodium ion batteries, as a new and promising energy storage system, have received extensive attention. Compared with traditional lithium ion batteries, sodium ion batteries have significant advantages such as rich sodium resources and low cost, and are expected to play a key role in the field of large-scale energy storage.

[0003] Among the core components of sodium ion batteries, the performance of the cathode material plays a decisive role. Currently, sodium oxide cathode materials for sodium ion batteries have become one of the research hotspots due to their high theoretical specific capacity, suitable voltage platform and other characteristics. However, these materials face severe challenges in the actual application process, which limit the improvement of the overall performance of sodium ion batteries and the large-scale commercialization process.

[0004] Specifically, when the battery is in a charge-discharge environment with a high voltage (>4.1V), a very difficult problem is exposed in the sodium oxide cathode material. Since the electrochemical environment inside the material changes violently at this time, sodium ions (Na) will undergo a deintercalation behavior, and the deintercalation ratio is often as high as more than 80%. Such a high proportion of Na deintercalation has a catastrophic impact on the crystal structure of the material. Specifically, the O-Na-O layer structure in the material cannot maintain its original stability, obvious slip phenomenon occurs, and a large number of dislocations are triggered. This disorder of the crystal structure completely breaks the TM-O-Na coordination balance in the originally balanced O-TM-O layer (where TM represents transition metal). Once the coordination balance is lost, the positions of transition metal (TM) atoms in the material lattice become unstable and begin to migrate. As the migration process continues, a TM-O-TM coordination structure will gradually form, and this abnormal structure greatly changes the electron conduction path, ion diffusion channel and the overall distribution of electrochemical active sites of the material.

[0005] Most critically, due to the irreversibility of the above structural changes, the sodium ions that have been extracted from the cathode material cannot be smoothly re-inserted into the interior of the cathode material during subsequent charge-discharge cycles. This directly leads to a continuous reduction in the effective capacity of the cathode material during each cycle, resulting in serious irreversible losses, and significantly degrading key performance indicators such as the cycle life, energy density, and charge-discharge efficiency of sodium-ion batteries. This bottleneck problem severely hinders the further application of sodium oxide cathode materials in high-performance sodium-ion batteries. Therefore, there is an urgent need to develop new technical means and material modification strategies to overcome this series of structural degradation and performance attenuation problems under high voltages, in order to promote the sodium-ion battery industry to a new stage of development.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The first object of the present invention is to provide a directionally doped and modified cathode material. By doping element A with an ionic radius similar to that of Na + and no electrochemical activity, which can enter the Na layer through doping to stabilize the layered structure in the high sodium extraction state; at the same time, by doping element G with an ionic radius larger than that of TM (transition metal) and no electrochemical activity, which can enter the TM layer through doping to stabilize the coordination environment of O in the high sodium extraction state, preventing TM from breaking through the octahedral coordination relationship, and thus maintaining the layered structure; in addition, the addition of anion F, the unique F-TM can anchor TM and inhibit TM migration. Therefore, the synergistic effect of these three can improve the electrochemical performance such as capacity, rate, and cycle under high voltages.

[0008] The second object of the present invention is to provide a preparation method for the directionally doped and modified cathode material, which has the advantages of simple operation, short process, and suitability for batch production.

[0009] The third object of the present invention is to provide a cathode sheet, which has the advantages of high capacity, good rate performance, and excellent cycle performance.

[0010] The fourth object of the present invention is to provide a sodium-ion battery, which has a high capacity, high rate performance, and long cycle life.

[0011] To achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0012] The present invention first provides a directionally doped and modified cathode material, and the structural formula of the cathode material is Na x A e Ni a Mn b Cu c Ti d G f O2Fy ; wherein, A includes at least one of K and Ca elements; G includes at least one of Mg, Al, Zn, Sr, Y and Zr elements; 0.85 < x < 0.95, 0.01 < e < 0.05, 0.35 < a < 0.45, 0.3 < b < 0.5, 0.01 < c < 0.15, 0.05 < d < 0.2, 0.01 < f ≤ 0.1, 0.01 ≤ y < 0.1, and a + b + c + d + f = 1.

[0013] Further, the positive electrode material is an O3-type layered oxide positive electrode material.

[0014] Further, in the X-ray diffraction pattern of the positive electrode material, the diffraction angle 2θ of the 003 characteristic peak is 16.5° - 17.0°, the diffraction angle 2θ of the 104 characteristic peak is 41.5° - 42.5°, and the intensity ratio I003 / I104 of the 003 characteristic peak to the 104 characteristic peak is 0.9 - 1.5.

[0015] Further, the morphology of the positive electrode material is a single crystal morphology or a quasi-single crystal morphology.

[0016] Further, the particle size D50 of the positive electrode material is 5 - 7 μm.

[0017] The present invention further provides a preparation method of the above-mentioned directionally doped and modified positive electrode material, including the following steps: mixing a sodium source, a nickel-manganese-copper-titanium precursor, an A-containing additive, a G-containing additive and a fluorine-containing additive, and then performing first sintering and second sintering in sequence.

[0018] Further, the temperature of the first sintering is 900 - 1000 °C.

[0019] Further, the temperature of the second sintering is 880 - 930 °C.

[0020] The present invention also provides a positive electrode sheet, including the above-mentioned directionally doped and modified positive electrode material.

