A p2-type sodium ion battery positive electrode material and a preparation method and application thereof

Abstract

The application discloses a P2-type sodium ion battery positive electrode material and a preparation method and application thereof, and relates to a P2-type sodium ion battery positive electrode material Na x Ni a Cu b Fe c Mn d Ti e M f O2, which involves multiple elements, utilizes the synergistic effect of the multiple elements and takes into account the different functions of the elements, and simply and quickly realizes component optimization and performance improvement of the P2-type layered oxide; the preparation method is simple and convenient to operate; the prepared P2-type sodium ion battery positive electrode material is used for preparing a sodium ion battery, has very excellent cycle stability and fast charging capacity, is suitable for industrialized production, and has a good application prospect in the field of sodium ion batteries, especially fast-charging sodium ion batteries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a P2-type sodium ion battery positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Sodium ion batteries have the advantages of rich sodium resources, wide distribution and low cost, and have good application prospects in the field of large-scale energy storage. As the main source of sodium in sodium ion batteries, the positive electrode material directly determines the energy density of the sodium ion battery, and the structural stability of the positive electrode material in the charging and discharging process affects the cycle and rate performance of the battery. Therefore, it is crucial to develop a positive electrode material with high capacity, cycle stability and excellent fast charging performance.

[0003] Among the many positive electrode materials, P2-type layered oxides have high theoretical capacity and easy sodium ion diffusion transmission paths, and are suitable for application in fast-charging sodium ion batteries. However, P2-type materials will undergo irreversible P2-O2 phase transition when charged to high voltage, which seriously reduces the cycle stability of P2-type layered oxides; and various sodium / vacancy ordered structures will appear during the charging and discharging process, resulting in a decrease in the fast-charging performance of the material. For example, Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 ]O2, the reversible specific capacity can reach 150 mAh / g at 2.0-4.5 V, but the in-situ XRD results show that the platform at about 4.1 V corresponds to the P2-O2 phase transition, accompanied by a large volume change, thereby causing rapid attenuation of the specific capacity. Researchers have used element substitution / doping methods to suppress the ordered structures and irreversible phase transitions of P2-type layered oxides during the charging and discharging process, thereby improving the cycle and rate performance of P2 layered oxides. Komaba et al. obtained Na 2 / 3 [Ni 1 / 3 Mn 1 / 2 Ti 1 / 6 ]O2 by doping Ti to replace part of Mn, and the cycle performance was improved to a certain extent, but the reversible specific capacity decreased. In the prior art, one or two elements are gradually replaced to improve some performance, but it is difficult to comprehensively and quickly improve the overall performance of sodium ion batteries. SUMMARY

[0004] In view of the above technical problems existing in the prior art, the application provides a P2-type sodium ion battery positive electrode material and a preparation method and application thereof, which can accurately control the content range of different elements and comprehensively improve the capacity, cycle and rate performance of sodium ion batteries.

[0005] To achieve the above application purposes, the technical scheme adopted by the application is as follows: a P2-type sodium ion battery positive electrode material, whose chemical formula is: Na x Nia Cu b Fe c Mn d Ti e M f O2, wherein M is one or more of Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+ , 0.6≤x≤0.75, 0.15≤a≤0.35, 0.02≤b≤0.15, 0.02≤c≤0.2, 0.25≤d≤0.45, 0.1≤e≤0.3, 0≤f≤0.1, a+b+c+d+e+f=1.

[0006] The application further provides a preparation method of the P2-type sodium ion battery positive electrode material, and the preparation method is a solid phase method.

[0007] Further, the preparation method of the P2-type sodium ion battery positive electrode material comprises the following steps:

[0008] (1) A proper amount of sodium salt, nickel oxide, copper oxide, iron oxide, manganese dioxide, titanium dioxide and M oxide are taken in proportion and mixed into a precursor;

[0009] (2) The precursor is placed in a muffle furnace for low-temperature sintering, taken out, ground and then high-temperature sintered;

[0010] (3) The sintered powder is ground to obtain the P2-type sodium ion battery positive electrode material.

