Positive electrode material, sodium-ion battery and electric device

Abstract

The embodiment of the application discloses a kind of positive electrode material, sodium ion battery and electric equipment. Positive electrode material includes positive electrode material particle, the positive electrode material particle has core-shell structure, the core includes P2 phase layer oxide, the shell includes O3 phase layer oxide, further can make O3 phase layer oxide provide sufficient active sodium ion for sodium ion battery, to improve the first coulomb efficiency of sodium ion battery, simultaneously, due to the crystal structure of O3 phase layer oxide is stable and electrochemical performance is reversible, can be dried and regenerated after absorbing water in environment, and the inner core includes P2 phase layer oxide, further guarantee that sodium ion battery has excellent rate performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a positive electrode material, a sodium ion battery and an electric device. BACKGROUND

[0002] A sodium ion battery is a kind of secondary battery, which mainly relies on the movement of sodium ions between the positive electrode and the negative electrode to work. The working principle of the sodium ion battery is similar to that of the lithium ion battery. When charging, sodium ions are extracted from the positive electrode, embedded into the negative electrode through the electrolyte, and the compensation charge of the electrons is supplied to the negative electrode through the external circuit to ensure the charge balance of the positive and negative electrodes. When discharging, the sodium ions are extracted from the negative electrode and embedded into the positive electrode through the electrolyte.

[0003] Due to the abundant reserves, wide distribution, low cost, no development bottleneck and environmental friendliness of sodium, and the fact that the sodium ion battery can be compatible with the existing production equipment of the lithium ion battery, and the sodium ion battery has good power characteristics, wide temperature range adaptability, safety performance and no over-discharge problem, and the positive and negative electrodes of the sodium ion battery can be constructed into a bipolar battery using aluminum foil current collector to further improve the energy density of the sodium ion battery. However, the existing sodium ion battery cannot have high first coulomb efficiency and excellent rate performance at the same time.

[0004] Therefore, how to provide a sodium ion battery with high first coulomb efficiency and excellent rate performance is a technical problem to be solved at present. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a positive electrode material, a sodium ion battery and an electric device, so that the sodium ion battery has high first coulomb efficiency and excellent rate performance.

[0006] In a first aspect, the embodiments of the present application provide a positive electrode material, which comprises positive electrode material particles, the positive electrode material particles have a core-shell structure, the core comprises a P2 phase layered oxide, and the shell comprises an O3 phase layered oxide.

[0007] Further, in the positive electrode material, the molecular formula of the positive electrode material comprises: Na x MO2, wherein 0.67 < x < 0.85, M comprises one or more of transition metal elements and alkali metal elements.

[0008] Further, in the positive electrode material, M comprises one or more of iron elements, nickel elements, lithium elements, copper elements, zinc elements, cobalt elements, titanium elements and manganese elements.

[0009] Further, in the positive electrode material, the Na / M element atomic number ratio A in the shell where the O3 phase layered oxide is located is 0.9 < A < 1.0.

[0010] Further, in the positive electrode material, the Na / M element atom number ratio a in the core where the P2 phase layered oxide is located is 0.5 < a < 0.8.

[0011] Further, in the positive electrode material, the particle size distribution D v 50 is 1 μm to 20 μm.

[0012] Further, in the positive electrode material, the specific surface area of the positive electrode material is 0.5 m 2 / g to 10 m 2 / g.

[0013] Further, in the positive electrode material, the powder compaction density of the positive electrode material under a pressure of 40 KN is 2 g / cm 3 / 3.5 g / cm 3 .

[0014] In a second aspect, the embodiment of the present application further provides a sodium ion battery, comprising: a positive electrode sheet, a negative electrode sheet, a separator and a battery electrolyte; wherein the positive electrode sheet comprises the positive electrode material of the first aspect.

[0015] In a third aspect, the embodiment of the present application further provides an electric device comprising the sodium ion battery of the second aspect.

[0016] By designing the positive electrode material particles into a core-shell structure of P2 phase layered oxide coated by O3 phase layered oxide, the O3 phase layered oxide can provide sufficient active sodium ions for the sodium ion battery to improve the first coulomb efficiency of the sodium ion battery, and the O3 phase layered oxide has stable crystal structure and reversible electrochemical performance, and can be regenerated by drying after absorbing water in the environment, and the inner core comprises P2 phase layered oxide, thereby ensuring excellent rate performance of the sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The schematic diagram of the morphology structure of the positive electrode material provided by the embodiment of the present application. DETAILED DESCRIPTION

[0019] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0020] It should be understood that the term "and / or" used in the specification and the appended claims of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0021] As analyzed in the background art of the present application, the existing sodium ion battery cannot simultaneously have high first coulomb efficiency and excellent rate performance. To solve the above technical problems, the present application provides a positive electrode material, a sodium ion battery and an electric device.

