A high-energy-density sodium-ion battery sodium-rich positive electrode material and a preparation method and application thereof

Abstract

The application relates to the technical field of energy materials, in particular to a high-energy-density sodium-ion battery sodium-rich positive electrode material and a preparation method and application thereof. The sodium-rich positive electrode material is composed of sodium-ion layered oxides and sodium-rich oxides, the molar ratio of the sodium-ion layered oxides and the sodium-rich oxides is 0.1-10:1, and the sodium-rich positive electrode material is prepared through a high-temperature solid-phase method. The sodium-rich positive electrode material releases extra electrons and forms high specific capacity through the synergistic oxidation-reduction reaction of anion oxygen and metal cations, so that the energy density is significantly improved. The sodium-rich positive electrode material is a two-phase material, the heterogeneous interface buffer volume expands stress in the cycle process, and meanwhile, the two phases synergistically inhibit the irreversible phase transition caused by deep sodium extraction, so that the lattice integrity is maintained, and the cycle stability is improved.

Description

Technical Field

[0001] This invention relates to the field of energy materials technology, and more particularly to a high-energy-density sodium-ion battery sodium-rich cathode material, its preparation method, and its application. Background Technology

[0002] To address environmental pollution and the greenhouse effect caused by fossil fuels, sodium-ion batteries (SIBs) energy storage technology, with its high energy conversion efficiency and flexible controllability, is widely used in various mobile office devices and public transportation. However, the energy density of existing sodium-ion batteries is still insufficient to meet the rapidly growing demand for higher energy densities in areas such as electric vehicles and large-scale energy storage facilities.

[0003] The energy density of sodium-ion batteries is primarily limited by the performance of the cathode material. Currently, the main approach is to increase energy density by widening the voltage window of the cathode material. However, a higher voltage window leads to irreversible phase transitions and structural collapse of the cathode material under high voltage. Simultaneously, the cathode / electrolyte interface undergoes severe oxidation side reactions at high potentials (such as electrolyte decomposition and dissolution of transition metal ions), triggering the generation of large amounts of gases such as CO2 and O2, causing battery expansion and safety risks.

[0004] Therefore, developing cathode materials with anionic redox activity to obtain sodium-ion batteries with higher energy density is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-energy-density sodium-ion battery sodium-rich cathode material, its preparation method, and its application. This method utilizes the physicochemical reaction between two components during high-temperature sintering to achieve a phase fusion effect. The heterogeneous interface of the two-phase structure buffers the volume expansion stress during cycling and leverages the structural stability of the sodium-rich oxide, thus avoiding phase transition behavior. Simultaneously, the inherent anionic redox reaction of the sodium-rich oxide contributes additional capacity, significantly improving the energy density of the product.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In one aspect, the present invention provides a sodium-rich cathode material for high-energy-density sodium-ion batteries, wherein the sodium-rich cathode material is composed of sodium-ion layered oxide and sodium-rich oxide, and the molar ratio of sodium-ion layered oxide to sodium-rich oxide is 0.1 to 10:1.

[0008] In the above technical solution, the molecular structural formula of the sodium ion layered oxide is Na. x MO2, wherein 0.5 < x < 1, and M is one or more of Mn, Ni, Cu, and Ti; the phase of the sodium ion layered oxide is any one of P2 type layered, P3 type layered, and O3 type layered.

[0009] In the above technical solution, the molecular structural formula of the sodium-rich oxide is Na. y M'Oz, where y>1, z≥2, and M' is one of Mo, W, Ir, Ru, and Zr.

[0010] Another aspect of the present invention provides a method for preparing the above-mentioned high-energy-density sodium-ion battery sodium-rich cathode material, the method comprising the following steps:

[0011] Step (1): Sodium carbonate and M source are mixed according to the stoichiometric ratio of each chemical composition of sodium ion layered oxide to obtain mixture 1. Sodium carbonate and M' source are mixed according to the stoichiometric ratio of each chemical composition of sodium-rich oxide to obtain mixture 2.

[0012] Step (2): Perform a first ball milling treatment on mixture 1 and mixture 2 respectively;

[0013] Step (3): The ball milling products obtained in step (2) are subjected to a first sintering to obtain a sodium ion layered oxide precursor and a sodium-rich oxide precursor.