[0011] Further, in the step (1), the sodium salt is sodium carbonate or sodium nitrate.

[0012] Further, in the step (2), the precursor powder is placed in a muffle furnace, sintered at 100-500℃ for 1-5h, taken out, fully ground and then sintered at 800-1100℃ for 12-24h.

[0013] The application further provides a preparation method of the P2-type sodium ion battery positive electrode material, and the preparation method is a sol-gel method.

[0014] Further, the preparation method of the P2-type sodium ion battery positive electrode material comprises the following steps:

[0015] (1) the stoichiometric salt of the required sodium, the salt of the required element of the electrode material and the salt of the doping element M are dissolved and mixed according to the stoichiometric ratio to form a precursor solution;

[0016] (2) the precursor solution is stirred under heating conditions, a chelating agent is added and evaporated to form a precursor gel;

[0017] (3) the precursor gel is placed in a crucible, pre-fired at low temperature and then heat-treated at high temperature to obtain a precursor powder;

[0018] (4) the precursor powder is ground to obtain a P2-type sodium ion battery positive electrode material.

[0019] Further, in the step (1), the stoichiometric salt of sodium is one of 100wt%-108wt% sodium acetate, sodium nitrate, sodium carbonate or sodium sulfate; the required element of the electrode material of the doping element is nickel, copper, iron, manganese, titanium; the doping element M is one or more of Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+ ; and the salt is nitrate or sulfate.

[0020] Further, in the step (2), the heating temperature is 50℃-100℃.

[0021] Further, in the step (3), the heating temperature is 100℃-500℃ for 2h; the heat treatment is at 600℃-1000℃ for 2-24h.

[0022] Further, the P2-type sodium ion battery positive electrode material is a P2-type sodium ion battery layered oxide positive electrode material.

[0023] The application also provides the application of the P2-type sodium ion battery positive electrode material, which is used as an active substance of a battery positive electrode material for the preparation of a sodium ion battery.

[0024] The technical scheme of the application has the beneficial effects that a P2-type sodium ion battery positive electrode material, Na x Ni a Cu b Fe c Mn d Ti e M fO2, and the content of each element is limited accordingly; the material of the application involves multiple elements, wherein Fe and Mn are abundant and low in cost, and Fe can be removed from the transition metal layer to the sodium layer during preparation, thereby ultimately reducing the cycle stability of the material; to inhibit the migration of Fe and ensure that the layered oxide has sufficient charge compensation, the application adds Ni during preparation, and the multi-electron redox reaction of Ni 3+ / Fe 4+ The redox reaction provides a certain capacity for the material, and if the content of Fe 4+ in the material is too high, Fe 4+ will migrate from the transition metal layer to the sodium layer, ultimately reducing the cycle stability of the material; to inhibit the migration of Fe 4+ and ensure that the layered oxide has sufficient charge compensation, the application adds Ni during preparation, and the multi-electron redox reaction of Ni 2+ / Ni 3+ / Ni 4+ provides high capacity for the material, and the content of Ni is strictly controlled to avoid the presence of NiO impurities; the addition of Cu with variable valence further improves the stability of the material in air while ensuring high capacity; however, the solid solubility of Cu is not high, so the amount of Cu doping needs to be controlled. In addition, part of the Mn 4+ in the application is replaced by Ti 4 + , which can inhibit the Jahn-Teller effect caused by the variable valence of Mn and help improve the structural stability and cycle stability of the material, but too much Ti will reduce the cycle stability of the material. Therefore, the application adds a small amount of other electrochemically inert elements during preparation to further enhance the structural stability of the material under high rate and long cycle. The application utilizes the synergistic effect of multiple elements and the different functions of the elements, effectively selects the corresponding elements and controls the content of each element, and can simply and quickly realize the component optimization and performance improvement of P2-type layered oxides; the preparation method of the application is simple and easy to operate, and the P2-type sodium ion battery cathode material prepared by the method has very excellent cycle stability and fast charging capacity, is suitable for industrial production, and has good application prospects in the field of sodium ion batteries, especially fast-charging sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a P2-type material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 O2 prepared by the second embodiment of the application;

