A positive electrode material, a preparation method thereof, a positive electrode sheet, and a battery

Abstract

The application relates to the technical field of batteries, in particular to a positive electrode material, a preparation method thereof, a positive electrode sheet and a battery. The positive electrode material comprises a lithium-rich manganese-based oxide, the chemical formula of the lithium-rich manganese-based oxide is Li x‑y T y (Mn a Ni b Co (1‑a‑b) ) 2‑x O2; wherein, 1.0<=x<=1.2, 0<=y<=0.03, 0.6<=a<=0.75, 0.2<=b<=0.4, and T is a doped metal element; the composite phase of the lithium-rich manganese-based oxide comprises an O2 phase, a T2 phase and an O3 phase; wherein, the sum of the molar ratios of the O2 phase and the T2 phase in the composite phase is less than or equal to 85%; and the molar ratio of the O3 phase is greater than or equal to 15%. The specific capacity, cycle retention rate and rate performance of the composite-phase lithium-rich manganese-based positive electrode material provided by the application are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a positive electrode material and its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] With the rapid development of the power battery market, there is an urgent need to develop systems with higher energy density. Considering that cathode materials are the weakest link in battery systems, lithium-rich manganese-based oxygen materials, as the cathode materials with the highest known specific capacity, are expected to help the battery field achieve breakthroughs. However, O3-type lithium-rich manganese-based materials produced by traditional sintering methods face many technical challenges, including rapid capacity decay, low initial coulombic efficiency, poor rate performance, and low compaction density, which seriously hinder the market application of this material. The root cause of these problems lies in the inherent microstructure of the O3 phase. Firstly, in the high-voltage section, the process of lattice oxygen participating in the redox reaction is highly uncontrollable, leading to irreversible structure. Secondly, the mobility of lithium ions in lithium-rich manganese-based material systems is extremely low, making it difficult to achieve efficient and rapid insertion and extraction.

[0003] In recent years, a novel layered stacking mode of O2-type lithium-rich manganese-based cathode material has been extensively studied to address the aforementioned problems. Existing technology first mixes a precursor, lithium salt, and sodium salt in a specific ratio and sintersects them at high temperature in an air atmosphere to form a P2-phase sodium ion layered oxide as an intermediate. Then, through ion exchange at low temperature, sodium ions are replaced with lithium ions to prepare the O2-type lithium-rich manganese-based cathode material. Compared with O3-type lithium-rich manganese-based cathode materials prepared by conventional sintering methods, the O2 type exhibits superior cycle stability and structural reversibility.

[0004] However, existing O2-phase lithium-rich manganese-based materials and their preparation technologies have the following main problems: Due to the low lithium-ion migration efficiency and incomplete ion exchange process in lithium-rich manganese-based cathode materials, lithium vacancies always exist in the initial bulk phase, forming a lithium-deficient state. This prevents the cathode material from reaching its full capacity, requiring lithium replenishment through the electrolyte or anode. This is reflected in the initial coulombic efficiency exceeding 110% in half-cell tests. The lithium-deficient characteristics of pure O2-phase lithium-rich manganese-based cathode materials mean that their actual discharge specific capacity does not show a significant advantage compared to modified O3-phase lithium-rich manganese-based cathode materials. Furthermore, although the special layered stacked structure provides higher reversibility, O2-phase lithium-rich manganese-based cathode materials still suffer from severe voltage decay, which is particularly pronounced under high-rate conditions.

[0005] The ion exchange step in the preparation of pure O2 phase relies on the exchange of sodium ions in the P2 sodium mesophase with a large amount of lithium source. Since these lithium sources are expensive and bulky, the preparation cost increases and the efficiency decreases, which becomes a huge barrier to industrial application.

[0006] Existing O2 phase lithium-rich manganese-based cathode materials have not yet been commercialized due to inherent material defects and immature processes, and are still in the technology development stage. Summary of the Invention

[0007] To address the problems of pure O2 phase lithium-rich manganese-based cathode materials in the prior art, this invention provides a cathode material, its preparation method, a cathode sheet, and a battery.

[0008] In a first aspect, the present invention provides a cathode material comprising a lithium-rich manganese-based oxide, wherein the chemical formula of the lithium-rich manganese-based oxide is Li. x-y T y (Mn a Ni b Co (1-a-b) ) 2-x O2; where 1.0≤x≤1.2, 0≤y≤0.03, 0.6≤a≤0.75, 0.2≤b≤0.4, and T is the doped metal element; The composite phase of the lithium-rich manganese-based oxide includes an O2 phase, a T2 phase, and an O3 phase; Wherein, the sum of the molar proportions of the O2 phase and the T2 phase in the composite phase is less than or equal to 85%; The molar proportion of the O3 phase is greater than or equal to 15%.