[0021] The present invention further provides a sodium ion battery, including the above-mentioned positive electrode sheet.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the directionally doped and modified positive electrode material provided by the present invention, compared with Na +A, which has a similar ionic radius and is electrochemically inactive, is doped into the Na layer to stabilize the layered structure in the high sodiation state. At the same time, element G, which has an ionic radius larger than that of TM and is electrochemically inactive, is doped into the TM layer to stabilize the coordination environment of O in the high sodiation state, preventing TM from breaking through the octahedral coordination relationship and thus maintaining the layered structure. In addition, the addition of anion F results in a unique F-TM that can anchor TM and inhibit TM migration. Therefore, the synergistic effect of these three components significantly improves the electrochemical performance such as capacity, rate performance, and cycling of the cathode material and the battery prepared therefrom at high voltages (>4.1V). Description of the Drawings

[0023] 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 the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

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

[0025] Figure 2 XRD comparison chart of the cathode material prepared in Example 1 provided by the present invention and the cathode material prepared in Comparative Example 1;

[0026] Figure 3 SEM image of the cathode material prepared in Comparative Example 1 provided by the present invention. Detailed Description of the Embodiments

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, but not all embodiments, and 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. Those conditions not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0028] Unless otherwise specified, in the present invention, "first aspect", "second aspect", "third aspect", "fourth aspect", etc. are for descriptive purposes only, and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. are only for non-exhaustive listing and description purposes, and should be understood not to constitute a closed limitation on quantity.

[0029] Unless otherwise specified, "comprising" and "including" as mentioned in the present invention mean open-ended, and can also be closed-ended. For example, the said "comprising" and "including" can mean that other components not listed can also be included, or it can only include or contain the listed components.

[0030] Unless otherwise specified, in the present invention, "one or more" or "at least one" means any one, any two, or any two or more of the listed items. Among them, "several" means any two or more.

[0031] In a first aspect, the present invention provides a directionally doped and modified cathode material for a sodium-ion battery, and the structural formula of the cathode material is Na x A e Ni a Mn b Cu c Ti d G f O2F y 。

[0032] Among them, A includes at least one of K element and Ca element.

[0033] G includes at least one of Mg, Al, Zn, Sr, Y and Zr elements, and two, three, four or more of them can also be selected.

[0034] 0.85 < x < 0.95, including but not limited to point values such as 0.86, 0.87, 0.88, 0.90, 0.92, 0.94 or range values between any two of them.

[0035] 0.01 < e < 0.05, including but not limited to point values such as 0.02, 0.03, 0.04 or range values between any two of them.

[0036] 0.35 < a < 0.45, including but not limited to point values such as 0.36, 0.37, 0.38, 0.40, 0.41, 0.42, 0.44 or range values between any two of them.

[0037] 0.3 < b < 0.5, including but not limited to the point value 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 or the range value between any two of them.

[0038] 0.01 < c < 0.15, including but not limited to the point value of any one of 0.02, 0.03, 0.05, 0.06, 0.08, 0.10, 0.12, 0.14 or the range value between any two of them.

[0039] 0.05 < d < 0.2, including but not limited to the point value of any one of 0.06, 0.08, 0.10, 0.12, 0.13, 0.15, 0.16, 0.18 or the range value between any two of them.

[0040] 0.01 < f ≤ 0.1, including but not limited to the point value of any one of 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or the range value between any two of them.

[0041] 0.01 ≤ y < 0.1, including but not limited to the point value of any one of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or the range value between any two of them.

[0042] And a + b + c + d + f = 1.

[0043] The positive electrode material is charged to above 4.2V and is in a high sodium - deintercalation state. Due to the reduction of Na in the O - Na - O interlayer, it is not sufficient to support the structural stability. To solve this problem, the present invention conducts doping of element A. Since A has a similar ionic radius to Na + and does not have electrochemical activity, it can enter the Na layer through doping and stabilize the layered structure in the high sodium - deintercalation state.

[0044] Meanwhile, in the high sodium - deintercalation state of the positive electrode material, TM reaches an unstable high oxidation state, and the coordination environment of O changes. TM breaks through the octahedral coordination with O and transfers to a more stable tetrahedral coordination, and the TM - O - Na coordination balance is broken. To solve this problem, the present invention conducts doping of element G. Since the ionic radius of G is larger than that of TM and it does not have electrochemical activity, it can enter the TM layer through doping, stabilize the coordination environment of O in the high sodium - deintercalation state, and prevent TM from breaking through the octahedral coordination relationship, thereby maintaining the layered structure.

[0045] In addition, the addition of anion F, the unique F - TM can anchor TM (transition metal) and inhibit TM migration.

[0046] Therefore, in the present invention, by simultaneously doping A, G, and F, and through their synergistic effects, the electrochemical properties such as capacity, rate performance, and cycle performance of the cathode material and the battery prepared therefrom in a high-voltage (>4.1 V) environment are significantly improved.

[0047] In some specific embodiments, the cathode material is an O3-type layered oxide cathode material.

[0048] 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 17.0°, such as 16.6°, 16.7°, 16.8°, or 16.9°.

[0049] 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°.

[0050] In some specific embodiments, in the X-ray diffraction pattern of the cathode material, the intensity ratio I003 / I104 of the 003 characteristic peak to the 104 characteristic peak is 0.9 to 1.5, such as 1.0, 1.1, 1.2, 1.3, or 1.4.

[0051] In some specific embodiments, the morphology of the cathode material is a single-crystal morphology or a quasi-single-crystal morphology.

[0052] In some specific embodiments, the D50 particle size of the cathode material is 5 to 7 μm, including but not limited to any point value of 5 μm, 5.3 μm, 5.5 μm, 5.8 μm, 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm or the range value between any two of them.

[0053] In a second aspect, the present invention provides a method for preparing the directionally doped and modified cathode material, comprising the following steps: mixing a sodium source, a nickel-manganese-copper-titanium precursor, an A-containing additive, a G-containing additive, and a fluorine-containing additive uniformly, and then performing a first sintering and a second sintering in sequence.

