O3-type layered oxide sodium-ion positive electrode material and preparation method and application thereof

Abstract

The application provides a type O3 layered oxide sodium-ion positive electrode material and a preparation method and application thereof. The positive electrode material comprises a sodium nickel-iron-manganese-zinc core and a sodium nickel-iron-manganese-zinc shell; in the sodium nickel-iron-manganese-zinc core, zinc accounts for 7-10% of the total molar amount of nickel-iron-manganese-zinc; in the sodium nickel-iron-manganese-zinc shell, zinc accounts for 1-5% of the total molar amount of nickel-iron-manganese-zinc; the sodium nickel-iron-manganese-zinc core and the sodium nickel-iron-manganese-zinc shell each independently comprise a first lattice regulating element; and the sodium nickel-iron-manganese-zinc shell further comprises a second lattice regulating element. The type O3 layered oxide sodium-ion positive electrode material is designed as a core-shell structure, supports each other, couples each other, simultaneously regulates the composition of the core and the shell, inhibits the lattice interlayer slip, avoids the cracking problem caused by stress concentration, significantly improves the structural stability of the positive electrode material, and realizes the synchronous improvement of the rate performance and the cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to positive electrode materials, and in particular to O3-type layered oxide sodium ion positive electrode materials, and preparation methods and applications thereof. Background Art

[0002] In recent years, with the increasing shortage of natural lithium and the significant price fluctuations of raw materials such as nickel and cobalt, sodium-ion batteries (SIBs) have emerged as a viable alternative to lithium-ion batteries (LIBs) due to the abundance and low prices of sodium, copper, iron, and manganese in their cathode materials. Their advantages include low cost, high safety, and long cycle life. O3-type layered oxide sodium-ion cathode materials have high specific capacity and are fabricated using similar processes to ternary cathode materials for lithium-ion batteries. Therefore, they are considered the most promising cathode materials for sodium batteries. However, due to their inherent structure, O3-type layered oxide sodium-ion cathode materials are prone to structural changes / phase transitions during sodium ion insertion and extraction, resulting in volume expansion, anisotropic stress on the particle surface, and high residual alkali content, leading to decreased physical, chemical, and electrical properties.

[0003] CN119050299A discloses an O3 type layered oxide composite material, the molecular formula of which is Na x Ni 0.4 Fe 0.2 Mn 0.4-y Ti y O 2-z F z @ZrO2, in which ZrO2 is coated on the surface of O3-type layered oxide, which not only alleviates the problem of easy failure of O3-type material when exposed to air, but also inhibits the volume change of O3-type layered oxide during the cycle, thereby enhancing the cycle stability. A part of the anatase-type ZrO2 melts into the transition metal layer at high temperature, thereby enhancing the stability of the transition metal layer. A certain proportion of titanium is used to replace manganese, which can reduce costs on the one hand and effectively improve the sodium ion diffusion coefficient on the other hand. Doping F ions at the anion site and introducing fluoride ions to replace part of the oxygen element can enhance the bond energy between the transition metal and the fluorine element, alleviate the gas production problem, and improve the voltage and specific capacity of the material.

[0004] CN117416992A discloses an O3 type layered oxide containing sodium vacancies. The chemical formula of the O3 type layered oxide is: Na x Ni a Cu b Fe c Mn d Ti eO2, 0.7≤x<0.8, 0.1≤a≤0.3, 0.02≤b≤0.15, 0.02≤c≤0.2, 0.2≤d≤0.4, 0.1≤e≤0.3, a+b+c+d+e=1. This invention reduces the sodium content to create sodium vacancies in the O3-type material. While also rationally controlling the composition and content range of transition metal elements, the invention utilizes the stability of the sodium vacancy structure when charged to high voltages, thereby improving the material's cycle and rate performance when operating at high voltages.

[0005] CN118507677A discloses a coated sodium-ion battery positive electrode material. The coated sodium-ion battery positive electrode material comprises: a layered oxide serving as a substrate for the sodium-ion battery positive electrode material, wherein the layered oxide is a P2-type, O3-type, or dual-phase transition metal oxide; and a CuO coating layer coated on the surface of the layered oxide. The present invention also relates to a method for preparing the positive electrode material. By using a selected layered oxide and a preferred coating method, the invention achieves a sodium-ion battery positive electrode material with excellent charge-discharge capacity and cycling stability.

[0006] Therefore, it is of great significance to provide an O3-type layered oxide sodium ion positive electrode material with good structural stability. Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention aims to provide an O3-type layered oxide sodium ion cathode material, its preparation method, and its application. The present invention designs the O3-type layered oxide sodium ion cathode material into a structure consisting of a high-zinc core and a low-zinc shell. The core and shell support and couple with each other to form a stress buffer zone, thereby alleviating the cracking problem caused by the shell layer, which has a larger specific surface area and a high degree of reaction, leading to phase change. Furthermore, the first and second lattice control elements are introduced into the core and shell, respectively, to further maintain the structural stability of the material, regulate the interlayer spacing, reduce lattice distortion, and improve the material's cycling and rate performance.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides an O3-type layered oxide sodium ion positive electrode material, which includes a sodium nickel iron manganese zincate core and a sodium nickel iron manganese zincate shell; in the sodium nickel iron manganese zincate core, the total molar amount of nickel iron manganese zinc is 100%, and the molar percentage of zinc is 7%~10%; in the sodium nickel iron manganese zincate shell, the total molar amount of nickel iron manganese zinc is 100%, and the molar percentage of zinc is 1%~5%; the sodium nickel iron manganese zincate core and the sodium nickel iron manganese zincate shell each independently include a first lattice control element; the sodium nickel iron manganese zincate shell also includes a second lattice control element.