[0014] Step (4): The sodium ion layered oxide precursor and the sodium-rich oxide precursor obtained in step (3) are subjected to a second ball milling treatment respectively;

[0015] Step (5): Mix the ball milling product obtained in step (4) and then perform a second sintering to obtain the sodium-rich cathode material for sodium-ion batteries.

[0016] In the above technical solution, further, in step (1), the M source is one or more of manganese carbonate, nickel carbonate, copper oxide, and titanium oxide;

[0017] The M' source is one or more of molybdenum oxide, tungsten oxide, ruthenium oxide, iridium oxide, and zirconium oxide.

[0018] In the above technical solution, further, in step (2), the speed of the first ball mill is 100~800 rpm and the time is 0.5~12 h.

[0019] In the above technical solution, further, in step (3), the atmosphere of the first sintering is air, the heating rate is 1~10℃ / min, the sintering temperature is 300~800℃, and the holding time is 0.5~8h.

[0020] In the above technical solution, further, in step (4), the speed of the second ball mill is 200~900 rpm and the time is 1~10 h.

[0021] In the above technical solution, further, in step (5), the atmosphere of the second sintering is one of air, oxygen, a mixture of air and argon, or a mixture of oxygen and argon, the heating rate is 1~10℃ / min, the sintering temperature is 600~1100℃, and the holding time is 3~20 h; the molar ratio of sodium ion layered oxide precursor and sodium-rich oxide precursor is 0.1~10:1.

[0022] The present invention also provides an application of the above-mentioned sodium-rich cathode material in the preparation of sodium-ion batteries.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. The sodium-rich cathode material of this invention releases additional electrons and forms a high specific capacity through the synergistic redox reaction of anionic oxygen and metal cations, thereby achieving a significant improvement in energy density.

[0025] 2. The sodium-rich cathode material of this invention is a two-phase material. During cycling, the heterogeneous interface buffers the volume expansion stress, and the two phases work together to suppress the irreversible phase transition caused by deep sodium desodium removal, maintaining lattice integrity, thereby improving cycle stability.

[0026] 3. The preparation method of this invention is simple, the material cost is low, no toxic chemical reagents are introduced, the operation is safe, and it is suitable for large-scale production.

[0027] In summary, the sodium-rich cathode material of this invention integrates the cycle stability advantages of mature sodium-ion layered oxide materials with the high specific capacity advantages of sodium-rich oxide materials, thus systematically improving the performance of the electrode material and making it more suitable for the needs of modern high-energy-density equipment. Attached Figure Description

[0028] Figure 1 NaNi prepared for Comparative Example 1 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Charge-discharge curves of the O2 positive electrode;

[0029] Figure 2 NaNi prepared in Example 1 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Charge-discharge curves of sodium-rich positive electrode O2 (1:1)Na2MoO4;

[0030] Figure 3 Na prepared for Comparative Example 2 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Charge-discharge curves of the O2 positive electrode;

[0031] Figure 4 Na prepared in Example 9 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Charge-discharge curves of sodium-rich positive electrode O2 (4:1)Na2MoO4;

[0032] Figure 5 Na prepared for Comparative Example 2 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Cyclic performance test results of O2 cathode;

[0033] Figure 6 Na prepared in Example 9 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Cyclic performance test results of O2 (4:1)Na2MoO4 sodium-rich cathode;

[0034] Figure 7 The charge-discharge curve of Na2MoO4 obtained in Example 9 is shown. Detailed Implementation

[0035] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0036] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0037] Example 1

[0038] This embodiment provides a method for preparing a sodium-rich cathode material for a high-energy-density sodium-ion battery, including the following steps:

[0039] Step (1): According to the O3 type sodium ion layered oxide NaNi 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and molybdenum oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2MoO4. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0040] Step (2): Mixture 1 and mixture 2 are ball-milled at 100 rpm for 1 hour respectively;

[0041] Step (3): The ball-milled products obtained in step (2) are sintered at 600℃ in air atmosphere for 6 hours with a heating rate of 5℃ / min to obtain NaNi. 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor;

[0042] Step (4): Dispose of the NaNi obtained in step (3) separately 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were ball-milled at 300 rpm for 2 hours.