[0054] This preparation method has the advantages of simple operation, short process, and suitability for batch production.

[0055] Among them, the purpose of the first sintering is: preliminary decomposition to release CO2, H2O, etc. in the raw materials, formation of the material unit cell, and crystallization growth. However, the release of decomposition products will generate defects and pores, resulting in affected crystallinity. The purpose of the second sintering is: to complete the remaining solid-phase reaction, continue the crystallization reaction, and promote grain growth and densification.

[0056] Among them, the nickel-manganese-copper-titanium precursor includes, but is not limited to, carbonates of nickel, manganese, copper, and titanium and hydroxides of nickel, manganese, copper, and titanium.

[0057] It can be understood that the additive containing A refers to an additive containing A, including compounds containing A, where A includes at least one of the elements K and Ca.

[0058] It can be understood that the additive containing G refers to an additive containing G, including compounds containing G, where G includes at least one of the elements Mg, Al, Zn, Sr, Y, and Zr.

[0059] Among them, the fluorine-containing additive includes fluorine-containing compounds, such as sodium fluoride, potassium fluoride, magnesium fluoride, or aluminum fluoride.

[0060] It can be understood that the fluorine-containing additive can also be a fluoride of A or a fluoride of G.

[0061] Among them, the sodium source includes sodium-containing compounds, such as sodium carbonate and sodium hydroxide.

[0062] In some specific embodiments, the temperature of the first sintering is 900 - 1000 °C, including, but not limited to, any point value among 910 °C, 920 °C, 930 °C, 950 °C, 960 °C, 970 °C, 980 °C, 990 °C, 1000 °C or a range value between any two of them.

[0063] In some specific embodiments, the heat preservation time of the first sintering is 15 - 20 h, but not limited to this.

[0064] In some specific embodiments, the first sintering is carried out in an air atmosphere or an oxygen atmosphere.

[0065] In some specific embodiments, the heating rate of the first sintering is 1 - 10 °C / min, such as 2 °C / min, 2.5 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, or 8 °C / min.

[0066] In some specific embodiments, the temperature of the second sintering is 880 - 930 °C, including, but not limited to, any point value among 880 °C, 890 °C, 900 °C, 910 °C, 920 °C, 930 °C or a range value between any two of them.

[0067] In some specific embodiments, the heat preservation time of the second sintering is 10 - 14 h, but not limited to this.

[0068] In some specific embodiments, the second sintering is carried out in an air atmosphere or an oxygen atmosphere.

[0069] In some specific embodiments, the heating rate of the second sintering is 1-10 °C / min, such as 2 °C / min, 2.5 °C / min, 3 °C / min, 4 °C / min, 5 °C / min or 8 °C / min.

[0070] In some specific embodiments, the steps of crushing are respectively included after the first sintering and the second sintering.

[0071] In a third aspect, the present invention provides a positive electrode sheet, which includes the directionally doped and modified positive electrode material.

[0072] In some specific embodiments, the positive electrode sheet further includes a binder and a conductive agent, and the present invention does not limit this.

[0073] In a fourth aspect, the present invention provides a sodium ion battery, which includes the positive electrode sheet.

[0074] The sodium ion battery provided by the present invention has the advantages of high capacity, high rate performance and long cycle life.

[0075] 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.

[0076] The embodiments of the present invention will be described in detail below 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 not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. Those reagents or instruments without indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0077] Example 1

[0078] The preparation method of the directionally doped and modified positive electrode material Na 0.93 K 0.01 Ca 0.03 Ni 0.36 Mn 0.38 Cu 0.12 Ti 0.08 Al 0.02 Zr 0.04 O2F 0.03 includes the following steps:

[0079] Calculated according to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.36 Mn 0.38 Cu 0.12 Ti 0.08)CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), Al2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). The above raw materials are mixed using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0080] The mixed raw materials are loaded into a sagger and placed in a high-temperature furnace. Under an air atmosphere, a sintering curve is set. Room temperature is used as the initial temperature, and it is heated at a rate of 3 °C / min to 600 °C and held at 600 °C for 2 h; then it is heated at a rate of 2.5 °C / min to 850 °C and held at 850 °C for 2 h; then it is heated at a rate of 2 °C / min to the target temperature of 990 °C and held at 990 °C for 15 h for the first sintering; then it is cooled at a rate of 2 °C / min to 800 °C, and then naturally cooled.

[0081] The product after the first sintering is subjected to primary air jet milling to obtain a semi-finished product.

[0082] The above semi-finished product is loaded into a ceramic sagger and placed in a high-temperature furnace. Under an air atmosphere, a sintering curve is set. Room temperature is used as the initial temperature, and it is heated at a rate of 3 °C / min to the target temperature of 900 °C and held at 900 °C for 10 h for the second sintering; then it is naturally cooled.

[0083] The product after the second sintering is subjected to secondary air jet milling, and the milling parameters are controlled to obtain a cathode material with a particle size D50 = 6.9 μm.

[0084] 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 shown, it can be seen through Figure 1 that it has a single-crystal-like morphology.

[0085] The XRD pattern of the cathode material prepared in this example is shown in Figure 2 As shown ( Figure 2 is the XRD comparison pattern of the cathode materials of Example 1 and Comparative Example 1), the diffraction angles 2θ and I003 / I104 of the 003 characteristic peak and 104 characteristic peak in the X-ray diffraction (XRD) pattern of the cathode material prepared in this example are shown in Table 1, and the lattice parameter a, lattice parameter c, and unit cell parameter V of this cathode material are shown in Table 1.

