Sodium Oxide-Containing Cathode Material, Method for Producing the Same, Use Thereof, Cathode Plate, and Use Thereof

Abstract

The present invention relates to the technical field of sodium ion batteries, and discloses a sodium oxide-containing positive electrode material, its preparation method and use, and a positive electrode plate and its use. The content of soluble base on the surface of the positive electrode material satisfies the following conditions: (1) m(Na2CO3)+m(NaOH)≦15000ppm, (2) 0.1≦m(Na2CO3) / m(NaOH)≦1. The sodium metal oxide-containing positive electrode material has a low content of soluble base on the surface, and when used in a sodium ion battery, it can provide the battery with high capacity, high rate and high safety, and can sustain the deintercalation / intercalation reaction of sodium ions without obvious reduction in battery capacity.

Description

Technical Field

[0001] Cross - reference to related applications This application claims the benefit of Chinese Patent Application No. 202210334270.0, filed on March 30, 2022, the content of which is incorporated herein by reference.

[0002] The present invention relates to the technical field of sodium - ion batteries, and specifically relates to a sodium - oxide - containing positive electrode material, a method for manufacturing the same and its use, as well as a positive electrode plate and its use.

Background Art

[0003] Lithium - ion batteries have been successfully applied to portable electronic products. Currently, the application of lithium - ion batteries is gradually expanding to fields such as large - scale energy storage power grids and electric vehicles. However, when the lithium resources are limited and the demand for lithium - ion batteries increases significantly, the problem of high cost may occur, and the development of alternative energy storage systems is necessary. In recent years, sodium - ion batteries have attracted attention again because sodium resources are abundant and inexpensive.

[0004] In recent years, the development of new electrode materials for sodium - ion batteries has been actively carried out. Due to their easy synthesis and electrochemical activity, layered transition metal oxides Na x MeO2 (Me is usually a transition metal) have been studied. Among them, inexpensive and environmentally friendly α - Na x FeO2 and Na x MnO2 have received extensive attention. α - Na x FeO2 has a reversible capacity of about 80 mAh·g -1 at a voltage platform of about 3.3 V. However, when α - Na 1-x FeO2 is charged to x > 0.5, the insertion of Na + into the host structure is hindered by irreversible structural changes. The layered - structured Na x MnO2 material has an initial capacity of 150 mAh·g -1exceeds this value, but its capacity rapidly decays, limiting its application. Furthermore, since sodium is highly reactive, x MnO2 materials usually have a high content of soluble bases on their surfaces during the preparation process, and + the deintercalation / intercalation of sodium and the decomposition / gas generation during charge and discharge are inhibited, leading to a decrease in the capacity of the material, as well as a decline in cycle performance and safety.

[0005] Therefore, the development of a layered Na x MnO2 cathode material for sodium-ion batteries with high capacity, long cycle life, and high rate performance is of great significance.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to solve the drawbacks in the prior art, where the content of soluble bases on the surface of sodium metal oxide-containing materials is too high, resulting in a decrease in the safety of the materials, a decline in discharge specific capacity and rate performance, and serious side reactions during the cycling process, leading to deterioration of cycle performance. To achieve this, a sodium metal oxide-containing cathode material is provided, which has a low content of soluble bases on the surface. When used in a sodium-ion battery, it imparts high capacity, high rate, and high safety to the battery, and can continuously carry out the deintercalation / intercalation reaction of sodium ions without significantly reducing the battery capacity. The present invention also provides a method for manufacturing and using this cathode material, as well as a positive electrode plate and its use.

Means for Solving the Problems

[0007] To achieve the above object, a first aspect of the present invention provides a sodium oxide-containing cathode material, wherein the content of soluble bases on the surface satisfies the following conditions: (1) m(Na2CO3) + m(NaOH) ≤ 15000 ppm, (2) 0.1 ≤ m(Na2CO3) / m(NaOH) ≤ 1.

[0008] The second aspect of the present invention is subjecting a sodium-manganese-iron-containing cathode material precursor to a first sintering, cooling, crushing, and sieving to obtain the sodium oxide-containing cathode material, wherein in the first sintering, an oxygen-containing atmosphere is introduced, the introduction amount of the oxygen-containing atmosphere is 1 to 15 m 3 / h, the humidity of the oxygen-containing atmosphere is 10 RH% or less, the temperature T1 of the first sintering satisfies the condition of 500×(1 + y) ≤ T1 ≤ 400×(3 - y) °C, where y is the content of Mn in the sodium-manganese-iron oxide-containing cathode material, the heat preservation time of the first sintering is 6 to 20 h, and the heating rate of the first sintering is 10 °C / min or less. A method for manufacturing a sodium oxide-containing cathode material is provided.

[0009] The third aspect of the present invention provides a sodium oxide-containing cathode material manufactured by the above manufacturing method.

[0010] The fourth aspect of the present invention includes at least 80 wt% of a sodium oxide-containing cathode material based on the total weight of the positive electrode plate, wherein the sodium oxide-containing cathode material is the above sodium oxide-containing cathode material. A positive electrode plate is provided.

[0011] The fifth aspect of the present invention provides the use of the above sodium oxide-containing cathode material or the above positive electrode plate in the use of a sodium ion battery.

Advantages of the Invention

[0012] According to the above technical solution, the sodium oxide-containing cathode material, its manufacturing method and use, and the positive electrode plate and its use according to the present invention can obtain the following beneficial effects. The sodium oxide-containing cathode material according to the present invention has a low content of soluble base on the surface. When used in a sodium-ion battery, it imparts high capacity, high rate, and high safety to the battery, and can continuously perform the deintercalation / intercalation reaction of sodium ions without significantly reducing the battery capacity. Furthermore, the sodium oxide-containing cathode material according to the present invention contains a specific doping element, which promotes the reaction between sodium and metal oxide or metal hydroxide, reduces the content of soluble base on the surface of the material, stabilizes the surface structure of the material particles, the interfacial strength between particles, or the grain boundary structure between primary crystal grains, prolongs the cycle life of the battery containing the cathode material, and further increases the transport ability of sodium ions between particles and interfaces, thereby improving the rate performance of the battery containing the cathode material. In the manufacturing method of the sodium oxide-containing cathode material according to the present invention, by introducing a specific oxygen-containing atmosphere and performing roasting under specific conditions, the content of soluble base on the surface of the manufactured sodium oxide-containing cathode material can be significantly reduced, and the charge-discharge capacity, cycle rate, cycle life, and safety of the sodium-ion battery containing the cathode material can be significantly improved.

Brief Description of the Drawings

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BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The endpoints and any values within the ranges disclosed in this specification are not limited to the exact ranges or values, but should be understood to include values close to these ranges or values. In the case of numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this specification.

[0015] A first aspect of the present invention provides a sodium oxide-containing positive electrode material, wherein the content of soluble base on the surface satisfies the conditions: (1) m(Na2CO3) + m(NaOH) ≤ 15000 ppm, and (2) 0.1 ≤ m(Na2CO3) / m(NaOH) ≤ 1.

[0016] In the present invention, the sodium metal oxide-containing positive electrode material has a low content of soluble base on the surface. When used in a sodium ion battery, it imparts high capacity, high rate, and high safety to the battery, and can continuously perform the deintercalation / intercalation reaction of sodium ions without significantly reducing the battery capacity.

[0017] In the present invention, due to the low content of soluble base on the surface of the sodium oxide-containing positive electrode material, it is possible to avoid the increase in the content of non-electrochemically active substances in the positive electrode material and the resulting decrease in the charge-discharge capacity of the sodium ion battery caused by too high a content of soluble base on the surface of the positive electrode material. Also, it is possible to avoid the increase in the thickness of the inactive layer on the surface of the positive electrode material and the impedance of the positive electrode material and the resulting decrease in rate performance caused by too high a content of soluble base on the surface.

[0018] Furthermore, due to the low content of soluble base on the surface of the sodium oxide-containing positive electrode material according to the present invention, in the continuous charge-discharge cycles of the battery, it is possible to avoid side reactions between the soluble base on the surface of the material and the electrolyte solution, which would otherwise promote the consumption of the electrolyte and gas generation, reduce the cycle performance and safety of the battery, and in severe cases cause battery failure.

[0019] Furthermore, the content of soluble base on the surface of the positive electrode material satisfies (1) m(Na2CO3) + m(NaOH) ≤ 12000 ppm, (2) 0.1 ≤ m(Na2CO3) / m(NaOH) ≤ 0.6.

