Multi-element co-doping of sodium ion cathode material, method for preparing the same, and use

Abstract

The present invention provides a multi-element co-doped sodium ion cathode material, the cathode material being in the O3 phase, with a space group of R-3m, and its chemical formula is Na α M a Li b Cu c Ti d O 2+β wherein M is at least one of Ni, Co, Mn, Cr, V, Al, Fe, B, Si, Mg, and Zn, and 0.5≦α≦1, -0.1≦β≦0.1, 0

Description

[Technical Field]

[0001] This invention relates to the field of materials technology, and more particularly to a sodium ion cathode material co-doped with multiple elements, a method for preparing the same, and its use. [Background technology]

[0002] In recent years, lithium-ion batteries have experienced explosive growth, with demand increasing daily in the 3Cs (Common Demand, Cost, and Delivery), energy storage, and power sectors. However, lithium-ion batteries face challenges such as the depletion of lithium resources and nickel and cobalt ore. In particular, the price of lithium ore is rising year by year, and even if all the lithium resources explored worldwide were extracted, it would be insufficient to meet the explosively growing demand for lithium-ion batteries. Furthermore, the global distribution of lithium resources is highly uneven, and 80% of China's lithium ore must be imported from South America, posing a serious risk to national energy security. Therefore, there is a growing need to seek other alkali metal batteries with abundant resources, wide distribution, low prices, and high electrochemical performance. Sodium-ion batteries possess the above advantages, and in addition, they are fully compatible with lithium-ion batteries, with most of the auxiliary materials and processes being the same or similar.

[0003] Sodium-ion batteries primarily consist of a positive electrode, negative electrode, separator electrolyte, and other auxiliary materials. The performance of the positive electrode determines the performance of the battery. Common sodium-ion positive electrode materials typically have drawbacks such as low specific capacity (less than 135 mAh / g), poor structural stability, and low air stability. Pathways to obtain higher capacity mainly include extending the voltage range, introducing activated lattice oxygen, and doping with electrochemically active elements (mainly increasing the Ni content). The former two tend to sacrifice the cycle life of the material and make it difficult to achieve both structural stability and high capacity, potentially causing a decrease in discharge equalization voltage. The latter significantly increases raw material costs, contradicting the low-cost philosophy of sodium-ion positive electrode materials. The most commonly used solution is to optimize the structure by doping, but the effect of single-element doping is always limited and cannot improve aspects such as structure and performance. In other words, while elemental doping can stabilize the structure to obtain a long cycle life, single-element doping cannot satisfy the design requirements of high capacity and long cycle life.

[0004] There are three main types of sodium ion cathodes: oxides, Prussian blue, and polyanions. Oxides are becoming an increasingly popular technological hotspot in academia and industry due to their advantages such as high specific capacity, low cost, high voltage, wide availability of raw materials, and environmental friendliness. However, oxide cathode materials face problems such as low structural stability due to phase transitions, rapid capacity decay, and poor air stability, which slows down the progress of large-scale commercialization. [Overview of the project]

[0005] The objective of this invention is to achieve the goal of improving both the structure and electrochemical performance of cathode materials by realizing the synergistic effect of multiple elements through a multi-element co-doping method.

[0006] Therefore, the present invention relates to a sodium ion cathode material obtained by multi-element co-doping, wherein the cathode material is an O3 phase, the space group is R-3m, and its chemical formula is Na α M aLi b Cu c Ti d O 2+β where M is at least one of Ni, Co, Mn, Cr, V, Al, Fe, B, Si, Mg, Zn, and 0.5 ≤ α ≤ 1, -0.1 ≤ β ≤ 0.1, 0 < a < 0.95, 0 < b < 0.25, 0 < c < 0.3, 0 < d < 0.6, a + b + c + d = 1, and electrical neutrality is satisfied. A sodium ion cathode material by multi - element co - doping is proposed.

[0007] Preferably, M is one, two or three of Ni, Mn, Fe.

[0008] Preferably, 0.05 ≤ a + b + c < 1.

[0009] The present invention also provides a method for preparing the sodium ion cathode material by multi - element co - doping. The method includes weighing appropriate amounts of a Na - element - containing compound, an M - element - containing compound, a Li - element - containing compound, a Cu - element - containing compound and a Ti - element - containing compound according to the atomic ratio of Na element, M element, Li element, Cu element and Ti element in the chemical formula Na α M a Li b Cu c Ti d O 2+β mixing them to obtain a mixture, and firing the mixture to obtain a sodium ion cathode material by multi - element co - doping. A method for preparing the sodium ion cathode material by multi - element co - doping is proposed.