[0086] Example 2

[0087] The directionally doped and modified cathode material Na 0.93 K 0.02 Ca 0.02 Ni 0.38 Mn 0.41 Cu 0.05 Ti 0.06Mg 0.02 Al 0.04 Y 0.04 O2F 0.02 The preparation method of

[0088] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.38 Mn 0.41 Cu 0.05 Ti 0.06 )(OH)2, K2CO3 (containing additive A), CaCO3 (containing additive A), MgO (containing additive G), Al2O3 (containing additive G), Y2O3 (containing additive G) and NaF (fluorine-containing additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0089] Put the mixed raw materials into a crucible and place it in a high-temperature furnace. Under an oxygen atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to 600°C at a rate of 3°C / min, hold for 2 hours at 600°C; then heat up to 850°C at a rate of 2.5°C / min and hold for 2 hours at 850°C; then heat up to the target temperature of 910°C at a rate of 2°C / min and hold for 15 hours for the first sintering; then cool down to 800°C at a rate of 2°C / min, and then cool down naturally.

[0090] Perform primary air-flow crushing on the product after the first sintering to obtain a semi-finished product.

[0091] Put the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an oxygen atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to the target temperature of 900°C at a rate of 3°C / min, hold for 10 hours at 900°C for the second sintering; then cool down naturally.

[0092] Perform secondary air-flow crushing on the product after the second sintering, and control the crushing parameters to obtain a cathode material with a particle size D50 = 5.5 μm.

[0093] Example 3

[0094] The cathode material Na 0.94 Ca 0.04 Ni 0.38 Mn 0.36 Cu 0.1 Ti 0.12 Al 0.01 Zr 0.03 O2F 0.06 prepared by the method provided in this example includes the following steps:

[0095] According to the stoichiometric ratio, sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.38 Mn 0.36 Cu 0.1 Ti 0.12 )CO3, CaCO3 (containing additive A), Al2O3 (containing additive G), ZrO2 (containing additive G), and NaF (fluorine-containing 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 sintering reaction.

[0096] The mixed raw materials are loaded into a sagger and placed in a high-temperature furnace. Under an air atmosphere, a sintering curve is set. The normal temperature is used as the initial temperature, and it is heated to 600 °C at a rate of 3 °C / min and held at 600 °C for 2 h; then it is heated to 850 °C at a rate of 2.5 °C / min and held at 850 °C for 2 h; then it is heated to the target temperature of 940 °C at a rate of 2 °C / min and held at 940 °C for 15 h for the first sintering; then it is cooled to 800 °C at a rate of 2 °C / min, and subsequent natural cooling follows.

[0097] The product after the first sintering is subjected to primary air flow pulverization to obtain a semi-finished product.

[0098] The above semi-finished product is loaded into a ceramic sagger and placed in a high-temperature furnace. Under an air atmosphere, a sintering curve is set. The normal temperature is used as the initial temperature, and it is heated to the target temperature of 900 °C at a rate of 3 °C / min and held at 900 °C for 10 h for the second sintering; subsequent natural cooling follows.

[0099] The product after the second sintering is subjected to secondary air flow pulverization, and the pulverization parameters are controlled to obtain a cathode material with a particle size D50 = 5.1 μm.

[0100] Example 4

[0101] The preparation method of the directionally doped and modified cathode material Na 0.9 K 0.01 Ca 0.03 Ni 0.36 Mn 0.4 Cu 0.07 Ti 0.07 Mg 0.02 Zn 0.01 Sr 0.01 Y 0.02 Zr 0.04 O2F 0.01 includes the following steps:

[0102] According to the stoichiometric ratio, sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.36 Mn 0.4 Cu 0.07 Ti 0.07)(OH)2, K2CO3 (containing additive A), CaCO3 (containing additive A), MgO (containing additive G), ZnO (containing additive G), SrCO3 (containing additive G), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0103] Load the mixed raw materials into a sagger and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and raise the temperature to 600 °C at a rate of 3 °C / min, hold for 2 h at 600 °C; then raise the temperature to 850 °C at a rate of 2.5 °C / min, hold for 2 h at 850 °C; then raise the temperature to the target temperature of 900 °C at a rate of 2 °C / min, hold for 15 h at 900 °C for the first sintering; then cool down to 800 °C at a rate of 2 °C / min, and then cool down naturally afterwards.

[0104] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0105] Load the above semi-finished product into a ceramic sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and raise the temperature to the target temperature of 900 °C at a rate of 3 °C / min, hold for 10 h at 900 °C for the second sintering; then cool down naturally afterwards.

[0106] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 6.4 μm.

[0107] Example 5

[0108] The preparation method of the directionally doped and modified cathode material Na 0.9 K 0.02 Ca 0.02 Ni 0.39 Mn 0.42 Cu 0.06 Ti 0.11 Al 0.01 Zr 0.01 O2F 0.06 includes the following steps:

[0109] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.39 Mn 0.42 Cu 0.06 Ti 0.11)CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), Al2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0110] Load the mixed raw materials into a crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to 600 °C at a rate of 3 °C / min, hold at 600 °C for 2 h; then heat up to 850 °C at a rate of 2.5 °C / min, hold at 850 °C for 2 h; then heat up to the target temperature of 1000 °C at a rate of 2 °C / min, hold at 1000 °C for 15 h for the first sintering; then cool down to 800 °C at a rate of 2 °C / min, and then cool down naturally afterwards.

[0111] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0112] Load the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to the target temperature of 900 °C at a rate of 3 °C / min, hold at 900 °C for 10 h for the second sintering; then cool down naturally afterwards.

[0113] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 5.8 μm.