[0020] In the present invention, the content of soluble base on the surface of the positive electrode material is tested by a Metrohm 888 / 905 apparatus.

[0021] According to the present invention, the content of soluble base on the surface of the positive electrode material heat-treated under the conditions of 500 to 900 °C satisfies △λ[m(Na2CO3)+m(NaOH)]≦10%, △λ[m(Na2CO3) / m(NaOH)]≦50%,

Number

[0022] In the present invention, when the positive electrode material is heat-treated at a high temperature, the change value of the absolute content of soluble base on the surface of the positive electrode material and the absolute change value of the content ratio of Na2CO3 and NaOH on the surface are both small before and after the heat treatment. From this, it is clear that the surface structure of the material is stable, and it is difficult for soluble base to diffuse into the bulk of the material or participate in the reaction even at high temperatures. Thereby, the sodium ion battery manufactured with this positive electrode material has high charge and discharge capacity, high cycle rate, long cycle life, and excellent safety.

[0023] Furthermore, △λ[m(Na2CO3)+m(NaOH)]≦5%.

[0024] Furthermore, △λ[m(Na2CO3) / m(NaOH)]≦30%.

[0025] According to the present invention, the cathode material has a full width at half maximum (FWHM) of the (003) crystal plane obtained by XRD (003) and a full width at half maximum (FWHM) of the (104) crystal plane (104) such that 0.1 ≦ FWHM (003) ≦ 0.3, 0.1 ≦ FWHM (104) ≦ 0.4, satisfying the conditions.

[0026] In the present invention, the cathode material has a full width at half maximum (FWHM) of the (003) crystal plane obtained by XRD (003) and a full width at half maximum (FWHM) of the (104) crystal plane (104) satisfying the above conditions. From this, it is clear that the crystallinity of the cathode material and the content of low-soluble bases on the surface are appropriate. As a result, the sodium-ion battery manufactured with this cathode material has high charge-discharge capacity, high cycle rate, long cycle life, and excellent safety.

[0027] Furthermore, the cathode material has a full width at half maximum (FWHM) of the (003) crystal plane obtained by XRD (003) and a full width at half maximum (FWHM) of the (104) crystal plane (104) such that 0.13 ≦ FWHM (003) ≦ 0.24, 0.15 ≦ FWHM (104) ≦ 0.30, satisfying the conditions.

[0028] According to the present invention, the cathode material has a full width at half maximum (FWHM) of the (003) crystal plane obtained by XRD (003) and a full width at half maximum (FWHM) of the (104) crystal plane (104) such that 0.5 ≦ FWHM (003) / FWHM (104) ≦ 1.2, satisfying the conditions.

[0029] In the present invention, due to the crystallinity of the positive electrode material having the above structural characteristics, good structural stability, and low content of soluble base on the surface, the sodium ion battery manufactured with the positive electrode material has high charge-discharge capacity, high cycle rate, long cycle life, and excellent safety.

[0030] Furthermore, 0.7 ≦ FWHM (003) / FWHM (104) ≦ 1.

[0031] According to the present invention, the peak area S (003) of the (003) crystal plane and the peak area S (104) of the (104) crystal plane obtained by XRD for the positive electrode material satisfy 0.5 ≦ S (003) / S (104) ≦ 1.5.

[0032] In the present invention, since the peak area S (003) of the (003) crystal plane and the peak area S (104) of the (104) crystal plane obtained by XRD for the positive electrode material satisfy the above conditions, it is clear that the positive electrode material has good structural stability and appropriate crystal plane distribution. Therefore, the sodium ion battery manufactured with the positive electrode material has high charge-discharge capacity, high cycle rate, long cycle life, and excellent safety. Furthermore, 0.7 ≦ S (003) / S (104) ≦ 1.2.

[0033] According to the present invention, the tap density of the positive electrode material is 1.2 g / cm 3 or more, and the compression density of the positive electrode material is 2.5 g / cm 3 or more.

[0034] In the present invention, since the positive electrode material has a high tap density and a high compression density, the sodium ion battery manufactured with the positive electrode material has high electrode density, high energy density, long cycle life, and excellent safety.

[0035] Furthermore, the tap density of the positive electrode material is 1.5 g / cm 3 or more, preferably 1.8 g / cm 3 or more, and the compression density of the positive electrode material is 2.8 g / cm 3 or more, preferably 3.2 g / cm 3 or more.

[0036] According to the present invention, the BET specific surface area of the positive electrode material is 0.5 m 2 / g ≤ BET ≤ 4 m 2 / g, preferably, 1.5 m 2 / g ≤ BET ≤ 3 m 2 / g satisfies the condition.

[0037] According to the present invention, the positive electrode material has a composition represented by the general formula shown in Formula I. Na 1-x [Mn y Fe z M u M' j O 2-w F w Formula I (where 0 ≤ x ≤ 0.4, 0.2 ≤ y ≤ 0.6, 0.1 ≤ z ≤ 0.4, 0 < u ≤ 0.5, 0 < j ≤ 0.1, 0 ≤ w ≤ 0.1, M is at least one element selected from Li, Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, Os, Pr, Re, Ru, Sr, Sm, and Ta, and M' is at least one element selected from Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, Os, Pr, Re, Ru, Sr, Sm, and Ta.)

[0038] In the present invention, the sodium oxide-containing cathode material according to the present invention contains a specific doping element, whereby the reaction between sodium and the metal oxide or metal hydroxide is promoted, the content of soluble base on the surface of the material is reduced, and the surface structure of the material particles, the interfacial strength between particles, or the grain boundary structure between primary crystal grains is stabilized, the cycle life of the battery including the cathode material is prolonged, and further, the transport ability of sodium ions between particles and interfaces is increased, and the rate characteristics of the battery including the cathode material can be improved.

[0039] Furthermore, 0.05 ≦ x ≦ 0.3, 0.3 ≦ y ≦ 0.5, 0.15 ≦ z ≦ 0.35, 0 < u ≦ 0.3, 0 < j ≦ 0.05, 0 ≦ w ≦ 0.05, M is at least one element selected from Li, Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, and Sr, and M' is at least one element selected from Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, and Sr.

[0040] In one specific embodiment of the present invention, M is at least one element selected from Co, Ti, Sc, Zr, W, Mg, Y, Cr, and Ta. The above specific types of elements can promote the reaction between sodium and the metal oxide or metal hydroxide, reduce the content of soluble base on the surface of the cathode material, stabilize the crystal structure of the material, improve the rate characteristics of the battery manufactured with the cathode material, and extend the cycle life.

[0041] In one specific embodiment of the present invention, M is at least one element selected from V, Ti, Zr, Mo, Nb, La, and W. The above specific types of elements can form Na3VO4, Na2Ti3O7, Na2ZrO3, Na2MoO4, NaNbO3, LaMnO on the surface of the particles of the cathode material or at the interfaces between particles. 3.6It can form substances such as Na2WO4, stabilize the surface structure of the material particles, the interfacial strength between particles, and the grain boundary structure between primary crystal grains, reduce the content of soluble base on the surface of the cathode material, extend the cycle life of the battery manufactured with the cathode material, accelerate the transport of sodium ions between particles and interfaces, and improve the rate performance of the battery manufactured with the cathode material.

[0042] In the present invention, by using an appropriate additive (additive M), the reaction between sodium and metal oxide or metal hydroxide or metal carbonate is promoted, the sodiation reaction is made more sufficient, the content of soluble base on the surface of the material is reduced, the DCIR value of the direct current internal resistance and the gas generation amount of the material in the cycle are decreased, the capacity of the material is improved, and the cycle life can be extended.

[0043] The second aspect of the present invention is including the step of subjecting the sodium-manganese-iron-containing cathode material precursor to a first sintering, cooling, crushing, and sieving to obtain the sodium oxide-containing cathode material, in the first sintering, an oxygen-containing atmosphere is introduced, the introduction amount of the oxygen-containing atmosphere is 1 to 15 m 3 / h, the humidity of the oxygen-containing atmosphere is 10 RH% or less, the temperature T1 of the first sintering satisfies the condition of 500×(1 + y) ≤ T1 ≤ 400×(3 - y) °C, where y is the content of Mn in the sodium-manganese-iron oxide-containing cathode material, the heat preservation time of the first sintering is 6 to 20 h, the heating rate of the first sintering is 10 °C / min or less, and a method for manufacturing a sodium oxide-containing cathode material is provided.