[0022] As shown in Figure 1 In an embodiment of the present application, a positive electrode material is provided, which includes positive electrode material particles, and the positive electrode material particles have a core-shell structure, the core of which includes a P2 phase layered oxide, and the shell of which includes an O3 phase layered oxide.

[0023] Specifically, the positive electrode material particles include a P2 phase layered oxide and an O3 phase layered oxide arranged on at least part of the surface of the P2 phase layered oxide. The positive electrode material particles can be in a spherical particle shape, and the ratio of the core of the positive electrode material particles to the diameter thereof can be (0.95-0.98):1. The space group of the P2 phase layered oxide is P63 / mmc, and the cell parameters are a=0.28nm, c=1.28nm. The ratio is 95-98%; the space group of the O3 phase layered oxide is R-3m, and the cell parameters are a=0.28nm, c=3.28nm. The ratio is 2%-5%. The ratio can be obtained by XRD testing.

[0024] It can be understood that the shape of the positive electrode material particles is not limited to a spherical particle shape, but can also be other shapes. The ratio of the core of the positive electrode material particles to the diameter thereof includes but is not limited to the above range, and limiting it in the above range can further improve the first coulomb efficiency of the sodium ion battery, and also further improve the rate performance of the sodium ion battery.

[0025] By applying the technical solutions of the present application, the O3 phase layered oxide can provide sufficient active sodium ions for the sodium ion battery to improve the first coulomb efficiency of the sodium ion battery. At the same time, due to the stable crystal structure and reversible electrochemical performance of the O3 phase layered oxide, it can be regenerated after drying after absorbing water in the environment, and the inner core includes the P2 phase layered oxide, thereby ensuring excellent rate performance of the sodium ion battery.

[0026] In some embodiments, the molecular formula of the positive electrode material includes Na x MO2, wherein 0.67 < x < 0.85, M can be one or more of transition metal elements, alkali metal elements.

[0027] In some embodiments, the molecular formula of the positive electrode material includes Na x MO2, wherein x is 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84 or a range consisting of any two of the above values.

[0028] Wherein, M can be provided by P2 phase layered oxide, can also be provided by O3 phase layered oxide, and can also be provided by P2 phase layered oxide and O3 phase layered oxide at the same time. For example, when the O3 phase layered oxide is sodium carbonate, the M element in the core and the shell of the sodium ion battery positive electrode material is provided by the P2 phase layered oxide, that is, after the O3 phase layered oxide is fully mixed in the coating process of the P2 phase layered oxide, the M element in the P2 phase layered oxide will migrate to the shell of the positive electrode material.

[0029] In some more specific embodiments, M includes one or more of iron elements, nickel elements, lithium elements, copper elements, zinc elements, cobalt elements, titanium elements, manganese elements, etc.

[0030] In some embodiments, the A of the Na / M element atomic ratio in the O3 phase layered oxide can be 0.9 < A < 1.0, by increasing the A of the Na / M element atomic ratio in the O3 phase layered oxide to above 0.9, the first coulomb efficiency of the sodium ion battery is further improved.

[0031] In some embodiments, the A of the Na / M element atomic ratio in the O3 phase layered oxide is 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or a range consisting of any two of the above values.

[0032] At the same time, in order to further ensure that the sodium ion battery has high first coulomb efficiency and excellent rate performance, the a of the Na / M element atomic ratio in the P2 phase layered oxide can be 0.5 < a < 0.8.

[0033] In some embodiments, the P2 phase layered oxide has a Na / M element atomic number ratio a of 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, or a range defined by any two of the above values.

[0034] Typically but not limitedly, the P2 phase layered oxide can be Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, Na 4 / 9 Mn1O2, Na 2 / 3 Ni 1 / 3Fe 1 / 3 Mn 1 / 3 O2, etc., the O3 phase layered oxide can be NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 2 / 9 Cu 1 / 9Fe 1 / 3 Mn 1 / 3 O2, NaOH, Na2CO3, NaHCO3, NaNi 1 / 2 Mn 1 / 2 O2, etc.