[0010] During the application of O3-type layered oxide sodium ion positive electrode materials, cracking is easily caused by phase change reactions due to the large surface area of ​​the outer layer of the particles and the high degree of reaction participation. The present invention designs the O3-type layered oxide sodium ion positive electrode material into a core-shell structure. In the sodium nickel iron manganese zincate core, the total molar amount of nickel iron manganese zinc is 100%, and the molar percentage of zinc is 7%~10%, for example, it can be 7%, 8%, 9% or 10%; in the sodium nickel iron manganese zincate shell, the total molar amount of nickel iron manganese zinc is 100%, and the molar percentage of zinc is 1%~5%, for example, it can be 1%, 2%, 3%, 4% or 5%. The structure of the high-zinc content core and the low-zinc content shell is matched to form a stress buffer zone, thereby improving the structural stability of the O3-type layered oxide sodium ion positive electrode material and slowing down cracking.

[0011] The present invention independently adds a first lattice control element to the inner core and outer shell of sodium nickel iron manganese zincate. The first lattice control element can form a high bond energy with oxygen, can inhibit interlayer slip, and reduce the migration and mixing of transition elements; and adds a second lattice control element to the outer shell of sodium nickel iron manganese zincate. The second lattice control element has a high oxidation state and can undergo electronic hybridization with other elements, thereby increasing the electron cloud density near the second lattice control element, expanding the Na ion transmission channel while stabilizing the lattice spacing, reducing expansion and contraction during the cycle, controlling the degree of lattice distortion, reducing structural collapse caused by stress concentration, and effectively improving cycle stability and rate performance.

[0012] Preferably, in the sodium nickel iron manganese zincate core, the doping amount of the first lattice regulating element is 0.1 mol% to 1 mol% of the sodium nickel iron manganese zincate core, for example, it can be 0.1 mol%, 0.2 mol%, 0.3 mol%, 0.4 mol%, 0.5 mol%, 0.6 mol%, 0.7 mol%, 0.8 mol%, 0.9 mol% or 1 mol%, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] Preferably, in the sodium nickel iron manganese zincate shell, the doping amounts of the first lattice regulating element and the second lattice regulating element are each independently 0.1 mol%, 0.2 mol%, 0.3 mol%, 0.4 mol%, 0.5 mol%, 0.6 mol%, 0.7 mol%, 0.8 mol%, 0.9 mol% or 1 mol% of the sodium nickel iron manganese zincate shell, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0014] In the present invention, the selection of doping elements affects the interlayer spacing and bond energy of the lattice of the O3-type layered oxide sodium ion positive electrode material. By regulating the type and content of the first lattice regulating element A in the inner core layer and the first lattice regulating element A and the second lattice regulating element B in the outer shell layer, the relationship between the interlayer spacing and the bond energy is regulated, which can further improve the structural stability of the material, provide a more reliable and stable channel for the transmission of Na ions, and thus improve the rate performance and cycle stability of the positive electrode material.

[0015] Preferably, the sodium nickel iron manganese zincate core and the sodium nickel iron manganese zincate shell further independently include a first lattice regulating element, wherein the first lattice regulating element includes any one or a combination of at least two of Ti, Y, Zr, La, Ce, Ca or Al, and typical but non-limiting combinations include a combination of Ti and Y, a combination of Zr and La, a combination of Ce and Ca, or a combination of Ca and Al.

[0016] Preferably, the sodium nickel iron manganese zincate shell further includes a second lattice regulating element, and the second lattice regulating element includes any one or a combination of at least two of Cu, Co, Nb, Sn, Sb, Cr, Mn, Mo, W, Re or Ru, and typical but non-limiting combinations include a combination of Cu and Co, a combination of Nb and Sn, a combination of Sb and Cr, a combination of Mn and Mo, a combination of W and Re, or a combination of Re and Ru.

[0017] In the sodium nickel iron manganese zincate shell provided by the present invention, the alkali metal layer spacing is defined as d O-Na , the distance between transition metal layers is d TM-TM The weighted average ionic radius of the first lattice regulating element and the second lattice regulating element is r AB And the average radius of sodium ions is r Na , wherein the weighted average ionic radius of the first lattice regulating element and the second lattice regulating element is r AB =(n A· r A +n B· r B ) / (n A +n B ), n A is the amount of the first lattice control element in the outer shell of sodium nickel iron manganese zincate, n B is the amount of the second lattice control element in the outer shell of sodium nickel iron manganese zincate, r A is the average ionic radius of the first lattice regulating element, r B is the average ionic radius of the second lattice regulating element.