[0026] Figure 2 is a P2-type material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn0.4 Ti 0.2 SEM image of O2;

[0027] Figure 3 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Two of the present invention 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 Rate capability plot of O2;

[0028] Figure 4 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Two of the present invention 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 Cycle capacity plot of O2 at 0.5C rate;

[0029] Figure 5 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Three of the present invention 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 Rate capability plot of O2;

[0030] Figure 6 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Three of the present invention 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 Cycle capacity plot of O2 at 2C rate;

[0031] Figure 7 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Four of the present invention 0.7 Ni 0.23 Cu 0.05 Fe 0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 Rate capability plot of O2;

[0032] Figure 8 Na0.7Mn0.5Ti0.5O2 is a P2-type material prepared in Example Four of the present invention 0.7 Ni 0.23 Cu 0.05 Fe 0.08Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 Cycle capacity graph of O2 at 0.5C rate;

[0033] Figure 9 Na material prepared in the present application Comparative Example 1 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 XRD pattern of O2;

[0034] Figure 10 Na material prepared in the present application Comparative Example 1 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 Cycle capacity graph of O2 at 0.5C rate;

[0035] Figure 11 P2 type Na material prepared in the present application Comparative Example 2 0.7 Ni 0.25 Cu 0.05 Fe 0.1 Mn 0.15 Ti 0.45 Cycle capacity graph of O2 at 0.5C rate. DETAILED DESCRIPTION

[0036] The present application will be described in detail below in conjunction with the accompanying drawings and examples.

[0037] Example 1

[0038] The present application provides a P2 type sodium ion battery cathode material, which has a chemical formula of: Na x Ni a Cu b Fe c Mn d Ti e M f O2, wherein M is Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+One or more of the following elements are used: 0.6≤x≤0.75, 0.15≤a≤0.35, 0.02≤b≤0.15, 0.02≤c≤0.2, 0.25≤d≤0.45, 0.1≤e≤0.3, 0≤f≤0.15, and a+b+c+d+e+f=1. This invention also employs a multi-element P2-type sodium-ion battery cathode material, limiting the content of each element and controlling the ratio between them. By utilizing the synergistic effect of multiple elements and considering their different functions, the composition optimization and performance improvement of P2-type layered oxides are achieved simply and quickly.

[0039] This invention also provides a method for preparing the P2 type sodium-ion battery cathode material, wherein the preparation method is a solid-state method.

[0040] Preferably, the preparation method of the P2 type sodium-ion battery cathode material includes the following steps:

[0041] (1) Take appropriate amounts of sodium salt, nickel oxide, copper oxide, iron oxide, manganese dioxide, titanium dioxide and oxide of M in proportion and mix them to form a precursor;

[0042] (2) The precursor is placed in a muffle furnace for low-temperature sintering, then removed, ground, and sintered at high temperature; the present invention implements low-temperature preheating sintering to further mix the elements evenly.

[0043] (3) The sintered sample was ground to obtain the P2 type sodium-ion battery cathode material.

[0044] Preferably, in step (1), the sodium salt is sodium carbonate or sodium nitrate.

[0045] Preferably, in step (2), the precursor powder is placed in a muffle furnace and sintered at 100-500℃ for 1-5 hours, then taken out and ground thoroughly, and then sintered at 800-1100℃ for 12-24 hours.

[0046] The present invention also provides a method for preparing the P2 type sodium-ion battery cathode material, wherein the preparation method is a sol-gel method.

[0047] Preferably, the preparation method of the P2 type sodium-ion battery cathode material includes the following steps:

[0048] (1) Dissolve and mix the required sodium salt, the salt of the element required for the electrode material, and the salt of the dopant element M in stoichiometric ratio to form a precursor solution.

[0049] (2) Stir the precursor solution under heating conditions, add chelating agent and evaporate to dryness to form precursor gel;

[0050] (3) The precursor gel is placed in a crucible, pre-calcined at low temperature and then heat-treated at high temperature to obtain precursor powder;

[0051] (4) grinding the precursor powder to obtain a P2-type sodium-ion battery positive electrode material.