[0010] Preferably, the M - element - containing compound, the Li - element - containing compound, the Cu - element - containing compound and the Ti - element - containing compound are independently at least one of metal oxides, metal nitrates, metal sulfates, metal carbonates and metal chlorides.

[0011] Preferably, the Na - element - containing compound is at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate.

[0012] Preferably, the amount of the Na-containing compound weighed is 100% to 110% of the theoretical amount calculated according to the atomic ratio of Na, M, Li, Cu, and Ti.

[0013] Preferably, the amount of sodium-containing compound weighed is 102% to 106% of the theoretical amount.

[0014] Preferably, the amount of Li-containing compound weighed is 100% to 110% of the theoretical amount.

[0015] Preferably, the amount of Li-containing compound weighed is 102% to 106% of the theoretical amount.

[0016] Preferably, the mixing step includes mixing a Na-containing compound, an M-containing compound, a Li-containing compound, a Cu-containing compound, and a Ti-containing compound and mechanically milling them to obtain a mixture.

[0017] Preferably, the speed of mechanical milling is 100 rpm to 1000 rpm, and the duration is 1 hour to 48 hours.

[0018] Preferably, the firing temperature is 700°C to 1050°C, the firing time is 6 hours to 36 hours, and the heating rate is 1°C / min to 20°C / min.

[0019] The present invention also relates to a method for preparing a sodium ion cathode material by the above-mentioned multi-element co-doping, the method comprising weighing out an appropriate amount of M-element-containing nitrate or M-element-containing sulfate according to the atomic ratio of M-element in the chemical formula MCO3 or M(OH)2, dissolving it in water, adjusting the pH with a precipitating agent and a complexing agent to uniformly precipitate it, and obtaining a precursor MCO3 or M(OH)2 after drying, and the chemical formula Na α M a Li b Cu c Ti d O 2+βWe propose a method for preparing a sodium ion cathode material by multi-element co-doping, characterized by comprising weighing appropriate amounts of a sodium-containing compound, a lithium-containing compound, a cu-containing compound, a ti-containing compound, and a precursor MCO3 or M(OH)2 according to the atomic ratio of sodium, magnesium, lithium, copper, and ti in a given material, mixing them to obtain a mixture, and calcining the mixture to obtain a sodium ion cathode material by multi-element co-doping.

[0020] Preferably, the Li-containing compound, Cu-containing compound, and Ti-containing compound are independently at least one of metal oxides, metal nitrates, metal sulfates, metal carbonates, and metal chlorides.

[0021] Preferably, the Na element-containing compound is at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

[0022] Preferably, the amount of the Na-containing compound weighed is 100% to 110% of the theoretical amount calculated according to the atomic ratio of Na, M, Li, Cu, and Ti.

[0023] Preferably, the amount of sodium-containing compound weighed is 102% to 106% of the theoretical amount.

[0024] Preferably, the amount of Li-containing compound weighed is 100% to 110% of the theoretical amount.

[0025] Preferably, the amount of Li-containing compound weighed is 102% to 106% of the theoretical amount.

[0026] Preferably, the pH of the precursor acquisition step is 7.5 to 13, the precipitating agent is sodium hydroxide or sodium carbonate, the complexing agent is aqueous ammonia, the drying temperature is 80°C to 150°C, and the drying time is 6 to 48 hours.

[0027] Preferably, the mixing step includes mixing a Na-containing compound, a Li-containing compound, a Cu-containing compound, a Ti-containing compound, and a precursor MCO3 or M(OH)2 compound and mechanically milling them to obtain a mixture.

[0028] Preferably, the speed of mechanical milling is 100 rpm to 1000 rpm, and the duration is 1 hour to 48 hours.

[0029] Preferably, the firing temperature is 700°C to 1050°C, the firing time is 6 hours to 36 hours, and the heating rate is 1°C / min to 20°C / min.

[0030] The present invention also provides a sodium-ion battery characterized by including a sodium-ion cathode material co-doped with the above-mentioned multi-element material.

[0031] Preferably, sodium-ion batteries are used in low-speed motorcycles, electric vehicles, wind power generation, peak load adjustment for smart grids, solar power generation, household power supplies, or large-scale energy storage equipment for communication base stations.