[0018] d O-Na· r Na with d TM-TM· rAB The ratio of is directly related to the geometric matching of the layered structure and the regulation of the ion transport path. AB Increase, lattice distortion makes the intermolecular force increase, the interlayer force of transition metal is enhanced, and the interlayer spacing d of transition metal is increased. TM-TM The structure is more stable, and at the same time, the distance between the alkali metal layers is increased, which reduces the transmission barrier of Na ions and improves the diffusion efficiency of Na ions.

[0019] Preferably, in the sodium nickel iron manganese zincate shell, the alkali metal layer spacing d O-Na , transition metal interlayer spacing d TM-TM , the weighted average ionic radius r of the first lattice regulating element and the second lattice regulating element AB and the average radius r of the sodium ion Na Satisfy between:

[0020] (d O-Na· r Na ) / (d TM-TM· r AB )=δ1, 1.9<δ1<2.5, for example, δ1 can be 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.5; wherein, d O-Na d TM-TM 、r AB With r Na The unit is Å.

[0021] In the positive electrode material provided by the present invention, the bond energy between the first lattice regulating element and oxygen in the outer shell of the sodium nickel iron manganese zincate, the bond energy between the second lattice regulating element and oxygen, and the average bond energy between the first lattice regulating element and oxygen in the inner core of the sodium nickel iron manganese zincate are defined as E bond The average unit cell volume of the sodium nickel iron manganese zincate core and the sodium nickel iron manganese zincate shell is the same as that of the standard NaNi 0.35 Zn 0.05 Fe 0.28 Mn 0.32 The difference in the volume of the O2 unit cell is ΔV, ln(E bond ) and ΔV ½ The ratio of ΔV affects the balance between the stability of the lattice structure and the dynamics of the material. High bond energy can resist the lattice stress caused by ion extraction / embedding, while a small ΔV means low lattice intrinsic distortion. bond ) is larger, ΔV½ is smaller, i.e. ln(E bond ) and ΔV ½ The larger the ratio, the stronger the material's lattice rigidity and higher its structural stability. Simultaneously, the bond energy and unit cell volume are regulated, and the two work together to reduce the risk of transition from layered to spinel and then to rock salt phases, ensuring the structural stability of the material during the recycling process.

[0022] Preferably, in the positive electrode material, the average bond energy E of the first lattice regulating element and the second lattice regulating element with oxygen is bond , and the unit cell volume of the cathode material is similar to that of the standard NaNi 0.35 Zn 0.05 Fe 0.28 Mn 0.32 The difference in the volume of the O2 unit cell ΔV satisfies:

[0023] ln(E bond ) / (ΔV ½ )=δ2, 3.0<δ2<3.6, for example, δ2 can be 3.0, 3.1, 3.2, 3.3, 3.4, 3.5 or 3.6; wherein, E bond The unit of is kJ / mol, and the unit of ΔV is Å 3 .

[0024] In the present invention, standard NaNi 0.35 Zn 0.05 Fe 0.28 Mn 0.32 The volume of the O2 unit cell is 124Å 3 calculate.

[0025] Preferably, in the positive electrode material, the mass percentage of the nickel iron manganese zincate sodium core is 15% to 40%, for example, 15%, 20%, 25%, 30%, 35% or 40%, and the mass percentage of the nickel iron manganese zincate sodium shell is 60% to 85%, for example, 60%, 65%, 70%, 75%, 80% or 85%, including but not limited to the values ​​listed, and other unlisted values ​​within the numerical range are equally applicable. The core and shell of suitable mass ratio are matched to form a continuous crystal structure using lattice matching at the interface. This matching can reduce the lattice stress concentration caused by volume change during sodium ion deintercalation and deintercalation, while reducing the transition of the layered structure to spinel or rock salt phase. The shell material with a higher mass ratio can constrain the structure of the core material through the covalent bond and coordination of the lattice, delaying the phase transition, and the core can provide mechanical support as a "skeleton" to avoid the shell from failing due to its own structural collapse during the cycle. The high structural strength of the core and the high stability of the shell work together to effectively improve the performance of the positive electrode material.

[0026] Preferably, the chemical formula of the sodium nickel iron manganese zincate core is Na x Ni 1-u-v-w Zn u Fe v Mn wO2, wherein 0.95≤x≤1.05, for example, x can be 0.95, 0.97, 0.99, 1.01, 1.03 or 1.05; 0.07≤u≤0.1, for example, u can be 0.07, 0.08, 0.09 or 0.1; 0.15≤v≤0.35, for example, v can be 0.15, 0.2, 0.25, 0.3 or 0.35; 0.15≤w≤0.35, for example, w can be 0.15, 0.2, 0.25, 0.3 or 0.35, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the chemical formula of the sodium nickel iron manganese zincate shell is Na m Ni 1-a-b-c Zn a Fe b Mn c O2, wherein 0.95≤m≤1.05, for example, m can be 0.95, 0.97, 0.99, 1.01, 1.03 or 1.05; 0.01≤a≤0.05, for example, a can be 0.01, 0.02, 0.03, 0.04 or 0.05; 0.2≤b≤0.4, for example, b can be 0.2, 0.25, 0.3, 0.35 or 0.4; 0.2≤c≤0.4, for example, c can be 0.2, 0.25, 0.3, 0.35 or 0.4, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In a second aspect, the present invention provides a method for preparing the O3-type layered oxide sodium ion positive electrode material as described in the first aspect, the preparation method comprising:

[0029] The sodium nickel iron manganese zincate core precursor, the first lattice control compound and the sodium salt are first mixed to obtain a first mixture, and then first sintered to obtain the sodium nickel iron manganese zincate core.

[0030] The sodium nickel iron manganese zincate core, the first lattice control compound, the second lattice control compound, the sodium nickel iron manganese zincate shell precursor and the sodium salt are mixed for a second time to obtain a second mixture, and then sintered for a second time to obtain the O3-type layered oxide sodium ion positive electrode material.

[0031] The preparation method provided by the present invention first prepares a sodium nickel iron manganese zincate core, and then mixes the core with the sodium nickel iron manganese zincate shell material and sintering. Compared with first co-precipitating to prepare a precursor with corresponding compositions of the core and shell, and then sintering, the preparation method provided by the present invention effectively prevents the mutual diffusion between the elements of the core and shell layers, realizes the precise control of the composition of the core and shell, and ensures the uniformity and consistency of the composition of the core and shell.

[0032] Preferably, the first lattice regulating compound includes any one or a combination of at least two of TiO2, Y2O3, ZrO2, La2O3, CeO2, CaO or Al2O3. Typical but non-limiting combinations include a combination of TiO2 and Y2O3, a combination of ZrO2 and La2O3, a combination of Ce2O2 and CaO, or a combination of CaO and Al2O3.

[0033] Preferably, the second lattice regulating compound includes any one or a combination of at least two of CuO, Co2O3, Nb2O5, SnO2, Sb2O5, Cr2O3, MnO2, MoO3, WO3, ReO3 or RuO2. Typical but non-limiting combinations include a combination of CuO and Co2O3, a combination of Nb2O5 and SnO2, a combination of Sb2O5 and Cr2O3, a combination of MnO2 and MoO3, a combination of WO3 and ReO3, or a combination of ReO3 and RuO2.

[0034] Preferably, the temperature of the first sintering is 800°C to 1000°C, for example, 800°C, 850°C, 900°C, 950°C or 1000°C, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the first sintering time is 6 h to 20 h, for example, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the temperature of the second sintering is 900°C to 1050°C, for example, 900°C, 950°C, 1000°C or 1050°C, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the second sintering time is 6 h to 20 h, for example, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the atmosphere of the first sintering and the second sintering is independently an oxygen-containing atmosphere. Exemplarily, the oxygen-containing atmosphere includes air.

[0039] In a third aspect, the present invention provides a positive electrode sheet, which includes the O3-type layered oxide sodium ion positive electrode material as described in the first aspect.

[0040] In a fourth aspect, the present invention provides a sodium ion battery, which comprises the O3-type layered oxide sodium ion positive electrode material as described in the first aspect, or comprises the positive electrode sheet as described in the third aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The present invention designs the O3 type layered oxide sodium ion cathode material into a core and shell structure with differential distribution of Zn elements, and utilizes the coupling effect between the core and the shell to effectively form a stress buffer zone, thereby improving the structural stability of the O3 type layered oxide sodium ion cathode material and slowing down the cracking caused by stress concentration.

[0043] (2) The present invention independently adds a first lattice regulating element to the core and shell of sodium nickel iron manganese zincate, which can inhibit interlayer slip and reduce the migration and mixing of transition elements; adding a second lattice regulating element to the shell of sodium nickel iron manganese zincate can improve the Na ion transmission channel while stabilizing the lattice spacing, reduce expansion and contraction during the cycle, control the degree of lattice distortion, reduce structural collapse caused by stress concentration, and effectively improve the cycle stability and rate performance.

[0044] (2) The preparation method provided by the present invention effectively prevents the mutual diffusion of elements between the core and the shell layer, realizes the precise control of the composition of the core and the shell, and ensures the uniformity and consistency of the composition of the core and the shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the FE-SEM morphology of the O3-type layered oxide sodium ion positive electrode material provided in Example 1.

[0046] Figure 2 This is the 0.1C charge-discharge curve of the O3-type layered oxide sodium ion positive electrode material provided in Example 1.

[0047] Figure 3 This is the 25°C cycle curve of the O3-type layered oxide sodium ion positive electrode material provided in Example 1.

[0048] Figure 4 This is a graph of the rate discharge capacity retention rate of the O3-type layered oxide sodium ion positive electrode material provided in Example 1. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0051] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0052] In a specific embodiment, the present invention provides an O3-type layered oxide sodium ion positive electrode material, wherein the positive electrode material comprises a sodium nickel iron manganese zincate core and a sodium nickel iron manganese zincate shell.