[0043] Step (5): Take the NaNi obtained in step (4) 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were mixed at a molar ratio of 1:1 and sintered at 900℃ in air for 10 hours with a heating rate of 5℃ / min to obtain NaNi. 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 (1:1)Na2MoO4 sodium-rich cathode material.

[0044] Example 2

[0045] Step (1): According to the O3 type sodium ion layered oxide NaNi 0.4 Mn 0.4 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and molybdenum oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2MoO4. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0046] Step (2): Mixture 1 and mixture 2 are ball-milled at 200 rpm for 2 hours respectively;

[0047] Step (3): The ball-milled products obtained in step (2) are sintered at 300℃ in air atmosphere for 3 hours with a heating rate of 5℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti0.1 O2 precursor and Na2MoO4 precursor;

[0048] Step (4): Dispose of the NaNi obtained in step (3) separately 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were ball-milled at 400 rpm for 1 hour.

[0049] Step (5): Take the NaNi obtained in step (4) 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were mixed at a molar ratio of 1:2 and sintered at 800℃ for 10 h in an oxygen atmosphere with a heating rate of 5℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 (1:2)Na2MoO4 sodium-rich cathode material.

[0050] Example 3

[0051] Step (1): According to the O3 type sodium ion layered oxide NaNi 0.4 Mn 0.4 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and zirconium oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2ZrO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0052] Step (2): Mixture 1 and mixture 2 were ball-milled at 600 rpm for 2 hours respectively;

[0053] Step (3): The ball-milled products obtained in step (2) are sintered at 300℃ in air atmosphere for 5 hours with a heating rate of 5℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2ZrO3 precursor;

[0054] Step (4): Dispose of the NaNi obtained in step (3) separately 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2ZrO3 precursor were ball-milled at 600 rpm for 1 hour.

[0055] Step (5): Take the NaNi obtained in step (4) 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2ZrO3 precursor were mixed at a molar ratio of 1:3 and sintered at 1000℃ in air for 20 hours with a heating rate of 10℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 (1:3)Na2ZrO3 sodium-rich cathode material.

[0056] Example 4

[0057] Step (1): According to the O3 type sodium ion layered oxide NaNi 0.4 Mn 0.4 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and zirconium oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2ZrO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0058] Step (2): Mixture 1 and mixture 2 were ball-milled at 600 rpm for 2 hours respectively;

[0059] Step (3): The ball-milled products obtained in step (2) are sintered at 500℃ in air atmosphere for 4 hours with a heating rate of 5℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2ZrO3 precursor;

[0060] Step (4): Dispose of the NaNi obtained in step (3) separately 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2ZrO3 precursor were ball-milled at 300 rpm for 1 hour.

[0061] Step (5): Take the NaNi obtained in step (4) 0.4 Mn 0.4 Cu 0.1 Ti 0.1O2 precursor and Na2ZrO3 precursor were mixed at a molar ratio of 1:1 and sintered at 1000℃ in air for 15 h with a heating rate of 6℃ / min to obtain NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 (1:1)Na2ZrO3 sodium-rich cathode material.

[0062] Example 5

[0063] Step (1): According to the P2 type sodium ion layered oxide Na 0.67 Sodium carbonate and manganese carbonate were weighed according to the stoichiometric ratio of the chemical composition of MnO2, and sodium carbonate and zirconium oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2ZrO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0064] Step (2): Mixture 1 and mixture 2 were ball-milled at 600 rpm for 2 hours respectively;

[0065] Step (3): The ball-milled products obtained in step (2) are sintered at 500℃ in air atmosphere for 5 hours with a heating rate of 5℃ / min to obtain Na. 0.67 MnO2 precursor and Na2ZrO3 precursor;

[0066] Step (4): Dispose of the Na obtained in step (3) separately 0.67 MnO2 precursor and Na2ZrO3 precursor were ball-milled at 300 rpm for 1 hour.

[0067] Step (5): Take the Na obtained in step (4) 0.67 MnO2 precursor and Na2ZrO3 precursor were mixed at a molar ratio of 1:1 and sintered at 600℃ for 15 h in air atmosphere with a heating rate of 6℃ / min to obtain Na 0.67 Sodium-rich cathode material: MnO2 (1:1)Na2ZrO3.