[0032] According to the present invention, Li + Because it has a larger ionic radius and stronger Li-O bond energy, it can activate lattice oxygen at high voltage, O 2- / O n- By achieving reversible capacitance in the electrical pair, Ti 4+ Ni 2+ / Ti 4+ -O 2- It is possible to improve covalent bonding properties, further stabilize the structure, reduce cation mixing, suppress multiphase transitions, and stabilize the layered structure of the material, Cu 2+ This can significantly improve the air stability of the material, and Cu 2+ / Cu 3+ This can also provide partial capacitance. This imparts high structural stability and high electrochemical performance to the cathode material of the present invention. [Brief explanation of the drawing]

[0033] [Figure 1] This is an SEM topography of Example 1. [Figure 2] This is the SEM topography of Example 3. [Figure 3] These are the XRD spectra of Example 3 and Example 4. [Figure 4] These are electrochemical performance diagrams for the first cycle of Examples 4 and 5. [Figure 5] These are performance diagrams for the first 100 cycles of Examples 1, 4, and 5. [Modes for carrying out the invention]

[0034] Specific embodiments of the present invention will be described in detail below with reference to the drawings. The specific embodiments described herein are merely for illustrative purposes and interpretation of the present invention, and should be understood not as limiting the invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to these precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. With respect to numerical ranges, the intervals between the endpoint values ​​of individual ranges, between the endpoint values ​​of individual ranges and individual point values, and between individual point values ​​can be combined to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed herein.

[0036] A first embodiment of the present invention is a multi-element co-doped sodium ion cathode material, which is an O3 phase, has a space group of R-3m, and has the chemical formula Na α M a Li b Cu c Ti d O 2+βA sodium ion cathode material by multi-element co-doping that satisfies electrical neutrality is proposed. In the formula, M is at least one of Ni, Co, Mn, Cr, V, Al, Fe, B, Si, Mg, Zn. Specifically, it may be one, two or three of Ni, Mn, Fe, but is not limited thereto. α is the number of Na element atoms per cathode material, and 0.5 ≤ α ≤ 1. 2 + β is the number of O element atoms per cathode material, and -0.1 ≤ β ≤ 0.1. a is the number of M element atoms per cathode material, and 0 < a < 0.95. b is the number of Li element atoms per cathode material, and 0 < b < 0.25. c is the number of Cu element atoms per cathode material, and 0 < c < 0.3. d is the number of Ti element atoms per cathode material, and 0 < d < 0.6. And a + b + c + d = 1. Also, a + b + c can satisfy the condition of 0.05 ≤ a + b + c < 1, but is not limited thereto.

[0037] The second embodiment of the present invention proposes a method for preparing a sodium ion cathode material by multi-element co-doping. The sodium ion cathode material by multi-element co-doping is as described above, and its description is omitted here. This method is the high-temperature solid-phase method, and the detailed steps are as follows: First, the chemical formula Na α M a Li b Cu c Ti d O 2+βDepending on the atomic ratios of Na, M, Li, Cu, and Ti elements in the mixture, appropriate amounts of Na-containing compounds, M-containing compounds, Li-containing compounds, Cu-containing compounds, and Ti-containing compounds are weighed out and mixed to obtain a mixture. Specifically, the M-containing compounds, Li-containing compounds, Cu-containing compounds, and Ti-containing compounds may be, but are not limited to, at least one of metal oxides, metal nitrates, metal sulfates, metal carbonates, and metal chlorides. For example, an M-element compound is at least one of M-element oxides, M-element nitrates, M-element sulfates, M-element carbonates, and M-element chlorides; a Li-element compound is at least one of Li-element oxides, Li-element nitrates, Li-element sulfates, Li-element carbonates, and Li-element chlorides; a Cu-element compound is at least one of Cu-element oxides, Cu-element nitrates, Cu-element sulfates, Cu-element carbonates, and Cu-element chlorides; and a Ti-element compound is at least one of Ti-element oxides, Ti-element nitrates, Ti-element sulfates, Ti-element carbonates, and Ti-element chlorides. Specifically, a Na-element compound may be at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate, but is not limited to these. When mixing, a mixture can be obtained by mechanically milling a compound containing Na, a compound containing M, a compound containing Li, a compound containing Cu, and a compound containing Ti. The speed of mechanical milling may be 100 rpm to 1000 rpm, but is not limited thereto, and the time of mechanical milling may be 1 hour to 48 hours, but is not limited thereto.