[0035] In some embodiments, in order to further improve the uniformity of the positive electrode material particles, the particle size distribution D v 50 of the positive electrode material is 1 μm to 20 μm.

[0036] In some embodiments, in order to further improve the uniformity of the positive electrode material particles, the particle size distribution D v 50 of the positive electrode material is 5 μm to 12 μm. At this time, the uniformity of the positive electrode material particles is better, which can effectively improve the initial coulombic efficiency and rate performance of the sodium ion battery.

[0037] It can be understood that the particle size distribution D v 50 of the positive electrode material includes but is not limited to the above range, and limiting it in the above range can further improve the uniformity of the positive electrode material particles, which can effectively improve the initial coulombic efficiency and rate performance of the sodium ion battery.

[0038] In some embodiments, in order to further improve the electrochemical performance of the sodium ion battery, the specific surface area of the positive electrode material is 0.5 m 2 / g to 10 m 2 / g.

[0039] In some embodiments, the specific surface area of the positive electrode material is 0.8 m 2 / g~7 m 2 / g.

[0040] In some embodiments, the specific surface area of the positive electrode material is 1 m 2 / g~5 m 2 / g. The first coulombic efficiency and the rate performance of the sodium-ion battery can be further improved.

[0041] It can be understood that the specific surface area of the positive electrode material of the sodium-ion battery includes but is not limited to the above range, and the electrochemical performance of the sodium-ion battery can be further improved by limiting it in the above range, thereby effectively improving the first coulombic efficiency and the rate performance of the sodium-ion battery.

[0042] In some embodiments, the powder compaction density of the positive electrode material under a pressure of 40 KN is 2 g / cm 3 ~3.5 g / cm 3 .

[0043] In some embodiments, the application further provides a preparation method of the positive electrode material, comprising the following steps:

[0044] S10, sintering a precursor of a P2 phase layered oxide to obtain a core of the positive electrode material particle;

[0045] S20, mixing the core of the positive electrode material particle with an O3 phase layered oxide to obtain a precursor of the positive electrode material;

[0046] S30, sintering the precursor of the positive electrode material to obtain the positive electrode material.

[0047] Specifically, the precursor of the P2 phase layered oxide can be mixed by a sodium source and a transition metal oxide, or a transition metal oxide containing sodium can be directly used as the precursor of the P2 phase layered oxide. For example, the precursor of the P2 phase layered oxide can include Na2CO3, NiO, Fe2O3, and MnO2, or can include Na2CO3, NiO, and Fe2O3, or can include NaHCO3, NiO, Fe2O3, and MnO2. Among them, if the precursor of the P2 phase layered oxide includes Na2CO3, NiO, Fe2O3, and MnO2, the molar ratio of Na:Ni:Fe:Mn in the precursor of the P2 phase layered oxide can be (1.5~2.5):1:1:1.

[0048] It can be understood that the precursor of the P2 phase layered oxide includes but is not limited to the above compounds, and the actual composition of the precursor of the P2 phase layered oxide can be selected according to the actual situation, which is not specifically limited in the present embodiment.

[0049] Furthermore, the precursor of the P2 phase layered oxide can be sintered in air at a temperature of 600℃ to 800℃ for 10 to 14 hours. Simultaneously, to ensure more uniform cathode material particles and more complete sintering, the precursor of the P2 phase layered oxide can be ball-milled and pressed into sheets before sintering. Pressing into sheets allows for more uniform heating during sintering, while ball milling ensures more complete sintering. The ball milling time can be 2 to 4 hours, the ball milling speed can be 100 to 500 rpm, and the preferred ball milling temperature is room temperature.

[0050] Furthermore, the core of the cathode material particles and the O3 phase layered oxide need to be thoroughly mixed to ensure that the core of the cathode material particles can be coated by the O3 phase layered oxide. Specifically, the core of the cathode material particles and the O3 phase layered oxide can be uniformly stirred at room temperature under vacuum for 2-4 hours at a stirring speed of 100-250 rpm.

[0051] Similarly, the precursor of the cathode material, formed by uniformly mixing the core of the cathode material particles with the layered oxide of the O3 phase, also needs to be pressed into sheets to facilitate more complete sintering of the precursor, thereby optimizing the initial coulombic efficiency and rate performance of the final sodium-ion battery cathode material. The cathode material precursor can be sintered in air at a temperature of 800℃–1000℃ for a time of 0.5h–1.5h.