[0068] Example 6

[0069] Step (1): According to the P2 type sodium ion layered oxide Na 0.67 Sodium carbonate and manganese carbonate were weighed according to the stoichiometric ratio of MnO2, and sodium carbonate and tungsten oxide were weighed according to the stoichiometric ratio of sodium-rich oxide Na2WO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0070] Step (2): Mixture 1 and mixture 2 are ball-milled at 500 rpm for 2 hours respectively;

[0071] Step (3): The ball-milled products obtained in step (2) are sintered at 500℃ in air atmosphere for 5 hours with a heating rate of 5℃ / min to obtain Na. 0.67 MnO2 precursor and Na2WO3 precursor;

[0072] Step (4): Dispose of the Na obtained in step (3) separately 0.67 MnO2 precursor and Na2WO3 precursor were ball-milled at 300 rpm for 1 hour.

[0073] Step (5): Take the Na obtained in step (4) 0.67 MnO2 precursor and Na2WO3 precursor were mixed at a molar ratio of 0.1:1 and sintered at 1100℃ for 11 h under an oxygen atmosphere with a heating rate of 2℃ / min to obtain Na 0.67 Sodium-rich cathode material of MnO2 (0.1:1)Na2WO3.

[0074] Example 7

[0075] Step (1): According to the P3 type sodium ion layered oxide Na 0.8 Ni 0.4 Mn 0.4 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and iridium oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2IrO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0076] Step (2): Mixture 1 and mixture 2 are ball-milled at 500 rpm for 2 hours respectively;

[0077] Step (3): The ball-milled products obtained in step (2) are sintered at 500℃ in air atmosphere for 3 hours with a heating rate of 5℃ / min to obtain Na. 0.8 Ni 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2IrO3 precursor;

[0078] Step (4): Dispose of the Na obtained in step (3) separately 0.8 Ni 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2IrO3 precursor were ball-milled at 300 rpm for 1 hour.

[0079] Step (5): Take the Na obtained in step (4) 0.8 Ni 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 precursor and Na2IrO3 precursor were mixed at a molar ratio of 10:1 and sintered at 1100℃ for 12 hours under an oxygen atmosphere with a heating rate of 10℃ / min to obtain Na 0.8 Ni 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2 (10:1)Na2IrO3 sodium-rich cathode material.

[0080] Example 8

[0081] Step (1): According to the P2 type sodium ion layered oxide Na 0.67 Ni 0.33 Mn 0.67 Sodium carbonate, manganese carbonate, and nickel carbonate were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and ruthenium oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2RuO3. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0082] Step (2): Mixture 1 and mixture 2 are ball-milled at 500 rpm for 2 hours respectively;

[0083] Step (3): The ball-milled products obtained in step (2) were sintered at 500℃ in air for 4 hours at a heating rate of 5℃ / min to obtain Na. 0.67 Ni 0.33 Mn 0.67 O2 precursor and Na2RuO3 precursor;

[0084] Step (4): Dispose of the Na obtained in step (3) separately 0.67 Ni 0.33 Mn 0.67 O2 precursor and Na2RuO3 precursor were ball-milled at 300 rpm for 1 hour.

[0085] Step (5): Take the Na obtained in step (4) 0.67 Ni 0.33 Mn 0.67 O2 precursor and Na2RuO3 precursor were mixed at a molar ratio of 1:3 and sintered at 1100℃ in air for 10 hours with a heating rate of 5℃ / min to obtain Na2RuO3 precursor. 0.67 Ni 0.33 Mn 0.67 O2 (1:3)Na2RuO3 sodium-rich cathode material.

[0086] Example 9

[0087] Step (1): According to the P2 type sodium ion layered oxide Na 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 Sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide were weighed according to the stoichiometric ratio of the chemical composition of O2. Sodium carbonate and molybdenum oxide were weighed according to the stoichiometric ratio of the chemical composition of sodium-rich oxide Na2MoO4. The raw materials were mixed separately to obtain mixture 1 and mixture 2.