[0052] Further, in the step (1), the stoichiometric salt of sodium is one of 100wt%-108wt% sodium acetate, sodium nitrate, sodium carbonate or sodium sulfate; the required element of the doped element electrode material is nickel, copper, iron, manganese, titanium; the doped element M is one or more of Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+ ; and the salt is nitrate or sulfate.

[0053] Preferably, in the step (2), the heating temperature is 50℃-100℃.

[0054] Preferably, in the step (3), the heating temperature is 100℃-500℃, and the time is 2h; the heat treatment temperature is 600℃-1000℃, and the time is 2-24h.

[0055] Preferably, the P2-type sodium-ion battery positive electrode material is a P2-type sodium-ion battery layered oxide positive electrode material.

[0056] Example Two

[0057] The P2-type sodium-ion battery positive electrode material is prepared by the solid phase method of the example one of the present application, Na2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), Fe2O3 (analytical pure), MnO2 (analytical pure), TiO2 (analytical pure) are mixed according to the required stoichiometric ratio; grinding in an agate mortar for half an hour to obtain a precursor; the precursor is treated at 300℃ for 3 hours in a muffle furnace, taken out, ground again and treated at 950℃ for 15 hours in a muffle furnace to obtain a brown powder of P2-type material Na 0.7 Ni 0.23 Cu 0.0 7Fe 0.1 Mn 0.4 Ti 0.2 O2.

[0058] Referring to the accompanying Figure 1 , the material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti0.2 O2 crystal structure is a P2 type layered structure oxide.

[0059] Referring to the drawings Figure 2 , the P2 type material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 O2 prepared in the embodiment of the present application is a block material.

[0060] The P2 type material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 O2 prepared in the embodiment of the present application is used as an active material of a battery positive electrode material for the preparation of a sodium ion battery. The Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 O2 powder prepared in the embodiment of the present application is mixed with a conductive agent (carbon nanotube) and a binder (PVDF) in a mass ratio of 8:1:1, and the slurry is uniformly coated on a current collector aluminum foil in a dry environment at room temperature, and is dried at 120°C for 10 hours under vacuum conditions, and is cut into an electrode sheet and is transferred to a glove box for standby. The assembly of a simulation battery is performed in an Ar atmosphere glove box, a metal sodium is used as a counter electrode, and a NaClO4 / diethyl carbonate (EC:DEC) solution is used as an electrolyte, and a CR2032 button cell is assembled.

[0061] A constant current charge and discharge mode is used, and charge and discharge tests are performed at different current densities of 0.1C-10C. The performance is tested under the condition that the discharge cut-off voltage is 2V and the charge cut-off voltage is 4.2V.

[0062] Referring to the drawings Figure 3 , the P2 type material Na 0.7 Ni 0.23 Cu 0.07 Fe 0.1 Mn 0.4 Ti 0.2 O2 prepared in the embodiment of the present application has a specific capacity of 112mAh / g, and has a capacity retention rate of 59% at a 10C rate.

[0063] Referring to the drawings Figure 4 , the P2 type material Na 0.7 Ni 0.23 Cu 0.07Fe 0.1 Mn 0.4 Ti 0.2 The capacity retention rate of the battery 100 prepared by O2 after 100 weeks is 95.2%, and the battery has excellent electrochemical comprehensive performance.

[0064] Example three

[0065] The P2 type sodium ion battery positive electrode material is prepared by the solid phase method in the embodiment one of the application, Na2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), Fe2O3 (analytical pure), MnO2 (analytical pure), TiO2 (analytical pure), and MgO (analytical pure) are mixed according to the required stoichiometric ratio; the mixture is ground in a agate mortar for half an hour to obtain a precursor; the precursor is treated at 300 DEG C in a muffle furnace for 3 hours, and then ground and treated again at 1000 DEG C in a muffle furnace for 15 hours to obtain a brown powder of the P2 type material Na 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 O2.