[0053] The mass percentage of the sodium nickel iron manganese zincate core is 15% to 40%, and the chemical formula of the sodium nickel iron manganese zincate core is Na x Ni 1-u-v-w Zn u Fe v Mn w A y O2, wherein 0.95≤x≤1.05, 0.07≤u≤0.1, 0.15≤v≤0.35, 0.15≤w≤0.35, 0.001≤y≤0.01, A includes any one or a combination of at least two of Ti, Y, Zr, La, Ce, Ca or Al; the mass percentage of the sodium nickel iron manganese zincate shell is 60% to 85%, and the chemical formula of the sodium nickel iron manganese zincate shell is Na m Ni 1-a-b-c Zn a Fe b Mn c A d B e O2, wherein 0.95≤m≤1.05, 0.01≤a≤0.05, 0.2≤b≤0.4, 0.2≤c≤0.4, 0.001≤d≤0.01, 0.001≤e≤0.01, A includes any one or a combination of at least two of Ti, Y, Zr, La, Ce, Ca or Al, and B includes any one or a combination of at least two of Cu, Co, Nb, Sn, Sb, Cr, Mn, Mo, W, Re or Ru.

[0054] In some embodiments, the alkali metal layer spacing d in the sodium nickel iron manganese zincate shell is O-Na , transition metal interlayer spacing d TM-TM, the weighted average ionic radius r of the first lattice regulating element and the second lattice regulating element AB and the average radius r of the sodium ion Na Satisfy between:

[0055] (d O-Na· r Na ) / (d TM-TM· r AB )=δ1, 1.9<δ1<2.5. Among them, d O-Na d TM-TM 、r AB With r Na The unit is Å.

[0056] In some embodiments, in the positive electrode material, the average value of the bond energy between the first lattice regulating element and oxygen and the bond energy between the second lattice regulating element and oxygen is recorded as E bond The average unit cell volume of the cathode material is similar to that of the standard NaNi 0.35 Zn 0.05 Fe 0.28 Mn 0.32 The difference in the volume of the O2 unit cell is recorded as ΔV, and the E bond and ΔV satisfy:

[0057] ln(E bond ) / ΔV ½ =δ2, 3.0<δ2<3.6. Among them, E bond The unit of is kJ / mol, and the unit of ΔV is Å 3 .

[0058] In another specific embodiment, the present invention provides a method for preparing the O3-type layered oxide sodium ion positive electrode material as described in the above specific embodiment, the preparation method comprising:

[0059] In an oxygen-containing atmosphere, a sodium nickel iron manganese zincate core precursor, a first lattice regulation compound and a sodium salt are first mixed according to a molar ratio to obtain a first mixture; a first sintering is performed at 800°C to 1000°C for 6h to 20h to obtain the sodium nickel iron manganese zincate core; a second mixing is performed on the sodium nickel iron manganese zincate core, the first lattice regulation compound, the second lattice regulation compound, a sodium nickel iron manganese zincate shell precursor and a sodium salt according to a molar ratio and a mass ratio to obtain a second mixture; a second sintering is performed at 900°C to 1050°C for 6h to 20h to obtain the O3-type layered oxide sodium ion positive electrode material.

[0060] In some embodiments, the first lattice control compound includes any one or a combination of at least two of TiO2, Y2O3, ZrO2, La2O3, CeO2, CaO or Al2O3.

[0061] In some embodiments, the second lattice control compound includes any one or a combination of at least two of CuO, Co2O3, Nb2O5, SnO2, Sb2O5, Cr2O3, MnO2, MoO3, WO3, ReO3 or RuO2.

[0062] In yet another specific embodiment, the present invention provides a positive electrode comprising the O3-type layered oxide sodium ion positive electrode material as described in the foregoing specific embodiment.

[0063] In another specific embodiment, the present invention provides a sodium ion battery, which includes the O3-type layered oxide sodium ion positive electrode material as described in the above specific embodiment, or includes the positive electrode as described in the above still another specific embodiment.

[0064] Example 1

[0065] This embodiment provides an O3 type layered oxide sodium ion positive electrode material, including 35% by mass of NaNi 0.42 Zn 0.08 Fe 0.25 Mn 0.25 Ti 0.006 O2 core, and 65% by mass of NaNi 0.32 Zn 0.03 Fe 0.3 Mn 0.35 Ti 0.00 3Cu 0.009 O2 shell. The positive electrode material meets the following requirements: (d O-Na· r Na ) / (d TM-TM· r AB )=δ1=2.3, ln(E bond ) / (ΔV ½ )=δ2=3.4.

[0066] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, the preparation method comprising:

[0067] A sodium nickel iron manganese zincate core precursor, TiO2, and sodium carbonate are first mixed according to a molar ratio to obtain a first mixture, and the first mixture is first sintered at a temperature of 900° C. for 12 hours to obtain the sodium nickel iron manganese zincate core;

[0068] According to the molar ratio, the sodium nickel iron manganese zincate shell precursor, TiO2, CuO and sodium carbonate are mixed, and the sodium nickel iron manganese zincate core is added according to the mass ratio to perform a second mixing; the second mixture is subjected to a second sintering at a sintering temperature of 1000°C and a sintering time of 15 hours to prepare the O3-type layered oxide sodium ion positive electrode material.