[0114] Example 6

[0115] The preparation method of the directionally doped and modified cathode material Na 0.94 K 0.01 Ca 0.03 Ni 0.4 Mn 0.32 Cu 0.06 Ti 0.15 Mg 0.01 Al 0.02 Sr 0.01 Y 0.02 Zr 0.01 O2F 0.02 includes the following steps:

[0116] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.4 Mn 0.32 Cu 0.06 Ti 0.15)CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), MgO (containing additive G), Al2O3 (containing additive G), SrCO3 (containing additive G), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial for the next high-temperature sintering reaction.

[0117] Load the mixed raw materials into a crucible and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to 600 °C at a rate of 3 °C / min, hold for 2 h at 600 °C; then heat up to 850 °C at a rate of 2.5 °C / min and hold for 2 h at 850 °C; then heat up to the target temperature of 980 °C at a rate of 2 °C / min and hold for 15 h for the first sintering; then cool down to 800 °C at a rate of 2 °C / min, and then cool down naturally afterwards.

[0118] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0119] Load the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to the target temperature of 900 °C at a rate of 3 °C / min, hold for 10 h at 900 °C for the second sintering; then cool down naturally afterwards.

[0120] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 5.7 μm.

[0121] Example 7

[0122] The preparation method of the directionally doped and modified cathode material Na 0.94 K 0.04 Ni 0.4 Mn 0.4 Cu 0.06 Ti 0.1 Al 0.01 Sr 0.01 Y 0.01 Zr 0.01 O2F 0.03 includes the following steps:

[0123] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.4 Mn 0.4 Cu 0.06 Ti 0.1) CO3, K2CO3 (containing additive A), Al2O3 (containing additive G), SrCO3 (containing additive G), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0124] Load the mixed raw materials into a crucible and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. The room temperature is used as the initial temperature, and it is heated to 600 °C at a rate of 3 °C / min, and held at 600 °C for 2 h; then heated to 850 °C at a rate of 2.5 °C / min and held at 850 °C for 2 h; then heated to the target temperature of 950 °C at a rate of 2 °C / min and held at 950 °C for 15 h for the first sintering; then cooled to 800 °C at a rate of 2 °C / min, and then cooled naturally.

[0125] Perform primary air flow pulverization on the product after the first sintering to obtain a semi-finished product.

[0126] Load the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. The room temperature is used as the initial temperature, and it is heated to the target temperature of 900 °C at a rate of 3 °C / min and held at 900 °C for 10 h for the second sintering; then cooled naturally.

[0127] Perform secondary air flow pulverization on the product after the second sintering, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 5.7 μm.

[0128] Example 8

[0129] The preparation method of the directionally doped and modified cathode material Na 0.92 K 0.02 Ca 0.02 Ni 0.42 Mn 0.4 Cu 0.03 Ti 0.0 8Y 0.03 Zr 0.04 O2F 0.06 includes the following steps:

[0130] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.42 Mn 0.4 Cu 0.03 Ti 0.08 )CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0131] Load the above mixed raw materials into a sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Taking room temperature as the initial temperature, heat it at a rate of 3 °C / min to 600 °C, and hold for 2 h at 600 °C; then heat it at a rate of 2.5 °C / min to 850 °C, and hold for 2 h at 850 °C; then heat it at a rate of 2 °C / min to the target temperature of 910 °C, and hold for 15 h at 910 °C for the first sintering; then cool it to 800 °C at a rate of 2 °C / min, and then cool naturally subsequently.

[0132] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0133] Load the above semi-finished product into a ceramic sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Taking room temperature as the initial temperature, heat it at a rate of 3 °C / min to the target temperature of 900 °C, and hold for 10 h at 900 °C for the second sintering; then cool naturally subsequently.

[0134] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 5.9 μm.

[0135] Comparative Example 1

[0136] The preparation method of the cathode material NaNi 0.45 Mn 0.45 Cu 0.05 Ti 0.05 O2 includes the following steps:

[0137] According to the stoichiometric ratio, weigh sodium carbonate (sodium source) and nickel-manganese-copper-titanium precursor (Ni 0.45 Mn 0.45 Cu 0.05 Ti 0.05 )CO3. Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0138] Load the above mixed raw materials into a sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Taking room temperature as the initial temperature, heat it at a rate of 3 °C / min to 600 °C, and hold for 2 h at 600 °C; then heat it at a rate of 2.5 °C / min to 850 °C, and hold for 2 h at 850 °C; then heat it at a rate of 2 °C / min to the target temperature of 950 °C, and hold for 15 h at 950 °C for the first sintering; then cool it to 800 °C at a rate of 2 °C / min, and then cool naturally subsequently.

[0139] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0140] Put the above semi-finished products into ceramic crucibles and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. The room temperature is used as the initial temperature, and the temperature is raised to the target temperature of 900 °C at a rate of 3 °C / min. Hold at 900 °C for 10 h for the second sintering; then cool naturally.

[0141] Perform secondary airflow pulverization on the product after the second sintering, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 5.5 μm.

[0142] The SEM image of the cathode material prepared in this comparative example is shown in Figure 3 as follows.

[0143] The XRD comparison chart of the cathode material prepared in this comparative example and the cathode material prepared in Example 1 is shown in Figure 2 .

[0144] Comparing Figure 1 and Figure 3 it can be seen that Figure 1 the material in Figure 3 is obvious single-crystal particle agglomeration, and the morphology of a single particle is smooth, and no obvious structural defects are found. On the contrary, the material in

[0145] Comparative Example 2

[0146] The preparation method of the cathode material Na 0.92 K 0.02 Ca 0.02 Ni 0.4 Mn 0.45 Cu 0.05 Mg 0.02 Al 0.02 Zn 0.01 Sr 0.0 1Y 0.02 Zr 0.02 O 1.97 F 0.03 includes the following steps:

[0147] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.4 Mn 0.45 Cu 0.05) CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), MgO (containing additive G), Al2O3 (containing additive G), ZnO (containing additive G), SrCO3 (containing additive G), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial for the next high-temperature sintering reaction.