[0052] In some embodiments, this application also provides a sodium-ion battery, which includes: a positive electrode, a negative electrode, a separator, and a battery electrolyte; wherein the positive electrode includes the above-described positive electrode material or a positive electrode material prepared by the above-described method.

[0053] Furthermore, in sodium-ion batteries, Al foil is typically chosen as the metal current collector for the positive electrode and Cu foil for the negative electrode. Since sodium and aluminum do not react to form a lithium-aluminum alloy like lithium and aluminum do, aluminum foil can be used as the current collector for both the positive and negative electrodes of sodium-ion batteries to reduce the cost of auxiliary materials for sodium-ion batteries.

[0054] In this embodiment, the thickness of the aluminum foil in the positive electrode sheet can be 8μm to 20μm, and the areal density of the positive electrode sheet can be 3mg / cm³. 2 ~30mg / cm 2 The compaction density can be 1 g / cm³. 3 ~3g / cm 3 The thickness of the aluminum foil in the negative electrode can be 8μm to 20μm, and the areal density of the negative electrode can be 1mg / cm³. 2~10mg / cm 2 The compaction density can be 0.3 g / cm³. 3 ~2g / cm 3 .

[0055] In some embodiments, the negative electrode material of the sodium-ion battery can be selected from materials with a potential higher than that of metallic sodium and capable of reversibly extracting / intercalating sodium ions, such as hard carbon (HC); while the electrolyte of the sodium-ion battery can be an organic carbonate solution with sodium salt (such as one or more of NaPF6 and NaClO4) as solute, and its concentration can be 0.5-5 mol / L. The solvent in the electrolyte can be one or more of ethylene carbonate, polycarbonate, dimethyl carbonate, and diethyl carbonate; the separator can be an electronic insulating material that can conduct ions.

[0056] It is understood that the positive electrode, negative electrode, separator, and battery electrolyte include, but are not limited to, the above-mentioned ranges. The specific selection can be made according to the actual application, and no specific limitation is made in this embodiment.

[0057] In some embodiments, this application also provides an electrical device that includes the sodium-ion battery described above.

[0058] The electrical equipment can include, but is not limited to, electric vehicles, electric cars, ships, spacecraft, mobile phones, tablets, laptops, electric toys, and power tools. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft; electric toys can include stationary or mobile electric toys, such as electric tank toys, game consoles, electric car toys, electric ship toys, and electric airplane toys.

[0059] This application designs the cathode material particles as a core-shell structure with O3-phase layered oxide coating P2-phase layered oxide, thereby enabling the O3-phase layered oxide to provide sufficient active sodium ions for the sodium-ion battery, thus improving the initial coulombic efficiency of the sodium-ion battery. At the same time, since the crystal structure of the O3-phase layered oxide is stable and its electrochemical performance is reversible, it can be dried and regenerated after absorbing water in the environment. The core includes P2-phase layered oxide, thus ensuring that the sodium-ion battery has excellent rate performance.

[0060] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0061] Example 1

[0062] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell. The molecular formula of the cathode material is Na. 0.71 Ni 1 / 3 Fe1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.12 m². 2 / g, compacted density is 3g / cm³ 3 .

[0063] The preparation method of the above-mentioned positive electrode material is as follows:

[0064] Step 1: Add Na₂CO₃, NiO, Fe₂O₃, and MnO₂ to a ball mill and ball mill at 300 rpm for 3 hours at room temperature. After ball milling, press the mixture into sheets under 40 kN pressure and sinter at 700°C in air for 12 hours. After cooling, remove the sheets to obtain the core of the cathode material particles. The molar ratio of Na:Ni:Fe:Mn is 2:1:1:1, and the molecular formula of the P₂ phase layered oxide in the core is Na₂CO₃. 0.67 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2;

[0065] Step 2: Place the core of the cathode material particles prepared in Step 1 and Na2CO3 in a stirrer and stir at 200 rpm for 3 hours under vacuum. After stirring, press it into a sheet shape under a pressure of 40 kN to obtain the precursor of the cathode material; wherein, Na... 0.67 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 The molar ratio of O2 to Na2CO3 is 1:0.1;

[0066] Step 3: Sinter the precursor of the cathode material prepared in Step 2 at 900°C for 1 hour in an air environment, and then cool it down to obtain the cathode material.