[0044] In the present invention, the sintering temperature in the production of the sodium oxide-containing cathode material is clearly defined, and this temperature depends on the content of Mn in the sodium-manganese-iron oxide-containing cathode material. If the sintering temperature is too high, the primary particles contained in the sodium oxide become large, and the aggregation becomes serious, which is disadvantageous for the capacity of the cathode material to be exerted. On the other hand, if the sintering temperature is too low, the precursor cannot undergo a complete reaction during sintering, and it is difficult to generate an appropriate crystal structure, so low capacity and low cycle characteristics are exhibited.

[0045] In the present invention, in the method for producing the sodium oxide-containing cathode material, a specific oxygen-containing atmosphere is introduced, and roasting is carried out under specific conditions, so that the content of soluble base on the surface of the produced sodium oxide-containing cathode material is greatly reduced, and the charge-discharge capacity, cycle rate, cycle life and safety of the sodium-ion battery including the cathode material can be greatly improved.

[0046] Furthermore, in the production method according to the present invention, both the production cost of the cathode material and the characteristic indexes of the produced cathode material can be considered.

[0047] In the present invention, when the oxygen-containing atmosphere contains air and oxygen gas, the ratio of the introduction amounts of the air and the oxygen gas is 1 to 5:1, preferably 1 to 3:1.

[0048] Furthermore, the introduction amount of the oxygen-containing atmosphere is 2 to 8 m 3 / h, and the humidity of the oxygen-containing atmosphere is 6RH% or less.

[0049] Furthermore, the oxygen-containing atmosphere contains air and / or oxygen gas.

[0050] Furthermore, the temperature T1 of the first sintering satisfies the condition of 550×(1 + y) ≦ T1 ≦ 380×(3 - y) °C.

[0051] Furthermore, the heat preservation time of the first sintering is 8 to 15 h.

[0052] Furthermore, the heating rate of the first sintering is 8 °C / min or less.

[0053] According to the present invention, the sodium-manganese-iron-containing cathode material precursor is [Mn y Fe z M u (OH)2, a mixture of a Na source and an additive M, [Mn y Fe z M u CO3, a mixture of a Na source and an additive M, or a mixture of an oxide of Mn and / or a hydroxide of Mn and an oxide of Fe and / or a hydroxide of Fe with a molar ratio of n(Mn):n(Fe)=y:z and a Na source and an additive M, selected from In the sodium-manganese-iron oxide-containing cathode material precursor, the usage amount of the Na source satisfies 0.6 ≦ n(Na) / n(Mn + Fe + M) ≦ 1, In the sodium-manganese-iron oxide-containing cathode material precursor, the usage amount of the additive M satisfies 0 < n(M) / n(Mn + Fe + M) ≦ 0.5, 0.2 ≦ y ≦ 0.6, 0.1 ≦ z ≦ 0.4, 0 ≦ u ≦ 0.5, and M is at least one element selected from Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, Os, Pr, Re, Ru, Sr, Sm, and Ta.

[0054] In the present invention, by controlling the form, microstructure, particle size, etc. of each component (such as a sodium source, metal oxide, metal hydroxide, or metal carbonate, etc.) contained in the sodium-manganese-iron-containing cathode material precursor mixture, the uniformity of material mixing is ensured, and a local increase in sodium content due to uneven material mixing is avoided. Specifically, in the present invention, the D 50 ≦ 1 μm of the sodium source, D 50 ≦ 2 μm of the metal oxide (such as an oxide of Fe or an oxide of Mn), the metal hydroxide (such as a hydroxide of Mn or a hydroxide of Fe) or the metal carbonate ([Mn y Fe z M u CO3)nD 50By controlling it to be ≤15 μm, the uniformity of material mixing is ensured, and it is avoided that the local increase in sodium content caused by uneven material mixing leads to an undesirable decrease in the comprehensive properties of the produced sodium oxide-containing cathode material.

[0055] Manufacture of the precursor by the solid-phase method In one specific embodiment of the present invention, the sodium-manganese-iron-containing cathode material precursor is prepared by uniformly mixing manganese oxide and / or manganese hydroxide, iron oxide and / or iron hydroxide with a molar ratio of n(Mn):n(Fe)=y:z, a Na source, and an additive M, and obtaining the sodium-manganese-iron-containing cathode material precursor.

[0056] In the present invention, according to the above method, since manganese oxide and / or manganese hydroxide, iron oxide and / or iron hydroxide, a Na source, and an additive M are mixed in solid form, it is easy to adjust the operation and the composition ratio, and there is an advantage that the compression density of the produced cathode material is high. The produced sodium-manganese-iron-containing cathode material precursor has the effects of low cost, easy production, easy adjustment of the composition, and excellent compression density and the like.

[0057] In the present invention, in order to improve the uniformity of mixing of each component, preferably, an appropriate solvent, such as ethanol, is added during mixing.

[0058] In the present invention, the Na source is at least one selected from sodium hydroxide, sodium carbonate, sodium sulfate, sodium oxalate, sodium chloride, sodium citrate, and sodium fluoride.

[0059] In the present invention, the additive M is at least one selected from oxides, hydroxides, oxyhydroxides, phosphates, fluorides, borides, carbonates, and oxalates containing element M.

[0060] In the present invention, the usage amount of the additive M is set such that 0 < n(M) / n(Mn + Fe + M) ≤ 0.5, preferably 0.1 ≤ n(M) / n(Mn + Fe + M) ≤ 0.4, in the sodium-manganese-iron-containing cathode material precursor.

[0061] In the present invention, the usage amount of the sodium source is set such that 0.6 ≤ n(Na) / n(Mn + Fe + M) ≤ 1, preferably 0.7 ≤ n(Na) / n(Mn + Fe + M) ≤ 0.95, in the sodium-manganese-iron-containing cathode material precursor.

[0062] Production of the precursor by the liquid phase method In another specific embodiment of the present invention, the sodium-manganese-iron-containing cathode material precursor is (1) A mixed salt solution is prepared from Mn salt and Fe salt at a molar ratio of n(Mn):n(Fe) = y:z. A precipitant solution, a complexing agent solution, and an additive M solution are respectively prepared from a precipitant, a complexing agent, and the additive M. The mixed salt solution, the precipitant solution, and the complexing agent solution are merged and introduced into a reaction kettle to carry out a coprecipitation reaction to obtain a solid-liquid mixture, which is filtered to obtain a filter cake. The filter cake is dried and sieved to obtain an intermediate. (2) The intermediate, a sodium source, and an optional additive M are uniformly mixed to obtain the sodium-manganese-iron-containing cathode material precursor by the method.

[0063] In the present invention, by the above method, the Mn salt solution, the Fe salt solution, and the additive M solution are coprecipitated in the form of a solution with a precipitant solution and a complexing agent solution to obtain an intermediate. By uniformly mixing the intermediate with a sodium source and an optional additive M, the element distribution becomes more uniform, the activity of the precursor is high, the morphology is controllable, and excellent effects such as facilitating the high-temperature reaction and morphology control of the produced sodium-manganese-iron-containing cathode material precursor can be obtained.

[0064] In the present invention, the sodium source is at least one selected from sodium hydroxide, sodium carbonate, sodium sulfate, sodium oxalate, sodium chloride, sodium citrate, and sodium fluoride.

[0065] In the present invention, the additive M is at least one selected from oxides, hydroxides, oxyhydroxides, phosphates, fluorides, borides, carbonates, and oxalates containing the element M.

[0066] In the present invention, in steps (1) and (2), there is no particular limitation on the usage amount of the additive M, and it is only necessary to ensure that the usage amount of the additive M satisfies 0 < n(M) / n(Mn + Fe + M) ≤ 0.5, preferably 0.1 ≤ n(M) / n(Mn + Fe + M) ≤ 0.4 in the sodium-manganese-iron-containing cathode material precursor.

[0067] In the present invention, the usage amount of the sodium source satisfies 0.6 ≤ n(Na) / n(Mn + Fe + M) ≤ 1, preferably 0.7 ≤ n(Na) / n(Mn + Fe + M) ≤ 0.95 in the sodium-manganese-iron-containing cathode material precursor.

[0068] In the present invention, there is no particular limitation on the types of the precipitant and the complexing agent, and they may be ordinary types of precipitants and complexing agents in this field. For example, the precipitant is sodium hydroxide and / or sodium carbonate, and the complexing agent is aqueous ammonia. In the present invention, there is no particular limitation on the concentrations of the mixed salt solution, the precipitant solution, and the complexing agent solution, and the ordinary concentrations in this field can be used.