[0088] Step (2): Mixture 1 and mixture 2 are ball-milled at 500 rpm for 2 hours respectively;

[0089] Step (3): The ball-milled products obtained in step (2) are sintered at 500℃ in air atmosphere for 4 hours, with a heating rate of 5℃ / min, until Na... 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor;

[0090] Step (4): Dispose of the Na obtained in step (3) separately 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were ball-milled at 300 rpm for 2 hours.

[0091] Step (5): Take the Na obtained in step (4) 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 precursor and Na2MoO4 precursor were mixed at a molar ratio of 4:1 and sintered at 1000℃ in air for 12 hours with a heating rate of 6℃ / min to obtain Na2MoO4 precursor. 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 (4:1)Na2MoO4 sodium-rich cathode material.

[0092] Comparative Example 1

[0093] Step (1): According to the O3 type sodium ion layered oxide NaNi 0.3 Mn 0.5Cu 0.1 Ti 0.1 The stoichiometric ratio of the chemical composition of O2 is obtained by weighing sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide, mixing the raw materials to obtain a mixture;

[0094] Step (2): The mixture is ball-milled at 100 rpm for 1 hour;

[0095] Step (3): The ball-milled product obtained in step (2) is sintered at 900℃ in air atmosphere for 10 hours with a heating rate of 5℃ / min to obtain NaNi. 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 cathode material.

[0096] Comparative Example 2

[0097] Step (1): According to the P2 type sodium ion layered oxide Na 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The stoichiometric ratio of the chemical composition of O2 is obtained by weighing sodium carbonate, nickel carbonate, manganese carbonate, copper oxide, and titanium oxide, mixing the raw materials to obtain a mixture;

[0098] Step (2): The mixture was ball-milled at 500 rpm for 2 hours;

[0099] Step (3): The ball-milled product obtained in step (2) is sintered at 1000℃ in air atmosphere for 12 hours with a heating rate of 6℃ / min until Na 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 cathode material.

[0100] Sodium-ion batteries assembled from the cathode materials prepared in Comparative Example 1, Comparative Example 2, Example 1, and Example 9 were tested. Cathode material, super P carbon black, and PVDF binder were weighed in a 7:2:1 mass ratio, coated onto aluminum foil, and cut into 12mm diameter discs to obtain the cathode sheet. A 1mol / L NaClO4 solution was used as the solute, and a 1:1 mixture of EC and DEC was used as the solvent. Sodium foil was used as the counter electrode, and CR2032 coin cells were assembled. The assembled coin cells were tested at a current density of 0.1C with a nominal capacity of 100mAh / g.

[0101] The specific capacity of the cathode material in Examples 1-9 in the first cycle is shown in Table 1.

[0102] Table 1. Specific capacity of cathode materials in Examples 1-9 (first cycle)

[0103]

[0104] Figure 1 and Figure 2 The NaNi prepared in Comparative Example 1 is shown. 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 positive electrode and NaNi prepared in Example 1 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The first charge-discharge curves of the O2 (1:1) Na2MoO4 sodium-rich cathode were compared, revealing that NaNi 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The sodium-rich O2 (1:1)Na2MoO4 cathode exhibits a first-cycle discharge capacity of 212.12 mAh / g at a current density of 0.1C, which is higher than that of NaNi. 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The O2 cathode has a capacity of 193.89 mAh / g.

[0105] Figure 3 and Figure 4 The Na prepared in Comparative Example 2 is shown. 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 O2 positive electrode and Na prepared in Example 9 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The first two charge-discharge curves of the O2 (4:1)Na2MoO4 sodium-rich cathode were compared, and it was found that the first cycle of Na... 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The discharge capacity of the sodium-rich O2 (4:1)Na2MoO4 cathode is 206.90 mAh / g, and its specific capacity is higher than that of Na2MoO4. 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The O2 cathode has a specific capacity of 184.82 mAh / g, and the Na is represented by the dashed line. 0.67 Ni 0.3 Mn0.5 Cu 0.1 Ti 0.1 The second cycle curve of the sodium-rich cathode O2 (4:1) Na2MoO4 relative to Na 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The O2 cathode exhibits significantly less capacity decay.