[0069] The FE-SEM morphology of the O3-type layered oxide sodium ion cathode material prepared in this example is shown in FIG. Figure 1 shown.

[0070] Example 2

[0071] This embodiment provides an O3 type layered oxide sodium ion positive electrode material, including 15% by mass of Na 0.95 Ni 0.63 Zn 0.07 Fe 0.15 Mn 0.15 Y 0.003 O2 core, and 85% by mass of Na 0.95 Ni 0.59 Zn 0.01 Fe 0.2 Mn 0. 2Y 0.002 Co 0.006 O2 shell, the positive electrode material meets the following requirements: (d O-Na· r Na ) / (d TM-TM· r AB )=δ1=2.0,ln(E bond ) / (ΔV ½ )=δ2=3.0.

[0072] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, the preparation method comprising:

[0073] A sodium nickel iron manganese zincate core precursor, Y2O3 and sodium carbonate are first mixed according to a molar ratio to obtain a first mixture, and the first mixture is first sintered at a temperature of 800° C. for 6 hours to obtain the sodium nickel iron manganese zincate core;

[0074] According to the molar ratio, the sodium nickel iron manganese zincate shell precursor, Y2O3, Co2O3 and sodium carbonate are mixed, and the sodium nickel iron manganese zincate core is added according to the mass ratio to perform a second mixing; the second mixture is subjected to a second sintering at a sintering temperature of 900°C and a sintering time of 6 hours to prepare the O3-type layered oxide sodium ion positive electrode material.

[0075] Example 3

[0076] This embodiment provides an O3 type layered oxide sodium ion positive electrode material, including 40% by mass of Na 1.05 Ni 0.2 Zn 0.1 Fe 0.35 Mn 0.35 Al 0.005 O2 core, and 60% by mass of Na 1.05 Ni 0.15 Zn 0.05 Fe 0.4 Mn 0.4 Al 0.004 Sb 0.005 O2 shell, the positive electrode material meets the following requirements: (d O-Na· r Na ) / (d TM-TM· r AB )=δ1=2.5,ln(E bond ) / (ΔV ½ )=δ2=3.6.

[0077] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, the preparation method comprising:

[0078] A sodium nickel iron manganese zincate core precursor, Al2O3 and sodium carbonate are first mixed according to a molar ratio to obtain a first mixture, and the first mixture is first sintered at a temperature of 1000° C. for 20 hours to obtain the sodium nickel iron manganese zincate core;

[0079] According to the molar ratio, the sodium nickel iron manganese zincate shell precursor, Al2O3, Sb2O5 and sodium carbonate are mixed, and the sodium nickel iron manganese zincate core is added according to the mass ratio to perform a second mixing; the second mixture is subjected to a second sintering at a sintering temperature of 1050°C and a sintering time of 20 hours to prepare the O3-type layered oxide sodium ion positive electrode material.

[0080] Example 4

[0081] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, except that neither the core nor the shell contains the first lattice regulating element. In the positive electrode material, except that δ1=2.0 and δ2=3.0, the rest are the same as in Example 1.

[0082] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, which is the same as that of Example 1 except that no compound of element A is added during the preparation of the core and the shell.

[0083] Example 5

[0084] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, which is the same as Example 1 except that the outer shell does not contain the second lattice regulating element. In the positive electrode material, δ1=2.6 and δ2=3.1.

[0085] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, which is the same as that of Example 1 except that no compound of element B is added during the preparation of the shell.

[0086] Example 6

[0087] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, which is the same as that in Example 1 except that the doping amount of A in the core is 0.05 mol %, and in the unit cell of the positive electrode material, δ1=2.5 and δ2=3.0.

[0088] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the core according to the doping amount of A being 0.05 mol%, the rest is the same as that of Example 1.

[0089] Example 7

[0090] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, which is the same as that in Example 1 except that the doping amount of A in the core is 1.2 mol %, and in the unit cell of the positive electrode material, δ1=2.5 and δ2=3.6.

[0091] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the core according to the doping amount of A being 1.2 mol %, the rest is the same as in Example 1.

[0092] Example 8

[0093] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, which is the same as that in Example 1 except that the doping amount of B in the shell is 0.05 mol %, and in the unit cell of the positive electrode material, δ1=2.3 and δ2=2.9.

[0094] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the outer shell according to the B doping amount of 0.05 mol%, the rest is the same as that of Example 1.

[0095] Example 9

[0096] This embodiment provides an O3-type layered oxide sodium ion positive electrode material, which is the same as that in Example 1 except that the doping amount of B in the shell is 1.2 mol %, and in the unit cell of the positive electrode material, δ1=2.1 and δ2=2.8.