[0069] In the present invention, the conditions of the coprecipitation reaction include that the reaction temperature is 25 to 60 °C, the pH value is 8 to 11, the stirring rotation speed is 200 to 1000 rpm, and the reaction time is 10 to 30 h.

[0070] Washing According to the present invention, the method further includes the steps of mixing the sodium oxide-containing cathode material with a washing liquid, washing, filtering to obtain a filter cake, and drying the filter cake.

[0071] In the present invention, by further washing the sodium oxide-containing cathode material with a cleaning solution, the content of soluble base on the surface of the produced sodium oxide-containing cathode material is further reduced, and the charge-discharge capacity, cycle rate, cycle life and safety of the sodium-ion battery produced with the cathode material can be further improved.

[0072] According to the present invention, the cleaning solution is selected from water and / or acidic solution.

[0073] According to the present invention, the weight ratio of the sodium oxide-containing cathode material to the cleaning solution is 0.5-3:1, preferably 1-2.5:1.

[0074] According to the present invention, the concentration of the acidic solution is 0.1-5 mol / L.

[0075] In the present invention, the acidic solution may be a normal type of acidic solution in this field, such as acetic acid solution.

[0076] According to the present invention, the cleaning conditions include washing at a temperature of 0-25°C for 3-60 min while stirring at 100-1000 rpm.

[0077] Furthermore, the cleaning conditions include washing at a temperature of 5-15°C for 5-30 min while stirring at 300-800 rpm.

[0078] Coating According to the present invention, the method further includes the step of ball-milling and mixing the sodium oxide-containing cathode material with a coating agent M', then subjecting it to a second sintering, cooling, crushing, and sieving to obtain the sodium oxide-containing cathode material. In the second sintering, an oxygen-containing atmosphere is introduced. The introduction amount of the oxygen-containing atmosphere is 1-15 m 3 / h, and the humidity of the oxygen-containing atmosphere is 10 RH% or less. The temperature T2 of the second sintering satisfies the condition of 250×(1 + y) ≤ T2 ≤ 300×(3 - y)°C, where y is the content of Mn in the sodium-manganese-iron-containing cathode material, The heat preservation time of the second sintering is 4 to 20 h, The heating rate of the second sintering is 10°C / min or less.

[0079] In the present invention, by coating the sodium oxide-containing cathode material with the coating agent M', the content of soluble base on the surface of the produced sodium oxide-containing cathode material is further reduced, and the charge-discharge capacity, cycle rate, cycle life and safety of the sodium-ion battery produced with the cathode material can be further improved.

[0080] Furthermore, the introduction amount of the oxygen-containing atmosphere is 2 to 8 m 3 / h, and the humidity of the oxygen-containing atmosphere is 8RH% or less. The temperature T2 of the second sintering satisfies the condition of 275×(1 + y) ≤ T2 ≤ 275×(3 - y)°C, where y is the content of Mn in the sodium-manganese-iron-containing cathode material, The heat preservation time of the second sintering is 4 to 12 h, The heating rate of the second sintering is 8°C / min or less.

[0081] According to the present invention, the usage amount of the coating agent M' is 0 ≤ n(M') / n(Mn + Fe + M + M') ≤ 0.1, preferably 0 < n(M') / n(Mn + Fe + M + M') ≤ 0.05 in the sodium oxide-containing cathode material.

[0082] In the present invention, the coating agent M' is at least one selected from oxides, hydroxides, oxyhydroxides, phosphates, fluorides, borides, carbonates, and oxalates containing the element M'.

[0083] In one specific embodiment of the present invention, the manufacturing method of the sodium oxide-containing cathode material includes the following steps.

[0084] S1-1: Mix an oxide of Mn and / or a hydroxide of Mn and an oxide of Fe and / or a hydroxide of Fe with a molar ratio of n(Mn):n(Fe) = y:z uniformly with a Na source and an additive M to obtain the sodium-manganese-iron-containing cathode material precursor.

[0085] S1-2: (i) Prepare a mixed salt solution of a Mn salt and an Fe salt with a molar ratio of n(Mn):n(Fe) = y:z, and prepare a precipitant, a complexing agent, and an additive M in a precipitant solution, a complexing agent solution, and an additive M solution respectively. Then, merge the mixed salt solution, the precipitant solution, and the complexing agent solution and introduce them into a reaction kettle to perform a coprecipitation reaction to obtain a solid-liquid mixture. Filter it to obtain a filter cake, dry the filter cake, and sieve it to obtain an intermediate. (ii) Uniformly mix the intermediate, the sodium source, and an optional additive M to obtain the sodium-manganese-iron-containing cathode material precursor.

[0086] S2: Subject the sodium-manganese-iron-containing cathode material precursor to a first sintering, cool it, crush it, and sieve it to obtain a first sintering product. In the first sintering, an oxygen-containing atmosphere is introduced. The introduction amount of the oxygen-containing atmosphere is 1 - 15 m 3 / h, and the humidity of the oxygen-containing atmosphere is 10 RH% or less. The temperature T1 of the first sintering satisfies the condition of 500×(1 + y) ≤ T1 ≤ 400×(3 - y) °C, where y is the content of Mn in the sodium-manganese-iron oxide-containing cathode material. The heat preservation time of the first sintering is 6 - 20 h. The heating rate of the first sintering is 10 °C / min or less.

[0087] S3: After uniformly mixing the first sintering product and a coating agent M', subject it to a second sintering, cool it, crush it, and sieve it to obtain a second sintering product. In the second sintering, an oxygen-containing atmosphere is introduced. The introduction amount of the oxygen-containing atmosphere is 1 - 15 m 3 / h, and the humidity of the oxygen-containing atmosphere is 10 RH% or less. The temperature T2 of the second sintering satisfies the condition of 250×(1 + y) ≤ T2 ≤ 300×(3 - y) °C, where y is the content of Mn in the sodium-manganese-iron-containing cathode material, the heat preservation time of the second sintering is 4 to 20 h, and the heating rate of the second sintering is 10 °C / min or less.

[0088] S4: Optionally, the second sintering product is mixed with a cleaning liquid, washed, filtered to obtain a filter cake, and the filter cake is dried to obtain the sodium oxide-containing cathode material.

[0089] In the present invention, the second sintered material produced in step S3 can be directly used as the sodium oxide-containing cathode material in a sodium-ion battery. In order to further reduce the content of soluble base on the surface of the cathode material, preferably, the second sintering product is washed as in step S4 to obtain the sodium oxide-containing cathode material.

[0090] The third aspect of the present invention provides a sodium oxide-containing cathode material produced by the above production method.

[0091] In the present invention, when the sodium oxide-containing cathode material according to the present invention is used in a sodium-ion battery, the charge-discharge capacity, cycle rate, cycle life, and safety of the sodium-ion battery can be significantly improved.

[0092] For example, when the sodium oxide-containing cathode material according to the present invention is used in a 2025 button-type battery, in the charge-discharge range of 2 to 4.2 V, the battery has a 0.1C charge-discharge capacity of 130 mAh / g or more, and a 1C discharge capacity / 0.1C discharge capacity of 80% or more, preferably 85% or more.

[0093] At room temperature, the button-type battery has a capacity retention rate of 85% or more, preferably 90% or more, more preferably 92% or more after 100 cycles at 1C.

[0094] The fourth aspect of the present invention includes a sodium oxide-containing cathode material of at least 80 wt% based on the total weight of the cathode plate, wherein the sodium oxide-containing cathode material is the above-mentioned sodium oxide-containing cathode material, and provides a cathode plate characterized by this.

[0095] Furthermore, based on the total weight of the cathode plate, it contains at least 90 wt%, preferably at least 95 wt% of the sodium oxide-containing cathode material.

[0096] In the present invention, the cathode plate also contains ordinary auxiliaries in this field, such as a conductive agent and a binder PVDF. There are no particular limitations on the types and amounts of the conductive agent and the binder, and they may be of ordinary types and amounts in this field.

[0097] According to the present invention, the plate density of the cathode plate is 2.8 g / cm 3 or more, preferably 3 g / cm 3 or more, more preferably 3.2 g / cm 3 or more.

[0098] In the present invention, the plate density of the cathode plate can be obtained by weighing the mass of the plate active material and dividing it by the plate area.

[0099] The fifth aspect of the present invention provides the use of the above-mentioned sodium oxide-containing cathode material or the above-mentioned cathode plate in a sodium-ion battery.