[0148] Load the mixed raw materials into a crucible and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to 600 °C at a rate of 3 °C / min, hold at 600 °C for 2 h; then heat up to 850 °C at a rate of 2.5 °C / min and hold at 850 °C for 2 h; then heat up to the target temperature of 950 °C at a rate of 2 °C / min and hold at 950 °C for 15 h for the first sintering; then cool down to 800 °C at a rate of 2 °C / min and then cool down naturally subsequently.

[0149] Conduct primary air flow pulverization on the product after the first sintering to obtain a semi-finished product.

[0150] Load the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to the target temperature of 900 °C at a rate of 3 °C / min and hold at 900 °C for 10 h for the second sintering; then cool down naturally subsequently.

[0151] Conduct secondary air flow pulverization on the product after the second sintering and control the pulverization parameters to obtain a cathode material with a particle size D50 = 11.8 μm.

[0152] Comparative Example 3

[0153] The preparation method of the cathode material Na 0.92 K 0.02 Ca 0.02 Ni 0.45 Mn 0.4 Ti 0.05 Mg 0.02 Al 0.02 Zn 0.01 Sr 0.0 1Y 0.02 Zr 0.02 O 1.97 F 0.03 includes the following steps:

[0154] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel-manganese-copper-titanium precursor (Ni 0.45 Mn 0.4 Ti 0.05)CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), MgO (containing additive G), Al2O3 (containing additive G), ZnO (containing additive G), SrCO3 (containing additive G), Y2O3 (containing additive G), ZrO2 (containing additive G), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial for the next high-temperature sintering reaction.

[0155] Load the mixed raw materials into a crucible and place them in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to 600 °C at a rate of 3 °C / min, hold for 2 h at 600 °C; then heat up to 850 °C at a rate of 2.5 °C / min and hold for 2 h at 850 °C; then heat up to the target temperature of 950 °C at a rate of 2 °C / min and hold for 15 h for the first sintering; then cool down to 800 °C at a rate of 2 °C / min, and then cool down naturally afterwards.

[0156] Perform primary air-flow pulverization on the product after the first sintering to obtain a semi-finished product.

[0157] Load the above semi-finished product into a ceramic crucible and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat up to the target temperature of 900 °C at a rate of 3 °C / min, hold for 10 h at 900 °C for the second sintering; then cool down naturally afterwards.

[0158] Perform secondary air-flow pulverization on the product after the second sintering and control the pulverization parameters to obtain a cathode material with a particle size D50 = 7.7 μm.

[0159] Comparative Example 4

[0160] The preparation method of the cathode material Na 0.9 K 0.02 Ca 0.04 Ni 0.45 Mn 0.45 Cu 0.05 Ti 0.05 O 1.99 F 0.03 includes the following steps:

[0161] According to the stoichiometric ratio, successively weigh sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.45 Mn 0.45 Cu 0.05 Ti 0.05 )CO3, K2CO3 (containing additive A), CaCO3 (containing additive A), and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial for the next high-temperature sintering reaction.

[0162] Load the above - mixed raw materials into a sagger and place it in a high - temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, heat up to 600 °C at a rate of 3 °C / min, hold for 2 h at 600 °C; then heat up to 850 °C at a rate of 2.5 °C / min, hold for 2 h at 850 °C; then heat up to the target temperature of 950 °C at a rate of 2 °C / min, hold for 15 h for the first sintering; then cool down to 800 °C at a rate of 2 °C / min, and then cool down naturally subsequently.

[0163] Perform primary air - flow pulverization on the product after the first sintering to obtain a semi - finished product.

[0164] Load the above - mentioned semi - finished product into a ceramic sagger and place it in a high - temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, heat up to the target temperature of 900 °C at a rate of 3 °C / min, hold for 10 h at 900 °C for the second sintering; then cool down naturally subsequently.

[0165] Perform secondary air - flow pulverization on the product after the second sintering, and control the pulverization parameters to obtain a cathode material with a particle size D50 = 11.4 μm.

[0166] Comparative Example 5

[0167] The preparation method of the cathode material Na 0.9 K 0.02 Ca 0.02 Ni 0.45 Mn 0.45 Cu 0.05 Ti 0.05 Mg 0.02 Al 002 Zn 001 Sr 001 Y 002 Zr 002 O 211 F 003 includes the following steps:

[0168] Calculate according to the stoichiometric ratio, and successively weigh sodium carbonate (sodium source), nickel - manganese - copper - titanium precursor (Ni 0.45 Mn 0.45 Cu 0.05 Ti 0.05 )CO3, K2CO3 (containing A additive), CaCO3 (containing A additive), MgO (containing G additive), Al2O3 (containing G additive), ZnO (containing G additive), SrCO3 (containing G additive), Y2O3 (containing G additive), ZrO2 (containing G additive) and NaF (containing fluorine additive). Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high - temperature sintering reaction.

[0169] Put the above-mentioned mixed raw materials into a sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, and heat it at a rate of 3 °C / min to 600 °C, and keep it at 600 °C for 2 h; then heat it at a rate of 2.5 °C / min to 850 °C, and keep it at 850 °C for 2 h; then heat it at a rate of 2 °C / min to the target temperature of 950 °C, and keep it at 950 °C for 15 h for the first sintering; then cool it to 800 °C at a rate of 2 °C / min, and then cool it naturally subsequently.

[0170] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0171] Put the above-mentioned semi-finished product into a ceramic sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, and heat it at a rate of 3 °C / min to the target temperature of 900 °C, and keep it at 900 °C for 10 h for the second sintering; then cool it naturally subsequently.