[0097] This embodiment also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the outer shell according to the B doping amount of 1.2 mol%, the rest is the same as that of Example 1.

[0098] Comparative Example 1

[0099] This comparative example provides an O3 type layered oxide sodium ion positive electrode material, the chemical formula of which is NaNi except for the shell. 0.42 Zn 0.08 Fe 0.25 Mn 0.25 Ti 0.003 Cu 0.009 Except for O2, the rest are the same as in Example 1.

[0100] This comparative example also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the shell according to the molar ratio of this comparative example, the rest is the same as Example 1.

[0101] Comparative Example 2

[0102] This comparative example provides an O3 type layered oxide sodium ion positive electrode material, the chemical formula of which is NaNi except for the core 0.32 Zn 0.03 Fe 0.3 Mn 0.35 Ti 0.006 Except for O2, the rest are the same as in Example 1.

[0103] This comparative example also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material. Except for preparing the core according to the molar ratio of this comparative example, the rest is the same as Example 1.

[0104] Comparative Example 3

[0105] This comparative example provides an O3-type layered oxide sodium ion positive electrode material, which is the same as Example 1 except that the core and the shell do not contain lattice regulating elements.

[0106] This comparative example also provides a method for preparing an O3-type layered oxide sodium ion positive electrode material, which is the same as Example 1 except that the first lattice regulation compound is not added when preparing the inner core, and the first lattice regulation compound and the second lattice regulation compound are not added when preparing the outer shell.

[0107] Performance testing:

[0108] The O3-type layered oxide sodium ion positive electrode material provided in all the above examples and comparative examples was mixed with SP and PVDF in a mass ratio of 94:3:3. After mixing evenly, N-methylpyrrolidone was added and stirred at 1800 rpm for 10 min using a homogenizer. After the mixed slurry was formed, it was coated on aluminum foil with a 200 μm scraper and then vacuum-baked at 80°C. The dried electrode was rolled and finally cut into a positive electrode sheet with a diameter of 14 mm, wherein the electrode sheet surface density was 9.7 mg / cm 2 , pole piece compaction 3.1g / cm 3 , then a pure sodium sheet with a diameter of 15.6 mm was used as the negative electrode sheet, ENA 18 electrolyte (Guangzhou Tianci High-tech Materials Co., Ltd.) was used, and a Whatman glass fiber diaphragm was used to assemble the sodium-ion battery in an argon-filled glove box.

[0109] At 25°C and a voltage range of 2V to 4V, the 0.1C discharge specific capacity, the 50-cycle capacity retention rate under the 0.1C charge / 1C discharge system, and the 4C rate discharge capacity retention rate under the 0.1C charge / 4C discharge system of the O3-type layered oxide sodium ion positive electrode material provided in all the above embodiments and comparative examples were tested. The test results are shown in Table 1. The 0.1C charge and discharge curves of the O3-type layered oxide sodium ion positive electrode material provided in Example 1 are shown in Table 1. Figure 2 , the cycle curve is shown in Figure 3 .

[0110] At 25 ° C, in the voltage range of 2V~4V, the O3-type layered oxide sodium ion positive electrode material provided in Example 1 was subjected to a step rate charge test. The test system was: 0.1C charge / 0.1C discharge, 0.1C charge / 0.5C discharge, 0.1C charge / 1C discharge, 0.1C charge / 2C discharge, 0.1C charge / 3C discharge and 0.1C charge / 4C discharge were performed in sequence to test the discharge capacity retention rate at different rates. The test results are shown in FIG. Figure 4 .

[0111] The O3-type layered oxide sodium ion cathode materials provided in all the above examples and comparative examples were tested at 45°C and a voltage range of 2V to 4V. The capacity retention after 50 cycles under a 0.1C charge / 1C discharge regime was determined. The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114] According to the test results in Table 1, the present invention forms a stress buffer zone by designing the O3-type layered oxide sodium ion positive electrode material into a structure in which a core with a high zinc content and a shell with a low zinc content cooperate with each other. This avoids the cracking problem caused by stress concentration after repeated phase changes in the shell layer with a larger specific surface area due to a high degree of participation in the reaction, thereby improving the cyclic stability of the material.

[0115] The present application further introduces a high-bond-energy first lattice control element into the core of sodium nickel iron manganese zincate, and simultaneously introduces a high-bond-energy first lattice control element and a high-oxidation-state second lattice control element into the shell of sodium nickel iron manganese zincate. By regulating the interlayer spacing, bond energy and intrinsic distortion of the lattice, the structural stability of the material is further improved, and the diffusion efficiency of Na ions is improved, thereby achieving a simultaneous improvement in cycle performance and rate performance.