[0100] Hereinafter, the present invention will be described in detail by examples. In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0101] In the following examples, the relevant characteristics are obtained by the following methods. Phase measurement: It is obtained by performing measurement with a SmartLab 9kW type X-ray diffractometer manufactured by Rigaku Corporation, Japan. Morphology measurement: It is obtained by performing measurement with an S-4800 type scanning electron microscope manufactured by Hitachi, Ltd., Japan. Measurement of surface residual base: It is measured by titration using a Tirando smart potentiometric titrator dedicated to Metrohmm888. Specific surface area: It is obtained by performing measurement using a Tristar II 3020 model specific surface area tester manufactured by Micromertics, USA. Tap density: It is obtained by performing measurement using a BT-30 model tap density tester manufactured by BAX.

[0102] Compression density: It is obtained by performing measurement using an MCP-PD51 model compression densitometer manufactured by Mitsubishi Chemical Corporation, Japan. Measurement of thermal stability: It is obtained by performing measurement using a TGA-DSC3 model thermogravimetric analysis tester manufactured by Mettler Toledo. Measurement of electrochemical performance: At 25 °C, a Neware battery measurement system is adopted, and electrochemical performance measurement is performed on a 2025 type button cell. The obtained button cell is subjected to charge and discharge measurement at 2 - 4.2 V and 0.1 C (0.1 C = 140 mAh / g) to evaluate the initial charge-discharge specific capacity and initial efficiency of the material. The obtained button cell is subjected to charge and discharge measurement at 2 - 4.2 V, 0.1 C, 0.2 C, 0.33 C, 0.5 C, 1 C, and 2 C respectively to evaluate the rate performance of the material. The obtained button cell is cycled 80 times at 2 V - 4.1 V and 1 C to evaluate the cycle performance of the material.

[0103] Example 1 (1) Manganese dioxide, ferric oxide, nickel oxide, copper oxide, and sodium carbonate are accurately weighed so that the molar ratio of manganese, iron, nickel, copper, and sodium elements is 4:2:2:2:8, an appropriate amount of ethanol mixed medium is added, and ball milling is performed to mix uniformly to obtain a precursor Q1 for a sodium-manganese-iron metal oxide-containing cathode material. (2) The precursor Q1 uniformly mixed above is put into a muffle furnace and heated from room temperature to 850 °C (y = 0.4), kept warm for 15 h, and the first sintering is performed with a heating rate of 5 °C / min. In the first sintering, dry air with a humidity of less than 5 RH% is 10 m 3It was continuously introduced at an introduction rate of / h. After natural cooling, it was crushed and sieved to obtain a sodium metal oxide-containing positive electrode material S1.

[0104] Examples 2 to 7 are similar to the manufacturing method of Example 1 and are shown in Table 1.

[0105]

Table 1-1

[0106]

Table 1-2

[0107] Unless otherwise specified, all of the above ratios and usage ratios in Table 1 are molar ratios, and M is the total molar amount of the doping element.

[0108] Example 8 (1) Manganese sulfate, iron sulfate, nickel sulfate, and copper sulfate were dissolved at a ratio such that the molar ratio of manganese, iron, nickel, and copper elements was 4:2:2:2 to obtain a mixed salt solution with a concentration of 2 mol / L. Sodium hydroxide was dissolved to obtain a precipitant solution with a concentration of 2 mol / L, and aqueous ammonia was dissolved to obtain a complexing agent solution with a concentration of 3 mol / L. The precipitant solution, the complexing agent solution, and the mixed salt solution were merged and added to a reaction kettle, and reacted at a temperature of 45 °C, a pH value of 10.5, and a stirring rotation speed of 700 rpm for 30 h. Then, the slurry was suction filtered, washed, and the filter cake was baked at 120 °C and then sieved to obtain an intermediate P8 with the chemical formula Mn 0.4 Fe 0.2 Ni 0.2 Cu 0.2 (OH)2. (2) Sodium carbonate and the precursor Q8 were uniformly mixed to obtain the precursor Q8. (3) The above precursor Q8 was placed in a muffle furnace and heated from room temperature to 850 °C (y = 0.4), held for 15 h, and the first sintering was carried out with a heating rate of 5 °C / min. In the first sintering, dry air with a humidity of 5 RH% was 10 m 3It was continuously introduced at an introduction rate of / h. After natural cooling, it was crushed and sieved to obtain the sodium metal oxide-containing cathode material S8. Specifically, the molar ratio of the amount of sodium carbonate in terms of Na element contained to the amount of the precursor in terms of Mn, Fe, Ni, and Cu elements contained is n(Na) / n(Mn + Fe + Ni + Cu) = 0.85:1.

[0109] Example 9 Sodium carbonate, intermediate P8, titanium dioxide, magnesium oxide, and cobalt oxide were ball-milled at a predetermined ratio and uniformly mixed. Next, they were placed in a muffle furnace and heated from room temperature to 800 °C (y = 0.28), held for 15 h, and the first sintering was carried out with a heating rate of 5 °C / min. In the first sintering, dry air with a humidity of 3RH% was continuously introduced at an introduction rate of 15 m 3 / h. After natural cooling, it was crushed and sieved to obtain the sodium metal oxide-containing cathode material S9. Specifically, the relationship of the molar ratios of the amount of sodium carbonate in terms of Na element contained, the amount of the precursor in terms of Mn, Fe, Ni, and Cu elements contained, and the amount of the additive in terms of Ti, Mg, and Co elements contained is n(Na) / n(Mn + Fe + Ni + Cu + Ti + Mg + Co) = 0.85:1, n(Mn + Fe + Ni + Cu) / n(Mn + Fe + Ni + Cu + Ti + Mg + Co) = 0.7:1, n(Ti) / n(Mn + Fe + Ni + Cu + Ti + Mg + Co) = 0.1:1, n(Mg) / n(Mn + Fe + Ni + Cu + Ti + Mg + Co) = 0.1:1, n(Co) / n(Mn + Fe + Ni + Cu + Ti + Mg + Co) = 0.1:1.

[0110] Example 10 (1) Manganese sulfate, iron sulfate, nickel sulfate, and copper sulfate were dissolved at a ratio such that the molar ratio of manganese, iron, nickel, and copper elements was 4:2:2:2 to form a mixed salt solution with a concentration of 2 mol / L. Sodium carbonate was dissolved to form a precipitant solution with a concentration of 2 mol / L, and aqueous ammonia was dissolved to form a complexing agent solution with a concentration of 3 mol / L. The precipitant solution, complexing agent solution, and mixed salt solution were combined and put into a reaction kettle, and reacted at a temperature of 40 °C, a pH value of 8.2, and a stirring rotation speed of 700 rpm for 20 h. Next, the slurry was suction filtered, washed, and the filter cake was baked at 120 °C and then sieved to obtain an intermediate P10 with the chemical formula Mn 0.4 Fe 0.2 Ni 0.2 Cu 0.2 CO3. (2) Sodium carbonate and intermediate P10 were uniformly mixed to obtain a precursor Q10. (3) The above precursor Q10 was put into a muffle furnace and heated from room temperature to 950 °C (y = 0.4), held for 15 h, and the first sintering was carried out with a heating rate of 5 °C / min. In the first sintering, dry air with a humidity of 5 RH% was continuously introduced at an introduction rate of 15 m 3 / h. After natural cooling, it was crushed and sieved to obtain a sodium metal oxide-containing positive electrode material S10. Specifically, the molar ratio of the amount of sodium carbonate used in terms of Na element contained to the amount of precursor used in terms of Mn, Fe, Ni, and Cu elements contained is n(Na) / n(Mn + Fe + Ni + Cu) = 0.8:1.

[0111] Example 11 The sodium metal oxide-containing positive electrode material S1 obtained in Example 1 and pure water were mixed in a beaker at a mass ratio of 2:1, stirred at a temperature of 5 °C and a stirring rotation speed of 200 rpm for 5 min, then the slurry was quickly suction filtered, and the filter cake was baked in a vacuum oven at 105 °C and then sieved to obtain a sodium metal oxide-containing positive electrode material S11.

[0112] Example 12 The sodium metal oxide-containing cathode material S8 obtained in Example 8 and an acetic acid solution with a concentration of 0.1 mol / L were mixed in a beaker at a mass ratio of 2:1, stirred at a temperature of 10 °C and a stirring rotation speed of 200 rpm for 30 min, then the slurry was quickly suction filtered, the filter cake was baked in a vacuum oven at 105 °C, and then sieved to obtain the sodium metal oxide-containing cathode material S12.