[0066] The P2 type material Na 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 O2 prepared in the embodiment of the application is used as an active substance of a battery positive electrode material for the preparation of a sodium ion battery. 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 O2 powder is mixed with a conductive agent (carbon nanotube) and a binder (PVDF) according to a mass ratio of 8:1:1, the slurry is uniformly coated on a current collector aluminum foil in a dry environment at room temperature, and the slurry is dried at 120 DEG C for 10 hours under vacuum conditions, and then the slurry is cut into electrode pieces and transferred to a glove box for standby. The assembly of a simulation battery is carried out in an Ar atmosphere glove box, metal sodium is used as a counter electrode, and a NaClO4 / carbonic acid diethyl ester (EC:DEC) solution is used as an electrolyte, and a CR2032 button cell is assembled.

[0067] The constant current charge and discharge mode is used, and the charge and discharge test is carried out at different current densities of 0.1C-10C. The discharge cut-off voltage is 2V, and the charge cut-off voltage is 4.2V, and the performance is tested.

[0068] See attached document Figure 5 The P2 type material Na in this embodiment of the invention 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 The battery prepared with O2 has a specific capacity of 116 mAh / g and a capacity retention of 52% at a 10C rate.

[0069] See attached document Figure 4 Cycling performance was tested at a 2C rate for the P2 type material Na in this embodiment of the invention. 0.7 Ni 0.22 Cu 0.04 Fe 0.1 Mn 0.4 Ti 0.2 Mg 0.04 The battery prepared with O2 retained 98.3% of its capacity after 100 cycles, demonstrating excellent overall electrochemical performance.

[0070] Example 4

[0071] The P2-type sodium-ion battery cathode material was prepared using the solid-state method described in Example 1 of this invention. Na₂CO₃ (analytical grade), NiO (analytical grade), CuO (analytical grade), Fe₂O₃ (analytical grade), MnO₂ (analytical grade), TiO₂ (analytical grade), MgO (analytical grade), and SnO₂ (analytical grade) were mixed in the required stoichiometric ratio. The mixture was then ground in an agate mortar for half an hour to obtain a precursor. The precursor was then treated in a muffle furnace at 300°C for 3 hours, ground again, and then treated again in a muffle furnace at 1000°C for 15 hours to obtain a brown powder of the P2-type material Na. 0.7 Ni 0.23 Cu 0.05 Fe 0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 O2.

[0072] The embodiments of the present invention will prepare P2 type material Na 0.7 Ni 0.23 Cu 0.05 Fe 0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 O2 is used as an active material in the positive electrode of a battery in the preparation of sodium-ion batteries. The Na2 prepared in the embodiments of this invention... 0.7 Ni 0.23 Cu 0.05 Fe0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 O2 powder and conductive agent (carbon nanotubes), binder (PVDF) are mixed in a mass ratio of 8:1:1, and the slurry is uniformly coated on the current collector aluminum foil in a dry environment at room temperature. After drying at 120°C for 10 hours under vacuum conditions, the electrode sheet is cut and transferred to the glove box for standby. The assembly of the simulation battery is carried out in an Ar atmosphere glove box, using metallic sodium as the counter electrode, and NaClO4 / carbonic acid diethyl ester (EC:DEC) solution as the electrolyte, to assemble CR2032 button cell.

[0073] The constant current charge and discharge mode is used to carry out charge and discharge test at different current densities of 0.1C-10C. The performance is tested under the condition that the discharge cut-off voltage is 2V and the charge cut-off voltage is 4.2V.

[0074] Referring to the accompanying drawings, Figure 7 , the specific capacity of the battery prepared by the P2 type material Na 0.7 Ni 0.23 Cu 0.05 Fe 0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.0 O2 is 121mAh / g, and the capacity retention rate is 70% at 10C rate.

[0075] Referring to the accompanying drawings, Figure 8 , the cycle performance is tested at 0.5C rate, and the P2 type material Na 0.7 Ni 0.23 Cu 0.05 Fe 0.08 Mn 0.44 Ti 0.15 Mg 0.03 Sn 0.02 O2 prepared by the embodiment of the present application has a capacity retention rate of 98% after 100 cycles, and has excellent electrochemical comprehensive performance.