[0009] The cathode material exhibits a discharge capacity of 276 mAh / g within an electrochemical window of 2.0–4.8 V and a charge / discharge rate of 0.1 C, with an initial coulombic efficiency reduction to 105%. It also retains a discharge capacity of over 250 mAh / g at charge / discharge rates of 0.5 C and 1 C, and after 50 cycles, the capacity retention exceeds 80%.

[0010] In one embodiment of the present invention, the molar ratio of the O2 phase in the composite phase is 65%-85%, the molar ratio of the T2 phase in the composite phase is 0%-20%, and the molar ratio of the O3 phase in the composite phase is 15%-30%.

[0011] In one embodiment of the present invention, the lithium-rich manganese-based oxide with the T2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°; The lithium-rich manganese-based oxide with the O2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 18.2°≤θ2≤18.5°; The lithium-rich manganese-based oxide with the O3 phase structure has characteristic peaks for the (003) crystal plane in the range of 18.5°≤θ3≤18.8°.

[0012] In one embodiment of the present invention, the lithium-rich manganese-based oxide with T2 phase structure has a characteristic peak intensity of I1 corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°; The lithium-rich manganese-based oxide with the O2 phase structure has a characteristic peak intensity of I2 on the (002) crystal plane in the range of 18.2°≤θ2≤18.5°. The lithium-rich manganese-based oxide with the O3 phase structure has a characteristic peak intensity of I3 on ​​the (003) crystal plane in the range of 18.5°≤θ3≤18.8°. The I1, I2, and I3 satisfy 0 < I1 / I2 ≤ 0.5 and 0 < I3 / I2 ≤ 0.5.

[0013] In one embodiment of the present invention, I1, I2, and I3 satisfy 0 ≤ I1 / I2 ≤ 0.2 and 0.1 ≤ I3 / I2 ≤ 0.3.

[0014] In one embodiment of the present invention, the doped metal element is one or more of Ti, Zr, Mo, La and Nb.

[0015] In one embodiment of the present invention, the lithium-rich manganese-based oxide is a single crystal particle; Preferably, the particle size D50 of the lithium-rich manganese-based oxide is 1-5 μm; Preferably, the specific surface area of ​​the lithium-rich manganese-based oxide is 1-35 m². 2 / g.

[0016] Secondly, the present invention provides a method for preparing a positive electrode material, comprising the following steps: Sodium source, first lithium source, doped metal source and precursor are mixed and calcined in proportion to obtain a composite product containing single crystal P2 phase sodium ion oxide and O3 phase lithium ion oxide. The composite product was mixed with a second lithium source in a certain proportion and subjected to an ion exchange reaction to obtain a composite phase lithium-rich manganese-based oxide. Preferably, the particle size D50 of the precursor is 2-8 μm; Preferably, the specific surface area of ​​the precursor is 20-35 m². 2 / g; Preferably, the calcination is carried out at a heating rate of 1-10℃ / min; Preferably, the calcination temperature is 700-900℃, and the calcination time is 8-24h; Preferably, the heating rate of the ion exchange reaction is 1-20 °C / min; Preferably, the ion exchange reaction is carried out at one or more temperatures within the temperature range of 250-350°C; the duration of the ion exchange reaction is 4-15 hours.

[0017] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material as described above, or the positive electrode sheet comprising the positive electrode material prepared by the preparation method as described above.

[0018] Fourthly, the present invention provides a battery comprising the positive electrode material as described above, or the battery comprising the positive electrode sheet as described above.

[0019] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Unless otherwise specified, the positional relationships shown in the drawings in the following description are based on the direction in which the components are drawn in the figure.

[0021] Figure 1 The XRD pattern of the T2 / O2 / O3 composite phase lithium-rich manganese-based oxide prepared in Example 1 of this invention; Figure 2 The XRD pattern of the O2 / O3 composite phase lithium-rich manganese-based oxide prepared in Example 2 of this invention; Figure 3 The XRD pattern of the T2 / O2 composite phase lithium-rich manganese-based oxide prepared in Comparative Example 1 of this invention is shown. Figure 4 The XRD pattern of the T2 / O3 composite phase lithium-rich manganese-based oxide prepared in Comparative Example 2 of this invention is shown. Figure 5 The first charge-discharge curve of the button battery made from the positive electrode material of Example 1 of the present invention; Figure 6 The first charge-discharge curve of the button battery made from the positive electrode material of Example 2 of the present invention; Figure 7 The first charge-discharge curve of the button battery made from the positive electrode material of Example 3 of the present invention; Figure 8 The first charge-discharge curve of the button battery made from the positive electrode material of Example 4 of the present invention; Figure 9The first charge-discharge curve of the button battery made from the positive electrode material of Example 5 of the present invention; Figure 10 The first charge-discharge curve of the button battery made from the cathode material of Comparative Example 1 of this invention; Figure 11 The first charge-discharge curve of the button battery made of the positive electrode material of Comparative Example 2 of this invention; Figure 12 The first charge-discharge curve of the button battery made from the cathode material of Comparative Example 3 of this invention; Figure 13 The first charge-discharge curve of the button battery made from the cathode material of Comparative Example 4 of this invention; Figure 14 A comparison chart of the coin cell performance of the embodiment of the present invention and the positive electrode material of the embodiment after 50 cycles at 0.5C rate. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0024] This invention introduces and modulates the T2 and O3 phases into an O2-phase lithium-rich manganese-based cathode material to prepare a composite phase. By utilizing the physicochemical properties of each phase to establish a three-phase synergistic effect, and combining it with single crystallization and bulk doping design, this invention not only effectively solves the voltage decay and lithium deficiency problems existing in the current O2-phase lithium-rich manganese-based cathode material, but also significantly improves its specific capacity and rate performance, thus significantly enhancing the electrical performance of the cathode material. At the same time, this technical solution has low cost and is easy to implement, which is expected to accelerate the market application of this cathode material.