[0113] Example 13 The sodium metal oxide-containing cathode material S1 obtained in Example 1 and titanium dioxide as a coating agent were ball milled at a predetermined ratio and uniformly mixed, then placed in a muffle furnace and heated from room temperature to 600 °C (y = 0.36), held for 10 h, and the second sintering was carried out with a heating rate of 5 °C / min. In the second sintering, dry air with a humidity of 5 RH% was continuously introduced at an introduction rate of 10 m 3 / h. After natural cooling, it was crushed and sieved to obtain the sodium metal oxide-containing cathode material S13. Specifically, the molar ratio of the amount of the titanium dioxide used in terms of the contained Ti element to the amount of the precursors used in terms of the contained Mn, Fe, Ni, and Cu elements is n(Ti) / n(Mn + Fe + Ni + Cu + Ti) = 0.1:1.

[0114] Example 14 The sodium metal oxide-containing cathode material S8 obtained in Example 8 and zirconium fluoride were ball milled at a predetermined ratio and uniformly mixed, then placed in a muffle furnace and heated from room temperature to 700 °C (y = 0.36), held for 10 h, and the second sintering was carried out with a heating rate of 3 °C / min. In the second sintering, dry air with a humidity of 5 RH% was continuously introduced at an introduction rate of 10 m 3 / h. After natural cooling, it was crushed and sieved to obtain the sodium metal oxide-containing cathode material S14. Specifically, the molar ratio of the amount of the zirconium fluoride used in terms of the contained Zr element to the amount of the precursors used in terms of the contained Mn, Fe, Ni, and Cu elements is n(Zr) / n(Mn + Fe + Ni + Cu + Zr) = 0.1:1.

[0115] Example 15 The sodium metal oxide-containing cathode material S11 obtained in Example 11 and niobium oxide as a coating agent were ball-milled at a predetermined ratio and uniformly mixed, and then placed in a muffle furnace and heated from room temperature to 600 °C (y = 0.38), held for 15 h, and the heating rate was 5 °C / min for the second sintering. In the second sintering, dry air with a humidity of 10 RH% was continuously introduced at an introduction rate of 15 m 3 / h. After natural cooling, it was crushed and sieved to obtain a sodium metal oxide-containing cathode material S15. Specifically, the molar ratio of the amount of niobium oxide used in terms of the contained Nb element to the amount of the precursor used in terms of the contained Mn, Fe, Ni, and Cu elements is Nb / (Mn + Fe + Ni + Cu + Nb) = 0.05:1.

[0116] Example 16 The sodium metal oxide-containing cathode material S10 obtained in Example 10, aluminum oxide, and lanthanum oxide were ball-milled at a predetermined ratio and uniformly mixed, and then placed in a muffle furnace and heated from room temperature to 650 °C (y = 0.32), held for 10 h, and the heating rate was 3 °C / min for the second sintering. In the second sintering, dry air with a humidity of 5 RH% was continuously introduced at an introduction rate of 10 m 3 / h. After natural cooling, it was crushed and sieved to obtain an intermediate product of a sodium metal oxide-containing cathode material. The intermediate product of the sodium metal oxide-containing cathode material obtained above and a 0.1 mol / L ammonium sulfate solution were mixed in a beaker at a mass ratio of 1:1, stirred at a temperature of 3 °C and a stirring rotation speed of 500 rpm for 10 min, then the slurry was quickly suction-filtered, the filter cake was baked in a vacuum oven at 105 °C, and then sieved to obtain a sodium metal oxide-containing cathode material S16. Specifically, the molar ratios of the amounts of aluminum oxide used in terms of the contained Al element and lanthanum trioxide used in terms of the contained La element to the amount of the precursor used in terms of the contained Mn, Fe, Ni, and Cu elements are n(Al) / n(Mn + Fe + Ni + Cu + Al + La) = 0.1:1 and n(La) / n(Mn + Fe + Ni + Cu + Al + La) = 0.1:1.

[0117] Example 17 In step (1), except that nickel oxide and copper oxide were not added, and manganese, iron, and sodium elements were accurately weighed and mixed so that the molar ratio was 6:4:8 to produce a sodium metal oxide-containing positive electrode material S17, the same method as in Example 1 was used.

[0118] Comparative Example 1 In the sintering of step (2), except that dry air with a humidity of 30RH% was continuously introduced at an introduction rate of 10 m 3 / h to produce a sodium metal oxide-containing positive electrode material D1, the same method as in Example 1 was used.

[0119] Comparative Example 2 In step (2), except that the heat preservation time was shortened to 3 h and no dry gas was introduced during sintering to produce a sodium metal oxide-containing positive electrode material D2, the same method as in Example 8 was used. The compositions of the sodium oxide-containing positive electrode materials produced in the examples and comparative examples are shown in Table 2.

[0120]

Table 2

[0121] The structures and properties of the sodium oxide-containing positive electrode materials produced in the examples and comparative examples are shown in Table 3.

Table 3-1

[0122]

Table 3-2

[0123] As can be seen from Table 1, Table 2, and Table 3, in Examples S1 to S17, compared with Comparative Examples D1 and D2, FWHM (003) and FWHM (104) are smaller, and S (003) / S (104)is large, from which it is proved that the sodium oxide-containing cathode material according to the present invention has better crystallinity and structural stability. In Examples S1 to S17, compared with Comparative Examples D1 and D2, the content of m(Na2CO3)+m(NaOH) is significantly lower, from which it is proved that the sodium oxide-containing cathode material according to the present invention has a lower content of soluble base on the surface. In Examples S1 to S17, compared with Comparative Examples D1 and D2, the specific surface area is small, from which it is proved that the sodium oxide-containing cathode material according to the present invention has higher reaction activity and contributes to the deintercalation / intercalation of sodium ions and the exhibition of high capacity and rate performance. In Examples S1 to S17, compared with Comparative Examples D1 and D2, the tap density and compression density are high, from which it is proved that the sodium oxide-containing cathode material according to the present invention is advantageous for manufacturing a cathode plate with a high electrode density and improving the density of battery energy. In Examples S1 to S17, compared with Comparative Examples D1 and D2, the thermal decomposition temperature is high, from which it is proved that the sodium oxide-containing cathode material according to the present invention has higher safety. From the comparison of m(Na2CO3)+m(NaOH) between Example S10 and Example S16, the comparison of m(Na2CO3)+m(NaOH) between Example S11 and S15, and the comparison of m(Na2CO3)+m(NaOH) between Example S13 and Example S1, it is proved that the content of soluble base in the material can be significantly reduced by coating. From the comparison of m(Na2CO3)+m(NaOH) between Example S1 and Example S17, it is proved that element doping can reduce the content of soluble base in the material. From the comparison of m(Na2CO3)+m(NaOH) between Example S12 and Example S8, and the comparison of m(Na2CO3)+m(NaOH) between Example S11 and Example S1, it is proved that the content of soluble base in the material can be further significantly reduced by washing with water or treating with an acidic solution.

[0124] Figures 1, 2, 3, and 4 are the XRD patterns of the sodium oxide-containing cathode materials manufactured in Example 1, Example 12, Example 14, and Comparative Example 2, respectively. As can be seen from Figures 1 to 4, S of Example 1 (003) / S (104)is 0.83, and S of Example 12 (003) / S (104) is 0.76, and S of Example 14 (003) / S (104) is 0.92, and in all cases, they are larger than those of Comparative Example 2 (S (003) / S (104) is 0.45). Figures 5, 6, and 7 are SEM images of the sodium oxide-containing cathode materials manufactured in Example 1, Example 8, and Comparative Example 2, respectively. As can be seen from Figures 5 to 8, the sodium oxide-containing cathode material according to Example 1 has a uniform distribution, a smooth surface, and excellent crystallinity. The sodium oxide-containing cathode material according to Example 8 has a spherical shape, a uniform distribution, and excellent sphericity. The sodium oxide-containing cathode material manufactured in Comparative Example 2 has a non-uniform particle distribution, a rough surface, and poor crystallinity.

[0125] Measurement Example 1 The sodium oxide-containing cathode materials manufactured in the examples and comparative examples were placed in a muffle furnace and heated from room temperature to 600 °C, held for 10 h, and the heating rate was 5 °C / min. During sintering, air with a humidity of 25 RH% was continuously introduced at an introduction rate of 10 m 3 / h. After natural cooling, it was crushed and sieved to obtain the treated sodium oxide-containing cathode material, and the content of soluble residual base on its surface was measured. The results are shown in Table 4.