[0076] Comparative Example One

[0077] The sodium ion battery cathode material is prepared by the solid phase method of the first embodiment of the present application, Na2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), Fe2O3 (analytical pure), MnO2 (analytical pure), TiO2 (analytical pure) are mixed according to the required stoichiometric ratio; grind in a agate mortar for half an hour to obtain a precursor; the precursor is treated in a muffle furnace at 300°C for 3 hours, taken out and ground again, and then treated in a muffle furnace at 950°C for 15 hours to obtain a brown powder material Na0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 O2.

[0078] Referring to the drawings Figure 9 , the material Na 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 O2 prepared in the comparative example of the present application has a mixed phase layered structure of P2 and other phases, indicating that the material structure is prone to change when the Fe content is too high, reducing the purity of the P2 type structure.

[0079] The material Na 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 O2 prepared in the comparative example of the present application is used as an active material for a battery positive electrode material for the preparation of a sodium ion battery. 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25 O2 powder prepared in the example of the present application is mixed with a conductive agent (carbon nanotube) and a binder (PVDF) in a mass ratio of 8:1:1, and the slurry is uniformly coated on a current collector aluminum foil in a dry environment at room temperature. After drying at 120°C for 10 hours under vacuum conditions, the electrode sheet is cut and transferred to a glove box for standby. The assembly of the simulation battery is carried out in an Ar atmosphere glove box, using metallic sodium as the counter electrode, and NaClO4 / carbonic acid diethyl ester (EC:DEC) solution as the electrolyte, to assemble a CR2032 button cell.

[0080] The constant current charge and discharge mode is used to test the charge and discharge at different current densities. The performance is tested under the conditions that the discharge cut-off voltage is 2V and the charge cut-off voltage is 4.2V.

[0081] Referring to the drawings Figure 10 , the material Na 0.7 Ni 0.15 Cu 0.05 Fe 0.3 Mn 0.25 Ti 0.25The capacity retention rate of the battery prepared by the O2 is only 63.9% after 100 cycles, indicating that the cycle stability of the material significantly decreases when the content of Fe exceeds the limit range of the first embodiment of the application. Meanwhile, the rate performance of the material also significantly decreases compared with the second to fourth embodiments, and the capacity retention rate is only 32% at a 5C rate and only 14% at a 10C rate.

[0082] Comparative Example Two

[0083] The Na 0.7 Ni 0.25 Cu 0.05 Fe 0.1 Mn 0.15 Ti 0.45 O2 was prepared by the same method as the first comparative example, and the battery was assembled by using the same electrode sheet and battery preparation method.

[0084] The constant current charge and discharge mode was used to perform the charge and discharge test at different current densities. The performance was tested under the condition that the discharge cut-off voltage was 2V and the charge cut-off voltage was 4.2V.

[0085] Referring to the accompanying drawings Figure 11 The cycle performance was tested at a 0.5C rate. The P2-type material Na 0.7 Ni 0.25 Cu 0.05 Fe 0.1 Mn 0.15 Ti 0.45 The capacity retention rate of the battery prepared by the O2 is only 63.9% after 100 cycles, indicating that the cycle stability of the material significantly decreases when the content of Fe exceeds the limit range of the first embodiment of the application. Meanwhile, the rate performance of the material also significantly decreases compared with the second to fourth embodiments, and the capacity retention rate is only 32% at a 5C rate and only 14% at a 10C rate.

[0086] Comparative Example Three

[0087] The positive electrode material Na 0.7 Ni 0.3 Fe 0.1 Mn 0.6 O2 was prepared by the method of the first comparative example, and the battery was assembled by using the same electrode sheet and battery preparation method.

[0088] The constant current charge and discharge mode was used to perform the charge and discharge test at different current densities. The performance was tested under the condition that the discharge cut-off voltage was 2V and the charge cut-off voltage was 4.2V.