[0025] One embodiment of the present invention provides a cathode material, the cathode material comprising a lithium-rich manganese-based oxide, the lithium-rich manganese-based oxide having the chemical formula Li. x-y T y (Mn a Ni b Co (1-a-b) ) 2-x O2; where 1.0≤x≤1.2, 0≤y≤0.03, 0.6≤a≤0.75, 0.2≤b≤0.4, and T is the doped metal element; The composite phase of the lithium-rich manganese-based oxide includes an O2 phase, a T2 phase, and an O3 phase; Wherein, the sum of the molar proportions of the O2 phase and the T2 phase in the composite phase is less than or equal to 85%, preferably 60%-80%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., but not limited to the listed values, other unlisted values ​​within this range are also applicable; the molar proportion of the O3 phase is greater than or equal to 15%, such as 15%, 20%, 25%, 30% or any value between them.

[0026] It is worth noting that although other cathode material systems also possess T2, O2, and O3 phase structures, the chemical composition, microstructure, role, and charge / discharge process performance of these phases in lithium-rich manganese-based cathode materials are completely different from those in other systems. This will be explained in detail below: O3-phase lithium-rich manganese-based oxides are stable, exhibiting high specific capacity and lithium content. However, their structure suffers from poor reversibility during charge / discharge, and severe interfacial side reactions lead to rapid capacity decay and low initial coulombic efficiency. O2-phase lithium-rich manganese-based oxides are metastable. Due to their unique oxygen atom stacking structure, they are more stable and can suppress irreversible oxygen loss and transition metal ion migration during charge / discharge, thus exhibiting high capacity and high cycle retention. However, the O2 phase relies on ion exchange methods for preparation, resulting in bulk lithium deficiency. Furthermore, the O2 phase still suffers from voltage decay, particularly severe at high rates. T2-phase lithium-rich manganese-based oxides are metastable orthorhombic phases, typically lithium-deficient. They exhibit extremely high cycle stability during charge / discharge, but their capacity is low, thus they are rarely considered in practical applications. The inventors have discovered that introducing a certain amount of T2 and O3 phases into the O2 phase can not only compensate for the inherent defects of the O2, T2, and O3 phases but also induce a synergistic effect, significantly improving the battery performance of the cathode material. Specific experiments revealed that introducing the T2 phase into the O2 phase can improve the material's cycle performance, enhancing the cycle stability and rate performance of the composite phase. However, excessively high T2 phase content can lead to a decrease in material capacity. The introduced O3 phase can form a solid solution with the O2 phase, optimizing cycle performance. Simultaneously, it replenishes lithium to the O2 phase during charge and discharge, addressing lithium deficiency and improving the material's capacity and cycle performance. However, excessively high O3 phase content can cause a decrease in cycle performance and a sharp increase in impedance. In summary, within a specific molar ratio range in lithium-rich manganese-based cathode materials, the three phases can form an effective synergistic effect, significantly improving the overall performance of the cathode material.

[0027] In a preferred embodiment of the present invention, the molar ratio of the O2 phase in the composite phase is 65%-85%, preferably 65%-75%, for example 65%, 70%, 75%, 80%, 85% or any value therebetween; the molar ratio of the T2 phase in the composite phase is 0%-20%, preferably 0%-15%, for example 0%, 5%, 10%, 15%, 20% or any value therebetween; the molar ratio of the O3 phase in the composite phase is 15%-30%, preferably 20%-30%, for example 15%, 20%, 25%, 30% or any value therebetween.

[0028] In one embodiment of the present invention, please refer to Figure 1 The lithium-rich manganese-based oxide with T2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°, wherein the intensity of the characteristic peaks corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8° is I1; The lithium-rich manganese-based oxide with the O2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 18.2°≤θ2≤18.5°, wherein the intensity of the characteristic peak of the (002) crystal plane in the range of 18.2°≤θ2≤18.5° is I2; The lithium-rich manganese-based oxide with the O3 phase structure has a characteristic peak for the (003) crystal plane in the range of 18.5°≤θ3≤18.8°, wherein the intensity of the characteristic peak of the (003) crystal plane of the lithium-rich manganese-based oxide with the O3 phase structure in the range of 18.5°≤θ3≤18.8° is I3.