[0126]

Table 4

[0127] As can be seen from Table 4, as a result of heat treatment of the sodium oxide-containing cathode materials S1 to S17 according to the present invention under the conditions of high humidity (air with a humidity of 25% RH) and high temperature (600 °C), the absolute content change Δλ [m(Na2CO3) + m(NaOH)] and the ratio content change Δλ [m(Na2CO3) / m(NaOH)] of soluble bases on the surface are significantly smaller than those of Comparative Examples D1 and D2. From this, it can be seen that the sodium oxide-containing cathode material according to the present invention has a stable surface structure, is less likely to react with air, and even under the conditions of high humidity (air with a humidity of 25% RH) and high temperature (600 °C), the conversion of sodium hydroxide to sodium carbonate on the surface of the cathode material is difficult, which proves that the cathode material according to the present invention has excellent surface structure stability.

[0128] Measurement Example 2 The sodium oxide-containing cathode materials produced in the examples and comparative examples were placed in a muffle furnace, heated from room temperature to 900 °C, held for 10 h, and the heating rate was 5 °C / min. During sintering, air with a humidity of 30% RH was continuously introduced at an introduction rate of 15 m 3 / h. After natural cooling, it was crushed and sieved to obtain the treated sodium oxide-containing cathode material, and the content of soluble residual bases on its surface was measured. The results are shown in Table 5.

[0129]

Table 5

[0130] As can be seen from Table 5, as a result of heat treatment of the sodium oxide-containing cathode materials S1 to S17 according to the present invention under conditions of high humidity (air with a humidity of 30% RH) and high temperature (900 °C), the absolute content change Δλ [m(Na2CO3) + m(NaOH)] and the ratio content change Δλ [m(Na2CO3) / m(NaOH)] of soluble bases on the surface are significantly smaller than those of Comparative Example D1 and Ratio D2. From this, it can be seen that the sodium oxide-containing cathode material according to the present invention has a stable surface structure, is difficult to react with air, and even under conditions of high humidity (air with a humidity of 30% RH) and high temperature (900 °C), it is difficult for sodium hydroxide on the surface of the cathode material to be converted into sodium carbonate. This proves that the cathode material according to the present invention has excellent surface structure stability. By comparing m(Na2CO3)1 / m(NaOH)1 in Table 4 and Table 5, it can be seen that for the sodium oxide-containing cathode materials S1 to S17 according to the present invention, when the heat treatment temperature rises from 600 °C to 900 °C, the decrease in the value of m(Na2CO3)1 / m(NaOH)1 is very small. From this, it is proved that even at a very high treatment temperature (900 °C), there is only a very small amount of Na2CO3 involved in the reaction to incorporate Na into the material lattice. On the other hand, for D1 and D2, when the heat treatment temperature rises from 600 °C to 900 °C, the decrease in the value of m(Na2CO3)1 / m(NaOH)1 is large, which proves that there is a large amount of Na2CO3 involved in the reaction to incorporate Na into the material lattice at high temperature. From the above, it can be seen that the cathode material according to the present invention has a stable internal structure, and even at high temperature, it is difficult for the base remaining on the surface to react and enter the bulk of the material.

[0131] Application Example Manufacture of the electrode plate: The sodium metal oxide-containing cathode materials, carbon black, and polyvinylidene fluoride produced in the examples and comparative examples were thoroughly mixed in a mass ratio of 90%:5%:5% with an appropriate amount of N-methylpyrrolidone to form a uniform slurry, which was then coated on an aluminum foil and baked at 120 °C. After roll pressing, punching was performed, and the electrode plate with a diameter of 11 mm was punched out under a pressure of 100 MPa. Next, the electrode plate was placed in a vacuum oven and baked at 120 °C for 12 h. The characteristics of the electrode plate are shown in Table 6. Battery Assembly: Inside a glove box filled with argon gas, a sodium sheet was used as the negative electrode, a polypropylene microporous membrane as the separator (Celgard 2400), 1 mol / L of NaPF6 as the electrolyte, and assembled into a 2025-type button battery. The electrochemical characteristics of the manufactured battery are shown in Table 7.

[0132]

Table 6

[0133] As can be seen from Table 6, compared with Comparative Example 1 and Comparative Example 2, the positive electrode plates manufactured with the positive electrode materials provided in Examples S1 to S17 have a higher plate density. By using the above positive electrode plates in a sodium-ion battery, the energy density of the battery can be significantly improved.

[0134]

Table 7

[0135] As can be seen from Table 7, compared with Comparative Example 1 and Comparative Example 2, the sodium-ion batteries assembled using the positive electrode plates manufactured with the positive electrode materials according to Examples S1 to S17 have a higher discharge specific capacity, better rate performance, and cycle stability. In Comparative Example 1, the capacity decreased compared with Example 1 because the content of soluble base on the surface was too high. In Comparative Example 2, compared with Example 8, the lack of introduction of dry gas and the shortening of the sintering time resulted in too high a content of soluble base on the surface of the material prepared in Comparative Example 2 and inappropriate crystallinity, deteriorating its electrochemical characteristics.

[0136] Figures 8, 9, 10 and 11 are the first charge-discharge curves of sodium-ion batteries assembled using the positive electrode plates made of the sodium oxide-containing positive electrode materials manufactured in Example 2, Example 10, Example 12 and Comparative Example 2 respectively. As can be seen from Figures 8 to 11, the initial discharge capacities of the sodium oxide-containing positive electrode materials according to Example 2, Example 10 and Example 12 are 137.2 mAh / g, 158.7 mAh / g and 163.7 mAh / g respectively, all of which are significantly higher than the initial discharge capacity (116.1 mAh / g) of the sodium oxide-containing positive electrode material manufactured in the comparative example. From this, it is proved that the sodium oxide-containing positive electrode material according to the present invention has a higher discharge specific capacity.

[0137] Figures 12, 13, 14, 15 and 16 are diagrams showing the cycle characteristics of sodium-ion batteries assembled using the positive electrode plates made of the sodium oxide-containing positive electrode materials manufactured in Example 1, Example 9, Example 12, Example 16 and Comparative Example 2 respectively. As can be seen from Figures 12 to 16, the capacity retention rates of the sodium oxide-containing positive electrode materials according to Example 1, Example 9, Example 12 and Example 16 after 80 cycles at 1C are 88.6%, 94.5% and 96% respectively, all of which are significantly higher than the capacity retention rate (51.8%) under the same measurement conditions of the sodium oxide-containing positive electrode material of Comparative Example 2. From this, it is proved that the sodium oxide-containing positive electrode material according to the present invention has a good cycle life.

[0138] As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, multiple simple modifications can be made to the technical solution of the present invention, including combining each technical feature in other appropriate ways. These simple modifications and combinations should be regarded as the content disclosed in the present invention and all belong to the patent scope of the present invention.

Claims

1. A sodium oxide-containing positive electrode material, wherein the content of soluble base on the surface is (1) m(Na ２ CO ３ ) + m(NaOH) ≤ 15000 ppm, (2) 0.1 ≤ m(Na ２ CO ３ ) / m(NaOH) ≤ 1 is satisfied, m(Na ２ CO ３ ) is the content of Na ２ CO ３ on the surface of the positive electrode material, and m(NaOH) is the content of NaOH on the surface of the positive electrode material, has a composition represented by the general formula of Formula I, the sodium oxide-containing positive electrode material contains element M' in the form of a coating agent, and is characterized by the sodium oxide-containing positive electrode material. Na １－ｘ [Mn ｙ Fe ｚ M ｕ M' ｊ O ２－ｗ F ｗ Formula I (Here, 0.05 ≦ x ≦ 0.3, 0.3 ≦ y ≦ 0.6, 0.15 ≦ z ≦ 0.35, 0 < u ≦ 0.3, 0 < j ≦ 0.05, 0 ≦ w ≦ 0.05, M is at least one element selected from Li, Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, and Sr, and M' is at least one element selected from Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, and Sr.)

2. wherein the content of soluble base on the surface is (1) m(Na ２ CO ３ ) + m(NaOH) ≤ 12000 ppm, (2) The sodium oxide-containing positive electrode material according to claim 1, which satisfies the condition of 0.1 ≦ m(Na ２ CO ３ ) / m(NaOH) ≦ 0.

6.