[0038] The weighing amounts of Na-containing compounds, M-containing compounds, Li-containing compounds, Cu-containing compounds, and Ti-containing compounds can be adjusted based on theoretical amounts calculated according to the atomic ratios of Na, M, Li, Cu, and Ti, and these theoretical amounts can be expressed by the following formulas: Theoretical weight of a sodium-containing compound = (α) x (molecular weight of the sodium-containing compound) x arbitrary constant / (number of sodium atoms per sodium-containing compound) Theoretical quantity of an M-element compound = (a) x (molecular weight of the M-element compound) x arbitrary constant / (number of M-element atoms per M-element compound) Theoretical weight of a Li-containing compound = (b) x (molecular weight of the Li-containing compound) x arbitrary constant / (number of Li atoms per Li-containing compound) Theoretical weight of a Cu-containing compound = (c) x (molecular weight of the Cu-containing compound) x arbitrary constant / (number of Cu atoms per Cu-containing compound) Theoretical weight of a Ti-containing compound = (d) x (molecular weight of the Ti-containing compound) x arbitrary constant / (number of Ti atoms per Ti-containing compound) Of these, all arbitrary constants are the same.

[0039] The weighed amounts of Na-containing compounds, M-containing compounds, Li-containing compounds, Cu-containing compounds, and Ti-containing compounds may be 100% to 110% of the theoretical amount, but are not limited thereto, and are preferably 102% to 106%, more preferably 103%. In a preferred example, the weighed amounts of M-containing compounds, Cu-containing compounds, and Ti-containing compounds may be 100% of the theoretical amount, and the weighed amounts of Na-containing compounds and Li-containing compounds may be 100% to 110% of the theoretical amount, preferably 102% to 106%, more preferably 103%.

[0040] Next, the mixture is calcined to obtain a sodium ion cathode material co-doped with multiple elements. Specifically, the calcination temperature may be 700°C to 1050°C, but is not limited thereto; the calcination time may be 6 hours to 36 hours, but is not limited thereto; and the heating rate may be 1°C / min to 20°C / min, but is not limited thereto. Furthermore, in order to obtain a suitable particle size for the cathode material, it can be further cooled and crushed after calcination and then sieved through a 300-mesh sieve.

[0041] A third embodiment of the present invention proposes a method for preparing a sodium ion cathode material by multi-element co-doping. The multi-element co-doped sodium ion cathode material is as described above, and its explanation is omitted here. This method is a coprecipitation method, and the detailed steps are as follows: First, an appropriate amount of nitrate or sulfate containing element M is weighed out according to the atomic ratio of element M in the chemical formula MCO3 or M(OH)2, dissolved in water, and the pH is adjusted with a precipitating agent and a complexing agent to allow for uniform precipitation. After drying, the precursor MCO3 or M(OH)2 is obtained. Specifically, the pH adjusted with the precipitating agent and complexing agent may be 7.5 to 13, but is not limited thereto; examples of precipitating agents may be sodium hydroxide or sodium carbonate, but is not limited thereto; examples of complexing agents may be aqueous ammonia, but is not limited thereto; the drying temperature may be 80°C to 150°C, but is not limited thereto; and the drying time may be 6 to 48 hours, but is not limited thereto.

[0042] Next, the chemical formula Na α M a Li b Cu c Ti d O 2+βDepending on the atomic ratio of Na, M, Li, Cu, and Ti elements in the mixture, appropriate amounts of Na-containing compounds, Li-containing compounds, Cu-containing compounds, Ti-containing compounds, and precursor MCO3 or M(OH)2 are weighed and mixed to obtain a mixture. Specifically, the Li-containing compounds, Cu-containing compounds, and Ti-containing compounds may be, but are not limited to, at least one of metal oxides, metal nitrates, metal sulfates, metal carbonates, and metal chlorides. For example, the Li-containing compound is at least one of Li-containing oxides, Li-containing nitrates, Li-containing sulfates, Li-containing carbonates, and Li-containing chlorides; the Cu-containing compound is at least one of Cu-containing oxides, Cu-containing nitrates, Cu-containing sulfates, Cu-containing carbonates, and Cu-containing chlorides; and the Ti-containing compound is at least one of Ti-containing oxides, Ti-containing nitrates, Ti-containing sulfates, Ti-containing carbonates, and Ti-containing chlorides. Specifically, the Na-containing compound is at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate. When mixing, the Na-containing compound, Li-containing compound, Cu-containing compound, Ti-containing compound, and precursor MCO3 or M(OH)2 can be mixed and mechanically milled to obtain the mixture. The mechanical milling speed may be 100 rpm to 1000 rpm, but is not limited thereto, and the mechanical milling time may be 1 hour to 48 hours, but is not limited thereto.