[0029] In a preferred embodiment of the present invention, I1, I2, and I3 satisfy 0 < I1 / I2 ≤ 0.5 and 0 < I3 / I2 ≤ 0.5. When the cathode material satisfies the above formula, the cathode material has better rate performance, specific capacity, and first coulombic efficiency. More preferably, I1, I2, and I3 satisfy 0 ≤ I1 / I2 ≤ 0.2 and 0.1 ≤ I3 / I2 ≤ 0.3.

[0030] In one embodiment of the present invention, the doped metal element is one or more of Ti, Zr, Mo, La and Nb. The purpose of doping the composite phase lithium-rich manganese-based oxide of the present invention with transition metal element T is: (1) the selected doped element ions play a supporting role in the layered structure and widen the lithium ion transport channel, thereby improving the ion exchange efficiency; (2) the selected doped element is enriched near the surface of the grains, which plays a role in inhibiting oxygen evolution and protecting the interface, thereby effectively reducing the interface side reaction and improving the reversibility of oxygen anion redox, thereby improving the capacity and cycle retention rate of the cathode material; (3) the selected doped element can regulate grain growth, refine grains, and improve particle morphology during sintering and ion exchange, thereby further improving the capacity and compaction density of the cathode material.

[0031] In a preferred embodiment of the present invention, the lithium-rich manganese-based oxide is a single crystal particle; the particle size D50 of the lithium-rich manganese-based oxide is 1-5 μm, for example 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value between them; the specific surface area of ​​the lithium-rich manganese-based oxide is 1 m². 2 / g-35m 2 / g, for example, 1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 / g、35m 2 / g or any value between them. Using small-sized single-crystal particles can not only improve lithium-ion migration efficiency, but also ensure that all particle surfaces are in full contact with the electrolyte, further improving the electrical performance of the cathode material.

[0032] This invention provides a method for preparing a cathode material, comprising the following steps: Step 1: Mix and calcine the sodium source, the first lithium source, the doped metal source and the precursor in a certain proportion to obtain a composite product containing single-crystal P2 phase sodium ion oxide and O3 phase lithium ion oxide. In an exemplary embodiment of the present invention, the sodium source, the first lithium source, the doped metal source, and the precursor are preferably mixed and calcined in a molar ratio of n(Na): n(Li): n(T): n(Mn+Ni+Co) = 0.83:(xy-1):y:(2-x) to obtain a composite product containing single-crystal P2 phase sodium ion oxide and O3 phase lithium ion oxide; it should be noted that the doped metal source may be added or not added depending on the actual situation.

[0033] In an exemplary embodiment of the present invention, in step one, the sodium source is sodium carbonate or sodium hydroxide; the first lithium source is lithium carbonate or lithium hydroxide; and the doped metal source is one or more of titanium oxide, zirconium oxide, lanthanum oxide, molybdenum oxalate, and ammonium niobate oxalate.

[0034] In an exemplary embodiment of the present invention, the binary precursor is a nickel-manganese hydroxide or carbonate compound, and n(Ni):n(Mn) = a:b; the ternary precursor is a nickel-cobalt-manganese hydroxide or carbonate compound, and n(Ni):n(Mn):n(Co) = a:b:(1-ab); preferably, the particle size D50 of the precursor is 2-8 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any value between them; the specific surface area of ​​the precursor is 20-35 m². 2 / g, for example 20m 2 / g、21m 2 / g、22m 2 / g、23m 2 / g、24m 2 / g、25m 2 / g、26m 2 / g、27m 2 / g、28m 2 / g、29m 2 / g、30m 2 / g、31m 2 / g、32m 2 / g、33m 2 / g、34m 2 / g、35m 2 / g or any value between them; thereby improving ion conversion efficiency by obtaining composite products with smaller particle size and larger specific surface area.

[0035] In an exemplary embodiment of the present invention, the calcination is carried out at a heating rate of 1-10℃ / min, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any value between therewith; the calcination temperature is 700-900℃, for example, 700℃, 750℃, 800℃, 850℃, 900℃ or any value between therewith; the calcination time is 8-24h, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h or any value between therewith.

[0036] Step 2: Mix the composite product with a second lithium source in a certain proportion and carry out an ion exchange reaction to obtain a composite phase lithium-rich manganese-based oxide. In an exemplary embodiment of the present invention, the composite product obtained in step one is mixed with a second lithium source in a certain proportion and then subjected to ion exchange at low temperature. The residual salt is then removed by water washing, and finally the composite phase lithium-rich manganese-based oxide powder is obtained by vacuum drying. In an exemplary embodiment of the present invention, in step two, the second lithium source is lithium nitrate or a mixture of lithium nitrate and lithium chloride, and the exchange process replaces sodium ions and some vacancies in the composite product with lithium ions to form T2 and O2 phases.