3. wherein the content of soluble base on the surface of the positive electrode material heat-treated under the conditions of 500 to 900 °C is △λ[m(Na ２ CO ３ ) + m(NaOH)] ≤ 10%, △λ [m(Na ２ CO ３ ) / m(NaOH)] ≤ 50% under the condition that 【Number 1】 and [m(Na ２ CO ３ )+m(NaOH)] ０ is the total content of soluble base on the surface of the positive electrode material before treatment, and [m(Na ２ CO ３ )+m(NaOH)] １ is the total content of soluble base on the surface of the positive electrode material after treatment, m(NaOH) ０ is the content of NaOH on the surface of the positive electrode material before treatment, m(NaOH) １ is the content of NaOH on the surface of the positive electrode material after treatment, m(Na ２ CO ３ ) ０ is the content of Na ２ CO ３ on the surface of the positive electrode material before treatment, m(Na ２ CO ３ ) １ is the content of Na ２ CO ３ on the surface of the positive electrode material after treatment, the sodium oxide-containing positive electrode material according to claim 1.

4. The full width at half maximum (FWHM) of the (003) crystal plane obtained by XRD （００３） and the full width at half maximum (FWHM) of the (104) crystal plane （１０４） are 0.1 ≤ FWHM （００３） ≤ 0.3, 0.1 ≤ FWHM （１０４） ≤ 0.4, 0.5 ≤ FWHM （００３） / FWHM （１０４） The sodium oxide-containing positive electrode material according to claim 1, which satisfies the condition of ≤ 1.

2.

5. Peak area S of the (003) crystal plane obtained by XRD （００３） and peak area S of the (104) crystal plane （１０４） are 0.5 ≤ S （００３） / S （１０４） The sodium oxide-containing positive electrode material according to claim 1, which satisfies the condition of 0.5 ≤ S / S ≤ 1.

5.

6. The tap density is 1.2 g / cm ３ or more, The compression density is 2.5 g / cm ３ or more, The BET specific surface area satisfies the condition of 0.5 m ２ / g ≤ BET ≤ 4 m ２ / g, and the sodium oxide-containing positive electrode material according to claim 1.

7. A method for manufacturing a sodium oxide-containing positive electrode material, comprising the steps of subjecting a sodium-manganese-iron-containing positive electrode material precursor to a first sintering, cooling, crushing, and sieving to obtain the sodium oxide-containing positive electrode material, wherein an oxygen-containing atmosphere is introduced in the first sintering, The introduction amount of the oxygen-containing atmosphere is 1 to 15 m ３ / h, and the humidity of the oxygen-containing atmosphere is 10 RH% or less, the temperature T1 of the first sintering satisfies the condition of 500×(1 + y) ≦ T1 ≦ 400×(3 - y) °C, and y is the content of Mn in the sodium-manganese-iron oxide-containing positive electrode material, the heat preservation time of the first sintering is 6 to 20 h, the heating rate of the first sintering is 10 °C / min or less, The sodium-manganese-iron oxide-containing cathode material precursor is [Mn ｙ Fe ｚ M ｕ (OH) ２ , a mixture of an Na source, and additive M, [Mn ｙ Fe ｚ M ｕ CO ３ , a mixture of an Na source and additive M, or a mixture selected from an oxide and / or hydroxide of Mn, an oxide and / or hydroxide of Fe, and an Na source and additive M, where the molar ratio is n(Mn):n(Fe) = y:z in the sodium-manganese-iron oxide-containing positive electrode material precursor, the usage amount of the Na source satisfies 0.6 ≦ n(Na) / n(Mn + Fe + M) ≦ 1, in the sodium-manganese-iron oxide-containing positive electrode material precursor, the usage amount of the additive M satisfies 0 < n(M) / n(Mn + Fe + M) ≦ 0.5, 0.2 ≦ y ≦ 0.6, 0.1 ≦ z ≦ 0.4, 0 < u ≦ 0.5, and M is at least one element selected from Mg, Al, Cu, Zn, Zr, Nb, Co, Ti, Y, Sc, Cr, W, La, Mo, Os, Pr, Re, Ru, Sr, Sm, and Ta, and is characterized by the method for manufacturing a sodium oxide-containing positive electrode material.

8. The introduction amount of the oxygen-containing atmosphere is 2 to 8 m ３ / h, and the humidity of the oxygen-containing atmosphere is 6 RH% or less, the oxygen-containing atmosphere includes air and / or oxygen gas, The temperature T1 of the first sintering satisfies the condition of 550×(1 + y) ≤ T1 ≤ 380×(3 - y) °C, the heat preservation time of the first sintering is 8 to 15 h, the heating rate of the first sintering is 8 °C / min or less. The manufacturing method according to claim 7.

9. The sodium-manganese-iron-containing cathode material precursor is manufactured by a method of uniformly mixing oxides and / or hydroxides of Mn and oxides and / or hydroxides of Fe with a molar ratio of n(Mn):n(Fe) = y:z, a Na source, and an additive M to obtain the sodium-manganese-iron-oxide-containing cathode material precursor, or the sodium-manganese-iron-containing cathode material precursor is (1) Prepare a mixed salt solution of Mn salt, Fe salt, and additive M with a molar ratio of n(Mn):n(Fe) = y:z, prepare a precipitating agent, a complexing agent, and an arbitrary additive M into a precipitating agent solution, a complexing agent solution, and an additive M solution respectively, merge the mixed salt solution, the precipitating agent solution, and the complexing agent solution and introduce them into a reaction kettle to carry out a coprecipitation reaction to obtain a solid-liquid mixture, filter to obtain a filter cake, dry the filter cake, sieve it to obtain an intermediate, and (2) manufacture it by a method of mixing the intermediate, a sodium source, and an arbitrary additive M to obtain the sodium-manganese-iron-containing cathode material precursor, the additive M is added at least in step (1) or step (2), the sodium source is at least one selected from sodium hydroxide, sodium carbonate, sodium sulfate, sodium oxalate, sodium chloride, sodium citrate, and sodium fluoride, the additive M is at least one selected from oxides, hydroxides, oxyhydroxides, phosphates, fluorides, borides, carbonates, and oxalates containing element M, the usage amount of the additive M makes 0 < n(M) / n(Mn + Fe + M) ≤ 0.5 in the sodium-manganese-iron-containing cathode material precursor, the usage amount of the sodium source makes 0.6 ≤ n(Na) / n(Mn + Fe + M) ≤ 1 in the sodium-manganese-iron-containing cathode material precursor. The manufacturing method according to claim 7.

10. further includes the steps of mixing the sodium-oxide-containing cathode material with a cleaning liquid, cleaning, filtering to obtain a filter cake, and drying the filter cake, the cleaning liquid is selected from water and / or an acidic solution, the weight ratio of the sodium-oxide-containing cathode material to the cleaning liquid is 0.5 to 3:

1. The concentration of the acidic solution is 0.1 to 5 mol / L, The washing conditions include washing at a temperature of 0 to 25°C for 3 to 60 minutes while stirring at 100 to 1000 rpm. The manufacturing method according to claim 7.

11. After ball-milling and mixing the sodium oxide-containing positive electrode material and the coating agent M', subjecting it to a second sintering, cooling, crushing, and sieving to obtain the sodium oxide-containing positive electrode material. The method further includes the step of In the second sintering, an oxygen-containing atmosphere is introduced. The introduction amount of the oxygen-containing atmosphere is 1 to 15 m ３ / h, and the humidity of the oxygen-containing atmosphere is 10 RH% or less. The temperature T2 of the second sintering satisfies the condition of 250×(1 + y) ≤ T2 ≤ 300×(3 - y)°C, where y is the content of Mn in the sodium manganese iron oxide-containing positive electrode material. The heat preservation time of the second sintering is 4 to 20 h. The heating rate of the second sintering is 10°C / min or less. The usage amount of the coating agent M' is such that 0 ≤ n(M') / n(Mn + Fe + M + M') ≤ 0.1 in the sodium oxide-containing positive electrode material. The manufacturing method according to claim 7.

12. A positive electrode plate, including at least 80 wt% of a sodium oxide-containing positive electrode material based on the total weight of the positive electrode plate. The sodium oxide-containing positive electrode material is the sodium oxide-containing positive electrode material according to any one of claims 1 to 6. The plate density of the positive electrode plate is 2.8 g / cm ３ or more. The positive electrode plate is characterized by this.

13. Use of the sodium oxide-containing positive electrode material according to any one of claims 1 to 6 in a sodium ion battery.

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