[0043] The weighing amounts of Na-containing compounds, Li-containing compounds, Cu-containing compounds, Ti-containing compounds, and precursors MCO3 or M(OH)2 can be adjusted based on theoretical amounts calculated according to the atomic ratios of Na, M, Li, Cu, and Ti, and these theoretical amounts can be expressed by the following formulas: Theoretical weight of a sodium-containing compound = (α) x (molecular weight of the sodium-containing compound) x arbitrary constant / (number of sodium atoms per sodium-containing compound) Theoretical weight of a Li-containing compound = (b) x (molecular weight of the Li-containing compound) x arbitrary constant / (number of Li atoms per Li-containing compound) Theoretical weight of a Cu-containing compound = (c) x (molecular weight of the Cu-containing compound) x arbitrary constant / (number of Cu atoms per Cu-containing compound) Theoretical weight of a Ti-containing compound = (d) x (molecular weight of the Ti-containing compound) x arbitrary constant / (number of Ti atoms per Ti-containing compound) Theoretical amount of precursor MCO3 or M(OH)2 = (a) x (molecular weight of precursor MCO3 or M(OH)2) x arbitrary constant Of these, all arbitrary constants are the same.

[0044] The weighed amounts of the Na-containing compound, Li-containing compound, Cu-containing compound, Ti-containing compound, and precursor MCO3 or M(OH)2 may be 100% to 110% of the theoretical amount, preferably 102% to 106%, and more preferably 103%. In a preferred example, the weighed amounts of the Cu-containing compound, Ti-containing compound, and precursor MCO3 or M(OH)2 may be 100% of the theoretical amount, and the weighed amounts of the Na-containing compound and Li-containing compound may be 100% to 110% of the theoretical amount, preferably 102% to 106%, and more preferably 103%.

[0045] Next, the mixture is calcined to obtain a sodium ion cathode material co-doped with multiple elements. Specifically, the calcination temperature may be 700°C to 1050°C, but is not limited thereto; the calcination time may be 6 hours to 36 hours, but is not limited thereto; and the heating rate may be 1°C / min to 20°C / min, but is not limited thereto. Furthermore, in order to obtain a suitable particle size for the cathode material, it can be further cooled and crushed after calcination and then sieved through a 300-mesh sieve.

[0046] A fourth embodiment of the present invention proposes a sodium-ion battery comprising a multi-element co-doped sodium-ion cathode material as described above. Specifically, the multi-element co-doped sodium-ion cathode material can be mixed with an adhesive to form the cathode of the battery. Specifically, the adhesive may be at least one of SP and PVDF, but is not limited to these. Furthermore, the mass ratio of the multi-element co-doped sodium-ion cathode material to the adhesive may be (70-95):(5-30), but is not limited to this, and is preferably 90:10. Moreover, the sodium-ion battery may be used in low-speed motorcycles, electric vehicles, wind power generation, peak adjustment of smart grids, solar power generation, household power supplies, or large-scale energy storage equipment for communication base stations, but is not limited to these.

[0047] The present invention will be illustrated by the following examples: Example 1

[0048] In other cases, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.05 Cu 0.1 Ti 0.1 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.05 Cu 0.1 Ti 0.1 Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, lithium carbonate, copper oxide, and titanium dioxide were weighed out according to the stoichiometric ratio of O2, with sodium carbonate and lithium carbonate being 103% of the theoretically added amounts. These raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0049] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material (shown in Figure 1).

[0050] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Example 2

[0051] In other cases, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.05 Cu 0.15 Ti 0.05 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.05 Cu 0.15 Ti 0.05 Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, lithium carbonate, copper oxide, and titanium dioxide were weighed out according to the stoichiometric ratio of O2, with sodium carbonate and lithium carbonate being 103% of the theoretically added amounts. These raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0052] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0053] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Example 3

[0054] In other cases, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.075 Cu 0.1 Ti 0.075 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.075 Cu 0.1 Ti 0.075Weighed appropriate amounts of sodium carbonate, manganese dioxide, nickel oxide, lithium carbonate, copper oxide, and titanium dioxide according to the stoichiometric ratio of O2. Among them, sodium carbonate and lithium carbonate were 103% of the theoretical addition amount. Put the above raw materials into a ball mill and mechanically milled for 6 hours at a rotation speed of 350 rpm of the ball mill.