[0067] Example 2

[0068] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a diameter of 20 μm and a specific surface area of ​​1.12 m². 2 / g, compacted density is 2.9g / cm³ 3 .

[0069] The above-mentioned cathode material preparation method is basically the same as that in Example 1, except that the stirring speed in step 2 is 100 rpm.

[0070] Example 3

[0071] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.98 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 1 μm and a specific surface area of ​​4.83 m². 2 / g, compacted density is 3.1g / cm³ 3 .

[0072] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that Na in step 2... 0.67 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 The molar ratio of O2 to Na2CO3 is 1:0.13.

[0073] Example 4

[0074] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a diameter of 12 μm and a specific surface area of ​​0.49 m². 2 / g, compacted density is 2.8g / cm³ 3 .

[0075] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that the ball milling speed in step 1 is 200 rpm.

[0076] Example 5

[0077] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 5μm and a specific surface area of ​​9.97m². 2 / g, compacted density is 3.1g / cm³ 3 .

[0078] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that the ball milling speed in step 1 is 400 rpm.

[0079] Example 6

[0080] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.99 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.08 m². 2 / g, compacted density is 3g / cm³ 3 .

[0081] The preparation method of the above-mentioned cathode material is basically the same as that in Example 1, except that the molar ratio of Na:Ni:Fe:Mn in step 1 is 3:1:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.76 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0082] Example 7

[0083] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.98 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a diameter of 13 μm and a specific surface area of ​​0.53 m². 2 / g, compacted density is 2.9g / cm³ 3 .

[0084] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 6, except that the ball milling speed in step 1 is 200 rpm.

[0085] Example 8

[0086] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.99 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 6 μm and a specific surface area of ​​9.69 m². 2 / g, compacted density is 3.1g / cm³ 3 .

[0087] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 6, except that the ball milling speed in step 1 is 400 rpm.

[0088] Example 9

[0089] A cathode material has a Na / M atom ratio (a) of 0.60 in the core and a Na / M atom ratio (A) of 0.97 in the shell, with the molecular formula Na. 0.68 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 9 μm and a specific surface area of ​​2.97 m². 2 / g, compacted density is 2.9g / cm³ 3 .

[0090] The preparation method of the above-mentioned cathode material is basically the same as that in Example 1, except that the molar ratio of Na:Ni:Fe:Mn in step 1 is 1:1:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.60 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0091] Example 10

[0092] A cathode material has a Na / M atom ratio (a) of 0.60 in the core and a Na / M atom ratio (A) of 0.96 in the shell, with the molecular formula Na. 0.68 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a diameter of 14 μm and a specific surface area of ​​0.51 m². 2 / g, compacted density is 2.8g / cm³ 3 .

[0093] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 9, except that the ball milling speed in step 1 is 200 rpm.

[0094] Example 11

[0095] A cathode material has a Na / M atom ratio (a) of 0.60 in the core and a Na / M atom ratio (A) of 0.98 in the shell, with the molecular formula Na. 0.68 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3O2, particle size distribution D v 50 has a thickness of 9 μm and a specific surface area of ​​9.76 m². 2 / g, compacted density is 2.9g / cm³ 3 .

[0096] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 9, except that the ball milling speed in step 1 is 400 rpm.

[0097] Example 12

[0098] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.96 in the shell, with the molecular formula Na. 0.71 Cu 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 9 μm and a specific surface area of ​​2.98 m². 2 / g, compacted density is 3g / cm³ 3 .

[0099] The preparation method of the above-mentioned cathode material is basically the same as that in Example 1, except that: in step 1, Na2CO3, CuO, Fe2O3, and MnO2 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 KN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Cu:Fe:Mn is 2:1:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.67 Cu 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0100] Example 13

[0101] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Cu 1 / 6 Ni 1 / 6 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.21 m². 2 / g, compacted density is 3g / cm³ 3 .

[0102] The preparation method of the above-mentioned cathode material is basically the same as that in Example 1, except that: in step 1, Na2CO3, CuO, NiO, Fe2O3, and MnO2 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 kN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Cu:NiO:Fe:Mn is 2:0.5:0.5:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.67 Cu 1 / 6 Ni 1 / 6 Fe 1 / 3 Mn 1 / 3 O2.