[0172] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 7.2 μm.

[0173] Comparative Example 6

[0174] The preparation method of the cathode material Na 0.93 Ni 0.4 Mn 0.4 Cu 0.05 Ti 0.05 Al 0.02 Y 0.03 Zr 0.04 O 1.96 F 0.03 includes the following steps:

[0175] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), nickel manganese copper titanium precursor ((Ni 0.4 Mn 0.4 Cu 0.05 Ti 0.05 )CO3, Al2O3 (containing G additive), Y2O3 (containing G additive), ZrO2 (containing G additive) and NaF (containing fluorine additive) in sequence. Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0176] Load the above-mentioned mixed raw materials into a sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat it at a rate of 3 °C / min to 600 °C, hold for 2 h at 600 °C; then heat it at a rate of 2.5 °C / min to 850 °C, hold for 2 h at 850 °C; then heat it at a rate of 2 °C / min to the target temperature of 950 °C, hold for 15 h at 950 °C for the first sintering; then cool it to 800 °C at a rate of 2 °C / min, and then cool it naturally subsequently.

[0177] Perform primary air jet milling on the product after the first sintering to obtain a semi-finished product.

[0178] Load the above-mentioned semi-finished product into a ceramic sagger and place it in a high-temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature and heat it at a rate of 3 °C / min to the target temperature of 900 °C, hold for 10 h at 900 °C for the second sintering; then cool it naturally subsequently.

[0179] Perform secondary air jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 8.2 μm.

[0180] Comparative Example 7

[0181] The preparation method of the cathode material Na 0.93 K 0.02 Ca 0.02 Ni 0.4 Mn 0.4 Cu 0.05 Ti 0.05 Y 0.03 Zr 0.04 O 1.97 includes the following steps:

[0182] According to the stoichiometric ratio, weigh sodium carbonate (sodium source), nickel manganese copper titanium precursor (Ni 0.4 Mn 0.4 Cu 0.05 Ti 0.05 )CO3, K2CO3 (containing A additive), CaCO3 (containing A additive), Y2O3 (containing G additive) and ZrO2 (containing G additive) in sequence. Mix the above raw materials using a mixer to make them evenly distributed, which is beneficial to the next high-temperature sintering reaction.

[0183] Load the above - mixed raw materials into a sagger and place it in a high - temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, heat up to 600°C at a rate of 3°C / min, hold for 2 h at 600°C; then heat up to 850°C at a rate of 2.5°C / min, hold for 2 h at 850°C; then heat up to the target temperature of 950°C at a rate of 2°C / min, hold for 15 h at 950°C for the first sintering; then cool down to 800°C at a rate of 2°C / min, and then cool down naturally afterwards.

[0184] Perform primary air - jet milling on the product after the first sintering to obtain a semi - finished product.

[0185] Load the above semi - finished product into a ceramic sagger and place it in a high - temperature furnace. Under an air atmosphere, set the sintering curve. Take room temperature as the initial temperature, heat up to the target temperature of 900°C at a rate of 3°C / min, hold for 10 h at 900°C for the second sintering; then cool down naturally afterwards.

[0186] Perform secondary air - jet milling on the product after the second sintering, and control the milling parameters to obtain a cathode material with a particle size D50 = 9.2 μm.

[0187] The diffraction angles 2θ of the 003 characteristic peak, the diffraction angles 2θ of the 104 characteristic peak, I003 / I104, lattice parameter a, lattice parameter c, and unit cell parameter V in the X - ray diffraction patterns of the cathode materials prepared in Examples 2 - 8 and Comparative Examples 1 - 7 are shown in Table 1 respectively.

[0188] Table 1 Characteristic parameters of each cathode material

[0189]

[0190] Experimental Example

[0191] Preparation of coin cells: Use the cathode materials prepared in each example and each comparative example as active substances respectively. Uniformly mix 0.45 g of active substance, 0.025 g of SP (SP is specifically Super P, a conductive carbon black produced by TIMCAL in Switzerland), and 0.25 g of polyvinylidene fluoride colloidal solution (mass percentage 10%, solute is SOLVAY PVDF5130, solvent is NMP), and then add NMP to make a viscous colloidal solution. Coat this colloidal solution on an aluminum foil with a thickness of 16 μm, and then bake it in a vacuum drying oven at 120°C for 12 h to obtain a positive electrode plate, with an active substance areal density of 5 mg / cm 2. A 300μm thick sodium metal sheet (Aladdin) was used as the counter electrode, a 675μm thick glass fiber (Waterman) was used as the diaphragm, and a 1mol / L NaPF6 solution (the solvent was a mixture of EC and DMC in a volume ratio of 1:1) was used as the electrolyte. A 2032 button cell was assembled in an Ar atmosphere protection glove box. Afterwards, at 25°C, each battery was charged to 4.5V at a constant current of 0.1C (nominal specific capacity 100mAh / g), and then charged at a constant voltage until the current was less than or equal to 0.01mA, then left to stand for 5 minutes, and then discharged to 1.5V at a constant current of 0.1C. This was the activation process of the battery, and subsequent tests were performed after activation.

[0192] The first week 0.1C discharge capacity and 1C discharge capacity tests were performed on each button cell. The test methods are as follows:

[0193] The test method for the first cycle 0.1C discharge capacity is as follows: (1) At 25°C, charge the battery at 0.1C constant current to 4.2V, then charge at constant voltage until the current is less than or equal to 0.01mA, then let it stand for 5 minutes, and then discharge at 0.1C constant current to 2.5V. The discharge capacity at this time is the first cycle discharge capacity.