[0055] Put the mixture after the ball mill into a high-temperature furnace and calcined at 875 °C for 12 hours, with a heating rate of 5 °C / min. Cooled, pulverized, and sieved through a 300-mesh sieve to obtain a positive electrode material (shown in Figure 2).

[0056] The positive electrode material prepared above, SP, and PVDF were made into a slurry at a mass ratio of 90:5:5, coated, dried, and cut to form a positive electrode, and then assembled into a coin-type battery to evaluate its electrochemical performance. Example 4

[0057] In this example, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.075 Cu 0.1 Ti 0.075 O2 was prepared as follows: Chemical formula Mn 0.667 Ni 0.333 Weighed appropriate amounts of nickel sulfate and manganese sulfate according to the stoichiometric ratio of (OH)2, dissolved them in a certain amount of water, adjusted the pH with sodium hydroxide and ammonia water to precipitate uniformly, and dried at 100 °C to obtain the precursor Mn 0.667 Ni 0.333 (OH)2.

[0058] Chemical formula NaMn 0.5 Ni 0.25 Li 0.075 Cu 0.1 Ti 0.075 Weighed appropriate amounts of the above precursor, sodium carbonate, lithium carbonate, copper oxide, and titanium dioxide according to the stoichiometric ratio of O2, put them into a mill, and mechanically milled for 8 hours at a ball mill speed of 200 rpm to obtain a mixture.

[0059] The mixture after the ball mill was put into a high-temperature furnace and fired at 850 °C for 15 hours with a heating rate of 5 °C / min. After cooling and pulverizing, it was sieved through a 300-mesh sieve to obtain the cathode material.

[0060] The cathode material prepared above, SP, and PVDF were made into a slurry at a mass ratio of 90:5:5, coated, dried, and cut to form a cathode, which was then assembled into a coin-type battery to evaluate its electrochemical performance. Example 5

[0061] In this example, the cathode material NaMn 0.4 Ni 0.2 Fe 0.15 Li 0.075 Cu 0.1 Ti 0.075 O2 was prepared as follows: According to the stoichiometric ratio of the chemical formula NaMn 0.4 Ni 0.2 Fe 0.15 Li 0.075 Cu 0.1 Ti 0.075 Appropriate amounts of sodium carbonate, manganese sesquioxide, nickel oxide, ferric oxide, lithium carbonate, copper oxide, and titanium dioxide were weighed according to the stoichiometric ratio of O2. Among them, sodium carbonate and lithium carbonate were 103% of the theoretical addition amount. The above raw materials were put into a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0062] The mixture after the ball mill was put into a high-temperature furnace and fired at 875 °C for 12 hours with a heating rate of 5 °C / min. After cooling and pulverizing, it was sieved through a 300-mesh sieve to obtain the cathode material.

[0063] The cathode material prepared above, SP, and PVDF were made into a slurry at a mass ratio of 90:5:5, coated, dried, and cut to form a cathode, which was then assembled into a coin-type battery to evaluate its electrochemical performance. Comparative Example 1

[0064] In this comparative example, the cathode material NaMn 0.5 Ni 0.25 Li 0.25Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.25 Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, and lithium carbonate were weighed out according to the stoichiometric ratio of O2, with sodium carbonate and lithium carbonate being 103% of the theoretically added amounts. These raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0065] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0066] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Comparative Example 2

[0067] In this comparative example, the positive electrode material NaMn 0.5 Ni 0.25 Cu 0.25 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Cu 0.25 Sodium carbonate, dimanganese trioxide, nickel oxide, and copper oxide were weighed in appropriate amounts according to the stoichiometric ratio of O2, with sodium carbonate being 103% of the theoretically added amount. The above raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0068] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0069] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Comparative Example 3

[0070] In this comparative example, the positive electrode material NaMn 0.5 Ni 0.25 Ti 0.25 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Ti 0.25 Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, and titanium dioxide were weighed out according to the stoichiometric ratio of O2, with sodium carbonate being 103% of the theoretical amount. The above raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0071] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0072] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Comparative Example 4

[0073] In this comparative example, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.125 Cu 0.125 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.125 Cu 0.125Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, lithium carbonate, and copper oxide were weighed out according to the stoichiometric ratio of O2. Of these, sodium carbonate and lithium carbonate were added at 103% of the theoretical amount. The above raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0074] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0075] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Comparative Example 5