[0103] Example 14

[0104] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Fe 1 / 3 Ti 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​2.92 m². 2 / g, compacted density is 3g / cm³ 3 .

[0105] The preparation method of the above-mentioned cathode material is basically the same as that in Example 6, except that: in step 1, Na2CO3, NiO, Fe2O3, and Ti2O3 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 KN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Ni:Fe:Ti is 2:1:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.76 Ni 1 / 3 Fe 1 / 3 Ti 1 / 3 O2.

[0106] Example 15

[0107] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.96 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Fe 1 / 3 Mn 1 / 6 Ti 1 / 6 O2, particle size distribution D v50 has a thickness of 9 μm and a specific surface area of ​​2.93 m². 2 / g, compacted density is 3g / cm³ 3 .

[0108] The preparation method of the above-mentioned cathode material is basically the same as that in Example 6, except that: in step 1, Na2CO3, NiO, Fe2O3, MnO2, and Ti2O3 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 kN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Ni:Fe:Mn:Ti is 2:1:1:0.5:0.5, and the molecular formula of the P2 phase layered oxide in the core is Na 0.76 Ni 1 / 3 Fe 1 / 3 Mn 1 / 6 Ti 1 / 6 O2.

[0109] Example 16

[0110] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.84 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a diameter of 11 μm and a specific surface area of ​​2.92 m². 2 / g, compacted density is 3g / cm³ 3 .

[0111] The preparation method of the above-mentioned cathode material is basically the same as that in Example 6, except that: in step 1, Na2CO3, NiO, CoO, and MnO2 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 KN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Ni:Co:Mn is 2:1:1:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.76 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2.

[0112] Example 17

[0113] A cathode material has a Na / M atom ratio (a) of 0.76 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.84Ni 1 / 3 Co 1 / 6 Fe 1 / 6 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.06 m². 2 / g, compacted density is 3g / cm³ 3 .

[0114] The preparation method of the above-mentioned cathode material is basically the same as that in Example 6, except that: in step 1, Na2CO3, NiO, CoO, Fe2O3, and MnO2 are added to a ball mill and ball-milled at 300 rpm for 3 hours at room temperature. After ball milling, the material is pressed into sheets under a pressure of 40 KN and sintered in air at 700°C for 12 hours. After cooling, the material is removed to obtain the core of the cathode material particles. The molar ratio of Na:Ni:Co:Fe:Mn is 2:1:0.5:0.5:1, and the molecular formula of the P2 phase layered oxide in the core is Na 0.76 Ni 1 / 3 Co 1 / 6 Fe 1 / 6 Mn 1 / 3 O2.

[0115] Example 18

[0116] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell. The molecular formula of the cathode material is Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.12 m². 2 / g, compacted density is 2g / cm³ 3 .

[0117] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that in step 1, the material is ball-milled at 100 rpm for 6 hours at room temperature.

[0118] Example 19

[0119] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 2μm and a specific surface area of ​​3.89m². 2 / g, compacted density is 3.5g / cm³ 3 .

[0120] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that the ball milling speed in step 1 is 500 rpm.

[0121] Example 20

[0122] A cathode material has a Na / M atom ratio (a) of 0.67 in the core and a Na / M atom ratio (A) of 0.95 in the shell, with the molecular formula Na. 0.71 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 15 μm and a specific surface area of ​​2.98 m². 2 / g, compacted density is 2.5g / cm³ 3 .

[0123] The preparation method of the above-mentioned positive electrode material is basically the same as that in Example 1, except that the ball milling speed in step 1 is 100 rpm.

[0124] Comparative Example 1

[0125] A cathode material with the molecular formula Na 0.67 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.12 m². 2 / g, compacted density is 3g / cm³ 3 .

[0126] The preparation method of the above-mentioned positive electrode material is as follows:

[0127] Step 1: Add Na2CO3, NiO, Fe2O3, and MnO2 into a ball mill and ball mill at 300 rpm for 3 hours at room temperature. After ball milling, press the mixture into sheets under a pressure of 40 KN and sinter it in air at 700℃ for 12 hours. After cooling, remove the material to obtain the above-mentioned cathode material. The molar ratio of Na:Ni:Fe:Mn is 2:1:1:1.

[0128] Comparative Example 2

[0129] A cathode material with the molecular formula NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, particle size distribution D v 50 has a thickness of 10 μm and a specific surface area of ​​3.24 m². 2 / g, compacted density is 3g / cm³ 3 .