[0106] exist Figure 5 and Figure 6 The comparison shows the cycle performance of the two cathodes in Comparative Example 2 and Example 9. The comparison reveals that Na 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The sodium-rich O2 (4:1)Na2MoO4 cathode still maintains a specific capacity of 159.17 mAh / g after 10 cycles at a current density of 0.1C, with a capacity retention of 86.58%, which is higher than that of Na2MoO4. 0.67 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.1 The O2 cathode has a capacity of 124.67 mAh / g and a capacity retention rate of 71.86%.

[0107] Using Na2MoO4 obtained in Example 9 as the positive electrode material, a battery was assembled and tested. Na2MoO4, super P carbon black, and PVDF binder were weighed in a 7:2:1 mass ratio, coated onto aluminum foil, and cut into 12mm diameter discs to obtain the positive electrode sheet. A 1mol / L NaClO4 solution was used as the solute, and a 1:1 mixture of EC and DEC was used as the solvent. Sodium foil was used as the counter electrode. A CR2032 coin cell was assembled. The assembled coin cell was tested at a current density of 0.1C under the condition of a nominal capacity of 100mAh / g.

[0108] Figure 7 The first two charge-discharge curves of the Na2MoO4 cathode are shown, indicating that its capacity contribution is mainly at the high-voltage plateau, suggesting that anionic redox reactions have occurred.

[0109] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a sodium-rich cathode material for a high-energy-density sodium-ion battery, characterized in that, The sodium-rich cathode material is composed of sodium-ion layered oxide and sodium-rich oxide, with a molar ratio of sodium-ion layered oxide to sodium-rich oxide of 0.1~10:1; the molecular structural formula of the sodium-rich oxide is Na. y M'O z Where y>1, z≥2, and M' is one of Mo, W, Ir, Ru, and Zr; The method includes the following steps: Step (1): Sodium carbonate and M source are mixed according to the stoichiometric ratio of each chemical composition of sodium ion layered oxide to obtain mixture 1. Sodium carbonate and M' source are mixed according to the stoichiometric ratio of each chemical composition of sodium-rich oxide to obtain mixture 2. Step (2): Perform a first ball milling treatment on mixture 1 and mixture 2 respectively; Step (3): The ball milling products obtained in step (2) are subjected to a first sintering to obtain a sodium ion layered oxide precursor and a sodium-rich oxide precursor. Step (4): The sodium ion layered oxide precursor and the sodium-rich oxide precursor obtained in step (3) are subjected to a second ball milling treatment respectively; Step (5): Mix the ball milling product obtained in step (4) and then perform a second sintering to obtain the sodium-rich cathode material for sodium-ion batteries. In step (3), the temperature of the first sintering is 300~600 ℃ and the holding time is 0.5~8 h.

2. The preparation method according to claim 1, characterized in that, The molecular structural formula of the sodium ion layered oxide is Na x MO2, wherein 0.5 < x < 1, and M is one or more of Mn, Ni, Cu, and Ti; the phase of the sodium ion layered oxide is any one of P2 type layered, P3 type layered, and O3 type layered.

3. The preparation method according to claim 1, characterized in that, In step (1), the M source is one or more of manganese carbonate, nickel carbonate, copper oxide, and titanium oxide; The M' source is one or more of molybdenum oxide, tungsten oxide, ruthenium oxide, iridium oxide, and zirconium oxide.

4. The preparation method according to claim 1, characterized in that, In step (2), the first ball milling speed is 100~800 rpm and the time is 0.5~12 h.

5. The preparation method according to claim 1, characterized in that, In step (3), the atmosphere for the first sintering is air, and the heating rate is 1~10 ℃ / min.

6. The preparation method according to claim 1, characterized in that, In step (4), the second ball milling speed is 200~900 rpm and the time is 1~10 h.

7. The preparation method according to claim 1, characterized in that, In step (5), the atmosphere of the second sintering is one of air, oxygen, a mixture of air and argon, or a mixture of oxygen and argon. The heating rate is 1~10℃ / min, the sintering temperature is 600~1100℃, and the holding time is 3~20 h. The molar ratio of sodium ion layered oxide precursor to sodium-rich oxide precursor is 0.1 to 10:

1.

8. The application of a sodium-rich cathode material prepared by the preparation method according to any one of claims 1-7 in the preparation of sodium-ion batteries.

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