[0076] In this comparative example, the positive electrode material NaMn 0.5 Ni 0.25 Li 0.125 Ti 0.125 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Li 0.125 Ti 0.125 Appropriate amounts of sodium carbonate, dimanganese trioxide, nickel oxide, lithium carbonate, and titanium dioxide were weighed out according to the stoichiometric ratio of O2. Of these, sodium carbonate and lithium carbonate were added at 103% of the theoretical amount. The above raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0077] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0078] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance. Comparative Example 6

[0079] In this comparative example, the positive electrode material NaMn 0.5 Ni 0.25 Cu 0.125 Ti 0.125 Prepare O2 as follows: Chemical formula NaMn 0.5 Ni 0.25 Cu 0.125 Ti 0.125 Sodium carbonate, dimanganese trioxide, nickel oxide, copper oxide, and titanium dioxide were weighed in appropriate amounts according to the stoichiometric ratio of O2, with sodium carbonate being 103% of the theoretical amount. These raw materials were placed in a ball mill and mechanically milled at a rotation speed of 350 rpm for 6 hours.

[0080] The mixture after ball milling was placed in a high-temperature furnace and fired at 875°C for 12 hours at a heating rate of 5°C / min. After cooling, it was pulverized and sieved through a 300-mesh sieve to obtain the cathode material.

[0081] The cathode material prepared above, along with SP and PVDF, were mixed into a slurry in a mass ratio of 90:5:5. After coating, drying, and cutting, the slurry was used as the cathode, and the resulting assembly into a coin-type battery was evaluated for its electrochemical performance.

[0082] Please refer to Figure 3. When compared with the standard product JCPDS 54-0887, it was found that the cathode materials obtained in these examples have an R3-m space group. Please refer to Figure 4. It was found that all of these examples can impart an immediate charge / discharge effect to the battery. Please refer to Figure 5. It was found that these examples impart a high capacity retention to the battery even after 100 charge / discharge cycles.

[0083] Please refer to Table 1. Examples 1-3 had almost the same preparation process and the same atomic ratio of Mn and Ni elements in the positive electrode material, resulting in an appropriate atomic ratio of Li, Cu, and Ti elements in the positive electrode material. Examples 3 and 5 had almost the same preparation process and the same atomic ratio of Li, Cu, and Ti elements in the positive electrode material, and it was found that the battery performance deteriorated when the positive electrode material contained Fe.

[0084] Please refer to Table 1. Comparative Examples 1 to 3 followed almost the same preparation process as Example 1, and the atomic ratios of Mn and Ni in the positive electrode material were the same. As a result, the performance that Li, Cu, and Ti together bring to the battery is superior to that of any one of Li, Cu, or Ti, demonstrating that Li, Cu, and Ti can have a synergistic effect on the battery's performance.

[0085] Please refer to Table 1. Comparative Examples 4-6 followed almost the same preparation process as Example 1, and the atomic ratios of Mn and Ni in the positive electrode material were the same. As a result, the performance that Li, Cu, and Ti together bring to the battery is superior to any two of the three elements, demonstrating that Li, Cu, and Ti can have a synergistic effect on the battery's performance.

[0086] Table 1, Electrochemical test results JPEG0007897313000001.jpg93170

[0087] Any further information relating to common knowledge will not be explained in detail and will be understandable to those skilled in the art.

[0088] The above description is merely a few specific embodiments of the present invention and is not intended to limit it. Any modifications, equivalent substitutions, improvements, etc., made in the spirit and principles of the present invention should all be included within the scope of the claims. The technical scope of this invention is not limited to the contents of the specification and should be determined by the claims.

Claims

1. A sodium ion cathode material obtained by multi-element co-doping, The positive electrode material is an O3 phase, the space group is R-3m, and its chemical formula is Na α M ａ Li ｂ Cu ｃ Ti ｄ O ２＋β A sodium ion cathode material obtained by multi-element co-doping, characterized in that, among these elements, M is Ni and Mn, or Ni, Mn and Fe, and 0.5 ≤ α ≤ 1, -0.1 ≤ β ≤ 0.1, 0 < a < 0.95, 0 < b < 0.25, 0 < c < 0.3, 0 < d < 0.6, a + b + c + d = 1, and also satisfies electrical neutrality.