[0130] The preparation method of the above-mentioned positive electrode material is as follows:

[0131] Step 1: Add Na2CO3, NiO, Fe2O3, and MnO2 into a ball mill and ball mill at 300 rpm for 3 hours at room temperature. After ball milling, press the mixture into sheets under a pressure of 40 KN and sinter it in air at 700℃ for 12 hours. After cooling, remove the material to obtain the above-mentioned cathode material. The molar ratio of Na:Ni:Fe:Mn is 4:1:1:1.

[0132] test

[0133] After the cathode materials prepared in Examples 1 to 20, as well as Comparative Examples 1 and 2, were applied to sodium-ion batteries, the performance of the sodium-ion batteries was tested using the following methods:

[0134] First-time efficiency of the full battery: Place a fresh cell that has not undergone electrochemical testing on a charge-discharge tester at room temperature, charge it to 3.8V at 0.33C (capacity Q1), and discharge it to 1.5V at 0.33C (capacity Q2). First-time efficiency of the full battery = Q2 / Q1*100%.

[0135] Rate performance: Fresh cells that have not undergone electrochemical testing are placed on a charge / discharge tester at room temperature. Charging to 3.8V at 0.33C and discharging to 1.5V at 0.33C yields a capacity of Q2. Charging to 3.8V at 0.33C and discharging to 1.5V at 6C yields a capacity of Q3. Rate performance = Q3 / Q2*100%.

[0136] The performance test results are shown in Table 1:

[0137] Table 1

[0138] Coated Full cell first efficiency (%) Rate capability (%) Example 1 Yes 88 92 Example 2 Yes 86 91 Example 3 Yes 87 90 Example 4 Yes 89 89 Example 5 Yes 86 93 Example 6 Yes 89 92 Example 7 Yes 85 91 Example 8 Yes 87 92 Example 9 Yes 85 91 Example 10 Yes 91 90 Example 11 Yes 84 92 Example 12 Yes 88 91 Example 13 Yes 87 92 Example 14 Yes 88 91 Example 15 Yes 87 92 Example 16 Yes 87 91 Example 17 Yes 88 91 Example 18 Yes 88 89 Example 19 Yes 82 94 Example 20 Yes 89.5 85 Comparative Example 1 No 78 89 Comparative Example 2 No 83 81

[0139] As can be seen from the above test results, by applying the technical solution of this application, the O3 phase layered oxide can coat the P2 phase layered oxide to form core-shell structured cathode material particles, thereby enabling the O3 phase layered oxide to provide sufficient active sodium ions for the sodium-ion battery, thus improving the first coulombic efficiency of the sodium-ion battery. At the same time, since the crystal structure of the O3 phase layered oxide is stable and its electrochemical performance is reversible, it can be dried and regenerated after absorbing water in the environment. The core includes the P2 phase layered oxide, thus ensuring that the sodium-ion battery has excellent rate performance.

[0140] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A positive electrode material, characterized in that, It includes positive electrode material particles, which have a core-shell structure, wherein the core is a P2 phase layered oxide and the shell is an O3 phase layered oxide; The particle size distribution D of the positive electrode material v 50 represents 1μm to 20μm; The molecular formula of the positive electrode material includes: Na x MO2, where 0.67 < x < 0.85, and M includes one or more of transition metal elements and alkali metal elements.

2. The cathode material according to claim 1, characterized in that, M includes one or more of the following elements: iron, nickel, lithium, copper, zinc, cobalt, titanium, and manganese.

3. The cathode material according to claim 1, characterized in that, The Na / M atom ratio of A in the shell containing the O3 phase layered oxide is 0.

9. <A<1.0。 4. The cathode material according to claim 3, characterized in that, The Na / M atom ratio a in the core containing the P2 phase layered oxide is 0.

5. <a<0.8。 5. The positive electrode material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode material is 0.5 m². 2 / g~10m 2 / g.

6. The cathode material according to claim 1, characterized in that, The compaction density of the positive electrode material under 40 kN pressure is 2 g / cm³. 3 ~3.5g / cm 3 .

7. A sodium-ion battery, characterized in that, include: A positive electrode, a negative electrode, a separator, and an electrolyte; wherein the positive electrode comprises the positive electrode material as described in any one of claims 1 to 6.

8. An electrical appliance, characterized in that, Including the sodium-ion battery as described in claim 7.

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