[0037] In an exemplary embodiment of the present invention, the heating rate of the ion exchange reaction is 1-20℃ / min, for example 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 14℃ / min, 16℃ / min, 18℃ / min, 20℃ / min or any value between them.

[0038] In an exemplary embodiment of the present invention, the ion exchange reaction is carried out in a temperature range of 250-350°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C or any value therebetween; the duration of the ion exchange reaction is 4-15 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or any value therebetween.

[0039] In another exemplary embodiment of the present invention, the ion exchange reaction is carried out at one or more temperatures within a temperature range of 250-350°C; Preferably, the temperature is above 250°C and below 320°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C or any value between them.

[0040] It is worth noting that different exchange temperatures can create suitable conditions for the formation of each phase at different stages. In the low temperature range, it is conducive to the formation of the metastable O2 phase. As the temperature increases, the ion exchange reaction can be more complete, further improving the degree of ion exchange and the lithium content of the system.

[0041] In step two, the mixing ratio of the composite product and the second lithium source is preferably such that the ratio of lithium in the second lithium source to sodium in the composite product is 1-5, for example, 1, 2, 3, 4, 5 or any value between them. The ratio of the T2 phase and the O2 phase is controlled by adjusting the exchange temperature and the lithium-sodium ion ratio. Using less second lithium source can also reduce the cost of the ion exchange step, increase the amount of material packed, and thus increase the yield.

[0042] Furthermore, the positive electrode and battery of the present invention will be described appropriately below.

[0043] Generally, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0044] The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes the positive electrode material of the first aspect of the present invention or the positive electrode material obtained by the method of the second aspect of the present invention.

[0045] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0046] In some embodiments of the present invention, the positive current collector may be a metal foil or a composite current collector.

[0047] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0048] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0049] In some embodiments of the present invention, the negative electrode current collector may be a metal foil or a composite current collector.

[0050] In some embodiments of the present invention, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0051] Electrolytes function to conduct ions between the positive and negative electrodes. This invention does not impose particular limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0052] In some embodiments of the present invention, the battery further includes a separator. The present invention does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0053] In some embodiments of the present invention, the battery may include one or more battery cells. In this invention, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy into electrical energy, and typically includes at least a positive electrode, a negative electrode, and an electrolyte. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of active ions between the positive and negative electrode.

[0054] The present invention does not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape.

[0055] In this invention, the battery can also be a battery module or a battery pack.

[0056] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0057] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0058] Example 1 This embodiment provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75) were uniformly mixed in a ratio of n(Na):n(Li):n(Mn+Ni)=0.83:0.25:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 800℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0059] Step 2: The composite product obtained in Step 1 is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange, heated to 280℃ at a rate of 10℃ / min and held for 4 hours, and then cooled to room temperature with the furnace. After crushing, washing with water and drying, a composite phase lithium-rich manganese-based oxide powder is obtained.

[0060] Example 2 This embodiment provides a method for preparing an O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, and nickel-cobalt-manganese ternary hydroxide (n(Ni):n(Co):n(Mn)=0.2:0.1:0.7) were uniformly mixed in a ratio of n(Na):n(Li):n(Mn+Ni+Co)=0.83:0.25:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0061] Step two: The composite product obtained in step one is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange. The temperature is first increased to 280℃ at a rate of 10℃ / min and held for 2 hours, then increased to 320℃ at a rate of 1℃ / min and held for 6 hours. After cooling to room temperature in the furnace, the powder is crushed, washed with water, and dried to obtain a composite phase lithium-rich manganese-based oxide powder.

[0062] Example 3 This embodiment provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, and nickel-cobalt-manganese ternary hydroxide (n(Ni):n(Co):n(Mn)=0.2:0.05:0.75) were uniformly mixed in a ratio of n(Na):n(Li):n(Mn+Ni+Co)=0.83:0.25:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 800℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0063] Step two: The composite product obtained in step one is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange. The temperature is first increased to 280℃ at a rate of 10℃ / min and held for 2 hours, then increased to 340℃ at a rate of 1℃ / min and held for 6 hours. After cooling to room temperature in the furnace, the powder is crushed, washed with water, and dried to obtain a composite phase lithium-rich manganese-based oxide powder.

[0064] Example 4 This embodiment provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, niobium ammonium oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.23:0.02:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 800℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0065] Step 2: The composite product obtained in Step 1 is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange, heated to 280℃ at a rate of 10℃ / min and held for 4 hours, and then cooled to room temperature with the furnace. After crushing, washing with water and drying, a composite phase lithium-rich manganese-based oxide powder is obtained.