2. The positive electrode material according to claim 1, characterized in that 0.05 ≤ a + b + c < 1.

3. A method for preparing a positive electrode material according to claim 1, wherein the method is: Chemical formula Na α M ａ Li ｂ Cu ｃ Ti ｄ O ２＋β According to the atomic number ratios of Na element, M element, Li element, Cu element, and Ti element in [chemical formula NaM LiCuTiO], an appropriate amount of a Na element-containing compound, an M element-containing compound, a Li element-containing compound, a Cu element-containing compound, and a Ti element-containing compound are weighed and mixed to obtain a mixture; a mixing step A method for preparing a cathode material according to claim 1, characterized by comprising a calcination step of calcining the mixture to obtain a sodium ion cathode material by multi-element co-doping.

4. The M-element-containing compound, the Li-element-containing compound, the Cu-element-containing compound, and the Ti-element-containing compound are independently at least one of the following: metal oxides, metal nitrates, metal sulfates, metal carbonates, and metal chlorides, and / or The preparation method according to claim 3, characterized in that the Na element-containing compound is at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

5. The amount of the Na-containing compound weighed is 100% to 110% of the theoretical amount calculated according to the atomic ratio of Na, M, Li, Cu, and Ti, and / or The preparation method according to claim 3 or 4, characterized in that the amount of the Li-containing compound weighed is 100% to 110% of the theoretical amount.

6. The preparation method according to claim 3, characterized in that the mixing step includes mixing the Na-containing compound, the M-containing compound, the Li-containing compound, the Cu-containing compound, and the Ti-containing compound and mechanically milling them to obtain the mixture, wherein the speed of mechanical milling is 100 rpm to 1000 rpm and the time is 1 hour to 48 hours.

7. The preparation method according to claim 3, characterized in that the firing temperature is 700°C to 1050°C, the time is 6 hours to 36 hours, and the heating rate is 1°C / min to 20°C / min.

8. A method for preparing a positive electrode material according to claim 1, wherein the method is: Chemical formula MCO ３ or M(OH) ２ Depending on the atomic ratio of element M, an appropriate amount of element M-containing nitrate or sulfate is weighed out and dissolved in water, the pH is adjusted with a precipitating agent and a complexing agent to allow for uniform precipitation, and after drying, the precursor MCO is formed. ３ or M(OH) ２ A precursor acquisition step to obtain the following, Chemical formula Na α M ａ Li ｂ Cu ｃ Ti ｄ O ２＋β Depending on the atomic ratio of Na, M, Li, Cu, and Ti elements in the compound, a Na-containing compound, a Li-containing compound, a Cu-containing compound, a Ti-containing compound, and the precursor MCO are used. ３ or M(OH) ２ A mixing step involves weighing out an appropriate amount and mixing it to obtain a mixture, A method for preparing a cathode material according to claim 1, characterized by comprising a calcination step of calcining the mixture to obtain a sodium ion cathode material by multi-element co-doping.

9. The Li-containing compound, the Cu-containing compound, and the Ti-containing compound are independently at least one of the following: metal oxides, metal nitrates, metal sulfates, metal carbonates, and metal chlorides, and / or The preparation method according to claim 8, characterized in that the Na element-containing compound is at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

10. The amount of the Na-containing compound weighed is 100% to 110% of the theoretical amount calculated according to the atomic ratio of Na, M, Li, Cu, and Ti, and / or The preparation method according to claim 8 or 9, characterized in that the amount of the Li-containing compound weighed is 100% to 110% of the theoretical amount.

11. The preparation method according to claim 8, characterized in that the pH of the precursor acquisition step is 7.5 to 13, the precipitating agent is sodium hydroxide or sodium carbonate, the complexing agent is aqueous ammonia, the drying temperature is 80°C to 150°C, and / or the drying time is 6 hours to 48 hours.

12. The mixing step involves the Na element-containing compound and the precursor MCO. ３ or M(OH) ２ The preparation method according to claim 8, comprising mixing the Li-containing compound, the Cu-containing compound, and the Ti-containing compound and mechanically milling them to obtain the mixture, wherein the speed of mechanical milling is 100 rpm to 1000 rpm and the time is 1 hour to 48 hours.

13. The preparation method according to claim 8, characterized in that the firing temperature is 700°C to 1050°C, the time is 6 hours to 36 hours, and the heating rate is 1°C / min to 20°C / min.

14. A sodium-ion battery, characterized in that the battery includes the positive electrode material described in claim 1.

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