[0194] The test method of 1C discharge specific capacity is as follows: (1) At 25°C, charge the battery at 0.1C constant current to 4.2V, then charge at constant voltage to a current of less than or equal to 0.01mA, then let it stand for 5 minutes, and then discharge at 1C constant current to 2.5V. The discharge specific capacity at this time is the 1C discharge specific capacity.

[0195] Full battery preparation:

[0196] The positive electrode materials prepared in each embodiment and each comparative example were used as positive electrode active materials to prepare sodium ion batteries according to the following method:

[0197] Preparation of positive electrode slurry: According to the specific mass ratio (positive electrode active material: SP: PVDF = 95:3:2), use an electronic balance to accurately weigh the positive electrode active material, SP and PVDF. First, dissolve PVDF in N-methylpyrrolidone (NMP) and stir it with a vacuum planetary mixer until it is completely dissolved; then add the conductive agent SP to the above solution, stir and disperse it thoroughly; then add the positive electrode active material and continue stirring until a uniform, non-agglomerated positive electrode slurry is formed.

[0198] Preparation of 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). First, dissolve CMC in deionized water and stir with a vacuum planetary mixer until completely dissolved. Then add SBR and SP to the above solution, stir well to mix and disperse; then add the negative electrode active material and continue to stir until a uniform and non-agglomerated negative electrode slurry is formed.

[0199] Preparation of electrode sheets: Use a coater to uniformly coat the positive / negative electrode slurry on the aluminum foil current collector. The surface density is designed with N / P = 1.15, and the control range is ±0.3 g / m 2 . (N / P = (gram capacity of negative electrode active material × negative electrode surface density × negative electrode active material content ratio) ÷ (gram capacity of positive electrode active material × positive electrode surface density × positive electrode active material content ratio)). Dry the current collector coated with the slurry, remove the solvents NMP / deionized water. The dried electrode sheets are rolled by a rolling press, and then the electrode sheets are cut into the required width using a slitter and into the required length using a punching machine.

[0200] Preparation of electrolyte: Dissolve NaPF6 in a mixed solvent of EC, DMC, and FEC to prepare a 1 mol / L solution.

[0201] 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.

[0202] Battery formation: Conduct the first charge-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.

[0203] After the battery formation is completed, the cycle performance of each full battery is tested respectively according to the following method: Use a battery charge-discharge tester for testing, and the set conditions are as follows:

[0204] a) 0.1C - DC to 1.5V;

[0205] b) Put 10min;

[0206] c) 1C - CC to 4.2V, CV to 0.05C;

[0207] d) Put 10min;

[0208] e) 1C - DC to 1.5V;

[0209] f) Set b to e as n Cycles;

[0210] g) End;

[0211] The discharge capacity mAh of step e at different cycle numbers n is divided by the discharge capacity mAh of the first cycle to obtain the cycle retention rate % of the battery.

[0212] The test results of each electrochemical performance are shown in Table 2.

[0213] Table 2 Test Results of Electrochemical Performance

[0214]

[0215] It can be seen from Table 1 that the sodium ion batteries assembled with the cathode materials prepared in each example have high capacity, good rate performance, and excellent cycle performance.

[0216] However, for the cathode materials prepared in each comparative example, due to the absence of doping with A, G, F, or not conforming to the structural formula Na x A e Ni a Mn b Cu c Ti d G f O2F y , the capacity, rate performance, and cycle performance decrease.

[0217] It can be seen that by using the cathode material with a specific structural formula and doping with A, G, and F simultaneously, the synergistic effect of these three can significantly improve the capacity, rate performance, and cycle performance of the cathode material at high voltage (>4.1V).

[0218] 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 to limit 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 the embodiments of the present invention; therefore, this means that all such replacements and modifications belonging to the scope of the present invention are included in the appended claims.

Claims

1. The cathode material modified by directional doping, characterized in that, The structural formula of the positive electrode material is Na x A e Ni a Mn b Cu c Ti d G f O2F y ; Among them, A includes at least one of K and Ca elements; G includes at least one of Mg, Al, Zn, Sr, Y and Zr elements; 0.85 < x < 0.95, 0.01 < e < 0.05, 0.35 < a < 0.45, 0.3 < b < 0.5, 0.01 < c < 0.15, 0.05 < d < 0.2, 0.01 < f ≤ 0.1, 0.01 ≤ y < 0.1, and a + b + c + d + f = 1.

2. The directionally doped and modified cathode material according to claim 1, wherein The positive electrode material is an O3-type layered oxide positive electrode material.

3. The cathode material with directional doping modification 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 17.0°, the diffraction angle 2θ of the 104 characteristic peak is 41.5° to 42.5°, and the intensity ratio I003 / I104 of the 003 characteristic peak to the 104 characteristic peak is 0.9 to 1.

5.

4. The positively charged electrode material modified by directional doping according to claim 1, characterized in that, The morphology of the positive electrode material is a single crystal morphology or a pseudo single crystal morphology.

5. The directionally doped and modified cathode material according to claim 1, wherein The particle size D50 of the positive electrode material is 5 to 7 μm.

6. The preparation method of the directionally doped and modified cathode material according to any one of claims 1 to 5, characterized in that, It includes the following steps: mixing a sodium source, a nickel manganese copper titanium precursor, an A-containing additive, a G-containing additive and a fluorine-containing additive, and then performing first sintering and second sintering in sequence.

7. The preparation method of the directionally doped and modified cathode material according to claim 6, characterized in that, The temperature of the first sintering is 900 to 1000 °C.

8. The preparation method of the directionally doped and modified cathode material according to claim 6, wherein, The temperature of the second sintering is 880 to 930 °C.

9. The positive electrode sheet is characterized in that, It includes the directionally doped and modified positive electrode material according to any one of claims 1 to 5.

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

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