[0089] The cycle performance was tested at a 0.5C rate. The P2-type material Na 0.7 Ni 0.3 Fe 0.1 Mn 0.6The capacity retention rate of the battery prepared by O2 is 85.1% after 100 cycles. Its rate performance is tested, and the capacity retention rate is only 23% at a 5C rate and only 5% at a 10C rate. In this comparative example, only three transition metal elements, Ni, Fe, and Mn, are present, and compared to the P2-type sodium-ion battery cathode material of the present application containing more than five elements, the cycle and rate performance of the comparative example are both significantly decreased.

[0090] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Thus, it is intended that the present application cover the modifications and changes as they come within the scope of the claims and the equivalents of the claims.

Claims

1. A P2-type sodium-ion battery cathode material, characterized in that, The P2 type sodium ion battery positive electrode material has a chemical formula of: Na x Ni a Cu b Fe c Mn d Ti e M f O2; wherein M is one or more of Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+ , 0.6≤x≤0.75, 0.22≤a≤0.35, 0.02≤b≤0.15, 0.02≤c≤0.2, 0.25≤d≤0.45, 0.15≤e≤0.3, 0≤f≤0.15, a+b+c+d+e+f=1.

2. A method for preparing the P2-type sodium-ion battery cathode material of claim 1, characterized by, The preparation method of the P2 type sodium ion battery cathode material is a solid phase method or a sol-gel method.

3. A method for preparing the P2-type sodium-ion battery cathode material of claim 1, characterized by, The method comprises the following steps: (1) taking a proper amount of sodium salt, nickel oxide, copper oxide, iron oxide, manganese dioxide, titanium dioxide and M oxide according to the proportion to mix into a precursor; (2) placing the precursor in a muffle furnace for low-temperature sintering, taking out, grinding and then high-temperature sintering; (3) Take the sintered powder grinding, get P2 type sodium ion battery positive material Na x Ni a Cu b Fe c Mn d Ti e M f O2.

4. The method for preparing the P2-type sodium-ion battery cathode material according to claim 3, characterized in that, In the step (1), the sodium salt is sodium carbonate or sodium nitrate.

5. The method for preparing the P2-type sodium-ion battery cathode material according to claim 3, characterized in that, In the step (2), the precursor powder is placed in a muffle furnace, sintered at 100-500 DEG C for 1-5h, taken out, ground, and then sintered at 800-1100 DEG C for 12-24h.

6. A method of preparing the P2-type sodium-ion battery cathode material of claim 1, characterized by, The method comprises the following steps: (1) dissolving and mixing stoichiometrically required sodium salt, electrode material required element salt and doped element M salt into a precursor solution according to the stoichiometric ratio; (2) stirring the precursor solution under heating, adding a chelating agent and evaporating to form a precursor gel; (3) placing the precursor gel in a crucible, pre-sintering at low temperature and then high-temperature heat treatment to obtain a precursor powder; (4) grinding the precursor powder to obtain a P2 type sodium ion battery cathode material.

7. The method for preparing the P2-type sodium-ion battery cathode material according to claim 6, characterized in that, In the step (1), the stoichiometric salt of sodium is one of 100wt%-108wt% sodium acetate, sodium nitrate, sodium carbonate or sodium sulfate; the required element of the electrode material is nickel, copper, iron, manganese, titanium; the doping element M is one or more of Li + , Mg 2+ , Zn 2+ , Al 3+ , Co 3+ , Sn 4+ , V 4+ , Zr 4+ , La 3+ , Nb 5+ ; and the salt is nitrate or sulfate.

8. The method for preparing the P2-type sodium-ion battery cathode material according to claim 6, characterized in that, In the step (2), the heating temperature is 50 DEG C-100 DEG C.

9. The method for preparing the P2-type sodium-ion battery cathode material according to claim 6, characterized in that, In the step (3), the low-temperature pre-sintering temperature is 100 DEG C-500 DEG C, and the time is 2h; the heat treatment temperature is 600 DEG C-1000 DEG C, and the time is 2-24h.

10. Use of the P2 sodium-ion battery cathode material of claim 1, characterized in that, The active substance used as the battery cathode material is used for preparing a sodium ion battery.

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