[0116] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. An O3-type layered oxide sodium ion positive electrode material, characterized in that: The positive electrode material comprises a nickel iron sodium manganese zincate core and a nickel iron sodium manganese zincate shell; In the sodium nickel-iron-manganese-zincate core, zinc accounts for 7% to 10% of the total molar amount of nickel-iron-manganese-zinc; In the sodium nickel-iron-manganese-zincate shell, zinc accounts for 1% to 5% of the total molar amount of nickel-iron-manganese-zinc; The sodium nickel iron manganese zincate core and the sodium nickel iron manganese zincate shell each independently include a first lattice control element; the sodium nickel iron manganese zincate shell also includes a second lattice control element; In the positive electrode material, the mass percentage of the sodium nickel iron manganese zincate core is 15% to 40%, and the mass percentage of the sodium nickel iron manganese zincate shell is 60% to 85%; The first lattice regulating element includes any one or a combination of at least two of Ti, Y, Zr, La, Ce, Ca or Al; The second lattice regulating element includes any one of Cu, Co, Nb, Sn, Sb, Cr, Mn, Mo, W, Re or Ru, or a combination of at least two thereof.

2. The positive electrode material according to claim 1, wherein In the sodium nickel iron manganese zincate core, the doping amount of the first lattice control element is 0.1 mol% to 1 mol% of the sodium nickel iron manganese zincate core; And / or, in the sodium nickel iron manganese zincate shell, the doping amount of the first lattice regulating element and the second lattice regulating element are each independently 0.1 mol% to 1 mol% of the sodium nickel iron manganese zincate shell.

3. The positive electrode material according to claim 1, wherein In the sodium nickel iron manganese zincate shell, the alkali metal layer spacing d O-Na , transition metal interlayer spacing d TM-TM , the weighted average ionic radius r of the first lattice regulating element and the second lattice regulating element AB and the average radius r of the sodium ion Na Satisfy between: (d O-Na· r Na ) / (d TM-TM· r AB )=δ1,1.9<δ1<2.5; Among them, d O-Na d TM-TM 、r AB With r Na The unit of Å is Å; And / or, in the positive electrode material, the average value of the bond energy between the first lattice regulating element and oxygen and the bond energy between the second lattice regulating element and oxygen is recorded as E bond The average unit cell volume of the cathode material is similar to that of the standard NaNi 0.35 Zn 0.05 Fe 0.28 Mn 0.32 The difference in the volume of the O2 unit cell is recorded as ΔV, and the E bond and ΔV satisfy: ln(E bond ) / (ΔV ½ )=δ2,3.0<δ2<3.6;where,E bond The unit of is kJ / mol, and the unit of ΔV is Å 3 .

4. The positive electrode material according to claim 1, wherein In the positive electrode material, the mass percentage of the sodium nickel iron manganese zincate core is 15% to 40%, and the mass percentage of the sodium nickel iron manganese zincate shell is 60% to 85%.

5. The positive electrode material according to claim 1, wherein The chemical formula of the sodium nickel iron manganese zincate core is Na x Ni 1-u-v-w Zn u Fe v Mn w A y O2, where 0.95≤x≤1.05, 0.07≤u≤0.1, 0.15≤v≤0.35, 0.15≤w≤0.35, 0.001≤y≤0.01; The chemical formula of the sodium nickel iron manganese zincate shell is Na m Ni 1-a-b-c Zn a Fe b Mn c A d B e O2, where 0.95≤m≤1.05, 0.01≤a≤0.05, 0.2≤b≤0.4, 0.2≤c≤0.4, 0.001≤d≤0.01, 0.001≤e≤0.01; A includes any one or a combination of at least two of Ti, Y, Zr, La, Ce, Ca or Al, and B includes any one or a combination of at least two of Cu, Co, Nb, Sn, Sb, Cr, Mn, Mo, W, Re or Ru.

6. A method for preparing the O3-type layered oxide sodium ion positive electrode material according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The sodium nickel iron manganese zincate core precursor, the first lattice control compound and the sodium salt are first mixed to obtain a first mixture; and a first sintering is performed to obtain the sodium nickel iron manganese zincate core; The sodium nickel iron manganese zincate core, the first lattice regulation compound, the second lattice regulation compound, the sodium nickel iron manganese zincate shell precursor and the sodium salt are mixed for a second time to obtain a second mixture; and a second sintering is performed to obtain the O3 type layered oxide sodium ion positive electrode material.

7. The preparation method according to claim 6, wherein The first lattice control compound includes any one or a combination of at least two of TiO2, Y2O3, ZrO2, La2O3, CeO2, CaO or Al2O3; And / or, the second lattice control compound includes any one or a combination of at least two of CuO, Co2O3, Nb2O5, SnO2, Sb2O5, Cr2O3, MnO2, MoO3, WO3, ReO3 or RuO2.

8. The preparation method according to claim 6, wherein The temperature of the first sintering is 800° C. to 1000° C.; And / or, the first sintering time is 6h~20h; And / or, the temperature of the second sintering is 900° C. to 1050° C.; And / or, the second sintering time is 6h~20h; And / or, the atmosphere of the first sintering and the second sintering is independently an oxygen-containing atmosphere.

9. A positive electrode sheet, characterized in that: The positive electrode comprises the O3-type layered oxide sodium ion positive electrode material according to any one of claims 1 to 5.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the O3-type layered oxide sodium ion positive electrode material according to any one of claims 1 to 5, or comprises the positive electrode sheet according to claim 9.

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