[0066] Example 5 This embodiment provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, ammonium niobate oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.23:0.02:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 850℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0067] Step 2: The composite product obtained in Step 1 is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange, heated to 280℃ at a rate of 10℃ / min and held for 4 hours, and then cooled to room temperature with the furnace. After crushing, washing with water and drying, a composite phase lithium-rich manganese-based oxide powder is obtained.

[0068] Comparative Example 1 This comparative example provides a method for preparing a T2 / O2 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, niobium ammonium oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.08:0.02:0.9 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 850℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain P2 phase sodium ion oxide.

[0069] Step 2: The composite product obtained in Step 1 is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange, heated to 280℃ at a rate of 10℃ / min and held for 4 hours, and then cooled to room temperature with the furnace. After crushing, washing with water and drying, a composite phase lithium-rich manganese-based oxide powder is obtained.

[0070] Comparative Example 2 This comparative example provides a method for preparing a T2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, niobium ammonium oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.23:0.02:0.75 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 800℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0071] Step two: The composite product obtained in step one is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange. The temperature is first increased to 280℃ at a rate of 10℃ / min and held for 2 hours, then increased to 380℃ at a rate of 1℃ / min and held for 6 hours. After cooling to room temperature in the furnace, the powder is crushed, washed with water, and dried to obtain a composite phase lithium-rich manganese-based oxide powder.

[0072] Comparative Example 3 This comparative example provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, ammonium niobate oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.33:0.02:0.65 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 800℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0073] Step two: The composite product obtained in step one is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange. The temperature is first increased to 280℃ at a rate of 10℃ / min and held for 2 hours, then increased to 350℃ at a rate of 1℃ / min and held for 6 hours. After cooling to room temperature in the furnace, the powder is crushed, washed with water, and dried to obtain a composite phase lithium-rich manganese-based oxide powder.

[0074] Comparative Example 4 This comparative example provides a method for preparing a T2 / O2 / O3 composite phase lithium-rich manganese-based cathode material, including the following steps: Step 1: Sodium carbonate, lithium carbonate, ammonium niobate oxalate, and nickel-manganese binary hydroxide (n(Ni):n(Mn)=0.25:0.75)) were uniformly mixed in a ratio of n(Na):n(Li):n(Nb):n(Mn+Ni)=0.83:0.13:0.02:0.85 to obtain a mixed powder sample. The mixed powder sample was placed in a box furnace and heated to 450℃ at a rate of 3℃ / min and held for 5 hours. Then, the temperature was increased to 850℃ at a rate of 3℃ / min and held for 12 hours. After that, the furnace was cooled to room temperature to obtain a composite product of P2 phase sodium ion oxide and O3 phase lithium ion oxide.

[0075] Step two: The composite product obtained in step one is uniformly mixed with lithium nitrate at a ratio of n(Na):n(Li) = 1:3 to obtain a mixed powder sample. The mixed powder sample is then placed in a low-temperature furnace for static ion exchange. The temperature is first increased to 280℃ at a rate of 10℃ / min and held for 2 hours, then increased to 310℃ at a rate of 1℃ / min and held for 6 hours. After cooling to room temperature in the furnace, the powder is crushed, washed with water, and dried to obtain a composite phase lithium-rich manganese-based oxide powder.

[0076] Battery manufacturing The cathode materials obtained in each embodiment and comparative example were used to prepare lithium-ion battery cathode sheets: The positive electrode material, conductive additive Super P, and binder polyvinylidene fluoride were mixed at a mass ratio of 90:5:5, and an appropriate amount of organic solvent N-methylpyrrolidone was added to form a uniformly dispersed slurry. This slurry was then uniformly coated onto an aluminum foil current collector using a scraper and placed in an oven to dry at 130°C for 20 min. The dried aluminum foil was then rolled and cut into circular electrode sheets, which were stored in a vacuum oven at 80°C for 12 h. The dried positive electrode sheets, separator, electrolyte, and negative electrode sheets were then sequentially assembled in a glove box to obtain a lithium-ion battery.

[0077] Body phase characterization Figure 1 The XRD pattern of the T2 / O2 / O3 composite phase lithium-rich manganese-based oxide prepared in Example 1; Figure 2 The XRD pattern of the O2 / O3 composite phase lithium-rich manganese-based oxide prepared in Example 2; Figure 3 The XRD pattern of the T2 / O2 composite phase lithium-rich manganese-based oxide prepared in Comparative Example 1 is shown. Figure 4 The XRD pattern of the T2 / O3 composite phase lithium-rich manganese-based oxide prepared in Comparative Example 2 is shown. from Figure 1 It can be seen that the lithium-rich manganese-based oxide with the T2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°; the lithium-rich manganese-based oxide with the O2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 18.2°≤θ2≤18.5°; and the lithium-rich manganese-based oxide with the O3 phase structure has characteristic peaks corresponding to the (003) crystal plane in the range of 18.5°≤θ3≤18.8°.

[0078] The cathode materials prepared in Examples 1-5 and Comparative Examples 1-4 were characterized by XRD diffraction, and their phase composition was calculated. Table 1 shows the molar ratio of each phase in the cathode materials of each example and comparative example obtained by XRD testing.

[0079] Table 1

[0080] Electrochemical performance testing Specific capacity and initial coulombic efficiency tests: At room temperature, charge to 4.8V with a constant current of 0.1C, then charge with a constant voltage, with a cutoff current of 0.02C, and then discharge to 2.0V with a constant current of 0.1C. Record the discharge specific capacity and initial coulombic efficiency.

[0081] Rate performance test: At room temperature, the first cycle is activated by constant current charging at 0.5C and 1C to 4.8V, followed by constant voltage charging with a cutoff current of 0.02C. Then, the discharge is carried out at constant current of 0.1C to 2.0V, and the discharge specific capacity is recorded. The above steps are repeated 50 times. The discharge capacity of the first cycle is recorded as C1 and the capacity of the 50th cycle is recorded as C50. The capacity retention rate after 50 cycles is calculated as % = (C50 / C1) * 100%.

[0082] The test results are shown in the table below.

[0083] Table 2

[0084] According to the table above, refer to Figure 5 and Figure 14The button cell made from the cathode material of Example 1 had discharge specific capacities of 261 mAh / g, 246 mAh / g, and 220 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 110%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 92% and 84%, respectively. refer to Figure 6 The button cell made from the cathode material of Example 2 had discharge specific capacities of 260 mAh / g, 258 mAh / g, and 245 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 109%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 80% and 81%, respectively.

[0085] refer to Figure 7 The button cell made from the cathode material of Example 3 had discharge specific capacities of 255 mAh / g, 253 mAh / g, and 252 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 100%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 89% and 83%, respectively.

[0086] refer to Figure 8 and Figure 14 The button cell made from the cathode material of Example 4 had discharge specific capacities of 267 mAh / g, 259 mAh / g, and 251 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 106%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 89% and 81%, respectively.

[0087] refer to Figure 9 and Figure 14 The button cell made from the cathode material of Example 5 had discharge specific capacities of 276 mAh / g, 264 mAh / g, and 244 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 105%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 85% and 83%, respectively.

[0088] refer to Figure 10 and Figure 14The button cell made from the cathode material of Comparative Example 1 exhibited discharge specific capacities of 246 mAh / g, 251 mAh / g, and 244 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. Its initial coulombic efficiency at 0.1C was 127%, and its capacity retention rates after 50 cycles at 0.5C and 1C were 84% and 81%, respectively. Due to the lack of the O3 phase, the cathode material suffered from severe lithium deficiency, resulting in an excessively high initial coulombic efficiency, making it unsuitable for use in actual production full cells. Furthermore, the synergistic effect was disrupted, leading to a deterioration in capacity and cycle performance, significantly inferior to the examples.

[0089] refer to Figure 11 and Figure 14 The button cell made from the cathode material of Comparative Example 2 exhibited discharge specific capacities of 203 mAh / g, 190 mAh / g, and 185 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 92%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 105% and 99%, respectively. Due to the lack of the O2 phase, the capacity decreased significantly at all rates. During charging, the O3 structure collapsed rapidly, forming stable spinel and rock salt phases, thus ceasing to exhibit lithium-rich characteristics, resulting in performance significantly inferior to the examples.

[0090] refer to Figure 12 and Figure 14 The button cell made from the cathode material of Comparative Example 3 exhibited discharge specific capacities of 243 mAh / g, 239 mAh / g, and 234 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. The initial coulombic efficiency at 0.1C was 112%, and the capacity retention rates after 50 cycles at 0.5C and 1C were 88% and 86%, respectively. Because the molar ratio of the three phases T2, O2, and O3 was not within the control range of this invention, the synergistic effect was poor, resulting in a decrease in capacity at all rates, an increase in initial coulombic efficiency, and significantly inferior performance compared to the examples.

[0091] refer to Figure 13 and Figure 14 The button cell made from the cathode material of Comparative Example 4 exhibited discharge specific capacities of 251 mAh / g, 245 mAh / g, and 233 mAh / g at 0.1C, 0.5C, and 1C rates, respectively. Its initial coulombic efficiency at 0.1C was 116%, and its capacity retention rates after 50 cycles at 0.5C and 1C were 85% and 82%, respectively. In Comparative Example 4, the ratio of T2 to O2 was within the constraints of claim 1, but the T2+O2 ratio exceeded 85%, resulting in poor synergistic effect. The capacity decreased at all rates, while the initial coulombic efficiency increased, making its performance significantly inferior to the examples.

[0092] In summary, compared with the prior art, the composite phase lithium-rich manganese-based cathode material prepared by the present invention achieves synergistic effects by simultaneously introducing T2 and O3 phases into the O2 phase lithium-rich manganese-based cathode material and adjusting their ratio. Combined with bulk doping technology, the specific capacity, cycle retention rate and rate performance of the composite phase lithium-rich manganese-based cathode material are significantly improved.

[0093] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0094] Although this document frequently uses terms such as cathode material, lithium-rich manganese-based oxide, composite phase, nanosource, lithium source, doped metal source, precursor, and ion exchange reaction, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention. The terms "first," "second," etc. (if present) in the specification, claims, and accompanying drawings of the embodiments of the invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a lithium-rich manganese-based oxide, the chemical formula of which is Li. x-y T y (Mn a Ni b Co (1-a-b) ) 2-x O2; where 1.0≤x≤1.2, 0≤y≤0.03, 0.6≤a≤0.75, 0.2≤b≤0.4, and T is the doped metal element; The composite phase of the lithium-rich manganese-based oxide includes an O2 phase, a T2 phase, and an O3 phase; Wherein, the sum of the molar proportions of the O2 phase and the T2 phase in the composite phase is less than or equal to 85%; The molar proportion of the O3 phase is greater than or equal to 15%; The molar proportion of the O2 phase in the composite phase is 65%-85%, the molar proportion of the T2 phase in the composite phase is 0%-20%, and the molar proportion of the O3 phase in the composite phase is 15%-30%.

2. The cathode material according to claim 1, characterized in that, The lithium-rich manganese-based oxide with the T2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°; The lithium-rich manganese-based oxide with the O2 phase structure has characteristic peaks corresponding to the (002) crystal plane in the range of 18.2°≤θ2≤18.5°; The lithium-rich manganese-based oxide with the O3 phase structure has characteristic peaks for the (003) crystal plane in the range of 18.5°≤θ3≤18.8°.

3. The cathode material according to claim 2, characterized in that, The lithium-rich manganese-based oxide with the T2 phase structure has a characteristic peak intensity of I1 corresponding to the (002) crystal plane in the range of 17.4°≤θ1≤17.8°; The lithium-rich manganese-based oxide with the O2 phase structure has a characteristic peak intensity of I2 on the (002) crystal plane in the range of 18.2°≤θ2≤18.5°. The lithium-rich manganese-based oxide with the O3 phase structure has a characteristic peak intensity of I3 on ​​the (003) crystal plane in the range of 18.5°≤θ3≤18.8°. The I1, I2, and I3 satisfy 0 < I1 / I2 ≤ 0.5 and 0 < I3 / I2 ≤ 0.

5.

4. The cathode material according to claim 3, characterized in that, The terms I1, I2, and I3 satisfy 0 < I1 / I2 ≤ 0.2 and 0.1 ≤ I3 / I2 ≤ 0.

3.

5. The positive electrode material according to claim 3, characterized in that, The doped metal element is one or more of Ti, Zr, Mo, La and Nb.

6. The cathode material according to claim 1, characterized in that, The lithium-rich manganese-based oxide is a single crystal particle.

7. The cathode material according to claim 6, characterized in that, The particle size D50 of the lithium-rich manganese-based oxide is 1-5 μm.

8. The positive electrode material according to claim 6, characterized in that, The specific surface area of ​​the lithium-rich manganese-based oxide is 1-35 m². 2 / g.

9. A method for preparing a positive electrode material according to any one of claims 1-8, characterized in that, Includes the following steps: Sodium source, first lithium source, doped metal source and precursor are mixed and calcined in proportion to obtain a composite product containing single crystal P2 phase sodium ion oxide and O3 phase lithium ion oxide. The composite product was mixed with a second lithium source in a certain proportion and subjected to an ion exchange reaction to obtain a composite phase lithium-rich manganese-based oxide.

10. The method for preparing the cathode material according to claim 9, characterized in that, The particle size D50 of the precursor is 2-8 μm.

11. The method for preparing the cathode material according to claim 9, characterized in that, The specific surface area of ​​the precursor is 20-35 m². 2 / g.

12. The method for preparing the cathode material according to claim 9, characterized in that, The calcination is carried out at a heating rate of 1-10℃ / min.

13. The method for preparing the cathode material according to claim 9, characterized in that, The calcination temperature is 700-900℃; the calcination time is 8-24h.

14. The method for preparing the cathode material according to claim 9, characterized in that, The heating rate of the ion exchange reaction is 1-20℃ / min.

15. The method for preparing the cathode material according to claim 9, characterized in that, The ion exchange reaction is carried out at one or more temperatures within the temperature range of 250-350°C; the duration of the ion exchange reaction is 4-15 hours.

16. A positive electrode sheet, wherein the positive electrode sheet comprises the positive electrode material according to any one of claims 1-8, or the positive electrode sheet comprises the positive electrode material prepared by the preparation method according to any one of claims 9-15.

17. A battery, characterized in that, The battery comprises the positive electrode material according to any one of claims 1-8, or the battery comprises the positive electrode sheet according to claim 16.

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